PURPOSE: To evaluate in reperfused myocardial infarction in a cat model, the time-course of signal enhancement as seen on Gadomer-17 enhanced MRI, and to correlate the size of the enhanced area with that of the infarct area as revealed by on histochemical examination. MATERIALS AND METHODS: Five cats which had undergone occlusion of the LAD followed by reperfusion underwent MR imaging. After T2-weighted imaging, Gadomer-17 enhanced T1-weighted images were obtained in four cats during a six-hour period, and in one during a three-hour period. Signal intensities were measured in the enhanced and non-enhanced areas of enhanced T1-weighted images. and using 2,3,5-triphenyl tetrazolium chloride (TTC) histochemical staining, the size of the abnormal signal area on each image was compared with that of the infarct area. RESULT: The enhanced area seen on enhanced T1-weighted images showed rapidly increased signal intensity following the administration of Gadomer-17. Maximum enhancement was detected during a 40 -60 minutes period, with an average enhancement of 168 +/-9.9% of normal myocardium. TTC staining revealed that the size of the high signal area on T2-weighted images and of the enhanced area on enhanced T1-weighted images was greater than that of the infarct area (p<0.05). CONCLUSION: In reperfused myocardial infarction in a cat model, Gadomer-17 enhanced MR imaging delineates both reversibly and irreversibly damaged myocardium, with strong enhancement and a broad temporal window. We may therefore expect that Gadomer-17 is useful for demonstrating myocardial injury.