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Academic research paper on topic "Abstracts, Poster Presentations"

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Combined XCT/SPECT technology in patients with hyperparathyroidism

O. Kienast (1), G. Dobrozemsky (1), K. Kaczirek (2), F. Kainberger (3), R. Dudczak (1), A. Kurtaran (1). (1) Department of Nuclear Medicine of the University of Vienna, Vienna, Austria, (2) Department of Surgery of the University of Vienna, Vienna, Austria, (3) Department of Radiology of the University of Vienna, Vienna, Austria.

Aim: 99mTc-MIBI dual phase scintigraphy is already established in localising hyperparathy-roid tissue, however, it lacks exact anatomical information. This additional information is needed if minimal invasive parathyroidectomy (MIP) is planned. For this purpose radiological imaging techniques are required. Recently, a novel transmission and emission technology in a single device has been presented and is now in clinical use. This device contains a gamma camera and a low dose X-ray tube allowing a co-registration of SPECT and X-ray CT in the same session without changing the patients position.

Materials and Methods: Nine patients with biochemical and scintigraphic evidence of hyperfunctioning parathyroid tissue were investigated with this device. Our patient population consisted of 4 patients with primary (pHPT) and 5 with renal hyperparathyroidism (rHPT). In 7 patients (4 with pHPT, 3 with rHPT) surgery has been performed, yet. In 5/7 patients MIP was applicable, in 1 patient with a four-gland-disease and one patient with an ectopic gland a transcervical approach was necessary.

Results: In all patients XCT/SPECT-technology revealed additional anatomical details providing exact localisation of SPECT-detected tracer accumulation. The most clinical benefit was achieved in 4 patients with an ectopic gland (3 with pHPT, 1 with rHPT), where the correct localisation was then confirmed by additional diagnostic (conventional) CT, ultrasound and histology. In 1 patient with rHPT the suspected accumulation in the upper mediastinum was localised in the sternum by XCT/SPECT, excluding a parathyroid adenoma. There was no difference between patients with primary or secondary hyperparathyroidism regarding usefulness of this technology.

Conclusion: We conclude that 1) in patients with hyperparathyroidism additional anatomical information provided by XCT/SPECT enhances the diagnostic accuracy of the 99mTc-MIBI images. 2) This new technology enables successful surgery, even in a minimal invasive setting. 3) Most importantly, further radiological examinations are not required in most patients with ectopic parathyroid glands.

Highly active antiretroviral treatment (HAART) with protease inhibitors (PI) in HIV: secondary effects on bone mass loss

Gr. Madeddu (1), A. Spanu (2), P. Solinas (2), G.M. Calia (1), C. Lovigu (1), M. Mannazzu (1), F. Chessa (2), M.S. Mura (1), G. Madeddu (2). (1) Department of Infectious Diseases of the University of Sassari, Sassari, Italy, (2) Department of Nuclear Medicine of the University of Sassari, Sassari, Italy.

Aim: Few and controversial data have been reported about the effect of HAART on bone mass in HIV infected patients, particularly if protease inhibitors (PI) are included, and we thus further investigated whether a relationship between bone loss risk and this type of treatment exists.

Materials and Methods: We studied 150 HIV patients, aged 22-61 yrs, 99 M and 51 F, 3 in postmenopause (m); 92 patients (P) were on HAART including PI (37.5±12.6 mths), 58 (NP) were on HAART without PI (13.3±8.7 mths). Sixty age-sex matched normal controls (C) were also enrolled. In all cases we measured in spine bone density (BD; g/cm2) by DEXA, in serum osteocalcin (O; ng/ml) and bone alkaline phosphatase (BAP; ng/ml) by IRMA and in urine pyridinium crosslinks (PYR; nM/mM creat) by ELISA.

Results: Analyzing BD values according to WHO, we found osteoporosis in 20/92 P (21%), 16 M and 4 F (1m) and osteopenia in 35/92 (38%), 27 M and 8 F; osteoporosis was also evidenced in 5/58 NP (8%), 4 M and 1 F (1 m) and osteopenia in 20/58 (34%), 13 M and 7 F. A statistical difference (p<0.05) was ascertained only for osteoporotic patients. Moreover, P patients had mean BD values (0.919 ± 0.12) significantly lower in respect of NP (0.968±0.13; p<0.04) and C (0.987±0.09; p<0.003), while no statistical difference was found between the 2 latter. P patients showed significantly (p<0.01) higher O values (21.21±10.9) compared to NP (17.04±6.47), while neither patient group showed any statistical difference with C (19.49±7.0). P and NP patient BAP levels (18.35±9.46 vs 18.30±9.05) were not significantly different, but both were significantly (p<0.01) higher than C (13.74±7.62). PYR (nM/mM creat.) was significantly (p<0.04) higher in P (28.7±13) than NP (24.8 ± 11) patients; moreover, P and NP had significantly (p<0.000008 and p<0.006, respectively) higher values than C (18.4±6.57). In Ppatients no significant correlation was found between BD, O, BAP, PYR and disease severity or treatment time.

Conclusion: Thus bone mass loss risk seems to exist in HIV HAART PI treated patients with higher incidence and significantly more severity than patients not treated with PI. Since bone disorder can exarcebate HIV disease associated morbidity, an accurate selection of patients for preventive therapy prior to PI treatment and a careful follow-up seem advisable.

Bone mineral loss in celiac patients on gluten free diet (GFD). A longitudinal study

F. Dore (1), G. Fanciulli (2), P. Solinas (1), M. Cossu (2), F. Chessa (1), A. Falchi (1), G. Madeddu (1). (1) Department of Nuclear Medicine of the University of Sassari, Sassari, Italy, (2) Department of Pediatry of the Hospital of Alghero, Sassari, Italy.

Aim: We further investigated whether a bone mass loss exists in celiac patients and whether gluten free diet (GFD) might improve this disease complication.

Materials and Methods: We studied 71 affected patients, 45 adults (38F, 7M) aged 22 to 66 yrs (G1) and 26 young people (17F, 9M) aged 10 to 19 yrs (G2); 7 G1 females were in post-menopause (m). All G1 and G2 patients were on GFD (34.33±62.30 and 51.03±48.97 mths, respectively). We also enrolled 102 age and sex matched normal subjects (C), 55 adults (C1), and 47 young people (C2). In all patients and in C we measured in spine BD (g/cm2) by DEXA, in serum Osteocalcin (O; ng/ml), Bone Alkaline phosphatase (BAP; ng/ml), PTH (pg/ml) by IRMA, Calcium by standard colorimetry and in urine Pyridinium cross-links (PYR; nM/ mM Creat.) by ELISA.

Results: According to WHO, we found osteoporosis in 7/45 G1 (15.5%), all females (4m), and osteopenia in 18/45 (40%), 4 M and 14 F (2m); osteoporosis was also evidenced in 3/26 G2 (11.5%), 1 M and 2 F, and osteopenia in 12/26 (46.1%), 4 M and 8 F. BD mean values were significantly lower in celiac patients than in C, both in G1 (0.910±0.14 vs 0.99±0.10; p<0.002) and in G2 (0.760±0.17 vs 0.880±0.13; p<0.001).

O, BAP and PYR mean levels were higher in G1 and G2 patients than C, but the difference was significant in G1 only for PYR (p<0.00001) and PTH (p<0.01) and in G2 only for BAP (p <0.02). Calcium was significantly lower in celiac patients than in C. Neither BD nor the other parameters correlated with GFD treatment time. We rechecked after 18 mths 35/45 G1 and 12/26 G2 patients, still on GFD. BD had significantly increased both in G1 (0.92±0.15 vs 0.91±0.15, p<0.03) and in G2 (0.84±0.14 vs 0.81±0.15, p<0.002). In G1, only O and BAP significantly (p<0.04) decreased, while in G2 only BAP (p<0.008). PTH decreased in both G1 and G2, significantly (p<0.04) in G1, while Calcium remained immodified. Conclusion: Our data confirm that osteoporosis and osteopenia can occur in both adult and younger celiac patients, even on GFD, but particularly in the former, with menopause an aggravating factor. Bone mass disorder, due to calcium malabsorption causing secondary serum PTH increase, can be improved by continuous GFD, as our longitudinal study seems to demonstrate.

Comparison of Lateral Versus Anterior-posterior Spine DXA in Obese-postmenopausal Women

G. Bural (1), B. Karayalgin (1), O. Qeri (1), F. Aydin (1), A. Yildiz (1), U. Karayalgin (2). (1) Department of Nuclear Medicine, Medical Faculty of Akdeniz University, (2) Division of Endocrinology, Medical Faculty of Akdeniz University, Antalya, Turkey.

Aim: Bone mineral density (BMD) measurement using dual energy X-ray absorptiometry (DXA) may result in falsely elevated values due to degenerative changes in posterior vertebral elements. Lateral spine DXA which selectively measures the trabecular -rich vertebral bodies is less affected by degenerative changes than PA-DXA. Although lateral scan has been suggested as a solution of this situation, in obese patients due to increased attenuation of fat tissue, BMD measurements may also increase.

In our study, we investigated the correlation of Z scores and BMD values obtained by pos-teroanterior (PA)L3 and lateral LAT-L3 DXA scans in obese postmenopausal women. Materials and Methods: 49 postmenopausal obese women (Body Mass Index (BMI) 34.3±4.2 kg/m2; age 59.6±7.9 years) were included to our study. The correlation between PA-L3 and LAT-L3 Z scores and BMD values were evaluated and PA-L3 and LAT-L3 Z scores were compared.

Results: The correlation between PA-L3 and LAT-L3 Z scores and BMD values were significantly low: 0.38±1.18; 0.35 ±1.64 (r=0.47 p<0.05); 0.989±0.157 and 0.600±0.143 (r= 0,34 p<0.05) respectively. Even though there is no significant difference between PA-L3 and LAT-L3 Z scores (p>0.05), there was no significant correlation..

Conclusion: In lateral scans fat attenuation; in PA scans degenerative changes may lead to falsely elevated Z scores. Although lateral scan is more valuable in non-obese patients with degenerative changes; in obese patients with degenerative changes both PA and LAT-L3 values may result in falsely elevated values. Therefore, in the assesment and follow-up of obese patients with degenerative changes, femur neck values or whole femur region values may be more reliable.

Acute Alterations in Bone Metabolism Markers in Patients with GRAVES Opthalmopathy, after receiving one high dose of Glucocorticoids I.V.

G.K. Kachrimani, I.A. Armeniakos, A.P. Pilava, E.V. Veve, T.S. Stratigou, E.P. Papadodima, X.S. Soulou, C.A. Avgoustis, S.P. Papadopoulos. Dpt. of Endocrinology and Metabolism, Athens, Greece

It is widely known that glucocorticosteroids(GCs) administrated per os as a long term treatement, reduce bone formation and induce bone resorption, disconnecting the two phases of bone metabolism.

The aim of the study is to estimate the variation in bone metabolism markers, after IV administration of Igr methylprednizolone(mtp).

Patients and methods: 19 patients with Graves'ophthalmopathy aged 22-55 years old, were studied.5 had subclinical hyperthyroidism^ hyperthyroidism^ euthyroidism,2 hypothyroidism. We measured Ca, P, ALP, osteocalcin(BGP), PTH before and 24 hours after IV administration of 1 gr mtp RESULTS:

BEFORE AFTER

BGP (ng/ml) 23,03 ±12,69 9,48± 7,8*

PTH (pg/ml) 35,36± 16,8 31±11,34#

Ca (mg/dl) 9,76 ±0,56 10,07±0,51**

P (mg/dl) 3,49 ±0,42 3,57 ±0,7 #

ALP (U/L) 90 ±44 88± 46 #

Values as x ±SD *p<0,001 **p<0,l #NS

CONCLUSIONS: GCs given IV in one high dose, rapidly decreased osteoblast activity as shown by significant reduction of BGP

On the other hand, no significant increase of PTH was noted. The unexpected increase of serum Ca should be re-evaluated in a larger group of patients.

Conclusions: Somatostatin receptor scintigraphy shows high specify in the diagnostic of pituitary tumours. Somatostatin receptor scintigraphy presents high sensitivity in the diagnostic of GH and PRL secreting pituitary adenomas. Moreover is a non-invasive study that allows to obtain additional relevant information for diagnostic and treatment of pituitary tumours. Somatostatin receptor scintigraphy may help to better characterisation of pituitary tumour with confounding results on CT or MRI.

Somatostatin receptor scintigraphy in preoperatory diagnostic of patients with pituitary tumours.

M.A. Muros (1), M.J. Acosta-Gómez (1), J.M. Llamas-Elvira (1), A. Ramírez (1), J.M. López-Ruiz (1), G. Sabatel (1), S. Ortega (1), R. Vilchez (2). (1) Department of Nuclear Medicine of the Universitary Hospital, Granada, Spain.

In vivo visualization of somatostatin receptor is acquiring great importance in the diagnostic of Neuroendocrine tumours. In pituitary tumours there are different results in the literature about the utility of somatostatin receptor scintigraphy.

Objective: Determine the utility of somatostatin receptor scintigraphy in the diagnostic of patients with pituitary tumours.

Material and methods: We evaluated 17 patients (12 female and 5 male) (mean age 42,5 years) diagnosed of pituitary tumours (Acromegaly GH n=4; Prolactinoma PRL n=4; non secretor n=3; ACTH n=3; TSH n=1; FSH n=1; LH n=1) Clinical data, biochemical analysis, conventional images: Computer Tomography (CT) and MRI, ophthalmologic study (campimetry) and evaluative control were obtained in all patients. Scintigraphy with 111In-DTPA-D-Phe-octreotide was performed with 185-220 MBq (5-6mCi). Health Department approved the compassionate use of the radiopharmaceutical in all patients. Planar views were obtained at 4, 24 and 48 hours after injection and SPECT was obtained at 4 and 24 hours. Qualitative evaluation of the images was made by two specialists in Nuclear Medicine to describe tracer uptake. Anatomopathology was used as confirmation in patients operated (n=3), and in those were surgery was not consider conventional images (CT or MRI) with hormonal analysis and evaluative control during 6 months to 2 years was used. Results: Somatostatin receptor scintigraphy was positive in 10 patients. MRI was positive in these 10 patients. In two patients surgery confirmed pituitary tumour, six patients were treated with somatostatin analogue and two patients with substitutive medical treatment (those with small lesions) In all 10 patients evaluative control demonstrated improvement. Scintigraphy was negative in 7 patients: absence of tumour was demonstrated in 3 patients using conventional images, biochemical analysis and evaluative control. In the other four patients somato-statin receptor scintigraphy do not detected presence of tumour: two non-secreting adenoma, ACTH secreting adenoma less than 1 cm of size and an eventual Prolactinoma. Our results show the highest sensibility of somatostatin receptor scintigraphy in GH and PRL secreting adenoma (S=80%) and less sensibility in patients with non-secreting tumours were the presence of somatostatin receptor is less. Comparing the results with MRI, MRI was positive in a patient were it was not confirmed the presence of adenoma in biochemical analysis neither evaluative control. Somatostatin receptor scintigraphy shows a global sensibility of 71%, Specificity 100%, and Positive Predictive Value (PPV) of 100%.

Combined XCT/SPECT in a single device in patients with suspected or known pheochromocytoma

S. Ozer (1), O. Kienast (1), G. Dobrozemsky (1), B. Niederle (2), F. Kainberger (3), R. Dudczak (1), A. Kurtaran (1). (1) Department of Nuclear Medicine of the University of Vienna, Vienna, Austria, (2) Department of Surgery of the University of Vienna, Vienna, Austria, (3) Department of Radiology of the University of Vienna, Vienna, Austria.

Aim: The aim of this work was to evaluate the clinical/diagnostic value of combined XCT/SPECT in a single device in patients undergoing 123I-MIBG scintigraphy. This technology permits the co-registration of both nuclear medicine and radiological studies in the same patient position.

Material and Methods: 21 patients with known (n=4) or suspected pheochromocytoma (n=17) demonstrating focal accumulation(s) in 123-I MIBG scintigraphy were investigated with the novel gamma camera mounted anatomical X-ray tomograph (GMAXT; GE Medical systems, Millenium VG with Hawkeye) which is equipped with a low dose CT. Results: The morphological information obtained by this technology provided better anatomical information allowing the differentiation of physiological intestinal uptake/renal excretion from abnormal 123I-MIBG-uptake (adrenal/extraadrenal). Fused images demonstrated intestinal accumulation of 123I-MIBG in 6 out of 17 patients (35 %) who had focal uptake in the abdomen. In 7 out of 17 patients (41%) the focal accumulation was shown to be caused by the renal excretion of 123I-MIBG excluding a pheochromocytoma. In two patients a focal accumulation in projection of the right adrenal gland was caused by an unusual accumulation of 123I-MIBG in the liver. In the remaining two patients focal accumulation was localised in the adrenal glands leading to successful surgery. In one patient with known pheochromocytoma the differentiation of bone metastasis from a local recurrence could be accurately done by this system resulting in a change of patient management.

Conclusion: Our study demonstrates the potential clinical value of XCT/SPECT in a single device in patients undergoing 123I-MIBG scintigraphy. The combined XCT/SPECT technology provides a higher diagnostic accuracy and may avoid further diagnostic procedures.

Ligand of Glucose Transporters: preliminary biological evaluation of iodine flavonoïd derivatives.

H. Visseaux (1), M.D. Desruet (1), C. Ghezzi (1), A. Boumendjel (2), A.M. Mariotte (2), D. Fagret (1). (1) Inserm E00-08,Laboratoire d'Etudes de Radiopharmaceutiques ,Faculté de médecine ,Grenoble (FRANCE), (2) Laboratoire de Pharmacognosie-UFR de pharmacie de Grenoble,Université Josehp Fourier,La Tronche, France.

Aim: Glucose transporters are a family of membrane proteins which mediate glucose uptake across the cell membrane and play a major role in glucose homeostasis. Alterations of GluT membrane distribution have been involved in the pathogenesis of altered metabolic state such as diabetes, neurodegenerative disorders and tumors. Moreover, it has been shown that GluT density alteration in insulin resistance is a characteristic of precocious state of Type 2 diabetes mellitus. As part of a developpement of SPECT radioligands for in vivo quantitative measurement of Glucose transporters, this study proposes the evaluation of several iodine flavonoïd derivatives.

Materiel and Methods: To test the interaction of these iodine flavonoïd derivatives with GluT 1 (Glucose transporters on erythrocytes) in vitro, inhibition (determination of Ki) and competition experiments were conducted in human erythrocytes. These Ki were determined with glucose transport tracers as D-galactose[14C] or 2-Deoxyglucose [14C]. Results: Five iodine flavonoïd derivatives called AB1, AB2, 4IMEM,MH-48, 4IC have given promising results. AB1, AB2, 4IMEM and MH-48 were found to have a Ki of 90+-4, 40.5+-9, 232+-89, 95+-25 micromolars respectively Whereas no inhibition of Glucose transport was evidenced with 4IC .

Conclusion: The best affinity for GluT1 was found with AB2. This affinity is one hundred fold better than that of Glucose. Further Studies are now in progress testing other iodine flavonoïd derivatives. The most promising of these compounds will be radiolabeled and evaluated in vivo. A SPECT radiotracer of GluT will be very interesting for evaluated glucose transporters density alteration in insulin resistance which is a characteristic of precocious state of Type 2 Diabetes.

Pharmacokinetics of levothyroxine: is it linear or not?

M.J. Reinhardt (1), H.P. Breuel (1), H. Palmedo (1), U. Mansmann (2), D. von Mallek (1), H.J. Biersack (1). (1) Department of Nuclear Medicine, University Hospital Bonn, Bonn, Germany, (2) Institute for Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany.

Aim: Thyroid hormone substitution with levothyroxine is the standard treatment of hypothy-roidism. Nonetheless, it is still unclear, whether levothyroxine has a linear or almost linear pharmacokinetics or not. Thus, the aim of this study was to assess the pharmacokinetic linearity of levothyroxine.

Materials and Methods: Pharmacokinetic data obtained from 205 patients treated with 8 different doses of levothyroxine ranging from 25 ^g to 200 ^g were normalized to a standard dose of 100 ^g. All studies were performed according to the same crossover design with two treatment periods of 6 weeks and a treatment-free interval of 2 weeks. Thus, a total of 410 data-sets were obtained. Study participants were symptomatic subjects in whom levothyrox-ine treatment was indicated in the particular dose of the respective bioequivalence study. Serum concentrations of total and free levothyroxine were analyzed at the end of both treatment periods. The dose-normalized pharmacokinetic parameters AUC0^24' Cmax and Ctrough were tested for differences by a one-way ANOVA and post hoc tests. Results: Steady state was reached for each dose after 6 weeks of medication, as demonstrated by comparing total and free levothyroxine serum concentrations before intake of medication and 24 hours later. The pooled dose-normalized pharmacokinetic parameters AUC0^24' Cmax and Ctrough of free and total levothyroxine showed a close correlation between both treatment periods (Pearson's correlation coefficient r between 0.879 and 0.925). Variation coefficient did not show a significant difference in dependence on the dose of levothyroxine. No relevant dose range could be identified in which the pharmacokinetics of levothyroxine were "almost" linear, defined as a 20 % or smaller deviation from the 100 ^g reference dose. Conclusion: Levothyroxine has a non-linear pharmacokinetics.

Date: 02.09.2002 THYROID

Time: 14:30 - 16:00 • Hall: Poster exhibition

Intra-individual Variability of Thyroid Hormones in Healthy Volunteers without Hormone Substitution.

T. Krause (1), N.S. Simon-Hodler (2), H.P. Breuel (2), H. Palmedo (2), D.V. Mallek (2), H.J. Biersack (2), M.J. Reinhardt (2). (1) Department of Nuclear Medicine of the Inselspital, Berne; Switzerland, (2) Department of Nuclear Medicine of the Universitaetsklinik Bonn, Bonn, Germany.

There are only few data available concerning spontaneous variation of thyroid hormones in healthy subjects.

The aim of the study was the evaluation of spontaneous variability of thyroid hormones in healthy people without hormone substitution within one week.

Methods: Included in the study were 20 healthy volunteers (12 female, 8 male, age 32 ± 11 years) with total T3 and T4, free T3 and T4 in normal range, and basal TSH > 0.5 mU/L, body weight in normal range, and without any concomitant medical therapy. Blood samples were drawn at 8.00 am and 10.00 am on day 1, 2, 3, and 7 after 30 min lying period. Mean thyroid hormone levels were determined with AMERLEX-M T4, AMERLEX-MAB FT3 (Ortho-Clinical Diagnostics, Amersham, UK), and GammaCoat T3, GammaCoat Free T4 (DiaSorin, Stillwater, Minnesota, USA).

Results: Confirmatory comparison showed no significant differences of T4, fT4, T3, and fT3 values between days 1 to 7. Pearson's coefficient of correlation was high for T4 (> 0.88), fT4 (> 0.87) and for T3 (> 0.80) regarding individual variability between day 1 to 7 for the two blood samples (8.00 am and 10.00 am). For fT3 correlation was sometimes weak (range 0.850.16). Rcrit-values were low for T4 (< 1.17), slightly higher for T3 (<1.31), fT3 (1.27), and fT4 (<1.64). Mean individual coefficients of variation of the precision (max CV - min CV) were: T4 (11.94-2.82), fT4 (19.53-4.43), T3 (12.17-3.39), and fT3 (14.24-2.91). Conclusions: Spontaneous variation of levels for T3, fT3, T4, and fT4 is minimal. There was no significant difference found between days 1 - 7. Rcrit (p=0.05) and coefficients of variation were found to be small for T4, T3, and fT3. The greatest variability was determined for fT4.

Cerebral Blood Flow In Hypothyroidism: Response To Therapy And Associated Cognitive Performance

N. Ilgin (1), I. Yetkin (2), U.O. Akdemir (1), A. Eroglu (2). (1) Gazi University Medical School Department of Nuclear Medicine, Ankara, Turkey, (2) Gazi University Medical School Department of Endocrinology, Ankara, Turkey.

Hypothyroidism is often associated with defective memory, psychomotor slowing and depression. However, the relationship between thyroid status, related cognitive state and associated cerebral circulatory and/or metabolic abnormalities have not been elucidated. Purpose: The aim of this study was to evaluate pre-and post-therapy brain perfusion patterns in 9 hypothyroid patients presenting with Hashimoto thyroiditis

Method: Patients were referred on the basis of abnormal levels of anti-thyroglobulin and anti-microsomal antibodies, hypothyroidism and symptoms of cognitive dysfunction. Cognitive performance was tested using Raven's Coloured Progressive Matrices and Bender Gestalt Test. Functional evaluation of the brain was also performed via the methods of electoroen-cephalograpy (EEG) and single photon emission tomography (SPECT). An initial SPECT study was carried out after I.V. injection of Tc99m-HMPAO and semiquantitative rCBF analysis was performed by drawing irregular regions of interest (ROIs) in three slices. A total number of 12 sector regions of interest placed on the two hemispheres and regional cerebral blood flow (rCBF) was determined using cortical region/cerebellum ratios obtained in each hemisphere. A repeat SPECT study was undertaken in 5 subjects 3-6 months after the initiation of medical therapy.

Results: Pre-therapy perfusion data in four patients showed that the cortical ratios were globally depressed at the levels of 0.65-0.85 where these ratios improved quickly to the near normal-above normal levels (range of rCBF improvement as % difference from baseline 25%-45%) within 3-4 months of therapy.

Conclusion: These results indicate that brain activity was globally decreased in severe hypothyroidism of short duration which normalized steadily as the hypothyroid state is corrected.

Usefulness of 2-hour uptake for calculating the dose of I-131 in the treatment of Graves^ disease

I. Al-Shammeri (1), S. Mahmood (1), N. Ballani (2), S. Al-Mohannadi (1). (1) Department of nuclear medicine, Kuwait center for specialized surgery, Ministry of Health, Kuwait, (2) Radiologic Sciences, Kuwait University, Kuwait.

Aim: To emphasise 2-4 hour uptake usefulness in calculating the therapy dose of I-131 as other factors like previous neomercazole intake, weight of the gland, recurrence of thyrotoxicosis.

Literature has emphasised calculating the 2-4 hour uptake (i.e. early measurement) of I-131 in patients with Graves' disease to detect the high washout or rapid turnover patients. Material and Methods: We have noticed that patients with rapid turnover are liable for under dosage when calculating the dose if such factor is not taken into consideration. At our centre we do a 2 hour uptake for all patients of hyperthyroidism. A retrospective study was conducted, reviewing the medical files of 1417 patients who received radioactive iodine for Graves' in the period from 1992 to 2000.

Results: The hundred-four (104) patients were found to have high 2-hour value (normal value up to 45%). Sixty-four (61%) patients needed more frequent and close follow up (up to three years), hypothyroidism was not achieved 3-4 months post-treatment as expected. Twenty-nine patients (28%) needed a second dose. Three patients received a third dose. Conclusion: The two-hour uptake value of I-131 in Graves' patients should be taken into consideration when calculating the dose. Our advice that such patients should have higher dose than patients with normal 2-4 hour uptake; however, further investigation is required before deciding on the fixed high dosage regimen.

Efficiency of radioiodine therapy in Graves disease and adenoma toxicum and incidence of hypothyroidism

Z.P. Petrovski, G.J. Jovan, M.S. Snezana. Department of Nuclear Medicine,Medical Center,Bitola,Macedonia.

The aim of the this study was to evaluate different states in hyperthyroid patients and incidence of hypothyroidism after J-131 therapy.We observed a total of 184 hyperthyroid pts,fTom which 108(58,7%)pts with Graves' disease,65(35,3%)pts with single toxicum nodule and 11(6%)pts with toxicum multinodular goitre,treated with radioiodine therapy during the period 1986-2001.Dose of J-131 orally administered ranged 150-1100MBq and was calculated according to the "MBq/gram" method.The radioiodine-131 therapy was perfomed once in 69,5%(128/184)pts,twice in 21,2%(39/184)pts and in 9,3%(17/184)pts more than two doses. Completely cured of hyperthyroidism occurred in 61%(66/108)pts with Graves' dis-ease,81,8%(9/11)pts with toxic multinodular goiter and 90,7%(59/65)pts with single toxic nodule.The patients in our study were evaluated 6 months to 15 years after received J-131 therapy.

Incidence of early hypothyroidism within one year was 23,1%(25/108) in Graves' dis-ease,9%(1/11) in toxic multinodular goiter and 4,6%(3/65) with single toxicum nodule.Overall incidence of hypothyroidism within one year was 17,6% and had cumulative increase of Graves' disease every following year approximately for 3%,while for adenoma toxicum there was no any significant changes.

We concluded that radioiodine therapy is simple,comfortable radical method for medical treatment of hyperthyroidism and indicate higher incidence of hypothyroidism in patients treated with J-131 for Graves' disease than that of patients treated for toxicum multinodular goiters and single toxic nodule.

Is there an useful correlation between Tc-99m and I-131 uptake in Hyperthyroidism?

S. Carmona (1), P. Almeida (1,3), P. Santos (3), J. Sequeira (1), M. Filipe (1), D. Passos (2), R. Magalhaes (1), A.I. Santos (1). (1) Nuclear Medicine Department, Hospital Garcia de Orta, Almada, Portugal, (2) Endocrinology Department, Hospital Garcia de Orta, Almada, Portugal, (3) Biophysics and Biomedical Engineering Institute, University of Lisbon, Portugal.

Introduction: The therapeutic doses of I-131 used in hyperthyroidism can be calculated using thyroid uptake measures obtained from planar I-131 images. The replacement of I-131 by Tc-99m for this purpose, would reduce radiation doses during thyroid uptake measurements, improve image quality for accurate imaging of the functional areas of thyroid and reduce the time and cost of the procedures. However, a relationship between the physiological uptakes of I-131 (UI) and of Tc-99m (UTC) needs to be established.

Aim: This study investigates the functional relationship between maximum I-131 and Tc-99m thyroid uptakes in hyperthyroid patients, which is expected to occur in average at 24 h and 2030 minutes post administration for I-131 and Tc-99m, respectively.

Material and Methods: We have studied 45 patients, 35 female and 10 male (<age>= 52.3±12.4 y) classified into three groups, according to the hyperthyroidism ethiology: 19 Multinodular Goiter (MG), 17 Diffuse Goiter (DG) and 9 Toxic Adenoma (TA). Patients were injected with 74.00±11.10 MBq of Tc-99m and thyroid and background planar images were obtained 25±6 minutes after injection. I-131 capsules (0.89±0.15 MBq) were given to patients 83±24 minutes after Tc-99m injection and thyroid and background planar images obtained about 22 hours after the administration. All images were obtained using a 128*128 pixel (1.57x1.57 mm) matrix on a single headed gamma camera (GE400XC) equipped with a Low Energy High Resolution and a High Energy All Purpose collimator for Tc-99m and I-131, respectively. Thyroid uptake were calculated for both radioisotopes as ((T-B)/AD)x100(%), where T represents thyroid counts, B the background counts and AD the counts obtained for the pellet and injection syringe in I-131 and Tc-99m, respectively. The same operator in all cases manually drew the regions of interest used for analysis.

Results: The functional relation between UTC and UI showed an exponential trend in the separate cases of DG (UTC=0.81e0 04(UI), R2=0,69) and MG (UTC=0.32e0 06(UI), R2=0,69). Grouping DG and MG patients resulted in a trend defined as UTC=0.44e005(UI), R2=0,71. Poor correlation was found in the case of patients with TA, probably due to the small size of this group. For the entire group of patients studied UTC=0.52e0.05(UI), R2=0,65. Conclusion: The results obtained suggest that there may be an useful relationship between I-131 and Tc-99m uptake in patients suffering from Diffuse or Multinodular Goiter. Additional data is necessary to confirm this correlation, before allowing the exclusive use of Tc-99m for thyroid uptake calculations in hyperthyroidism therapy procedures using I-131.

In111-Octreotide scintigraphy in orbital Graves' disease: a parameter to predicts the clinical response to somatostatin analogs therapy?

M.L. Domínguez (1), B. Llana (1), N. Zeidán (1), J.P. Suárez (1), A. Alvarez (1), P. Raigoso (1), C. Roiz (1), T. Allende (1), F. Cadórniga (2). (1) Department of Nuclear Medicine of the Hospital Central de Asturias, Oviedo, Spain, (2) Department of Endocrinology of the Hospital Central de Asturias, Oviedo, Spain.

OBJECTIVE: The aim of the study was to evaluate the degree of orbital In111-Octreotide uptake in Graves' ophthalmopathy and the management of the scintigraphy to predict the response to somatostatin analogs therapy in these patients.

METHODS: We studied 9 patients (8 women and 1 man), mean 46 years, with moderately severe Graves' ophthalmopathy. The severity of the ophthalmopathy was assessed according to NOSPECS classification and all patients included presented at least class 3 of orbital disease severity. In all cases, previously to scintigraphy, it was practiced CT in order to asses the evidence of enlargement of extraocular muscles and to exclude other causes of ophthalmopathy. The orbital uptake of In111-Octreotide was measured at 4 and 24h after i.v injection of 330 MBq In111-DTPA-Octreotide, the scintigraphy was performed with a ELSCINT double head SPECT-camera. A semi-quantitative four-point score (ranging from 0 to 3) was used to classify the intensity of uptake and scores were assigned to two categories: negative scores 0 and 1 (no uptake or same uptake as skull background); positive scores 2 and 3 (more intense uptake). A quantitative analysis was also carried out using a fixed rectangular region of interest in transversal slices of the orbit and in an occipital area. To correct orbital uptake for nonspecific background uptake, we calculated the orbital/occipital uptake ratio. Somatostatin analogs therapy was decided for each patient according to sings and symptoms and scintigra-phy data.

RESULTS: In all cases orbital uptake was more intense in 4h study than 24h exploration. In 4 patients early tomography images were interpreted score 2 or 3 on semi-quantitative analysis. The orbital/occipital uptake ratio varied from 1.2 to 2 at 4h study and all those cases that were visually classified score 2 or 3 showed an uptake ratio higher than 1.5. Three patients with positive scintigrahy and 1 patient with negative study (previously treated with corticosteroid and without improved of ophthalmopathy) were treated with Lanreotido or Sandostatin. Ophthalmological changes were recorded during 6 months and we found no worsening of ophthalmopathy in all cases.

CONCLUSIONS: In111-Octeotride scintighraphy showed higher orbital uptake in early studies than 24h images. The orbital uptake may be considered as indicator of active disease and this current preliminary study suggested that In111-Octroetide scintigraphy may be an useful approach to select patients to proper treatment. This preliminary data suggested that scintigraphy is able to predict the clinical response to somatostatin analogs therapy.

The Role Of Tc-99m Polyclonal Human Immunglobulin Scintigraphy in Graves' Ophthalmopathy

H. Ortapamuk (1), S. Naldoken (1), B. Hosal (2). (1) Department of Nuclear Medicine of Ankara Numune Hospital,Ankara,TURKEY, (2) Department of Ophthalmology, Ankara,TURKEY.

Objective:Recently, Tc-99m human immunglobulin G (HIG) was introduced for clinical use. This radioligand is used for infection and inflammation. The aim of this study was to clarify whether Tc-99m HIG can be imaged and determinated the severity of orbital involvement in patients with Graves' ophthalmopathy.

Method: 26 patients between 19 and 36 years with Graves' ophthalmopathy were examined. All patients received approximately 370 MBq Tc-99m HIG by iv. injection. Planar and SPECT examination were performed 4 hours after injection. Visual and semiquantitative evaluations were performed for both orbits by two independent observers.

Results: Clinically activite ophthalmopathy patients (n=7 ) showed markedly increased orbital accumulation of labeled Tc-99m HIG. In patients with inactive disease ,14 of 19 had no uptake whereas 5 patients showed orbital radioactivity accumulation. There was a good correlation between clinical activity and radioactivity grade with r = 0.844 (P= 0.001). Conclusion:These results indicate that Tc-99m HIG SPECT might be useful for assessment of disease activity in Graves' ophthalmopathy.

Induction of TSH-Receptor Antibodies in Patients with Toxic Multinodular Goitre by Radioiodine Treatment.

D.M. Muller (1), H. Wallaschofski (2), R. Paschke (2), O. Sabri (1). (1) Department of Nuclear Medicine Leipzig, (2) Department of Internal Medicine III Leipzig, Germany.

Aim: Previous studies have shown an increase or a de-novo induction of TSH-receptor antibodies (TRAbs) in some patients with toxic multinodular goitre (TMG) after radioiodine treatment (RAI). We investigated whether the induction of TRAbs preferentially occurs in patients with TMG type A (i.e., predominantly disseminated autonomy) and whether TRAbs are detectable in these patients by two different newest generation TRAb assays before RAI. Material and methods: TRAbs levels were measured by a conventional assay (TBII, Dynotest® BRAHMS Inc., GER) and an TSAB Assay. The later assay facilitates to distinguish between stimulating and inhibiting Abs (Wallaschofski et al., 2001). In addition anti-thyroper-oxidase antibody (anti-TPO-Abs) and anti-thyroglobulin antibody (anti-TG-Abs) levels were determined. Forty-three consecutive patients with the scintigraphic diagnosis of a toxic adenoma (TA; n = 20), TMG type A(n = 11) or type B (n = 12) and with no detectable TRAbs by either assay before RAI were prospectively enrolled.

Results: After RAI therapy, we detected TRAbs by means of the TBII assay exclusively in patients with TMG type A in 4 of 11 cases (36%), whereas TRAbs were not detectable in patients with TMG type B or TA. Furthermore, 3 of the 4 patients with detectable TRAbs after RAI showed positive anti-TPO-Abs before RAI. No TRAbs we detected by means of the

TSAB assay.

Conclusions: These preliminary results show that patients with TMG type A and high anti-TPO-Abs seem to be at risk of developing TRAbs after RAI. Further, the TSAB assay seems to be not sensitive enough to identify patients with a subclinical Graves disease before RAI. References: Wallaschofski H, Orda C, Fuhrer D, et al.: Distinction between autoimmune and nonautoimmune hyperthyroidism by determination of thyrotropin-receptor antibodies in patients with the scintigraphic diagnosis of disseminated autonomy. Thyroid. 2001 Jul;11(7):710-1.

The influence of 131I-radioiodine therapy on anti-TSH antibody level measured with TRAK-HUMAN kit

W. Cholewinski, A. Nocun, B. Stefaniak, B. Szymanek, H. Jankowska, A. Tarkowska. Department of Nuclear Medicine, Medical University of Lublin, Lublin, Poland.

Aim. To assess the influence of radioiodine therapy on anti-TSH antibodies level measured with TRAK HUMAN kit (Brahms) in patients with Graves (GD) hyperthyreosis Material and Methods. 87 patients with hyperthyreosis in GD underwent blood tests comprising the levels of anti-TSH antibodies measured with TRAK HUMAN kit (Brahms) (aTSHh), TRAK ASSAY kit (Brahms)(aTSHp) and levels of antiperoxidase antibodies (aTPO) (Brahms), FT3, FT4, TSH. The studies were performed before and on the average 6.6 months after 131I therapy. In ten pts blood tests were repeated on the average 14.5 months after treatment.

Results. Before therapy increased levels of aTSHh were observed in 93.1% of pts, aTSHp in 79.3% and aTPO in 78.2%. In 17 pts who became euthyreotic after 6.6 months, the mean concentrations before and after therapy and the differences were respectively: aTSHh 7.9 IU/l and

12.8 IU/l (+62.0%, p>0.05); aTSHp 38.7 IU/l and 59.6 IU/l (+54.0%,p>0.05); aTPO 1437.7 and 1779.3 U/ml (+23.8%, p>0.05). In 36 pts with post treatment hypothyreosis (Hy) above concentrations were respectively: aTSHh 14.1 IU/l and 20.1 IU/l (+42.6%, p<0.05); aTSHp

73.9 IU/l and 113.2 IU/l (+53.2%,p>0.05); aTPO 1612.0 and 1920.3 U/ml (+19.1%, p>0.05). In 34 pts with hyperthyreosis (Hr) after treatment those concentrations were respectively: aTSHh 17.3 IU/l and 32.3 IU/l (+34.7%, p<0.01); aTSHp 80.1 IU/l and 95.1 IU/l (+18.7%, p>0.05); aTPO 1797.4 and 2132.2 U/ml (+18.6%, p<0.05). Number of subjects with elevated levels of aTSHh, aTSHp and aTPO were higher in groups Hy and Hr 6.6 months after therapy than before treatment (respectively: Hy- aTSHh 100% vs 94.4% and Hr- 100.0% vs. 97.1%; aTSHp 94.1% vs 83.3% and 94.1% vs 85.3%; aTPO 86.1% vs 78.8% and 91.2% vs 88.2%). In the group, which developed euthyreosis, numbers of pts with elevated aTSHh and aTSHp levels were similar before and after treatment (82.4% vs 82.4% and 58.8% vs. 58.8%). Number of pts with elevated aTPO was slightly higher after than before therapy (64.7% vs 58.8%). Studies performed in 10 patients, 14.5 months after treatment, revealed mean concentrations of all measured antibodies lower than before therapy (respectively: aTSHh 6.5 IU/l vs 15.5 IU/l (-62.9%, p>0.05), aTSHp 13.1 IU/l vs 113.5 IU/l (-88.5%, p>0.05), aTPO 1331.7 U/ml vs 2195.7 U/ml (-39.4%, p>0.05).

Conclusions. The measurements with TRAK HUMAN kit reflect better the immunological condition in GD than TRAK ASSAYkit, independently of thyroid function.

Computer-Assisted Image Analysis in Differential Diagnosis of Hyperplastic and Neoplastic Follicular Nodules of the Thyroid

H. Halbauer, M. Medvedec, H. Tomic Brzac, D. Dodig. Department of Nuclear Medicine and Radiation Protection of the University Hospital Centre Zagreb, Zagreb, Croatia.

Aim: In order to assess the possible value of morphometric parameters in distinguishing between nodular hyperplastic goiter (NHG) and neoplastic follicular nodules in the thyroid, fine needle aspirates were morphometrically analyzed under an Olympus BH2 microscope, using a PC based image analysis system (VAMS, Zagreb) and CCD camera (JVC TK 1270). Material and methods: The nuclear area and perimeter were measured in at least 100 nuclei per smear in aspirates of 10 pathohistologically confirmed NHG, 10 follicular adenomas (FA) and 10 follicular carcinomas (FC). Form factor, equivalent radius and volume were calculated from the measured values.

Results:

NHG (N=10)

FA(N=10)

FC (N=10)

Area (?m2) 73.8+/-24.3 83.9+/-12.6 102.0+/-26.8

Perimeter (?m) 33.7+/-5.4 36.1+/-2.8 39.4+/-5.1

Form factor 0.796+/-0.024 0.802+/-0.023 0.810+/-0.018

Radius (?m) 4.8+/-0.8 5.1+/-0.4 5.6+/-0.7

Volume (?m3) 499.9+/-251.2 590.4+/-131.5 809.0+/-333.9

Nuclear area and volume appeared as the most important factors of differentiation. The result of one-way analysis of variance among the groups was probably significant (p<0.05), while the result of comparison of two samples was highly significant for NHG vs. FC (p<0.01) and probably significant for FA vs. FC (p<0.05).

Conclusion: The main limitation of FNAB diagnosis is encountered in differentiation between FA and FC as well as between NHG and neoplastic lesions (FA and FC). Morphometry, however, appears to provide a very useful information for the proper differentiation between these two entities.

Thyroid Carcinoma In Patients With Hyperthyroidism

N. Alan, O. Ozmen, L. Kabasakal, C. Onsel, B. Kanmaz, K. Sonmezoglu, H. Sayman, I. Uslu. Department of Nuclear Medicine, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.

AIM: The prevalence and the prognosis of thyroid cancer (TC) in hyperthyroidism (HT) remains controversial. The aim of the present study was to evaluate the prevalance and the prognosis of TC in pts with HT.

METHOD: The records of 1850 TC pts from1982 to 2002 were evaluated. Of 50 (3%) pts with TC had HT. The age range 23 and 74(42.7±12.2 yrs, 9 m, 41 f). Pts followed for 54.5±59.5 mo (from 6 mo to 23 yrs).

RESULTS: Of 19 (38%) pts had Graves disease, 9 (18%) pts had toxic adenoma, 20 (%40) pts had toxic multinodular goitre and 2 (%4) pts with subclinical HT. The majority of pts had papillary cancer (PC) (45 pts, 90%). There were only 3 (6%) pts with follicular cancer and 2 (4%) pts with Hurthle cell cancer. Of 30 (60%) pts had occult PC and 11 (%22) had multifocal cancer. According to the TNM 35 pts (70%) had stage I disease, 8 (16%) stage II, 6 (12%) stage III and 1 (2%) stage IV disease. Mean plasma Tg and TSH values were 35.79±70.38 ng/dl and 43.71±24.10 uIU/ml. Among these pts 30 (60%) pts treated with I-131, 16 (32%) pts followed by TSH suppression. Despite high uptake values 25 (83%) pts were ablated in one I-131 dose. Of 4 (13%) pts had 2 and 1 (3%) patient had 3 consequitive I-131 therapy within 6 mo intervals. The total given dose to the pts was 154.5±75.6 mCi (100 to 400 mCi). Among pts who had Graves disease 10 (53%) pts treated with I-131 and 9 (47%) pts followed by TSH supression. Among all pts 1 patient with Graves disease who had liver metastasis have died and the others are followed without any evidence of disease at present. CONCLUSION: In contrast with the previous studies, this study suggested that 1) TC with HT is not more aggressive than the others. 2) these pts can be treated with relatively less doses of I-131 probably due to higher uptake values 3) occult papillary cancer with or without multifocal disease developed in HT state may also be treated only by TSH supression without radioiodine therapy.

Impact of iodine deficiency/excess on thyroid morphology and function

G. Horvatic Herceg, I. Bracic, S. Kusacic Kuna, D. Dodig. Clinical Department of Nuclear Medicine and Radiation Protection University Hospital Zagreb, Zagreb, Croatia.

Low iodine intake is known as a main etiologic factor of endemic goiter development. The aim of this study was to estimate the significance of morphological and functional thyroid changes caused by iodine deficiency or excess.

The study was prospective, including 293 pts (261 women, 32 men, mean age 44). Iodine in casual urine sample provides a reasonably good estimate of iodine intake. Iodine deficiency (<100(g /L) was found in 78% of patients. Iodine excess was found only in patients treated with amiodarone. T3/T4 ratio was significantly decreased in the group with excess iodine intake. Frequency of hypo and hyperthyroidism was similar in iodine excess/ deficiency. Relation between estimated iodine intake and 131-I accumulation in thyroid was quantified. Regression analyses revealed that exponential decreasing function was the best fit of the measured points. All pts were submitted to ultrasound examination. In the group with excess iodine autoimmune thyroiditis was found 66,6%. There was no significant difference in proportion of diffuse goiter and normally sized thyroid with nodules in our groups. However, enlarged thyroid with nodules was found in significantly higher proportion (p<0,05) in deficient (52%) than in normal iodine intake (36%). There were no such changes in the group with iodine excess. In 145 patients with thyroid nodules ultrasound guided fine needle aspiration biopsy revealed 34 tumours. The ratio of follicular tumours and papillary carcinomas was 1,86 in the group with iodine deficiency and 1,80 in the group with normal iodine values. Majority of our patients suffer from insufficient iodine supply connected with nodular goiter as a common finding. Autoimmune thyroiditis was the most frequent in the group with iodine excess. Thyroid hormone profile was altered in a similar way in iodine deficiency as in iodine excess but T3/T4 ratio was significantly decreased in the group of pts with iodine excess.

Comparison of recombinant human Thyrotropin (rhTSH) and thyroid hormone with drawal in the management of differentiated thyroid cancer

M.L. Domínguez, C. Roiz, N. Zeidán, L. Bernardo, J.P. Suárez, B. Llana, P. Raigoso, A. Alvarez, T. Allende. Department of Nuclear Medicine of the Hospital Central de Asturias, Oviedo, Spain.

OBJECTIVES: The aim of this study is to evaluate if stimulation with rhTSH in patients with differentiated thyroid cancer(DTC), previously treated with near-total thyroidectomy, I-131 ablation and tiroxine(T4), is an alternative to thyroid hormone withdrawal for the diagnostic follow-up (thyroglobulin measurement and I-131 whole body scan). METHODS: We studied 12 patients(10 females,1 male,range 23-78years,mean age 60) with differentiated thyroid cancer,previously treated with near-total thyroidectomy and I-131 thyroid ablation.Histology showed 5 papillary and 7 follicular.Distant metastasis were present in 3 patients.12 I-131 whole body scans(WBS)were performed in anterior and posterior projections using an Elscint SP4 gamma camera (fitted with high-energy and parallel hole collima-tor). In addition, serum TSH, thyroglobulin(Tg) and antiTg antibodies determinations with an immunoradiometric assay (IRMA) were performed in all patients. The patient population was divided into 2 groups with similar pathology.Group I: 6patients(5females,1 male, age 48-73 years, mean age 65 received rhTSH (Thyrogen®,thyrotropin alfa; Genzyme, Cambridge, MA. The protocol was as follows: Day 1) 0,9mg rhTSH given intramuscularly, day 2) 0,9mg rhTSH given intramuscularly;day 3)oral dose of 5mCi (185MBq) of I-131, day 5) whole-body imaging(at 48h) and serum TSH,Tg and antiTg antibodies measurement.Group II:6 patients(6 females,range 23-78 years, mean age 51 with thyroid hormone withdrawal previous to I-131 dose of 5mCi (185MBq). Serum TSH, Tg and antiTg antibodies were performed just before I-131 dose,and WBS 24-48h after it. RESULTS: All patients had negative antiTg antibodies.

Group I: 4 patients had detectable serum Tg.After rhTSH administration,WBS was negative in 5 patients,4 of whom had a persistent detectable serum Tg .

Group II: 2 patients had previous detectable Tg.WBS was positive in 3 patients (2 in the thyroid bed and 1 in lungs and sacrum),and it was negative in 3 patients,2 of them with indectable serum Tg. Both methods were tolerated well.

CONCLUSION: 1)Hypothyroidism after thyroid hormone withdrawal is more sensitive in the identification of patients with persistent or recurrent DTC. 2)rhTSH is an useful and safe alternative to thyroid hormone withdrawal to avoid signs and symptoms of hypothyroidism and risk of tumor progresion in selected cases.

Influence of an induced hypothyroidism on tumor metabolism and tumor proliferation in thyroid cancer

D. Detlef (1), K. Marx (1), J. Hahn (2), K. Schomacker (1), T. Fischer (1), K. Raffelt (2), H. Schicha (1). (1) Department of Nuclear Medicine of the University of Cologne, Germany, (2) Institute of Inorganic and Analytic Chemistry, University of Cologne, Germany.

Objectives: In patients with thyroid cancer a hypothyroid state is normally used for diagnostic and therapeutic application of radioiodine. Apart of the aimed increase of iodine uptake, hypothyroidism in thyroid cancer is assumed to effect alterations in cancer metabolism and proliferation. Aim of this study was to assess further hormone dependent effects of a hypothy-roid state in patients with metastatic thyroid cancer in comparison to the euthyroid state. Methods: Blood samples of 10 patients with metastatic thyroid cancer were assessed in hypothyroidism in preparation to a radioiodine application and in euthyroidism after thyroid hormone substitution using 1H- and 31P- magnetic resonance spectroscopy. As control group we used 10 patients with thyroid cancer, now in remission after successful therapy. Results of changes in metabolism and proliferation in hypothyroid state were validated using cell cultures of thyroid cancer.

Results: Using spectroscopy in hypothyroidism we detected changes in lipid-, amino acid-and membrane-metabolism and quantified six different phospholipids in the blood samples: phosphatidylethanolamine (PE), sphingomyelin (SM), 1- and 2-acyl-lyso-phosphatidyl-cholines, phosphatidylinositol and phosphatidylcholine (PC). In comparison to the control group patients with metastatic thyroid cancer in hypothyroidism displayed an significantly increased membrane metabolism and an increased phospholipid consumption for membrane production as a hint for an increased cancer proliferation: e.g. in whole body the systemic concentration of SM, PE and PC, which are main components of thyroid cancer membranes, decrease significantly due to an increased membrane production. These results could also be verified in cell culture experiments of thyroid cancer cells.

Conclusion: Apart of the aimed increase of the radioiodine uptake in thyroid cancer cells hypothyroidism has noteworthy influence on cancer metabolism and proliferation. Our results underline the necessity to keep a diagnostic or therapeutic hypothyroid state as short as possible.

99 mTc MIBI as the marker for early stages of thyroid carcinoma

B. Huszno, F. Golkowski, M. Trofimiuk, A. Baldys-Waligorska, Z. Szybinski. Chair and Department of Endocrinology, Collegium Medicum, Jagiellonian University, Krakow, Poland.

Aim: Over ten years ago the accumulation of isonitryle analogue (MIBI-metoxyisobutylisoni-trile) in the thyroid neoplasms was demonstrated and thereafter it was introduced for early diagnostics of thyroid cancer. The aim of the study was to determine diagnostic efficacy of MIBI as a marker for early stages of thyroid carcinoma (T1-2; N0; M0). Material and methods: The study comprised 2046 patients (381 males and 1665 females aged between 19 and 83 years) that were seen for conventional scintigraphy of thyroid and were diagnosed with cold nodules. Subsequently 99 mTc-MIBI scintigraphy was performed. The study location was the Nuclear medicine Unit of the Endocrinology Department, Collegium Medicum, Jagiellonian University in Krakow and scintigraphy was performed using Superscaner Selo DS8 or a gamma-camera Digitrac ZLC - Siemens. All the patients had ultrasound examination of thyroid and cytologic assessment of fine needle biopsy of cold nodules carried out. Thyroidectomy was performed in 1st and 3rd Surgery Department, Collegium Medicum, Jagiellonian University in Krakow, in all cases if neoplasm was suspected as well as if increased accumulation of MIBI in cold nodule was demonstrated. Results In over 80% single nodules were detected. Out of all 2046 patients with cold nodules, 498 (24%) showed increased MIBI accumulation. Based on histopathological examination it was found that 63 (13%) were not thyroid neoplasms but Hashimoto disease or nodular hyper-throphy. In 264 cases (53%) benign adenoma was found, and remaining 171 patients (34%) were diagnosed with thyroid carcinoma. This demonstrates that based on the results of MIBI scintigraphy, the decisions concerning surgical treatment proved correct in 435 out of 498 patients and defines the diagnostic sensivity of method to be 83%. Concurrently, based on ultrasound examination and cytologic assessment of biopsy material, 615 patients (out of all 2046) were suspected for thyroid neoplasms. Most of the patients in this group were also found to accumulate MIBI in cold nodules. Histopathological examination performed after surgery confirmed thyroid neoplasms in 394 out of those 615 patients. No neoplasms were found in remaining 221 patients.

Conclusions: Isotopic examination applying a marker such as MIBI for malignancies, is no inferior to cytologic assessment and may even prove to be more effective.

Incidence Of Second Primary Cancer Among 1000 Thyroid Cancer Patients

T. Ozulker, F. Ozulker, E. Uyanik, M. Mulazimoglu, M. Çabuk, O. Eker, E.E. Ozgonenel, R. Sahin, T. Ozpaçaci. Department of Nuclear Medicine of the Okmeydani SSK Hospital of Istanbul, Istanbul, Turkey.

