Scholarly article on topic 'Role of computed tomography and magnetic resonance imaging in diagnosing pericardial lesions'

Role of computed tomography and magnetic resonance imaging in diagnosing pericardial lesions Academic research paper on "Clinical medicine"

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{"Constrictive pericarditis" / "Pericardial effusion" / "Pericardial masses" / "Cardiac MRI" / "Pericardial lesions"}

Abstract of research paper on Clinical medicine, author of scientific article — Noha H. Behairy, Ayman N. Moharram

Abstract Objective In this research, patients who had pericardial lesions are imaged by either CT or MRI and the purpose of this paper is to discuss which imaging modality should be used in the assessment of patients with different pericardial diseases. Patients and methods Thirty patients ranging in age between 3months and 46years diagnosed as having pericardial lesions by transthoracic echocardiography were prospectively studied. All patients were examined by history taking, chest X-ray, clinical examination, transthoracic echocardiography, Multidetector CT and/or magnetic resonance imaging. Result Several types of lesions were identified including constrictive pericarditis (n =10), pericardial simple effusion (n =9), pericardial tumors (n =5), pericardial abscess (n =4), pericardial hemorrhage (n =4) and one case of pericardial cyst. Three patients had combined lesions. Conclusion CT and MR imaging should be used when findings at echocardiography are difficult to interpret, inconclusive or conflict with clinical findings. CT is better used for the assessment of postoperative cases while MRI is superior in detecting and diagnosing pericardiac masses and constrictive pericarditis. Also, because of radiation involving CT scan should be avoided in children if possible but has the advantage of fast imaging speed and often no need for sedation of patients and children.

Academic research paper on topic "Role of computed tomography and magnetic resonance imaging in diagnosing pericardial lesions"

The Egyptian Journal of Radiology and Nuclear Medicine (2012) 43, 389-395

Egyptian Society of Radiology and Nuclear Medicine The Egyptian Journal of Radiology and Nuclear Medicine

www.elsevier.com/locate/ejrnm www.sciencedirect.com

ORIGINAL ARTICLE

Role of computed tomography and magnetic resonance imaging in diagnosing pericardial lesions

Noha H. Behairy a *, Ayman N. Moharram b

a Department of Radiology, Kasr El Aini Hospital, Cairo University, Cairo, Egypt b Department of Critical Care Medicine, Kasr El Aini Hospital, Cairo University, Egypt

Received 18 March 2012; accepted 20 June 2012 Available online 20 July 2012

KEYWORDS

Constrictive pericarditis; Pericardial effusion; Pericardial masses; Cardiac MRI; Pericardial lesions

Abstract Objective: In this research, patients who had pericardial lesions are imaged by either CT or MRI and the purpose of this paper is to discuss which imaging modality should be used in the assessment of patients with different pericardial diseases.

Patients and methods: Thirty patients ranging in age between 3 months and 46 years diagnosed as having pericardial lesions by transthoracic echocardiography were prospectively studied. All patients were examined by history taking, chest X-ray, clinical examination, transthoracic echocar-diography, Multidetector CT and/or magnetic resonance imaging.

Result: Several types of lesions were identified including constrictive pericarditis (n = 10), pericardial simple effusion (n = 9), pericardial tumors (n = 5), pericardial abscess (n = 4), pericardial hemorrhage (n = 4) and one case of pericardial cyst. Three patients had combined lesions. Conclusion: CT and MR imaging should be used when findings at echocardiography are difficult to interpret, inconclusive or conflict with clinical findings. CT is better used for the assessment of postoperative cases while MRI is superior in detecting and diagnosing pericardiac masses and constric-tive pericarditis.

Also, because of radiation involving CT scan should be avoided in children if possible but has the advantage of fast imaging speed and often no need for sedation of patients and children. © 2012 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V.

All rights reserved.

* Corresponding author. Address: Apartment 13, 47, Street 199, Degla, Maadi, Cairo, Egypt. Tel.: +20 002 0225203545/002 01227781598.

E-mail address: nohabehairy@gmail.com (N.H. Behairy).

Peer review under responsibility of Egyptian Society of Radiology and

Nuclear Medicine.

