Study of reperfusion on MR diffusion-weighted imaging in rat models with cerebral ischemia

Objective:Using MR diffusion-weighted imaging(DWI) to investigate the dynamic changes of cerebral ischemia after early reperfusion in rat models with acute cerebral infarct.Methods:Sixteen male SD rats were chosen,cerebral ischemic models were established by right middle cerebral artery occlusion(MCAO) with floss embolization.The SD rats were randomly divided into reperfusion group(reperfusion 2h following MCAO) and control group(permanent ischemia after MCAO),with 8 rats in each group.DWI was performed 30min,2h,6h,12h and 24h after MCAO.The infarction volume and the increased rate of infarction of each group displayed on DWI were calculated and compared as well as the apparent diffusion coefficient(ADC) values at the level with the largest infarct area.All the rats were sacrificed after MR scanning protocols were finished and the cerebral ischemic tissues were examined by histopathology with hematoxylin and eosin(HE) staining and compared with DWI findings.Results:All of the two groups showed abnormal hyperintensity in the right cerebral ischemic region on DWI and reduced signal on ADC maps after MCAO.The increased rate of infarcted volume in reperfusion group was lower than that of permanent ischemia group 2h,12h and 24h after MACO respectively,yet it showed statistical differences only at 12h and 24h after MACO(P0.05).No statistic differences were existed on ADC value and rADC value in the infarcted areas of the reperfusion group and control group at 30min after MCAO(P0.05),while the ADC values and rADC values in the reperfusion group at 2h,6h,12h,24h were all obviously lower than that of control group(P0.05).The infarction volumes after MACO on HE staining were in consistent with that on DWI in the two groups with no statistical differences(P0.05).Conclusion:DWI could sensitively demonstrate early reperfusion after cerebral infarction,it was very helpful in evaluating the therapeutic effect.