Reperfused rat myocardium subjected to various durations of ischemia: Estimation of the distribution volume of contrast material with echo-planar a IR imaging

PURPOSE: To estimate and compare the fractional distribution volume (fDV) o f gadodiamide injection and technetium 99m-diethylenetriaminepentaacetic ac id (DTPA) in the reperfused myocardium of rat hearts subjected to various d urations of ischemia. MATERIALS AND METHODS: Magnetic resonance (MR) imaging and autoradiography were performed in rats subjected to 20, 30, 40, or 60 minutes of regional i schemia followed by 1 hour of reperfusion. The fDVs of gadodiamide injectio n and Tc-99m-DTPA were measured and compared by using inversion-recovery ec ho-planar imaging and autoradiographic phosphor imaging, respectively. RESULTS: The mean fDV of both tracers (gadodiamide and Tc-99m-DTPA) in norm al myocardium was 18% +/- 1, whereas that in the entire area at risk increa sed significantly (P < .05) with 20, 30, 40, and 60 minutes of ischemia to 32% +/- 1, 57% +/- 4, 66% +/- 2, and 68% +/- 2, respectively. The fDV was s ignificantly (P < .05) greater in the core of infarction-78% +/- 4, 89% +/- 5, and 88% +/- 5 with 30, 40, and 60 minutes of ischemia, respectively-tha n in the normal myocardium or in the area at risk. CONCLUSION: The fDV of MR contrast material in the periinfarcted rim was si gnificantly (P < .05) greater than that in the normal myocardium, but signi ficantly less than that in the core of infarcted myocardium.