he purpose of this paper is to evaluate acute ischemia and reperfusion in canine models by serial 99m Tc-MIBI myocardial SPECT studies. In 24 dogs

myocardial ischemia was induced by dilated balloon inserted in LAD or LCX

followed by reperfusion at 1h （GroupⅠ）

4h （Group Ⅱ） later

and permanent ischemia by copper coil（Group Ⅲ）. The first and second imaging was taken after ischemia and after reperfusion. The 3rd

4th and 5th SPECT were at 7

14 and 28 days later. Defect fraction（DF）

and ischemic fraction（IF） was obtained from the Bull′s-eye images. The first DFs in all 3 groups correlated well with the myocardium at risk（IF） measured by pathological study. DF in group Ⅰ decreased censistently since the second SPECT

in Group Ⅱ DF had some decrease

while in Group Ⅲ no decrease of DF was measured. The SF in all animals showed the same trend. The last DF was correlated with the real size of infarct foci（NF） determined by TTC staining by pathological study. 99m Tc-MIBI SPECT was sensitive and accurate in revealing myocardial damage after acute ischemia and its response to reperfusion. The first（before）

seconed（right after）

and the last SPECT（4 weeks after reperfusion） were the most informative and clinically useful.