急性脑缺血再灌注DWI及PWI的实验研究

Diffusion and Perfusion MR Imaging of Acute Cerebral Ischemia with Reperfusion:A Experiment in Rats

目的:评价DWI及PWI判定急性脑梗死诊断及缺血半暗带的作用。材料和方法:40只SD大鼠随机均分4组,A组作假手术对照;B、D组分别栓塞2h、6h,均再灌注2h、24h;C组栓塞2h再灌注24h、7d。B、C、D组于各自栓塞及再灌注时间点行DWI、PWI及常规序列扫描;后处理获得表观扩散系数(ADC)、脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)形态图。并将结果与四氮唑红(TTC)染色和病理作比较。结果:A组DWI、PWI、TTC染色及病理观察均无异常;B、C、D组栓塞时均可见右大脑中动脉供血区DWI呈高信号,D组异常信号区面积明显大于B组,病理电镜表现为细胞内水肿。B、D组再灌注24hDWI异常信号区面积与灌注前相比,B组无明显变化,D组较前增大;C组再灌注7d6只大鼠DWI见高信号,但ADC图均正常。B、D组栓塞时右大脑中动脉供血区PWI灌注缺损区面积相似。B组PWI异常信号面积大于DWI异常信号区;D组PWI与DWI异常信号面积无明显差别。结论:DWI能灵敏反映急性期缺血脑组织损伤情况,PWI能灵敏反映组织血流灌注情况。DWI、PWI联合应用有可能判定缺血半暗带。

Purpose：To assess the value of DWI and PWI in evaluating penumbra of acute cerebral ischemia.Materials and Methods：A total of 40 SD rats were randomly divided into four groups.Group A was sham-operated for control study,Group B,D were occluded for 2,6 hours and reperfused for 2,24 hours respectively.Group C was occluded for 2 hours and reperfused for 24 hours,7 days.DWI,PWI,T1WI,T2WI were performed before and 2,24 hours,7days after reperfusion.ADC,CBV,CBF,MTT topographical maps were reconstructed at the work station.The outcomes of serial MRI were compared with TTC stain and pathological findings.Results：In group A,neither abnormal signal of DWI,PWI nor pathological changes were found.In group B,C,D hyper-intensity signal occurred on DWI in the territory of middle cerebral artery after occlusion.The region of abnormal signal intensity on DWI was larger in group D when compared with group B,which corresponding intracellular edema revealed by electron microscopy.Twenty-four hours after reperfusion,the area of hyper-intensity in DWI was same as that before occlusion in group B and larger in group D.Seven days after reperfusion in group C,DWI showed abnormal in six rats but ADC returned to normal in all the 10 cases.Perfusion deficit maintained on PWI both in group B and D during occlusion,but the area was larger than that of DWI in group B and equal in group D.Conclusion：DWI can detect ischemic lesion sensitively and PWI can monitor hemodynamics change sensitively,so that combined DWI and PWI may define ischemic penumbra.