An interleaved T1-T2*imaging sequence for assessing myocardial injury

We developed a sequence by which T1- and T2*-weighted images can be acquire d simultaneously and demonstrated its validity for assessing myocardial inj ury. The interleaved T1-T2* imaging sequence consisted of one preparatory p ulse (a 90 degrees pulse) and a gradient-echo imaging sequence with a dynam ically variable echo time varying between 4.2 msec for T1-weighted imaging and 15 msec for T2*-weighted imaging. The sequence was tested and validated on isolated blood-perfused pig hearts (n = 4). We found that contrast agen t-induced T1 and T2* effects,were clearly delineated during the first pass and steady-state periods of a contrast agent (gadolinium diethylenetriamino pentaacetic acid). With a bolus injection of contrast agent, the maximum ch anges in T2* signal intensity occur significantly earlier than the changes in T1 signal. We also found that the maximum change in T1 signal intensity during the first pass of contrast agent was significantly gl-eater in a rep erfused-infarcted region than in normal regions. The suppression of T2* sig nal was similar in both regions. Ar steady state of contrast agent, T2* sig nal intensities gradually recovered to a significantly higher- level in the reperfused-infarcted region than in normal regions. This suggests that the contrast agent diffused into the intracellular space, indicating the loss of cell membrane integrity. As a result, T1 signal intensity was also highe r- in the reperfused-infarcted myocardium than in normal myocardium. T1-and T2*-weighted images can be acquired simultaneously. The interleaved T1-T2* sequence is useful in assessing myocardial injury.