1. Introduction

The pericardium is a two-layered membrane that envelops all four cardiac chambers and the origins of the great vessels. The parietal and visceral layers are separated by a small amount of serous fluid—normally, about 15-50 mL that is mainly an ultrafiltrate of plasma (1).

The upper limit of normal for the thickest part of the pericardium is 2 mm on CT (2,3). On MRI the pericardium appears as a low intensity signal between a high intensity signal

0378-603X © 2012 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.Org/10.1016/j.ejrnm.2012.06.004

of mediastinal and subepicardial fat, thickness ranges from 1 to 3 mm (4).

Many disease processes affect the pericardium, including infection, neoplasm, trauma, primary myocardial disease, and congenital disease. Echocardiography is the imaging modality most often used for the initial evaluation of pericardial diseases, especially in patients suspected of having pericardial effusion or tamponade. Echocardiography is readily available and does not involve ionizing radiation. However, the restricted acoustic window limits the usefulness of this modality for imaging of the entire pericardium (5).

Computed tomography (CT) and magnetic resonance (MR) imaging offer distinct advantages in the imaging of the pericardium. Both modalities provide a larger field of view than echocardiography, thus allowing the examination of the entire chest and detection of associated abnormalities in the mediastinum and lungs. Soft tissue contrast on CT scans and MR images is superior to that on echocardio-grams. CT and MR imaging provide excellent anatomic delineation and enable precise localization of pericardial masses. In addition, CT and MR imaging are performed in standard imaging planes and do not require use of a transducer; therefore, they are less operator dependent than echocardiography (6,7).

Optimal management of patients with suspected pericar-dial disease requires familiarity with the key imaging modalities and the ability to choose the appropriate imaging tests for each patient [8]. In this research, the advantages and limitations of CT and MRI for the evaluation of pericardial diseases are discussed to specify the best imaging modality used in the assessment of patients with different pericardial diseases.

2. Patients and methods

Thirty patients ranging in age between 3 months and 46 years (16 males and 14 females) diagnosed as having pericardial lesions by transthoracic echocardiography were prospectively studied. 28 were adults while two were children. The study was conducted over a period of one year starting from December 2010 to December 2011. All patients were examined by history taking, chest X-ray, clinical examination, transthoracic echocardiography, Multidetector CT and/or magnetic resonance imaging after taking an informed verbal consent from the patients or their guardians.

3. Clinical findings

Patients experienced variable symptoms and signs of: dyspnea, fever, respiratory distress, myocardial dysfunction, congestive heart failure and LL edema.

4. Transthoracic echocardiography

Two dimensional transthoracic echocardiography was performed using Hewlett Packard (sonos 4500) with 8 or 4 mHz transducers for pediatric patients and 2 mHz for the adult group. The thickness, content and sonographic texture of the pericardium as well as the whole heart were documented.

5. Multidetector computerized tomography

Patients were imaged by light speed plus GE medical system Milwaukee, Wisconsin four channel multidetector row scanner in supine position. Slice thickness was 1 cm and 360 FOV using a high spatial resolution algorithm. Scanning protocol included mA of 300, kV of 120 in the mediastinal window of ww of 313 and wl of 45. IV contrast was given when needed. Images were analyzed for the presence of pericardial fluid, masses or localized collections as well as pericardial calcification. Additional findings in the lungs or heart were also recorded e.g. Cardiac chamber enlargement, dilated IVC, pulmonary infection and pleural effusion.

6. Magnetic resonance imaging

Twenty-three patients were imaged by a Philips Gyroscan Intera 1.5 tesla super conducting magnet using the cardiac coil and ECG triggering.

MRI was not performed on postoperative patients (no = 7) with valve prosthesis and/or metallic sutures at the sternum.

Patients were examined in supine position; ECG leads and respiratory trigger were applied and adjusted until a good signal was obtained.

6.1. MRI protocol

Multiple stack survey provided coronal, transverse and sagittal images followed by:

• Gradient echo sequences bFFE (balanced fast field echo) in four chambers, short axis and coronal views were performed with TR/TE = 3.2/1.7, 215-256 x 256 matrix and 50° flip angle 8-10 mm slice thickness, 10-14 slice numbers encompassing the heart and mediastinum with 300-350 mm FOV according to the body dimensions for all patients.