Aim: There are studies in the literature reporting that there's an increase in the occurence of certain tumors in patients with thyroid cancer.Up to now there has been several studies suggesting that there is an increase in the incidence of cancers of breast, kidney, bladder, endocrine glands, central nervous system and leukemias in patients with thyroid cancer. It has been claimed that, close medical survey, developments in thyroid cancer treatment, hereditary factors, and increase in the number of autopsies might be the cause of increase in the incidence of these tumors. In this study we aimed to assess the incidence of the second primary tumors in patients with thyroid cancer.

Materials and methods: For this purpose we investigated 1030 thyroid cancer patients who have been followed in our clinic since 1980.

Results: Totally in 36 patients (24 women, 12 male) tumor in a second focus were detected (%3,4). In one of these patients with papillary thyroid cancer there were two other sites of cancers (Breast cancer and hypophysis tumor) Among these tumors, the the most frequently encountered one was breast cancer; 13 cases (%36,1). In the other patients; 6 larynx cancers ( %16,6), 5 gastrointestinal system cancers (%13,8), 2 lung cancers (%5,5), 2 malign melanomas (%5,5), 2 hypophysis tumors (%5,5), 2 pheochromocytomas (%5,5), 2 endometrium cancers (%5,5), 1 tongue cancer, 1 chondrosarcoma, 1 gingiva cancer were detected. Conclusion: In our study an increase in the incidence of breast cancer in patients with thyroid cancer is observed. The reports of the past studies suggesting that the patients with thyroid cancer are at increased risk of leukemia, kidney and bladder cancer are not confirmed in our study.

Expression of Sodium-Iodide Symporter (NIS) in Thyroid Diseases: Comparison of RT-PCR and Immunohistochemical Staining Methods

S.K. Bae (1), K.D. Lee (2), H.K. Jang (3), Y.S. Choi (4). (1) Department of Nuclear Medicine, Kosin Medical Center, Busan, Korea, (2) Department of Head & Neck Surgery, Kosin Medical Center, Busan, Korea, (3) Department of Pathology, Kosin Medical Center, Busan, Korea, (4) Department of Internal Medicine, Kosin Medical Center, Busan, Korea.

Aim: The sodium-iodide symporter (NIS) expression may be an important factor in determining the sensitivity to radioiodine therapy in well-differentiated thyroid cancers. The expression of NIS was analyzed in thyroid tissues of patients with well-differentiated thyroid cancer, medullary cancer, adenoma and nodular hyperplasia.

Materials & Methods: We measured the expression of NIS by reverse transcriptase-poly-merase chain reaction (RT-PCR) and also by immunohistochemistry using anti-NIS Ab in thyroid cancers and other benign diseases. We compared semiquantitatively the results of each method.

Results: We included 19 papillary carcinomas, 1 follicular carcinoma, 1 medullary carcinoma, 4 adenomas and 7 nodular hyperplasias. By RT-PCR analysis, 10 of 19 papillary carcinomas expressed NIS, but 1 follicular cancer didn't express NIS. By immunohistochemical staining, 15 of 19 papaillary carcinomas express NIS, but 1 follicular cancer didn't express NIS. There was a significant correlation between the semiquantitative results of RT-PCR and immunohistochemical staining of NIS expression. (p<0.01)

Conclusion: Our data demonstrated that the expression of NIS in thyroid cancers and other benign diseases investigated by RT-PCR and immunohistochemistry correlated well each other. However, by immunohistochemical staining, more NIS expression was found.

Explanatory patient variables for, and prognostic significance of success of I-131 ablation in differentiated thyroid cancer

F.A. Verburg (1), B. de Keizer (1), C.L.J.J. Kruitwagen (2), P.M.J. Zelissen (3), I.H.M. Borel Rinkes (4), C.J.M. Lips (3), J.M.H. de Klerk (1). (1) Department of Nuclear Medicine, University Medical Center Utrecht, (2) Center for Biostatistics, Utrecht University, (3) Department of Endocrinology, University Medical Center Utrecht, (4) Department of Surgery, University Medical Center Utrecht.

Generally, patients with differentiated thyroid carcinoma are treated with (near) total thy-roidectomy followed by I-131 ablation.

Aim: (a) to examine eleven thyroid cancer related variables that are available around the time of I-131 ablation for prognostic significance with regard to success of ablation of remaining normal and/or neoplastic thyroid tissue, and (b) to examine the prognostic significance of success of ablative dosage of I-131.

Methods: 173 patients whose thyroid cancer status one year after I-131 ablation was known, were studied retrospectively. All patients had successful (near) total thyroidectomy followed by an ablative I-131 dosage (3700-7400 MBq). Success of ablation was determined in all patients. Prognostic significance of success of ablation was examined in 126 patients treated before July

I, 1998, who were alive when determining success of ablation. Complete ablation was defined as patients showing no pathologic I-131 uptake on diagnostic scintigraphy performed one year after ablation, combined with undetectable serum thyroglobulin levels during hypothyroid status (Tg-off) and absence of any other evidence for the presence of thyroid (cancer) tissue. In patients in whom no diagnostic scintigraphy was performed, ablation was considered successful if Tg-levels during suppressive LT4 therapy were undetectable one year after I-131 ablation. Results: 64% of patients were considered to have successful ablation. In multivariate logistic regression, T-stage according to the TNM system (odds ratios: T0: 1, T1: 3.8691, T2: 1.2703, T3: 0.0002, T4: 5.4789), remaining lymph node metastases after surgery (odds ratio: 2.8905) and presence of distant metastases (odds ratio: 14.1444) turned out to be simultaneously explanatory prognostic factors with regard to success of ablation. Both thyroid cancer-specific survival (successful ablation: 97.3% (SE 2.7%) at ten years, unsuccessful ablation: 76.5% (SE

II.6%) at ten years) and disease-free survival (successful ablation: 92.6% (SE 4.1%) at five years, unsuccessful ablation: 39.4% (SE 9.6%) at five years) are significantly higher (P=0.007 and P<0.001 respectively) in patients who had successful ablation one year after I-131 ablation than in patients with unsuccessful ablation.

Conclusion: Simultaneously explanatory factors for success of ablation are T-stage, though surprisingly not in ascending order of stages, presence of lymph node metastases after surgery and presence of distant metastases. Patients with successful ablation one year after an ablative dosage of I-131 have a better prognosis with regard to disease-free and thyroid cancer-specific survival than those with unsuccessful ablation, indicating the importance of evaluating the ablation effect for further determining prognosis of thyroid cancer patients.

The clinical value of diffuse hepatic uptake of radioiodine in thyroid carcinoma patients

R.B.T. Verkooijen, M.P.M. Stokkel, J.W.A. Smit, E.K.J. Pauwels. Departments of Nuclear Medicine and Endocrinology of the Leiden University Medical Center, Leiden, The Netherlands.

Aim: Diffuse hepatic uptake (DHU) of radioiodine is a common feature on diagnostic and post-treatment scintigrams in differentiated thyroid cancer (DTC) patients. The aim of the present study was to assess the prevalence and its value in clinical practice. Materials and methods: DTC patients were selected who underwent ablation with I-131 between January 1986 and December 1999, followed by diagnostic scintigraphy with low-dose radioiodine and/or by additional treatment with I-131 in case of residual thyroid tissue. All post-ablation, post-therapeutic and diagnostic scans were visually analysed for the presence of thyroid remnants and DHU. Patients with metastases were excluded to preclude the possibility of I-131 uptake in livermetastases mimicking DHU. All scans were categorised according to the dose administered and the number of treatments. Finally, thyroglobulin (Tg)-off values measured at the time of diagnostic scintigraphy were gathered to study its relation with DHU.

Results: In 291 DTC patients, 228 post-ablation, 89 post-therapeutic and 168 diagnostic scans were available for analysis. DHU was seen in 185 of 228 (81,1%) post-ablation scans. Based on the ablation dose it was: 78,8% (26/33) 1060-1450 MBq (mean 1135); 79,1% (34/43) 1600-2300 MBq (mean 1893); 82,5% (113/137) 2600-3370 MBq (mean 2807); 50% (1/2) 3700-4400 MBq (mean 4033); 84,6% (11/13) >5800 MBq (mean 6179). Regarding post-therapeutic scans (mean dose 6059 MBq), DHU was seen in 75,4% (52/69), 82,4% (14/17) and 66,7% (2/3) after a second, third and fourth treatment respectively. In this group, the prevalence of DHU was not significantly different between scintigrams with or without uptake in neck region (p=0,20; 0,07; 0,08). The overall prevalence of DHU on post-ablation and post-therapeutic scans (n=317) was 79,8%. In 13 of 168 diagnostic scintigrams (7,7%) DHU was seen. The difference between DHU on scans with and without uptake in the neck region was not significant (p=0,57). Finally, the presence of DHU was not significantly different between patients with or without increased Tg values (p=0,78).

Conclusion: DHU is not unequivocally indicative for residual thyroid tissue. The difference in prevalence of DHU between post-ablation and post-therapeutic scans (79,8%) and low-dose diagnostic (7,7%) scans in DTC suggests a dose-related physiological phenomenon.

Scintigraphic Assessment of Endoluminal Bronchial Valves, an Alternative to Lung Volume Reduction Surgery (LVRS) in Chronic Obstructive Airways Disease (COAD).

M.J. Kelly (1), G.C. Salanitri (1), V. Kalff (1), G. Snell (2), T. Williams (2). (1) Department of Nuclear Medicine, Alfred Hospital, (2) Department of Respiratory Medicine, Alfred Hospital, Melbourne, Australia.

Aim: The benefit of LVRS in COAD is controversial because of a high complication rate. A potentially effective less invasive method may be endoluminal placement of one-way valves to block air entry and thus collapse affected lung zones. Our study assessed the physiological effects of this procedure.

Methods: Five patients with severe COAD suitable for LVRS, underwent this procedure to both upper lobe main bronchi. Assessment included pre-and post-operative Tc-99m Technegas and quantitative Tc-99m MAA studies, and also measurement of regional ventilation dynamics using Xe-133, ( 80 secs washin / equilibration and a 3.5 mins washout phase). The calculated index of washin was Xe-133 counts at 20 secs / Xe-133 counts at 80 seconds. Results: In all 10 treated upper lobes in patients with COAD substantial ventilation and perfusion persisted, and no radiographic collapse occurred. % perfusion to upper lung zones fell slightly from 31+27% to 26+10% (mean +SD): (P<0.01). Dynamic data were:

Xe-133 DATA WASHIN INDEX_WASHOUTT? (secs)

Lobe UPPER LOWER UPPER LOWER

Pre-Operative 1.00+0.16 1.62+0.29 126+84 68.8+13

Post-Operative 0.66+0.17 1.57+0.34 145+98 34.6+11

P: Pre vs Post <0.00001 NS NS <0.01

Conclusion: The decreased washin index to the treated lobes shows a significant effect of the endoluminal valve. The increased washout rate from the lower lobes suggests therapeutic benefit. However preserved volume, ventilation and perfusion in the treated lobes suggest continuing aeration via interlobar ventilatory connections with the untreated lobes.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition OTHER CLINICAL SCIENCE: MISCELLANEOUS

Assessment of dynamic changes in perfusion lung scintigrams of patients with CTEPH

N. Skoro-Sajer (1, 4), A. Becherer (2), W. Klepetko (3), M.P. Kneussl (4), I.M. Lang (1). (1) Department of Internal medicine II, Cardiology, (2) Department of Nuclear medicine, (3) Department of Cardiothoracic surgery, (4) Department of Internal medicine IV, Pulmonary medicine, Vienna General Hospital, Austria.

Background. Chronic thromboembolic pulmonary hypertension (CTEPH) is the result of single or recurrent pulmonary thromboemboli arising from sites of venous thrombosis. Over time thrombi become organized obstructions that are thought to expand by recurrent embolisation and in situ thrombosis.

Aim. We performed a quantitative evaluation of ventilation and perfusion scintigrams (V/Q scan) in patients with inoperable CTEPH in order to assess the natural history of thrombus expansion.

Material and methods. We prospectively studied 11 CTEPH patients (52±11years, 7 females, 4 males) over a period of 32,3 months. The baseline V/Q scan was obtained at the time of diagnosis. Ventilation imaging used [99mTc] DTPA aerosol and perfusion imaging was performed with intravenous [99mTc]-labeled human albumin macroaggregates. Planar images were reconstructed in eight standard projections. The right lung (RL) and the left lung (LL) were subdivided into an upper (LU,RU), middle (LM,RM) and lower (LL,RL) region of interest (ROI). The ratio of the mean count per pixel in the ROI to the count over the heart was calculated as the Lung/Heart index (L/H). The RL and LL variation coefficient (Vc), i.e. the ratio of the count standard deviation and the average count of the ROI were evaluated

from the same planar scintigrams. Student's paired t-test was used to analyze baseline and fol-

low up data.

Results.

L/H L/H L/H L/H L/H L/H Vc Vc MPA CO PVR

LU LM LL RU RM RL LL RL Pmm Hg l/min Wood

Baseline 3,9± 6,9± 4,3± 4,2± 6,9± 4,2± 51,7± 58,5± 48,4± 4,0± 9,8±

1,8 3,1 1,9 1,5 2,1 1,1 8,0 7,4 14,6 0,6 4,6

Follow 6,5± 9,1± 6,8± 6,5± 9,4± 5,5± 44,4± 45,5± 51,3± 3,8± 10,2±

up 3,2 3,8 3,4 2,4 2,5 1,2 8,4 8,2 8,0 0,7 3,3

P-Value N.S. N.S. N.S. 0,0083 0,0024 N.S. N.S. 0,0017 N.S. N.S. N.S.

Conclusions. Lung perfusion scintigrams in patients with inoperable CTEPH show a decrease of segmental flow abnormalities. We speculate that, over time, secondary vascular changes determine the course of CTEPH and ultimately lead into the scintigraphic pattern of non-thromboembolic pulmonary hypertension.

A comparative study of serum KL-6,Ga-67 scintigraphy and Tc-99m DTPA aerosol scintigraphy in patient with interstitial pneumonia

S. Ogi (1), D. Tsuchida (1), N. Fukumitsu (1), M. Uchiyama (1), Y. Mori (1), S. Tominaga (2). (1) Department of Radiology, The Jikei University School of Medicine, Tokyo, Japan, (2) Department of Internal Medicine, Juntendo University, Urayasu Hospital, Tokyo, Japan.

Aim: Ga-67 scintigraphy is useful in the evaluation of the activity and follow-up of interstital pneumonia(IP). Tc-99m DTPA aerosol(DTPA) scintigraphy is known to be more sensitive than CT in alveolar-capillary membrane permeability of IP. In general, DTPA aerosol clearance is accelerated in IP. KL-6 that is serum marker for IP is known to be useful as a parameter of the activity of IP clinically. The purpose of this study was to investigate the utility of Ga-67 scintigraphy and DTPAaerosol scintigraphy for IP in comparison with Serum KL-6. Methods: Forteen cases clinically diagnosed as IP were studied. Serum KL-6 was measured and Ga-67, DTPA aerosol scintigraphies were performed on the same period in all patients. Ga-67 scintigraphy was classified into 4 groups(gallium score; from score 0 of normal to score 3 of higher accumulation than the liver) and half time(T1/2) of DTPA aerosol clearance was obtained by time-activity curve of radioaerosol clearance.

Results: The value of serum KL-6 was 1004±861U/ml(mean±S.D.), which was higher than the normal limits. Gallium scores were variable. T1/2 of DTPA aerosol clearance was acceler-ated(T1/2=32.4±14.2minutes). There was no significant correlation between serum KL-6 and gallium score, however there was the significant correlation between serum KL-6 and T1/2 of DTPAaerosol clearance(y=2231.6-38.0x, p<0.05).

Conclusion: Tc-99m DTPA aerosol scintigraphy may be more useful than Ga-67 scintigraphy as evaluation of the activity of IP.

Alneolar-capillary permibility in stage-I sarcoidosis

D. Akrividou (1), A. Rapti (2), G. Panoutsopoulos (1), M. Laskou (2), C. Batsakis (1), G. Douskas (1.), S. Boutsali (1.), J. Christacopoulou (1.). (1) Nuclear Medicine Dept, General Hospital, (2) 8th Pulmonary Clinic, General Hospital, Athens Greece.

Background: The clearance rate of inhaled of Tc-99m-DTPA aerosol from the lung, provides a rapid non-invasive index of pulmonary epithelial permeability. Previous studies demonstrated increased clearance rate of Tc-99m-DTPA aerosol in stage II and III sarcoidosis due to destruction of the alveolar-capillary epithelium.

Aim: Aim of this study was to evaluate the pulmonary clearance rate of Tc-99m-DTPA aerosol in patients with stage I sarcoidosis, in whom parenchymal involvement is not apparent. Patients and Methods: We studied 86 individuals [43 with stage I Sarcoidosis, (group A) 19 with stage II and III (group B) and 24 healthy controls with matching age and sex profiles]. All individuals were non smokers. Diagnosis of sarcoidosis was established by biopsy confirmation, while staging was based on High Resolution CT, and Gallium scan findings. Healthy controls and patients of group Ahad normal spirometric data.

Immediately after inhalation of Tc-99m-DTPA aerosol, data were acquired in posterior view for 30 minutes. Four regions of interest were outlined for each lung (upper, middle, lower part of lung, and entire lung). The clearance of Tc-99m-DTPAwas expressed as the percentage of decline of counts per minute. Statistical analysis was performed using the Mann-Whitney U-test and p-value less than 0.05 was accepted as been statistically significant. The results are tabulated as follows :

Control Group_Group A-Stage I_Group B-Stage II,III

Clearance rate 0.53 ± 0.26 %/min 1.2 ± 0.94 %/min 2.4 ± 1.6 %/min

Entire lung (1) (2) (3)

Clearance rate 1.0 ± 0.3 %/min 1.7 ± 1.0 %/min 2.7± 1.8%/min

Lower zone (4) (5) (6)

(2)vs(1) : p< 0.01 (3)vs(2) : p< 0.02 (3)vs(1): <0.001

(4)vs(1): p<0.01 (5)vs(2):<0.02 (6)vs(3) : NS

The pulmonary clearance was significantly increased in patients with stage II and III sarcoido-sis in comparison with the control group and group A, as it was expected. But, the same finding was also observed in patients with stage I sarcoidosis as compared with the healthy coltrols. Although the higher clearance rate in every group was observed in the lower zones in comparison to the others, statistically significant difference among them was observerd only in the control group and group A.

Conclusion: In patients with sarcoidosis stage I pulmonary clearance is increased, a finding consistent with parenchymal involvement, which is not apparent with conventional methods. This marker may have a prognostic value for the evolution of the disease.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition PHYSICS 1

Validation of anatomic standardization of normal brain for FDG-PET: SPM and NEUROSTAT

K. Hosaka (1), S. Sakamoto (2), K. Ishii (1), M. Senda (2), H. Fukuda (3), T. Kato (4), K. Sugimura (1). (1) Department of Radiology, Kobe University, Kobe, Japan, (2) Department of Image-based Medicine, Institute of Biomedical Research and Innovation, Kobe, Japan, (3) Department of Nuclear Medicine and Radiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan, (4) Department of Biofunctional Research, National Institute for Longevity Sciences, Obu, Japan.

Aim: Recently spatial normalization techniques for intersubject analysis of PET have been widely used, however these methods are not well evaluated, especially for 18F-FDG PET images. The purpose of this study was to evaluate the anatomic precision of spatial normalization of Statistical Parametric Mapping (SPM) and NEUROSTAT for PET images in normal subjects.

Materials and Methods: Twenty healthy normal subjects (M: F=19:1, mean age: 38.1+/-18.9 years old) were recruited for FDG PET and high resolution T1- weighted MRI studies. First PET and MR images were coregistered in each individual subject. The Sylvian fissures and cingulate sulci were marked on the brain surface of each individual's MR images. Then spatial normalization was performed on the PET images of each subject using SPM99 and NEUROSTAT with NEUROSTAT's FDG template image. MR images of each subject, whose Sylvian fissures and cingulate sulci were marked in advance, were normalized using the transformation parameters obtained from the PET normalization by SPM and NEUROSTAT, respectively. The coordinates of the each subjects' Sylvian fissures and cingulate sulci detected on the normalized MR images by SPM and NEUROSTAT were obtained and compared to those on the template images, and deviations from the averaged coordinates on representative coronal plane were evaluated. Additionally, we evaluated individual difference of brain shape normalized by SPM and NEUROSTAT.

Results: The difference of the averaged deviation of the marks on Sylvian fissure transformed by SPM and by NEUROSTAT on the representative coronal slices remained no more than 0.9 mm, and that for the cingulate sulci was no more than 0.5 mm. The number of voxels that were within the brain volume in normalized MRI of all 20 subjects was 88.0 % of the total number of brain volume of SPM voxels and 85.3 % for NEUROSTAT. Conclusion: The result of this study demonstrated that SPM and NEUROSTAT yielded relatively small differences as spatial normalization algorithm and that both methods are effective and valid for normal subjects' PET study.

Lung lymphatic dynamics visualized with modulated liposomes

M.F. Botelho (1), C.M. Gomes (1), J.J.P. de Lima (1), M.L. Silva (2), M.F. Baganha (3). (1) Biophysics Department, IBILI - Faculty of Medicine, (2) Experimental Investigation Laboratory, HUC, (3) Pneumology Center of Coimbra University, Coimbra, Portugal.

Objectives: The development of a methodology to visualize the deep lung lymphatic drainage in an experimental model (swines), using modulated 100 nm diameter liposomes, administered by inhalation, after labeling with 99mTc-HMPAO.

Material and methods: The liposome double layer, based upon Bacillus subtilis capsule spores, consisted of distearoylphosphatidylcholine, phosphatidylglycerol, N-acetylmuramic acid and cholesterol in molar concentrations of 7.5:1.5:0.5:0.5. The liposomes were measured and evaluated for stability and citotoxicity. After 99mTc-liposomes inhalation a 60 min dynamic acquisition at thorax level, 64x64 matrix, at 2 frames/minute, was carried out. Static images, 128x128, with 2 minutes of individual duration every 30 minutes, for 5 hours, of thorax and pelvis, were subsequently acquired. To confirm the lymph nodes localization, two swines were injected, in the first interdigital space of both feet, with albumin nanocolloid labeled with 99mTc. For the lymphoscintigraphy a 60 min dynamic acquisition, at pelvis level, 64x64 matrix, 2 frames/minute, was followed by a pelvis static image, 128x128, 60 min after interdigital injection. To confirm the anatomical localization of the mfTadiafTagmatic lymphatic chains, two other swines were interdigitally injected with patent blue. To cross check, in one swine, inhalation of native 99mTc-HMPAO aerosol was made, in order to compare with the images obtained with the radioliposomes. For 99mTc-HMPAO aerosols, a 20 min dynamic acquisition was performed, at thorax level, 64x64 matrix; 6 frame/min, followed by static images, 128x128, at 20, 30, 45 and 60 min, of the thorax and pelvis. Results: 10 min after inhalation the hilar drainage was visualized. 30 min after, transdiafrag-matic drainage is already present as well as the visualization of the aortic chain. One hour after inhalation, the periaortic and inguinal lymph nodes are observed. These localizations were confirmed with patent blue. After injection of 99mTc-albumin nanocolloid and passive movements of the feet the lymphatic ducts of the posterior limbs was visualized at 17 minutes, the popliteal node at 25 min and the nodes of aortic chain at 30 min. Inhalation of 99mTc-HMPAO aerosol showed no visualization of the lymph nodes.

Conclusions: The liposomic formulation developed, that showed to be stable and maintained its physical characteristics, with a high specificity for the deep lung lymphatic drainage and no citotoxic, seems to be useful for the visualization and dynamic evaluation of the deep lung lymphatic drainage. Simultaneously, may play an important role in lymphatic lung delivery of pharmaceuticals, namely, cytotoxic drugs.

Binding Potential for [11C]Raclopride PET: Cluster Analysis for Reproducible Determination of the Reference Tissue

G. Glatting (1), J. Karitzky (2), A. Baune (3), J. Ruckgaber (1), K. Henkel (3), C. Solbach (1), F.T. Sommer (3), G.B. Landwehrmeyer (2), S.N. Reske (l). (1) Abteilung Nuklearmedizin, Universität Ulm, Ulm, Germany, (2) Abteilung Neurologie, Universität Ulm, Ulm, Germany, (3) Abteilung Neuroinformatik, Universität Ulm, Ulm, Germany.

Aim: A reference tissue model is widely used for the calculation of binding potentials (BPs) in ["Cjraclopride PET studies. The aim of the present study was to improve the determination of time activity curves (TAC) of the reference tissue using cluster analysis. Materials and Methods: In 5 subjects with Huntington Disease (1 female, 4 male; mean age 40 years, range 26-55; mean total functional capacity 11, range 9-12; mean disease duration 3 years, range 2-4), each with two consecutive investigations, TACs of a cerebellar reference region were calculated either from manually placed circular regions of interest (ROIs) within the cerebellum or by cluster analysis. PET data were acquired dynamically (17 frames, 5-600 s, total 60 min) in 3D mode (CTI ECAT EXACT HR+, Knoxville, TN) after application of [11C]Raclopride (doses: (6.8±0.8) mCi; specific activity (0.79±0.42) Ci/mmol) and reconstructed using the PROMIS algorithm (cutoff 0.5). The manually TAC consisted of six circular ROIs (diameter 3.2 cm), placed on three subsequent planes. For each investigation 10 k-means cluster analyses with k=10 were performed. The mean quadratic quantization error (MQQE) of the data points with respect to their class prototypes, the TACs of different cluster centres and their sizes were compared.

Results: A high MQQE reproducibility was found (signal to noise ratio (SNR) of 1-23 106). The comparison of the obtained TACs ('venous', 'cerebellar', 'striatal' and 'thalamocortical') demonstrated that the high SNR for the MQQE results in a high reproducibility: the SD for the activity in every frame for these tissues was less than 0.13% of the mean compared to 0.55-27% for the manually drawn ROIs. BPs for patient no. 3 assessed using TACs of the cerebellar cluster and the manually drawn cerebellar ROIs (mean±SD) with the receptor parametric mapping (RPM) software (Gunn et al. 1997) are given in the table (number of ROIs or cluster analyses N).

Cerebellar cluster

Cerebellar ROI

3a 4 1.40±0.001 5 1.25±0.10

3b 6 1.28±0.001 5 1.12±0.04

Conclusion: Reproducibility and variability in BP estimates derived from cluster analysis compared favourably with manually placed cerebellar ROIs and suggests the use of cluster analysis in defining reference tissue regions. The higher BP obtained by the cluster reference ROIs is compatible with the presence of specific binding sites in the manually drawn ROIs.

Internet-Accessible Daemon for The Probabilistic Anatomical Labeling of Brain Structures in ICBM Standard Coordinate

J.S. Kim (1,2), J. S. Lee (1), D. S. Lee (1), K. J. Seong (2), J. K. Chung (1), M. C. Lee (1). (1) Seoul National University College of Medicine, Seoul, Korea, (2) Department of Mechanical Engineering, Dongguk University, Seoul, Korea.

Aim: While the use of statistical parametric mapping (SPM) program has increased for the analysis of brain PET and SPECT images, anatomical location of the areas revealed by SPM has been determined by looking up the Talairach atlas. However, the disparity between Talairach coordinate and ICBM (International Consortium for Brain Mapping) standard coordinate used in SPM program made the interpretation of SPM result time consuming and subjective. The aim of this study was to develop an Internet-accessible program to provide objective anatomical information of each x-y-z position in ICBM coordinate. Material and Methods: Program was designed to provide the anatomical information for the given x-y-z position in ICBM coordinate based on the Statistical Probabilistic Anatomical Map (SPAM) images of ICBM, which was used as a database to acquire probabilistic information on 98 anatomical structures of SPM templates. When x-y-z position was given to the program, names of the anatomical structures with non-zero probability and the probabilities that the given position belongs to the structures were tabulated. The program was coded using IDL language for the easy transplantation to any operating system or platform. In addition, Internet-accessible daemon was implemented using PHP language to support multiple concurrent requests.

Results: Real time retrieval of probabilistic information with 1 mm spatial resolution would be performed using both the programs. Internet accessible daemon will be available at http://nm.snu.ac.kr/SPAM/.

Conclusion: These programs are useful for the result interpretation of the image analysis performed on ICBM coordinate, as done in SPM program.

Comparative analysis of influence of filters in the results of gated single photon emission computed tomography images

H. Monteiro (1), G.E. Bier (2), M. Olandoski (3), D.B. Precoma (2), A.S. Yamada (2). (1) Philips Medical Systems, (2) NUCLEMAB, (3) Universidade Federal do Paraná, Sao Paulo, SP and Curitiba, PR -Brazil.

Aim: The purpose of this study was to determine and compare the influence of four known filters evaluating the ejection fraction, end dyastolic and systolic volumes from images obtained from GSPECT and processed by QGS software.

Material and Methods: Thirty patients who had normal perfusion studies from one day protocol aquisition images were enrolled. 370 MBq of technetium-99m tetrofosmin (MYOVIEW) was injected at rest and 1110 MBq during stress testing. Myocardial SPECT was performed using 180° acquisition, 8 frames per cardial cycle, total of 32 frames, 20 seconds per frame, 64X64 matrix, roving mask 38 (1.46 zoom), in a dual-head gamma-camera (VERTEX PLUS - ADAC/PHILIPS MEDICAL SYSTEMS). Images were processed with Auto Spect+ software, using four different common filters: F1 filtered back projection (FBP) butterworth with cut-off frequency 0.45, order 5.0.; F2 hanning cut-off 0.82; F3 gaussian cutoff 0.2 order 1.0 and F4 iterative butterworth cut-off 0.5 order 7.0. The reconstructed images were submited to QGS software to get the function cardiac values which were analized by statistics metodology.

Results: Statistics analysis demonstrated that the mean ejection fraction values are not significant different (p<0,0001), but the end dyastolic and systolic volumes results were significant different when using filter F4, using significant level of 5%.

Conclusions: Therefore the ejection fraction values did not show significant estatistics difference, different values were obtained with filter F4 when comparing the end dyastolic and systolic volumes results, maybe because of these filter uses iterative metodology so that it shows more different contrast and signal-noise ratio than FBP, modifying the edge detection by QGS.

Ex-vivo SPECT imaging of whole human brain specimens to measure the spatial resolution effect on quantification of primary auditory cortex functional activity

J.M. Marti-Climent (1), J. Arbizu (1), L.M. Villar (1), E. Artacho-Perula (2), R. Insausti (2), I. Penuelas (1), J.A. Richter (1). (1) Department of Nuclear Medicine. University Hospital. University of Navarra. Pamplona. Spain, (2) Human Neuroanatomy Laboratory, School of Medicine, Castilla-La Mancha University, Albacete, Spain.

Aim: The objective of this study was to establish a correlation between the gross anatomy of the transverse gyri of Heschl and the definition of primary auditory cortex (PAC) based on cytoarchitecnonic boundaries. This will permit to examine potential problems in the delimitation of ROIs in SPECT quantification of PAC functional activity.

Methods: The anatomical study was performed on 6 non-pathological human brains obtained from autopsy, and consisted in a morphometric study of the PAC on histological sections where length and width diameters and shape factor (elliptical and circular) were evaluated. The volume was also estimated using Cavalieri's principle.

Two whole brain specimens (4 hemispheres) were specifically prepared to perform a SPECT study using point sources positioned on the anatomical limits of the transverse gyri of Heschl, and anterior-posterior commissures (AC-PC). Two SPECT acquisitions of each case were achieved in an Orbiter 75 with a Neurofocal collimator (Siemens). Distances between the lateral-anterior (LA), lateral-posterior (LP) and medial (M) aspects of the Heschl's gyri were measured directly on each brain and on the SPECT images (FWHM 12 mm). Recovery coefficient (RC) was calculated at the center of that volume by convolution of a uniform activity distribution with a system gaussian response function. Results: The morphometric study of the 12 hemispheres showed PAC sections having elliptical geometry, with a mean width of 6.04±1.08 and length of 9.83±1.21 mm. An average of 12.2 sections (24.33±3.80 mm) per hemisphere delimited the PAC depth. The mean volume estimation was 829±210 on the right PAC and 884±232 mm3 on the left PAC. All measures were later on corrected by brain retraction due to histological processing (correction fac-tor=1.3). SPECT measures of the anatomical limits of Heschl's gyri and AC-PC compared to macroscopic distances showed mean deviations in each brain of 1.0±0.63 and 2.25±1.54 mm respectively. As a result of the anatomical study, PAC was modeled as a hot radioactive tube region having uniform elliptical sections. RC evaluated for the 12 samples showed a mean value of 0.38±0.08 ranging from 0.23 to 0.51.

None of the comparisons between hemispheres referred above showed statistical differences. Conclusions: Measurements of brain distances with SPECT presented a mean error lower than pixel size. However, the anatomical limits of Heschl's gyri exceed the real size of PAC and pose a problem of partial volume effect in SPECT studies that must be corrected.

IAEA upgrading of gamma cameras with PC/Windows based acquisition and processing system.

F.V. Fidler (1), P.M. Prepadnik (1), F.S. Fidler (2), M.M. Medved (2). (1) Clinic for Nuclear Medicine, University Medical Center, Ljubljana, Slovenia, (2) Faculty for Electrotechnics, University of Ljubljana, Slovenia.

Nuclear medicine computers for acquisition and processing of images from analogue gamma cameras in developing countries are in many cases faulty and technologicaly obsolute. The aim of our upgrading project as well as from England, India, China and Cuba with the financial support of International Atomic Energy Agency (IAEA) was the development of low cost PC based computer system.

The basic development demands for the system were: one acquisition card on ISA bus, image resolution up to 256x256, SVGA graphics, low count loss at high count rates, standard acquisition and clinical protocols incorporated in PIP (Portable Image Processing from England), on-line energy and uniformity corrections, high quality image printing and networking. The most functionally stable acquisition system tested on several international workshops and university clinics was the Slovenian one with a complete set of acquisition and clinical protocols, transfer of scintigraphic data from acquisition card to PC through PORT, count loss less than 1 % at count rate of 120 kc/s, improvement of integral uniformity index by a factor of 35 times with energy and uniformity corrections, reporting, networking and archiving solutions for simple MS network or server oriented network systems (NT). More than 300 gamma cameras in 52 countries were succesfully upgraded. The Windows based Slovenian acquisition and processing software MEDICVIEW extended the upgrading project to the development of general purpose medical graphic station with the capacity of processing NM studies, viewing radiology and US original and processed studies with developed additional analysis, archiving and reporting.

The project of upgrading the analogue gamma cameras yielded a high promotion of nuclear medicine in the developing countries by replacing the old computer systems with modern systems, improving the technological knowledge of endusers on workshops and training courses and lowering the maintenance cost of the departments.

Butterworth is the most suitable filter for time activity curves in nuclear medicine

H. Rajabi, M.P. Firoozabadi. Department of Medical Physics, Tarbiat Modarres University, Tehran, Iran.

Aim: During the last twenty years attempts have been made to find a standard method for filtration of activity-time curves in nuclear medicine. Nevertheless the 3-points filter (1 2 1 kernel) is commonly used as the main means of noise reduction from such data. Due to slow order and low cut-off frequency, sufficient noise reduction requires repeated application of the filter that may results in data distortion. Therefore this filter is not suitable for nuclear medicine data. The aim of this study was to determine the most suitable filter for activity-time curves among all known low-pass filters. We assumed the most suitable filter to be one that better matches the distribution of noise in the nuclear medicine data.

Methods and Materials: Nuclear medicine time activity curves were generated using standard techniques. Normally distributed noise was added to the curves. The noise free curves and noisy curves were transformed into the frequency domain considering possible aliasing. The ideal filter for each pair of noisy and noise free curve was calculated. The procedure was repeated 10000 times for each simulation of activity time curves. The ideal filters were averaged for each simulation separately. Different filter frequency functions were examined to find the one that best matches the calculated average filter.

Results: Among all common low-pass filters tested, the Butterworth exactly matched our calculated filter in all simulation. It was practically proved that Butterworth is the ideal filter for data with normally distributed noise.

Conclusion: Several random nature physical phenomena are involved in generation of nuclear medicine data, each with its own probability distributions, but the resultant distribution is approximately Gaussian. Normally distributed noise was added to simulated activity-time curves. The ideal filter to remove the noise completely was calculated. The ideal filters were very complex but the average of them was exactly the famous Butterworth filter. This proves that the most suitable filter for activity-time curves on the average is the Butterworth. But this does not mean that Butterworth is the ideal filter for each individual case. It is the best for the data type on the average.

Interactive online visualisation of SPECT and PET studies in clinical conferences

O. Nickel, C.T. Kadalie, M. Schreckenberger, W. Eichhorn, P.A. Bartenstein. Department of Nuclear Medicine, Johannes Gutenberg University Mainz, Germany.

Aim: Online presentations of SPECT and PET tomograms allow new ways of visualisation and navigation in 3D data. Therefore an interactive program for image display of emission tomograms was developed, which can be used in clinical conferences. This program was tested and compared to conventional DICOM viewers.

Material and Methods: The program is written in object oriented Pascal (Borland Delphi) and runs on networked Windows PCs. Image data are loaded over FTP from any nuclear medicine workstation by using an integrated FTP client. One of the workstations can be used as a server containing lists of patients and studies prepared for demonstration. The program reformats volume data into transaxial, coronal and sagittal planes. Maximum intensity projections are generated, which can be interactively rotated; these are processed with a special algorithm preserving the depth information and providing a true 3D view. The program was used up to now in 3 clinical departments, in the orthopaedic, surgical and neurological clinics of our hospital.

Results: The installation on all PCs available in the viewing rooms was done without problems. The loading from network and reformatting of patient studies for demonstration is easy and very fast (about 5 seconds for a whole body PET). The acceptance of the physicians is very good because of the interactive presentation, especially the 3D visualisation gives more vivid insight into the patients body. With the conventional DICOM viewers only the presentation of screenshots is satisfactory, because PET and SPECT tomograms are not yet handled sufficiently.

Conclusion: The use of a presentation program adapted for emission tomograms can be recommended for an optimal demonstration of PET and SPECT. The acceptance of these modalities compared to MRT and CT is improved very much by interactive navigation and 3D visualisation.

An algorithm for adjustment of a filter to individual data

H. Rajabi, M.P. Firoozabadi, H.R. Ghiasi. Department of Medical Physics, Tarbiat Modarres University, Tehran, Iran.

An algorithm for adjustment of a filter to individual data

Aim: Nuclear medicine data are contaminated with noise and application of some kind of filter is usually unavoidable. Removal of the noise from data is not a simple task if the data and noise have common frequency components. Filtering of noise in common frequencies may results in data distortion or insufficient noise reduction. Optimum filtration, i.e. maximum noise reduction with minimum data distortion, may be possible when signal-to-noise ratio is known. The aim of this study was to find a method to adjust a filter to individual data sets without any knowledge of signal-to-noise ration.

Methods and Materials: Conventional methods were used to generate artificial renogram. Noise with normal distribution was added to the curves. Based on previous experiment Butterworth filter was used as the most suitable filter. Filtration was started using arbitrary cut-off and order for the filter. After application of the filter, the differences between corresponding points in noisy filtered and noise free curves were calculated as residual noise. It was assumed that the residual values obey Gaussian distribution. The above procedure was repeated changing the filter parameters until the condition was satisfied. The efficiency of the proposed algorithm to remove noise from renogram was evaluated and the amount of data distortion was calculated in terms of root mean square error between original and noisy filtered curves. The result produced by the method was compared with 3-points conventional filter widely used in nuclear medicine.

Results: The algorithm removes the noise up to a certain level. In each individual case the proposed algorithm was able to bring RMSe to a level significantly less than the conventional 3-points filter.

Conclusion: The count recorded in each pixel of nuclear medicine image is the result of a measurement, which includes some degree of uncertainty. This type of uncertainty is called noise and filters are used to suppress the noise. We have assumed that the filtered curve is the best fit to the noisy data in which the residuals obey a Gaussian distribution. The new algorithm is able to find such fit to the data. The efficiency of the algorithm is directly related to the statistical method being used to examine the normality of the residual distribution.

Dose calibrator performance in Belgium : First results

E. De Geest (1), N. Gerardy (1), F. Jacobs (2), F. De Vos (2), K. Persyn (1), R.A. Dierckx (2). (1) AV Controlatom, Brussels, Belgium, (2) University Hospital Gent, Gent, Belgium.

Aim: The Belgian law of 02/10/97 enforces the availability of a radiation physicist for each nuclear medicine division in Belgium. The aim of the study was to compare the reliability of the dose calibrators used in a nuclear medicine setting, in order to suggest guidelines for radiation physicists.

Material and method: Fourteen nuclear medicine departments were randomly selected. A protocol was set up to test dose calibrators, based on international guidelines. Background activity (norm: <100kBq) was measured in each department. With a 57Co point source, we determined the accuracy (norm: <10%) and reproducibility (norm: <5%) of each dose calibrator. Isoresponse curves and lineariry (norm : <5%) were calculated with 99mTc point sources. The influence of the geometry of the recipients (norm : <5%) has been analysed by successive dilution of a 2 GBq 99mTc -source.

Results: Twelve of the fourteen investigated dose calibrators produced accurate measurements. One dose calibrator has been excluded from further analyses, since it showed a deviation of >50%. Five dose calibrators gave background levels slightly higher (up to 300kBq) than allowed, which emphasizes the importance of autocalibration. The observed levels, however, were negligible when compared to the activities normally encountered. Concering linearity and geometry, no calibrator exceeded the prescribed standards. Our tests also show that the syringe-holder delivered with the dose calibrator has to be used to obtain precise results. All results were reproducible.

Conclusion: Radiation physicists should check the accuracy and background level of each dose calibrator. If the observed background levels are high, autocalibration should be used. The syringe-holder delivered with the dose calibrator should be used.

Three-dimensional (3D) semi-automated segmentation of FDG-PET images: influence of reconstruction algorithms on volumetric accuracy.

J.-F. Daisne (1), M. Lonneux (2), M. Sibomana (2), A. Bol (2), T. Doumont (2), V. Grégoire (1). (1) Radiation Oncology Department, Université Catholique de Louvain, St-Luc University Hospital, Brussels, Belgium, (2) PET Laboratory, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.

Aim: In the framework of a routine use of FDG-PET images for Head & Neck tumor delineation in radiotherapy treatment planning, the objectives of the study were : 1) to find a relationship between Source/Background (S/B) ratio and threshold to be applied for automatic volume segmentation, and 2) to assess the influence of different reconstruction algorithms on this relationship.

Materials and Methods: A circular phantom object (21 cm diameter) containing 6 empty spheres with volume ranging from 0.55 to 17.15 ml was used. Spheres were filled with 74 -111 kBq/ml of 18F. Phantom was first filled with „cold" water (1 acquisition) then with increasing 18F activity concentrations (6 acquisitions) resulting in calculated S/B ratios ranging from 1.5 to infinite. Acquired images were reconstructed using either (1) a Filtered Backprojection (FBP) algorithm with either a Ramp or a Hann filter or (2) an iterative algorithm (FORE-OSEM) with and without Gaussian post-smoothing of 6 and 8 mm in each spatial direction, respectively. Iterative 3D thresholding was applied on the spheres until accurate volumetric estimation could be reached for the various background conditions. Corresponding threshold values were plotted as a function of the S/B ratio directly measured on the images, considering individual results for each reconstruction method used. Regression function analyses were performed. Thresholds derived from these functions were then applied on the source images to check their ability to adequately assess the various spherical volumes. Results: FBP-Ramp images were excluded since they were not interpretable for calculated S/B ratios lower or equal to 5. Relationships between threshold values and measured S/B were fitted through a power regression (r2 varying between 0.77 and 0.83, p<0.001). Depending on the reconstruction algorithm, the use of these regression functions led, on average, to a 21.6 to 87.91 % volume overestimation for objects < or = to 1.08 ml and to a 2.3 to 14.6 % volume underestimation for objects > to 1.08 ml.

reconstruction r2 volume overestimation volume underestimation algorithm_for small object1 (mean, %) for large object2 (mean, %)

FBP-Ramp 0.82 21.6 -4.5

OSEM 0.77 61.8 -5.1

OSEM 6mm 0.83 66.9 -2.3

OSEM 8mm 0.83 87.9 -14.6

1 volume < or = to 1.08 ml

2 volume > to 1.08 ml

Conclusion: 3D semi-automated volume thresholding method based on measured S/B ratios using FBP-Ramp reconstruction algorithm led to the more realistic estimations of spherical volumes in a phantom object. Validation of this method in a clinical situation by comparison with surgical specimens is in progress.

Double label techniques in pharmacokinetic assays: Simple determination of injected activity doses of nuclides in binary mixtures

A.T.J. Vogg, B. Neumaier, C. Solbach, G. Glatting, S.N. Reske. Abteilung Nuklearmedizin, Universitätsklinikum Ulm, Ulm, Germany.

Aim: Comparative determination of pharmacokinetics of two radiopharmaceuticals labelled with different gamma emitting nuclides within the same animal has several advantages: 1st Minimum relative biodistribution error if drugs are similar or different, 2nd Cost reduction (animals, working time) and 3rd Animal welfare. For biodistribution measurement of a binary nuclide mixture the exact injected activity doses has to be determined exactly. Therefore the activity of the filled and emptied injection syringe can be measured using gamma spectrometry. However, due to the relatively high activities and the complex sample geometry of a syringe this method is not workable. We established a new method to access nuclide activity doses in such mixtures by using an dose calibrator. The principal feasibility has already been demonstrated by DeNardo et al. (J. Nucl. Med. 37, 302-306 (1996)).

Materials and Methods: "Binary nuclide factors" (BNF) were derived mathematically. Dose calibrator display readings (Atomlab 100 plus, Biodex) have to be multiplied by the respective BNF's to yield the real activity of the nuclide chosen on the dose calibrator. BNF's were determined experimentally by preparing a complementary dilution series (100 % nuclide A / 0 % nuclide B to 0 % nuclide A / 100 % nuclide B). Samples were measured with the dose calibrator and exact nuclide activity contents were determined using gamma spectrometry. Since the BNF's are functions of the relative activity fraction of one of the nuclides additional knowledge of the initial nuclide composition of the parent solution is mandatory. Initial nuclide activities were determined by separate measurement of the radiopharmaceuticals using a dose calibrator before mixing.

Results: The in vivo biodistribution of two different radiopharmaceuticals in the same animal has been determined simultaneously by the new method using mathematically derived BNF's. Conclusion: By this new technique comparative pharmacokinetics with two labelled drugs in one animal are easily performed by using a dose calibrator and binary nuclide functions (BNF's), specific for each nuclide pair.

Renogram Analysis using Multi-Compartmental Modeling with Time Dependent Exchange Coefficients

T.A. Riauka (1), S.A. McQuarrie (2), S.A. Jackson (1), A.J.B. McEwan (1). (1) Department of Oncology, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada, (2) Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada.

The extraction of quantitative data from the nuclear medicine renogram is severely hampered by the inherent presence of noise. In cases where the renal function is poor and quantitative parameters would be most valuable, the signal to noise ratio is sufficiently small that standard methods of feature extraction can produce variable and unreliable results. The utilization of deconvolution analysis for example, works well with noise free data and produces clinically useful parameters. However, in the presence of significant amounts of noise, deconvolution methods can produce inconsistent results and consequently have not been widely adopted.

The renal analysis technique presented here exhibits several advantages over conventional techniques, particularly when dealing with noisy data. Our approach fits the clinical data to an analytical model that approximates the physical processes associated with the handling of renal radiopharmaceuticals such as 99mTc-DTPA and 99mTc -MAG3. Simulated annealing methods are used to obtain the time-dependent exchange coefficients by minimizing the difference between the time-activity curve obtained clinically and that predicted by an appropriate multi-compartmental model. The exchange coefficients can be directly related to the Estimated Renal Plasma Flow (ERPF) and Glomerular Filtration Rate (GFR) for MAG3 and DTPA respectively. The method provides excellent noise suppression without loss of information and allows further quantitative analysis to be reliably performed using the resulting modeled data.

The application of compartmental modeling and simulated annealing techniques will be fully described and comparative analysis with conventional analytical methods will be presented for several sets of clinical data illustrating the power of this technique.

Accuracy of the quantification of organ activity from planar gamma camera images.

K. Norrgren, S. Leide-Svegborn, J. Areberg, S. Mattsson. Department of Radiation Physics, University Hospital MAS, Malmo, Sweden.

The accuracy in determination of whole body and organ activity of 99m-Tcand 111-In was investigated in the study. The activity was estimated from gamma camera images of a phantom, using the conjugate view method. The accuracy depends on several parameters such as the choice of background correction method, the accuracy in determination of effective linear attenuation coefficient, the thickness of the body and organs and on the determination of the sensitivity.

The background correction method has a major influence on the quantification of the activity and methods which take the volume of the source organ into consideration are recommended. The discrepancy in the determined organ activity varied between an underestimation of 26 % and an overestimation of 9%, depending on which organ was studied and on the correction method used.

To correct for absorption and scattering, an effective linear attenuation coefficient was used. A theoretical analysis showed that a change in the attenuation coefficient of 0.01 cm-1 resulted in a 15% change in the calculated activity. Also the thickness of the body and the organ of interest influences the calculated activity. A 2 cm deviation in the body thickness gives rise to a deviation of 10 % in the calculated activity.

The whole body content using 99m-Tcand 111-In labelled radiopharmaceuticals can be quantified with an uncertainty of ± 3 %. For internal organs with a relatively high activity content, the uncertainty could be of the order of ± 10 % and for organs with clearly visible, but lower content it goes up to ± 30 %.

Count Efficiency of a Double-Well Single-Plastic Scintillation Counter to Radionuclides (Tl-201, Tc-99m, I-123, Ga-67, In-111 and I-131)

K.S. Sasaki, Y.I. Ihara, T.O. Oka, T.K. Kido, K.I. Itoh. Department of Radiology, JR Sapporo General Hospital, Sapporo, Japan.

Aim: A new type of well-scintillation counter with a double-well and single-plastic scintilla-tor was developed to simplify time consuming and cumbersome dilution procedures inherent to in-vivo sample measurement. We examined the count efficiency (CE) of the instrument with respect to 6 clinically available radionuclides

Material and Methods: The instrument has two wells, one dedicated to the injection syringe and collimated to a plastic scintillator using lead. For each radionuclide, we prepared two standard solutions containing high (>100 MBq/ml) and relatively low radioactivity (10~20 MBq/ml).The absolute radioactivity (Bq) of the radionuclide in each solution at time=0 was measured by a dose calibrator (IGC-3, Aloka, Japan). Afterwards, it was calculated from the physical decay time of each radionuclide. Each standard solution was counted in each well ten times per sample until the count rate was low, close to background level. For I-131, the measurement was completed in 6 months. The CE for each radionuclide was determined by cps/Bq x 100 (%) at time of measured radioactivity. The conversion constant (CC) was determined as a mean reciprocal value of CE.

Results: The linearity between measured radioactivity (cps) and standard radioactivity (Bq) in each well was evaluated: the CE among the 6 radionuclides were significantly different and tended to depend on the energy of the gamma ray emitted. The coefficient variation (CV) also depended on the measured radioactivity and was less than 1 % above 10A3 Bq. The CE was not significantly affected by sample volume from 1 to 4 ml in both wells. Conclusion: The new well-counter has the potential to allow for quantification of in-vivo samples, thus avoiding time consuming and cumbersome dilution techniques.

PACS as a smart tool for clinical audits in NM departments

S. Savolainen (1), T. Kauppinen (1,2), J. Ahovuo (1), H. Pohjonen (1), A. Suhonen (1), K. Harno (3), J. Kinnunen (1). (1) Department of Radiology, Helsinki University Central Hospital, Helsinki, Finland, (2) Division of Nuclear Medicine, Helsinki University Central Hospital, Helsinki, Finland, (3) Department of Medicine, Administration, Helsinki University Central Hospital, Helsinki, Finland.

The Council of the European Union issued the Medical Exposure Directive (MED) on the 30 of June 1997. Member States should have brought into force the laws and regulations necessary to comply with the directive before the 13 of May 2000. According to MED directive clinical audits shall be carried out in accordance with national procedures. Clinical audit is a systematic examination or review of medical radiological procedures which seeks to improve the quality and the outcome of patient care through structured review whereby radiological practices, procedures and results are examined against agreed standards for good medical radiological procedures, with modification of practices where indicated and the application of new standards if necessary.

The auditing process PACS can be used as a smart tool for the implementation of the whole audit schema into the clinical practice, especially, requirements: the competence of authorities and their responsibilities, the referral of examinations and the availability of guidance for purpose; the procedure of justification of exposure including the practice to obtain previous diagnostic information or medical records relevant to the planned exposure and consideration of these data to avoid unnecessary exposure; and the actions taken to ensure the quality of information obtained from exposures, the way to store the obtained data and the radiological workflow.

The Hospital District of Helsinki and Uusimaa (HUS) has a PAC system called HUSpacs connecting gradually all the 21 hospitals of the district including four divisions of nuclear medicine with the total amount of one million examinations (more than 20 TB) per year. The purpose of this study is to report how the modern intelligent PAC system can be used to obtain these requirements of the regulations stated by the MED directive concerning the use of ionisation radiation in medical examinations.

HUSpacs assures the availability and inexpensiveness of imaging services for people in the HUS-area. HUSpacs supports all care chains, in which radiological images are produced or the patients' previous images are viewed. Even the new radiation law makes the clinician and the radiologist to find out, what examinations have been made earlier. This is to avoid recurrent overlapping examinations and useless radiation exposure. In conclusion, it can be said that HUSpacs assists in whole clinical audit process.

PET and Cyclotron planning: the Reggio Emilia S.Maria Hospital experience

F. Fioroni (1), D. Salvo (2), L. Mondini (1), F. Colombo (3), M. Asti (2), A. Versari (2), D. Serafini (2), G. Borasi (1). (1) Medical Physics Department, S.Maria Nuova Hospital, Reggio Emilia (Italy), (2) Nuclear Medicine Department, (3) Nuclear Medicine Department, Policlinico Hospital, Milano (Italy).

The number of Pet and Cyclotron units required for each catchment area, has become very difficult to evaluate, due to the impressive increasing, in the last five years, of the Pet importance for medicine, with a particular reference to oncology. In Italy Emilia Romagna Region (about 4 million inhabitants, 9 Provinces) planned to install #3 PET and # 1 Cyclotron units in 1997. The latter had to be an high level unit (18 MeV), devoted to provide all the PETs with FDG in the Region and to give a contribution to the basic research in the field. On the basis of logistic considerations and of a careful analysis of the public demand for appropriated PET examinations, we have proposed an alternative plan, providing with one additional cyclotron unit located in Reggio Emilia. This unit had to feed the PET tomographs for our Province (about 450.000 inhabitants) and to serve the future needs of the adjacent Parma Province (about 400.000 inhabitants). Alocal Charity Organization (Manodori) has given an economical support to the Hospital Administration and, after an initial scepticism, the Regional Authorities have approved the new plan. We have had to face with two challenging requirements: a quick starting up of PET and Cyclotrons units and a cost-effective installation. We have followed four main guidelines.

Patients had not to wait for cyclotron installation times. In a very short time we activated the PET unit, buying FDG from a specialized Company (Iason). As a tomograph we chose an ADAC C PET Plus, a cost effective unit, totally fitting with oncology exams (S. Raffaele). The system was made operative in September 2000 and from then about 1400 patients were examined. The cyclotron and synthesis module had to be suited to a safe routine work, in a non-research hospital environment. The autoshielded 10 MeV cyclotron from GE (MINITRACE) and the fully automated synthesis unit from Coincidence well matched these requirements. Several chemical and physical control tests would assure the medicinal product quality. The site planning had to be rational and cost effective. We considered that the best location for cyclotron and Radiochemistry were in new underground rooms, connected with the existing building where Nuclear Medicine is located. UNI 10491 and cGMP regulation compliance were assumed as a reference for Radiochemistry planning (building from ORION, radiochemistry cells from Tema Sinergie, main contractor GE). The unit had to be designed for a totally safe operation.

