中文摘要：

目的：研究大鼠急性脑缺血-再灌注模型缺血半暗带（IP）的扩散加权成像（DWI）和扩散张量成像（DTI）演变规律。方法：制作大鼠大脑中动脉闭塞缺血模型。分为永久缺血组，0．5h、1．5h、2．5h和3．5h4个再灌注组。在0．5～24h内行T2WI、DWI及DTI检查，测定缺血灶不同部位的ADC、DCavg、FA值，计算病侧与对侧正常组织的相对值。结果：缺血核心与边缘区之间9～12h内的rADC和rDCavg、6h内的rFA有显著性差异（P〈O．05）。2．5h和3．5h再灌注组与永久缺血组组间分析无显著性差异（P〉O．05）。结论：大鼠MCAO模型缺血灶ADC、DCavg、FA值具有特征性演变规律；IP存在时间窗为9～12h，再灌注的时间窗应小于2．5h。

英文摘要：

Objective To study the evolvement of ischemic penumbra （IP） on diffusion weighted imaging （DWI） and diffusion tensor imaging （DTI） in rat model of acute cerebral ischemia and reperfusion. Methods Twenty-five male Wistar rats were operated to develop middle cerebral artery occlusion model. The rats were divided into ischemia group and four reperfusion groups after 0.5 h, 1.5 h, 2.5 h and 3.5 h （5 rats in each group） respectively. In 0.5-24 h, T2WI, DWI and DTI were performed. The values of apparent diffusion coefficient （ADC）, average diffusion coefficient （DCavg） and fractional anisotropy （FA） in different area of ischemia region were measured. Results Difference of relative ADC value and relative DCavg value within 9-12 h, relative FA value within 6 h between central and peripheral parts of ischemia lesions had significance （P〈0.05）. Difference between 2.5 h and 3.5 h reperfusion groups and ischemia group had no significance （P〉 0.05）. Conclusion It had characteristic disciplinarian in changes of ADC, DCavg and FA. The present time window of is-chemia penumbra may be 9-12 h. The time window of effective reperfusion should be lower than 2.5 h.