• T1 weighted images with TR/TE = 600-750/25-30 and T2 weighted images with TR/TE = 1300-1700/75-85, 156 x 256 matrix, were taken in cases of pericardial masses and constrictive pericarditis.

• Post enhancement with intravenous gadolinium-based contrast material was done when needed (0.1 mm/kg) in short axis, four chambers and coronal views.

The thickness, signal of the pericardium and fluid content were evaluated. In the presence of a localized lesion its size, site and tissue characterization were assessed. Associated abnormalities in the cardiac chambers or lungs were recorded including e.g. valve lesions, motion wall abnormalities, intracardiac extension of tumors and pleural effusion.

7. Results

Thirty patients were included in this study ranging in age between 3 months and 46 years. 16 of them were males while 14 were females. Several types of lesions were identified including: Constrictive pericarditis (n = 10), Pericardial effusion (simple) (n = 9), Pericardial tumors (n = 5), Pericardial abscess (n = 4), Pericardial hemorrhage (n = 4) and one case of pericardial cyst (Table 1).

Table 1 Different pericardial lesions included in the study.

Pericardial lesion No. of patients Percentage

Constrictive pericarditis 10 33

Simple pericardial effusion 9 30

Pericardial tumors 5 16

Pericardial abscess 4 13

Pericardial hemorrhage 4 13

Pericardial cyst 1 3

Fig. 1b Four chamber gradient echo MRI of the same patient showing diffuse thickening of the pericardium (arrows) most evident on the left ventricle free border, dilated cardiac chambers as well as bilateral pleural effusion more on the left side (star) No evident pericardial effusion.

Three patients had combined lesions, two of them showed constrictive pericarditis with effusion and one case showed pericardial fibroma with surrounding effusion.

MRI was performed for twenty-three patients, while CT was of particular importance in cases of postoperative lesions, where MRI was not feasible due to the metallic sutures or prosthesis applied.

Thirteen patients showing signs and symptoms of restricted ventricular filling suggestive of constrictive pericarditis versus restrictive cardiomyopathy by clinical examination and echocardiography were examined.

Combined CT and MRI diagnosed ten cases as constrictive pericarditis and three as restrictive cardiomyopathy. Only two of the cases showed pericardial calcification, while another two showed the presence of pericardial effusion on CT scan. CT was not able to distinctly show the exact thickness of the pericardium especially in the presence of a small amount of effusion.

MRI showed pericardial thickening, however pericardial calcification was not seen. Patients had pericardial thickness ranging from 6 to 18 mm. Seven cases showed diffuse pericardial thickening more over the right ventricle (Fig. 1), while three cases showed localized thickness at the free wall of the right ventricle (Fig. 2). In addition cine MRI detected the bouncing movement of the interventricular septum and the presence of tubular ventricles which are characteristic of constrictive pericarditis (Fig. 2). Dilated cardiac chambers were found in seven cases and pericardial effusion in two cases. The overall cardiac function and ventricular volume were also estimated by MRI.

Associated findings like dilated IVC and pleural effusion were detected by both CT and MRI.

Fig. 1a CT scan showing diffuse pericardial thickening with no calcification suspicious of effusion with bilateral pleural effusion.

Fig. 1c Short axis view of the heart in black blood image showing diffuse thickening of the pericardium (arrows).

One of the cases showed adhesive constrictive pericarditis in which the pericardium over the free right ventricle wall was thickened and adherent to the wall of the right ventricle by strands of fibrosis on MRI. CT of this case showed thickened pericardium with no calcification but was not able to detect the fibrotic strands attached to the RV myocardium (Fig. 3). This case was misdiagnosed on echocardiography as fibrous band within the right ventricle restricting its movement.

Cases with restrictive cardiomyopathy showed normal peri-cardial thickness with both atria dilated (not included in the study).