On 14th March 2002, exactly after one year from the signature of the agreement, the first FDG production for clinical use was delivered. The total cost of the project, including PET, Cyclotron, accessories, building was about 3.000.000 Euros. At this time our unit (PET and Cyclotron) is the only one operative in our Region.

Radiation Detectors in Surgical Gamma Probes

J. Luo (1), J. Li (2). (1) Saint Vincents Catholic Medical Center of New York, (2) Beijing Capital Normal University, Beijing, China.

Purpose: Investigate features of semiconductor and scintillation crystal in surgical gamma probes for Sentinel lymph node mapping.in axillary dissection.

Method: two semiconductor gamma probes (CdTe) and a scintillation crystal (NaI(Tl)) were used with various settings in the sentinel node mapping in physics labs. and in operating rooms after lymphoscintigraphy in nuclear medicine. Traditional localization with blue dye was also applied to compare with the Tc-99m colloid method and to ensure detection of the sentinel nodes.

Result: Two semiconductor probes (CRC-4 from RMD and Navigator from US Surgical Corp.) demonstrated excellent energy resolution and good detection efficiency. Scintillation probe with NaI(Tl) crystal (Beijing Capital Normal University) showed about two times detection efficiency than the semiconductors. Energy window (20% ~ 50%) played an important role in identifying SN at low Tc-99m colloid uptake. Relative SN uptake (activity ratio of SN to tissue) is the key factor in the node mapping (2 ~ 30 and up to 300 were observed). Conclusion: Scintillation crystal demonstrated high detection efficiency. Detection efficiency and collimation are the most important factors in gamma probe design. The lymphoscintigra-phy will help surgeons find multiple nodes especially when the nodes are close to breast with high activity.

Telemetric monitoring of left ventricule ejection fraction measured by radionuclide technique.

K.D. Kalantarov, V.A. Viktorov, G.V. Petrik, V.G. Shibanov. Researche institute for medical engineering,Moskow Russia.

Ejection fraction index is very sensitive iscemic parameter of left ventricule during daily activity of patientes with iscemic lesion of heart.

Monitoring of ejection fraction wich realized by ambulatory portable instrument like VEST become very popular last years wiche has one disadvantages-impossibility to calculat ejection fraction [EF] in real time.Anouther instrument Cardioscint makes calculation in real time but its detector connected to PC by cable deprived patiente of autonomie.

We designed and realized portable instrument wich can calculats EF in real time at patient situated on 2-3 kilometer out of PC accumulting counts from precordial detector during 3-4 ours.It become possible by using telemetric transmission of data trough radiotelephon KXT9095.

Our instrument consisted of :

1. Scintillation probe with 2 collimators -one for heart another for background

2. Vest

3. Belt- portable box[asquisition electronic,pulse height analyser, prescaling, ECG amplifier,nuclear and ECG signal convertor,output for radiotelephone

4. Radiotelephone-emitter

5. Base of radiotelephone

6. Interface between base and PC

7. IBM PC

8. Package of clinical programmes.

Technical test shown stable performance of systeme at distance between patiente and base about 2-3 kilometer.Preliminary clinical evaluation will be presented.

An Easy and Safe Interchange of Nuclear Medicine Static, Tomographic, Dynamic studies and Data through Internet

M. Lyra, M. Tzamtzi, J. Jordanou. Department of Radiology of University of Athens, Athens, Greece.

Aim: The aim of this project was to fully implement alternative services that Internet offers to the easy transfer of complete patients' examinations. Prosperity of easy interchange in every day practice of Nuclear Medicine found its application through the Internet media. We use a simple and safe way to interchange images and diagnostic information between the scinti-graphic acquisition and processing location and the clinical department in order to improve patient's health care and young doctors' education. We present our experience in transferring patient data, SPECT slices, 3D SPECT images in video (movies) form and animation display to medical specialists.

Materials and Method: Images and patient reports are transferred and saved through dedicated software to a workstation that transform gamma-camera scintigraphic images in a PC readable format. Diagnosis reports and scintigraphic images are incorporated to a database directory in hypertext form. The gamma camera works under a RMX Operating System. The data are transferred to the local server PC via a Local Area Network - in which the medical system computer is also included- and are modified by procyon starlab software to BMP type image files. After the images have been transferred to the local PC as BMP files, an image-processing programme can manipulate them, in order to change the colour scale or emphasise at certain details. The series of images from the gamma -camera dedicated computer are transferred to the local PC. SPECT slices and/or 3D processed SPECT images as well as dynamic or gated studies can be send to the connected PC. The set of images is manipulated by standard video or animator producer software to create AVI or MOV or even GIF files. Medical record data are combined with the images and movies in a hypertext file that can be sent as an attachment via an e-mailer functioning under Windows environment. The receiver side should be equipped with a similar e-mailer and can view or print patient's set of images and data through a suitable browser. The mailed series of images are characterised by diagnostic quality analogous to that of the original sets that someone can see as simple series or in a cine form of tomographic slices, dynamic studies and 3D images in a gamma camera. Results: Transfer via e-mail has been used in our center for the exchange of complete studies including data, images and movies to and from our colleagues when particular patients are concerned. Furthermore, both patients' files and educational files can be downloaded, from our department ftp location, by a unique password.

Conclusion: E-mail transfer of a full patient template enables the archiving of particular files from the authors' Institute database ensuring the security desired and it has been proven to be a quick and safe mean of exchange of dynamic set of Nuclear Medicine Information between physicians and scientific centers. Usual WWW connection gives the possibility of patients' examinations transfer by email attachments as well as interchange of relative comments towards both directions. Cost effective solution has been achieved using standard hard- and software.

Integration of images nuclear medicine in the virtual clinical history of a health system.

C. Estebanez (1), E. Goni, J.L. Martinez (1), M.E. Martinez (1), J.A. Garbayo (2), R. Aisa (2), J. Martinez (2). (1) Medicine Nuclear departa-ment of Hospital of Navarra, Pamplona,Navarra,Spain, (2) Health information system departament. ( Navarra Health Care Service),Pamplona,Navarra,Spain.

The incorporation of the computer based clinical history has been an objective of the „Servicio Navarro de Salud" ( Navarra Health Care Service) since 1999. This service aims to integrate the personal clinical history of every citizen, from primary to specialist and hospital levels of health care, including all health departments of the „Comunidad Foral de Navarra" (Navarra Province). The health service seeks to integrate information managed in both medical assistance and administrative processes.

The Department of Nuclear Medicine at the Hospital de Navarra, has endeavoured to exploit the wide accesssibility of the virtual clinical history by transmitting along with the clinical history, relevant images to complement the medical report.

To do this, processed images at the Data Processing station recieved from the gammacameras (UNIX system), are transferred, through FTP, with the product REFLECTION, to a workstation integrated in the general network of the system. At this work station the images are transformed (tiff to jpg), by its own development program, and are saved in a server (Windows NT), from which these images are distributed to any part of the net.

Likewise, this file allows for a quick and simple consultation of images by doctors in Nuclear medicine in order to followup the course of patients.

When the medical report of a test in the computer based clinical history is consulted (accessible to all health care providers in the „Servicio Navarro de Salud"), the corresponding processed image appears simultaneously, given that, the section of the report has a reference to the file of the image.

The computer application of the clinical history is composed of the complete report, vinculat-ing the selected images to the text of the clinical report emitted for the test.

To protect the patient's right to intimacy, a hierachical system of accessibility and user profile is established for each person that may need to consult data from the clinical history, with the understanding that health care providers have the obligation to respect this right, just like it has been done with the traditional clinical history.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition PHYSICS 2

Performance of the TierSPECT: Limitations to Spatial Resolution and Sensitivity

A. Wirrwar (1), N. Schramm (2), H.W. Müller-Gärtner (1). (1) Nuklearmedizin des Universitätsklinikums Düsseldorf, Düsseldorf, Germany, (2) Zentralinstitut für Elektronik, FZ Jülich, Jülich, Germany.

We present performance measurements of a dedicated animal SPECT. The prototype of the TierSPECT (Figure 1) system was recently presented and consists of a single detector mounted to a gantry. The camera is controlled by a common personal computer and allows 360° rotation and radial translation of the detector head. Acquisition and all subsequent data processing are performed on the personal computer as well. The detector itself consists of a 3mm NaI(Tl) disk optically coupled to a position sensitive photomultiplier (Hamamatsu, R3292) which is enclosed in a aluminium housing with a 5mm lead shielding. The tomographical resolution of the system amounts to 2.8, which makes it suitable for SPECT in small laboratory animals. The time resolution of such cameras strongly depends on the pharmacological behaviour of the tracer and can range from several minutes to hours.

To prepare the observation of receptor kinetics in small animals, we built a rat phantom equipped with ellipsoidal and spherical volumes of 0.065ml-0.19ml. Previous in vivo and in vitro measurements of several receptor ligands show typical uptake ratios between 0.5 and 4.5% for the striatum. The activity concentrations in the chambers of about 1.5MBq/ml considered physiological restrictions and the specific activity of the radioligand. Using 99mTc solutions in the chambers, even with 10% background activity, the 3x7mm? shape of the striatum chamber can be recognised, volumes with 10mm in diameter can be resolved without partial volume effects. Using 123I solutions the septa penetration of the LEUHR collimator reduces the image quality: the ellipsoidal regions hardly can be recognised.

With the presented glass rat phantom it can be shown, that the low sensitivity of the actual camera limit the visualisation of the rat receptor system to static images or to dynamic setups without injection dose limitations.

Image removed by abstract editors

Quantitative reconstruction of 2D Yttrium-86 measurements using an ECAT EXACT HR+ positron emission tomograph

T. Kull, G. Glatting, J. Ruckgaber, R. Weller, S.N. Reske. Abteilung Nuklearmedizin, Universität Ulm, D - 89070 Ulm, Germany.

Aim: Y-86 is a positron emitting nuclide with a halflife of 14.74 h, which emits positrons with an abundance of 32% along with approximately 300% gamma radiation. The additional gamma rays of Y-86 were not only suspicious for an increase in both dead time and random coincidences if their energy falls within the energy window of the PET scanner, but also for coincidences between annihilations photons and gamma radiation, and/or coincidences between two photons of a gamma cascade. Consequently imaging properties are degraded when doing quantitative Y-86 PET measurements. Our aim was to identify artefacts and to develop a method to obtain quantitative in vivo Y-86 PET data by applying corrections to the standard (F-18) PET image reconstruction.

Materials and Methods: F-18 and Y-86 data of a cylinder phantom (IEC phantom) optionally with line source inserts or sphere inserts were acquired in 2D mode to evaluate scatter fraction, contrast ratios and count rate dependency. In extension to the method described in (K. S. Pentlow, R.D. Finn et al. Clin. Pos. Imag. 2000; 3: 85-90) we subtract a straight line in the sinogram, which is fitted to the apparent intensity contributions and calibrate the Y-86 activity concentrations depending on the count rates. The correction method was tested by comparing the measured activity concentrations and ratios obtained with the ROI method with the concentration values obtained with a calibrated well counter.

Results: A yield of 90% of all registered coincidences are found for F-18 inside of a 4*FWHM wide strip around the line source centre. For Y-86 only 24% of the coincidences are within this range. Using a branching ratio of 0.32 for Y-86 reconstruction a multiplication factor of about 2 is needed to calibrate the measured activity concentration at low count rate. At system dead times of 14 % an additional correction by a factor of 1.2 is required. After the approximative corrections the results of the measured activity concentration in the phantoms agree well with their true values.

Conclusion: Compared with the uncorrected reconstruction the additional corrections improve the quantitative imaging properties for Y-86 PET significantly for asymmetric activity distribution in the field of view.

Figure 1 TierSPECT

Reconstruction of Emission and Attenuation Images from PET Emission Data only

G. Glatting, M. Landmann, S.N. Reske. Abteilung Nuklearmedizin, Universität Ulm, Ulm, Germany.

Aim: For quantitative image reconstruction in positron emission tomography attenuation correction is mandatory. In case that no data are available for the calculation of the attenuation correction factors one can try to determine them from the emission data alone. However, it is not clear if the information content is sufficient to yield an adequate attenuation correction together with a satisfactory activity distribution. Aim of the study is to develop such a reconstruction algorithm for PET emission data.

Materials and Methods: A mathematical thorax phantom including the patient bed (activity ratios for soft tissue, lungs, tumours, bones, trachea were 1, 0.375, 4, 1.5 and 0, respectively and for attenuation coefficients 0.095, 0.02, 0.095, 0.14 and 0.0) served to generate noisy realizations (Poisson distribution). The log likelihood distribution for the phantom was determined depending on the choice of attenuation and activity pixel values to measure the crosstalk between both. In addition an iterative image reconstruction (one-dimensional Newton-like algorithm with a maximum likelihood estimator), which simultaneously reconstructs the images of the activity distribution and the attenuation coefficients is used to demonstrate the dependence of the results on the start images and the regularization. Therefore, additional information is included using a k-means cluster analysis. Results: For a change of the log likelihood in the range of statistical noise, the associated change in the activity value of a structure is between 6-263%. When starting the iteration with the true activity and attenuation images, the algorithm remains in the correct maximum. However, when using a median root prior the algorithm reaches a false local maximum. This demonstrates the need for a regularization, which does not implement an interaction between different regions, e.g., cluster analysis.

Conclusion: Taking into account the attenuation information in the emission data improves the performance of image reconstruction with respect to log likelihood and with respect to the bias of the activities, however, the reconstruction still is not quantitative. Also, it is not possible to choose the best maximum on the basis of the log likelihood when a regularization is used, because the coupling between different structures mediated by the (smoothing) regular-ization prevents an adequate solution due to crosstalk. Implementation of cluster analysis yields a good improvement for large structures, however, it shows negative effects at the margins, if such pixels were assigned to the wrong cluster.

Development of An Affordable High-Resolution Transformable PET Camera

W.H. Wong, J. Uribe, H. Li, H. Baghaei, Y. Wang, Y. Liu, T. Xing, R. Farrell. University of Texas M.D. Anderson Cancer Center, Houston, USA.

An affordable high-resolution PET camera is being developed. This PET is designed to have an ultrahigh image resolution (2.2-2.6 mm) compared with current clinical PET (4.5 mm) and a transformable configuration including: (a) a high-sensitivity brain/animal mode with 40-cm transaxial field of view (TFOV) and 21-cm axial field of view (AFOV), (b) a whole-body tumor localization/staging mode with a 60-cm TFOV and 13-cm AFOV, (c) a high-sensitivity breast mode with 40-cmTFOV and 21 AFOV, and (d) an extra large radiation treatment planning mode with 80-cm TFOV and 13-cm AFOV. The production cost would be less than that of a typical commercial PET. The dedicated breast mode has 13-26 times higher positron-detection sensitivity than regular PETs, and an image resolution of 2.2 mm, for early detection of small breast tumors and multi-lesion diseases. For brain imaging, the brain mode has an image resolution of 2.2 mm, a 4x higher detection sensitivity with a extra large 21-cm AFOV for concurrent imaging of the brain and carotid arteries (for obtaining arterial input function in the image enabled by the high resolution). The PET may improve the accuracy of cancer diagnosis and research by (a) detecting early/small tumors as small as 2-3 mm, (b) determining the response of cancer to treatment earlier, (c) quantifying more accurately the functions of tumors, (d) facilitating quantitative tracer-kinetic modeling for cancer research, and (e) achieving 1-2 minute fast breast exams to facilitate breast screening for high risk young women. This system will use (a) an ultrahigh resolution, lower-cost photomultiplier-quadrant-sharing detector design, (b) a pileup-event-recovery electronics (reducing image artifacts) developed for the high resolution detectors, (c) a new transformable design that eliminates gaps between detector modules, (d) a new position-sensitive detector manufacturing method that reduces cost and improves resolution, (e) a new reprogrammable coincidence electronics to serve the transformable modular design and to achieve simultaneous cardiac and breath gating to realize high-resolution imaging for the lung and heart, and (f) a new photomultiplier tuning method. A scaled-down prototype PET has been developed to demonstrate (a) the highresolution detector concept, and (b) the theoretical validity and engineering feasibility of the transformable PET concept. Construction of this full-size PET, would allow performance of clinical tests to test the multi-functionality of a transformable PET, the usefulness of dedicated small PETs for brain, head and neck, spinal cord and breast imaging, and the usefulness of ultrahigh resolution PET imaging.

Is SUV an Accurate Marker of Treatment Response for Sarcoidosis When Using Wholebody FDG PET?

L. Rahman (1), A. Al-Nahhas (1), R.K. Coker (2), M. Myers (1). (1) Department of Nuclear Medicine, Hammersmith Hospital, London, UK, (2) Faculty of Medicine, Imperial College, London, UK.

Objective: SUV is an established method of quantitation for clinical PET studies. However, several studies have indicated the limitations of SUV due to its dependence on factors such as blood glucose, body weight distribution and region of interest placement. FDG PET is a useful tool for highlighting lymph nodes with sarcoid involvement although some nodes may be small and close to the lung border. The objective of this study was to evaluate the accuracy of SUV's measured pre and post treatment on wholebody PET scans to assess treatment response. The effects on SUV from variations in lymph node size and various acquisition and reconstruction parameters are assessed.

Methods: A typical range of affected lymph node size, placement and SUV normalised to body weight was determined from 6 clinical PET scans on patients suffering from sarcoidosis. The variation in partial volume effects and recovery losses due to object size was assessed using phantom simulations. The effects of techniques such as 2D acquisition and transmission image segmentation were assessed using clinical data and phantom simulations. Results: Maximum SUV value was used to remove ROI dependency. A significant error in maximum SUV value was noted for lymph nodes less than 2cm3. The use of image segmentation for transmission images can affect lymph node SUV's in close proximity to lungs. Conclusion: For patients where the scan protocol has been closely matched, SUV used as a relative measure pre and post treatment can identify changes in FDG uptake. Absolute measurement of SUV for lymph nodes less than 2cm3 should be avoided and transmission image segmentation should be used with care for SUV measurement near lung boundaries.

Validation of uniformity correction in SPECT

S. Ekberg. Department of Nuclear Medicine, University Hospital, Linkoping, Sweden.

The reconstruction algorithm in SPECT magnifies the nonuniformities from the planar data to the reconstructed data. Thus it is of great importance that the correction for non-uniformity works correctly. Usually one uniformity matrix is collected for each energy and collimator. The clinical patient acquisition may, however, be performed with different magnification, pan, rotation direction and patient positioning. All these possibilities together are a challenge for the programmer. There are several possibilities to make program errors, in particular, if there is more than one computer software involved in the acquisition, storing, correction and reconstruction of the collected data. The aim of this work is to present a method for validating uniformity correction programs and to present results from 3 gamma camera-computer systems. Methods: Seven coins (22 mm diameter, 1.5 mm thickness), were mounted with adhesive tape directly on the surface of the collimator in a diagonal pattern about 5 cm apart. A uniformity matrix was collected from a flood source. Several SPECT acquisitions were performed on a cylindrical phantom with different combinations of zoom factors, pan, rotation directions and patient positioning parameters. The coins were mounted on the collimator throughout all the acquisitions. The appearance of distinct ring artefacts in the transaxial images was used as measure of an insufficient uniformity correction. Three different gamma camera - computer systems were tested (A,B,C). One of the systems was a mix from two different company's (C) Results: The coins made a non-uniformity of about 40-50% in the uniformity and planar data. One of the three systems (A) performed the uniformity correction correctly. The second gamma camera system (B) failed in correcting data for one acquisition combination. In the mixed system (C) several faulty uniformity corrections were detected.

Conclusion: A simple test method was developed for validation of uniformity correction programs for gamma cameras in different acquisition set-ups and revealed program errors in two gamma cameras systems of three investigated.

Factors affecting recovery coefficients in PET

K. Knesaurek, J. Machac, B.R. Krynyckyi, O.D. Almeida. The Mount Sinai Medical Center, New York NY, USA.

Objectives: To investigate the dependency of the recovery coefficient (RC) utilizing a GE Advance PET system on the following factors: geometry, region-of-interest (ROI), maximum vs. average pixel value in the ROI, surrounding material, reconstruction method and isotope (18F vs. 82Rb). Methods: To derive the RC for spherical lesions, 6 spheres ranging from 1.1 to 3.2 cm were filled with 129.5 kBq/cc of 18F. To derive the RC for thin layers, a wedge phantom 29 cm long with a thickness ranging from 0 to 3.0 cm, was filled with 318.2 kBq/cc of 18F, and 125.8 kBq/cc of 82Rb, respectively. In calculating the RC, different ROIs and maximum and average values within the ROIs were used. RCs were measured for the phantom placed in air and in water. Reconstruction methods consisted of FBP (Hanning 13 (H13) and Hanning 16 (H16) filters), and OS-EM (IRMAC) for the phantom in air and in water. Results: Varying ROI size/position had no effect on RC using maximal pixel values and a 20% effect using average pixel values. For the wedge phantom with a thickness (T) <2 cm, RC (in water) = 0.55*T(cm)+0.11 and RC (in air) =0.53*T(cm)-0.03. For spheres with a diameter (D) <3 cm, RC (in water) =0.37*D(cm)-0.147. Different 2D reconstruction methods and isotopes used had relatively small effects on RC. Conclusion: The RC depends on geometry, ROI, whether maximum or average values were used, and the surrounding material. Dependency on background activity and 3D reconstruction methods needs further investigation.

Animal SPECT using Multi-Pinhole Collimation

N.U. Schramm (1), U. Engeland (2), G. Ebel (2), T. Schurrat (3), M. Behe (3), T.M. Behr (3). (1) ZEL, Research Center Juelich, Germany, (2) Scivis GmbH, Goettingen, Germany, (3) Dept. Nuclear Medicine, University of Marburg, Germany.

Aim: High-resolution pinhole SPECT can be very useful in tracer development and pre-clini-cal research where new radio pharmaceuticals have to be tested in small animal studies. However, conventional pinhole systems usually suffer from a poor sensitivity due to the inferior geometric efficiency of the high-resolution collimator. In order to increase the sensitivity without degrading spatial resolution we are studying the utilization of multi-pinhole collima-tion for animal SPECT imaging. Our approach is to equip a commercial gamma camera with a dedicated multi-pinhole collimator for high-resolution and high-sensitivity imaging of mice and rats.

Materials & Methods: Multi-pinhole tomography is an extension of conventional single-pin-hole tomography to more than one pinhole per collimator (typically 7 to 15). The pinholes are arranged in way that each pinhole of the multi-pinhole aperture only views a certain part of the object with all pinholes together covering the whole field of view (FOV). To accomplish this the pinhole axes have to be tilted in the axial and the transaxial direction. In contrary to single-pinhole tomography this multi-hole configuration allows the imaging of a non-spherical FOV which can be very useful in whole-body imaging of small animals. Another important feature of multi-pinhole imaging is that projections through different pinholes may partially overlap on the detector resulting in a more efficient coverage of the detector and thus, leading to a considerable increase in system sensitivity.

Our custom built collimator is based on a conventional collimator frame and consists of a lead shielding and an exchangeable multi-pinhole aperture made of tungsten. The conical pinholes have a diameter between 1 and 1.5mm and an opening angle of about 60°. Image reconstruction is carried out by an iterative algorithm which takes into account the spatially dependent point spread function of the multi-pinhole detector. This PSF is derived from the calculated sensitivity and the system resolution of a single pinhole. The reconstruction also corrects for the attenuation of radiation within the object assuming an uniform attenuation medium. The effective attenuation coefficient may be measured in water while the object contour is estimated from measured Compton projections.

Results & Conclusion: First planar images and tomographical phantom studies are very encouraging, showing the feasibility and the high potential of multi-pinhole imaging. These studies suggest a reconstructed resolution round 2.5mm and a system sensitivity of up to 600cps/MBq depending on the imaging distance and the aperture used.

A phantom study of the effects of acquisition and reconstruction parameters on measured myocardial wall thickness and cavity size.

D.O. Hall, F.V. Zananiri. Medical Physics Department, Bristol Royal Infirmary, Bristol, UK..

Aim: To evaluate the effects of acquisition zoom, acquired counts, filter, and frames per cardiac cycle on measured regional myocardial wall thickness and cavity diameter in Tc99m myocardial perfusion SPECT.

Materials and methods: A myocardial phantom, consisting of two non-concentric cylinders, was filled with 60MBq Tc99m, placed in a thorax phantom, and imaged on an SMV DST-XLi dual headed gamma camera fitted with a LEHR collimator. The phantom cylinder was 90mm diameter, interior diameter 45mm, with the internal cylinder placed off-centre so that the widest wall thickness is 32mm, and the narrowest 13mm.

We acquired 16 angles (32 views), 5 and 20s per angle, 8 and 16 frames per cycle, and zoom 1.14 and 1.33. The acquisition times were designed to give relatively high and low counts in the myocardium compared with typical clinical studies. The zooms gave pixel sizes of 7.89mm ad 6.77mm respectively. The images were reconstructed on an SMV-GE Vision computer with a Metz filter (order 8, cut-off 0.4 cycles/pixel) and a Butterworth filter (order 5, cut-off 0.3 cycles/pixel).

On a central slice at a single time period, we drew profiles two pixels wide across a diameter through the internal and external cylinders, i.e. through the thickest and thinnest parts of the phantom wall. We fitted a smooth curve to the profiles, and recorded the peak and half-maxima of each wall. We calculated the FWHM of each wall, the cavity diameter from the distance between internal half-maxima, and phantom diameter from external half-maxima. Results: The cavity dimension (45mm) was underestimated (mean 35(SD8). The thicker wall thickness was underestimated (24(5) mm vs 32mm), and the thinner wall was slightly overestimated (16(3) vs 13mm).

Changing zoom from 1.14 to 1.33 changed cavity by 3.1(sem1.6) mm, Butterworth rather than Metz filtration produced a change of -2.1(1.7)mm. Changing from 16 to 8 cycles and from high to low counts produced changes of 1.1(1.7)mm and 1.0(1.8)mm. Changing zoom from 1.14 to 1.33 changed thin wall by -2.6(1.1) mm and thick wall -2.9(2.3)mm; Butterworth rather than Metz filtration changed thin wall by 1.5(1.3)mm and thick wall by 2.0(2.4)mm.

Conclusion: The largest effect on measured cavity dimensions and wall thickness, and hence calculated myocardial volume, is the choice of cut-off, followed by acquisition zoom and filtration.

A comparison of Resolution loss and Geometrical distortions in different detector's configurations

M. De Marco (1), S. Maggi (1), B. Rossi (2). (1) Department of Medical Physics of Umberto I Hospital of Ancona, Ancona, Italy, (2) Department of Nuclear Medicine of Umberto I Hospital of Ancona, Ancona, Italy.

Aim: The analysis of perfusion myocardial Single Photon Emission Tomography (SPET) requires a reproducible method which gives a correct spatial individuation of the lesion. To better image the cardiac district and to reduce the contribution of the scatter due to the patient's left arm, the modern gamma cameras with a variable angle system, are be able to configure the detectors at the 76°, 90° and 180° locations. These geometrical configurations, associated with a transversal motion of the gantry during the SPET acquisition, give rise to a Non Circular (NC) motion of the system which permit a better contouring of the patient profile during a tomographic acquisition, but they may induce critical geometrical distortions. In this work the authors have evaluated the contrast and the system's resolution analysing the variations of the Full Width at Half Maximum (FWHM) of three linear sources in the different detectors' configurations. They have also investigated the geometrical distortions introduced in a cold lesion using these particular scans and their implications in a clinical routine. Material and Methods: To evaluate the contrast variations it has been used a typical Jaszczak phantom, consisting of six cold spherical objects of different size in a water filled acrylic cylinder. The camera was set up as in a normal cardiac SPET acquisition, and the phantom was positioned directly on the patient handling system. This condition may produce a light increase in the scatter component that is just like happens in the clinical use. The phantom has been imaged using the step&shoot mode, angular step of 3°, collecting at least 900,000 total counts in each image of 256*256 pixels matrix size. The images have been reconstructed using the filtered back projection technique with a ramp filter (cut off: Nyquist frequency). To evaluate the system's Line Spread Function (LSF), it has been used the typical NEMA phantom consisting of three axial line sources in a water filled acrylic cylinder. It has been imaged by using the same procedure described above, collecting 200,000 counts in each image.

Results: The contrast variation versus the objects' size has been valuated using an image of the Jaszczak phantom with the cold lesions, and the statistical noise using an uniform image. The next table shows the results: the NC acquisitions give rise to a general contrast's increase particularly evident in the 90° detector's configuration for the objects labelled #5 and #6. The noise may be considered constant in the different acquisitions.

Detector's Contrast Noise

configurations 1_2_3_4_5_6_

180 NC Orbit 88,6 79,6 51,2 33,8 22,9 — 5,5

180 C Orbit_85,9 73,7 48,0 33,8 18,7 — 5,8

90 NC Orbit 100,0 91,6 25,3 —_5,3 6,3 5,1

90 C Orbit_99,0 80,8 21,2 — — — 6,6

76 NC Orbit 100,0 98,3 37,6 7,7 18,8 6,0 5,9

Improvement of quantitative activity and image distortion in Tl-201 myocardial SPECT using scatter and attenuation corrections

A. Kojima (1), S. Tomiguchi (1), N. Katsuda (1), M. Matsumoto (1), Y. Yamashita (1), N. Motomura (2). (1) Kumamoto University, Kumamoto, Japan, (2) Toshiba Medical Engineering Laboratory, Tochigi, Japan.

Improvement of quantitative activity and image distortion in Tl-201 myocardial SPECT using scatter and attenuation corrections

Aim: Scatter and attenuation in the body cause significant distortions in myocardial SPECT images and limit quantitative measurement of absolute radioactivity. The aim of this study was to investigate how both scatter and attenuation corrections can quantitatively improve SPECT values and image distortions when extracardiac activity and body size are changed in Tl-201 myocardial SPECT study using a sophisticated phantom.

Materials and Methods: In this study, we employed a dual-head gamma camera SPECT system and an anthropomorphic thorax phantom with a cardic insert. Attenuation correction (AC) using an asymmetric fan-beam collimator and Tc-99m external source specially designed for the SPECT system and scatter correction (SC) by the triple energy window (TEW) method was performed. ECT projection data were acquired for a normal cardiac insert and a cardiac insert with a posterior defect and an extracardiac activity (liver). Each cardiac insert was placed in the thorax phantom with two different body sizes: a thick chest thickness (AT1) and a thin chest thickness (AT2). Four ECT image reconstructions were performed for each study: without both SC and AC, with SC and without AC, without SC and with AC, and with both SC and AC.

Results: The quantitative SPECT value and image distortion of myocardial polar maps were measured for each study. For the attenuation AT1, polar maps without AC generated moderate counts reduction by up to 30% in the inferior regions, but for the attenuation AT2 great apparent defect was created with reduced intensity by up to 50% within the range from the lateral-to the inferior-wall without AC. However, AC could improve these distortions by up to 20%. SC made the posterior defect clear for the increased counts from the liver activity. SC and AC generate more uniform polar maps for all the studies.

Conclusion: Both scatter and attenuation corrections can improve quantitative SPECT value and image distortion in Tl-201 myocardial SPECT study.

The system's resolution has been evaluated using the NEMA phantom. Comparing the data obtained we can see that the NC acquisitions presents an increasing of the system's resolution greater than 10% in horizontal direction. This feature is not associated with an analogous result for the vertical direction causing an erroneous representation of the lateral point that appears as an oval foggy spot.

Conclusion: The study has demonstrated an enhancement of contrast in tomographic acquisitions based on a Non Circular orbit in comparison with the Circular ones; this feature associated with a constant noise level in the two scans, makes the NC acquisitions helpful in resolving the smaller objects. We have also compared the results obtained using different detectors' configurations finding a contrast's increase more than +10% for the configuration at 76° rather than 180°. Such results have been obtained from the FWHM analysis of the linear sources. On the other side the acquisitions obtained with this detector's configuration induce an underestimation of the phantom's lower part, due to the reduced gantry's degrees of rotation. This fact can induce a wrong individuation of hypoperfusion defects localized in the cardiac back basal wall during a myocardial SPET.

The Improvment of Radiation Synovectomy of the Knee using Iterative Reconstruction and Image Fusion

J.I. Vuorela (1), T. Kauppinen (2), T. Sokka (3). (1) Department of Nuclear Medicine. Central Finland Central Hospital, Jyvaskyla, Finland, (2) Division of Nuclear Medicine. Helsinki University Central Hospital,Helsinki, Finland., (3) Department of Medicine. Central Finland Central Hospital, Jyvaskyla, Finland.

Aim: Treatment of chronic synovitis using radiation synoventomy aims to control the inflammatory process that causes stiffness, pain and severe structural damage to the joint. SPET study indicates that the most of the injected radiochemical localise within the injected joint cavity. Filtered back-projection (FBP) used in SPET has lead to noisy images with apparent streak artefacts. It is possible to improve the image quality by using an ordered subsets expectation maximization (OS-EM) iterative reconstruction technique. Image fusion with co-registered MR image was performed in order to correlate morphological information with the image data obtained by SPET. The aim of this work was to improve the quality of SPET images and fuse them to MR images aiming to get better result from synovectomy of the knee.

Methods: The patient studies were performed using six patients with rheumatoid arthritis. The rheumatoid knee joints were treated with intra-articular 166Holmium-ferric hydroxide macroaggregates (166Ho-FHMA) injections. SPET images were acquired using gamma energy of holmium (80 keV) with on average 9.8 Mcounts count statistics. The treatment dose was 0.9-1.0 GBq of 166Ho-FHMA. MRI (T1-weighted, fat-suppressed 3D-images with DTPA-enhanced images) were also performed. Pannus synovial hypertrophy and joint fluid is easily identified from these images. These images were used as a reference to the effect of the syn-ovectomy. Automatic registration was performed using maximisation of mutual information algorithm, where SEPT images were fused to MR images. In this registering technique the statistical dependence between the image intensities of corresponding voxels in both image sets is defined and it is assumed to be maximal if the images are geometrically aligned. Result: This imaging method shows clearly the effect of the therapy. It was noticed that FBP gives the approximation of activity distribution with noise and harmful streak artefacts. OS-EM increased the contrast of the image and improved the separation between the different regions. MR reference images were acquired because they represent the anatomical distribution of the inflamed synovium volume. The inflamed synovium was seen bright in T1-weight-ed Gd-DTPA images. Also the joint fluid can be seen.

Conclusions: Iterative reconstruction algorithm improves the results of SPET knee imaging, especially when SPET images were fused to the MR images. Iterative reconstruction algorithm is recommended for radiation synovectomy of the knee in clinical situation.

Large hole collimator (CACAO) a possible bright future for SPECT

C. Jeanguillaume (1,2), M. Quartuccio (2), A. Douiri (2), S. Begot (3), H. Rakotonirina (1), J.J. lejeune (1), P. Jallet (1). (1) CHU Angers Hopital Larrey 49033 ANGERS FRANCE, (2) Laboratoire de physique des solides Faculté des sciences 91405 ORSAY FRANCE, (3) IUT Chateauroux 36000 CHATEAUROUX FRANCE.

Several attempts were made in the past to replace the conventional collimator by coded aperture, even coded aperture in motion. Most of these works stuck to the small aperture principle. Only the work of Keyes changed dramatically the shape and the dimension of the collimator holes. The rotating motion of the collimator compensated the large dimension of the slat. The CACAO project shared with the work of Keyes the same principle. The CACAO project use large rectangular holes in the collimator and a linear scanning motion added to the gantry. This project is capable of dramatically increase the sensitivity of SPECT system (by a factor 100 or more). Moreover the mathematical model, which takes a full account of all the geometry of the acquisition (e.g. every dimensions of the collimator hole, and the source to collima-tor distance) matches the physical reality with an accuracy never attained to date (2,3). Needless to say the impulse function is homogeneous in all the field of view. Information theory demonstrated theoretically the potential benefit of the CACAO project (3). Recent improvements of our reconstruction algorithm greatly increase the quality of our computed images. A splines interpolation made the rotation more accurate and a pseudo wiener - multichannel optimisation boosted the deconvolution stage. To fully examine the potential benefit of the CACAO project with pixelated detector, we simulated the reconstruction of tomograph-ic images with a supposedly intrinsic resolution of the detector of 1.5mm. Our simulations confirm that thin hole conventional collimator is incapable of benefit from this improvement of resolution without impairing too much, the sensitivity of the system. At the opposite the CACAO project (at least in these simulations) exhibit an important improvement of the resolution of the images. Calculation of the signal to noise ratio in both simulation (CACAO and conventional) confirmed the difference. The first 3D computerised simulations were recently tried. The comparison of the CACAO images and the conventional ones emphasised the superiority of the CACAO approach. It is then argued that CACAO would improve in a near future the quality of SPECT images. The emergence of solid state detector with pixel size smaller than the millimetre will sure benefit from this type of collimation. 1- Keyes Phys Med Biol 1975;20:489-93 2- C. Jeanguillaume. 14th Annual IEEE EMBS Conf, Paris (France), 29 octobre/1 novembre 1992, part 5 of 7 pp. 1813-1815. 3- High sensitivity gamma camera system US Patent N° 5 448 073 September 05, 1995. 4- C. Jeanguillaume, et al. R.B.M. 1996;18:(7) 198-206 and 207-215

I-123 IBZM-SPECT: improved acquisition protocol with HR-collima-tor

D. Sandrock, V. Ivancevic, U. Dopichaj-Menge, D. Gruber, D.L. Munz. Clinic for Nuclear Medicine, University Hospital Charité, Humboldt University of Berlin, Berlin, Germany.

Aim: Aim of this study was to evaluate the impact of different acquisition and reconstruction protocols on the quality of SPECT diagnostics with I-123 IBZM in patients with diseases of the dopaminergic system.

Material and Methods: Overall, 30 patients (19 men, 11 women, aged 22 - 80 years) were studied with SPECT after i.v. injection of 5 mCi (185 MBq) I-123 IBZM. Acquisition was performed 60 min p.i. (protocol A) using a medium energy collimator, a 64 x 64 matrix, 64 projections, step and shoot technique, 5.6° and 20 seconds per step with a MultiSPECT2 double-head gamma camera (Siemens). Immediately afterwards, a second acquisition (protocol B, 90 min p.i.) using a high resolution collimator, a 128 x 128 matrix, 60 projections, step and shoot technique, 3° and 30 seconds per step was performed. The reconstruction was done in filtered backprojection technique and a Butterworth filter of order 7, in protocol Ausing a cutoff of 0.5 and in protocol B of 0.4. Finally, the net count ratios of the basal ganglia to the frontal lobe(s) were calculated and compared with the clinical diagnosis. Results: The visual analysis yielded - as expected -a better image quality for protocol B (concordant impression of 3 independent observers) with more accurate delineation of the basal ganglia. The count ratios with protocol B were (mean) 0.19 higher (equivalent to 13 %) than with protocol A. In the group of patients with count ratios > 1.55 there was the highest (and significant) difference between protocols A and B with (mean count ratio difference) 0.32 (equivalent to 20 %). Protocol B also allowed a better differentiation between patients clinically staged normal and abnormal. In patients with unilateral disease, this difference between normal and abnormal was more prominent (in comparison to the contralateral side as well as compared to the reference value [1.5]). The comparison of the count ratios with the clinical data revealed 7 patients with borderline results with protocol A and 3 patients with protocol B. These could not properly staged as normal or abnormal.

Conclusion: The acquisition protocol using a HR collimator and a 128 x 128 matrix in I-123 IBZM-SPECT leads to a more valid determination of the dopamine D2 receptor status.

Dynamic Imaging with a Gamacamera-PET system: a feasibility study

G. Dobrozemsky (1), M. Mitterhauser (2,3), H. Bergmann (1,4), K. Kletter (2). (1) Department of Biomedical Engineering and Physics of the Vienna General Hospital, Vienna University, Vienna, Austria, (2) Department of Nuclear Medicine of the Vienna General Hospital, Vienna University, Vienna, Austria, (3) Anstaltsapotheke of the Vienna General Hospital, Vienna, Austria, (4) Ludwig Boltzmann Institute for Nuclear Medicine, Vienna, Austria.

Aim: Multiheaded gamma cameras with coincidence detection capabilities (GC-PET) are less suited to perform dynamic imaging than dedicated PET systems, not only due to design or software limitations, but also due to countrate statistics. (R)-[O-methyl-11C]metomidate (MTO) is a tracer designed for the identification of adrenocortical lesions which targets enzyme P450n?. The information obtained by static imaging of this tracer is often insufficient to decide uptake in incidentalomas of the adrenal cortex from gastric uptake-which has a significantly different dynamic behavior in the first half hour of uptake. So, we wanted to investigate the possibilities of dynamic imaging on a GC-PET system with slip-ring gantry. Materials and Methods: We constructed a phantom with geometric properties similar to that of a mid-abdominal lesion. The adrenal cortex was simulated by an ion-exchange cartridge (Alltech Maxiclean Alumina-N) which was placed inside a body phantom normally used for QC purposes. The phantom's main volume was filled with activity (45MBq in some 9l) to simulate background activity. Two cylinders simulating the arms were added on the phantom's sides to simulate attenuation as encountered in patient imaging. A small volume of known activity (0.7MBq in 2ml) was added as a reference source. A dynamic uptake pattern was achieved by employing a closed loop system in which the activity reservoir (0.4MBq in 60ml) was circulated through the ion exchange column by a pump which circulated the entire volume about once in 10min. To keep the ion-exchange column (pretested extracting efficiency >99%) from trapping all the activity in a single pass, the system was designed with a bypass so only a third of the fluid passed the ion-exchange column resulting in a typical com-partmental uptake curve. Data acquisition was performed with 3 minutes per rotation and each single complete rotation was reconstructed separately. The same measurements were also performed on a dedicated PET system for reference.

Results: After normalization using the reference source, the GC-PET system showed results corresponding (within margin of error) to those obtained by the dedicated PET system. While the time resolution of the uptake curves does not permit to derive accurate kinetic parameters, it is sufficient to distinguish between gastrointestinal uptake and adrenocortical incidentalomas. Conclusion: GC-PET systems with slip-ring gantry and suitable reconstruction software can be used to perform dynamic PET imaging such as identification of incidentalomas of the adrenal cortex with MTO down to frame rates in the minute scale.

Effects of Varying Degrees of Overlap in Whole-Body Coincidence-Detection Imaging:Comparison Of Image Resolution & System Sensitivity at Overlap (Knit) Locations in Whole-Body Images

M.O. Afriyie, P. V. Pugliese, F. Leveque, C. Love, M.B. Tomas, J. N. Rini, C. J. Palestro. Division of Nuclear Medicine of Long Island Jewish Medical Center, New Hyde Park, New York USA.

Aim: Whole-Body Coincidence-Detection images are acquired using overlap acquisition protocols. The recommended 50% overlap prolongs imaging time, which may be up to 2 hours for a single whole body study. Less overlap would shorten study duration. The effects of a smaller overlap on system sensitivity and resolution, particularly at the margins of the field of view where the "knitting" takes place are not well known. The objective of this investigation was to determine the effects of varying degrees of overlap on sensitivity and resolution at the knitting sites.

Methods: A polycarbonate & glass cylindrical tube (Data Spectrum) 45.7 cm in length and 1.2 mm diameter was filled with 1 mCi of 18F-FDG. A single acquisition, with no overlap (0%) was performed, and served as the control. Studies consisting of 2 acquisitions were performed using 30%, 40%, and 50% overlap. Data were reconstructed into 3D images, and the images knitted together. For each acquisition, using line profiles and regions of interest, FWHM, FWTM, & ROI counts were determined at various points along the tube, including knit locations.

Results: FWHM results obtained from 30%, 40%, and 50% overlap acquisitions showed no differences. FWTM values, however, showed minimal differences. The 0% overlap acquisition, showed 19.8 & 15% deterioration in FWHM & FWTM respectively, at the margins of the field. Sensitivity-wise, normalized to 50% overlap image as 100%, we obtained 55%, 60%, and 80% sensitivity index for 0%, 30% & 40% overlap respectively (Table). Conclusion: These data demonstrate that, although 50% overlap prolongs imaging time, it remains the best choice for imaging based on resolution & sensitivity. Lesser degrees of overlap, such as 30% and 40%, should be reserved for those patients whose condition requires the shortest study time possible. If a single spin, 0% overlap must be performed, the area of interest must be positioned as close to the center of the field as possible to minimize data loss.

Resolution and Sensitivity vs. Overlap

Overlap (%) FWHM (mm) FWTM (mm) Sensitivity (%) normalized _to 50% overlap_

0 '4.8 26 55

30 '0 '7.5 60

40 '0 '9.7 80

50 9.9 '9.2 '00

Comparison of Br-76-PET and In-111-SPECT with a coincidence gamma camera system

M. Lubberink (1,4), M. Sandstrom (1), C. Widstrom (1), K. Kairemo (2), V. Tolmachev (3). (1) Department of Hospital Physics, Uppsala University Hospital, (2) Department of Nuclear Medicine, Uppsala University Hospital, (3) Section of Biomedical Radiation Sciences, Uppsala University, (4) Uppsala University PET Centre, Uppsala, Sweden.

AIM: Gamma camera systems with coincidence capabilities are often installed at hospitals without an on-site cyclotron for production of PET radionuclides. The availability of positron-emitting radionuclides with longer half-lives than 18F could thus considerably expand the possibilities of PET imaging with these systems. Bromine-76, a positron-emitting nuclide with a radioactive half-life of 16.2 h, has been suggested for e.g. measurement of antibody kinetics with PET. 111In-SPECT has been used for similar purposes. The aim of this work was to compare the performance of SPECT with 111In to the performance of coincidence imaging with 76Br on the same system.

MATERIALS AND METHODS: All measurements were made with a GE Millenium VG dual-headed system with 5/8" detectors and Hawkeye X-ray CT. Attenuation correction was done using the Hawkeye X-ray system. Medium energy and septa collimators were used for 111In and 76Br, respectively. Images were reconstructed by OSEM using the standard software and all standard settings. Scatter correction was not applied, and coincidence measurements were done both without and with acceptance of coincidences of scattered and unscattered photons for increased sensitivity. Spatial resolution, recovery, quantitative accuracy and image quality were studied. Radioactivity concentrations and imaging times were similar for both nuclides.

RESULTS: Spatial resolution for 76Br was 15 mm, 111In-SPECT resolution was appr. 2 cm. Assuming 100% recovery of radioactivity concentration in a 40 mm diameter hot sphere, recovery in a 22 mm sphere was 47% for 111In and 63% for 76Br, while recovery in a 10 mm sphere was 5% and 6%, respectively. The table below shows remnant correction errors in water, air and Teflon in a standard NEMA phantom for both nuclides.

'"In_76Br, peak/peak_76Br, peak/Compton

Water 2' % 34 % 42 %

Air 7 % '9 % '6 %

Teflon 2' % 32 % 5' %

DISCUSSION: Spatial resolution and recovery of coincidence imaging with 76Br were better than for 111In-SPECT but less optimal than for dedicated PET systems, partly because of the large filters applied in the standard settings of the system. Acceptance of coincidences of scattered and unscattered photons degrades image quality significantly. Scattered radiation and prompt gamma coincidences are a larger problem for 76Br than scatter is for 111In, and corrections are necessary for both nuclides to enable quantitative imaging.

Limitations of a coincidence gamma camera with x-ray based attenuation correction at patient studies with metal implantations

U. Jaeger, H.J. Adrian, U. Doerr. Department of Nuclear Medicine, Klinikum Stuttgart, Katharinenhospital, Stuttgart, Germany.

Aim: Using a coincidence gamma camera with xray-based attenuation correction ( e.q. GE Millennium Hawkeye) artifacts of the activitity concentration of 18F-FDG (AC) occur at patients with metal implantations. At the position of these metal implantations a increase of the AC up to a factor of 10 to the surrounding AC was observed. The reason and the quantitative results of these artifacts should be analyzed by use of special phantoms. Material and Methods: A phantom was produced, with a uniform background AC and different metal-cylinders with 6 diameters between 5 mm and 30 mm. To get the lower limit of the diameter a metal-pyramid of a basis diameter of 30 mm was used.

Results: The artifacts observed in the patient studies could be verified in the phantom studies. The quantitative evalution gave increases of the AC of a maxmium of up to 800% at diameters of 15 mm and above. The lower limit of the metal diameter for this artifacts was found at 5 mm.

Conclusion: At 18F-FDG -Patient studies where the surrounding AC of metal implantations is important for the clinical diagnosis it is important to use the non attenuation corrected data and the x-ray attenuation map to verify the true AC in this regions. Furthermore it is necessary to have a option in the application software, which allows the user to indicate regions with metal implantations and to apply a correction to avoid this artifacts.

Quantification of Organ Uptake in Whole-Body Coincidence Detection Images: How Reliable Is It?

M. O. Afriyie, P. O. Pugliese, G. G. Tronco, C. Love, M. B. Tomas, C. J. Palestro. Division of Nuclear Medicine of Long Island Jewish Medical Center, New Hyde Park, New York, USA.

Aim: A whole body Coincidence Detection image is created by knitting together a series of individually acquired and processed data sets, commonly referred to as "spins". Because of vastly different count densities in these individual acquisitions, it is difficult to use a single set of filter parameters to reconstruct the data sets with a consistent resolution. More often, a selected filter will be best for one data set, and another will be better for other data sets. Since every filter component manipulates data differently with respect to smoothing, noise addition, count density restrictions, we chose to investigate whether or not a selected filter, based on its properties, could change organ quantification results. We evaluated the application of a given filter with variable cut off frequencies and its effect on the 3 reconstructed data based on organ uptake ratios.

Methods: Patient imaging of the head, chest, and abdomen were studied. Using Butterworth Filter with cut-off frequency of 0.96, order of 6, the 3 data sets were reconstructed into 3D images and were knitted together to form whole-body images. The procedure was repeated using Butterworth filter and cut of frequencies of 0.86 & 0.76 respectively and order of 6; resulting in 3- 3D whole body image data sets. 3 prominent organs in the 3D image sets were selected as ROIs; brain, heart, & right kidney. Counts were obtained from each individual organ in each 3D image set and were recorded. Geometric mean was derived. Ratios of uptake, normalized to kidney uptake (lowest among the 3 ROIs) were calculated for organs in each individual image set.

Results: The results are presented in the table below.

Image set 3D Butterworth Cut off Frequency

Right kidney: Heart: Brain ratio

' 0.96 ' '.95 3.4

2 0.86 ' '.96 3.2

3 0.76 ' '.93 3.5

The table shows that there is no appreciable change in the ratios obtained by the various cut off frequencies. The 3 sets of data, irrespective of their individual treatment by the filters, maintained count density integrity, & therefore maintained the original count ratio in the raw data.

Conclusion: The data demonstrate that quantification of Coincidence Detection images is reliable, even if data are subjected to various processing formats. As long as the same filter with varying cut off frequencies is employed, ratios maintain their integrity and correctness.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition DOSIMETRY

Fluorine-18-Fluoroerythronitroimidazole Radiation Dosimetry in Cancer Studies

Efective dose to patients in Positron Emission Tomography studies

J.M. Marti-Climent, I. Peñuelas, M.J. Garcia-Velloso, J. Arbizu, L. Villar, M. Rodríguez-Fraile, J.A. Richter. Department of Nuclear Medicine. University Hospital. University of Navarra. Pamplona. Spain.

Aim: Positron emission tomography has become a common diagnostic tool in most European countries. Different procedures in each PET Center, due to administered activity to patient, impose variations in patient effective doses. The objective was to evaluate the collective effective dose due to radiopharmaceuticals used in our PET Center during the year 2001. Methods: A total of 1590 PET procedures were done; 55.9 % of the patients were male. Mean activity per radiopharmaceutical was 425, 136, 392, 414 and 621 MBq for 18FDG, 18FDOPA, 11C-Methyonine, H215O and 13NH3 respectively. A ECAT EXACT HR+ (CTI-Siemens) scanner was used. Literature values of normalized effective dose (mSv/MBq), following ICRP-60 recommendations, were used to evaluate effective dose. Detriment was also evaluated using the nominal probability coefficients of stochastic effects for general public. Results: 18FDG was the radiopharmaceutical most used in our center: 89.6% of procedures and 91.7% of administered activity. 18FDOPA and 11C-Methionine represented 3.4 and 4.2 percent of PET procedures respectively. According to the mean activity administered per each radiopharmaceutical, the effective dose per diagnostic study was:

Diagnostic Study_Radiopharmaceutical_Effective dose (mSv)

Oncological Whole Body "FDG 8.1

Miocardial Perfusion 13NH, 1.2

Coronary Flow Reserve 2 x 13NH, 2.4

Myocardial Viability 18FDG + 13NH, 9.3

Brain FDG Metabolism 18FDG 8.1

Brain Tumor (Recurrence) 18FDG + "C-Methionine 10.1

Dopaminergic System "FDOPA 2.7

Brain Perfusion H215O 0.4

Brain Perfusion (activation) 4 x H215O 1.6

Brain Perfusion (activation) 8 x H215O 3.2

Collective effective dose due to PET studies was 11.83 mSv*Person; 55.1 % corresponds to the male patient population. 18FDG, 18FDOPA and 11C-Methionine produced 97.4, 1.2 and 1.1 % of the collective effective dose.

Although the nominal probability coefficients of stochastic effects for general public are not of direct application to a patient population, PET studies in our Center during the year 2001 would have supposed the apparition of 0.59 fatal cancer cases and 0.89 stochastic effects. Conclusions: These results show that 18FDG has produced the highest effective dose per PET procedure (8.1 mSv). Effective dose due to Positron Emission Tomography studies is similar than those from other Nuclear Medicine studies.

T. Tolvanen (1), K. Lehtio (1), J. Kulmala (2), V. Oikonen (1), O. Eskola (3), J. Bergman (3), H. Minn (1). (1) Turku PET Centre, Turku University Central Hospital, (2) The Department of Oncology and Radiotherapy, Turku University Central Hospital, (3) Turku PET Centre, Radiopharmaceutical Chemistry Laboratory, Turku, Finland.

[18F]Fluoroerythronitromidazole, 4-[18F]Fluoro-2,3-dihydroxy-l-(2'-nitro-l'-imidazolyl)butane (FETNIM) is a new promising PET tracer for imaging tumor hypoxia. Poorly oxygenated cells are known to be relatively resistant to various forms of cancer therapy and detection of hypoxia in tumors is important for targeting treatment specifically to those cells. Aim of this study was to estimate the radiation dose to the patient caused by intravenous injection of 18F-FETNIM.

Materials & methods: Dynamic PET studies from twenty-seven patients with a histologically verified cancer were used for measuring residence times of 18F-FETNIM in liver, kidneys, spleen, lungs, pancreas, muscle, red bone marrow, brain and gastrointestinal tract with the GE Advance PET scanner (General Electric Medical Systems, Milwaukee, USA). Arterial plasma samples and voided urine samples were collected during and after the PET scanning and they were measured with cross-calibrated gamma counter (Wizard, Wallac-EG&G, Turku, Finland). The MIRD schema and MIRDOSE 3-software (Oak Ridge Associated Universities, Oak Ridge, Tennessee, USA) were used in calculating S-values for each source organ - target organ pair.

