Purpose: To investigate the contribution of proton density (PD) in T-2-STIR based edema imaging in the setting of acute myocardial infarction (AMI).
Materials and Methods: Canines (n = 5), subjected to full occlusion of the left anterior descending artery for 3 hours, underwent serial magnetic resonance imaging (MRI) studies 2 hours postreperfusion (day 0) and on day 2. During each study, T-1 and T-2 maps, STIR (TE = 7.1 msec and 64 msec) and late gadolinium enhancement (LGE) images were acquired. Using T-1 and T-2 maps, relaxation and PD contributions to myocardial edema contrast (EC) in STIR images at both TEs were calculated.
Results: Edematous territories showed significant increase in PD (20.3 +/- 14.3%, P <0.05) relative to healthy territories. The contributions of T-1 changes and T-2 or PD changes toward EC were in opposite directions. One-tailed t-test confirmed that the mean T-2 and PD-based EC at both TEs were greater than zero. EC from STIR images at TE = 7.1 msec was dominated by PD than T-2 effects (94.3 +/- 11.3% vs. 17.6 +/- 2.5%, P <0.05), while at TE 64 msec, T-2 effects were significantly greater than PD effects (90.8 +/- 20.3% vs. 12.5 +/- 11.9%, P <0.05). The contribution from PD in standard STIR acquisitions (TE 64 msec) was significantly higher than 0 (P <0.05).
Conclusion: In addition to T-2-weighting, edema detection in the setting of AMI with T-2-weighted STIR imaging has a substantial contribution from PD changes, likely stemming from increased free-water content within the affected tissue. This suggests that imaging approaches that take advantage of both PD as well as T-2 effects may provide the optimal sensitivity for detecting myocardial edema.
- myocardial edema
- proton density
- ischemia-reperfusion injury
- CARDIOVASCULAR MAGNETIC-RESONANCE