Pericardial effusion was found in nine cases. Five were isolated effusion (Fig. 4) (no other cardiac lesions), while four cases showed associated lesions. One case showed pericardial fibroma, another case showed the presence of arrythmogenic right ventricular dysplasia while two were associated with

Fig. 2a Four chamber view of the heart in gradient echo showing marked localized thickening of the pericardium over the free lateral right ventricle (arrows), tubular shaped ventricle (star) and two dilated atria.

Fig. 3a CT scan showing thickened pericardium over the right ventricle and atrium with no calcification (arrows) associated right pleural effusion is noted.

Fig. 2b Short axis view of the heart in gradient echo showing localized pericardium thickening over the RV (arrows).

Fig. 3b Gradient echo MRI in Short axis view showing thickened pericardium (long white arrows) with small fibrous bands (short white arrows) seen within the epicardial fat adherent to the RV wall (black arrows).

constrictive pericarditis (Fig. 2). CT attenuation was between 8 and 13HUs. On MRI pericardial effusion showed high intensity signal on gradient echo and T2wis and low intensity signal on T1wis.

Echocardiography showed inconclusive collections in six cases. CT diagnosed three as pericardial abscesses and three as pericardial hemorrhage.

Four cases of pericardial abscesses were diagnosed in this study. Three post operative cases showed a well defined rounded abscess with rim enhancement at the retrosternal region by CT (Fig. 5). The forth case was misdiagnosed as a cardiac mass by echocardiography, showing a large pericardial collection with enhanced rim on MRI (Fig. 6).

Pericardial hemorrhage was diagnosed in four cases, three were post operative cases for open heart surgeries and the fourth patient had a thrombolytic condition. CT scan showed

mixed high and low density fluid seen trickling between the big vessels and contained within the pericardial sac (Fig. 7).

MRI diagnosed five cases of pericardial masses, two cases of metastases, and one case of fibroma, lipoma and fibrosar-coma each. MRI detected the size, site, extent and signal characteristic of each mass.

The case of pericardial fibroma was detected in a 3 month infant and was misdiagnosed on echocardiography as a large infiltrative lesion involving the left ventricle wall. MRI clearly characterized a well defined oval shaped non-enhancing mass with a low intensity signal on both T1 and T2wIs surrounded by pericardial effusion.

Pericardial Lipoma showed characteristic fat signal; high in T2 and T1wIs and low on fat suppression sequences. Pericar-dial fibrosarcoma was heterogeneously high on both T2 and T1wIs with suspected infiltration to the myocardium (Fig. 8).

Fig. 4 Four chamber gradient echo view of the heart showing simple high intensity signal pericardial effusion with normal pericardial thickness and normal cardiac chambers.

Both cases of pericardial metastases were secondary to squamous cell carcinomas.

Pericardial cyst was diagnosed in one case. The patient was known to have hydatid disease, so the cyst was considered a hydatid cyst.

8. Discussion

Echocardiography is considered the primary imaging modality for the evaluation of pericardial effusion because of its high sensitivity and specificity, lack of ionizing radiation, and low cost. CT and MR imaging are indicated when loculated or hemorrhagic effusion or pericardial thickening is suspected or when findings at echocardiography are inconclusive. (8).

Because the pericardial sac can be easily and completely visualized on CMR, this technique is superior to echocardiog-raphy in detecting the distribution and amount of fluid accu-

Fig. 6 Coronal T2wi showing a large high intensity signal collection inferior to the LV (star), another smaller one is seen just above the LV (smaller star).

Fig. 7 CT scan of a postoperative patient showing a collection with mixed high and low density at the right side of the heart denoting hematoma (arrows). Note the sutures and mitral valve prosthesis.

mulation, CMR can detect pericardial effusions as small as 30 ml (9).

CT effusion usually has attenuation of water, while non hemorrhagic effusion has a low intensity signal of Tl-weighted imaging and a high intensity signal on GRE cine images (10,11).

Nine cases of simple effusion were presented showing an attenuation between 8 and 13HU while cases of hemorrhagic effusion showed a high density fluid within the pericardium with 50-80HU on CT scan. MRI showed high intensity signal on GRE cine images in cases of effusion (Figs. 2 and 3). Loculated effusions, especially those in anterior locations, can be difficult to detect at echocardiography (5) but are readily demonstrated at CT or MR imaging. CT confirmed the inconclusive diagnosis of echocardiography in cases of pericar-dial abscesses which were located anteriorly at the retrosternal region (Fig. 4). Also MRI diagnosed a case of large pericardial

Fig. 5 CT scan showing a well defined abscess (star) with enhanced thickened rim and air loculi in a postoperative patient (note the sutures and the metallic mitral valve prosthesis). Bilateral mild pleural effusion is also noted.