Results: According to urine samples 60 % of administered activity was cleared through the urinary pathway. Two different voiding schedules were considered, 2 hours and 4 hours after administration of 18F-FETNIM for radiation dose calculation. The critical organs with 4 hours voiding schedule were urinary bladder wall, kidneys and liver where dose equivalents were 0.127, 0.027and 0.024 mGy/MBq respectively. The other target organs received dose equivalent of 0.006 to 0.020 mGy/MBq. The effective dose was 0.015 mSv/MBq or 0.017 mSv/MBq leading up to 5.55 mSv or 7.03 mSv dose for the 370 MBq injection depending on the voiding protocol.

Conclusion: The effective dose from FETNIM PET study to a 70 kg patient is comparable to other related medical exposures. We recommend that patients are well-hydrated before administration and voiding is allowed within 2 hours from injection.

Dosimetry of repeated Y-90-SMT 487 (Octreother) therapy of somatostatin receptor expressing tumours using Y-90-bremsstrahlung and In-111-octreotide measurements

M. Lubberink (1), U. Garske (2), M. Sandstrom (1), C. Widstrom (1), H. Lundqvist (3), E. Maripuu (1), K. Oberg (4), K. Kairemo (2,3). (1) Uppsala University Hospital, Department of Hospital Physics, (2) Uppsala University Hospital, Department of Nuclear Medicine, (3) Uppsala University, Department of Oncology, Radiology and Clinical Immunology, (4) Uppsala University, Department of Medical Science, Uppsala, Sweden.

AIM: The aim of this study was to determine absorbed doses in nine patients with metastatic cancers expressing somatostatin receptors, undergoing repeated treatments with 90Y-SMT 487 (90Y-DOTA-D-Phe1-Tyr3-octreotide).

MATERIALS AND METHODS: Nine patients included in a clinical study by Novartis (Basel, Switzerland) received three repeated doses of 4.4 GBq of 90Y-SMT 487 (OctreoTher™, Mallinckrodt, Petten, The Netherlands) in six week intervals. Prior to the first therapy, 175 MBq of 111In-DTPA-D-Phe1-octreotide (Octreoscan®) was administered to all patients and whole-body anterior and posterior scans were made at 4, 24, 48 and 72 h p.i., as well as a SPECT at 24 h p.i.. At 72 h p.i. a transmission scan was made using a 57Co plane source. Bremsstrahlung whole-body scans were made at 2-4 h and 24 h after each treatment, using medium energy collimators and an energy window of 125% around 150 keV. ROIs were drawn in the geometrical mean image around organs of interest and visible tumours. Corresponding ROIs in the transmission image were used to calculate an attenuation correction factor for each tissue, using broad beam attenuation coefficients of 0.125 cm-1 for 57Co and experimentally determined attenuation coefficients for 111In and 90Y. Absorbed doses were calculated using the MIRD scheme.

RESULTS: Broad beam attenuation coefficients of 0.11 cm-1 and 0.095 cm-1 were found for 111In and 90Y, respectively. Preliminary results show kidney residence times ranging from 2.1 to 4.0 h, resulting in 90Y doses of approximately 6 mGy/MBq. It should be noted that all patients were also administered amino-acids at the time of the 90Y administration to limit absorbed dose to the kidneys, which was not done during the Octreoscan measurements. There was a large variation in tumour doses between different patients. For all patients that had received a second treatment at the time of writing, 90Y uptake to tumours decreased for the second treatment. CONCLUSION: Individual dose planning is highly motivated for patients receiving large amounts of 90Y because of large differences in kinetics between patients and the high absorbed doses involved. Bremsstrahlung measurements give a very crude estimate of absorbed doses during therapy, so other methods such as co-injection of 86Y-labelled octreotide for quantitative PET measurements could be considered. More detailed conclusions will be presented after the completion of all three treatments by all patients.

Biokinetics and dosimetry of 99mTc-HYNIC/EDDA-octreotide in tumour patients

W. Cholewinski (1), C. Decristoforo (2), S.J. Mather (3), E. Donnemiller (2), M. Gabriel (2), R. Moncayo (2). (1) Department of Nuclear Medicine, Medical University of Lublin, Lublin, Poland, (2) Department of Nuclear Medicine, Innsbruck University, Innsbruck, Austria, (3) Nuclear Medicine Research Laboratory, St.Bartholomews Hospital, London, UK.

Aim: Replacement of 111In for 99mTc for Somatostatin Receptor Scintigraphy could result in wider availbility higher image quality, but also reduced radiation dose. Recent experience with the new Somatostatin analogue 99mTc-EDDA/HYNIC-Tyr3 octreotide (HYNIC-TOC) showed similar or better tumour to organ ratios in comparison with 111In-DTPA-octreotide. The aim of this study was to obtain data about the radiation absorbed organ dose and biokinet-ics of this promising radiopharmaceutical in tumour patients

Materials and Methods: Whole body biodistribution and dosimetry was evaluated in 9 patients (3 carcinoid tumors, 4 thyroid carcinomas and 2 pancreatic cancers). Planar whole-body scans 0-1, 2-3, 4-6 and 18-24 h p.i. and SPECT imaging (3-5 h p.i.) were performed after injection of 300-350MBq 99mTc-HYNIC-TOC with a double head cammera (Elscint Helix). Tracer biodistribution was evaluated using whole body images and conjugated views. Regions of interest (ROI's) were manually drawn on whole body scintigrams over whole body, liver, spleen, kidney, chest, heart, bladder and tumour sites at different time points. Mono- and biexponential time-activity curves were fitted. For calculating self-S values for spherical tumours, the „Nodule Module" option in the MIRDOSE 3.1 Software was used. MIRDOSE 3.1 software was also used for dose calculations for all other organs, entering calculated residence times and selecting appropriate phantom model. The volumes of the tumour sites were evaluated by Region Growing Software (Nuclear Diagnostic) from SPECT slices. The biodistribution and kinetics of 99mTc- HYNIC-TOC in the source organs were used to calculate the residence times.

Results: Calculated absorbed doses were for spleen: 0,044 mGy/MBq, kidneys: 0,03 mGy/MBq, liver: 0,01 mGy/MBq, heart wall: 0,005 mGy/MBq and lungs 0,009 mGy/MBq. The total body dose was 0,0042 mGy/MBq. Maximum uptake in tumour expressed as %ID was observed at different time-points usually 0.5-4 hr post injection. Residence time ranging from 0.01 to 0.22 hr (mean 0.06h ± 0.06) and absorbed dose from 0,001 to 0,014 mGy/MBq (mean 0,004 ± 0,004 mGy/MBq).

Conclusion: In comparison with previously published data concerning 111In labelled somato-statin analogues 99mTc-EDDA/HYNIC-octreotide showed ten to twenty times lower absorbed doses to main organs. In combination with a superior image quality these results underline the advantages of 99mTc-HYNIC-TOC as possible replacement for 111In-DTPA-Octreotide. Biokinetic parameters of 99mTc-HYNIC-TOC in tumour sites seem to be similar to that observed in 111In-DOTATOC studies giving promising implication for internal therapy with 90Y-DOTATOC planning and follow-up.

How clinical factors affect exposure rates (versus time after administration) for iodine-131 treated thyroid carcinoma patients.

D. Papadimitriou (1), L. Oros (1), A. Perris (2), M. Molfetas (3), E. Efstathopoulos (4), S. Kottou (4). (1) Nuclear Medicine Dept, White Cross Hospital, Piraeus,Greece, (2) Radiology Dept., University of Athens, Aretaieion Hospital, Athens, Greece, (3) Medical Physics Dept, Evagelismos Hospital, Athens, Greece, (4) Med. Physics Dept., University of Athens, School of Medicine, Athens, Greece.

Introduction: This work tries to estimate the correlation between several clinical factors and the residual activity of I-131 in patient's body. A method is also proposed for a more simple estimation of this residual activity.

Materials and Method: The measurements took place in General Hospital ??White Cross??. Exposure rates at a distance of 1m from 45 patients with well-differentiated thyroid carcinoma were measured using an ionisation chamber filled with air. The measurements were taken 3, 24, 48 and 72 hours after administration of I-131 for ablation or treatment for distant metastasis. The administered activity ranged from 2220 to 5550 MBq. Patient's related clinical parameters as gender, weight, height, extent of surgery, tumour histology, thyroid uptake at 24h, TSH value, presence of metastasis were recorded. During patient's hospitalisation additional parameters as liquid consumed and emptying of the bowls were recorded. Correlations between exposure rates and all of the above parameters were calculated. Also, Patient's Exposure Rate Constants are calculated in relation with Patient's Body Mass Index (BMI). The calculation is based on the assumption that the administrated activity is distributed through patient's body after 3h, which is our reference exposure rate value. Results: Exposure rate 24h after administration, normalized to the administered activity (mR.h-1.MBq-1) is significantly correlated with water consumed (r=-0.47, p=0.02) and thyroid uptake values (r=0.45, p=0.008). Regression curves were generated for exposure rate versus time in relation to all clinical parameters mentioned above. An interesting founding of this analysis is that the mean residual I-131 24h after administration reaches 23% of the administered activity for uptake values ranging between 0-2% and 35% for uptake ranging between 210%. Also for low liquid consumption (mean 3L) the mean residual activity is 30% higher than for high liquid consumption (mean 6.5L). The presence of metastasis results in 25% higher residual activity at the end of the first 24h.

The exposure rate constant 1m from the patient's body is estimated to 0.2mR.h-1mCi-1 for underweight patients (BMI<21), 0.17mR.h-1mCi-1 for normal patients (21<BMI<27) and 0.135mR.h-1mCi-1 for overweight patients (BMI>27).

Conclusions: The main factors affecting the amount of residual activity are the liquid consumption and the thyroid uptake value. Also method for simple estimation of the residual activity is proposed. Good management of patients receiving iodine-131 treatment should attempt to maximize thyroid uptake while keeping the dose to other organs as low as possible.

Radiation exposure in imaging with <SUP>86</SUP>Y-DOTATOC

G.J. Förster (1), H. Reber (1), M. Engelbach (2), J. Brockmann (3), H.-G. Buchholz (1), P. Bartenstein (1). (1) Department of Nuclear Medicine, University-Hospital Mainz, (2) Department of Endocrinology, University-Hospital Mainz, (3) Institute of Nuclear Chemistry, University Mainz, Mainz, Germany.

Objectives: Radiolabeled somatostatin analogues are used for imaging and treatment of patients with neuroendocrine tumors. DOTATOC (DOTA-D-Phe'-Tyr3-octreotide) labelled with the positron emitter 86Y allows quantitative imaging of somatostatin positive tumors and dosimetry for a therapy with 90Y-DOTATOC. The aim of this study was to calculate dose estimations for this diagnostic procedure based on in vivo measurements of patients. Methods: Dynamic and static PET studies in 2D mode with 77-186 MBq 86Y-DOTATOC were performed in 3 patients with metastatic carcinoid tumors on a ECAT EXACT 922 scanner up to 48 h after injection. Images were reconstructed using transmission scans and filtered back projection. Serum and urinary activity were measured simultaneously. Based on the regional tissue uptake kinetics, residence times were calculated from the time activity curves and doses for the investigation were estimated based on the MIRD concept. Results: The serum und cumulative urine kinetics showed that 86Y-DOTATOC is eliminated fast of the vascular compartment with two exponential components: half life of 6.5 min (ca. 80% of injected activity) and 130 min. The highest absorbed doses were found in the kidneys, spleen and liver with a mean estimated dose (±SD) of 0.28±0.09, 0.22±0.17 and 0.13±0.02 mGy/MBq, respectively. The exposures based on this data result in an effective dose of 0.037±0.005 mSv/MBq.

Conclusion: For a supposed applicated activity of 200 MBq the exposures are 56.4 mSv for the kidneys, 44.4 mSv for the spleen and 25.6 mSv for the liver. The effective dose is 7.4 mSv. In comparison with published dosimetry data of the already established radiopharma-ceutical 111In-DTPA-octreotide, assessment of the radiation exposure of an investigation with 86Y-DOTATOC is in the same order of magnitude. This data justify the use of 86Y-DOTATOC in staging of somatostatin positive tumors and pretherapeutic dosimetry taking advantage of its high affinity to the somatostatin receptor and the superior imaging properties of PET.

Absorbed doses to urine bladder during radioiodine therapy to thyroid cancer patients: A clinical study using MIRDOSE3

A.S.M.S. Ahmed, M. Demir, C. Mete. Nuclear Medicine Department, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.

Aim: For most thyroid cancer treatments, patients are administered radioactive I-131 to ablate residual thyroid tissue and functional metastases from thyroid cancer. Most of the radioiodine is excreted through urinary tract in first few days. The object of the study was to calcualte the absorbed doses to urinary bladder by MIRDOSE3 (Medical internal radiation dose package program) at different voiding intervals for individuals.

Materials and Methods: 21 female thyroid cancer patients (age ranged from 40-60 years with a mean value 50) were selected for the study under four groups depending on given dose. The therapy doses ranged from 3700-7400MBq (100-200mCi) of I-131. The uptake of radioisotope was measured by a calibrated Eberline ESP-2 GM counter under special arrangement of each patient. Reading was taken at 1cm distance from three organs (Previously marked): thyroid, thigh, kidney. Urine sample was collected at 12 hrs interval for first 3 days and then 24 hrs. interval for the next 7 days. The individual biologic half life of excreted urine was calculated using individual effective half life that measured from individual urine sample. Absorbed doses for bladder were calculated for an adult female phantom using dynamic bladder model of MIRDOSE3 program at different voiding intervals.

Results: An average of 85% of total dose (for 4 grps.) passed through urinary tract within first three days of treatment with a biologic half life of (28.5±0.747) hr. The amount was 9% for the next 7 days with a biologic half life of (118.43±0.645) hr. The voiding interval shows great impact on total absorbed dose to bladder. The absorbed doses are summarized in the table below.

Group Ave. of total no. Ave. of total Bladder Residence Total

with dose activity passes activity passes voiding time (hr) absorbed

limit (mCi) urinary tract (mCi) urinary tract interval (hr) dose (rad)

in first 3 days (mCi) in last

7 days

1 1 0.399 68.72

(100-125) 98.28 9.94 2 0.802 138.52

3 1.21 207.78

2 1 0.408 82.16

(125-150) 115.28 11.32 2 0.819 164.58

3 1.23 248.13

3 1 0.408 95.14

(150-175) 133.42 13.18 2 0.819 190.57

3 1.23 287.32

4 1 0.408 109.26

(175-200) 153.19 15.16 2 0.819 218.85

3 1.23 329.96

Conclusion: Water supplementation needs to be intensified to shorten the bladder voiding interval for the first three days just after giving iodine 131 to the thyroid cancer patients in order to reduce the absorbed doses to bladder.

Quantitative analysis of planar and SPECT methods of dose estimation.

K.L. Dixon, A. Celler. Medical Imaging Research Group at Vancouver Hospital and Health Science Centre, Vancouver, Canada.

Aim: Estimation of absorbed dose in tumour therapy is often carried out using only the data acquired from anterior and posterior whole body scans. Dose calculations of a 3-D object performed using only two projections will necessarily be based on a multitude of assumptions. This study sets out to quantitate the errors in cumulative activity estimations arising from those assumptions. A more accurate approach involves the normalisation of data acquired from a series of planar studies using information gathered from one or two SPECT scans. Materials and Method: The mathematical platform Matlab was used to simulate anterior and posterior acquisitions from a uniformly attenuating transaxial body slice. Hot lesions containing six times the background activity were placed at various positions within the slice. The geometric mean of these acquisitions were used to estimate the original activity distribution. More complex simulations were carried out using SimSet Monte Carlo software which modelled the scatter and attenuation of photons originating in the phantom and the imaging characteristics of the camera and collimator. Finally experiments were performed using a thorax phantom. The heart and two additional 'tumour' lesions contained six times the concentration of 99mTc present in the background region. Aseries of five planar anterior and posterior images were acquired at intervals allowing the physical decay of the radionuclide to simulate biological clearance of the pharmaceutical. Two additional SPECT studies were acquired during this period including transmission scans for attenuation correction. Results were analysed a) using only the planar data to estimate the cumulated activity, and b) using the SPECT data to normalise the planar information.

Results: The planar method using Matlab simulations showed errors in estimated activity of up to 50 % for lesions situated near the lateral edges of the body. Lesions closer to the centre showed errors in the region of 12 %. Larger errors were observed in the more realistic SimSet simulations. The cumulative activity estimated from the phantom studies showed errors greater than 100 % when using only the planar acquisition data. The application of SPECT data to normalise the planar values reduced the errors to 5 - 7 %.

Conclusions: The use of planar acquisitions can result in huge errors in the estimation of cumulated activity which is a parameter of great importance to the estimation of absorbed dose in tumour therapy. The use of attenuation corrected SPECT images to normalise the planar information substantially improves accuracy.

Salivary Gland scintigraphy to assess the efficacy of a putative radioprotective agent in patients with head and neck tumors undergoing radiotherapy.

E. Lazzeri (1), A. Alsharif (1), S. Boschi (1), A.M. Nocita (2), F. Ducci (2), G. Mariani (1). (1) Department of Nuclear Medicine of the University of Pisa, Pisa, Italy, (2) Department of Radiotherapy of the University of Pisa, Pisa, Italy.

Aim: Salivary gland fibrosis is a frequent complication of radiotherapy in patients with head and neck tumors. Amifostin has recently been proposed as a radioprotective agent preventing or reducing this complication. The aim of our study was to scintigraphically evaluate the efficacy of this salivary protector in patients with head and neck tumors whose radiotheraphy field included the salivary glands.

Materials and methods: We have so far performed 31 scintigraphies in 13 patients (10 men and 3 women, mean age yr) with head and neck tumors; 9/13 patients (group A) were pre-treated with amifostin before first radiotherapy session, all patients underwent pre-treatment scintigraphy and at least one post-radiotheraphy study, The complete follow-up scintigraphy protocol including imaging at the 3, 6 and 12 month time points (mean duration of follow-up months). Patients were injected i.v. with 185 MBq 99mTc-O4- and dynamic scans were acquired for 60 min post-injection (1 min/frame). Salivation was induced at the 45th minute by oral administration of 4 ml of lemon juice. After visual evaluation, semiquantitative analysis was performed by manually drawning regular-box regions of interest were positioned on the parotid and submandibular glands and by generating time/activity curves. Results: No significant changes were observed in the early post-radiotherapy scans in 6 patients of group A; whereas 3 patients of this group had a marked reduction of salivary gland. On the other hand, all control patients (4/13 ) had a marked reduction of salivary gland (ranging between 50-90%) in basal evaluation (3 months after radiotherapy). Significant reduction of tracer uptake (> 50%) was closely correlated with clinical evidence of xerostomy. Conclusions: The preliminary results obtained in this study appear to confirm clinical advantage of treatment with amifostin for salivary gland protection during radiotherapy.

RADAR: The RAdiation Dose Assessment Resource. An Internet-Based Resource with Dose Information for Nuclear Medicine and Occupational Radiation Safety

M. Stabin (1), J.A. Siegel (2), J. Hunt (3), R.B. Sparks (4). (1) Vanderbilt University, Nashville, TN, USA, (2) Nuclear Physics Enterprises, Cherry Hill, NJ,USA, (3) Comissao Nacional de Energia Nuclear, Rio de Janeiro, RJ, BR, (4) Creative Development Enterprises, Knoxville, TN, USA.

An internet-based resource has been developed to organize and disseminate information about radiation dose calculations, from both internal and external sources, with applications in nuclear medicine as well as health physics. The site contains data available for electronic download from a number of well established sources, guidance documents, online training courses, software tools, and other resources. The great majority of the information on the site is available at no charge; some services are fee-based (such as the on-line courses and some software). Free information at present includes (1) a new set of decay data for over 800 nuclides recently derived from the Brookhaven National Laboratory site, with standard decay data and beta spectra, (2) absorbed fractions for major organs for 10 stylized phantoms and one realistic, voxel-based phantom, (3) absorbed fractions for various organ models not included in the traditional phantoms (e.g. prostate gland, peritoneal cavity, small spheres, MIRD head and brain model), (4) dose conversion factors for all nuclides for all phantoms and organ models, (5) kinetic models for many radiopharmaceuticals, (6) internal and external dose conversion factors for hundreds of radionuclides, (7) guidance documents on data collection and methods in dosimetry, and (8) links to many other useful sites with dosimetry and radiation-related information. New information and sources of data will be continually added to the site. The goal is to provide the user community with the best up-to-date sources of such information in an electronic format that facilitates widespread use and easy access. This is particularly important in third world or developing countries that have limited access to (often expensive) printed materials.

Radiation exposure to medical staff and radioactive contamination from sentinel node navigation surgery

K. Ejiri (1), K. Minami (1), H. Toyama (2), G. Kudo (2), H. Hattori (2), K. Iwase (2), K. Matsunaga (2), Y. Udagawa (2), K. Katada (2). (1) Fujita Health University School of Health Sciences, (2) Fujita Health University School of Medicine.

Aim: To establish the safe use of 99mTc tin-colloid (Sn) in widespread sentinel node navigation surgery (SNNS), we measured and estimated the radiation exposure from the patients to medical and surgical staff.

Materials and Methods: Thirteen patients (breast cancer: 11, malignant melanoma: 1, vulva cancer: 1) were injected with 69 to 180 MBq of Sn 1 day before SNNS. Radiation dose rates were recorded at 0.05, 0.5, 1.0 and 1.5 m from the patient's body surface by three ionization survey-meters immediately after injection of Sn. During SNNS, radiation exposure was measured by semiconductor detectors and ring-type glass dosimeters for body and hands. Contamination of the surgical materials was measured with scintillation survey meter, and the floor was examined with wipe test.

Results: Around the patients, the maximum total radiation doses (E) of 240, 41, 15 and 8 ?Sv/74MBq at 0.05, 0.5 1.0 and 1.5 m were calculated from the physical T1/2 of 99m Tc and the initial radiation dose rates. The maximum cumulative dose (Hp(10)) during SNNS to primary surgeon, assisting surgeon and nurse, and anesthetist were 3.7, 1.4, 0.3 and 0.6 ?Sv/operation, respectively. The maximum hand dose (Hp(70?m)) of 100?Sv/operation was recorded twice in the operations. Contamination in bloody gauze was maximum 20 x background counting. In the other materials, contamination range was up to 12 x background counting. There was no contamination on the floor.

Conclusions: In SNNS, radiation exposure to medical and surgical staff is minimal regarding no action. However, materials used for SNNS are significantly contaminated regarding careful handling of these materials to be separately stored for a few days.

Date: 02.09.2002 • Time: 14:30 - 16:00 RADIOBIOLOGY

Hall: Poster exhibition

What is the cause of chromosomal damage induced in vitro by 99mTc-MIBI on human peripheral blood lymphocytes ?

N. Taibi (1-2), P. Bourgeois (1), M. Kirsch-Volders (2). (1) Service of Nuclear Medicine, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium, (2) Laboratory for Anthropogenetics, Vrije Universiteit Brussel, Brussels, Belgium.

Introduction: It has been demonstrated that 99mTc-MIBI is specifically taken up in vitro by the HPBL, cells which are known to be highly radiosensitive. Using the cytokinesis block Micro-Nucleus (MN) assay, chromosomal damages have also been demonstrated after in vitro exposure of HPBL to at least 10 cGy or 0.25 milliCies of 99mTc-MIBI. After in vivo scinti-graphic investigations using 99mTc-MIBI (25 milliCies), it was also found that 4 out of 15 patients exhibited significant increase of the numbers of binucleated cells with MN. Aim of the study: to determine what is possible cause of the chromosome damage induced by 99mTc-MIBI : 99mTc (the external irradiation ?), the unlabeled chemical MIBI (that can be toxic by itself) or the 99mTc-labeled MIBI (the internalised irradiation and the Auger electrons emitted by the Tc-99m) ?

Material and methods: Blood samples from eight patients (among whose two demonstrated therafter chromosomal damages in the blood sample obtained after in vivo injection of 99MTc-MIBI for diagnostic purposes) were divided in four fractions. The first fraction was used as control and the three others were incubated in vitro respectively with 99mTc alone (0.25 milliCies), with 0.25 milliCies of 99mTc-labeled MIBI and with the corresponding amount of unlabeled MIBI. The cytokinesis block micronucleus (MN) assay was used and the frequency of binucleated cells (BC) with MN (MNBC) was analysed in cultured HPBL of each tested fraction.

Results: Using statistical test for paired-values, no difference was observed beteween controls and MIBI alone (p = 0.302) (although one of the two patients who demonstrated chromosomal damages after in vivo « evaluation »-injection of 99mTc-MIBI showed one two-fold increase of the MNBC frequency with MIBI alone). No significant difference (p = 0.084) was found when comparing control fractions and 99mTc-MIBI tested fractions but the two patients who demonstrated chromosomal damages after in vivo « evaluation »-injection of 99mTc-MIBI showed 2.5-fold increase of the MNBC when compared to control values. With 99mTc alone, the increase was statistically significant (p = 0.006 when compared to control and five patients had increase of MNBC higher than 1.5 fold the normal. Once again, however, the two patients « positive » after in vivo exposure exhibited the highest increase. Conclusion: Our results suggest that ionizing radiation of 99mTc was the cause of the chro-mosomic damages induced in vivo by the 99mTc-MIBI..

Thermoluminescent dosimetric threads: optimisation and use for radioprotection

J.D. Jarnet (1), B. Denizot (1), F. Hindre (1), A. Lisbonas (2), M. Bardies (3), P. Jallet (1). (1) Inserm ERIT-M 0104, Angers, France, (2) CRLCC Rene Gauducheau, Nantes, FRANCE, (3) Inserm U463, Nantes, France.

Aim: New polypropylene threads incorporating (LiF : Mg, Cu, P) thermoluminescent powder (French patent 9903729) are promising for specific applications like in-vivo dosimetry and irradiation evaluation of extremities (hands, fingers,...). Although their intrinsic reliability and use facility, their sensitivity as well as their waterproofness (need for steam sterilization) are to be improved by optimisation of manufacturing parameters. Dosimetry applications to patients and medical staffs are presented.

Material and methods: Extrusion method (simple extrusion versus co-extrusion), LiF powder granulometry (80-120 ^m range versus smaller than 50 ^m), load rate (from 50 up to 90% W/W), proportion of adjuvants and plasticizers were evaluated according to sensitivity, repro-ducibility, impermeability (lack of LiF release), and fading induced by autoclave sterilization. Two dosimetric studies are in progress : one evaluating the doses at finger level for orthopaedic surgeons, the other on premature babies subjected to multiple X-ray images during their residence in neonatal departments of either Nantes or Angers university Hospitals. Results: Increasing the load rate up to 80% and granulometry (80-120 ^m range) rises up the sensitivity of about 40%, minimal detected dose is now neighbouring the mGy. Co-extrusion and sealing of thread extremities reduce LiF release (close to zero) and allow autoclave sterilization (134°C for 18 minutes). Although encouraging, radioprotection dose evaluations are not yet statistically interpretable.

Conclusion: Increasing the dosimetry thread performances (sensitivity, waterproofness and ability to sterilization) and flexibility allow new radioprotection applications. New fields in internal radiotherapy are under consideration.

Cytogenetic damages of Human Peripheral Blood Lymphocytes after in vivo scintigraphic imaging with 99mTc-MIBI ? Study in 15 subjects using the cytokinesis block mincronucleus assay.

N. Taibi (1,2), P. Bourgeois (1), M. Kirsch-Volders (2). (1) Service of Nuclear Medicine, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium, (2) Laboratory for Anthropogenetics, Vrije Universiteit of Brussels, Brussels, Belgium.

Introduction: 99mTc-MIBI is currently used for parathyroid and thyroid imaging, for cardiac investigations and for the evaluation of various tumours. It has been demonstrated that 99mTc-MIBI is specifically taken up by the HPBL and that cytogenetic damages can be found in HPBL cultured from blood incubated in vitro with activity equal to at least 0.25 milliCies . Aim of the study: to detect the possible chromosomic damages induced on HPBL by in vivo scintigraphic imagings and using diagnostic activities of 99mTc-MIBI. Material and methods: Blood samples from 15 patients among whose 3 men and 2 women presented with hyperparathyroidy (research of parathyroid adenoma) and 10 had cardiac evaluation for cancer (6 women with breast cancer, two men and one woman with one hematogenous disease and one woman with rhabdomyosarcoma, who had been treated with radiotherapy and/or chemotherapy-ies) were obtained before and 2 to 3 hours after the IV administration of 25 milliCies of 99mTc-MIBI. The cytokinesis block micronucleus (MN) assay was used and the frequency of binucleated cells (BC) with MN (MNBC) was analysed in cultured HPBL. Pre and post injection of MIBI percentages were compared using statistical tests for paired values.

Results: Considering the series as a whole, the frequencies of MNBC were significantly higher in blood after exposure to 99mTc-MIBI than in control pre-injection samples (p < 0.001). However, only 4 patients (two of the women treated for breast cancer and two men with hyperparathyroidy) exhibited significant increase of their percentages of MNBC. Conclusion: after in vivo scintigraphic investigations using (25 milliCies of) 99mTc-MIBI, chromosomic damages can be thus demonstrated in HPBL from « normal » and cancerous patients. The radiosensitivity, however, does not seem to be « systematic » but rather « individual ».

Probability function of thyroid remnants ablation after first course of radioiodine treatment of thyroid cancer patients

O.V. Kozak, E. Chebotareva, B. Sinyuta, M. Zavelevich, V. Shishkina. Institute of Oncology, Kiev, Ukraine.

Probability function of thyroid remnants ablation after first course of radioiodine treatment of thyroid cancer patients

Kozak O.V, Chebotareva E.D., Sinyuta B.F., Institute of Oncology, Kiev, Ukraine

The aim of the study was to determine function predicting thyroid remnants ablation after first course of radioiodine treatment of thyroid cancer patients on the basis of diagnostic scintigra-phy data.

30 patients with differentiated thyroid cancer have been treated with I131 after diagnostic scintigraphy (74 MBq). Activities administered A ranged from 1574 to 51200 MBq. Thyroid remnants only have been determined during the treatment. Remnants ablation took place in 24 patients after the first course of I131 treatment and nonablation was observed in 6 patients. Parameters of I131 kinetics of excretion and accumulation in remnants were calculated upon scintigraphy data during 4 days after activity administration: T- effective half time of I131 excretion in remnants, N1- max cpm in ROI over remnants in 24 hours after activity administration; N0 - background cpm (upon the shoulder); N= N1- N0. The parameters were normalized to their average values Ta, Na, Aa: Tn= T/Ta, Nn=N/Na, An= A/Aa where Ta = 5.73 d, Na= 38.4, Aa=3035 MBq. Logistic function was chosen for describing probability of remnants ablation after the first course of I131 treatment. Logistic regression analysis was delivered.

As a result f = (-3+4-An-0.608-Nn+0.71-Tn)/[1+(-3+4-An-0.608-Nn+0.71-Tn)j f = 0.81 +0.19 in the case of remnants ablation f = 0.39 + 0.20 in the case of non-ablation

Thus logistic function could be considered as probability value of remnants ablation after first course of I131 treatment. The choice of activity value is decisive in the outcome of I131 treatment (4 > 0.608; 0.710). The greater volume of thyroid remnants is the greater activity is necessary for its ablation. The higher effective half time of I131 excretion in remnants is the higher probability of remnants ablation.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition RADIATION PROTECTION

Radiation Dose to the Pediatric Population in the Czech Republic due to Diagnostic Nuclear Medicine in 1999 and Trends during the Period of 1987 - 1999

V. Husak (1), K. Petrova (2), Z. Prouza (2), P. Koranda (1), M. Myslivecek (1). (1) Department of Nuclear Medicine, University Hospital, Olomouc, Czech Republic, (2) State Office for Nuclear Safety, Prague, Czech Republic.

Aim: To determine an annual collective effective dose SE to children younger than 15 years in the Czech Republic (CR) from nuclear medicine (NM) and compare it with previous estimates in 1987 and 1995 - 1996.

Methods: Frequencies of diagnostic procedures in children, types and amounts of administered radiopharmaceuticals (RP) in 1999 were provided by the General Health Insurance Company (GHIC) covering 75 % of CR inhabitants. It was assumed that extrapolated GHIC frequencies and other information were representative of the Czech population. Data for year II.1995-I.1996 were obtained in the same way, a questionnaire was used to get data concerning 1987. Conversion factors (mSv/MBq) for RP were taken from ICRP Publication 80. Results: Atotal of 19,120 examinations of children younger than 15 years were performed in 1999, representing 7 % of the annual amount of all NM examinations (including children and adults). The resulting annual SE to the pediatric population and the mean effective dose per exam were found to be 49.7 man Sv (i. e. 5.6 % of Se to all patients examined by NM procedures in CR), and 2.6 mSv, respectively. The contributions of the respective procedures in various pediatric body systems to the annual „pediatric" Se were as follows: renal 45.2 %, bone 35.8 %, GIT 6.9 %, lung 3.6 %, brain 3.3 %, cardiovascular 3.1 %, thyroid 0.3 %, others 1.8 %. In comparison with 1987 and II.1995-I.1996 SE to children increased by a factor of 2.8 and 4.6, respectively. A proportion of „pediatric" Se of the total Se increased from 2 % in 1987 to 5.6 % in 1999 whereas the total Se was elevated from 570 to 890 man Sv only. Conclusions: A favourable fact is that the mean effective dose per exam in 1999 was lower than 80 % of that in adults. Even though the number of pediatric NM examinations was small as compared with that of radiodiagnostic procedures performed in children in 1999, the continuous increase in the „pediatric" annual SE due to NM is worth considering. Therefore, a special attention should be paid to radiation protection of children in CR; in particular, a requirement has to be more respected that each examination is carried out on the condition of a strong clinical indication.

The Effects of Technetium-99m Methylendiphosphanate (Tc-99m MDP) on Erytrocyte Antioxidant Enzyme Activities

F. Aydin, A. Boz, N. Gurbuz, T.A. Aksu, B. Karayalgin, Y. Aliciguzel. Departments of Nuclear Medicine and Biochemistry of the Akdeniz University, Antalya, Turkey.

Background: Radioactive substances lead to the production of oxidants which alter intracel-lular molecular structure and disturb cell function. Erythrocyte antioxidant enzymes, Catalase (CAT), Selenium Dependent Glutathion Peroxidase (GSH-Px), Cu-Zn Superoxide Dismutase (SOD), scavence hydrojen peroxide (H2O2) which is a potent oxidant. In this study we aimed to assess the effect of radioactive substances used for routine diagnostic bone scintigraphy on erythrocyte antioxidant enzyme activity which is a marker of oxidant stress. Materials and Methods: 20 patients (age range 40-70; 5 W, 15 M) with cancer who underwent Tc-99m MDP bone scintigraphy for investigation of metastasis were included into the study. Blood samples were taken before administration of 20 mCi Tc-99m MDP( group-1) and after injection (group-2). CAT , GSH-Px and SOD enzyme activities were determined by spectrophotometry.

Results: GSH-Px activity was significantly higher (p<0.01) in group-2 (1.68±0.85) compared to group-1 (1.29±0.64). CAT activity was lower in group-2 (124± 101.4) compared to group-1 (137±92.05) SOD activity did not differ statistically between group-1 (1268±205.53) and group2 (1300±278.95) The 15 % increase in GSH-Px activity might be the result of increased H2O2 production due to the oxidative stress caused by Tc-99m MDP. The decrease in CAT activity may led us to the conclusion that the CAT structure in the porphyrin ring may damaged. In this study we only investigated whether the diagnostic radiopharmaceutical agent caused changes in enzyme activity. Further studies investigating how long this change in enzyme activity lasts may be useful.

Gamma radiation levels inside a cyclotron bunker during positron emission radionuclides production

J.M. Martí-Climent, I. Peñuelas, J. Arbizu, M.J. García-Velloso, F.J. Boán, J.A. Richter. Department of Nuclear Medicine. University Hospital. University of Navarra. Pamplona, Spain.

Aim: Radionuclide production for positron emission tomography is done using a cyclotron by means of nuclear reactions that generate intensive gamma and neutron fields. These impose restrictions to cyclotron layout and procedures. Our objective was to evaluate gamma radiation levels inside a cyclotron bunker during its normal operation.

Methods: Measurements were done around a cyclotron Cyclone 18/9 (IBA) that accelerates protons and deuterons at 18 and 9 MeV, respectively, and target currents up to 30 ?A in normal operation. A Geiger counter LB-6500-3 (Berthold) (dose rate range: 10-5 to 1 Sv/h) was positioned in front of four targets (at 60 cm from the cyclotron surface) and close to the cyclotron vault door, at 143 cm from the floor (corresponding to the cyclotron medium plane). Dose equivalent rates, with the convention of 100 R equivalent to 1 Sv, were evaluated at different beam currents for each target. Target number (#N) corresponds to port position around the cyclotron.

Results: Dose rates at beam current of 5.2 ?Awere:

Target_Dose rate (mSv/h at measuring point (#)

Port Form Reaction #1 #3 #5 #6 #door

#1 18F2 20Ne(d,?)18F 28.8 2.30 1.55 2.04 1.30

#3 11CO2 14N(p,?)11C 2.36 104.20 2.11 2.30 1.28

#5 15O2 14N(d,n)15O 1.53 1.78 56.20 4.86 2.07

#6 18F- 20O(p,n)18F 4.33 5.25 17.83 80.00 7.80

As the port positions for targets have a likely octagonal geometry, radiation measurements showed this symmetry. Although the detector measuring range is up to 1 Sv/h, the measurements performed at different beam currents showed detector nonlinear response over 10 mSv/h rates.

Extrapolation of these results to normal bombardment conditions results on dose rates of 94, 400, 162 and 462 mSv/h in front of the 18F2, 11CO2, 15O2 and 18F- targets (with beam currents of 17, 20, 15 and 30 ?Arespectively); but measurements only reached 246 mSv/h (30,4 ?Afor 18F- production).

Conclusions: The radiation levels measured justify the radiation protection restrictions and procedures around the cyclotron. Although the 18F- target is considered to produce the highest neutron field, the highest gamma radiation dose rates were found during the 11C production though the 14N(p,?)11C reaction. These results could be used as a first dose estimation in case of an accident due to a person remaining inside the cyclotron vault during its operation.

Exposure to radiation to relatives of patients treated with 131-iodine: effective halflife-dependent discharge-body-activity-limit

B. Sattler (1), J. Petzold (1), J. Lorenz (2), O. Sabri (1). (1) University of Leipzig, Clinic for Nuclear Medicine, (2) Regional authority for environment and geology, Leipzig, Germany.

AIM: The recently released ICRP recommendation 60 limits for exposure to radiation of public persons of 1 mSv per year. In most European Union countries, these limits are implemented into the national radiation protection laws. In order to limit the exposure to radiation to relatives of patients treated with 131-iodine, it has to be is to ensured that patients discharged from radioiodine therapy do not cause a dose rate higher than 3.5^Sv/h in 2m distance in order to stay below the 1 mSv/a limit for public persons. This corresponds to a residual body activity of 250 MBq 131-iodine on the day of discharge.

MATERIAL: This study included 25 patients treated with 0.2 to 5.2 GBq 131-iodine for benign or malignant thyroid disease. Patients and next relatives were monitored with film badges and TLD-ring-dosimeters for 14 days after discharge. Patients and relatives were asked to place the badges under the pillow and to wear the TLD-ring-dosimeter during the whole day.

All patients except one (20 mSv/h in this case) were discharged at dose rates between 2 and 15 mSv/h in a distance of 2 meters. Only those relatives with doses equal or lower that 1 mSv on the TLD-ringdosimeter (n=19) were included into statistical analyses. RESULTS: As expected, the TLD-ring dosimeters reported higher doses than the badges. Relatives of patients with malignant thyroid disease were exposed to significantly lower doses than relatives of patients with benign diseases. There is a significant positive correlation (r=0,793) between the exposure to radiation to the relatives and the effective half-life of 131-iodine in the patients. The exposure to radiation ascends with the effective halflife. CONCLUSION: We therefore suggest to use an effective half-life dependent limit of the residual activity to determine the time point of discharge (see table 1). If measurements during therapy yield an effective half-life greater than 5 days, then 250 MBq should remain the discharge-limit (marked gray in table ).

Dose rate2m [ßSv/h]

T1/2epf [d]

29,8 1 2,020

14,4 2 0,976

9,7 3 0,657

7,3 4 0,494

5,8 5 0,393

3,6 6-8 0,325-0,244

Date: 02.09.2002 BIOKINETICS

Time: 14:30 - 16:00 • Hall: Poster exhibition

Quantification of Tracer Kinetics: Comparison of Gamma Camera and Scintillation Probe

K. von Hof, L.F. Schelper, B. Meller, E. Richter, M. Baehre. University Clinic Luebeck, Department of Radiotherapy and Nuclear Medicine, Luebeck, Germany.

Aim: Up to now there are no recommendations to determine tracer kinetics either with gamma cameras (GC) or with scintillation probes (SP). Kinetic studies are frequently used for diagnostic, therapeutical or scientific purposes. The question of our study was whether results of both systems are closely correlated. The thyroid gland (wide range of volumes) and the radioiodine uptake test were selected as field of activity.

Material and Methods: Quantitative investigations were performed in 25 patients 24 h after application of 2-5 MBq 131I. Scintigrams were analysed by ROI-technique. For SP collimated measurements of integral count rate were used. Therapeutic activity was calculated by means of maximum uptake and half life period (HLP) of both systems (Marinelli formula). We defined three subgroups of thyroid volume (TV): 9 organs were smaller than 20 ml (G1), 9 showed volumes between 20 and 40 ml (G2), 7 were larger than 40 ml (G3). For statistical evaluation distribution-free tests were used.

Results: Median volume of G1 was 15 ml, of G2 28 ml and of G3 56 ml. Comparison of maximum uptake between both systems showed significant differences (p<0,05) in dependence of TV (G1 and G3). The percental deviation of maximum uptake using both systems shows a linear augmentation in dependence of increasing TV. The median maximum uptake of GC was 36 % versus 34 % of SP. The median HLP was 7 d in case of GC and 6.4 d for SP. Furthermore, no relationship between TV and HLP could be detected. The calculated median therapeutic activity that was based on measurements either with GC (786 MBq) or SP (730 MBq) differed significantly (p<0,005).

Conclusions: Significant discrepancies between the kinetics determined by GC and SP were found with important consequences for therapeutic application. Determination of tracer kinetics by GC allows correct uptake determination and improves optimal estimation of HLP by reduction of surrounding background activity (shielding by collimator/usage of ROI-technique). Furthermore, GC offers a constant efficiency within the field of view (FOV) whereas SP showed a considerable loss of efficiency near the edge of FOV. As determination of maximum uptake was dependent on TV we suggest that GC should be used to improve the accuracy of kinetic studies.

Is radioguided localization of the sentinel node a safe technique in pregnant women with breast cancer?

M. Cremonesi, G. Trifiro, O. Gentilini, M. Intra, M. Ferrari, D. Militano, G. Bassani, G. Tosi, G. Paganelli. Medical Physics Department, Nuclear Medicine Division and Senology Division, European Institute of Oncology, Milan, Italy.

Aim: The great value of the radioguided localization of the sentinel lymph node (SN) in the management of breast cancer patients leads to consider the possibility of applying this technique also during pregnancy. The aim of this work was to specifically investigate the safety of the procedure in terms of radiation protection and the possible absorbed doses to the fetus considering different stages of gestation.

Methods: 10 premenopausal patients with breast cancer undergoing SN surgery have been included in the study. The protocol used for SN consists of the peritumoral injection of approximately 12 MBq of 99mTc-HSA. All the patients underwent surgical removal of the lesion and the of SN 16 h p.i. To observe the localization of radiotracer, static (15 min and 15 h p.i) and whole body (15 h p.i.) scintigraphic images were acquired. Activity concentration in the complete urine collection performed within established time intervals (0-2, 2-4, 4-8, 8-16 h p.i.) was evaluated by a gamma-counter. TLD dosemeters were placed upon epigastrium, umbilicus and hypogastrium immediately after the injection of the tracer and removed immediately before surgery; for the estimate of the possible cumulated absorbed dose, these sites of measurement were considered representative for the evaluation of the possible cumulated absorbed dose to the fetus at different phases of pregnancy.

Results: Scintigraphic images showed no diffusion of the radiotracer, including urinary bladder, but in the SN and the injection site, demonstrating negligible irradiation to other tissues. These findings were confirmed by the total activity excreted in the urine (mean values: 0.4% +/- 0.3%; range: 0.1% - 1.4%). In 4 patients, all absorbed dose measurements resulted lower than TLD sensitivity (<1 microGy); in the other patients, the absorbed dose to epigastrium, umbilicus and hypogastrium were within the following ranges: 30-320, 0-60, 30-140 microGy, respectively.

Conclusions: The absorbed doses are strictly related to the amount of injected activity, tracer dimensions and tumour site. According to the protocols described above, SN biopsy can be safely applied also during pregnancy, as specific radiation protection evaluations related to any phase of gestation do not indicate significant risks to the fetus compared to the important clinical benefit to the patients. These conclusions are consistent with the correlations between dose for stochastic effects and threshold values for deterministic effects reported in the pub-blication ICRP 60.

Antithyroid Medication and Radioiodine Kinetic of the Thyroid

G. Kirsch (1), A. Zinke (1), M. Trautmann (1), R. Meckel (1), U. Bohl (1), W. Meng (2). (1) Department of Nuclear Medicine of the University of Greifswald, (2) Department of Internal Medicine, Greifswald, Germany.

Aim: Possible negative effects of antithyroid medication on radioiodine therapy (RIT) of hyperthyroidism can be excluded by interrupting medication some days before RIT; so iodine uptake should not be influenced. After or during RIT antithyroid drugs are often again to be given for some weeks to prevent exacerbation of hyperthyroidism.

The effect of this medication on RIT (reducing of effective half life) is controversly discussed and difficult to prove by interindividual comparisons because of many variable influence factors.

We examined the effect of methimazol (starting 4d after RI application) on RI elimination half-life in intratherapeutic studies by very frequent measurements of thyroid RI uptake. So relevant changes in half-life provoked by medication should be detected in one patient during one RIT excluding most other influencing factors.

Materials and Methods: In 40 RIT (Graves disease or autonomies) methimazol medication (5-20mg/d) restarted on day 3 or 4 after iv RI application. Thyroid iodine uptake was measured frequently (4-12 times per day) for 5-8d. Effective half-life of thyroid RI elimination was calculated separately for the pre and post medication periods. Differences of more than 1d were regarded as relevant changes in half-life.

Results: After methimazol medication RI elimination half-life was unchanged in 85% (36/40), reduced in 10% (4/40) and elongated in 5% (2/40). There were no significant differences between the off and on medication periods. Similar variability in half-life (early to late periods) is found in controls without methimazol medication during RIT. Conclusion: Frequent iodine uptake measurements result in good quality RIT kinetic curves that allow half-life comparison between early (off medication) and late (on medication) periods.

There is no relevant (half-life shortening) effect of methimazol (at doses 5-20mg/d) if drug administration starts some days after RI application. So in case of exacerbated hyperthy-roidism during RIT (after pre RIT drug interruption) antithyroid medication can be restarted without fear of reducing relevantly the RIT dose to the thyroid.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition TECHNETIUM AND IMMUNOANALYSIS

Developing an instant preparation for 99mTc labeling of MAG3 conjugated biomolecules.

Labeling with 99mTc and biochemical characterization of CCK8 derivatized with diphenylphosphine

L. Aloj (1), M.R. Panico (1), C. Caraco' (2), S. De Luca (1), U. Mazzi (3), S. Del Vecchio (1), M. Salvatore (4). (1) Istituto di Biostrutture e Bioimmagini, CNR, Napoli, Italy, (2) Istituto di Medicina Sperimentale e Biotecnologie, CNR, Piano Lago Mangone (CS), ITALY, (3) Dipartimento di Scienze Farmaceutiche, Universita' di Padova, Italy, (4) Dipartimento di Scienze Biomorfologiche e Funzionali, Universita' Federico II, Napoli, Italy..

Cholecystokinin (CCK) receptor isoforms have been shown to be overexpressed in neuroendocrine and other tumors. Development of radiolabeled ligands for these receptors is appealing for use in nuclear medicine Previous attempts at CCK receptor imaging have utilized 111In as label. Labeling with 99mTc would be preferable for imaging purposes. Aim. To evaluate the binding properties of the CCK8 peptide tagged with diphenylphosphine, labeled with 99mTc and test its suitability for receptor imaging.

Methods. The CCK8 peptide was modified at its N-terminus by introducing, in the following order: cysteine, glycine and a diphenylphosphinopropionyl moiety, giving a 10-residue peptide derivative, PhosGC-CCK8. Fifty ^g of this peptide were incubated with 4-10 mCi of freshly eluted Na99mTcO4, in a solution containing10 mM NaOH, and SnCl2 and Na4P2O7 both at a final concentration of 100 ^M, at 60°C for 1 hour. Complex formation was determined by HPLC analysis using a reversed phase C-18 column and a Water/Acetonitrile gradient. A431 cells stably transfected with a cDNA encoding for the human CCK-B receptor were utilized to determine binding affinity, internalization and retention of the labeled peptide, in comparison to wild-type A431 cells.

Results. Incorporation of label into the peptide was typically 90-95%. Experiments performed at 4°C on A431-CCKBR cells showed saturable binding of the compound with an apparent Kd of 32 + 5 nM and 1.73 + 0.09 x 106 sites/ cell. Wild Type A431 cells showed negligible binding of the peptide. Incubation of PhosGC-CCK8 with cells at 37°C showed progressive increase of cell associated activity over time, whereas levels were constant in cells incubated at 4°C. Attempts to displace cell associated activity by incubation with excess unlabeled pep-tide after 2 hours of incubation were successful in cells incubated at 4°C (~ 80 % of activity displaced) but very little displacement was seen in cells incubated at 37°C (<20%) suggestive of internalization of the peptide under these conditions. Release of activity from cells incubated at 37°C after removal of excess radioactivity by washing was bi-exponential with a fast component likely due to release of cell surface bound peptide (T 1/2 ~ 50 min) and a slow component (T 1/2 ~ 350 min) presumably due to release of internalized and subsequently metabolized compound.

Conclusion. PhosGC-CCK8 shows high specific binding to CCK-B receptors, high target-to-non target ratios, is internalized and label is released from cells at relatively slow rates indicating that it can be suitable for CCK-B receptor imaging.

M. Rusckowski, G. Liu, S. Zhang, J. He, D.J. Hnatowich. Department of Radiology, Division of Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA, USA.

Aims: S-acetyl MAG3 is being used as a chelator for 99mTc labeling of biomolecules but usually with the need for postlabeling purification. Our goal was to develop an instant method of labeling MAG3-conjugates with labeling efficiencies of at least 90% to avoid postlabeling purification.

Materials and Methods: As a model biomolecule, a 15 mer morpholino (MORF, a DNA analogue), was conjugated through its primary amine with NHS-MAG3 in the usual manner and the MAG3-MORF purified over a P4 column as before. The conjugate was radiolabeled using stannous ion as usual and the impurities identified using SE HPLC. Various methods were then investigated to remove the impurities.

Results: With tartrate as transchelator, the impurities were identified as labeled free MAG3 and labeled tartrate. The labeled free MAG3 could not be removed by re-purification using the usual pH 5.2 NH4OAc buffer. However, this impurity could be completely prevented if the conjugate was adjusted to pH 7.6, heated in boiling water for 20 min, and then re-purified on P4 before labeling. The labeled tartrate impurities were prevented by optimizing the labeling recipe. The following procedure for purification of the conjugation mixture and subsequent labeling was adopted: After conjugation of MORF with S-acetyl NHS-MAG3 (molar ratio 1:20) in pH 8.0 HEPES buffer and purification over P4 with pH 5.2 NfyOAc eluant, the conjugate fractions were combined and adjusted to pH 7.6 followed by heating in boiling water for 20 min. The conjugate was then purified over P4 again for storage at refrigerator temperatures. Labeling was achieved simply by adding less than 3 mCi of 99mTc-pertechnetate to a solution of at least 0.4 ^g MAG3-MORF in 35 ^L NfyOAc buffer pH 5.2, 500 ^g of tartrate dihydrate in a 10 ^L pH 9.2 buffer, and 4 - 20 ^g of fresh stannous chloride dihydrate in 0.01 M HCl. After heating for 20 min in boiling water, the labeling efficiency was always over 95% as determined by SE HPLC and paper chromatography. Specific activities as high as 7400 ^Ci/^g MORF15 were achieved.

Conclusion: By making several relatively simple changes to the routine procedure used to conjugate and radiolabel biomolecules with 99mTc via MAG3, a novel procedure was developed which results in labeling efficiency high enough to avoid postlabeling purification.

Biokinetics of three somatostatin analogs labeled with Tc-99m in rats

A. Laznickova (1), M. Laznicek (1), F. Trejtnar (1), C. Decristoforo (2). (1) Faculty of Pharmacy, Charles University, Hradec Kralove, Czech Republic, (2) University Hospital, Innsbruck, Austria.

Somatostatin receptor scintigraphy has proven to be a valuable method for the detection of many neuroendocrine tumors and their metastases. However, the use of indium-111 is not optimal for labeling of somatostatin receptor-specific peptides. To take advantage of the more suitable half-life, greater specific activity, excellent imaging properties, low cost and wider availability of Tc-99m, technetium was expected to be the preferred radiolabel. The aim of this study was to compare biodistribution and to analyze elimination mechanisms in rats of two somatostatin analogs /namely octreodide (OC) and lanreotide (LAN)/ labeled with Tc-99m by direct labeling method in comparison with that of Ty^-octreotide utilizing hydrazi-nonicotinamide as the bifunctional chelator (HYNIC-TOC). Labeling of OC and LAN with Tc-99m was accomplished by reduction of the cystein-bridge of the peptides, which provided two sulfhydryl groups for the radionuclide chelation. HYNIC-TOC labeling was performed with an employment of bifunctional chelate concept. Since HYNIC can occupy only two sites of the reduced technetium co-ordination sphere, ethylene diamine diacetic acid as a co-ligand was used. For biological experiments, male Wistar rats were used. An analysis of elimination mechanisms was performed with an employment of the perfused rat kidney and perfused rat liver. For all Tc-99m labeled peptides under study, the activity in blood and most organs decreased relatively rapidly with time. On the other hand, radiolabeled HYNIC-TOC was eliminated mostly by urine, whereas radiolabeled LAN and OC were excreted mainly by gastrointestinal tract to feces. Radioactivity uptake in the organs with high density of somato-statin receptors (pancreas and adrenals) were substantially lower for the peptides directly labeled with Tc-99m (LAN and OC) in comparison with that for Tc-HYNIC-TOC. The rat liver perfusion experiments showed that bile clearances of Tc-LAN and Tc-OC were more than two-order times higher than for HYNIC-TOC. Analysis of elimination mechanisms in the perfused rat kidney showed that all three peptides under study were eliminated mostly by glomerular filtration. Different protein binding of the agents (Tc-OC and Tc-HYNIC-TOC were only weakly bound, whereas Tc-LAN was strongly bound to proteins) resulted in substantially lower renal clearance of Tc-LAN when compared to the other peptides. The study demonstrated that an approach of direct Tc-99m-labeling of selected somatostatin analogs (OC and LAN) substantially altered the peptide binding affinity to somatostatin receptors in the organs with high density of these receptors. On the other hand, the results indicated that HYNIC-TOC labeled with Tc-99m is an attractive agent for the visualization of somatostatin receptors and could be useful for the scintigraphic imaging of endocrine tumors. The research was created under the support of program COST B12 of EU and partly by the Grant Agency of Charles University No. 264/2001.

