磁共振扩散加权成像对兔脑缺血再灌注伤的评价

目的探讨兔脑缺血再灌注后磁共振扩散加权成像（DWI）的特点。方法将成年新西兰兔用线栓法建立兔大脑中动脉闭塞再灌注（MCAO／R）模型，再将成功的兔MCAO／R模型随机分为永久性缺血组和缺血再灌注组；另取同样动物行假手术分别作为缺血组及再灌注组的对照组；观察不同时间DWI像上高信号区范围变化及表观扩散系数（ADC）的演变特点。结果1．缺血组：缺血1h可见到DWI像上明显的高信号伴ADC值的下降，缺血不同时间点DWI像上的高信号区较缺血1h均有增大，24h后趋于稳定。缺血组不同时间点平均ADC值呈先下降后上升的趋势。2．再灌注组：与再灌注前相比，再灌注2h、5h组均表现为DWI像上高信号区缩小及ADC值升高；再灌注11h组表现为高信号范围增大伴ADC值升高；再灌注23h、47h组表现为高信号范围增大而ADC值出现较明显下降。结论急性脑缺血后DWI像高信号区及ADC值的下降经早期再灌注后可明显改善，但持续再灌注可能导致ADC值再次下降。

Evaluation of Cerebral Ischemia and Reperfusion Injury with Magnetic Resonance Diffusion Weighted Imaging in Rabbits

Objective To study the changes of magnetic resonance diffusion weighted imaging(DWI) in acute cerebral ischemia and reperfusion injury. Methods Adult healthy NewZeadand rabbits(103 cases) were used to established middle cerebral ischemia and reperfusion(MCAO/R) model by intraluminal thread technique,and 58 successful models were randomly divided into permanent ischemic group(30 cases) which further divided into ischemic 1 h,3 h,6 h,12 h,24 h,48 h groups consisting 5 cases and ischemic reperfusion group 28 cases which further divided into reperfusion 0h,2h,5h,11h,23h,47h groups consisting 5,5,5,4,5,4 cases respectively.Another 10 rabbits were regarded as ischemic contrast(5 cases) and reperfusion contrast(5 cases).The changes of hyper-intensity signal area on DWI and apparent diffusion coefficient(ADC) were measured in different groups Results 1.In ischemic group rabbits,the hyper-intensity signal area on DWI with declined ADC appeared at ischemic 1h.The hyper-intensity signal areas on DWI at different times were larger than that at ischemic 1h and unchanged at 24h.The mean ADC at different times declined at first and then gradually increased.2.In reperfusion group rabbits: compared with ischemic 1h,the hyper-intensity signal area on DWI reduced while ADC increased at reperfusion 2 and 5h,but the hyper-intensity signal area on DWI enlarged with ADC high at reperfusion 11h,then the hyper-intensity signal area on DWI enlarged with ADC reduced siginificantly at 23h and 47h.Conclusion The hyper-intensity signal area on DWI and the decreasing ADC in acute cerebral ischemia could be improved by early reperfusion,but the secondary decreasing ADC would be induced with continously reperfusion.