Fig. 8 Coronal T1 with GTPA showing a large right sided pericardial heterogeneously enhancing mass proved to be pericar-dial fibrosarcoma on biopsy.

collection with enhanced pericardium which was misdiagnosed by echocardiography as a mass lesion (Fig. 5).

Both constrictive pericarditis and restrictive cardiomyopa-thy limit diastolic filling and result in diastolic heart failure, with relatively preserved global systolic function, hence they could not be differentiated on clinical basis (12). MR imaging has a reported accuracy of 93% for differentiation between constrictive pericarditis and restrictive cardiomyopathy on the basis of depiction of thickened pericardium (13,14). Such information was used to detect ten cases of constrictive pericarditis out of thirteen cases that showed signs and symptoms of restricted ventricular filling.

Oyama et al. stated that in most cases pericardial constriction is noted at the right side of the heart only.(13) In this study only three cases had localized constriction on the right ventricle, however most of the diffuse cases showed increased thickness on the right ventricle than on the rest of the heart.

According to Boagart and Francone the useful criteria to assess pericardial thickness by CMR are (a) pericardial thickness 2 mm or less: normal, (b) pericardial thickness greater than 4 mm: suggestive of pericardial constriction in patients

with the appropriate clinical presentation, (c) pericardial thickness greater than 5-6 mm: high specificity for constriction (10). Based on these values cases with pericardial thickness more than 6 mm were diagnosed as constrictive pericarditis.

About 50% of cases show some degree of calcification. CT is the most appropriate technique to depict, even minute amounts of pericardial calcium, whereas significant deposits may be missed by CMR (11,13).

Similar results were found in two cases with pericardial calcifications as they were detected by CT but not properly seen on MRI, however calcifications were found in only 20% of cases. This study also established that CMR better differentiates small effusions from pericardial thickening and has a better temporal resolution enabling detection of rapid hemodynamic processes such as a septal bounce or respiropha-sic variation in septal excursion (7,15).

Pericardial tumors are rare among them the most common benign tumors are lipoma, fibroma, teratoma and heamangi-oma (16), while the frequent primary malignant tumors are sarcomas and mesothelioma (7). On the other hand metastatic deposits are more common than primary tumors of the pericardium (17). MRI clearly detected the site, size and extent of the tumor it also characterized the type of tumor. MRI changed the diagnosis of two cases that were previously diagnosed by echocardiography as pericardial tumors into a peri-cardiac collection in the first one and pericardial aging hematoma in the second one.

MRI also corrected the misdiagnosis of infiltrative LV mass into a pericardial fibroma with surrounding effusion.

Only one case of hydatid cyst was detected in the pericardium since cardiac involvement of the hydatid disease is rare accounting for 0.2-2% of all hydatid cyst-related cases with the pericardium involved in only 10-15% of these cases (18,19).

CT cleared the inconclusive diagnosis of echocardiography in post operative cases as it was able to differentiate pericardial abscess from hemorrhage.

Both CT and MRI have a large field of view and detected the associated pericardial lesions in the thorax such as the presence of dilated IVC, congested liver, pulmonary lesions predisposing to pericardial effusion and the presence of hepatic cyst in one case. Such information could not be detected by echocardiography.

Table 2 Advantage and limitations of CT scan in evaluation of different pericardial lesions.

