Quantification of occlusive and reperfused myocardial infarct size with Gd-DTPA-enhanced MR imaging

The potential of Gd-DTPA-enhanced magnetic resonance imaging (MRI) for measuring infarct size was assessed in canine hearts. Twelve dogs underwent pre- and post-contrast MR imaging before and after recanalization. Infarct area was identified by triphenyltetrazolium chloride (TTC) staining of postmortal specimens in each case. Recanalization was complete in 10 dogs. High SI area was seen after reperfusion in nine of them; and it showed low signal intensity before reperfusion in seven of them. Two dogs were killed during reperfusion period: neither of them showed a low SI area before reperfusion. Necrotic regions were confirmed by TTC staining in seven of 12 dogs. Both the visual and quantitative assessment (n = 7) indicated that the extent of the low SI area before reperfusion was approximately the same as that of the necrotic region shown by TTC staining, while the high SI area seen after reperfusion was obviously larger than both the necrotic region and the low SI area on pre-reperfusion images. The correlation coefficient between low SI area and necrotic area was 0.98, and between high SI area and necrotic area was 0.80. These results suggest that Gd-DTPA-enhanced MRI may be useful for quantification of infarct size in occlusive myocardial infarction but it may overestimate in reperfused one.