A simple method of 99mTc-ciprofloxacin kit preparation

P. Komarek (1), I. Kleisner (2), M. Konopkova (3), I. Komarkova (4). (1) Department of Pharmaceutical Technology and Drug Control, Postgraduate Medical School, Prague, Czech Republic, (2) Department of Nuclear Medicine, Kralovske Vinohrady University Hospital, Prague, Czech Republic, (3) Department of Radioisotope Diagnostics, Institute for Clinical and Experimental Medicine, Prague, Czech Republic, (4) Department of Radiopharmaceuticals, State Institute for Drug Control, Prague, Czech Republic.

Aim: The aim of our study was to develop a simple and reproducible method of preparing a ciprofloxacin kit, which would meet the requirements for an easy and reliable technique of labelling with 99mTc.

Material and Methods: To prepare the kit, an insoluble redox polymer containing an end alpha(beta)-alanine-N, N?-diacetate group anchored to the dextran matrix was used. The redox polymer synthesised by the authors was incubated together with a 1% solution of ciprofloxacin in a 5% suspension at room temperature for 10 hours. The mixture was then filtered through a 0.22-^m pore size filter and then dispensed into sterile vials; 0.4 mL per vial. All steps were performed in a nitrogen atmosphere. The kit was stored at -35 °C. After its reconstitution, the kit was labelled with 99mTc for 10 min. at room temperature. The labelling efficiency was evaluated by ITLC and paper chromatography. The radiochemical purity of the ciprofloxacin-99mTc complex was determined in relation to the following factors: pH value, total content of ciprofloxacin, and the volume of sodium pertechnetate-99mTc. Ciprofloxacin biodistribution was evaluated in Wistar rats with Staphylococcus aureus infection in the left inguinal region 24 h after abscess induction. Accumulation of 99mTc activity was determined both using external gamma camera imaging and counting dissected tissues 1 hour after administration.

Results: The radiochemical purity is above 95% for kit-labelling pH values ranging between 3.3-3.7. At a pH of 3.45, labelled ciprofloxacin shows the highest stability and radiochemical purity. After the addition of 2-5 mL of sodium pertechnetate (99mTc), the 99mTc-ciprofloxacin complex is stable for at least 8 hours. The smallest amount of ciprofloxacin for a high labelling efficiency is 2 milligrams. The minimum proven shelf life of the prepared kit is 6 months. In experimentally induced inflammation, the amount of accumulated 99mTc-ciprofloxacin activity is five times that seen in control tissue.

Conclusion: The developed method of 99mTc-ciprofloxacin kit preparation employs a redox polymer in a new procedure, which enables the preparation of a stable kit with a high 99mTc-labelling efficiency. The labelled kit is suitable for scintigraphic imaging of infection. The study vas supported by grant No.NL/6071-3 awarded by the Internal Grant Agency of the Ministry of Health, Czech Republic.

Study of correlation of Natriuretic Peptide type-B and Echocardiography variables in transplanted heart .

I. Hervás (1), L. Almenar (2), J.L. Pérez-Pastor (1), J. Osca (2), A. Osa (2), P. González-Cabezas (1), D. Flores (1), P. Bello (1), A. Mateo (1). (1) Department of Nuclear Medicine. University Hospital La Fe. Valencia. SPAIN., (2) Department of Cardiology. University Hospital La Fe. Valencia, Spain.

Aim: Natriuretic Peptide type-B (BNP) is a cardiac hormone secreted predominantly from the ventricles and following impaired cardiac function its plasma concentrations are increased. High levels of BNP are detectable in plasma following orthotopic cardiac transplantation. Other studies try to find correlation between BNP and degree of rejection found in the endomyocardial biopsy. In the present, the correlation of BNP with echocardiography variables that show the status of ventricular function , is studied.

Methods: We have compared 92 BNP determinations with its correspondents echocardiography studies (performed the same day). A total of 33 heart transplanted patients (3 women and 30 men) aged 15 to 64 (mean age 51) were studied. BNP was determined using a radioim-munometric assay "Shionoria BNP Cis" that use a "sandwich" technique on solid phase. Echocardiography was performed with a Hewlett Packard Sonos 2500 instrument. Systolic function was defined as conserved when left ventricular ejection fraction (LVEF) was more than 55%, and as mildly, moderately or severely impaired when LVEF was 45-55%, 35-45%, or less than 35%, respectively. We have studied the correlation between BNP and: LV systolic function, isovolumetric relaxation time (IRT) , E-wave deceleration time (EDT), shortening fraction (SF) and LV mass. Statistical analysis: Student's t test and Pearson's correlation coefficient.

Results: BNP mean of patients with conserved LVEF was 171 pg/ml. BNP mean of patients with mildly, moderately or severely impaired LVEF was 789 pg/ml. There was statistical difference (p<0,001) between both means. The correlation coefficient of BNP-IRT was -0.4, BNP-EDT was -0.4, BNP-SF was - 0.1 and BNP-M was 0.3.

Conclusion: BNP levels of patients with conserved LV systolic function BNP were very significant lower. There is weak but significant correlation between BNP and IRT,EDT and LV mass.

It appears than BNP plasma levels are closely associated with left ventricular dysfunction.

A reliable thyroglobulin autoantibodies method is important for clinical interpretation of thyroglobulin

L. Lukinac, D. Krilic, D. Nothig-Hus, Z. Kusic. Department of Oncology and Nuclear Medicine, University Hospital Sestre Milosrdnice, Zagreb, Croatia.

The most difficult problem in clinical interpretation of thyroglobulin (Tg) concentrations is interference of thyroglobulin autoantibodies (TgA) in serum of patients with differentiated thyroid cancer (DTC). The influence of TgA may cause falsely positive or negative Tg results. Therefore, a specific problem is raising - a correct interpretation of Tg values. For detecting TgA, the agglutination assays predominate to EIA methods because of the cost or lack of equipment.

Aim: To specify the area of different TgAresults obtained by two methods. Which method should be used for thyroid antibody testing to get reliable Tg results? Materials & methods: Serum TgA levels were determined in parallel by two methods: A: a particle agglutination method Serodia TGA (Fujirebio, Japan, negative titre 1:100) and B: a quantitative enzyme-immunoassay (EIA) method Anti-Tg-Ab-Milenia (DPC, USA, normal: <100 IU/mL).

Results: In the period from 1999-2001 in each serum sample of 213 patients with DTC (beside thyrotropin and Tg concentrations), the presence of TgA was determined regularly by method A. In frozen samples, TgA was additionally measured by method B. Out of 63 negative TgA values, obtained with method A, there were 40 (63.5%) negative and 23 (36.5%) positive samples detected by method B. Contrary, out of 150 positive TgA values determined by method A, 113 (75.3%) were positive and 37 (24.7%) were negative by method B. Out of 72 positive (titre 1:400) samples measured by method A, 31 (43%) were detected as negative by method B. Also, 6 out of 50 (12%) samples of titre 1:1600 (method A) were also determined by method B as negative. Other 28 samples (titre >1:6400) were described as positive by both methods.

Conclusions: In the compared TgA results the agreement of 69.4 % was found (negative or positive by both methods); 30.6 % of positive values, measured by method A, were detected as negative by method B. It is uncertain which one of the two methods is more reliable. A need for an international standardisation in thyroid antibody testing is suggested.

Endomyocardial biopsy and natriuretic peptide type-B in transplat-ed human heart. A study of 349 BNP determinations.

I. Hervás (1), J. Osca (2), J.L. Pérez-Pastor (1), L. Almenar (2), A. Saura (1), P. González-Cabezas (1), D. Flores (1), P. Bello (1), A. Mateo (1). (1) Department of Nuclear Medicine. University Hospital La Fe, (2) Department of Cardiology . University Hospital La Fe, Valenzia, Spain.

AIM: Natriuretic peptide type-B (BNP) is a peptide of 32 amino acids secreted mainly by ventricular myocites in response to increased ventricular filling pressure and myocardial stretching. It is at present easily measurable by radioimmunometric assay. BNP have elevated circulating levels in patients with heart failure. Recent evidence suggests that adaptative changes in de-nervated transplanted human heart are associated with increased ventricular BNP gene expression. The aim of this study is to determine if the elevated levels of this peptide are correlated with the degree of rejection found in the endomyocardial biopsy (EMB). METHOD: We compared 349 BNP determinations with the corresponding EMB (The blood extraction for the BNP sample and BEM did not differed in time more than 48 hours). 80 patients (11 women and 69 men) after cardiac transplantation were studied. BNP was determined using a radioimmunometric assay "Shionoria BNP Cis" that use a "sandwich" technique on solid phase. EMB established the degrees of rejection according to the International Society of Heart and Lung transplantation Standardised Grading System. Patients were divided in four groups according to the EMB: First group (n=110) graded 0. Second (n=102) graded 1 A and 1 B. Third (n=79) graded 2. Fourth (n=58) graded 3 A, 3 B and 4. Statistical analysis: Mean and Standard Deviation for the Descriptive Statistics and Student's t test for the comparative statistics.

RESULTS: The first group presented a mean BNP value = 162,5 +/- 188,1 pg/ml, the second = 162,7 +/- 145 pg/ml., the third = 226,8 +/- 258 pg/ml and the fourth a mean BNP value = 380 +/- 455 pg/ml. The comparison of means of the different groups was the following:

GROUP COMPARISON P t

GROUP 1 AND 2 0,9948615 0,00645628

GROUP2AND 3 0,0359263 2,13421572

GROUP3AND 4 0,013306 2,55378836

GROUP3AND 1 0,049246 1,99720034

GROUP4AND 1 2,11E-05 4,6286732

GROUP4AND 2 1,51E-05 4,72180545

CONCLUSION: BNP levels are more increased in patients with upper degree of rejection in EMB. In the groups with lower risk of cardiac rejection (groups 1 and 2) we could not find statistical differences. The group with more possibilities of heart rejection (group 4) presented the highest BNP levels. These data suggest that BNP levels could form the basis for a new, non-invasive screening test to predict acute cardiac allograft rejection.

Normality values of brain natriuretic peptide assessed by radioim-munometric assay in children and adults.

I. Hervás (1), P. Bello (1), V. Castel (2), A. Verdeguer (2), A. Saura (1), P. González- Cabezas (1), D. Flores (1), J.F. Martí (1), A. Mateo (1). (1) Department of Nuclear Medicine. University Hospital, Valenzia, Spain.

AIM: Normality levels of BNP in children are not clearly established. In adults most authors find values in health population between 4+/- 4,8 pg/ml a 26,6 +/- 18,4 pg/ml. It seems that does not exist circadian rhythm and only an author demonstrated that BNP levels were higher in women. The aim of this study is to establish the normality levels of BNP, assessed with the "Shionoria BNP Cis" radioimmunometric assay, in children and adults. METHOD: We have studied the BNP levels of 113 healthy volunteers, 89 children ( age average 1month - 15 years ,47 boys and 41girls) and 34 adults (17 men y 17 women, age mean: 49 years. Children were divided in 3 groups depending on the age: until 5 years, 5 to 10 and 10 to 15 years) and sex. Adults were divide in 2 groups: men and women. BNP mean of each group was calculated and compared using the Student's t test. Statistical significance was considered for p<0,05. RESULTS: BNP means were the following:

A. Total of Children:15 +/-11ng/ml.

Groups of age:

AGE N Mean S.D.

Until 5 n=32 14,83 12

5 to 10 n=33 16,83 11

10 to 15 n=24 12,76 11

Groups of Sex:

N Mean S.D.

Boys n=48 15,9 11

Girls n=41 13,1 9,8

B. Total of Adults: BNP mean16,7+/-16 ng/ml. Women: 23,6+/-17,4ng/ml, Man: 9,7+/-11,7ng/ml.We did not find significant differences between BNP means of children and adults (p=0,51), Children of different age (p=0,48, 0,5 y 0,15) and sex (p=0,22). In Adults we did not find differences between Men and Women (p= 0,1).

CONCLUSIONS: We obtained normality BNP levels similar to the described in the literature. We did not find significant differences in BNP levels of Children and Adults and between the different groups of sex (adults and children) and age (children).

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition PROTEINS AND PEPTIDES

Radiochemical characteristics and infection imaging with UBI 29-41 peptide labelled directly and indirectly with 99mTechnetium

M.M. Welling (1), R. Visentin (2), A. Lupetti (3), U. Mazzi (2), E.K.J. Pauwels (1), P.H. Nibbering (3). (1) Department of Nuclear Medicine, Leiden University Medical Center, Leiden, The Netherlands, (2) Dipartimento di Scienze Farmaceutiche, Universita degli Studi di Padova, Padova, Italy, (3) Division of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.

Objective: We introduced 99mTc-UBI 29-41, a synthetic peptide derived from human ubiquici-dine, to distinguish bacterial and fungal infections from sterile inflammations in animals. This peptide was labelled with 99mTc using a direct method involving mild reduction conditions. Since indirect methods are widely used to label peptides and proteins, we compared the radio-chemical characteristics and the ability to image infections with UBI 29-41 labelled with 99mTc according to the direct method and a method involving a HYNIC moiety, which was introduced into the peptide during its synthesis.

Methodology: HPLC, ITLC, and SepPak analysis were used to analyse the composition of the labelling solutions; carrier-free 99mTc-UBI 29-41 was obtained after HPLC purification. The stability of the various labelled 99mTc-UBI 29-41 compounds was challenged in human serum for 24 hrs. Furthermore, in vitro competition binding studies were carried out to investigate the specificity of the binding of the tracers to bacteria. In addition, we evaluated the ability of these tracers to detect bacterial infections in mice.

Results: Radiochemical analysis of the various labelling preparations revealed that within one hour >95% of the radioactivity was associated with UBI 29-41 and that, after HPLC purification, carrier-free 99mTc-UBI 29-41 preparations were obtained. Good stability (>90%) of the three tracers in serum was observed. All three tracers bound preferentially to bacteria over human cells; the highest values were observed with carrier-free, directly labelled 99mTc-UBI 29-41. Binding of the various tracers was significantly (P<0.01) reduced after pre-incubating the bacteria with 100-times excess of unlabelled UBI 29-41, but not unlabelled control pep-tides. After intravenous injection into mice with a bacterial infection, the various tracers were removed from the circulation by renal clearance (40% ID) and to a lesser extent by the liver (10% ID). Accumulation of carrier-free, indirectly labelled 99mTc-UBI 29-41 in the liver was significantly lower (<5% ID). Unpurified, directly labelled 99mTc-UBI 29-41 and carrier-free, indirectly labelled peptide rapidly detected bacterial infections in mice with target-to-non target (T/NT) ratios of 2.5±0.2 (n=20) at 1 hr after injection of the tracer. Highest T/NT ratios of about 4.2±0.5 (n=14) were observed using carrier-free, directly labelled 99mTc-UBI 29-41. Conclusion: Direct labelling of UBI 29-41 with 99mTc and labelling through the intermediation of the HYNIC ligand resulted in tracers with similar radiochemical characteristics and ability to detect bacterial infections in mice. Carrier-free 99mTc-UBI 29-41 was superior in imaging of infections most likely due to lack of competition by unlabelled peptide.

In vivo evaluation of a peptide identified through random peptide phage display

S. Zitzmann (1), V. Askoxylakis (2), W. Mier (3), M. Eisenhut (4), M. Schwab (5), U. Haberkorn (6). (1) Universitätsklinikum, Dept. of Nuclear Medicine, Heidelberg, Germany, (2) DKFZ, Dept. of Cytogenetics, Heidelberg, Germany.

Aim: Targeting tumor cells by peptides is a promising strategy for delivering radionuclides for cancer therapy and tumor imaging. The identification of new efficient targeting peptides with specific targeting abilities and reduced background binding is still a major challenge in cancer-related peptide research. A prominent example for a homing peptide is the three-amino-acid sequence Arg-Gly-Asp (RGD) motif. RGD-analogues have been used in tumor imaging and tumor targeting with radionuclides or chemotherapeutic drugs. Materials and Methods: The peptide p160 (VPWMEPAYQRFL) [Zhang et al. 2001] has been identified through random peptide phage display techniques. It was labeled with sodium [131I]iodide using the chloramine-T method and purified by HPLC. P160 was monoiodinated on Tyr8 and with the Met4 residue oxidized to methionine sulfoxide. In vivo-studies were carried out in nude mice carrying neuroblastoma Wac2-tumors to investigate the biodistribution of the 131I-labeled p160-peptide in comparison to 131I-labeled Tyr10-RGD-4C and a control pep-tide, 131I-labeled WARGYDTGPSRL.

Results: The organ-distribution demonstrated an enrichment of p160-peptide in the Wac2-tumors (see table for 1 h values). A time course experiment with showed an overall decrease in iodine-labeling with progression of the time. To assess the targeting properties of p160-pep-tide, experiments were conducted with a RGD-4C-peptide as positive control and a negative peptide control. The RGD-4C-peptide showed a similar organ distribution as the p160-pep-tide, except for a higher liver and kidney accumulation.

tumor blood heart spleen liver kidney brain

p160 [%ID/g] 2.25 1.90 0.88 1.33 0.96 2.15 0.11

Tyr10-RGD-4C [%ID/g] 2.62 2.20 1.34 1.37 2.50 28.57 0.12

control peptide [%ID/g] 1.66 4.22 1.13 1.97 1.65 4.03 0.18

Conclusion: The p160-peptide seems to be a promising candidate for a peptide that can be used either for cancer diagnosis and therapy. Its targeting properties seem to resemble the ones of the RGD-4C-peptide while it does not share its extremely high excretion via the kidney. In contrary, the p160-peptide has in most organs except for the tumor a low accumulation which might be favorable for cancer treatment.

Factors influencing the uptake of neurotensin analogues in NT-1 receptor overexpressing tumours

E. Garcia Garayoa (1), B. Holzer (1), A. Blanc (1), M. Lutz (1), P. Bläuenstein (1), D. Tourwe (2), P.A. Schubiger (1). (1) Center for Radiopharmaceutical Science, Paul Scherrer Institut, Villigen, Switzerland, (2) Department of Organic Chemistry, Vrije Universiteit, Brussels, Belgium.

Aim: The favourable features of neuropeptides has boosted the search for new analogues as potential tumour targeting radiopharmaceuticals in the last years. Their short plasmatic halflife is, however, a problem difficult to circumvent since in some cases modifications in the sequence lead to loss of binding affinity and/or agonistic activity. Four neurotensin analogues (NT-VIII, NT-XI, NT-XII and NT-XIII) stabilised at positions 8-9 and 11-12 showed high affinity for NT-1 receptors and high human plasma stability in vitro (t1/2 > 24h). Nevertheless, differences were found in the in vivo tumour uptake. In order to elucidate whether these differences could be due to a different degradation in the tumour, we studied their metabolism and retention after internalisation in HT-29 human colon adenocacinoma cells.

Material and methods: HT-29 cells were used for testing the affinity, internalisation/release and metabolism of the stabilised NT(8-13) analogues in vitro. The metabolites were analysed by HPLC. Nude mice with HT-29 tumour xenografts were used to evaluate the biodistribution and the in vivo tumour uptake.

Results: All the analogues showed a high affinity for NT-1 receptors overexpressed in HT-29 cells. In these experiments, the relative amount of specific bound radioactivity (SB/F) was different for the different analogues. The values of SB/F were in good correlation with the in vivo tumour uptake at the earliest time point tested. After internalisation the activity was released in the form of intact peptide and/or fragments. In the first hours, the fraction of intact peptide was larger in the case of NT-VIII and NT-XII. This released intact peptide can bind again to NT-1 receptors and reinternalise. This is in accordance with the higher tumour uptake found at 5h post-injection for these two analogues. Finally, NT-XI and NT-XII are the pep-tides showing higher retention in tumour cells after 24h which is also in good correlation with their tumour uptake.

Conclusion: A longer plasma half-life is necessary in order to have a sufficient amount of intact peptide at the tumour area. High affinity and, especially, high ratios SB/F are also important since they determine the amount of peptide which can internalise and be processed in the cells. The degradation in the tumour cells is another factor to take into account. The formation of different fragments which can be released more rapidly or retained longer lead to different patterns of biodistribution and tumour uptake.

[111In] benzyl-DTPA-EGF, a new potential radiopeptide for targeting of glioma.

A. Orlova (1), A. Liljegren Sundberg (1), A. Bruskin (2), L. Gedda (1), J. Carlsson (1), V. Tolmachev (1,3). (1) Division of Biomedical Radiation Sciences, Uppsala University, Uppsala, Sweden, (2) RRC ITEP, Moscow, Russia, (3) Department of Organic Chemistry, Uppsala University, Uppsala, Sweden.

Aim: Overexpression of epidermal growth factor receptors (EGFR) in primary glioblastomas is well documented. This enables to use both labelled anti-EGFR antibodies and natural lig-and, EGF for targeting of glioblastomas. Though high level of expression of EGFR in normal liver complicates systemic injection of labelled EGF, the use of locoregional injection gives an opportunity of successful targeting. The use of small (6 kD) EGF might provide better penetration into tumours in comparison with anti-EGF antibodies and their fragments. The aim of the study was to prepare and evaluate in vitro EGF-based anti-glioma conjugate with residualising label.

Materials and methods: Human recombinant EGF was coupled with isothiocyanate-benzyl-DTPA , purified from unreacted chelator using solid-phase extraction, and labelled with 111In. In vitro characterisation using EGFR expressing glioma U-343 MGaCl2:6 cell line included study of binding and internalisation pattern, cellular retention, and binding affinity measurement. Stability in blood plasma was evaluated.

Results: The conjugate was labelled with 111In with yield of 86.9 ± 7.1 %. The label was reasonably stable, a transchelation to blood plasma proteins was about 5% after incubation at 37 oC during 24 hours. The conjugate demonstrated specific binding and quick internalisation of radioactivity. Intracellular retention of radioactivity after interrupted incubation with [111In] benzyl-DTPA-EGF was 71 ± 1 % and 59 ± 1.5 % after 24 and 45 hours, respectively. Dissociation constant was estimated as 9.4 nM.

Conclusion: The results indicate that [111In] benzyl-DTPA-EGF is a possible candidate for targeting of glioblastoma using locoregional injection.

Rituximab radio-iodination and in vivo evaluation towards intended application in repeat radioimmunotherapy.

F. Buchegger (1), A. Schaffland (1), M. Kosinski (1), C. Antonescu (1), N. Ketterer (2), T. Kovacsovics (3), R. Pellikka (4), A. Bischof Delaloye (1). (1) Division of Nuclear Medicine, University Hospital of Lausanne,, (2) Division of Oncology, University Hospital of Lausanne,, (3) Division of Hematology, University Hospital of Lausanne,, (4) Division of Radiopharmacy, Paul Scherrer Institute,Lausanne and Villigen, Switzerland.

Aim: Low immunogenic chimeric anti-CD20 antibody Rituximab was labelled with 131I for biodistribution studies performed repeatedly during standard, but time extended Rituximab therapy.

Methods: Labelling of Rituximab (185, respectively 37 MBq 131I /mg antibody) was performed with chloramine T, immunoreactivity measured on live B-lymphoma cells and 4 patients injected each at 3 different times during Rituximab therapy.

Results: Standardised labelling (185 MBq/mg) for patient study showed efficiency in the range of 91 % to 96 % (with one exception). After purification by ion exchange chromatography, radiochemical purity assessed by TLC (and confirmed by HPLC) was in the range of 98.4 to 99.8 %. Binding measured on ~10x106 fresh Raji or Daudi cells was 48.3 + 9 %, (N=11). Maximal immunoreactivity extrapolated according Lindmo was 70.2 + 16.8 %. Mean blood p T/2 (71.8 hrs) varied among patients (range 64.6 to 82.2 hrs) but remained constant within individual patients (mean coefficient of variation 7.8 %, range 4.0 to 14.1%). The second labelling condition of 37 MBq/mg showed a significantly higher (~20 % binding increase) immunoreactivity when directly compared with 185 MBq/mg labelling. Conclusion: Blood effective p-half-lives of 131I-Rituximab varied between 2.8 and 3.3 days in 4 patients. Half-lives remained constant within individual patients during Rituximab therapy. Antibody labelling with 5 fold lower amounts of 131I per mg antibody gave a significant gain of immunoreactivity. Supported by the Swiss Cancer League.

In-111 Labelled GLP-1 for In Vivo Diagnostic of Insulinomas

M. Behe, T. M. Behr, W. Schmalor, B. Herbst, J. Meier, M. Gotthardt. Philipps-University, Marburg, Germany.

Objectives: Only about 50% of the insulinomas express the sst2 receptor and can be detected by OctreoScan-111. However nearly 100 % of the insulinomas express the GLP-1 receptor which is a promising target for a better diagnostic application with a radiolabelled peptide. Furthermore there are some indications that GLP-1 receptor is expressed on other tumor modalities like medullary thyroid carcinoma or small cell lung cancer. We have developed radioiodinated GLP-1 and Exendin-3 (a GLP-1 receptor agonist) which were used successfully for the detection of insulinomas in an animal model. Since radiometal labelled compounds show a better cell retention an 111In labelled compound is desirable.

Methods: GLP-1 and Exendin-3 were conjugated with DTPA, purified by HPLC, and analysed by MS. The 111In labelled compounds were tested for their metabolic and chelator stability in human serum by HPLC and gel filtration. Internalisation and externalisation studies were performed with H-69 cells (SCLC). The externalised peptides were analysed by HPLC.

Results: Both compounds could be labelled with 370 GBq/?mol with more than 98% chemical purity. The stability studies show a transfer of the 111In to the proteins of 24%-28% after 24 h. 111In-DTPA-GLP-1 shows a hydrophilic metabolite after 24 h, whereas 111In-DTPA-exendin-3 is stable. 72 % and 80 % of the total bound peptide were internalised in the H-69 cells after 2 h. 15 % and 20 % of the internalised compound was externalised after 24 h. Conclusion: We developed two GLP-1 conjugates which can be labelled with high specific activity and high chemical purity with 111In. The peptides show a specific internalisation. The compounds comply the conditions for a successful in vivo application

Preparation of a new Re-186 labelled bombesin-like Pentadecapeptide and Evaluation in Radiotherapy

P. Bouziotis, M. Fani, M. Pelecanou, I. Pirmettis, M. Paravatou, L. Leondiadis, S. Xanthopoulos, S.C. Archimandritis, A.D. Varvarigou.

N.C.S.R. , Athens, Greece.

Technetium, an element belonging to Group 7 of the Periodic Table, has been extensively used in formulating diagnostic radiopharmaceuticals for scintigraphy and SPECT imaging studies in patients. Rhenium, which also belongs to Group 7, exhibits many of the chemical properties of technetium and investigations of rhenium coordination chemistry are often performed in conjunction with technetium, thus providing a non-radioactive alternative to working with technetium radioisotopes. Furthermore, the beta-emitting radionuclides 186Re and 188Re are of great interest to nuclear medicine as they possess physical and nuclear properties favorable for use in systemic radiotherapy. Further studies on the chemistry of technetium and rhenium will eventually lead to the design of suitable backbones that will be used for the optimum labelling of specific peptides and other biomolecules. In a recent study, we have synthesized and investigated a new pentadecapeptide, Bombesin derivative. This new biomolecule, labeled with Tc-99m, was found to localize in colon cancer and in small cell lung carcinoma, experimentally induced in animals, and in breast and prostate cancer in humans. In the present study the formation of a rhenium complex of the same peptide was investigated with two further goals: to investigate the complex structure using non-radioactive Rhenium-185/187 and to evaluate the possible use of the 186Re-complex for breast cancer radiotherapy. For the Re-peptide complex formation, Re-gluconate was initially generated and the metal was exchanged from the gluconate complex to the peptide by heating. In the case of Re-185/187, the complex formed is chromatographically isolated and identified by 1H-NMR and electro-spray mass ionization. On the other hand, labeling with 186Re-gluconate leads to the formation of a single radioactive derivative, with Rt= 13.48 min., which remained stable for at least 24 hours. Cell-binding assays, using different cancer cell lines and biodistribution evaluation in normal and tumour-bearing animals are in progress.

Optimizing of conditions for radiolabeling of DOTA-peptides with 90Y, 111In, and 177Lu at high specific activities

W.A.P. Breeman (1), J.L. Erion (3), T.J. Visser (2), W.H. Bakker (2), E.P. Krenning (2), M. de Jong (2). (1) Department of Nuclear Medicine, Rotterdam, The Netherlands, (2) Department of Internal Medicine, Rotterdam, The Netherlands, (3) BioSynthema, St Louis, MO, USA.

Objectives: DOTA-conjugated peptides, such as [DOTA0,Tyr3]octreotide (DOTATOC) and [DOTA0,Tyr3]octreotate (DOTA-tate) can be labeled with radionuclides like 90Y, 111In and 177Lu. These radiolabeled somatostatin analogues are nowadays in use for peptide receptor radionu-clide therapy (PRRT). Radioligands for PRRT require high specific activities, however, although these radionuclides are produced no carrier added, contaminants are ever present due to production methods and the formed decay products.

Aim: Parameters influencing the reaction kinetics of radiolabeled DOTA-peptides were investigated, as well how to obtain the highest achievable specific activity. The ever present contaminants were systematically investigated concentration-dependently in a test model, mimic-ing conditions of a labeling with minimal molar excess of DOTA-peptides over radionuclide. Results: Reaction kinetics of radiolabeled DOTA-peptides were optimal at pH 4 - 4.5; pH <<4 strongly slowed-down the kinetics. Above pH 5 reaction kinetics varied: at high concentration of the radionuclide the solubility becomes uncertain, due to rapid formation of hydroxides. Labeling with 90Y and 177Lu was completed after 20 min at 80 °C, while labeling with 111In was completed after 30 min at 100 °C. The ever present contaminants are summarized and systematically categorized, e.g. Zn, is the target and decay product of 67Ga, and will therefore always be present, and it was found to be a heavy competitor for 67Ga for the incorporation in DOTA. Radiolabeling DOTA-peptides at high specific activities with 67Gaand 111In is possible, but is hampered when the time interval between production of the radionuclide and use for labeling increases, due to the ingrowth of the formed decay products, i.e. Zn and Cd, resp. In contrast, Zr and Hf, decay products of 90Y and 177Lu, resp, do not interfere in this incorporation.

Conclusions: Reaction kinetics differ per radionuclide, and labeling at high specific activity can be hampered by the formation of decay products.

Quality control of radiopharmaceuticals used for sentinel node detection by dinamic light scattering method

A. Polyak, K. Bodo, L. Balogh, G. Andocs, R. Kiraly, D. Mathe, GY.A. Janoki. National Center for Public Health, National Research Institute for Radiobiology and Radiohygiene, Budapest, Hungary.

Aims: Localization and pharmacokinetics of colloid radiopharmaceuticals depends on the particle sizes. In our experiments we used a new laser scattering method for determination the sizes of nanometer-range to colloids.

Samples tested were HAS colloids with different particle size and wide clinical use. (Nano-Albumon® (50-70 nm) and Senti-Scint® (100-600 nm) - N.R.I.R.R., Hungary) Material and Methods: The analytical instrument used in our experiments named DynaPro is a product of the PROTEINSOLUTIONS Inc. (USA). The sample is illuminated by a semiconductor laser of ~830 nm wavelength. The light scattered by the sample in the cell is collected and guided via a fiber optic cable to an actively quenched, solid state Single Photon Counting Module (SPCM). The photons are then converted to electrical pulses and correlated. The DynaPro analyses the time scale of the scattered light intensity fluctuations by a mathematical process called autocorrelation. The translational diffusion coefficient (D) of the molecules in the sample cell is determined from the decay of the intensity autocorrelation data. The hydrodynamic radius (R) of the sample is then derived from D, using the Stokes-Einstein equation.

The DynaPro determines the uniformity of sizes through a monomodal (single particle) curve fit analysis, which assumes a single particle size with a gaussian distribution. If the sample is found to be polydisperse or non-monomodal using the monomodal assumption, the user can then perform additional analysis with DYNAMICS software to resolve a bimodal size distribution.

Results: Low sample volume (50^l) needed for determination, which offers possibility for serial measurements of labelled and inactive colloid material. Examination of protein-based colloids has proven that they are low level dynamically transforming systems for the most part. As we examined samples of Senti-Scint® and Nano-Albumon® radiopharmaceuticals during production and after liophilization (freeze-dried form), we could see the particle size distribution changes caused by the latter process. These measurements indicated an average increase up to 50% after the liophilization (Senti-Scint®: appx. 100 nm to appx. 150 nm). We also examined the stability of the colloid products (hourly and daily sampling - storage at 4°C, RT and at extreme high 50°C temperature). These protein-based radiopharmaceuticals showed high particle and radiochemical (>95%) stability at 4°C and room temperature storage.

Conclusion: The instrument is proved to be fast, simple but exact method to determinate colloid size which is an important task in quality control or during development of new radio-pharmaceuticals.

Synthesis and isolation of phenolic esters of DOTA

W. Mier (1), T. Schauer (1), U. Haberkorn (1), M. Eisenhut (2). (1) Universitätsklinikum, Dept. of Nuclear Medicine, Heidelberg, Germany, (2) German Cancer Research Center, Division of Radiochemistry and Radiopharmacology, Heidelberg, Germany.

Aim: Bifunctional chelating agents have been shown to be potent ligands used for radiometal labeling of molecules such as peptides and antibodies. Therefore, there is strong interest in the development of these agents for the application of radioactive metals towards „targeted" diagnosis and therapy of cancer. Due to their high in vivo stability and ease of labeling with different radionuclides, DOTA-conjugates offer advantages over other conjugated bifunctional chelating agents. However, convenient protocols for the preparation of DOTA-conjugated bio-molecules with high synthetic yields are still warranted.

Methods: As compared to NHS-esters, phenolic esters offer the advantage of high stability in aqueous solution combined with the favorable UV-detection due to the aromatic chromophor. The properties of the condensing agents 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide x HCl, diisopropylcarbodiimide and dicyclohexylcarbodiimide were compared. The phenolic esters of DOTA were prepared using stoichiometric amounts of DOTA, carbodiimide and respectively 2,3,4,5,6-pentafluorophenol, 2,3,5,6-tetrafluorophenol, 2-nitrophenol, 3-nitrophe-nol or 4-nitrophenol in aqueous solution containing acetonitrile.

Results: Under these conditions, the mono-activated phenolic esters could be formed with surprisingly high selectivity. Separation was carried out by preparative RP-HPLC using water with a linear gradient from 0 to 60% acetonitrile as eluent. The eluates were lyophilized and stored at -20 °C. The ability to conjugate the different phenolic esters was investigated with model compounds in solution and on a solid support. In both cases, high yields of the DOTA-conjugates could be obtained.

Conclusion: In summary, this method transforms the commercially available DOTA to highly useful active esters. The purification of these active esters can be performed with HPLC to yield the pure active esters, which can e.g. be used for the preparation of labeling kits. The stability of these active esters is ideal for the development of optimized protocols for an efficient, controlled conjugation to proteins, peptides and other molecules of biological interest, without the necessity of subsequent removal of protecting groups.

Preclinical evaluation of two newly developed somatostatin analogs labeled with indium and yttrium

M. Laznicek (1), A. Laznickova (1), F. Trejtnar (1), H. R. Macke (2), K. Eisenwiener (2), J. C. Reubi (3), S. Wenger (3). (1) Faculty of Pharmacy, Charles University, Hradec Kralove, Czech Republic, (2) University Hospital, Basel, Switzerland, (3) University of Bern, Bern, Switzerland.

The application of radiolabeled receptor-specific peptides to target somatostatin receptors on tumor cells represents a valuable method for the imaging of various neuroendocrine tumors. There is also a possibility to label octreotide analogues with an appropriate radionuclide for cancer therapy. In case the somatostatin receptor-positive tumors with good uptake of gamma-radiolabeled octreotide analog have been visualized, a replacement of a diagnostic radionu-clide with a beta-emitter such as yttrium-90 could be used for the peptide receptor radionu-clide therapy. In the present work, biodistribution and elimination mechanisms in rats of two new somatostatin analogs labeled with In-111 and Y-88 is presented. Both peptides under study, DOTAGA-Tyr3-octreotate (DOTAGA-tate) and DOTA-t-GA-Tyr3-octreotate (DOTA-t-GA-tate) have shown very high binding affinity to somatostatin receptor subtypes in in vitro experiments. Peptide radiolabeling with In-111 and Y-88 (as a substitute of Y-90) was performed using a bifunctional chelating method. For biological experiments, male Wistar rats were used. For the analysis of elimination mechanisms, the perfused rat liver and perfused rat kidney in situ were employed. In-111 labeled DTPA-octreotide was used as a standard agent. The results showed rapid blood clearances and similar biodistribution profiles of all peptides under study in most rat organs and tissues. High and long-term uptakes of radioactivity in the main elimination organ (the kidney) and also in somatostatin receptor-rich organs (the adrenals and pancreas) were found. Surprisingly, significantly higher kidney uptake of radioactivity after administration of the peptides labeled with radioindium when compared with that of radioyttrium was determined. Radioactivity concentrations in organs with high density of somatostatin receptors were substantially higher for the new peptides under study in comparison with In-DTPA-octreotide; the highest values for radiolabeled DOTAGA-tate were determined. The main elimination pathway for all peptides under study was urine excretion. Perfused rat kidney experiments showed that the peptides were eliminated mostly by glomerular filtration. Bile clearance of radioactivity in the perfused rat liver experiments was very low for all agents. The results showed that the octreotate derivatives under study are promising ligands for visualization and treatment of somatostatin receptor-positive tumors. According to the presented results, the most promising agent in this field seems to be DOTA-GA-tate.

The study was created under the support of program COST B12 of EU and partly supported by the grant No. 264/2001 of Grant Agency of Charles University.

Biodistribution of radiolabeled antimicrobial peptides and rapid detection of infection in rats.

T.P. Prangere (1), O. Madar (1), J.L. Dimarcq (2), F. Tiberghien (2), J.P. Meyer (2), M. Steinling (1). (1) Institut of Nuclear Medicine, CHRU de Lille, Lille, FRANCE, (2) ENTOMED S.A., Illkirch, France.

We have labeled 4 different antimicrobial peptides and studied in vitro their binding to the membrane of bacteria. The aim of this work was to study this radiotracer for the detection of infected sites.

Material and methods: 4 peptides isolated from insects, Thanatine, Androctonine, Helio-mycine and ARD, were succesfully labeled either by iodine or by Tc99m. We injected first 3.7MBq of this labeled peptides in normal rats to study their biological distribution. For this, we used a gama camera and a dynamic sequence acquisition of the first hour followed by static images of 10 minutes at 2, 3 and 4 hour.

After this biodistribution studies, we developed an experimental infection of the right thigh muscle by intramuscular injection of 0.2mL of a solution of 109 CFU of S.aureus or P.aerugi-nosa. The same imaging study was performed 24 hours later .

Results: In the biodistribution studies, we have seen an important difference beetween the two labeled methods. There is a rapid metabolisation of the radioiodine peptides, this is showed by the visualisation of the thyroid and the stomac since the 30th minute, this activities growing with the time. The labeling with Tc99m is more stable in vivo, even 4 hours after injection.

The diffusion of the radioactivity of the body is homogenous, peptides are eliminate mainly by the kidneys.

In the infection studies, the site is visualized in the first minutes after the injection and the maximum is obtain around the 30th minute and became stable after this time. The best results are obtained with the Thanatine with a Target/nonTarget ratio of 4/1.

Conclusion: This preliminary results in rats lead us to conclude that the use of radiolabeled antimicrobial peptides is an interesting way of study for the rapid detection of infection. More peptides must be explored to select the best one and other infection models must be studied.

% of injected dose (mean ± sd, n = 5) 99mTc-tricine-Hynexin 99mTc-EDDA-Hynexin

Organ 10 min p.i. 60 min p.i. 10 min p.i. 60 min p.i.

urine 0.3 ± 0.3 2.5 ± 0.5 0.2 ± 0.2 2.1 ± 0.9

kidneys 25.6 ± 6.9 38.3 ± 3.3 43.0 ± 2.6 51.8 ± 7.0

liver 29.1 ± 2.9 28.4 ± 2.4 15.9 ± 1.5 18.8 ± 4.8

spleen 4.7 ± 0.9 4.5 ± 0.7 2.2 ± 0.3 3.2 ± 1.1

intestines 2.9 ± 0.2 2.9 ± 0.7 3.5 ± 0.2 3.0 ± 0.4

lungs 4.2 ± 0.6 2.8 ± 0.8 3.3 ± 0.3 2.6 ± 1.3

blood 24.0 ± 3.0 6.3 ± 0.3 24.5 ± 2.1 5.1 ± 0.8

Influence of the co-ligand on the labelling and biodistribution of Tc-99m labelled Hynic-Annexin V

K.A. Verbeke (1), D. Kieffer (1), J.L. Vanderheyden (2), N. Steinmetz (2), A. Green (2), A. Verbruggen (1). (1) Laboratory of Radiopharmaceutical Chemistry of the K.U.Leuven, Belgium, (2) Theseus Imaging Corporation, Boston, MA, USA.

Aim: 99mTc-labelled Hynic derivatized Annexin V (99mTc-Hynexin) has been developed as a new radiopharmaceutical for the evaluation of apoptosis in vivo. Standardly, tricine has been used as the co-ligand for labelling Hynexin with 99mTc, resulting in a preparation which shows a rather high degree of renal retention and a relatively low urinary excretion. In this study, we have investigated whether ethylene diamine diacetic acid (EDDA) could be used as an alternative co-ligand and to what extent this co-ligand would alter the biodistribution of the 99mTc-Hynexin preparation.

Materials and methods: rh-Annexin V (AV) was reacted with Hynic-N-hydroxysuccinimide ester in a 1/5.5 molar ratio at pH 7.4 and a protein concentration of 1 mg/ml in order to obtain Hynexin with 0.5 Hynic per AV. Labelling with 99mTc was performed by addition of either tricine (1.5 mg) or EDDA (5 mg), SnCl2.2H2O (20 |ig) and 99mTcO4- (370 MBq, 1 ml) to Hynexin (93 |g) at pH 5.2. Preparations with tricine were incubated at room temperature whereas the ones with -EDDA were incubated at 37 °C. All preparations were analyzed with ITLC using respectively acetone, ACD (0.068M citrate, 0.074M dextrose, pH 5.0) or 12% TCA as the mobile phases. Size-exclusion FPLC was performed on a Superdex HR 75 column. The tissue distribution of FPLC-isolated 99mTc-Hynexin was evaluated in normal mice at 10 min and 60 min p.i (approximately 2.5 ng of Hynexin per mouse).

Results: When tricine was used as co-ligand, labelling yields of Hynexin were consistently high (>90%). On the other hand, radiochemical yields of 99mTc-EDDA-Hynexin were only 28% after 20 min and 35% after 60 min incubation. The results of the biodistribution study are summarized in the table and indicate that both 99mTc-Hynexin preparations exhibit a relatively rapid blood clearance and are predominantly taken up in the kidneys and to a lesser extent in the liver. Although the fraction of the activity in the kidneys is significantly higher for 99mTc-EDDA-Hynexin than for 99mTc-tricine-Hynexin at both time points, the fraction of injected activity that appears in the urine remains very small.

Conclusions: Despite the higher renal uptake and lower liver accumulation obtained with 99mTc-EDDA-Hynexin as compared to 99mTc-tricine-Hynexin, EDDA seems not to be a valuable co-ligand for the preparation of 99mTc-Hynexin, because of the low labelling yields and because it does not result in a higher urinary excretion.

Parameters for labelling DOTA-lanreotide with Gallium-67

E.B. Aldegueri, B.L. Faintuch, J.A. Osso Jr.. Institute of Energetic and Nuclear Research, Sao Paulo, Brazil.

Objectives: Lanreotide is an octapeptide somatostatin analogue that conjugated to the macro-cyclic chelant DOTA binds to a large variety of human tumors, including neuroendocrine malignancies, lymphomas, and non-small-cell lung cancer. DOTA is an almost universal chelator capable of strongly encapsulating hard metals such as 111In and 67Ga for SPECT, 68Ga, 86Y and 64Cu for PET, as well as 90Y for receptor-mediated radionuclide therapy. The aim of this study was to evaluate different parameters for labelling DOTA-Lanreotide (DOTALAN) with 67Ga, such as mass of conjugated peptide, pH, specific activity, reaction time, and radio-chemical stability.

Methods: Labelling studies were performed varying mass of DOTALAN (10 to 50 ^g), 67GaCl3 (10 to 100 mCi), pH (2 to 6), and reaction time (10 to 30 min), whereas radiochemi-cal stability was documented (1 to 72 hours). A small volume (30 uL) of 67GaCl3 was employed in 0.5 M ammonium acetate buffer (pH 5.2). This solution was added to the ligand DOTALAN and the mixture was heated in boiling water with stirring. Radiochemical purity was checked by means of thin layer chromatography on different supports and mobile phases and also by Sep-Pak C18 cartridges and HPLC.

Results: Radiochemical purity of 98.9 ± 0.4% was obtained with specific activity of 1mCi/ ^g. With a half of the specific activity radiochemical purity was 81.79 ± 2.34%. Amass of 20 ^g of DOTALAN was enough to obtain the best result, in a pH of 4.5, after 15 min of heating. For a mass below 20 ^g only 30% of the ligand was labelled.

Conclusion: DOTALAN was efficiently labeled with 67Ga when defined conditions were observed such as high specific activity, small volume and high temperature. After the success of this procedure is confirmed by biologic studies, application of 67Ga-DOTALAN for diagnosis of patients with somatostatin receptor-positive lesions should be considered.

Satumomab Pendetide: Preliminary evaluation for therapeutic use.

N. Urbano, S. Modoni, M. Di Bari, V. Frusciante. Department of Nuclear Medicine of the Hospital Casa Sollievo della Sofferenza, Scientific Institute, San Giovanni Rotondo, Italy.

Oncoscint® CR103, an immunoconjugate produced from a murine monoclonal antibody, MAb B72.3 (satumomab pendetide), recognizes a high molecular weight tumor-associated glyco-protein (TAG-72) expressed by different neoplasms. It is usually and successfully used as an immunoscintigraphic agent radiolabelled with Indium-111 chloride.

Aim: The present study was undertaken to determine whether this antibody, with its oxidized oligosaccharide component covalently coupled to glycyl-tyrosyl-(N-?-diethylene-triamine-pentaacetic acid)-lysine hydrochloride (GYK-DTPA.HCl), which acts as linker-chelator, may be also effectively labelled with Yttrium-90 in order to encourage a possible therapeutic use. Physical (E?max= 228 MeV) and radiobiological features make Yttrium-90-satumomab pen-detide well suited for radioimmunotherapy.

Since Indium-111 and Yttrium-90 have similar coordination chemistry and metabolic handling, the first could be used as a surrogate marker for Yttrium-90, lacking of gamma ray emission, to trace its biodistribution and dosimetry.

Methods and Results: In our center we tested the labelling of this agent with a sterile, pyro-gen-free Yttrium-90 chloride solution (0.5 ml) with a radioactive concentration of 1480 MBq (40mCi)/ml and specific activity of 20mCi/mg of antibody. In order to minimize radiation exposure, personnel - tools contamination and loss of radioisotope, sterile, pyrogen-free solution of 1 mg of satumomab pendetide in 2 ml of phosphate buffered saline solution (pH 6), was slowly transferred to the Yttrim-90 vial buffered with 0.1 ml of 0.5 M sodium acetate solution (pH 6). Precautions against radiations and proper aseptic techniques were maintained. After incubation at room temperature for 60 minutes with continuous agitation, we determined its radiochemical purity (RCP) by means of an instant thin layer chromatography-(ITLC). This procedure involves the use of ITLC-SG paper (Gelman Instruments, Ann Arbor, MI, USA) cut into 1.5 x 16 cm strips and 0.9% NaCl as solvent system. 70 ?l of 0.05 M DTPA solution were mixed with the same amount of Yttrium- labelled antibody. 3 ?l of this mixture were placed at the strip origin and eluted with saline.

For radioactive measurement we used a scanning radio-chromatography detection system (Bioscan, Inc. Washington, DC). Radiochemical purity was greater than 95%. Conclusion: These preliminary data suggest that this monoclonal antibody may be efficaciously labelled with Yttrium-90 and perhaps therapeutically used, although further improvements are needful.

Radiolabeling of antimicrobial peptides and in vitro study of their binding to the cell's membrane of bacteria.

T.P. Prangere (1), O. Madar (1), J.L. Dimarcq (2), F. Tiberghien (2), J.P. Meyer (2), M. Steinling (1). (1) Institut of Nuclear Medicine, CHRU de Lille, Lille, (2) ENTOMED S.A., Illkirch, France.

Antimicrobial peptides interact directly with the microorganism and they can be potential tracers for imaging of infection. The aim of this study was to develop the labeling of some of this peptides and to test the binding of the labeled compounds on the membrane of different bacteria.

Material and methods:

- 4 peptides with different structures and variable antimicrobial activities have been studied: Thanatine, Androctonine, Heliomycine and ARD.

- Because of the presence of tyrosine in the composition of this peptides we tried first a labeling with iodine by an iodogen method. In a second time, we tested the labeling method described by Welling and al. with Tc99m.

- The labelings are purified by Sep-Pak and the radiochemical purities were controled by HPLC.

- The binding of the labeled peptides was studied by contact with S. aureus or P. aeruginosa followed by filtration to separate free to bind peptides.

Results: For a same peptide, we don't find any difference beetween results obtained by the two labeling methods : we have from 40 to 80% of labeling, this percentage began superior to 95% after the purification.

For the binding assays, the best results were obtained for Thanatine and Heliomycine. Conclusion: This first results lead to conclude that this antimicrobial peptides can be tested for the detection of infection. The second step is to perform some studies in infected animals.

Synthesis, radiolabelling and biodistribution studies of the P149-QY peptide - potential ligand for hAFP receptor

P. Garnuszek (1), I. Licinska (1), M. Mirowski (2). (1) Department of Radioisotopic Drugs, Drug Institute, Warsaw, Poland, (2) Department of Pharmaceutical Biochemistry, Medical University,TodZ, Poland.

Introduction: The receptor for human alpha-fetoprotein (AFP) has been detected in proliferating fetal and tumour cells. Therefore, radioiodinated AFP has been successfully utilised in RIA method for clinical diagnosis of fetal disorders likewise some types of human tumours. Recently, molecular studies has revealed that 34 aminoacid fragment 447-480 of hAFP (P149) retains the anti-estrogenic and anti-tumour activities of parent AFP glycoprotein. The aim of our study was to syntethise the effective analogue of P149 peptide labelled with radionuclides of iodine (125I, 131I) and technetium-99m with intention of potential application for diagnosis and internal radiotherapy of the AFP positive tumours.

Methods: F-MOC Solid Phase Synthesis technique has been applied for synthesis of P149-QY-COOH, modified fragment P149 of human AFP. The radioiodinated peptide was prepared by chloramine-T method using Iodo-beads®, following by purification on PD-10 column. Labelling of the peptide with technetium-99m was performed by the direct method in the presence of stannous chloride. The comparative biodistribution studies of the radiolabelled species of P149-QY-COOH peptide and 131I-AFP were done in tumour-bearing C3H/W mice. Results: Introduction of tyrosine molecule to P149 peptide enabled preparation of radioiodinated peptide with ca. 50% yield. Biodistribution studies of 125I-P149-QY-COOH in tumour-bearing mice showed a higher pharmacokinetics rate of the peptide compared to radioiodinat-ed molecule of AFP, which similarly to other radiolabelled macromolecules showed a high retention in blood. A moderate uptake of the radioiodinated peptide in the tumour tissue was observed (3.2% ID/g 30-min p.i.v). However, the higher rate of radioactivity clearance from normal tissue effected in increasing the target to non-target ratio, i.e. from 2.3 %ID/g 30-min p.i.v. to 3.4 %ID/g 24 h p.i.v, and that suggest the specific mechanism of the tracer accumulation in tumour. The peptide labelled with Tc-99m revealed the highest accumulation in kidney (70%) and low concentration in tumour tissue, pointing out that its pharmacokinetics is regulated by the presence of -SH functional groups.

Conclusions: Radioiodinated P149-QY-COOH peptide reveals some positive feature as the AFP receptor radiopharmaceutical. However, some additional structural modification of the initial peptide molecule is needed for fully retention of the ligand-receptor interaction of its radiolabelled forms. This could be achieved by introduction to the sequence some additional aminoacids, and by the protection of -SH groups. Therefore, terminally introduced lysine, for instance, would enable the advantageous conjugation of bifunctional technetium-99m chelate obtained ex situ.

Determination of specific binding-characteristics of 111In-DTPA-DGlu1-minigastrin in rats pancreas carcinoma cells (AR4-2J)

A. Pethe (1), M. Behe (2), G. Bollmann (3), G. Gademann (3), H.-J. Otto (1). (1) Nuclear Medicine Clinic of Otto-von-Guericke-University Magdeburg, Magdeburg, Germany, (2) Nuclear Medicine Clinic of Philipps-University Marburg, Marburg, Germany, (3) Radiation Therapy Clinic of Otto-von-Guericke-University Magdeburg, Magdeburg, Germany.

Aim: 111In-DTPA-DGlu1-minigastrin (111In-DTPA-MG) is used to diagnose gastrine-receptor-positive tumours (medullary thyroid carcinomas > 95%). The aim of the presented study is to determine the IC50-value. Depending on different concentrations of 111In-DTPA-MG the specific binding-characteristics will be investigated in the carcinoma cell-line AR4-2J and the specific non-internalised part of the receptor-ligand-binding will be quantified. To investigate the binding to the cell, the marking-reaction had to be optimised before concerning the yield. Materials and Methods: Because of their high gastrin-expression AR4-2J-cells are used in the presented binding experiments. The peptide MG was labelled with carrier-added 111In in 0.5 M sodium-acetate (pH 5.5). After that the labelled peptide was purified by means of a C-18-cartridge. The cells were incubated with labelled peptide of different concentration for an one hour period.

Results: The IC50 of the peptide is in the low nanomolar range.

Conclusion: Only purified 111In-DTPA-MG should be used to determine the non-internalised part of the binding. The wide spread of the results can be explained by the very low pulserates caused by the small amount of non-internalised bindings. One way to overcome this problem could be found in a further optimisation of the preparation- technique. It could be shown that the In-111-DTPA- MG has an affinity in the low nanomolar range to the gastrin receptor.

Evaluation of different radioiodination techniques of Rituximab

H. Eidherr (1,3), H. Viernstein (2), A. Becherer (1,3), K. Kletter (1,3), R. Dudczak (1,3). (1) Department of Nuclear Medicine of the University of Vienna, Vienna, Austria, (2) Institute of Pharmaceutical Technology and Biopharmacy of the University of Vienna, Vienna, Austria, (3) Ludwig Boltzmann - Institute of Nuclear Medicine, Vienna, Austria.

Evaluation of different iodination radioiodination- techniques of Rituximab for future application in Radioimmunodiagnosis (RID) and Therapy (RIT) at Vienna.