Advantage of CT scan Limitation on CT scan

• Assess pericardial calcification • Used in postoperative cases • Fast imaging speed • Fast imaging speed • Not able to properly detect the size and extension of the pericardial masses • Cannot characterize nature of tumors • Cannot assess the pericardial thickness in the presence of effusion especially small amounts • Cannot assess associated intracardiac lesions or anomalies • Radiation involving CT scan, hence should be avoided in infants and children

Table 3 Advantage and limitations of MRI in the evaluation of different pericardial lesions. Advantage of MRI

Limitations of MRI

Proper detection and characterization of masses Higher delineation of pericardial thickness Proper detection of associated intracardiac pathology Evaluation of hemodynamic processes

Presence of cardiac prostheses and metallic sutures Cannot detect pericardial calcification

Both CT and MRI have advantages and limitations provided in Tables 2 and 3 which should be taken into consideration when choosing the diagnostic modality in pericardial lesions.

9. Conclusion

CT and MR imaging should be used as a complementary tool to echocardiography when findings at echocardiography are difficult to interpret, inconclusive or conflict with clinical findings. CT is better used for assessment of postoperative cases while MRI is superior in detecting and diagnosing pericardial masses and constrictive pericarditis. CT should be avoided in infants and children due to its radiation dose whenever possible.

References

(1) Edwards ED. Applied anatomy of the heart. In: Giuliani ER, Fuster V, editors. Cardiology: fundamentals and practice. St Louis, Mo: Mosby-Year Book; 1991. p. 47-51.

(2) Delile JP, Hernigou A, Sene V, et al. Maximal thickness of the normal human pericardium assessed by electron beam computed tomography. Eur Radiol 1999;9:1183-9.

(3) Deepak, Talreja DR, Edwards WD, et al. Constrictive pericarditis in 26 patients with histologically normal pericardial thickness. Circulation 2003;108:1852.

(4) Frank H, Globits S. Magnetic resonance imaging evaluation of myocardial and pericardial disease. J Magn Reson Imaging 1999;10: 617-26.

(5) Yousem D, Traill TT, Wheeler PS, et al. Illustrative cases in pericardial effusion misdetection: correlation of echocardiography and CT. Cardiovasc Intervent Radiol 1987;10:162-7.

(6) Wang Z, Reddy G, Gotway M, et al. CT and MRI imaging of pericardial disease. RadioGraphics 2003;23:S167-80.

(7) Verhaert D, Gabriel R, Johanstone D, et al. Role of multimo-dality imaging in management of pericardial disease. Circ Cardiovasc Imaging 2010;3:333-43.

(8) Yared K, Baggish AL, Picard MH, et al. Multimodality imaging of pericardial diseases. JACC Cardiovasc Imaging 2010;3(6): 650-60.

(9) Bull RK, Edwards PD, Dixon AK. CT dimensions of the normal pericardium. Br J Radiol 1998;71:923-5.

(10) Boagart, Francone. Cardiovascular magnetic resonance in pericardial diseases. J Cardiovasc Magn Reson 2009;11(1):14.

(11) O'Leary M, Williams PL, Williams MP, et al. Imaging of pericardium: appearance on ECG-gated 64-detector row cardiac computed tomography. Br J Radiol 2010;83:194-205.

(12) Khandakar MH, Espinosa RE, Nishimura RA, et al. Pericardial disease: diagnosis and management. Mayo Clin Proc 2010;85(6): 572-93.

(13) Oyama N, Oyama N, Kamuro K, et al. CT and MRI of the pericardium anatomy and pathology. Magn Reson Med Sci 2004;13(3):145-52.

(14) Masui T, Finck S, Higgins CB, et al. Constrictive pericarditis and restrictive cardiomyopathy: evaluation with MR imaging. Radiology 1992;182:369-73.

(15) Breen JF. Imaging of the pericardium. J Thorac Imaging 2001;16: 47-54.

(16) Van Beek JR, Stolpen AH, Khanma G, et al. CT and MRI of pericardial and cardiac neoplastic disease. Cancer Imaging 2007: 719-26.

(17) Smith W, Beacock D, Goddard A, et al. Magnetic resonance evaluation of the pericardium. Br J Radiol 2001:384-92.

(18) Gossios K, Passas G, Kontogiannis D, Kakadellis J. Mediastinal and pericardial hydatid cysts: an unusual cause of circulatory collapse. AJR 2003;181:285-6.

(19) Zidi A, Zannad-Hantous S, Mestiri I, et al. Hydatid cyst of the mediastinum: 14 case reports. J Radiol 2006;87:1869-74.