Assessment of myocardial edema and area at risk in a rat model of myocardial infarction with a faster T2 mapping method

Background: The common T2 mapping is not suitable for the use in rat heart with high heart rate, unless data are acquired in multiple cardiac cycles. Purpose: To evaluate a simplified T2 mapping method for faster assessment of myocardial edema and area at risk in a rat model of myocardial infarction. Material and Methods: The simplified T2 mapping method (TR/TE, 1500 ms/10, 20, 30 ms) was implemented at a 7.0T MRI system. The accuracy of T2 mapping was compared with a standard T2 mapping method (TR, 2500 ms, 16 TEs equally spaced from 11 ms to 176 ms) in thigh muscles in rats (n=6) and a phantom. This method was further evaluated in normal rats (n=8) and rats with myocardial infarction (n=8). Late gadolinium enhancement images were also acquired in the rats with myocardial infarction. Results: T2 values of simplified T2 mapping in the muscles and phantom were 27.3±2 ms and 26.5±1.1 ms, which were similar to the T2 values obtained by the standard T2 mapping method (28.1±1.4 ms, P>0.05; 26.9±1.7 ms). No significant difference in T2 distribution (different segments and slices from base to apex) in the whole heart was found in normal rats (25.6±3.3 ms, P>0.05). The mean T2 value in the myocardial edema regions of myocardial infarction rats (37±4.9 ms) was significantly higher than that of the normal rats (25.6±3.3 ms, P<0.001). The T2 value in the myocardial infarction core of myocardial infarction rats (39.9±3.6 ms) was significantly higher than that of area at risk (34.7±2.9 ms, P<0.001). Conclusion: The simplified myocardial T2 mapping is technically feasible and accurate, and can readily detect myocardial edema and area at risk in rats with high heart rate.