Aim: Rituximab is an chimeric monoclonal antibody (MoAb), targeted against CD20, an surface antigen present on the surface of various B-cell lymphomas. RID and Radioimmunotherapy (RIT) using 131I-labelled Rituximab areis regarded as a promising novel modality. therapeutic and diagnostic regimens in various malignant diseases. 131I-anti-CD-20 (Rituximab) is an agent, targeted against B-cell surface antigen. Iodogen-iodination was selected because of mild oxydation whereby proteins keep their immunoreactivity with the radioiodine properly built into the biomolecule. Three This study compares three different labellinglabelling methods were employedprotocolsmethods of Rituximab. Material and Methods: In all 3 methods Iodogen was used. for iodination in all 3 protocols because of its mild oxidation whereby antibodies keep their immunoreactivity. Method ProtocolMethod 1 uses Pierce® iodination tubes containing coated with 50 |g iodogen. inside as a film. 1 mg MoAb in 0,.1 ml antibody solution (1 mg MoAb). and 40 to 60 MBq radioiodine 131I in 0,.6 ml PBS are injected through the septum into the tube. After 5 min incubation at room temperature under gentle shaking the reaction is stopped by adding 1 mg potassium iodide iodide and 2 ml 20 % anion exchange resin. After 1 min tThe solution is passed through a 0,.22 |m filter. Method ProtocolMethod 2 is based upon on an one one-pot- method (Behe, Behr, et al.). Glass vials are manually coated with 500 |g iodogen; a little magnetic stir bar is inserted, and the vial is recapped with a stir bar inside; . 0,.1 ml MoAb-solution (i.e. 1 mg MoAb), and up to now 370 MBq 131I-NaI (in 0,.1 ml 0,.05 M NaOH), is added;and for neutralization 1 ml 0,.5 M PBS and 1 ml 0,.05 M phosphate bufferPBS (pH 7.4) are added,. then and tThe reaction mixture is stirred for 5 to 10 min at room temperature20° C (at elevated temperatures the volatile iodine goes into the gaseous phase and no iodine incorporation occurs). Unbound iodide is eliminated by 2 ml 20 % anion exchange resin. (for eliminating the excessive not incorporated iodide) and aAfter 3 min stirring, as a protectant against radiol-ysis and for proper chromatographic results, 1One ml albumin (HSA: a protectant against radiolysis and for proper chromatographic results) are is added and subsequently the mixture is passed through a 0,.22 |m filter. Method ProtocolMethod 3 is a semi-automated procedure (Schirbel, Reiners, et al: .). all All solution transfers occur by a pressure gradient by pushing and pulling two syringes simultaneously. 370 MBq 131I-NaI and subsequently 0.1 ml MoAb (1 mg) is put intoare sent to the Iodogen- reaction-vial by an afterloading method; . the solution is transferred into the reaction vial via the activity vial; . after After 20 min incubation time the mixture is purified on a PD-10 column; then the solution and is passed through a 0,.22 |m filter. Common medical threeCommercially available 3-way way valves and tubings were are employed for this single-use- apparatus. In all 3 methods free iodide is eliminated quantitatively by anion exchange resin. Radiochemical purity is checked by HPLC and ITLC. Results: Yields are approximately 40% ( with method method 1), 65 % (method with method 2) , and 20 % (method 3)with method 3. All methods achieve a rwith sufficient radiochemical purity of of at least 90 % for all methods. Albumin as used in (see method 2) protects from radiolysis and is necessary for proper chromatographic results.

Conclusions: The mild oxidant Iodogen preserves MoAb immunoreactivity. Handling safety is best in method 3 followed by method 2. Method Method 1 is restricted to small activities of long-lived radionuclidesto small activities, especially to of 125I as proposed by the manufacturer of the vialstubes, since much manipulation is required. The advantage of Method 3 is its remote control systeme. However, Due to toobecause long tubings and big void volumes are necessary, yields are small.: Magnetic valves and shorter tubings would be necessary; at this moment only easily implemented method 2 is applicable Thus, only method 2 provides sufficient yields greater 50 % and is feasible without special equipment..

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition PET RADIOCHEMISTRY

Synthesis and evaluation of new glucose conjugated O6-methyl-guanine-DNA methyltransferase (MGMT) inhibitors for in vivo determination of MGMT-status in tumour tissue

R. Schirrmacher (1), U. Muehlhausen (1), B. Waengler (1), E. Schirrmacher (1), J. Reinhard (2), B. Kaina (3), F. Roesch (1). (1) Institute of Nuclear Chemistry, University of Mainz, Mainz, (2) DKFZ, Section Molecular Toxicology, Heidelberg, (3) Devision of Applied Toxicology, Institute of Toxicology, University of Mainz, Mainz, Germany.

Aim: Following our first approach to determine the level of MGMT in tumour tissue using using 18F-labelled derivatives of O6-methylguanine, the aim of the present study was to syn-thesise and evaluate new 18F-fluorinated glucose-conjugated MGMT-inhibitors for the in vivo determination of the MGMT-status of tumour tissue. The human DNA repair protein O6-methylguanine-DNA methyltransferase plays a critical role in cancer therapy with alkylating reagents such as alkylnitrosoureas and alkyl triazenes. Tumour cells and neoplastic tissue with elevated MGMT levels can be resistant to alkylating therapeutics. To quantify the MGMT-sta-tus could be helpful in finding the appropriate cancer therapy. Although potent inhibitors of MGMT have been found and introduced into adjuvant therapy, in all cases no selectivity for neoplastic tissue has been achieved and all showed poor water solubility, which limits their applications. Recently, two MGMT-inhibitors were labelled with [18F]fluorine and [131I]iodine but without glucosidation1. Glucosidation represents a general strategy for improving both drug solubility and targeting. Thus, appropriate glucosyl derivates of MGMT-inhibitors might provide targeted depletion of MGMT activity in neoplastic tissue while the uptake in normal tissue is minimised.

Material and Methods: Several fluorine containing potential MGMT inhibitors have been synthesised. Their ED50 doses were determined by incubation of the compounds for 4 h in HeLa S3 cells. Data were obtained from plots of % MGMT activity remaining versus dose of test compound over a dose range of 0.1-200 |M. Inhibition of MGMT activity by the compounds was investigated using HeLa S3 cell extracts (150 |g protein per essay). Results: The most promising compound was identified to be 6-(2-fluoro-pyridine-4-ylmethoxy)-9-(octyl-a-D-glucosyl)-purin-2-ylamine. For this compound, an ED50 of 1.2 |M was determined. For the synthesis of the corresponding 18F-analogue, the labelling precursor was synthesised. The radioactive labelling with [18F]fluoride gave a radiochemical yield of 40 % after one minute reaction time in DMF at 80°C by using the corresponding chloro precursor. The purification was achieved using HPLC and the radiopharmaceutical was obtained in an ethanolic saline solution.

Conclusion: We synthesised new 19F-fluorinated O6-substituted glucose-conjugated guanine derivatives. Among these compounds 6-(2-fluoro-pyridine-4-ylmethoxy)-9-(octyl-a-D-gluco-syl)-purin-2-ylamine was shown to have the highest MGMT affinity. The corresponding 18F-compound was synthesised in moderate radiochemical yields, purified and shortly to be evaluated.

[1] Vaidyanathan G. et al. Bioconjugate Chem. 2000, 11, 868-875

(R)-[O-methyl-11C]metomidate may be superior to [18F]-FDG for PET imaging of metastases from adrenocortical origin

M. Mitterhauser (1,2,3), G. Dobrozemsky (4), W. Wadsak (3), G. Zettinig (3), H. Viernstein (2), I. Zolle (3), K. Kletter (3), R. Dudczak (3). (1) Anstaltsapotheke des AKH Wien, Isotopenapotheke, (2) Inst. für Pharmazeutische Technologie und Biopharmazie, Universität Wien, (3) Univ.-Klinik für Nuklearmedizin, AKH Wien, (4) Inst für Biomedizinische Technik und Physik, Universität Wien, Austria.

Synthesis and Quality-control of (R)-[0-methyl-11C]metomidate for PETAim: (R)-[O-methyl-11C]metomidate (MTO) is a tracer designed for the identification of adrenocortical lesions. The target enzyme is P450 11-ß, being overexpressed in incidentalomas of the adrenal cortex.

Since 6 months we use MTo for imaging of adrenocortical lesions, especially incidentalomas. The purpose of this study is to evaluate PET with the tracer 11C-metomidate as a method to identify adrenal cortical lesions. A fast and feasible synthesis and quality control was developed for this 11-b-hydroxylase inhibitor for PET.

Materials and Methods: (R)-[O-methyl-11C]metomidate MTO was prepared by the reaction of 11C-methyl iodide with the tetrabutylammonium salt of the free acid (1mg) of metomidate as precursor. The salt was prepared by dissolving 1 mg of the acid in 100300^l dichloromethane DMF under addition of 5.2^l of 0.77M tetrabutylammoniumhydroxide, evaporation of the solution to dryness and reconstitution of the precursor in 300^l DMF. The 11C-methyl iodide was trapped in this DMF-solution and the methylation reaction was carried out at 130°C for 4 minutes. After addition of water the product was purified with awith additional preparative HPLC (^Bondapak C18 5^m 200mm x 10mm acidic , flow 6ml/min, wavelength 254 nm, solvent 0.3M HCl in saline/Ethanol 65/35). The product fraction was diluted with salineethanolic phys. saline) and sterile filtrated filtration (Millipore 0.22^m) for the purification.

Quality control was performed with analytical HPLC (C18 ^Bondapak, , flow 1ml/min, wavelength 254nm, solvent 50mM ammoniumformiate buffer). pH3.5/acetonitrile:water (50:7) 40/60) and residual solvents by GC GC analysis on residual solvents showed no remaining residues in the applicable solution and osmolality and pH were measured. The acquisition protocol was performed according to an ongoing multicenter trial (CoST-B12) using MTO in the diagnosis of incidentalomas (Uppsala University, Turku PET Center). Dynamic images of liver and adrenals were acquired up to 45 minutes after application of 800 MBq tracer.

Until now we studied 9 patients. Among these patients two had metastatic desease of an adrenocortical tumor. Both patients had FDG-PET within one week of the MTO study. Results: The uncorrected yields of (R)-[O-methyl-11C]metomidate wereUsual labelling results are: yield 53-106% (corresponded to EOB), synthesis time: 40minspecific activity 500Ci/mmol), whereas highest losses of activity confer to the transformation of the [11C]- carbondioxide to [11C]-methyl iodide (~50%). The radiochemical purity is higher than> 97%, where the main impurities appear as [11C]-methanol and [11C]-methyl iodide are within the thresholds.

In both patients No residual solvents (DMF, Dichloromethane) could be detected in the final product, because of they were completely removed by the preparative HPLC.with adrenocor-tical tumor metastases (lung, diapragm, jejunal mesenterium) were outlined clearly on MTO images. Comparing MTO and FDG studies, MTO demonstrated better uptake of the tracer and showed additional lesions not depicted by FDG. SUV ranged from 5.8 to 16.3 for MTO and from 1.9 to 5.4 for FDG.

Conclusions: The adopted and improved synthesis method allows the fast routine support of MTO for 1-2 consecutive patients per synthesis with a high reproducible standard. PET-imaging with 11C-metomidateMTO has the potential to be an attractive method for the characterisation of adrenal masses with the ability to discriminate lesions of adrenal cortical origin from noncortical lesions. Additionally, MTO might be useful for staging in patients with metastatic disease in adrenocorticalcarcinoma as demonstrated in our two patients. It may also be superior to FDG imaging, which has already been shown to be a sensitive tool in this group of patients. The synthesis allows the fast routine support of 11C-metomidate for at least two patients per synthesis with a high reproducible standard.

Synthesis and in vivo evaluation of [11C]-zolpidem, an imidazopyri-dine with agonist properties at central benzodiazepine receptors

F. Dumont (1), R.N. Waterhouse (1), L.S. Kegeles (1), J.A. Arcement (1), A. Sultana (1), F. Mattner (2), A. Katsifis (2), M. Laruelle (1). (1) Columbia University, New York, NY, USA, (2) ANSTO, Menai, Australia.

Aim: Disturbances in GABA receptor function are thought to be involved in the pathology of several neuropsychiatric conditions. Binding of GABA to the GABAA receptor enhances the binding of benzodiazepine (BDZ) agonists to their binding site on the GABAa ion channel, a phenomenon referred to as the GABA shift. In contrast, the binding of full BDZ antagonists remains unaltered. To study this phenomenon in vivo, we synthesized and evaluated [11C]-zolpidem, an imidazopyridine with agonist properties at the central BDZ receptors. Materials and methods: [11C]-Zolpidem was synthesized by reaction of desmethylzolpidem with [11C] methyl iodide. The lipophilicity of the compound was measured by a HPLC method. We evaluated the regional brain distribution of [11C]-zolpidem in male Wistar rats (dose: 3.7 - 9.3 MBq) and by a PET scan in a male baboon (dose: 54 MBq). Results: [11C]-Zolpidem was synthesized in a 19.19 ± 3.23 % yield (n=3, EOB) with specific activities of 41.2 ± 3.9 GBq/?mol. The estimated log P value was 1.73. The regional brain activity (% ID/g) after i.v. tail injection in rats was low and did not parallel the known distribution of the central benzodiazepine receptors. The peak uptake was seen at 5 min and was 0.197, 0.188, 0.202 and 0.206 %ID/g for frontal cortex, hippocampus, cerebellum and brain stem respectively. PET imaging in a baboon confirmed the results obtained in rats of low brain uptake. Logan graphical analysis gave regional distribution volumes of 0.326, 0.270, 0.277 and 0.276 ml/g in occipital cortex, hippocampus, cerebellum and midbrain respectively. Plasma metabolite analysis in a baboon showed the formation of a polar metabolite and a free fraction of 4 %.

Conclusion: [11C]-Zolpidem was successfully synthesised in good yield and high specific activity. However, from rat and baboon studies it can be concluded that it is not a suitable tracer for in vivo visualisation of central benzodiazepine receptors.

Synthesis and evaluation of 3-((1-(3-[18F]-fluoropropyl)-2(S)-pyrro-lidinyl]methoxy)piperidine ([18F]-NicFP) as a potential a4B2 nicotinic acetylcholine receptor PET tracer

F. Dumont, A. Sultana, A.J. Balter, M. Laruelle, R.N. Waterhouse. Columbia University, New York, NY.

Aim: Nicotinic acetylcholine receptors (nAChRs), along with muscarinic receptors, are mediators of cholinergic neurotransmission. Post-mortem studies have shown a decreased concentration of nAChRs in Alzheimer patients, making imaging of the receptors very useful to study this disorder. Therefore, we synthesized and evaluated [18F]-NicFP as a potential ?4?2 subtype antagonist.

Materials and methods: [18F]-NicFP was prepared by a nucleophilic substitution by reacting the corresponding mesylate precursor with [18F] fluoride at 90 °C in the presence of kryptofix K222 and potassium carbonate. The tracer KD was measured in vitro in rat thalamic membranes (2 mg/tube, n = 3, 23-25 °C, 50 mM Tris buffer, pH = 7.4). In vivo distribution and blocking studies in male Wistar rats were also performed.

Results: [18F]-NicFPwas obtained in a 11.27 ± 2.14 % yield (n=3, EOB) with specific activities of 0.472 ± 0.181 GBq/mmol. In vitro analysis afforded a Kd of 0.92 ± 0.32 nM. Regional brain distribution studies after i.v. tail vein injection revealed a high brain uptake (1.02 ± 0.14, 1.03 ± 0.15 and 0.70 ± 0.11 %ID/g 5 min p.i. in thalamus, frontal cortex and cerebellum, respectively). The thalamus/cerebellum ratio peaked at 1.47 ± 0.07 by 5 minutes and declined to 0.97 ± 0.34 by 80 minutes. However, attempts to block tracer uptake by pre-injection of nicotine (0.03 mg/kg) or cold NicFP (1 mg/kg) did not result in a significant inhibition of uptake in any region (10 min).

Conclusion: [18F]-NicFP was successfully synthesised in good yield and high specific activity. Biodistribution studies in rats revealed a high brain uptake, fast clearance and no demonstrable specific binding, indicating that higher affinity is required. We therefore conclude that [18F]-NicFP is not a suitable PET ligand for imaging nAChRs.

Synthesis and evaluation of fluorinated tetrahydroquinoline-2-car-boxylic acid derivatives as potential NMDA ligands to study glu-tamergic neurotransmission in vivo

M. Piel (1), R. Schirrmacher (1), S. Höhnemann (1), W. Hamkens (1), M. Jansen (2), U. Schmitt (3), H. Lüddens (3), G. Dannhardt (2), F. Rösch (1). (1) Institute of Nuclear Chemistry of the University of Mainz, Mainz, Germany, (2) Institute of Pharmacy of the University of Mainz, Mainz, Germany, (3) Department of Psychiatry of the University of Mainz, Mainz, Germany.

Aim: Glutamate is the most important excitatory amino acid (EAA) in the central nervous system of mammals and plays an important role in neurodevelopment, synaptic plasticity and neurotoxicity. The NMDA receptor is one of the best charaterized glutamate receptors and represents an important target for medicinal chemistry, due to his involvement in neurodegen-erative disorders, stroke, epilepsy and schizophrenia. The structure of the receptor is very complex and posseses a variety of binding sites, of which the glycine binding site is an important target, because their ligands have less side effects compared to ligands of the glutamate and ion channel binding site. Therefore new [18F]fluorine labelled NMDA receptor ligands of the glycine binding site were developed that may potentially allow the in vivo visualization of glutamergic neurotransmission.

Material and Methods: Four new fluorine containing NMDA ligands and their corresponding precursors were synthesized. The labelling reactions were examined and optimised using [18F]fluorine and 2-[18F]fluoroethyltosylate as labelling agents. Afterwards preliminary pharmacological experiments were performed with the ligands. The lipophilicity of the molecules were determined using the HPLC method and Sörensen buffer as eluent. In [H3]MDL-105,519 binding assays the in vitro affinity was examined. Furthermore for one ligand ex vivo-biodis-tribution studies were carried out, examinating the uptake in brain, liver, kidney and bone. Results: Of the synthesised compounds trans-5,7-dichloro-4-{3-[4-(2-[18F]fluoro-ethoxy)-phenyl]-ureido}-1,2,3,4-tetrahydro-quinoline-2-carboxylic acid seems to be the most promising ligand. The in vitro-affinity of this molecule was determined showing a very high affinity with an IC50 of 4.4 nM, whilst having a moderate lipophilicity with a logD of 1.3. The ligand could be labelled in a radiochemical yield of about 95% after a reaction time of 15 minutes using 2-[18F]fluoroethyltosylate as labelling agent.

Conclusion: We synthesised four new 19F-fluorinated tetrahydroquinoline-2-carboxylic acid derivatives, examined the lipophilicity and in vitro-affinity of these ligands and optimised the 18F-labelling reactions. Among these compounds trans-5,7-dichloro-4-{3-[4-(2-[18F]fluoro-ethoxy)-phenyl]-ureido}-1,2,3,4-tetrahydro-quinoline-2-carboxylic acid seems to have the best properties for the in vivo visualization of the glutamergic neurotransmission. Therefore a further evaluation of this compound is planned.

The biodistribution and the cell uptake of F-18 fluorocholine derivatives (FCHDs)

J.H. Park (1), S.D. Yang (1), S.W. Kim (1), M.G. Hur (1), K.S. Chun (1), S.J. Lim (1), S.W. Hong (1), K.H. Yu (2). (1) Laboratory of Cyclotron Application of KCCH, Seoul, Korea, (2) Department of Chemistry of Dongguk University, Seoul, Korea.

Objectives: Previous studies showed that [11C]choline(CH) and [18F]fluorocholine(FCH) are effective for PET imaging of prostate cancer metastases and brain tumors. In order to examine the possibility for clinical PET scanning of modified F-18 labeled [18F]fluorocholine deriva-tives(FCHDs) having different alkyl chain have been prepared and evaluated. Methods: The FCHDs were synthesized by the reaction of [18F]fluoroalkyl(ethyl, propyl and butyl) tosylate with N,N-dimethylethanolamine. The purification was achived by anion exchange, alumina and silica SEP-PAK cartridge. The radiochemical purity was checked by high performance liquid chromatography(HPLC). The cell uptake of the FCHDs was measured on glioma(9L) and colon adenocarcinoma(SW620) and biodistributions were determined in balb/c mouse at 5min, 20min, 40min and 80min.

Results: The cell uptake of FCHDs as percent injected dose were about 2% for 9L and 1.5% for SW620. For FCH, 1.77% for 9Land 2.77% for SW620. The FCHDs showed similar organ uptake to CH at 5-min post injection but rapidly excreted from each organ and the blood uptake was about 4-fold higher than CH at 5-min post injection. The liver uptake of the FCHDs was increased with an increment chain length.

Conclusion: CH and FCH have more higher affinity towards SW620 than 9L, while the FCHDs showed opposite result. Further evaluation of FCHDs in mouse with colon cancer and brain tumors is in progress.

Synthesis of [18F]-Fluoroethylfenoterol for Imaging the beta-2 Receptor status in Lung in vivo

E. Schirrmacher (1), R. Schirrmacher (1), I. Wessler (2), R. Buhl (3), H.J. Machulla (4), F. Roesch (1). (1) Institute for Nuclear Chemistry, Universitiy Mainz, Mainz, (2) Pharmacological Institute, Hospital of the University of Mainz, Mainz, (3) III. Medicinal Hospital, Hospital of the University of Mainz, Mainz, (4) PET-Center, Section Radiopharmaceuticals, Hospital of the University of Tübingen, Tübingen.

Aim: The b2 receptor system is important for the sympathetic innervation of the lung. Via the second messager cAMP, b2 agonists effect a relaxation of bronchial smooth muscle. The importance of b2 adrenoceptor density for obstructive respiratory diseases such as asthma or chronic obstructive bronchitis is still not exactly clarified. For understanding the pathogene-sis, therapy and prognosis of such diseases, a non-invasive, quantifiable imaging of the b2 receptor in lung would be of considerable importance. There have already been several attempts, however mostly antagonists were labelled with carbon-11 [1]. The aim of this project was the synthesis of a selective fluorine-18 labelled b2 agonist to visualise the b2 receptor status in lung. We thus synthesised a fluoroethyl derivative of fenoterol. Material and Methods: As both the catechol phenol moieties, as well as the b-hydroxy function and the amine group are necessary for receptor binding, we aimed at fluoroethylating the 4-phenolic hydroxy function because this is unlikely to reduce the affinity of the molecule to the receptor. For first labelling experiments, we synthesised both the labelling precursor and the standard 19F-compound as a racemate. The standard [19F]fluorethylfenoterol was synthe-sised from fenoterol hydrobromide which was a gift of Boehringer Ingelheim Pharma KG. First in vitro tests with guinea pig trachea aimed at showing whether the receptor binding properties of the fluoroethylfenoterol differed from the original compound fenoterol. Isolated guinea-pig tracheae were placed in organ baths horizontally under a tension of 1 g and contracted by the application of the muscarinic receptor agonist oxotremorine (100 nM) [2]. Cumulative concentration-response curves were established for fluoroethylfenoterol and fenoterol by stepwise increasing the concentration.

Results: 5-(2-{2-[4-(2-[18F]Fluoroethoxy)-phenyl]-1-methyl-ethylamino}-1-hydroxy-ethyl)-benzene-1,3-diol ([18F]fluoroethyl fenoterol) was synthesised from 4-(2-{benzyl-[2-(3,5-bis-benzyloxy-phenyl)-2-hydroxy-ethyl]-amino}-propyl)-phenol using 2-[18F]fluoroethyltosylate (92% RCY) followed by reductive cleavage of the benzyl protecting groups. The IC50 values for fenoterol and fluoroethylfenoterol were nearly identical (about 60 nM). Conclusions: [18F]fluoroethylfenoterol was synthesised in 92% RCY. Preliminary in vitro tests showed the racemic [19F]fluoroethylfenoterol to be as potent in relaxation of lung tissue as fenoterol itself. An enantioselective synthesis is in progress to obtain the (R,R)-fluo-roethylfenoterol, which is thought to be the most potent agonist of all the enantiomers. References: [1] Elsinga P. et al. Nucl Med Biol 23: 159-167 (1996) [2] Wessler I. et al.. Naunyn-Schmiedeberg'sArchives ofPharmacology 348: 14-20 (1993)

Comparison of [18F]Fluoroazomycinarabinoside (FAZA) and [18F]Fluoromisonidazole (FMISO) as hypoxia tracers in experimental rat tumors

D. Sorger (1), M. Patt (1), P. Kumar (3), L.I. Wiebe (3), A. Seese (1), A. Tannapfel (2), O. Sabri (1). (1) Department of Nuclear Medicine, University of Leipzig, Germany, (2) Institute of Pathology, University of Leipzig, Germany, (3) Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.

Aim: [18F]Fluoroazomycinarabinoside (FAZA) had been synthesized recently (1). In cell culture studies uptake of FAZA under hypoxic conditions could be shown to be quantitatively comparable to that of the well established nitroimidazol compound [18F]Fluoromisonidazole (FMISO). For future human application of FAZAin PET studies it is necessary to evaluate in vivo parameters for the new compound with regard to hypoxia dependent tumor uptake and to the imaging contrast between tumor and non-tumor tissue. It is the aim of this study to test FAZA as in vivo tracer of tissue hypoxia in an experimental rat tumor by comparing it to FMISO.

Methods: Female Wistar rats (n = 15) were injected s.c. in the right hind leg with 5 x 106 mammary carcinoma cells (Walker 256). After 7 to 14 days hypoxic regions in the experimental tumor were recorded using PET (ECAT HR+, 5 min transmission, 10 min emission), 1 h and 3 h after i.v. application of 2.5 ± 0.9 MBq FAZA or 3.1 ± 1.0 MBq FMISO on consecutive days. Intratumoral hypoxia was confirmed polarographically (pO2 < 10 mm Hg). Results: Both FMISO and FAZA were accumulated in experimental tumors with a tumor/muscle ratio of 2.6 ± 0.6 (n = 14) and 2.3 ± 0.5 (n = 12), respectively, at 1 h p.i.. Accumulation was observed in the tumor center or adjacent to histochemically evaluated necrotic zones. An increased tumor to non-tumor ratio was also observed at 3 h p.i. for both tracers. The increase was however more pronounced for FMISO than for FAZA (4.1 ± 0.7 vs. 2.8 ± 0.4, p < 0.05).

Conclusion: FAZA can be used for imaging of hypoxic intratumoral regions. In this animal tumor model, however, PET scans after application of FAZA showed a less intensive tumor/non-tumor contrast than those for FMISO, especially at later time points. (1) Patt, M., Kumar, P., Wiebe, L.I., Machulla, H.J.: Nuklearmedizin, 38 (1999), A22

High radiochemical yield synthesis of [18F]FLT from 3'-O-nosylated thymidine and its 3-N-BOC-protected analogue

S. J. Oh, M. K. Yun, J. S. Ryu, D. H. Moon. Deaprtment of Nuclear Medicine, University of Ulsan College of Medicine, Asan Medical Center, Korea.

Aim: 18F-FLT (3'-deoxy-3'-fluorothymidine) was shown as a promising radiotracer for the assessment of tumor cell proliferation rate. In this study, we synthesized 3'-O-nosylate and its 3-N-BOC-protected thymidine derivatives as two precursors for high radiochemical yield synthesis of [18F]FLT and optimized [18F]fluorination conditions for routine clinical use. We also compared radiochemical properties OF two precursors.

Material and Methods: (5'-0-DMTr-2'-deoxy-3'-0-nosyl-p-D-threo-pentofuranosyl)thymi-dine and its 3-N-BOC-protected analogue were prepared from thymine and the overall chemical yields were 54 and 28%, respectively. For radiochemical synthesis, [18F]Fluoride was trapped on QMA cartridge and was eluted with K2CO3 and K222. After drying completely, 3'-0-nosylate precursor (10-30 mg) or 3-N-BOC-protected precursor (11-34 mg) was added with 500 pl of CH3CN, respectively. The reaction mixtures were heated at 100-130oC for 5-30 min. Hydrolysis was performed using 250-500 pl 1N HCl at 50oC or 60 pl of trifluoroacetic acid at room temperature for 5min, then followed by neutralization with 1.5ml of 2M sodium acetate. After filtering with Alumina N Sep-Pak cartridge, reaction mixture was purified by HPLC. Purification condition was water:ethanol = 85:15 with 3 ml/min at 267nm and Econosil column(10mm, 250x10mm) was used.

Results: The optimal [18F]fluorination yield of 3'-0-nosylate precursor was 85 ± 5.4% with 30 mg of precursor and a reaction time of 5 min at 130oC. For 3-N-BOC-protected analogue, [18F]fluorination yield was 82±5.4% with 34mg of precursor and a reaction time of 5 min at 110oC. After HPLC purification, overall radiochemical yield using each precursors were 40 ± 5.2% and 42 ± 5.4% and radiochemical purity were 98 ± 0.5% and 97 ± 2.1% for two precursors, respectively. Preparation time was 60 ± 10.5 min including HPLC purification for two precursors.

Conclusion: There were no apparent differences in radiochemical yield and radiochemical purity between the two precursors. However, 3-N-BOC-protected precursor required milder [18F]fluorination conditions than 3'-0-nosylate precursor. From these two precursors, [18F]FLT can be prepared reliably without lengthy precursor synthesis and long reaction time fro routine clinical application.

Optimized Synthesis of the PET-alpha4beta2-nAchReceptor ligand 2-18F-A85380 and in-vitro-evaluation in Parkinson's disease by using 6-OHDA lesioned rats

J. Schmaljohann (1), M. Minnerop (1), P. Karwath (2), D. Gündisch (3), U. Wüllner (1), S. Guhlke (2). (1) Department of Neurology of the University of Bonn, (2) Department of Nuclear Medicine of the University of Bonn, (3) Department of Pharmaceutical Chemistry of the University of Bonn, Germany.

Aim: PET is an important tool for the in-vivo investigation of the functional status of the different receptors in brain. PET can be especially valuable for the early diagnosis of neurode-generative disorders. Labelling nicotinic Acetylcholin-Receptors (nAchR) with 2-18F-A85380, a ligand with high affinity to nAchR's subtyp a4p2, enables the visualization of the nAchR-rich thalamus, cortex and striatum in baboons. In our work, we investigated the potential of this PET-tracer for its clinical use by optimization the synthesis of the 2-18F-A85380 and in-vitro evaluation using 6-OHDA lesioned rats as model for Parkinson's disease. Methods: The reaction conditions for the synthesis of 2-18F-A-85380 and a RP-HPLC-purifi-cation were optimized using the precursor 2-Nitro-(N-BOC)-A-85380. In-vitro experiments were carried out with brain slices of normal and unilaterally 6-OHDA lesioned rats. After incubation with 2-18F-A85380 the distribution of the tracer was measured by means of a phosphor imager.

Results: The radiochemical yield of 85% for the nucleophilic substitution could be reached with the Nitro-precursor. For the purification from the precursor a fast RP-HPLC was investigated resulting in a purity of >99%. The overall radiochemical yield of 2-18F-A85380 was 75±5% in 50min. In normal rat brain slices the expected highest uptake was measured in the thalamus, the region with the highest concentration of a4p2 nAchR's. In unilaterally 6-OHDA lesioned rats the striatal binding of 2-18F-A85380 was significantly reduced ipsilateral to the lesion (to 67±16% of the unlesioned site). Also the cortical binding ipsilateral to the lesion was significantly reduced to 90±10% of the unlesioned site. The thalamus showed no difference in the binding of 2-18F-A85380 in 6-OHDA lesioned rats.

Conclusions: The synthesis of 2-18F-A85380, with 54% uncorr. yield and a fast HPLC-purifi-cation, allows the production for the clinical application of this nAchR-ligand. The reduction in the striatal and cortical binding of 2-18F-A85380, resulting from nAchR located presynapti-cally on dopaminergic terminals in 6-OHDA lesioned rats, suggests that 2-18F-A85380 is a suitable ligand to investigate the status of nicotinic receptors in Parkinson's disease.

Binding rate of [18F]Fluoroazomycinarabinoside (FAZA) into rat mammary carcinoma cells during hypoxia

D. Sorger (1), M. Patt (1), P. Kumar (2), L.I. Wiebe (2), R. Kluge (1), O. Sabri (1). (1) Department of Nuclear Medicine, University of Leipzig, Germany, (2) Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.

Binding rate of [18F]Fluoroazomycinarabinoside (FAZA) into rat mammary carcinoma cells during hypoxia

D. Sorger, M. Patt, P. Kumar*, L.I. Wiebe*, O. Sabri

Dept. of Nuclear Medicine, University of Leipzig, Germany and *Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada

Aim: The potential PET tracer [18F]Fluoroazomycinarabinoside (FAZA) for the non-invasive assessment of tissue hypoxia had been synthesized (1) to get a kinetically more suitable agent than the rather lipophilic compound [18F]-Fluoromisonidazole (FMISO). It is the aim of this study to evaluate whether the hypoxia induced diffusion of FAZA into tumor cells is quantitatively comparable or even better than that of FMISO so far considered as the "golden standard" for hypoxia related cell uptake.

Methods: 2 x 107 rat mammary carcinoma Walker 256 cells were maintained in 5 ml RPMI 1640 medium (10 % FBS, 1.5 mM glucose) for 20 min at 37 oC under a hypoxic (1.5 % O2, 5 % CO2, 93.5 % N2) or normoxic (20 % O2, 5% CO2, 75 % N2) atmosphere. After addition of 50 kBq FAZA or FMISO the incubation was continued for 20 and aor 100 min. O2 partial pressure in the hypoxic medium was maintained below 3 mm Hg. Cells were sedimented by centrifugation, washed (3 x 4 ml PBS buffer), and counted for 18F radioactivity. [18F]FDG cell uptake was tested for comparison.

Results: Cell uptake of FAZA and FMISO under hypoxic atmosphere increased with time. Cell uptake ratio (hypoxia/normoxia) was 1.4 ± 0.3 (FAZA) andtimes 1.6 ± 0.4 (FMISO) after 20 min and 2.8 ± 0.5 (FAZA) and 3.1 ± 0.4 (FMISO) after 100 min of tracer incubation. For FDG an uptake ratio (hypoxia/normoxia) of 2.6 ± 1.3 was measured already after 20 min of incubation.

Conclusion: The binding rate of FAZA into hypoxic Walker 256 tumor cells was found to be in the same order of magnitude as that of FMISO. This makes FAZA a promising candidate for in vivo studies of tumor hypoxia. The comparatively faster increase of FDG cell uptake under hypoxic conditions can be explained by hypoxia induced changes of the glucose transport mechanisms which are more effective than the simple diffusion processes which are responsible for FMISO or FAZAuptake in the hypoxic cell.

1)Patt, M., Kumar, P., Wiebe, L.I., Machulla, H.J.: Nuklearmedizin, 38 (1999), A21 literature removed by abstract editors2

N1-Methyl-9-[(4-[F-18]fluoro-3-hydroxymethylbutyl]guanine [F-18]MFHBG as new substrate of HSV-1-thymidine kinase to monitor gene expression?

B. Johannsen (1), B. Noll (1), M. Grote (1), ST. Noll (1), R. Bergmann (1), G. Wolkersdorfer (2). (1) Forschungszentrum Rossendorf, Institut für Bioanorganische und Radiopharmazeutische Chemie, (2) Technische Universität Dresden, Universitätsklinikum, Dresden, Germany.

Gene therapy with the transfer of Herpes simplex virus type 1 thymidine kinase gene (HSV1-tk) has shown significant potential in treating several cancers. Many nucleoside analogues are known to localize selectively HSV1-tk transfected cells and show a high specificity for the viral enzyme, especially acyclic nucleosides such as ganciclovir or penciclovir. The penci-clovir derivative [F-18]FHBG is one of the proposed tracer for monitoring the gene expression by positron emission tomography. In order to improve the tracer properties, we modified the lipophilicity of [F-18]FHBG by introduction of a methyl group into the N1-position to get N1-methyl-9-[(4-[F-18]fluoro-3-hydroxymethylbutyl]guanine 3.

Materials and methods: The precursor 1 and the nonradioactive reference substance (MFHBG) were prepared by methylation of N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[(4-(p-toluene-sulphonyloxy))-3-(p-anisyldiphenylmethoxy)-methyl-butyl]guanine with methyl iodide in the N1 position. The precursor 1 reacts with a [F-18]KF kryptofix complex to the intermediate 2 in a 65-75 % radiochemical yield. In a second step the protecting groups are removed from 2 by heating in methanolic HCl solution. The tracer is purified by RP HPLC separation. The identity of the tracer [F-18]MFHBG with the nonradioactive reference compound was also proved by HPLC. The in vitro uptake of [F-18]FHBG and [F-18]MFHBG was evaluated into transduced and non-transduced human MC 38 cells.

Results: The labelling yield amounts to 70%, and the radiochemical purity of the tracer is greater than 98 %. Biodistribution data of [F-18]MFHBG show a fast blood clearance without remarkable erythrocyte binding. An initial high uptake of the tracer was found in the spleen, kindney and liver, which decreased rapidly in time. No metabolites were found. The rapid blood and organ clearance (faster than for [F-18]FHBG) and the high in vivo stability of [F-18]MFHBG are considered advantageous for in vivo monitoring of the gene transfer in tumours. The uptake of [F-18]MFHBG is however lower than the uptake of [F-18]FHBG in HSV1-tk transfected cell lines.

Conclusion: The novel tracer 9-[(4-[F-18]fluoro-3-hydroxymethyl-butyl]-guanine ([F-18]MFHBG) seems to be inferior to [F-18]FHBG because of lower uptake in the target cells. It is assumed that the molecule position chosen for methylation is unsuitable for the anticipated improvement of the tracer.

Tyrosine Derivatives: Synthesis of F-18 labeled Fluoroalkyltyrosines

B.S. Moon (1), S.H. Ahn (1), S.W. Kim (1), M.G. Hur (1), J.H. Park (1), S.D. Yang (1), K.S. Chun (1), S.W. Hong (1), D.Y. Chi (2). (1) Laboratory of Cyclotron Application of KCCH, Seoul, Korea, (2) Department of Chemistry of Inha University, Inchon, Korea.

Objectives: Radioisotope labeled tyrosine has clinical potential in oncology, neurology and psychiatric disorders. In many studies, a variety of radio labeled tyrosine derivatives were synthesized and have proven to be useful for imaging tumor. We hereby report the synthesis of four, 3-(2-[18F]fluoroethyl)tyrosine 1, 3-(3-[18F]-fluoropropyl)tyrosine 2, 0-methyl[3-(2-[18F]fluoroethyl)tyrosine 3, and 0-methyl[3-(3-[18F]fluoropropyl)tyrosine 4. The target materials have been designed based on the biological data of radiolabeled tyrosine derivatives. Methods: New tyrosine derivatives were prepared in 7 step from a commercially available 3-iodotyrosine. Tosylated tyrosine was used as a precursor, which synthesized by the reaction of the hydroxyalkyl tyrosine moiety with ^-toluenesulfonyl chloride and DMAP in C^C^. Labeling reaction was carried out by NCA nucleophilic substitution with K[18F]F/K2,2,2 in acetonitrile at 100 oC for 25 min. The reaction mixture was hydrolyzed with 4 N HCl at 110 oC for 40 min. After hydrolysis [18F]fluoroalkyl tyrosine derivatives were purified by HPLC and the collected fraction was passed by strong cation exchange resin for further purification. Results: The labeling yield was about 48% for 1, 82% for 2, 33% for 3 and 80% for 4 on average. The radiochemical yield was 15% for 1, 40% for 2, 12% for 3 and 35% for 4 after hydrolysis (radiochemical purity was > 95 % after HPLC purification), respectively. Conclusion: Research is ongoing to evaluate the biological properties for [18F]-labeled tyro-sine derivatives (1, 2, 3, 4) comparing to those of 0-(2-[18F]fluoroethyl)-L-tyrosine in rat bearing human 9L, glioma cell line.

Date: 02.09.2002 • Time: 14:30 - 16:00 HALOGENS & TUMOR MARKERS

Hall: Poster exhibition

In vitro characterisation of new potential ligands for the nicotinic receptors

W. Bisson, L. Mu, P.A. Schubiger, G. Westera. Center for Radiopharmaceutical Science, University Hospital Zurich.

Aim: The inhibition constant (Ki) of different newly synthesized ligands for the «4^2 nico-tinic receptors were measured. Those values are important to determine the potential of these compounds as PET ligands and to study the relationship between the chemical structure of the ligand and the affinity for the binding site of the nicotinic receptor.

Method: The ligands 8-Methyl-3-(pyridin-3-yloxy)-8-aza-bicyclo[3.2.1]octane (LJ20W), 8-Methyl-3-pyridin-3-yl-8-aza-bicyclo[3.2.1]oct-2-ene (LJ33b), 2-(Pyridin-3-yloxy)-7-aza-bicy-clo[2.2.1]heptane (LJ37) and 8-Methyl-3-pyridin-3-yl-8-aza-bicyclo[3.2.1]octan-3-ol (LJ38), which show some analogy with the well known «4^2 ligand epibatidine, are characterized by in vitro inhibition binding studies on rat brain homogenates against [3H]-cytisine. Binding assays were performed at the final volume of 0.2 ml containing 100^g of protein in a BSS buffer at pH 7.4. The concentration of [3H]-cytisine (59600dpm/pmol) was 2nM. After 1h at 0°C, the samples were vacuum-filtered on glass fiber filters (Whatman GF/C) which were then washed with ice cold buffer (2?4ml). Non-specific binding was estimated in the presence of 0.1mM nicotine.

Results: The average specific binding obtained was 80%. The values at 0°C of Ki for the lig-ands LJ20W, LJ33b, LJ37 and LJ38 are respectively .

LIGAND LJ20W LJ33b LJ37 LJ38

14 |iM

Conclusion: Further modification and characterization of compound LJ37 seems indicated. The C-11 N-methylated and 18-F fluorinated derivatives may provide new tools for PET stud-

Phase-transfer catalytic synthesis of 6-18F-fluoro-L-DOPA via room temperature alkylation promoted by (S)-NOBIN

O. Fedorova (1), V. Zaitsev (1), O. Kuznetsova (1), S.M. Ametamey (2), Y. Belokon (3), M. Nader (4), P.A. Schubiger (2), R. Krasikova (1). (1) Institute of Human Brain, Russian Academy of Sciences, St. Petersburg, Russia, (2) Center for Radiopharmaceutical Science of ETH, PSI and USZ, Villigen PSI, Switzerland, (3) A.N. Nesmeyanov Institute of Organo-Element Compounds, Russian Academy of Sciences, Moscow, Russia, (4) ARGOS Zyklotron GesmbH, PET Zentrum Klagenfurt, Austria.

Phase-transfer catalytic synthesis 6-18F-fluoro-L-DOPA via room temperature alkylation promoted by (S)-NOBIN

Aim: Recent advances in a stereoselective synthesis of amino acids offer new opportunities for a preparation of enantiomerically pure 18F-labelled analogues for PET application. In addition to previously used stoichiometric approach based on the 18F-fluorobenzyl alkylation of activated glycine fragments in the structure of various chiral inductors, phase-transfer catalytic (PTC) reactions were introduced into a synthesis of 6-18F-fluoro-L-DOPA (FDOPA), well established PET radiotracer for the cerebral presynaptic dopaminergic function in man. Now we intend to evaluate newly developed by some of us PTC system based on (S)-NOBIN which promotes an alkylation of achiral glycine substrate at room temperature providing high enantiomeric excess (e.e.) of amino acid.

Methods: An alkylating agent, 6-18F-fluoropiperonyl bromide (I) was prepared by the method earlier described. Reaction of (I) with a fresh mixture of achiral NiII complex of Schiff base of 2-benzoylphenylamide of pyridine-2-carboxylic acid and glycine, (S)-NOBIN and solid NaOH in CH2Cl2 was carried out at room temperature under stirring for 5 min. Reaction was quenched by addition of 57% HI before removal of solvent to prevent heating-induced racem-ization of the (S)-complex. The (S) complex was decomposed by 6 M HCl following depro-tection of hydroxyl groups by reflux with 57% HI. Crude FDOPA was purified by reverse phase HPLC. Synthesis time using Anatech RB86 robot was 100 min.

Results: FDOPA was obtained in enantiomeric purity of 95% high enough for a clinical use. Work is presently in progress to optimise the radiochemical yield.

Conclusion: Our first results with (S)-NOBIN show that using this catalyst FDOPA can be obtained in high e.e. by carrying out alkylation at room temperature. The use of recently reported PTC system (Guillouet S., J Label Compds Radiopharm 44: Suppl 1, S 868-870, 2001), based on 0-(9)-benzyl-N-9-antracenylmethylcinchonidinium in a synthesis of FDOPA requires to maintain alkylation temperature at 0oC which is associated with problems in automation. This work was supported by the SNSF contract 7SUPJO62161.00/1 and the Scientific Centre of St.Petersburg, Russian Academy of Science.

[76Br] p-isothiocycnatobenzyl-undecahydro-bromo-7,8-dicarba-nido-undecaborate (-1) (Br-NBI): preparation and use for labelling of monoclonal antibody.

V. Tolmachev (1,2), K.J. Winberg (1), M. Persson (2), S. Sjoberg (1). (1) Department of Organic Chemistry, Uppsala University, Uppsala, Sweden, (2) Division of Biomedical Radiation Sciences, Uppsala University, Uppsala, Sweden.

Aim: Positron emitting radionuclide 76Br (T ? =16 h) may be used for labelling of Mab. However, conventional methods of radiobromination can not provide good retention of radio-catabolites in tumour cells after internalisation of radioimmunoconjugates. The use of charged prosthetic group might improve retention of radiohalogens. Possible candidate for such prosthetic group might be p-isothiocycnatobenzyl -7,8-dicarba-nido-undecaborate (-1) (NBI), which contains negatively charged nido-carborate (-1) anion, and which had been earlier used for radioiodination of Mab. The aim of the study was to develop method for radiobromination of anti-HER2 Mab trastuzumab using NBI for future biological evaluation. Materials and methods: The 1-phenyl-1,2-dicarba-c/oso-dodecaborane was synthesised by reacting phenyl acetylene with decaborane in acetonitrile. Nitration of the phenyl ring using 15/85 % mixture of sulphuric acid and nitric acid gave the desired 1-(p-nitrophenyl)-1,2-dicarba-c/oso-dodecaborane. Reduction of the nitro group using tin chloride gave the amino product, 1-(p-aminophenyl)-1,2-dicarba-c/oso-dodecaborane. Degradation of c/oso-carborane to the nido analogue was done using potassium hydroxide in refluxing ethanol. The tetra methylammonium salt of the compound was obtained by adding tetramethylammonium-chloride to the solution. The amino function was then converted to the isothiocyanat using thiocar-bonyldiimidazol in dry THF at 0 °C. The sodium salt of the product was obtained by sodium cation exchange and characterised using 11B and 13C NMR and IR spectroscopy. Radiobromination of NBI in aqueous media using Chloramine-T was studied. The influence of concentrations of substrate and oxidant, as well as reaction time was studied. Further, the coupling of brominated NBI to antibody was optimised. Stability of the label in vitro in different denaturing as well as in physiological condition was assessed. Specificity of binding of labelled Mab to HER2 presenting cells was examined.

Results: The overall yield of the synthesis of p-isothiocycnatobenzyl -7,8-dicarba-nido-unde-caborate (-1) was about 4 %. The compound was radiobrominated with the yield of 93-95 % using Chloramine-T as an oxidant. Coupling to mAb was performed without intermediate purification, "in one pot". An overall labelling yield (mean ± max error) of 55.7 ± 4.8 % was achieved. The label was stable in vitro in physiological and denaturing conditions. Radiolabelled Mab preserved specific binding to breast cancer cells.

Conclusion: A new method for indirect labelling of Mab using positron emitter 76Br was developed. The method provides a good labelling yield and preserved antigen-binding capacity of Mab.

300 nM

250 nM

Synthesis of Radioiodine-labeled Dibenzyl Disulfide for Evaluation of Tumor Uptake

E.K. Ryu, Y.S. Choe, S.S. Byun, J.Y. Paik, K.-H. Lee, Y. Choi, S.E. Kim, B.-T. Kim. Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

Aim: Diallyl disulfide found in garlic has been known to inhibit the growth of human breast cancer cells (MCF-7) and other cancer cells. In this study, therefore, dibenzyl and allylbenzyl disulfides were synthesized and their growth inhibitory effects on MCF-7 cells were investigated. Among these, dibenzyl disulfide was labeled with 123I/125I for evaluation of tumor uptake.

Materials and Methods: Halogen substituted disulfides were synthesized using 2,2'-dithio-bis(benzothiazole) and one equivalent each of the corresponding thiols. The 4'-bromo/iodobenzyl thiol was synthesized from the corresponding 4'-halogen substituted benzyl alcohol in three steps. Growth inhibition studies were performed on MCF-7 cells that were grown at 37 °C for 48 hr prior to exposure to the disulfides. Radioiodine-labeled disulfide was prepared by halogen exchange reaction on the 4'-bromodibenzyl disulfide in the presence of Na123I/125I and CuCl at 160 °C for 90 min, followed by HPLC purification (C18 column, 85:15-methanol:water, tR=16-17 min). The resulting disulfide was incubated with MCF-7 cells stimulated with estradiol in order to enhance proliferation, and cell uptake of the radioactivity was compared with that of unstimulated cells.

Results: Unsymmetric disulfides were readily synthesized using 2,2'-dithiobis(benzothiazole) and thiols in high yields. Growth inhibition studies by the disulfides showed inhibition (>90%) comparable to diallyl disulfide (100%). Cu(I)-assisted radioiodination gave 4'-123I/125I-iododibenzyl disulfide in overall 30-40% radiochemical yield and with high specific activity. Cell uptake studies of the radiolabeled disulfide showed that the uptake increased slightly in estrogen responsive MCF-7 cells stimulated with estradiol compared with unstimulated cells, suggesting a good correlation between its growth inhibitory effect and tumor cell uptake. Conclusion: This study demonstrates that the radioiodine-labeled dibenzyl disulfide may be useful for evaluation of tumor uptake. Further studies are warranted to elucidate the uptake mechanism of the disulfide to the tumor cells.

Routine production of 4-18F-fluorobenzyl bromide in a remote-controlled synthetic apparatus

R. Krasikova (1,2), V. Zaitsev (1,2), P. Truong (1), M. Schou (1), C. Halldin (1). (1) Karolinska Institutet, Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, Stockholm, Sweden, (2) Institute of Human Brain, Russian Academy of Science, St. Petersburg, Russia.

Aim: Preparation of 18F-labelled benzyl bromides has been reported as useful alkylating agents for asymmetric synthesis of 18F-aromatic amino acids. A key synthetic step has been the bromination reaction using Ph3PBr2 as earlier suggested by R. Iwata et al., (Appl Rad Isot, 2001) for a semi-automated preparation of 4-18F-fluorobenzyl bromide (4-18F-FBB). 4-18F-FBB is extensively used for introducing 18F into aromatic part of various biologically active compounds and drugs, but its preparation is too complicated for the operation via commercially available 18F-fluorination modules. Based on our experience we intend to develop a remote controlled apparatus for 4-18F-FBB which can be implemented into routine production of PET radiopharmaceuticals.

Methods: 4-18F-FBB was synthesised in three steps: 1) nucleophilic fluorination of trifluo-romethanesulfonate salt of 4-(trimethylamino)benzaldehyde in DMSO at 150oC for 7 min; 2) on-line reduction of resulting 4-18F-fluorobenzaldehyde with an aqueous NaBH4 on the C18 SepPak; 3) room temperature bromination of the purified 4-18F-fluorobenzyl alcohol with Ph3PBr2 (3 min stirring in CH2Cl2).

A remote-controlled apparatus was constructed by Laboratech, Sweden. It consists of nine 3 way valves (Burkert Compromatic), heating block with a cooling gun, 2 reactive vessels with moving needles, gas manifold. All these parts were placed on the front door of stainless steel box, while electronics was inside.

Results: 4-18F-FBB was obtained in radiochemical purity >95%, radiochemical yield of 35% (EOB) within 50 min synthesis time. The reactive complex [K/K2.2.2]+18F- for the first synthesis step was prepared by an original method where 18F-fluoride was trapped on the QMA SepPak and eluted by solution of kryptofix and K2CO3 in CH3CN/H2O (96/4). With this composition conventional azeotropic drying of the complex was eliminated, which facilitates automation.

Conclusion: All the synthesis steps were optimized providing stable radiochemical yield and purity of the product required for routine application. An effective remote-controlled synthetic apparatus for routine production of 4-18F-FBB has been developed to keep a minimal radiation burden on the personal.

High uptake of 131I-methylene blue by melanoma and mammary tumor cells. New prospectives for scintigraphy?

G. Sobal, M. Rodrigues, H. Sinzinger. Department of Nuclear Medicine of the Vienna University, Vienna, Austria.

Aim: Radioiodinated methylene blue is a promising tracer showing high uptake in human pigmented melanoma and mammary tumor cells. To evaluate the potential relevance of 131I labeled methylene blue for melanoma detection, we investigated in-vitro the SK-MEL 28- and 518A2 melanoma cells uptake of 131I methylene blue. We also investigated another tumor cells, human mammary epithelial cells, malignant SK-BR-3 and nonmalignant HBL-100. Material and Methods: The radiolabelling of the tracer was perfomed using 1% methylene blue and 131I sodium iodide. Thereafter freshly prepared potassium iodate/iodide solution in the presence of 0.18 M hydrochloric acid was added. The reaction time was 60 min under heating in the water bath at 100°C. After cooling down the mixture was purified with a Lida SAX -sample preparation column, followed by filtration through a Millipore Millex-GS 0.22|m filter. For performing quality control a Merck HPLC-system: L-6200A-pump, L-4000 UV-detector (X=600 nm) and a Packard 150 TR Flow Scintillation Analyzer was used. Column: RP-18; 4x250 mm. Eluent: 0.1% trifluoroacetic acid, 90% acetonitrile and 10% water.

Results: The radiochemical purity of the tracer was 99.89±0.11% (n=9). We also performed TLC method using ITLC-SG strips and the same solvent. Using this method radiochemical purity was determined as 99.98±0.08% (n=9). This indicates the excellent agreement between the two methods. The stability of the preparation was also studied for 15 min, 3h and 6 h. The stability of the tracer in labelling buffer was persistent over 6 h and amounted to 98.93%±0.21% (n=9). In plasma the stability of the tracer was also very high and amounted to 97.40%±0.11% (n=9) after 6h. We measured uptake at 22°C and 37°C. By both melanoma cells types, the uptake of the tracer was very high and higher at 37°C (SK-MEL 28-cells 56.361.8% vs 36.3-56.0%, (n=6) by 518A2-cells) than at 22°C (45.0-51.7% vs 25.6-36.3%, (n=6), respectively. Also by both mammary cells lines the uptake of the tracer was very high, but did not differentiate between 22°C and 37°C. At 37°C the uptake amouted to (SK-BR-3 cells 50.1-57.7% vs 53.2.9-63.5%, (n=6) by HBL-100-cells and at 22°C (48.9-61.6% vs 54.164.8%, (n=6), respectively.

Conclusion: Therefore, we expect that this tracer, because of its easy handling, high stability in buffer and plasma, quite high uptake by both tumor cells, could be successfully used in the routine application for melanoma and mammary tumors imaging or eventually even radiotherapy.

Quantitative Yield Kit-preparation of Radioiodinated Aromatic Amino Acids

J.R. Mertens (1), V. Kersemans (2), C. Joos (1), G. Slegers (2). (1) NUGE,IIRC,Vrije Universiteit Brussel, 1090 Brussel, (2) RADIOFARM,IIRC, Universiteit Gent, 9000 Gent, Belgium.

