大鼠早期脑缺血的表观弥散系数变化的实验研究

目的利用MRI技术研究大鼠脑缺血模型的超急性期(6 h内)及急性期影像动态演变规律。方法 10只Wistar雄性大鼠,采用线栓法制作右侧大脑中动脉栓塞(MCAO)缺血模型,分别于MCAO后0.5、2、6、12和24 h行大鼠脑部冠状位磁共振T_1WI、T_2WI及弥散加权成像(DWI)扫描,分别测量T_2WI及表观弥散系数(ADC)图像上缺血区异常信号体积、ADC值和相对ADC值(rADC),并进行分析。结果随缺血时间延长,DWI及T_2WI异常高信号体积持续增大。0.5、2、6、12和24 h各时间点ADC图像显示的脑缺血体积明显大于T_2WI(P<0.01)。缺血中心区和边缘区的ADC值均较对侧脑组织明显减低(P<0.01)。随缺血时间延长,缺血中心区、边缘区和外周区的rADC值均呈不同程度减低。缺血中心区MCAO后2、6、12和24 h的rADC值明显低于0.5 h(P<0.01);缺血边缘区MCAO后2、6、12和24 h的rADC值明显低于0.5 h(P<0.01),6 h的rADC值明显低于2 h(P<0.05),12和24 h的rADC值明显低于2 h(P<0.01),24 h的rADC值明显低于6 h(P<0.05)。结论大鼠超急性期脑缺血病变进展迅速,急性期脑缺血进展减慢,DWI检查有助于早期诊断缺血半暗带。

Experimental study of the dynamic evolution of ADC value in the early phase of cerebral ischemia in rats

Objective To investigate the dynamic evolution of magnetic resonance images in the hyperacute and acute phases of cerebral infarction of acute cerebral ischemia rat model.Methods Ten male Wistar rats were used to establish right middle cerebral artery occlusion model (MCAO).Diffusion weighted imaging(DWI),T_2 WI and T_1 WI were performed 0.5 h,2 h,6 h,12 h and 24 h after MCAO.The value of apparent diffusion coefficient(ADC) and the infarction volume on T_2 WI and ADC map were measured.Results The intensity and volume of abnormal high signal on DWI and T_2 WI gradually increased over time.The infarct volume on ADC map was significantly larger than that on T_2WI at each time point(P<0.01).The ADC values of the infarct center and infarcted edge region were significantly decreased compared with the corresponding contralateral region(P <0.01).The relative ADC(rADC) values of the infarct center,infarcted edge and infarcted peripheral region were decreased over time.The rADC values of both infarct center and infarcted edge had significant differences among examinations at different time points after MCAO(P <0.05).However,the ADC value in the infarcted peripheral region had no significant differences among examinations at different time points after MCAO(P> 0.05).Conclusion Cerebral ischemia develops rapidly in hyperacute phase and slowly during acute phase.DWI could demonstrate the ischemic penumbra within 24 hours.