CC BY
0Journal of Cardiovascular Magnetic Resonance
BioMed Central
Open Access
Moderated poster presentation Why do we see myocardial edema in acute myocardial infarcts with balanced SSFP imaging?
Xiangzhi Zhou*1, Veronica Rundell1, Ying Liu1, Richard Tang1, Rachel Klein1 Shivraman Giri2, Saurabh Shah3, Sven Zuehlsdorff3, Orlando Simonetti2, Debiao Li1 and Rohan Dharmakumar1
Address: iNorthwestern University, Chicago, IL, USA, 2Ohio State University, Columbus, OH, USA and 3Siemens Medical Solutions USA, Inc., Chicago, IL, USA * Corresponding author
from 13th Annual SCMR Scientific Sessions Phoenix, AZ, USA. 21 -24 January 2010
Published: 21 January 2010
Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl l):MI2 doi:l0.l I86/I532-429X-12-SI-MI2
This abstract is available from: http://jcmr-online.com/content/ I2/SI/MI2 © 20I0 Zhou et al; licensee BioMed Central Ltd.
Introduction
Recent studies have demonstrated that conventional balanced steady-state free precession (b-SSFP) cine imaging can identify regions of myocardial edema in-and-around acute myocardial infarctions (AMI). However, the underlying mechanisms of b-SSFP edema contrast are not well understood. A more detailed understanding of the contrast mechanisms at play may enable opportunities for optimization of SSFP-based edema contrast.
Purpose
To investigate the mechanisms contributing to the b-SSFP-based edema contrast surrounding AMI in conventional cine b-SSFP images
Methods
Dogs (n = 3) subjected to ischemia-reperfusion injury (LAD occlusion for 3 hours followed by reperfusion) were studied at baseline (pre-injury), 2-hours post-reperfusion (day 0), and on days 2, 5, and 7. Multiple breath-held short-axis cine b-SSFP images, and T2- and T1-maps were acquired at late diastole using a Siemens Espree (1.5 T) system. All studies were terminated with PSIR late-gadolinium-enhancement (LGE) acquisitions to confirm LAD infarction. Cine SSFP imaging was performed with TR/TE = 3.5/1.75 ms; flip angle = 70°; 20-25 phases. The cardiac phase corresponding to the T1 and T2 maps were identi-
fied from the cine b-SSFP images. On these SSFP images, and the relaxation maps, a semi-automated approach was used to identify the edematous territory. Using the Freeman-Hill equation for b-SSFP and the measured signal, T1 and T2 values for edematous and healthy territories, the relative contributions from relaxation and thermal magnetization (M0) effects were estimated.
Results
Semi-automated and visual analysis did not identify regions of hyperenhancement in T1 and T2 maps, or SSFP or LGE images acquired under baseline conditions in any of the animals. Hyperintense LAD territories were readily identified on T1, T2, and cine SSFP images on days 0, 2, 5, and 7 in all dogs and the presence of AMI within the same territories was confirmed by LGE images (Figure 1). Mean relative contributions from relaxation and M0 effects, assessed over each imaging slice (across all studies), are shown in Figure 2. For all studies, signal contrast between edematous and healthy territories was 56.4 ± 14.7%. From the measured T1 and T2 maps, the theoretically expected edema contrast due to relaxation changes was 18.7 ± 9.5%.
Conclusion
Relaxation effects alone cannot explain the observed myo-cardial edema contrast in b-SSFP images. Results show
Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl 1):M12
http://jcmr-online.com/content/12/S1/M12
Figure!
Representative short-axis images obtained from a dog subject to ischemia-reperfusion injury in the LAD territory (day 0, 2-hours post reperfusion). A: T1 map; B: T2 map; C: b-SSFP; D: PSIR LGE phase image. Note that the LAD territory appears hyperintense in T1 and T2 maps, as well as in the b = SSFP image. D confirms the presence of a LAD infact.
Figure2
Mean, estimated contributions from relaxation and M0 effects to myocardial edema contrast in b-SSFP images. Note that in addition to the relaxation effects, a substantial fraction of the edema contrast originates from M0 effects, likely meditated through proton density and/or magnetization transfer mechanisms.
that M0 effects, likely from proton density and/or magnetization transfer changes between healthy and edematous territories, have a substantial contribution to the b-SSFP image contrast. Optimization strategies that wish to maximize myocardial edema contrast in b-SSFP imaging should take relaxation and M0 effects into account.
Publish with BioMedCentral and every scientist can read your work free of charge
"BioMed Central will be the most significant development for disseminating the results of biomedical research in our lifetime." Sir Paul Nurse, Cancer Research UK
Your research papers will be:
• available free of charge to the entire biomedical community
• peer reviewed and published immediately upon acceptance
• cited in PubMed and archived on PubMed Central
• yours — you keep the copyright
Submit your manuscript here:
http://www.biomedcentral.com/info/publishing_adv.asp
BioMedcentral