INTRODUCTION: L-2-123I-Tyrosine and 2-123I-Phenylalanine are currently evaluated in vivo as potential tumour diagnostics for SPECT. As it was shown that there is no need for high specific activity, the Cu(I) assisted isotopic nucleophilic exchange was developed for the Kit-preparation of 123I-labelled L- 2-I-Tyr and L- 2-I-Phe .

METHODS: SYNTHESIS OF PRECURSOR MOLECULES: L-2-I-Phe is prepared from L-2-Br- Phe obtained from Pep.Tech.Corp.(USA) by Cu(I) assisted nucleophilic exchange. 100 mg of L-2 Br- Phe in water containing the appropriate amount of NaI, CuSO4, SnSO4, gen-tisic acid and citric acid are refluxed during 15 hours under N2. 2-Br-Phe and 2-I-Phe (« 50%) are recovered separately from RP-HPLC. 2-I-Phe is back extracted in organic solvent. After evaporation the product is stored under N2. Identification and purity control achieved by NMR, MS, LC-MS, TLC and HPLC.

L-2-I-Tyrosine of high purity is obtained from ABX ( Dresden, Germany). RADIO SYNTHESIS: To a septum closed 1 mL Wheaton vial containing 1 mg of 2-I-Phe or 2-I-Tyr, 0.5 mg SnSO4, 5 mg gentisic acid, 10 mg citric acid and 0.17 mg CuSO4.5^O dissolved in 0.5 ml oxygen free H2O under N2 the appropriate amount (up to 50 p liter) of 123I solution is injected.The all is put into a closed aluminum safety container and heated in boiling water for 60 minutes. The content of the vial is sucked in a syringe containing the appropriate amount of make-up solution and is sent through a 0.22 micron filter into a sterile vacuum penicillin vial. Q.C. is achieved by HPLC and Sep-pak.

RESULTS and CONCLUSION: The Cu(I) method allows cold synthesis as well. The nucle-ophilic exchange occurs without changing the stereospecificity and presents an interesting alternative for a cumbersome multi-step stereospecific synthesis. The Cu(I) assisted radioiodi-nation allows routine kit preparation with a mean labeling yield of > 98%.

New Approach of Cell Uptake Kinetics of L-2-123I-Tyr and L-2-123I-Phe, New Potential Tumour Tracers for SPECT

J.R. Mertens, T. Lahoutte, C. Joos, A. Bossuyt. NUGE, Vrije Universiteit Brussel, 1090 Brussel, Belgium.

INTRODUCTION: Radioiodinated tyrosine and phenylalanine analogues can be promising as tumour tracers for SPECT. The promising results but also limitations of 123I-IMT increases the interest for the development of new radio iodinated aromatic amino acids.We developed the new compounds L-2-123I-tyrosine (2-*I-Tyr) and L-2-123I-phenylalanine (2-*I-Phe).Their uptake kinetics and properties are described in this paper.

METHODS: In vitro experiments : WiDr human colon carcinoma cells and R1M rat rab-domyosarcoma cells were used. Kinetic experiments with 2-125I-Tyr, 2-125I-Phe, L-3H-Tyr, L-3H-Phe are performed in Hepes buffer (pH 7.4, 37°C) spiked with the appropriate concentration of amino acid(s)(AA) of interest or MEM ( containing essential and non-essential AA, pH 7.4, 37 °C).

RESULTS: The uptake and efflux kinetics of 2-125I-Tyr and 2-125I-Phe (*AA,t) as a function of time for cells in equilibrium with the medium shows a rectangular hyperbolic shape reaching equilibrium (*AA,eq) represented by : 1/*AA,t = 1/*AA,eq - [t? /*AA,eq] x 1/t, with Vo,*AA = *AA,eq / t?.

At equilibrium [*AAi,eq / EKi.mAAi]out = [*AAi,eq / mAAi]in , m amount in mol in outer (out) solution or in the cells (in) of a single amino acid (EKi = 1) or EKi.mAAi of all the amino acids using the same tranporter(s) and Ki the relative Km values, showing that [*AAeq]in reflects the amount of free neutral amino acids in the tumour cells in equilibrium with the outer compartment.

The uptake is inhibited by BCH, Tyr, Leu and Ile pointing to transport by system L. As a function of the concentration the uptake follows the Michaelis Menten relation yielding an apparent Km value for 2-125I-Tyr and 2-125I-Phe of respectively 0.12 and 0.13 mM. In MEM, reflecting almost the in vivo conditions, there is no significant difference between the uptake of 2-125I-Tyr, 2-125I -Phe and that of L-3H-Phe and of L-3H-Tyr (Vo =0.56% / min per million R1M cells, Veq= 0.70 %/min).) and reflects the Vmax value observed in the kinetic studies ( 0.55 % or 7 nmol /min. per million cells; literature^rat brain cell influx = 6 nmol/min. g/ tissue ).

Conclusion: The uptake as function of time follows a rectangular hyperbolic relation allowing to determine Vo and t? with the equilibrium value [*AA,eq]in reflecting the amount of free neutral amino acids in the tumor cells in equilibrium with the actual concentration in the blood pool compartment. The uptake - concentration kinetics follow Michaelis-Menten and the resulting apparent Km values correspond with those of the natural amino acids.

Urinary Bladder Tumour Antigen (BTA) and Urinary Bladder Cancer Test (UBC) in Transitional Cell Bladder Cancer (TCC): a comparative study.

S. Nuvoli (1), A. Spanu (1), A. Mocci (2), A. Masia (1), A. Mulas (1), A. Marrosu (1), A. Falchi (1), F. Chessa (1), G. Madeddu (1). (1) Department of Nuclear Medicine of the University of Sassari, Sassari, Italy, (2) Department of Urology of the General Hospital of Sassari, Sassari, Italy.

Aim: We evaluated the usefulness of BTA and UBC in TCC.

Materials and methods: We studied consecutively 98 untreated TCC, 108 benign genito-uri-nary diseases (BD), 73 other genito-urinary cancers (OC) and 80 normal controls (C). All TCC, after trans-urethral resection, were classified according to clinical staging (9 Ta, 24 T1, 33 T2, 20 T3 and 8 T4) and pathological grading (14 G1, 28 G2, 42 G3 and 14 G4). BTA and UBC were assayed by the monoclonal antibody methods, IEMA and IRMA, respectively (cutoff values: 14 U/ml and 8 pg/l, respectively). The Chi Square and Mann Whitney U tests were used for statistical analysis.

Results: Sensitivity, specificity, PPV, NPV and accuracy were 83.6%, 75.1%, 64.6%, 89.5% and 72.4%, respectively for BTA and 53.1%, 89.4%, 72.8%, 78% and 75.6%, respectively for UBC. Specificity was calculated by combining BD and OC values; it was significantly lower for both markers in BD when compared to OC. BTA and UBC sensitivity significantly increased with advancing staging and grading, achieving maximum frequency in T4 (100% and 87.5%, respectively) and in G4 (92.8% and 69.2%, respectively) patients. Moreover, BTA sensitivity was significantly higher than UBC in both Ta-T1 stages and in T2-T3-T4 as well as in G1-G2 and in G3-G4 tumours. In particular, sensitivity was 77.7% for BTA and 11.1% for UBC in Ta patients. The combined use of BTA and UBC did not increase sensitivity. Mean BTA and UBC values were significantly higher in TCC (2905.49±11425.0 U/ml and 212.3±764.53 pg/l, respectively) compared to both BD (15.21±19.29 U/ml and 4.71±15.55 pg/l, respectively; p<0.000001) and OC (7.51±10.11 U/ml and 1.92±5.91 pg/l, respectively; p<0.000001) patients as well as to C (4.45±3.55 U/ml and 1.0±1.81 pg/l, respectively; p<0.0000002). Moreover, mean BTAand UBC values were significantly lower (p<0.0001 and p<0.000005, respectively) in Ta-T1 and G1-G2 carcinomas than in T2-T3-T4 and G3-G4. Both BTA and UBC mean levels were significantly higher in BD than in OC patients, while the comparision of both these groups with C was significant only for BTA. Conclusion: Our results suggest that BTA and UBC could be useful markers in TCC. In our cases, BTA identified more carcinomas than UBC, especially in Ta-T1 stages, while UBC better distinguished between TCC and urinary benign diseases or other genito-urinary tumours. Moreover, BTA and UBC could also be sensitive markers in TCC cases to discriminate invasive from non invasive diseases and high from low grading carcinomas.

The biodistributions in mice of a 99mTc labeled DNA-analogue (morpholinos) are influenced by chain length and base sequence.

D.J. Hnatowich, G. Liu, J. He, S. Zhang, N. Liu, Y.M. Zhang, C. Liu, S. Gupta, M. Rusckowski. Department of Radiology, Division of Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA, USA.

Aim: The influences of chain length and base sequence on the in vivo properties of radiolabeled oligomers must be established to optimize their use as radiopharmaceuticals. Materials and Methods: Several morpholinos (MORFs) were radiolabeled with 99mTc via MAG3 and investigated as DNA analogues. 1) The pharmacokinetics in normal mice were determined for three chain lengths (15, 18 and 25 mer) and two base sequences (MORF and its complement cMORF); 2) the duplex stabilities in serum and in normal mice of cMORF (conjugated to polymer PA) hybridized to MORF were compared for the 15 and 25 mer; and 3) LS174T-tumor bearing nude mice received the anti-CEA antibody MN14 (Immunomedics) conjugated either with MORF15 or MORF18 and subsequently received either 99mTc-labeled cMORF15 or cMORF18 respectively in a pretargeting strategy.

Results: In normal mice, all labeled MORFs and cMORFs accumulated only slightly in all tissues except kidney. Kidney levels increased with increasing chain length and depended on base sequence by being higher for cMORF25 vs. MORF25. Furthermore, while all other tissues cleared, kidney levels remained constant in both normal and tumored animals. When incubated in 37°C serum as the already hybridized PA-cMORF15-99mTc-MORF15 or PA-cMORF25-99mTc-MORF25, size exclusion HPLC showed an immediate and pronounced peak due to free 99mTc-MORF only in the former case. When these constructs were administered IV, whole body radioactivity levels fell more rapidly in mice receiving the PA-cMORF15-99mTc-MORF15. HPLC analysis of urine again showed instabilities only in this case. Possibly because of these differences, images obtained by pretargeting with 99mTc-cMORF15 were superior compared to 99mTc-cMORF18 and especially compared to control animals receiving 99mTc-cMORF18 without the prior administration of the antibody.

Conclusions: The pharmacokinetics of 99mTc labeled morpholinos was largely independent of chain length and base sequence except in kidneys in which accumulations were significantly higher for the longer chain lengths and significantly different for cMORF vs MORF. Furthermore, despite high hybridization affinities, cMORF15-99mTc-MORF15 was found to be unstable and thus subject to duplex dissociation in serum and in vivo. These results show that altering chain length and base sequences may be a useful method of improving upon the phar-macokinetics of radiolabeled oligomers in nuclear medicine imaging studies.

High-sensitive thyroglobulin immunoradiometric assay in differentiated thyroid cancer management

L. Giovanella, L. Ceriani, D. De Palma, S. Garancini. Department of Nuclear Medicine, Varese, Italy.

Aim: Circulating human thyroglobulin (hTG) measurement have a pivotal role in the management of patients affected by differentiated thyroid cancer (DTC). The present study was undertaken by employing a new developed high-sensitive hTG immunoradiometric assay (functional sensitivity 0.2 ng/mL) to evaluate its diagnostic performance in patients affected by radically cured and relapsing DTC and to set the most appropriate cut-off point for DTC management.

Material and Methods: We retrospectively selected 172 patients without signs of recurrence after primary treatment and 45 patients with recurrences from DTC. Serum samples were collected during l-thyroxine (T4) suppressive therapy (onT4) and four weeks after T4 withdrawal (offT4) and hTG measured by a specific high-sensitive IRMA assay (DYNOtest® Tg-plus, BRAHMS Diagnostica GmbH, Berlin, Germany). Sera showing the presence of AbhTG or hTG-recovery less than 80% were excluded from the study. ROC curve analysis was performed to select the best cut-off levels and diagnostic performance of the marker evaluated. Results: By using onT4 cut-off level of 0.2 ng/mL and offT4 cut-off level of 0.5 ng/mL we obtained a sensitivity/specificity/accuracy profile of 0.91/0.98/0.96 and 0.98/0.97/0.97, respectively. We found onT4-hTG false-negative results in 4 patient with local recurrence (n=2) or cervical lymph-node metastasis (n=2) while only one patient with local recurrence showed negative offT4-hTG. However, onT4 and offT4-hTG false-negative results were found in 9 and 5 patients, respectively, when 1.0 ng/mL cut-off level was employed. Conclusions: Basing on our data, we conclude that DYNOtest® Tg-plus assay is very effective and accurate in evaluation of patients with DTC allowing a significant increase in diagnostic sensitivity respect 1st generation IRMA methods.

Investigation of p21WAF-1/CIP-1 as a Potential Target for Molecular Imaging of Anti-tumour Response in Breast Cancer

H.M. Hu (1,3), J. Wang (1), P. Chen (1), K.A. Vallis (2), R.M. Reilly (1,3). (1) Division of Nuclear Medicine, University Health Network, (2) Department of Radiation Oncology, University Health Network, (3) Department of Pharmaceutical Sciences, University of Toronto, Toronto, Canada.

The cyclin-dependent kinase inhibitor, p21WAF-1/CIP-1 is a key regulatory protein which controls cell cycle arrest and apoptosis in breast cancer cells in response to treatment with cytotoxic agents or y-radiation. Aim: To determine the magnitude of induction of p21WAF-1/CIP-1 inhuman breast cancer cells following treatment in vitro with camptothecin (CPT), y-radiation or epidermal growth factor (EGF) as an indicator of its potential usefulness as a target for molecular imaging. Methods: MDA-468 (high EGFR, p53mu) and MCF-7 (low EGFR, p53wt) breast cancer cells were treated with EGF (0.5-10 nM), CPT (0.1-4 pM) or with y-radiation (2-20 Gy). The induction of p21WAF-1/CIP-1 was quantified by Western Blot at 0,4-6, 8, 24-48 h after treatment using (3-actin as an internal control. Cell cycle analysis was performed by flow cytome-try using propidium iodide. High concentrations of EGF are growth inhibitory to MDA-468 cells and promote apoptosis. Results: Treatment of MDA-468 with y-radiation did not induce p21WAF-1/CIP-1 due to p53 mutation. The p21WAF-1/CIP-1 /actin ratio was increased when MDA-468 cells were treated with CPT or EGF compared to untreated controls. Maximum p21WAF-1/CIP-1 /actin ratio for MDA-468 cells was 5.4:1 for CPT (4pM) and 2:1 for EGF (5 nM) and occurred at 24 h. Induction of p21WAF-1/CIP-1 in MDA-468 cells was associated with G1 arrest. Treatment of MCF-7 cells with EGF did not induce p21WAF-1/CIP-1. Nevertheless, the p21WAF-1/CIP-1 /actin ratio was increased when MCF-7 cells were treated with CPT or y-radiation compared to untreated controls. Maximum p21WAF-1/CIP-1 /actin ratio for MCF-7 cells was 4.8:1 for CPT (0.5 pM) and 3.5:1 for y-radiation (20 Gy) and occurred at 24 h. Induction of p21WAF-1/CIP-1 in MCF-7 cells was associated with prolonged S-phase (CPT) or G2 arrest (y-radiation). Conclusion: Moderate (up to 5-fold) increases in p21WAF-1/CIP-1 expression were observed in breast cancer cells following treatment with cytotoxic agents or y-radiation, suggesting that p21WAF-1/CIP-1 is a useful target for molecular imaging of anti-tumour response in breast cancer. We are currently designing internalizing radioimmunoconjugates which could target p21WAF-1/CIP-1 intracellularly in breast cancer cells for molecular imaging of the disease.

This work was supported by US Army Predoctoral Traineeships, the Cancer Research Society Inc., and the Breast cancer Society of Canada.

Relationship of tumoral Cathepsin D and Hyaluronic Acid contents with histological type of gastric carcinoma

T. Allende (1), J.M. Del Casar (2), P. Raigoso (1), N. Zeidan (1), J.P. Suarez (1), B. Llana (1), A. Alvarez (1), O. Abdel-Lah (3), C. Roiz (1). (1) Department of Nuclear Medicine of the Hospital Central de Asturias, Oviedo, Spain, (2) Department of Surgery of the Hospital de Jove, Gijon, Spain, (3) Department of Surgery II of the Hospital Central de Asturias, Oviedo, Spain.

AIM: Hyaluronic acid (HA) is an ubiquitous polysaccharide wich is found on the cell surface and extracellular matrix of virtually all tissues. Cathepsin D (Cat D) is an aspartyl protease that is normally localized within lysosomes and is involved in protein catabolism and tissue remodeling. The aim of this study was to evaluate the HA and Cat D contents in cytosolic samples from tumors and paired normal surrounding mucosa from gastric cancer patients, as well as their possible relationships with clinicopathological parameters. MATERIALS AND METHODS: We analyzed 78 gastric adenocarcinoma patients, 52 males and 26 females, who underwent surgical resection. The patients'age ranged from 42 to 85 years (mean ± SD: 68.2 ± 9.4 years). Gastric carcinoma tissue and normal surrounding mucosa samples were obtained at the thime of surgery. HA was measured in cytosolic samples using a radioligand binding assay (Pharmacia AB, Sweden) and Cat D by an immunoradio-metric assay (IRMA CIS, France). To analyze the distribution of HA and Cat D values, Kolmogorov-Smirnov test was used and to compare the differences in marker content between groups, Mann-Whitney U and Kruskal-Wallis tests were applied. Results were considered statistically significant at a 5% probability level (p<0.05)

RESULTS: HA and Cat D cytosolic contents ranged widely both in tumors (HA: 327-24,523 ng/mg prt; Cat D: 4-270 pmol/mg prt) and in the surrounding mucosa samples (HA: 50720,782 ng/mg prt; Cat D 1-97 pmol/mg prt).

There were no significant differences in HA content between tumors (3748 ± 411ng/mg prt) and non-neoplastic surrounding mucosa (4198 ± 379 ng/mg prt). By contrast Cat D was significantly higher (p<0.001) in tumors (52 ± 4 pmol/mg prt) than in non-neoplastic mucosa (31 ± 2 pmol/mg prt). The tumoral content of both markers was significantly higher (p<0.005) in diffuse type carcinomas than in intestinal type ones ( HA: 6027 ± 1099 vs. 2735 ± 242 ng/mg prt. Cat D: 75 ± 13 vs. 42 ± 3 pmol/mg prt).

CONCLUSIONS: 1/.- Our results show a wide variability of HA and Cat D cytosolic contents in gastric tumors and paired non neoplastic mucosa samples. 2/.- The higher content of Cat D found in tumors compared to normal mucosa may be due to the processes associated with malignant transformation. 3/.- The association of HA and Cat D levels higher in diffuse compared to intestinal type carcinomas suggests that these two biological markers may influence the growth pattern of gastric carcinomas

Comparative study of the biodistribution pattern of 123I-hEGF and 99mTc-HYNIC-hEGF in wild type NMRI-mice and in tumour inoculated athymic mice

B. Cornelissen (1), T. Thonissen (1), V. Kersemans (1), C. Vandewiele (2), O. Boerman (3), W. Oyen (3), G. Slegers (1). (1) Laboratory for Radiopharmacy, Ghent University, Ghent, Belgium, (2) Division of Nuclear Medicine, Ghent University Hospital, Ghent, Belgium, (3) Dept. of Nuclear Medicine, University Medical Center, Nijmegen, The Netherlands.

Aim: Human EGF is a growth factor protein whose receptor EGFR is commonly known to be overexpressed in human colon and head and neck cancers. 123I-hEGF and 99mTc-HYNIC-hEGF are to be used as a predictive tool to assess early therapy response prediction and therapy monitoring of chemotherapeutics such as farnesyl transferase inhibitors, which interfere with the signal transduction pathways of these receptors. The goal of these experiments was to perform a comparative study of the biodistribution of 123I-hEGF and 99mTc- HYNIC-hEGF in wild type NMRI mice and in tumour inoculated athymic mice.

Materials and methods: 123I-hEGF was synthesised using the common Iodogen method. Coupling of 99mTc-HYNIC to hEGF was performed. Biodistribution patterns in NMRI mice were obtained by dissection at various intervals p.i. and scintillation counting of all organs of interest. The concentration of radioactivity was expressed as percentage of the dose/g of tissue and decay corrected. LoVo-cells, previously shown to bind the 123I-hEGF in vitro, were inoculated subcutaneously in athymic mice. Activity distribution in tumour-inoculated mice was achieved using planar gamma scintigraphy and region of interest (ROI) analysis. Results: High specific activities were achieved (typically 500 pCi/pg for the Tc-derivative). Radiochemical purities were high (radiochemical purities > 93% for 123I-hEGF; > 95% for 99mTc-HYNIC-hEGF). In vitro binding capabilities of both radiolabelled proteins were compared using Scatchard analysis on EGFR-positive cancer cell lines. In the case of 123I-hEGF stomach activity proved rapid dehalogenation. Liver uptake due to endosomal activity was observed in both cases but was lower in the case of 99mTc-HYNIC-hEGF. Significant tumour uptake was shown (tumour-to-background ratios varied between 2.8 and 3.3), despite of the fact that the 123I-hEGF was partially dehalogenated. Uptake was maximal 1.5 hours after injection. Activity uptake using 99mTc-HYNIC-hEGF is probably higher due to a higher specific activity of the latter.

Conclusion: Two radiolabelled forms of the growth factor hEGF were compared for biodistribution patterns in wild type and tumour inoculated mice: 123I-hEGF and 99mTc-HYNIC-hEGF. The latter is most likely the better tracer for early therapy response prediction and monitoring therapy, due to lower dissociation of the isotope, lower cost and higher specific activity.

Cathepsin D a prognostic marker in resectable gastric cancer

T. Allende (1), F. Vizoso (2), P. Raigoso (1), N. Zeidán (1), B. Llana (1), J.P. Suárez (1), M.L. Domínguez (1), L. Bernardo (1), L. Sanz (3). (1) Department of Nuclear Medicine of the Hospital Central de Asturias, Oviedo, Spain, (2) Department of Surgery of the Hospital de Jove, Gijón, Spain, (3) Department of Surgery of the Hospital de Arriondas, Arriondas, Spain.

AIM: Cathepsin D (Cat D) is an intracellular aspartic proteinase that plays a role in the prote-olysis of intra and extracellular proteins. The expression of Cat D has been associated with apoptotic events and tumor metastasis. In this prospective study we determinate the values of cytosolic Cat D in complete resected gastric carcinoma, in order to stablish its impact on survival and relapse-free survival.

MATERIALS AND METHODS: This study include 60 patients with primary gastric adenocarcinoma. Samples were obtained from all cases and adjacent mucosa samples were also obtained from 48 patients. Age ranged from 42 to 85 (average 68,4±9,6 years). Clinicopathological characteristics were studied and disease recurrence and survival status were evaluated. Mean follow-up period was 41,5 months (range 1 to 97 months). Cat D was determined by an immunoradiometric assay (CIS-ELSA, France). Statistical analysis of data was made using non-parametric rank methods. Probabilities of overall survival were calculated with the Kaplan-Meier method and differences between curves were evaluated with logrank test. Statistical significance was considered at 5% probability level (p<0.05). RESULTS: The tumor content of Cat D ranged from 4 to 247 pmol/mg prt and from 6.4 to 97.7 pmol/mg prt in adjacent mucosa samples. Statistical analysis did not show significant association between Cat D levels and all of clinicopathological parameters, except age from patients (p=0.02) so that, younger patients have lower Cat D tumor levels than older ones [ 486.8 pmol/mg prt (<65 years), 5.1-247.6 pmol/mg prt (>65 years) ]. Differences between overall survival curves were significant (p=0.002). Patients with lower Cat D show prolonged survival and tumor stage and Cat D showed independent prognostic value on survival of patients with complete resection of gastric cancer. Respecting to relapse-free survival differences were also significant (p=0.02) in the same way that the former, but not as independent prognostic factor.

CONCLUSIONS: 1/.- There is a wide variability of Cat D levels in resected gastric cancer, so in neoplastic as in non neoplastic tissue. 2/.- Cytosolic Cat D levels were significantly higher in neoplastic tissue than those found in paired mucosa samples. 3/.- Statistical analysis did not show significant association between Cat D levels and clinicopathological parameters, except age from patients. 4/.- Tumors with lower Cat D levels have a better clinical outcome in terms of longer overall and disease-free survival. 5/.- Cat D shows and independent prognostic value on overall survival but not in relapse-free survival

TATI and Cytoceratins (UBS and CYFRA 21-1) in the diagnosis of bladder transitional cell carcinoma

L. lordanidou (1), L. Stenos (2), K. Sotirakoglou (3), E. Trivizaki (1), S. Saranti (1), P. Natsis (1), K. Pateniotis (1), P. Koutsiouba (1). (1) Department of Nuclear Medicine, (2) Department of Urology, (3) Department of Statistics of the University, Athens, Greece

PURPOSE: The aim of this study was to evaluate the usefulness of Cytokeratin-19 fragments (CYFRA 21-1), Tumor Associated Trypsin Inhibitor ( TATI ), and Cytokeratin 8 and 18 Urinary fragments (UBC) in serum and urine samples for the detection of bladder cancer, in comparison with urinary cytology.

PATIENTS AND METHODS: We measured serum and urine samples of 80 individuals , 20 healthy volunteers, 20 with benign urologic disorders, and 40 patients with histologically proven bladder transitional cell carcinoma(TCC), before any endoscopic examination. Urinary cytopathology was also performed.

RESULTS: Taking as cutoffs the 22 mg/l for TATI, 2.8 ng/ml for CYFRA21-1 and 12?g/l for UBC in urine samples, we found that the overall sensitivity was 79.4%, 55.1%, and 50% respectively when the overall sensitivity for urine cytology was 47%.

According to the histological stage, TATI was significantly more sensitive in stages Ta and T1 (84.2%) vs CYFRA21-1 (47.3%), UBC (31.5%),and cytology (39.5%) while in advanced stages the sensitivity was similar for all tumor markers and also for cytology. For the TATI and CYFRA21-1 sensitivity was much lower in serum samples in comparison with the urine ones.

CONCLUSIONS: According to our preliminary results there is a clear superiority of TATI in urine samples for the detection of bladder transitional cell carcinoma in early disease stages, while CYFRA21-1 and UBC can be considered as additional tools in the evaluation of TCC patients.

raphy was used to better predict in vivo events. The exIn-vivo vitro brain autoradiography may better predict in-vivo events.showed Similar similar IC50 values in all regions of FP-TZTP were observed using [18F]-FP-TZTP as the radioligand in all regions; the Bmax for all regions Bmax was constantly high and constanthigh and similar IC50 values were calculated in all regions using [18F]FP-TZTP as the radioligand. Regions with a larger percentage of M2 subtype showed Llower Bmax values were obtained in M2 rich regions with [3H]-NMS and either cold NMS or FPTZTP. We also observed that FP-TZTP blocked radioactive [18F]FP-TZTP with a stronger affinity than NMS, and . On the other hand, NMS blocked radioactive [3H]NMS with a stronger affinity than found with FP-TZTP.

Conclusion: We showed that FP-TZTP and NMS compete for two distinct binding sites. The KiEC50 for agonist blocking of antagonist or antagonist blocking of agonist binding occurred at higher concentrations than when the radioligand was blocked by the same compound. Also, we proved that FP-TZTP specific intracellular binding for M1-M5 CHO cells was independent of temperature, as there was no statistical difference between the results at 37°C or 4°C. Energy dependent receptor internalization was not involved in the uptake of [18F]-FP-TZTP in M1-M5 CHO cells. Therefore, internalization is not responsible for the M2 selectivity of FP-TZTP. In addition, we proved that FP-TZTP and NMS compete for two distinct binding sites. The Ki for agonist blocking of antagonist or antagonist blocking of agonist binding occurred at higher concentrations than when the radioligand was blocked by the same compound. What does one need to show non-competitive inhibition?

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition MOLECULAR BIOLOGY & OTHERS

Is Internalization Responsible for M2 Selectivity of FP-TZTP?

L. Ravasi (1,2), K. Shimoji (1), E.M. Jagoda (1), D.O. Kiesewetter (1), W.C. Eckelman (1). (1) Positron Emission Tomography Department, National Institutes of Health, Bethesda, MD, U.S.A., (2) Istituto di Scienze Radiologiche, Universita' degli Studi di Milano, Milano, Italy.

Is IInternalization or Kinetic Mismatch: Which One is Responsible for the M2 Selectivity of FP-TZTP?

L. Ravasi, K. Shimoji, E.M. Jagoda, D.O. Kiesewetter and W.C. Eckelman. PET Dept. Clinical Center, NIH, Bethesda MD.

Aim: Development of a M2 subtype selective ligand may allow both an early diagnosis of Alzheimer's disease and the follow up of those patients to evaluate the progression of such pathologyeffect of therapeuticy efficacy. Previous autoradiographic studies with 18F-[3-(3-(3-[18F]-fluoropropyl)thio)-1,2,5-thiadiazol-4-yl]-1,2,5,6-tetrahydro-1-methylpyridine ([18F]FP-TZTP) in brains of M1-, M1, M2-, M3-, and M4-knockout mice displayed demonstrated M2 receptor selectivity (Life Sciences 2001J. Nucl. Med., 2002). We conducted In in vitro studies were preformed to determine if receptor internalization was an important factor to explain the M2 subtype muscarinic receptor (mAChR) selectivity of [18F]-FP-TZTP. Methods: The antagonist 3H-N-Methyl-Scopolamine (NMS) or the agonist 18F-FP-TZTP binding In vitro binding assays were conducted on genetically transformed Chinese hamster ovarian cells (CHO) expressing the 5 subtypes of mAChR at 4°C for 120 minutes and 37°C for 30 minutes. The assays were conducted using either [3H]-N-methyl-scopolamine (NMS), a muscarinic antagonist, or [18F]FP-TZTP, an agonist. For the [18F]-FP-TZTP assays, N-methyl-atropine (10-5M) was used to block extracellular binding and FP-TZTP (10-4M) was used to determine non-specific binding (NSB). Using ex-vivo autoradiography, rat Rat brain slices were incubated with [3H]-NMS / [18F]-FP-TZTP at different concentrations (10-5 to 10-11 M) of FP-TZTP and NMS for 60 minutes at room temperature. Radioactivity retention was determined using in-vitro autoradiography. IC50 was calculated from the curves. Results: [18F18F-]]FP-TZTP specific intracellular binding (SBi) at 37°C for M1-M5 was 72-5, 78, 81, 81, and 72%, for M1-M5 Respectively. At 4° C SBi was and 86 , 100, 72-, 75, and 10092% for M1-M5, at 4°C, respectively. The remaining specific binding is was extracellular. Total NSB is was approximately less than 15% of the total binding. Since the CHO cells do not represent the in vivo cellular environment of M1-M5 receptors, in vitro brain autoradiog-

Non-invasive dual imaging of human anaplastic thyroid cancer cells using human sodium/iodide symporter(hNIS) - enhanced green fluorescent protein(EGFP) gene

K.I. Kim, J.K. Chung, J.H. Kang, Y.J. Lee, J.H. Shin, H.J. Oh, J.M. Jeong, D.S. Lee, M.C. Lee. Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.

Objectives: We are developing a non invasive reporter gene system using nuclear imaging (hNIS) and optical imaging (EGFP). We evaluated this dual reporter gene system in human anaplastic thyroid cancer cells, ARO, during in vitro therapeutic intervention. Methods: We constructed hNIS/EGFP fusion gene by the insertion of hNIS gene into pEGFP-N1(Clontech co.) and transfected it into human anaplastic thyroid cancer cell line, ARO by Liposome. Geneticin was used for the selection of the hNIS/EGFP stable transfectant. To evaluate the function of hNIS, the inhibition study was examined with 1mM potassium per-chlorate. We monitored hNIS/EGFP expression and counted cell numbers for viability assessment at 12, 24 and 48h after adding adriamycin. The activity of hNIS was monitored by iodide uptake, and EGFP protein was checked by fluorescent microscopy. The cells were counted in hemocytometer using trypan blue exclusion.

Results: ARO-hNIS/EGFP accumulated 76.65±3.98 pmol of iodide per 106 cells. Potassium perchlorate inhibited completely the uptake of I-125. ARO-hNIS/EGFP cells was highly fluorescent in fluorescent microscope. While wild type ARO was not. It suggested that the function of hNIS and EGFP was still active in spite of fusion protein of hNIS and EGFP. ARO-hNIS/EGFP cells showed complementarily gradual decrease in iodide uptake, viability and green fluorescence according to time point (12, 24, 48h) after adding adriamycin.

I-125 uptake(pmol/10' cells) 127.96 94.95 35.66

Viable cell numbers 1.19710' 6.507105 2.497105

Iodide uptake was significantly correlated to viable cell numbers(r=0.9694). Conclusions: In vitro model, expression of hNIS/EGFP fusion protein correlated among iodide uptake, fluorescent activity and viable cell numbers. These results suggest that hNIS/EGFP fusion protein can be a useful tool for non-invasive dual imaging.

Enzyme Inhibition Kinetics and Specific Binding of Iodine Labeled Phenylethyl-beta-D-Thiogalactopyranoside Against E. Coli beta-Galactosidase

S.S. Byun, K-H. Lee, J-Y. Paik, J.H. Choi, Y.S. Choe, Y. Choi, S.E. Kim, B-T. Kim. Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

Objective. Phenylethyl-p-D-thiogalactopyranoside (PETG) is a specific inhibitor against E. Coli p-galactosidase, a widely used reporter enzyme. We synthesized iodine labeled PETG and investigated its interaction with p-galactosidase protein to evaluate its potential for assessing lac-Z gene expression.

Methods. [125I]-iodoPETG was synthesized from a precursor and HPLC purified. Specific binding was evaluated by column chromatography and gel electrophoresis autoradiography after incubation with p-galactosidase in the presence or absence of cold PETG. Kinetics of p-galactosidase activity was measured by spectrophotometry assays of O-nitrophenyl-p-D-galactopyranoside hydrolysis rates in the presence of 0, 1, 10, or 100 ?M of PETG or iodoPETG. [125I]-iodoPETG uptake was evaluated in cultured COS-7 cells 48 hr after transfec-tion with the lac-Z gene.

Results. Chromatography demonstrated an early radioactivity peak consistent with protein binding of [125I]-iodoPETG. Gel electrophoresis confirmed a distinctive band of radioactivity concordant to the band on protein staining. Enzyme kinetic studies showed that iodoPETG retained significant enzyme inhibitory potency with an inhibition constant (Ki) of 43.7 ?M, which was slightly less potent but comparable to that of PETG (Ki = 7.9 ?M). COS-7 cells transfected with the LacZ gene showed significantly higher [125I]-iodoPETG uptake compared to non-transfected cells (p<0.0001).

Conclusion. These results regarding binding, enzyme inhibition and cell uptake of radioio-dine labeled PETG against p-galactosidase suggests that it may have potential for use in lac-Z reporter gene expression monitoring.

In vitro Characteristics of Sodium/Iodide Symporter Gene Transfected Human Cancer Cell lines

J.H. Kang, J.K. Chung, Y.J. Lee, J.H. Shin, K.I. Kim, H.J. Oh, J.M. Jeong, D.S. Lee, M.C. Lee. Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.

Aim: The sodium iodide symporter (NIS) is responsible for the transport of iodide into thyroid cells. The ability of thyroid cancer cells to concentrate radioiodine leads to diagnosis and treatments of differentiated thyroid carcinoma. To deposit the radioiodine to nonthyroid carcinoma and anaplastic thyroid carcinoma, we transfected hNIS gene to several human cancer cell lines and determined in vitro characteristics of iodide uptake and efflux in these cell lines. Methods: The human cancer cell lines, SK-Hep1 (hepatocellular carcinoma cell), ARO (anaplastic thyroid carcinoma cell) and SNU-C4 (colon carcinoma cell) were transfected with hNIS/pcDNA3 using the Lipofectamine. Geneticin was used for the selection of hNIS expressing cell lines. We determined the uptake and efflux assay of hNIS -transfected and wild type cell lines with I-125, Tc-99m, and Re-188 according to time courses. Lithium chloride, sodium ion competitor, was applied for the blocker of iodide reuptake. Results: The expression of hNIS from human cancer cell lines was confirmed by RT-PCR. In the iodide uptake, the hNIS gene transfected SK-Hep1 (SK-Hep1/NIS), ARO (ARO/NIS), and SNU-C4 (C5/NIS) accumulated up to 150, 35, and 3.5 times higher than did non-transfected cells, respectively. Potassium perchlorate completely inhibited the uptake of I-125, Tc-99m, and Re-188. The iodide uptake of SK-Hep1/NIS remained to be plateau to 120 min. However, iodine uptake of ARO/NIS and C5/NIS showed to be the highest at 30 - 40 min and then was declined rapidly. In case of Tc-99m and Re-188, SK-Hep1/NIS deposited the 112 and 87 times higher than did non-transfected cells, respectively. The iodide efflux of SK-Hep1/NIS was delayed compared to those of ARO/NIS and C5/NIS. Lithium chloride increased efflux of iodide in SK-Hep1/NIS.

Conclusion: The several human carcinoma cell lines transfected with hNIS gene induced the accumulations of radioiodide. SK-Hep1/NIS significantly accumulated the Tc-99m, and Re-188 as well as I-125 and showed delayed efflux. The hNIS transfected cancer cell lines may be applied for the cancer therapy and molecular imaging for diagnosis.

Structural Requirements of Metomidate for High Affinity Binding to Adrenal Membranes

M.L. Berger (1), A. Schirbel (2), F. Hammerschmidt (3), I. Zolle (4). (1) Brain Research Institute, University Vienna, Austria, (2) Clinic of Nuclear Medicine, University Wuerzburg, Germany, (3) Institute of Organic Chemistry, University Vienna, Austria, (4) Department of Nuclear Medicine, AKH, Vienna, Austria.

Aim: Etomidate (ETO) and the methylester metomidate (MTO) are potent inhibitors of 11 p-hydroxylation in the adrenal cortex (1,2). The development of MTO for adrenal scintigraphy has produced a number of MTO derivatives and 4-[131I]iodophenyl-MTO ([131I]MTO) as a radiotracer (3). Here we characterize the specific binding of [131I]MTO to adrenal membranes and present data on the potencies of derivatives. Scheme of Derivatisation

R_R]_IT_

H3C H5C7 H Etomidate (ETO)

H3C H5C9 I 4-iodo-ETO_

H3C H3C H Metomidate (MTO)

H^C H^C I 4-iodo-MTO_

Metomidate [(R)-1-(1-phenylethyl)- H_H3C H dme-MTO_

imidazole-5-carboxy-methylester] H5C9_H3C_H_MTO-et_

Materials and Methods: [131I]MTO (20-40.000 cpm) and 4-iodo-MTO-carrier (final ligand conc. 2 nM; spec. act. 0.37-0.73 GBq/^mol) were incubated in 0.5 mLof 10 mM K+/HEPES buffer pH 7.1 + 150 mM NaCl with rat adrenal membranes (0.2 mg tissue/vial) for 30 min at 23°C. Bound ligand was recovered by filtration, filters rinsed twice and measured in a gamma-counter.

Results: Kinetic studies demonstrated fast association and dissociation. Saturation analysis resulted in Kd = 7.4 nM and Bmax = 2.4 pmol/mg tissue. Table 1 shows the potenties of various compounds obtained by inhibition studies. Most efficient displacement was obtained with medium sized esters (ETO and ITO). Substitution of the phenyl ring with iodine in p-position resulted in a slight decrease of affinity; nevertheless, 4-[131I]MTO was a suitable radioligand for binding studies. Only the R-isomer showed high potency. The free carboxylic acid was inactive. The substrate DOC and known inhibitors of P45011 p (ketoconazole and metyrapole) were effective at micromolar concentrations.

Table 1 Inhibition of [131I]MTO binding by MTO derivatives and other compounds (ITO, isopropyl-MTO; PTO, n-propyl-MTO; DOC, 11-deoxycorticosterone)

IC50 (nM) IC50 (nM) IC50 (nM) IC50 (MM)

MTO 3.69 4-I-MTO 9.0 (R)-MTO 3.69 DOC 0.89

ETO 1.08 4-I-ETO 4.37 (S)-MTO 492 ketoconazole 0.71

ITO 1.42 3-I-MTO 4.44 dme-MTO 28.8 metyrapol 1.02

PTO 2.89 4-me-MTO 3.58 (R)-MTO-et 11.0 free acid 123

Conclusion: [131I]MTO binds with high affinity to a single class of binding sites and has fast on- and off-kinetics. The ester-group is essential for enzyme binding. Only compounds known to block adrenal cortisol production inhibit specific [131I]MTO binding.

Literature remove by abstract coordination

Tc-99m-MIBI and Tc-99m-tetrofosmin uptake in tumor cells. Influence of ion transport systems and membrane potential.

M. Rodrigues (1), W. Kalinowska (2), A.A. Aghajanian (1), C. Zielinski (2), H. Sinzinger (1). (1) Department of Nuclear Medicine, (2) Clinical Division of Oncology, Department of Internal Medicine I, University Hospital, Vienna, Austria.

Aim: Tc-99m-MIBI and Tc-99m-tetrofosmin uptake in tumor cells was found to depend on cellular metabolic activity, but the precise mechanisms of this uptake are not yet well known. This in-vitro study investigates the role of Na/K-ATPase pump, calcium channel inhibition and mitochondrial potential on the uptake of Tc-99m-MIBI and Tc-99m-tetrofosmin in well-characterized human tumor cells.

Methods: The human differentiated breast adenocarcinoma MCF-7, poorly differentiated breast adenocarcinoma SK-BR-3, synovial sarcoma SW 982 and chondrosarcoma SW 1353 cell lines (1x10E6 cells/ml incubation medium) were incubated (37°C) with ouabain (Na/K-ATPase pump inhibitor; 100 pM and 1mM; 15 and 30 minutes), verapamil (calcium channel inhibitor and competitive inhibitor of Pgp; 10 and 100 pM; 15 and 30 minutes), nigericin (increases mitochondrial potential and disrupts cell membrane potential; 5 and 50 pg/ml; 15 minutes) and carbonyl cyanide m-chlorophenylhydrazone (CCCP) (depolarizes mitochondrial membrane; 10 and 100 pM; cells under basal conditions or preincubated with nigericin; 10, 30 and 60 minutes). Tc-99m-MIBI and Tc-99m-tetrofosmin uptake (at 10, 30 and 60 minutes) in cells incubated with chemical agents was expressed as a percentage of respective control values of tracer uptake (i.e. uptake in cells not preincubated with chemicals) obtained for that batch of cells.

Results: Ouabain and verapamil decreased Tc-99m-MIBI uptake by 0.64-54.83 % and 2.2955.22 %, and Tc-99m-tetrofosmin uptake by 3.77-51.43 % and 1.09-51.98 %, respectively. Nigericin increased Tc-99m-MIBI uptake by 3.08-70.68 % and Tc-99m-tetrofosmin uptake by 0.45-62.44 %. Addition of CCCP to cells under basal conditions released 0.95-39.49 % and 2.17-37.32 % of accumulated Tc-99m-MIBI and Tc-99m-tetrofosmin, whereas in cells preincubated with nigericin CCCP released 5.79-46.22 % and 0.75-37.73 % of accumulated Tc-99m-MIBI and Tc-99m-tetrofosmin, respectively. No significant difference in cell viability (measured by trypan blue dye exclusion technique) was found between preincubation and after incubation with tracers or chemical agents.

Conclusions: Tc-99m-MIBI and Tc-99m-tetrofosmin uptake in tumor cells is dependent on both mitochondrial (Tc-99m-MIBI > Tc-99m-tetrofosmin) and cellular (Tc-99m-tetrofosmin > Tc-99m-MIBI) membrane potential. Tc-99m-MIBI and Tc-99m-tetrofosmin seem promising for in-vivo imaging of tumor with cells rich in mitochondria or enhanced mitochondrial activity. Verapamil does not seem useful for evaluating Pgp status in the tumor cell types investigated.

Optimization of the labelling efficiency of dextrans at different conditions of pH and reductant agent

R. Arenas, A. Delgado, A. Ramirez, M.A. Muros, M.J. Acosta, G. Sabatel, S. Ortega, C. Ramos, J.M. Llamas. Department of Nuclear Medicine, Granada, Spain.

PURPOSE: Evaluating the labelling conditions of pH and reductant agent for dextrans of different molecular weights in order to optimize the labelling yield.

MATERIAL AND METHODS: 27 vials were prepared with dextrans of different molecular weights, at different pH conditions and quantities of C^Sn.^O. Molecular weights of dextrans used were 200-300, 60-90 and 70; pH was 6, 7 and 8; and quantities of stannous chloride were 0.75, 1 and 2 mg.

pH was finally accurately adjusted with 1 N NaOH solution.

Subsequently, labelling of vials was carried out by adding 100 mCi of 99mTcO4- in 2-3 ml of 0.9% ClNa solution.

After 15 minutes of incubation at room temperature, radiochemical purity was determined by performing a chromatographic control, wich employes ITLC-SG as stationary phase and 0.1 N HCl as mobile phase to separate colloids, and Whatmman 17 paper and acetone as mobile phase to obtain free perthecnectate.

RESULTS:

DEXTRANS: 200-300 pm

pH= 6 96,4% ± 0,20 0,75 mg Cl2Sn2H2O 95,5% ± 0,65

pH= 7 95,7% ± 0,22 1 mg Cl2Sn2H2O 96,3% ± 0,36

pH= 8 95,8% ± 0,88 2 mg Cl2Sn2H2O 96,1% ± 0,50

DEXTRANS: 70 pm

pH= 6 93,9% ± 0,93 0,75 mg Cl2Sn2H2O 93,3% ± 1,20

pH= 7 92,7% ± 0,64 1 mg Cl2Sn2H2O 95,0% ± 1,12

pH= 8 94,7% ± 1,39 2 mg Cl2Sn2H2O 93,1% ± 0,60

DEXTRANS: 60-90 pm

pH= 6 95,5% ± 1,62 0,75 mg Cl2Sn2H2O 94,9% ± 1,17

pH= 7 95,4% ± 0,73 1 mg Cl2Sn2H2O 96,6% ± 0,56

pH= 8 95,3% ± 1,23 2 mg Cl2Sn2H2O 94,6% ± 0,87

CONCLUSIONS: Excellent labelling yields were obtained with dextrans used at different pH conditions and reductant agent.

No differences were found regarding different dextrans, pH and concentrations of C^Sn used in the experiment.

(*) This communication is part of the Researching Proyect n° 98/189, supported by the Andalusian Health Service.

Can Tc-99m-MIBI assess MDR-modulators?

K.N. Nakamura (1), Z.J.L. Li (2), H.F. Fujii (1), A.K. Kubo (1). (1) Department of Radiolgoy, Keio University School of Medicine, Tokyo, Japan, (2) Department of Nuclear Medicine, Second Clinical Hospital, China Medical University, Shenyang, China.

Many multidrug resistance (MDR)-modulators have been developed so that it is urgent to assess these modulators in vivo system. Tc-99m-MIBI scintigraphy is a promise tool to predict the chemo-sensitivity of tumors in vivo.

Objectives: The aim of this study is to evaluate the Tc-99m-MIBI uptakes as the assessment of MDR-modulators.

Materials and Methods: Human epidermoid carcinoma cell line, KB-31 and KB-G2 (KB-31 was transfected with mdr-1 to overexpress P-glycoprotein (P-gp)) were used throughout experiments. Cells were incubated with Actinomycin D (ACT-D), Vincristine (VCR), Paclitaxel (TXL), or Doxorubicin (DXR) for 60 hours to study their cytotoxicity by MTT assay. For the Tc-99m-MIBI uptake experiments, cells were incubated with Tc-99m-MIBI in the tube for 2 hours, followed by counting the activity in the cell. Cytotoxicity of drugs and Tc-99m-MIBI uptake in the cells were also studied in the presence of Verapamil or anti-Pgp monoclonal antibody (UIC2) that is directed against an external epitope. Results: There were significant differences between KB-31 and KB-G2 for Tc-99m-MIBI uptake (0.2 vs 0.05 [in]/[out]/mg protein of cells), and for IC5o of ACT-D, VCR, TXL and DXR (5.9 vs 0.8, 4.0 vs 1.0, 4.3 vs 2.2, and 158 vs 47 ng/ml, respectively). In the presence of 0.04 mg/ml of Verapamil or 0.01 mg/ml of UIC2, Tc-99m-MIBI uptake in KB-G2 was reversed to 0.2 or 0.18 [in]/[out]/mg protein of cells, respectively. When KB-G2 cell was incubated with IC50 of ACT-D, VCR, TXL and DXR in the presence of 0.01 mg/ml of Verapamil, the survival fraction was decreased to 27%, 3.6%, 23%, and 8.8% respectively; indicating that Verapamil reversed the resistance of KB-G2 to all drugs we studied. On the other hand, the effect of UIC2 (0.017 mg/ml) was not found on the resistance of KB-G2 to TXL and DXR, whereas the survival fraction of KB-G2 by the exposure of IC50 of ACT-D or VCR together with UIC2 was decreased to 38% or 39%, respectively.

Conclusion: Our results suggested that Verapamil or UIC2 would alter the efflux of Tc-99m-MIBI as well as drugs we studied by blocking P-gp function, but that it did not always relate to the reversal of the drug-resistance. In conclusion, it may not be always true that Tc-99m-MIBI scintigraphy is a good assessment for MDR-modulators.

Comparison between two different methods of determining the radiochemical purity of 99m-dextrans

A. Delgado, R. Arenas, A. Ramirez, M.A. Muros, M.J. Acosta, G. Sabatel, S. Ortega, C. Ramos, J.M. Llamas. Department of Nuclear Medicine, Granada, Spain.

PURPOSE: Comparing two different chromatographic methods to quantify the radiochemi-cal purity of dextrans labelled with 99mTc.

MATERIAL AND METHODS: 27 vials with dextrans of different molecular weights were prepared, at different pH conditions and concentrations of stannous chloride (Cl2Sn.2H2O). Subsequently, labelling was carried out by adding 100 mCi of 99mTcO4- in a volume of 2-3 ml of 0.9% ClNa solution per vial.

After 15 minutes of incubation at room temperature, radiochemical purity was tested by performing two different chromatographic methods.

For the first method, ITLC-SG was employed as stationary phase and NH4:Et0H:H20 (1:2:5 v/v) as mobile phase to separate colloids, and Whatmman 17 paper and acetone as mobile phase to obtain free 99mTcO4-, as described in the bibliography

The chromatographic control we propose uses ITLC-SG and 0.1 N HCl as stationary and mobile phase, respectively, to separate colloids, and Whatmman 17 paper and acetone to obtain free perthecnectate.

The radiochromatograph scanner used was a Mini-Gita, Isotopenmeßgeräte GmbH. RESULTS:

Mobile phase: HCl 0,1 N

Mobile phase: NH4OH:EtOH:H?O

Dextrans: 200-300 Dextrans: 200-300

pH=6 96,4±0,20 0,75mg 95,5±0,65 pH=6 91,1±1,79 0,75mg 87,6±1,45

pH=7 95,7±0,22 1mg 96,3±0,36 pH=7 86,3±0,70 1mg 91,1±4,75

pH=8 95,8±0,88 2mg 96,1 ±0,50 pH=8 91,8±4,59 2mg 90,6±3,31

Dextrans: 70 Dextrans: 70

pH=6 93,9±0,93 0,75mg 93,3±1,20 pH=6 90,2±1,68 0,75mg 89,6±2,26

pH=7 92,7±0,64 1m 95,0±1,12 pH=7 88,1±1,54 1mg 91,9±2,94

pH=8 94,7±1,39 2mg 93,1 ±0,60 pH=8 95,0±1,55 2mg 91,7±3,97

Dextrans: 60-90 Dextrans: 60-90

pH=6 95,5±1,62 0,75mg 94,9±1,17 pH=6 85,0±2,65 0,75mg 83,3±3,11

pH=7 95,4±0,73 1mg 96,6±0,56 pH=7 82,1±5,13 1mg 83,2±4,28

pH=8 95,3±1,23 2mg 94,6±0,87 pH=8 85,9±2,39 2mg 86,4±3,61

CONCLUSIONS: Chromatograms obtained using the proposed method (ITLC-SG as stationary phase and 0.1 N HCl as mobile phase to separate colloids, and Whatmman 17 paper and acetone as mobile phase to obtain free perthcnectate), show a better separation of dextrans labelled with 99mTc and colloids; therefore, the percentages of radiochemical purity are more

elevated than in the standarized method, and a better concordance exists between labelling efficiency and calculated values.

(*) This communication is part of the Researching Proyect n° 98/189, supported by the Andalusian Health Service.

Radiolabeling of monoclonal antibodies with Y-86 to obtain quantitative biokinetic data and Y-90 and Ac-225 for new therapeutic approaches

D. Rattat, B. Mahren, B. Neumaier, C. Bausch, I. Buchmann, C. Solbach, M. Schmid, S.N. Reske. Department of Nuclear Medicine of the University Hospital Ulm, Germany

Aim: The optimisation of radioimmunotherapy requires the quantitative measurement of in vivo uptake kinetics which is not possible with ideal therapeutic radionuclides. Some radionu-clides (e.g. Sm-153 and Re-188 with a low energy y-radiation) deliver only a rough estimation of organ exposure due to low image quality. With PET nuclides a quantitation of in vivo dosimetry can be obtained. Y-86 as PET analogon of Y-90 allows to measure quantitatively the uptake kinetics of Y-90 labeled antibodies. Another promising therapuetic radionuclide is the a-emitter Ac-225 due to its high linear energy transfer radiation with high relative biological effectiveness. For a radiolabeling with those isotopes different monoclonal antibodies have been derivatized with the bifunctional chelating agents p-SCN-benzyl-mx-DTPA and p-SCN-benzyl-DOTA. The functionalized antibodies were labeled with the radiometals Y-86 for PET-imaging and Y-90 and Ac-225 for future therapeutic approaches.

Materials and Methods: Anti-CD20, anti-CD33 and anti-CD66 have been conjugated to p-SCN-benzyl-mx-DTPA and p-SCN-benzyl-DOTA via a thiourea bond formation between the reactive SCN-group of the respective chelator and a primary aminofunction of the antibody (in HEPES-buffer; pH= 7,9). After several purification steps (using ultrafiltration and size exclusion chromatography) and buffer exchange (citrate/acetate; pH= 5,5) the labeling was performed with up to 800 MBq Y-86, 5800 MBq Y-90 and 20 MBq Ac-225. Radiolysis and decomplexation of the antibody was determined using SEC-HPLC-chromatography. Results: With mx-DTPA-modified antibodies radiolabeling yields of 95(± 4)% were obtained for each of the three radionuclides within 45 mins (analysed by SEC-HPLC), while the DOTA-derivative reacted much slower (labeling yield only 35(±5)% after 45 min). The labeling efficiency for DOTA was depended on temperature and could be increased to 80(±5)% using elevated reaction temperatures of 30-35°C and an extended reaction time of 3 hrs. Comparison of the stability of the radioimmunoconjugates showed no significant difference for the Y-86 respectively Y-90 labeled immunoconjugate. For the a-emitting Ac-225 labeled antibody the DOTA conjugate was more stable than the DTPA derivative. For the DTPA-derivative 10-13% and for the DOTA-derivative 27-30% of intact antibody were found after 72 hrs.

