T2 Mapping at 7T MRI Can Quantitatively Assess Intramyocardial Hemorrhage in Rats With Acute Reperfused Myocardial Infarction In Vivo

Purpose: To investigate T-2 mapping at 7T magnetic resonance imaging (MRI) for the detection and quantification of reperfused intramyocardial hemorrhage (IMH) in a rat model. Materials and Methods: Myocardial infarction (MI) was induced in 25 female rats. Rats were scanned at a 7T MRI 48 hours after reperfusion, using T-2 mapping and late gadolinium enhancement imaging. Gross sections of the left ventricular myocardium and corresponding hematoxylin and eosin staining were assessed for IMH. T-2 mapping images were matched with the gross sections. The IMH volume, expressed as a percentage of the left ventricular myocardial volume, of each heart determined by T-2 mapping was compared with that calculated by pathological gross examination. Results: Six rats died. In all, 97 gross sections of the left ventricular myocardium from the 19 rats were matched with T-2 mapping images. IMH occurred pathologically in 68 gross sections, which was detected as hypointense cores by T-2 mapping in 63 images (93% sensitivity). Three T-2 mapping images with hypointense cores showed no hemorrhage on pathological sections (90% specificity). The positive and negative predictive values of hemorrhage on T-2 mapping were 95% and 84%, respectively. In terms of the IMH volume, there was no significant difference between T-2 mapping and pathological gross measurements (4.8 +/- 2.4% vs. 5.3 +/- 3.2%; P=0.11). Conclusion: T-2 mapping at 7T MRI can reliably detect and quantify IMH in rats in vivo. This may be useful as a noninvasive quantitative approach to investigating the mechanisms and evolution of MI and reperfusion injury.