Additionally for the Y86-DTPA-anti-CD20 PET-images from patients were recorded showing the biodistribution of the labeled antibody.

Conclusion: Y-86-labeled antibodies and PET deliver a more precise prediction of the in vivo biodistribution of Y-90-radioimmunoconjugates used in radiotherapy than radioimmunoconju-gates labeled with the non homologous In-111. Furthermore the availability of Ac-225 labeled antibodies due to their nucelar properties opens new perspectives in radiotherapy in view of different tumor-entities.

VirRAD - The virtual Radiopharmacy - a virtual learning community in Radiopharmacy

J.K. Sosabowski. on behalf of the VirRAD consortium. London and Lancaster, UK; Graz, Austria; Patras, Greece; Leuven, Belgium; Lisbon, Portugal; Purdue, USA and Edmonton, Canada.

VirRAD is a new research project funded by the Information Society Technologies programme of the Fifth RTD Framework Programme of the European Union. The aim of VirRAD is to develop an Internet-based virtual learning environment for Radiopharmacy which will facilitate learning and understanding in the speciality at all levels both within and outside the radiopharmaceutical community. The final structure of VirRAD is yet to be decided and will be determined by the needs and desires of its ultimate participants, however it is expected to include multimedia teaching modules for distance learning applications, 3-D simulations of specialised equipment and complex techniques used in radiopharmaceutical preparation and research as well as improved systems of peer-to-peer and student-to-tutor communication and information retrieval. To be as useful and effective as possible VirRAD needs ideas and suggestions from the Nuclear Medicine community. A mechanism for obtaining such input and feedback will be an integral part of the development process.

Preparation of 166Ho-Macroaggregates and 166Ho-Chitosan for the Radiotherapy

M. Kropacek, F. Melichar, M. Mirzajevova. Department of Radiopharmaceuticals of the Nuclear Physics Institute Academy of Sciences, Rez, Czech Republic.

Aim: The purpose of this study was focused on the preparation Holmium-166 based agents for the radionuclide synovectomy (166Ho-macroaggregates) and for the hepatic cancer therapy (166Ho-chitosan complex). Radionuclide synovectomy (radiation synovectomy) is an alternative method, that cures patients with rheumatoid arthritis diseases without surgery. During treatment, the suspension of the radioactive particles is administrated via intra-articular injection into the target joint to destroy inflamed synovium. In case of hepatic tumour therapy treatment, 166Ho-chitosan complex can be administrated either directly into the tumour, or via catheter into hepatic artery.

Materials and Methods: Isotope 166Ho (E beta max = 1.84 MeV, half life = 26,8 hr) was prepared by the 165Ho(n, gamma)166Ho reaction at the neutron flux approximately 1014 cm-2s-1. The Ho-macroaggregates (Ho-MA) were prepared by reacting the aqueous solution of Ho(NO3)3 with sodium borohydride solution in 0.2 M NaOH. The particle size distribution of the prepared Ho-MA was determined by the Laser Particle Size Analyser. Quality of the prepared Ho-MA particles was investigated by the electron microscope. The in-vitro stability studies were carried out by incubation 166Ho-MAin 6 ml 0.9 % NaCl solution. The in-vivo stability studies of the 166Ho-B-MA were done at 24 hours after administration of 166Ho-MA into the knee joint of the rat (Wistar, 190-200g).

The 166Ho-chitosan complex was prepared by reacting of Ho(NO3)3.5H2O with chitosan, which M.W. was from 150000 to 600000. The time dependence of 166Ho-Chitosan viscosity was measured using Rheometer RC20-CPS (Rheotec). Radiochemical purity of 166Ho-Chitosan complex was measured by radio TLC method.

Results: Studies carried out with 166Ho-MA showed very good in-vitro stability prepared particles. The radioactivity leakage percentage was less then 5 % within approximately 190 hours of incubation. In-vivo studies showed very high retention of 166Ho-MA in the target joint. The percentage of the activity retained in the knee joint was higher then 99.9 % at 24 hours after administration (table 1).

Table 1: 166Ho-MA In-Vivo Study on the Rats 24 hours after administration

Organ [%]_Activity_

Blood_0.007_

Lung_0.010_

Spleen_0.004_

Kidney_0.007_

Liver_0.046_

Knee Joint 99.926

Studies carried out with 166Ho-chitosan complex proved relatively high radiochemical purity (more than 90%) within sufficient time period. However, 166Ho-chitosan complex appears to be sensitive to the radiation degradation, heading for decreasing of the complex viscosity.

Conclusion:166Ho-Macroaggregates can be prospective agent for radionuclide synovectomy with respect to it's high in-vitro and in vivo stability. However, some disadvantages can be caused due to it's non-biodegradability.

166Ho-chitosan complex is promising agent for the radiotherapy considering it's biocompatibil-ity and biodegradability. It's quality though decreases with time and 166Ho-chitosan usage immediately after synthesis will be probably highly required.

Hepatocyte-targeting of In-111 labeled oligo-DNA with avidin or avidin-dendrimer complex.

M. Mamede (1), T. Saga (1), T. Ishimori (1), T. Higashi (1), H. Kobayashi (1), J. Konishi (1), M.W. Brechbiel (2). (1) Department of Nuclear Medicine and Diagnostic Imaging, Kyoto University Hospital, (2) National Cancer Institute, National Institutes of Health, Kyoto, Japan and Bethesda, USA.

Objective: To develop an effective non-viral carrier of oligo-DNA to hepatocytes, various DNA-carrier complexes were synthesized and their binding/internalization and biodistribution in normal mice were studied.

Methods: An antisense oligonucleotide (20-mer) for the primer of c-erb-2 protooncogene (DNA) or its biotinylated compound (DNA-bt) were labeled with In-111 using a DTPA chelate (1B4M). 111In-DNA-bt was further mixed with Avidin (Av) to form 111In-DNA-bt-Av. Generation 4 (G4) starburst dendrimer, which can form stable electrostatic complex with DNA, was biotinylated (G4-bt) and was mixed with 111In-DNA to form 111In-DNA/G4-bt, and then mixed with Av to make 111In-DNA/G4-bt-Av. Biodistribution of 111In-DNA-bt-Av and 111In-DNA/G4-bt-Av were determined at 15 and 60 minutes after intravenous injection into normal Balb/c mice (n=5 for each group). To verify the internalization of the compound into hepatocytes, the fluorescent conjugated compound (FITC-DNA-bt-Av) was incubated with isolated hepatocytes in vitro and the localization of fluorescence was examined with fluorescent microscope.

Results: DNA and G4 made stable complexes with the mixing molar ratio between 1:25 to 1:100. In contrast to 111In-DNA, which showed low uptake in normal organs other than kidney (17.18 %ID/g at 15 min, 14.26 %ID/g at 60 min), 111In-DNA-bt-Av showed very high accumulation in the liver (40.76 % at 15 min, 38.31 % at 60 min) with low uptake in other normal organs resulting in high liver-to-background uptake ratios. 111In-DNA/G4-bt-Av (1:100 mixing ratio) showed lower hepatic uptake than 111In-bt-Av did (21.04 % at 15 min, 23.24 % at 60 min), and showed extremely high uptake in the lung (103.03 % at 15 min, 73.00 % at 60 min), in addition to kidney and spleen, probably because of the formation of large molecular weight complex and aggregates which are trapped in the lung and reticuloendothelial system. The FITC-DNA-bt-Av showed rapid fluorescence localization in the nucleus of hepatocytes (at 15 min).

Conclusions: 111In-DNA-bt-Av showed high uptake in the liver with high liver-to-background ratios. However, 111In-DNA/G4-bt-Av revealed extremely high accumulation in the lungs that might be explained by the large molecular size of the complex, and was not appropriate for intravenous administration. Avidin seems to have the potential as a carrier of oligo-DNA to the liver.

Metabolism of I-123 ADAM in humans measured in plasma by TLC

T.S. Kyllönen (1), E-L. Kämäräinen (1), A.K. Ahonen (2), T.A. Kauppinen (2), P. Heikman (3), J. Launes (3), P. Nikkinen (2), J. Hiltunen (4), K.A. Bergström (4). (1) Laboratory of Radiochemistry of the University of Helsinki, Helsinki, Finland, (2) Division of Nuclear Medicine of the Helsinki University Central Hospital, Helsinki, Finland, (3) Department of Neurology of the Helsinki University Central Hospital, Helsinki, Finland, (4) MAP Medical Technologies Oy, Helsinki, Finland.

AIMS: Serotonin transporters (SERT) are important in imaging serotonergic neurotransmission. A novel SERT ligand, I-123 labelled 2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine (ADAM) was investigated by SPECT in humans. The aim of the present study was to determine the metabolism of [I-123]ADAM in plasma using a TLC method. METHODS: Six healthy volunteers underwent SPECT imaging with a dose of 150-200 MBq of [I-123]ADAM. Venous blood samples were collected in certain time intervals 3-300 min after injection and 1 ml of plasma was separated. A control sample was prepared adding [I-123]ADAM into non-radioactive plasma sample. 100 pg of cold ADAM was added to the control and samples as a carrier. [I-123]ADAM was extracted with ethyl acetate (3 x 0,7 ml) and the samples were sentrifuged to improve the separation of two layers. Radioactivity of the both phases was measured. The ethyl acetate extracts were dried under a stream of nitrogen and MeOH was added to the dried residues. The dissolved extracts were applicated on a silica gel TLC-plate. TLC was developed using MeOH/H2O (80:20) as an eluent. The dried TLC-plate was cut into 6 equal pieces and measured in a gamma counter. Rf-value of [I-123]ADAM was 0.5 - 0.7.

RESULTS: The extraction yield of [I-123]ADAM in the control sample was 71 ± 24 %. Extraction of unchanged [I-123]ADAM together with a minor amount of lipophilic metabolite into ethyl acetate phase in patient samples decreased to about 6 % during two hours after injection. The calculated percentage of unchanged [I-123]ADAM in plasma after 10, 60 and 120 minutes was 42.5 ± 18.1 % ; 10.7 ± 2.9 % and 8.2 ± 2.2 %, respectively. At 3 min after injection the corresponding value was about 65 %. Development in extraction method is needed to minimise broad variation in extraction yields.

CONCLUSIONS: These preliminary results indicate that in humans [I-123]ADAM transforms rapidly during 2 hours after injection into polar metabolite(s). Lipophilic metabolite with a more polar nature than [I-123]ADAM was detected using TLC only to a minor extent.

Modified TFO can be labeled with In-111, Y-90 or Tc-99m retaining their binding activity

H. Ribbert, D. Rattat, C. Shen, A. Buck, B. Neumaier, S. Meier, S.N. Reske. Department of Nuclear Medicine of the University Hospital Ulm, Ulm, Germany.

Aim: Radiolabled triplex forming oligonucleotides (TFO) might be useful therapeutic and diagnostic tools. Arapid method for labeling TFO with In-111, Y-90 and Tc-99m is described. Material and Methods: All experiments were done with the TFO BGAT20P0, which binds to a sequence in the human bcl-2 promotor region and can inhibit protein expression in vitro. This TFO contains an aminolink at the 5'end and is phosphorthioated at both ends. TFO were conjugated with mx-DTPA by resolving a TFO precipitate in saturated mx-DTPA solution. After 16 hrs the TFO was purified with G50 spin columns. To label the modified TFO with In-111 or Y-90 it was incubated for one hour in citrate/acetate buffer (1:1) at room temperature. The labeling with Tc-99m was performed using the [Tc(CO)3]+-moiety (3 hrs, 50°C, phosphate buffer, under nitrogen atmosphere). A second possibility to conjugate the Tc-car-bonyl-complex is a 3'-histidine-modification at the described TFO. After buffer exchange electrophoretic mobility shift assays were performed, to determine the binding affinity of the labeled TFO.

Results: The percentage of TFO coupled with mx-DTPA was 78±26%. This modified TFO could chelate In-111, Y-90 and [Tc(CO)3]+ even in low concentrations. Eletrophoretic mobility shift assays showed, that the labeled TFO did not significantly loose binding affinity to supercoiled plasmids containing the bcl-2 promotor region.

Conclusion: TFO's labeled by the methods described above can bring radioactivity in close contact to DNA encoding for oncogenes, as it is shown for bcl-2 here. Apart of detemining the biodistribution of those TFO's this might have additional biological effects in gene inactiva-tion.

Radiochemical studies and biologic behaviour of 188Re-DTPA for prevention of coronary artery restenosis

B.L. Faintuch (1), J.A. Osso Jr. (1), S. Faintuch (2), E. Muramoto (1). (1) Radiopharmacy Center of the Institute of Energetic and Nuclear Research, (2) Department of Radiology, Medical School of Sâo Paulo Federal University, Sâo Paulo, Brazil.

Introduction: Sodium Perrhenate-188 (Na188ReO4) has application in control of the hyperplastic component of coronary restenosis. Studies demonstrated the inhibition of restenosis (510%) with the Re-188 liquid filled balloon approach after coronary overstretch injury, vs. 3050% during angioplasty without radiation. Re-188 is an attractive radionuclide because it is available from the 188W/188Re generator system by saline elution as 188Re-sodium perrhenate solution. Radiation exposure after accidental balloon rupture can be limited by chelation with DTPA (diethylenetriaminopentaacetic acid). Aim: In this study we optimized the labeling of DTPA with 188Re to achieve the best parameters of yield and stability of the complex, and compared the biodistribution of Re-188 perrhenate and 188Re-DTPA to assess the radiation dose to organs in animals.

Methods: Labeling of DTPAwith 188Re was done varying mass (10,20,30 mg) and using different quantities of stannous chloride as reducing agent (4,5,6,7,7.5 mg). The complex obtained with the highest radiochemical purity was used for the biodistribution studies in normal swiss mice at different times (15',30', 1,2,4 hours) employing biodistribution of Na188ReO4 for comparison. Radiochemical studies of 188Re-DTPAwas done for 24 hours. Results: Best labeling was achieved using the largest mass DTPA (30 mg) and 4mg of SnCl2.2H2O in 0.1M HCl. Reaction time was 15 min at water bath of 100 °C. Radiochemical purity was 96.71% ± 2.3 assessed by ITLC. The complex was radiochemically stable for 24 h when ascorbic acid was used in the mixture. In its absence, a high reoxidaton to 188Re-perrhen-ate was observed. Greatest uptake of 188Re-DTPA was by the kidneys (19.3% ID/g) and for 188Re-perrhenate it was by the stomach (21.3% ID/g) 15 min post-injection. Uptake of 188Re-perrhenate by the stomach increased at 4h post-injection.

Conclusion: A kit of fTeeze-dried DTPA can be developed for labeling with 188Re, by means of an easy and rapid method. Protection for main organ is assured with this molecule in care of ballon damage during angioplasty, by virtue of rapid excretion via the urinary system.

Standardization of MDP labeling with Rhenium-188 for palliative therapy of bone metastases

B.L. Faintuch (1), J.A. Osso Jr. (1), S. Faintuch (2), E. Muramoto (1), E.B. Aldegheri (1). (1) Radiopharmacy Center of Institute of Energetic and Nuclear Research, (2) Department of Radiology, Medical School of Sao Paulo Federal University, Sao Paulo, Brazil.

Introduction: Since its introduction in 1975, methylene diphosphonate (MDP) has become the most common agent for imaging the skeleton when labeled with 99mTc. Rhenium-188 (188Re) is a good candidate for radiotherapy. Beside the emission of beta radiation, 188Re is a gamma emitter that allows acquisition of images.

Aim: The aim of this study was to determine optimal preparation conditions for a kit of MDP labeled with 188Re. Different concentrations of MDP, stannous chloride, other labeling conditions, and subsequent radiochemical stability and biodistribution in animals were evaluated. Methods: The mixtures were incubated in boiling water for 15 minutes. Radiochemical purity and stability were checked by ITLC. The complex with the best radiochemical yield was evaluated in swiss mice at different times. Bone/muscle uptake ratio was determine from the %ID/g values of those tissues.

Results: Optimal conditions for the kit were obtained with 30 mg of DTPA, 4 mg of SnCl2.2H2O and pH 3, and radiochemical yield reached 95.2 ± 1.8%. With smaller concentrations of MDP the labeling was not so successful. Until 4 hours the complex was stable but for 24 hour use it was necessary to add ascorbic acid to the mixture. 188Re-MDP showed a high uptake by kidneys (6.84 ± 1.5 %ID/g) , 4h post-injection and by bone (1.18 ± 0.2 %ID/g). The bone/muscle ratio was 4.52.

Conclusion: The best labeling of MDP with 188Re was achieved using a high concentration of MDP, with good uptake by bone. The results suggest the suitability of the complex for further evaluation in animals and humans for bone pain palliation and cancer therapy.

Comparison of the syntheses of c.a. and n.c.a. [99mTc]-EDTMP and[111In]-EDTMP

M. Mitterhauser (1.2.3), W. Wadsak (1), A. Krcal (1), R. Dudczak (1), H. Viernstein (3), C. Pirich (1). (1) Univ. Klinik für Nuklearmedizin AKH Wien, (2) Anstaltsapotheke des AKH Wien, (3) Inst. für Pharmazeutische Technologie und Biopharmazie, Universität Wien, Austria.

Aim: An increased uptake of bone-seeking radiopharmaceuticals into malignant bone lesions is a prerequisite for adequate bone scanning.

Recent literature shows increased bone uptake in rat of no carrier added (n.c.a.) ['''Inj-EDTMP compared to n.c.a. [99mTcj-EDTMP. Yet carrier addition might lead to an even increased bone uptake.

Therefore, this study aims to compare the syntheses of [99mTcj- and ['''Inj-EDTMP c.a. versus n.c.a. as a basis for further investigations in man.

Materials and Methods: N.c.a. [99mTcj-EDTMP: Preparation according to the manufactorer's instructions (Multibone®). C.a. [99mTcj-EDTMP: perrhenic acid (!5^g) was added to [99m Tcj-pertechnetate (>6GBq in phys. saline), transferred to a vial containing 25mg EDTMP, 3.6mg stannous(II)chloride and 10mg ascorbic acid and heated to 45°C for 10min. N.c.a. ['''Inj-EDTMP: ' ml of an ['''In]-InCl3 solution (40MBq in phys. saline) was added to a vial containing 25mg of EDTMP, 'mg stannous(II)chloride and 10mg ascorbic acid, kept at ambient temperature for '0min. C.a. ['''Inj-EDTMP: Additionally, perrhenic acid (!5^g) was added to the respective labelling solution. Quality control ([99mTcj-EDTMP) was performed using radio-ITLC (Whatman SG; acetone: Rf perrhenate/pertechnetate 0,87, colloid/product 0.05; phys. saline: Rf colloid 0.00, perrhenate/pertechnetate and product 0.9) allowing efficient assessment of the labelling results. ['''Inj-EDTMP was analyzed using a Merck HPLC-system with UV- and NaI-detectors (Lichrospher RP '8, aquous acetic acid/acetonitrile 60/40). Results: Labelling yields were 80% (n='0; '5^g c.a.) and 9'% (n=5; n.c.a.) for [99mTcj-EDTMP. ['''Inj EDTMP showed labelling yields of > 95% (n=4) for both preparation-procedures. Radiochemical purity was >95%, any formed colloid was removed by sterile filtration (0,22^m). In clinical studies quantitative analysis of c.a. [99mTcj-EDTMP demonstrated a significant (p < 0.05) increase in bone/soft tissue ratio and bone lesion/normal bone ratio as compared to n.c.a. [99mTcj-EDTMP. Similar in vivo-experiments with c.a. versus n.c.a. ['''Inj-EDTMP are planned.

Conclusion: Our methods of labelling EDTMP with different nuclides allow fast and efficient preparations of Re/[99mTcj-EDTMP and Re/['''Inj-EDTMP.

Carrier addition decreased the labelling yield for the [99mTcj-labelled compounds but resulted in an increased bone uptake compared to n.c.a. preparations. Carrier addition had no effect on the labelling yield for ['''Inj-compounds. If this is also true for bone uptake needs clinical studies.

Possible improvements in the cyclotron production of 211At for targeted cancer therapy

U.W. Holzwarth, K. Abbas. European Commission, Joint Research Centre, Institute for Health and Consumer Protection, Ispra , Varese.

Among the a-particle emitters currently under examination for targeted tumor therapy the radioisotope 211At has promising properties due to the absence of hard y-radiation and its halflife of 7.2 hours. The main drawback of this radioisotope originates from its production route via the reaction 209Bi(a,2n)211At, which requires cyclotrons capable of accelerating a-particles to at least 28 MeV. In Europe only two cyclotrons (Rigshospitalet Copenhagen (DK), and Forschungszentrum Karlsruhe (D)) currently produce significant amounts of 211At for research. A few other cyclotron sites are in preparation phase. Sufficient availability of 211At for cancer research requires efforts to improve the production efficiency.

In order to investigate a possible advantage of a production by irradiation with 3He2+-particles instead of a-particles Monte Carlo simulations are presented for the reaction cross sections and the theoretical yield of the reactions 209Bi(a,2n)211At, 209Bi(3He2+,n)211At and for the reactions 209Bi(a,3n)210At, 209Bi(3He2+,2n)210At leading to the main radiological impurity 210At with these production routes.

The reaction cross section results of the Monte Carlo simulations for 209Bi(a,2n)211At, agree well with experimental literature data and exhibit a maximum of about 1000 mb between 28 and 30 MeV a-particle energy. The reaction cross section for irradiation of bismuth with 3He2+-particles reaches maximum values of only 30 mb leading to the exclusion of 211At-pro-duction by 3He2+-bombardment of bismuth. The theoretical production yield of the reaction 209Bi(a,2n)211At at 30 MeV a-particle energy turns out to be 100 MBq/^Ah. This value is significantly lower than earlier calculations by R.M. Lambrecht and S. Mirzadeh (Int J Appl Radiation and Isotopes 36 (1985) 443-450) but twice as high as the best experimental data reported so far. This difference between theoretical calculation and experimental findings is extraordinary large and strongly indicates to review and improve target design. The reason for this discrepancy is very likely the loss of 211At from the low-melting bismuth layer already during irradiation. Possible venues by improved coating technology and cooling of the bismuth layer will be discussed.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition ANIMAL STUDIES

Comparison of biodistribution and in vivo image between humanized anti-TAG-72 antibody and F(ab')2 fragment in tumor bearing nude mice.

S.J. Lim, T.S. Lee, K.S. Woo, W.S. Chung, S.J. Lee, K.J. Chun, C.W. Choi, S.M. Lim, S.W. Hong. department of cyclotron application laboratory of KCCH, Seoul, Korea.

Purpose: The mouse antibody repertoire, which in the form of monoclonal antibodies has been used in diagnostic applications would be an attractive source for the generation of therapeutic human antibodies. To evaluate the possibility of humanized Anti-TAG-72 monoclonal antibody(AKA) as diagnostic or therapeutic agent, biodistribution and in vivo image were obtained in LS174T(TAG-72 +) and MCF7(TAG-72 -) tumor bearing nude mice(n=4/group). Methods: We produced AKA producing cell line that CHO cell was transfected by recombinants of human IgG1 chain and binding epitope of mouse anti-TAG-72 antibody. Whole AKA and AKA F(ab')2 was labeled with 125I using chloramin-T methods. Tumor xenograft model was produced by injection of human adenocarcinoma cell line (LS174T) into left thigh and human breast adenocarcinoma cell line (MCF7) as negative control into right thigh of Balb/c nude mice. Biodistribution of 123I-whole AKA, 123I-AKA F(ab')2 was determined at 4, 24hr and in vivo images of 123I-whole AKA, 123I-AKA F(ab')2 was performed at 24hr in tumor bearing nude mice. Immunohistochemical stainings were done on frozen human colon cancer tissue samples.

Results: Radiolabeling yield of whole AKA and AKA F(ab')2 was 84.8%, 96.6%, respectively. Blood radioactivity was rapidly decreased in case of AKA F(ab')2 antibody. Tumor/Blood(T/B)ratio of whole AKA and AKA F(ab')2 was 1.67, 3.62 and T/B of AKA F(ab')2 is 2 fold higher than the whole AKA. Target tumor uptake of whole AKA and AKA F(ab')2 were 6.56, 8.84% ID/g and 5.73, 1.81% ID/g at 4, 24hr. Both 123I labeled whole AKA and AKA F(ab')2 were specific localized in LS174T tumor at 24hr image. Humanized AKA F(ab')2 reacted strongly staining with human colon cancer tissue sections was analyzed by immunohistochemistry.

Conclusion: These results suggest that AKA F(ab')2 can be useful for radioimmunodetec-tion(RID) and whole AKA for radioimmunotherapy(RIT), because AKA F(ab')2 was more rapidly cleared ,higher tumor/blood ratio than whole AKA antibody and whole AKA showed higher tumor uptake than F(ab')2. Furthermore, we need to be evaluated the efficacy of humanized antibody in RID and RIT.

Preliminary Study of 99mTc-HL91 on A Tumor Mouse Model

G.U. Hung (1), Y.C. Weng (2), W.Y. Lin (1), S.J. Wang (1), C.C. Hsia (3), S.P. Wey (3), L.H. Shen (3), G. Ting (3). (1) Department of Nuclear Medicine, Taichung Veterans General Hospital, Taichung, Taiwan, (2) Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan, (3) Institute of Nuclear Energy Research, Lung-Tan, Taiwan.

Background: Many malignant tumors are characterized by perfusion heterogeneity due to its proliferation more rapid than the vascularity, which results in tumor regions that are acutely or chronically hypoxia. 99mTc-HL91 is an amine oxime core radioligand that has shown oxygen dependent passive in vivo and in vitro binding with higher binding under hypoxic conditions than under non-hypoxic conditions. This study evaluated the domestic preparation of 99mTc-

HL91 for its feasibility as a tumor imaging agent, and compared the results with 201Tl-TlCl

(201Tl). 201

Methods: The lyophilized kits of HL91 and 201Tl-TlCl were produced by Institute of Nuclear Energy Research (INER). Following reconstitution of the kit with 99mTc-pertechnete, 99mTc-HL91 was injected intravenously into C3H mice bearing KHT sarcoma xenografts. Whole-body scans were performed at 1 h, 1.5 h and 2 h post-injection. The ratios of tumor-to-normal tissue background (T/N) were measured. After imaging study, the mice were sacrificed and underwent autoradiography. Parallel studies with 201Tl were performed for comparison. Results: There was increased uptake of 99mTc-HL91 at tumor regions. The T/N ratios of 99mTc-HL91 measured at 1 h, 1.5 h and 2 h were 2.986, 2.351 and 1.872, respectively. The images of 201Tl showed similar distribution of activity. The T/N ratios of 201Tl at 1 h, 1.5 h and 2 h were 1.457, 1.709 and 1.781, respectively.

Conclusion: The administration of 99mTc-HL91 resulted in specific localization in the tumor mass of mice bearing sarcoma xenografts, which was also identified by 201Tl. The preliminary result suggested that 99mTc-HL91 prepared by INER has the potential to be a promising radio-pharmaceutical for tumor detection.

Biokinetics of 99mTc-Labelled Antibodies in the Rat - Potential New Lymphotropic Tracers

T. Gruning, G. Wunderlich, J. Kropp. Department of Nuclear Medicine, Carl Gustav Carus Medical School, University of Dresden, Dresden, Germany.

Aim: 99mTc-labelled antibodies with a binding specificity relevant to lymph nodes were evaluated as lymphoscintigraphic agents. Well-established markers of lymph node germinal centres were chosen: CD23, CD38, CD80, and CD86. Cell surface IgD (sIgD) was used as a marker of mature B cells. CD45 can be found on all haematopoietic cells (control). Materials and Methods: Antibodies were obtained from commercial suppliers. 99mTc-labelling was performed using 2-iminothiolane as interchelating agent. Radiolabelled antibody was injected into the footpad of eight weeks old female Wistar rats, and intravenously into the tail vein of another animal. Gamma camera images were obtained from 5 minutes until 2 hours, at 24 hours p.i., and after dissection. The time-activity course in lymph nodes was determined using ROI technique. Blood samples were obtained 2 hours p.i. Animals were sacrificed and dissected 24 hours p.i. The activity of various organs was measured in a well counter. Results: The table shows (a) lymph node activity 1 and 2 hours after footpad injection expressed as percentage of the value measured at 5 mins p.i.; (b) organ distribution 24 hours after intravenous injection; (c) urinary excretion within 2 hours following intravenous injection; (d) serum activity at 2 hours p.i. (counts/l/MBq injected). Antibodies to co-stimulatory molecules CD80 and CD86 showed a maximum lymph node accumulation of about twice the initial value, as well as good retention. All other antibodies investigated showed a steady decline of activity in the lymph node. Anti-CD80 and -CD86 also had a low serum and high liver activity after intravenous injection, suggesting a high degree of cell-bound activity.

CD23 CD38 CD80 CD86 sIgD CD45

(a) 1 hour 110% 63% 260% 180% 91% 95%

2 hours 85% 48% 230% 140% 85% 67%

(b) liver 11% 15% 20% 36% 9% 19%

spleen 0% 0% 1% 2% 2% 6%

kidneys 30% 20% 28% 24% 47% 26%

lungs 1% 1% 1% 1% 1% 1%

remainder of the body 57% 63% 50% 38% 41% 48%

(c) urinary excretion 24% 27% 34% 28% 37% 47%

(d) intravenous injection 1400 2000 980 910 1400 300

footpad injection 140 210 110 84 730 100

Conclusion: When using immunoglobulins as lymphoscintigraphic agents, specific and lasting accumulation in lymph nodes depends on the binding specificities of the antibodies. Studies seeking to optimize accumulation and retention of anti-CD80/86 as well as investigating further markers may be worthwile.

Age-related changes in regional cerebral bloodflow and binding index of the 5-HT2A receptor in the canine brain

K.Y. Peremans (1), K. Audenaert (2), I. Van Soens (1), F. Jacobs (2), P. Blanckaert (3), H. van Bree (1), F. Verschooten (1), G. Slegers (3), R. Dierckx (2). (1) Department of Medical Imaging of the Faculty of Veterinary Medicine, University of Ghent, Belgium, (2) Division of Nuclear Medicine of the the Faculty of Medicine, University of Ghent, Belgium, (3) Laboratory of Radiopharmacy of the Faculty of Pharmaceutical Sciences, University of Ghent, Belgium.

Aging in men and animals is accompanied by alterations in brain perfusion, metabolism and neurotransmitter systems, resulting in a decline of cognitive, affective and behavioural functioning.

The aim of this study was to investigate regional brain perfusion and binding index of 123I-5-I-R91150, a selective ligand for 5-HT2A receptor imaging, in aged dogs, and to compare the obtained data with a reference group.

MATERIALS AND METHODS: Agroup of reference dogs (N=12, 6 M, 6 F) aged between 12 and 48 months (mean: 49 months, SD: 29) was compared with a group of aged dogs (N=12, 5 M, 7 F; range: 96-144 months, mean: 119 months, SD: 18).

Regional brain perfusion was visualised with 99mTc-ECD. The binding index of the 5-HT2A receptor was measured using the selective ligand 123I-5-I-R91150. Both examinations were performed under general anesthesia, with a high resolution fan-beam collimated triple head gamma camera with an interval of at least 1 week. A 153Gadolinium transmission scan was acquired. Images were reconstructed with FBP and a Butterworth-filter (cut-off 0.16 cycli/pixel, order 8). Uniform attenuation and a triple-energy window scatter correction were applied. Images were analysed with VOI's drawn around fronto-, temporo, parieto-, occipito-cerebral, thalamic regions and the cerebellum. Regional cerebral counts were normalised to the activity registered in the cerebellum.

RESULTS: Perfusion data: a significant decrease in perfusion was found in the left (LF: P<0.01; LT: P= 0.01) and right (RF: P= 0.02: RT: P= 0.001) fronto-temporal cortical and subcortical regions (P= 0.001) in the group of aged dogs compared to the reference group. Binding index of l12I-5-I-R9115&. a significant decrease in binding index was found in the left (P< 0.001) and right (P= 0.001) fTonto-cortical area in the aged group.

No significant correlation was found between the regional binding index of 123I-5-I R91150 and brain perfusion.

CONCLUSION: These findings suggest that SPET examination provides valuable information concerning the physiopathology of the aging canine brain and can aid in the evaluation of therapeutic support.

Handling of Tc-99m-HYNIC-TOC and Tc-99m-Lanreotide in the Perfused Rat Kidney

F. Trejtnar (1), A. Laznickova (1), M. Laznicek (1), H.R. Maecke (2), C. Decristoforo (3), K. Eisenwiener (2), J.C. Reubi (4), S. Wenger (4), S.J. Mather (3). (1) Faculty of Pharmacy, Charles University, Hradec Kralove, Czech Republic, (2) University Hospital, Basel, Switzerland, (3) St. Bartholomew's Hospital, London, UK, (4) Institute of Pathology, University of Bern, Switzerland.

Aim: Radiolabeled derivatives of octreotide have been shown to be useful for visualization and potential therapy of several types of human endocrine tumors. Significant renal uptake of the octreotide analogs reduces the sensitivity of scintigraphy for detection of small tumors in the perirenal region. Thus, detailed knowledge of renal handling could contribute to a formulation of more optimal compounds. The aim of the study was to analyze excretion parameters, mechanisms of excretion, and retention of two somatostatin receptor-targeted peptides, 99mTc-hydrazinonicotinyl-Tyr3-octreotide (HYNIC-TOC) and 99mTc-lanreotide (LAN) in the kidney in vitro.

Materials and Methods: Renal excretion parameters of the peptides were studied using the methods of the perfused rat kidney. The isolated rat kidney was perfused with Krebs-Henseleit solution containing bovine albumin, washed rat erythrocytes (6 %) and a mixture of amino acids under constant pressure in a recirculation regimen. Renal retention was evaluated using ratio of radioactivity of the perfused kidney and the perfusate. Bindings of the peptides to the perfusate were determined by equilibrium dialysis.

Results: Renal clearance values of two 99mTc-peptides under study were very different. While LAN clearance in the perfused kidney was extremely low, HYNIC-TOC renal clearance was by more than one order of magnitude higher. Similarly, binding to proteins in the perfusate was substantially different. The bound fraction of more lipophilic LAN was much higher than that of HYNIC-TOC. Correction of the renal clearances for binding to proteins in the perfusion medium revealed that the filtrated amount of each peptide was equal to the in urine excreted amount for both peptides. It means that both compounds are excreted in the kidney exclusively by glomerular filtration. Ratio of radioactivity in the kidney and the perfusate at the end of the perfusion was significantly higher in case of HYNIC-TOC. Conclusion: Somatostatin receptor-specific radiolabeled peptides HYNIC-TOC and LAN exerted very different efficacy of renal elimination. However, mechanisms of renal excretion are in both compounds similar because they were excreted in the perfused rat kidney by glomerular filtration. The found differences in renal excretion and retention can be attributed to differences in lipophilicity of the octreotide derivatives.

(The work was created under the support of program COST B12 of EU and was partly supported by the Grant Agency of Charles University, grant No. 264/2001)

Technetium-99m Human Immunoglobulin Scintigraphy in the Detection of Active Inflammation in Patients with Ankylosing Spondylitis: A Correlative Study with Bone Scintigraphy

O. Ozdogan (1), B. Degirmenci (1), E. Akalin (2), O. Senocak (2), S. Gulbahar (2), C. Tasci (1), G. Arslan (1), H. Durak (1). (1) Dokuz Eylul University School of Medicine Department of Nuclear Medicine, (2) Dokuz Eylul University School of Medicine Department of Physical Therapy and Rehabilitation, Izmir, Turkey.

Ankylosing Spondylitis (AS) is a systemic rheumatologic disease with unknown etiology and characterized by the inflammation of axial skeletal system and peripheral joints. The diagnosis of active inflammation and treatment in AS patients are very important in order to delay possible persistent deformities. Because of the absence of specific laboratory and imaging methods clinicians experience problems in the diagnoses of active inflammation. Aim: To detect active inflammation with Tc-99m human immunoglobulin (HIG) scintigraphy. Methods: 29 AS patients diagnosed according to New York criteria were included in this study. Tc-99m methylenediphosphonate (MDP) bone and HIG scintigraphies were performed within 2-5 day intervals. Two control groups were constituted for both MDP and HIG scinti-graphies, with patients without any known rheumatologic diseases and pelvis patologies. In AS patients active inflammation was determined clinically and by serologic tests. Both scinti-graphies were evaluated visually and quantitatively. Sacroiliac joint index (SII) values were calculated by drawing region of interests to sacroiliac joints and adjacent sacrum at the fourth hour posterior static image of patients and controls. Results: Active inflammation was considered in 5 patients (sacroileitis in 2, achilles tendinitis in 1, sacroileitis and spinal inflammation in 1, arthritis of coxafemoral joints in 1) by clinical evaluation. HIG scintigraphy showed increased uptake in 6 patients. HIG accumulation was seen in all patients with clinically active sacroileitis. The other 3 cases with HIG accumulation were in clinically inactive patients (1 in right knee joint, 1 in thoracic spine and the last in sacroiliac joints). Right and left SII obtained from bone scintigraphy was statistically higher (p<0.05) in patient group than in control group. Right and left SII obtained from HIG scintigraphy was statistically higher (p<0.05) in patients with scintigraphic active sacroiliac joints than in control group. There was no correlation of patients' exercise program, medical treatment, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values with the sacroiliac indices obtained from MDP and HIG scintigraphies.

Conclusion: HIG scintigraphy seems be a useful method for determining the active sacroileitis and may help to diagnose peripheral joint inflammation. HIG scintigraphy therefore may be used as a complementary method for clinical assessment.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition CORRELATIVE IMAGING

18FDG-PET in the diagnosis and follow-up of patients with Takayasu's arteritis. Comarisons with Angiography

A. AL-Nahhas (1), J. Andrews (2), L. Rahman (1), J. McVey (1), J. Frank (1), M. Myers (1), J.C. Mason (2), D.O. Haskard (2). (1) Department of Nuclear Medicine, Hammersmith Hospital, London UK, (2) Department of Rheumatology, Hammersmith Hospital, London, UK.

Aim: Takayasu's arteritis (TA) is a rare disease in which early diagnosis and assessment of treatment efficacy remains problematic. Clinical assessment is difficult as signs, symptoms and conventional blood tests are mostly non-specific. The current imaging gold standard is angiography, which is invasive and becomes positive only later in the disease coinciding with structural vascular damage. Recently, non-invasive methods have shown promise in the assessment of TA and we report our experience with positron emission tomography using 18FDG.

Methods: We reviewed invasive and non-invasive imaging performed on 5 patients who fulfilled the ACR criteria for TA. In addition to angiography all patients had 18FDG-PET performed at baseline. Following treatment, 3/5 had repeat 18FDG-PET to assess thertapeutic response by visual analysis and / or standard uptake value (SUV) quantitation. Results: At presentation 18FDG-PET was abnormal in 4/5 patients, all of whom showing occluded or stenotic vessles on angiography, and normal in 1/5 patient who had no angio-graphic data. Following treatment, 3 patients with abnormal baseline had repeat 18FDG-PET, one of which showed persistence of abnormal appearance in line with further occlusion on angiography, persistent acute phase response and poor clinical condition complicated by further vascular events. The other two patients showed normal or no change in 18FDG uptake coinciding with improvement in clinical status and normalised acute phase response. Angiography was not repeated when non-invasive imaging was normal or showed no progression.

Conclusion: All studies combining 18FDG-PET with angiography were concordant (7 studies in 5 patients). 18FDG-PET provided valuable information at diagnosis and after therapy and may play a role in the management of other vasculitides.

The Clinical Impact of a New Automated Software Registration for the Evaluation of Tomographic Images of the Head and Neck and Torso

R. Hardoff (1), A.P. Steinmetz (1), Z. Bar-Sever (1), C. Studholme (2). (1) Department of Nuclear Medicine, Beilinson Campus, Rabin Medical Center, Petah-Tikva, Israel, (2) Department of Radiology, University of California, San Francisco, USA.

Objectives: Co-registration of tomographic images improves localization of lesions and helps in comparisons of studies. Dedicated combined imaging devices have attached x-ray tubes or a full CT on gamma cameras or PET machines. This hardware equipment is expensive and is not available from all vendors. Software registration (SR) is a non-expensive tool, which can be used with any equipment and be utilized for single photon, positron, CT and MRI images. SR has been utilized mainly for brain studies. We present a new SR method, which is useful for head and neck and torso imaging and report our initial experience with SR of nuclear medicine (NM) images.

Methods: SR was performed in pts in whom lesion localization was uncertain. Studies were first read without and then with SR, both by consensus. The clinical impact of SR was judged by improvement of lesion localization and by change in pt management (up or down-staging, initiating new treatment, surgery etc).

Results: 25 evaluations were performed in 22 pts. A total of 42 NM,15 CT and 2 MRI studies were performed. NM studies were compared with each other in 17 instances, with CT/MRI in 11, with both in 13 instances. SR of the head and neck and torso proved to be technically adequate with good alignment between different image sets. SR was helpful in improving lesion localization in 22 of 25 evaluations (88%), and changed management in 14 (64%). Conclusions: SR can be an important tool in lesion localization and pts management. It is feasible to perform SR of the head and neck and the torso.

Investigation of the thoracic duct by 123-I IPPA Scintigraphy and SPECT/CT image fusion using the BodyFix® positioning device

D. Heute (1), E. Donnemiller (1), R. Bale (2), J. Hoflehner (2), M. Rieger (2), H. Zoller (3), T. Trieb (1), B. Warwitz (1), R. Moncayo (1). (1) Department of Nuclear Medicine, (2) Department of Radiology, (3) Department of Internal Medicine - University of Innsbruck, Austria.

Patient: A 30 year old man was referred to our hospital with recurring pleural effusion. Initially a chylo-pericard without severe clinical symptoms was diagnosed incidentally. Three years later our patient developed rapidly increasing dyspnoe over two months. Pleural effusion had to be punctured several times (4 times on the left and once on the right side) gaining 1,5 to 2 l of chylous fluid each time.

Objective: Discovering of thoracic duct pathologies by lymphoscintigraphy with 123-I fatty acid correlated with thorax CT using the image fusion technique.

Method: After oral administration of 220 MBq of 123-I labelled fatty acid (IPPA) diluted with 200 ml water planar images were taken at 10, 30, 45, 110, 155 and 280 min. SPECT of chest was done after 2 h using a double head gamma camera (ADAC Vertex). 3 mm helical contrast-enhanced CT scans were obtained with the GE HiSpeed CT/i Advantage. Preparation for image fusion was done with the BodyFix System ® which allows an exact and repetitive repositioning of the patient in each study modality. The system uses 7 markers on a vacuum immobilisation system and the patients skin in precisely defined positions. Results: On the images up to 45 min post application the tracer can be seen in the GI tract. From 110 min upward the planar images showed transport of the activity into the thorax with hot spots in the anterior parts of upper mediastinum and lower neck. Additional activity was seen in the region of the left lung and the right hilus. This tracer distribution remained constant until the end of the study. Suspicious corresponding lesions seen on CT could thus be verified as lymphatic cysts by fusion of SPECT with CT images. These findings were confirmed by an additional CT-lymphography using lipiodol ultra fluid

Conclusion: Scintigraphy with 123-I fatty acid combined with CT using image fusion technique seems to be a promising and reliable approach for functional imaging of the thoracic lymphatic system. The method is feasible for the localisation of cysts as well as leakage of the thoracic duct and visualisation of depots of lymphatic effusion into the thorax.

Combined emission-transmission tomoghaphy in evaluation of patients with low-back and joints pain.

L. Picchi. Department of Nuclear Medicine Santa

I. Taddei, P. Cavalleri, Chiara Firenze Italy.

Scintigraphic evaluation of patients with orthopedic diseases is useful in differentiating active pathology from that which has no actual clinical impact. It is very important to accurately localize the anatomical area of bone remodelling to assess a clinical diagnosis. The introduction of T.E.T. technology which combines sequential acquisition of anatomical and functional images using the same imaging device,allows a highy accurate fusion of both types of image. Method: We studied 22 patients using T.E.T. technology that was sent for investigation of low back pain or pain to joints.The emission part of the study was performed three hours after injection of 99mTc-MDP 740 MBq e.v.The purpose of T.E.T. protocol was to evaluate the additional benefit gained in clinical interpretation of the emission images. Patient population: T.E.T technology was applied on 5 patients with low back pain, 11 patients with knee pain (5 with prosthetic implants) , 5 with hip pain (3 with prosthetic implants) and 1 with shoulder pain.

Results: All patients had scinthigraphic studies,which rendered with abnormal findings, and some had morphologic abnormalities that could also be detected on the low resolution transmission tomography which was used for anatomical mapping.In detail we considered these anatomical abnormalities. lateralization of the rotula (patella) presence of endoarticular fluid degenerative modification of articular surfaces

T.E.T. made easy images interpretation in 17 of 22 patients and provides informations of additional clinical value in 13 of 22 patients.

Discussion: The Nuclear medicine approach is sensitive and delineates in an original way the functional characteristics of the bone tissue. Thus,not only does the bone scan help to identify the cause of pain,but also the correct anatomic localization of the abnormality,as provided by Xray fusion,could provide an important information that could reduce nonspecificity of this kind of procedures.

Other advantages of this technology are to distinguish referred pain from the true source of pain and to choose among many lesions that could give pain the one that is actually active.

Intra-scrotal photopenic lesions on testicular scintigraphy: correlation with color Doppler sonography

Z.V. Maizlin (2), N. Hod (1), S. Strauss (2), H. Manor (2), T. Horne (1). (1) Department of Nuclear Medicine, Assaf Harofeh Medical Center, (2) Department of Medical Imaging, Assaf Harofeh Medical Center, Zerifin, Israel.

Aim: Early detection of testicular torsion can lead to testicular salvage if treated promptly. Testicular scintigraphy is a well-known and extremely sensitive diagnostic method. The scintigraphic hallmark of testicular torsion is the appearance of intra-scrotal photopenic lesion. However, this finding can represent other intra-scrotal lesions thus lowering the specificity of the test. In this study we evaluated the relative merits of Doppler sonography in patients who were suspected of having acute testicular torsion as diagnosed on Tc-99m pertechnetate testicular scintigraphy.

Materials and Methods: Tc-99m pertechnetate testicular scintigraphy and Doppler sonogra-phy were concurrently performed at the same event within 24 hours in 75 patients with acute scrotum. In 27 patients an intra-scrotal photopenic finding indicated the possibility of testicu-lar torsion. All scintigraphic and sonographic records of the 27 patients were retrospectively analyzed.

Radionuclide perfusion and blood-pool scintigraphy were performed after 10-15 mCi Tc-99m pertechnetate injection. Doppler sonography was performed with the patient in a supine position, using high-frequency 7-10 MHz linear transducer.

Results: Ten of the 27 patients underwent surgery which revealed testicular torsion in 7, tes-ticular abscess in 1, torsion of appendix testis with reactive hydrocele in 1 and tumor in 1 patient. Of the 17 patients who were managed conservatively based on the clinical and sono-graphic features, the final diagnosis was epididymo-orchitis with reactive hydrocele in 3, atrophic but viable testis in 1, recurrent intrascrotal hernia in 1,cryptorchidisim in 2, spontaneous testicular de-torsion in 1, intra-scrotal hematoma in 1, and in 8 cases no explanation was found for the scintigraphic findings. Doppler sonography was 72% sensitive ( 5 of 7 cases ) and 100% specific for testicular torsion preventing unnecessary exploration in 17/27 ( 63% ) of the patients.

Conclusions: Tc-99m pertechnetate testicular scintigraphy and Doppler sonography play an important role in the investigation of acute scrotum. In cases in which Tc-99m pertechnetate testicular scintigraphy indicate the possibility of testicular torsion ( photopenic lesion ), Doppler sonography should be used as a morphologic imaging tool differentiating testicular torsion from other testicular or paratesticular causes for the scintigraphic findings, thereby preventing unnecessary exploration in many patients. In cases were testicular torsion is strongly suspected clinically despite negative sonography, performing scintigraphy can prevent false negative sonographic diagnosis.

Combined gamma-camera/X-ray-CT-device for anatomical mapping and attenuation correction in conventional scintigraphy and hybrid-PET- imaging: Aspects concerning clinical routine

L. Fridrich, A. Brandl, J. Gimpl, C. Müller, E. Skrinjar. Institute of Nuclear Medicine, County Hospital Steyr; Steyr, Austria.

Since our hospital was worldwide one of the first commercial installation-sites in the field for a PET-Hybrid-gamma-camera combined with a X-ray CT-scanner, this device was used in clinical routine immediatly after successful technical installation; therefore it was our Aim: To give a survey of the first clinical experiences in conventional scintigraphic and PET imaging with this device.

Material and Methods: Our departement(3 physicians, 6 technicians) supports 3 other regional hospitals (total beds: n=1650) and an outpatient area (n>200 000 inhabitants). During Y2000 beside two other cameras (Helix dual haed WB-Ect; single haed 409 AG Ect;GE) a digital dual haed gamma camera with 5/8 inch crystals and built in X-rayCT (Millenium VG + Hawkey Option +OS2 Aquisition Station;GE) TCPIP-connected to 6 eNTEGRA (NT-Work-stations;GE) and a NuclearMedicine-(dedicated)-DICOM-Pacs(Elimpex since 1997)was installed. Conventional scintigraphic imaging was performed 5 days /week 8h/day, PET imaging 3 days /week up to 6h/day. PET-Image reconstruction and evaluation was performed using different energy windows(applied patient-activity 185-370Mbq 18F-FDG). Results: Beside thyroid investigations(n=10 909 ) in 2001, the first year of more extensive use of the new combined PET-Hybrid X-Ray CT-scanner, alltogether 4923 scintigraphic procedures (^including Bone-, Inflammation-, Iodine- and Receptor-studies; **Onco- and Neuro-Pet) have been performed. Using both WB-cameras, nevertheless, the thicker cristal was preferred for higher energy-imaging.For 99mTc-studies the reading physicians could'nt recognize any difference with clinilal impact according to scintigraphic image quality. However in WB-studies they expected and experienced further clinical information from SPET and SPET combined with the Hawkey-Modality in 30 and an additional 29% respectively, althoug adding a radiation burden of 300mRem/SPET-position to the patients.

Year: 2001 Whole Body SPET* SPET + X-ray-CT* PET + X-ray-CT** _Scintigraphy*_

84(+44/ untill March 2002)

PET-studies performed earlier without attnuation correction resulted in inferior image-quality, therefore X-ray-at-tenuation-correction have become obligatory in PET-Studies despite possible pitfalls like movements- and metal-artefacts. Since availaible, reconstruction using COSEM and OSEM performed superior than the initial applied iterative method and generated sophisticated corrected and uncorrected images for image-fusion impressing even physicians without NM-knowledge.

Conclusion: Althoug a complex device, in a medium sized NM departement not dedicated to academic research, the gamma-camera-Hawkey-X-ray-CT-Modality in combination with a standardized commercial available softwere package has despite some pitfalls i.e. possible reconstruction artefacts and starting difficulties, however demonstrated its clinical practicability, gaining improved image quality and therefore enhanced functional and complementary anatomical information overt recognisable for the referring clinicians concerning hybrid-PET as well as conventional scintigraphic applications .

First 3 months pregnancy: After 3 months pregnancy:

Scintigraphic examinations during pregnancy: a survey of Belgian nuclear medicine physician's attitudes.

A. Sand (1), M. Tondeur (2), H. Ham (2). (1) Dept of Nuclear Medicine, AZ J. Portaels, Vilvoorde, Belgium, (2) Dept of Nuclear Medicine, CHU St Pierre, Brussels, Belgium.

Aim: The present survey was undertaken to approach the practices of Belgian nuclear medicine physicians towards performing diagnostic tests during pregnancy and in breast-feeding women.

Materials and Methods: Questionnaire (see infra) was sent to all (201) Belgian Nuclear Physicians.

Results: 78 answers (39 %) were received During pregnancy, do you accept to perform Tc-99m lung perfusion scan ?

Yes, using standard protocol: 16% ; Yes, using a reduced dose : 51% ; No : 33% Yes, using standard protocol : 24% ; Yes, using a reduced dose : 52% ; No : 24%

Tc-99m ventilation scan ?

First 3 months : Yes, using standard protocol : 10% ;

Yes, using a reduced dose : 11% ; No : 79% After 3 months : Yes, using standard protocol : 15% ;

Yes, using a reduced dose : 19% ; No : 66% Other diagnostic tests using Tc-99m ?

First 3 months : Yes, using standard protocol : 4% ;

Yes, using a reduced dose : 12% ; No : 84% After 3 months : Yes, using standard protocol : 4% ;

Yes, using a reduced dose : 17% ; No : 79% Other diagnostic tests using other radioisotopes ? First 3 months : Yes, using standard protocol : 3% ;

Yes, using a reduced dose : 0% ; No : 97% After 3 months : Yes, using standard protocol : 3% ;

Yes, using a reduced dose : 0% ; No : 97% In breast-feeding women do you accept to perform Tc-99m diagnostic tests ? No : 11%

Yes, using standard protocol : 0%

Yes, provided a breast-feeding break : 89%

In those situations is an informed consent necessary ? Yes : 42% ; No : 58% Conclusion: These results are quite similar to those obtained in other countries ; given the diversity of the opinions expressed, practical guidelines defining a standardized attitude would be helpful.

Date: 02.09.2002 • Time: 14:30 - 16:00 • Hall: Poster exhibition MANAGEMENT IN NUCLEAR MEDICINE

A Feasibility Study of the Installation of a PET Facility in an Italian Public General Hospital.

M.E. Dottorini (1), L.S. Maffioli (2). (1) Department of Nuclear Medicine of Ospedale Civile Legnano, Legnano, Italy, (2) Department of Nuclear Medicine of Ospedale, Legnano, Italy and Lecco, Italy.

AIM: The aim of this study was to assess if the costs of developing and operating a PET facility can be financially feasible for two General Hospitals, located in Lombardy, a region of Northern Italy.

METHODS: Epidemiological survey was the basis to estimate the potential number of PET scan per year. For this aim the most common oncological diseases registered in the hospital information system and tumor board registry, were kept into account.

Then, a cost analysis for a configuration of PET-dedicated unit was performed, considering only instruments that could ensure reduced costs but a good quality of the scans. The costs for three dedicated PET scanners were analyzed (a Na-I tomograph for option A, a BGO partial ring for option B and a BGO full ring for option C). In each case it was assumed to purchase FDG from an external distribution center. Financial data on the capital and operating costs were collected. Job costs were estimated, considering that in an initial period the workload can be reduced. In this case, the present staffing can perform the low number of examinations: afterward it is necessary to increase the working units. Furthermore, we calculated the average daily number of examinations needed to reach break even point, based on the current regional reimbursement fare for PET whole body scan (€ 1203). Finally, a "net present value" analysis of the financial investment was performed.

RESULTS: We estimated a maximal volume of 2000 PET scans/ year for each Hospital participating in the survey. Fixed, variable and total costs were calculated. Total costs ranged fTom 426110 (Option A) to 627529 (Option C) €. The adjunctive job cost for new work units can raise up to 120582 €. The break-even point ranged from 307 to 1043 scans/year, depending on the tomograph. The net present value ranged from 9360103 to 2241442 €. CONCLUSIONS: This study demonstrates that it is financially feasible to install a PET unit in an Italian General Hospital. Break-even point is easily reached, if the costs for facility construction and manpower are minimized.