超急性期脑梗死半影区弥散-灌注磁共振成像实验研究

Diffusion-Perfusion MR Imaging of Hyperacute Cerebral Infarction Penumbra: An Experiment in Rats

目的 应用弥散加权 灌注 (DWI PI)磁共振成像技术对改良线栓栓塞大脑中动脉制作的大鼠超急性脑梗死模型进行实验研究 ,并与病理结果对照。明确联合应用PWI PI对超急性脑梗死半影区诊断价值。材料与方法 5 0只SD大鼠 ,随机分成 5组 ,A组 (10只 )作假手术对照 ;其余按栓塞时间 30min、1、3、6h均分成B、C、D、E4组。A组于 30min、1、3、6h的时间点 ,B、C、D、E于各自栓塞时间点行弥散加权成像 (DWI)和灌注成像 (PI)扫描 ;工作站后处理获得表观弥散系数 (ADC)、脑血容量或血流量 (CBV或CBF)、平均通过时间 (MTT)形态图 ,计算ADC、CBV、CBF、MTT相对值 (与对侧相应部位比值 )。将成像结果与四氮唑红 (TTC)染色和病理观察对比。结果 (1)A组DWI、PI成像无异常信号 ,病理观察无变化。 (2 )B、C、D、E组PI显示栓塞侧大脑中动脉供血区灌注缺损范围无变化 ,基底节区最重 ,皮质区较轻 ;DWI显示高信号 ;ADC比值降低 (6 5 .2 % ) ,D组达到最低 (32 .2 % ) ,E组基本不变(2 9.9% ) ;ADC形态图显示病灶范围逐渐扩大 ,最终 (E组 )与PI异常信号区基本一致。 (3)超急性脑梗死的DWI高信号范围与TTC染色所见的异常染色 (白色 )范围比较无显著性差异 (t检验 ,P >0 .1)。 (4 )在超急性脑梗死中存在PI DWI不重叠区 (缺血半?

Objective To experimentally study hyperacute cerebral infarction in rats produced by occluding the middle cerebral artery (MCA) with diffusion weighted imaging-perfusion imaging (DWI-PI) technique, to compared imaging findings with pathologic results and to evaluate DWI-PI combination in diagnosing ischemic penumbra in hyperacute cerebral infarction.Materials and Methods Fifty SD rats were randomly and equally divided into five groups. Group A received sham-operation and was used as control group, and DWI-PI scanning was carried out at 30min, 1h, 3h and 6h interval. Groups B, C, D and E received occlusion of the left middle cerebral artery with thread and DWI-PI scanning was carried out at 30min, 1h, 3h and 6h interval, respectively. Apparent diffusion coefficient (ADC), cerebral blood volume or flow (CBV or CBF) and mean transition time (MTT) topographic maps were obtained on a workstation. The relative value (ratio of studied side value to opposite side value) of ADC, CBV, CBF and MTT was calculated. The results were compared with TTC stain and pathologic findings.Results (1) Neither signal intensity alteration on DWI or PI nor pathologic changes were found in the group A rats. (2) In the group B, C, D and E, no difference in perfusion defect extent due to CMA occlusion was seen, which showed high signal on DWI, and ADC ratio was decreased (65.2%) with the D group being the lowest (32.2%) and the E group being almost unchanged (29.9%). On ADC topographic maps the lesion extent increased with the time, and, finally, the extent became basically the same as the abnormal signal area on PI (in the group E). (3) No significant difference in the demonstrated extent of hyperacute cerebral infarction existed between high signal area on DWI and TTC stain area (t test, P>0.1). (4) In hyperacute cerebral infarction, DWI-PI unmatched area, the ischemic penumbra, showed no marked pathologic changes, and it was decreased with time.Conclusion In hyperacute cerebral infarction, PI can demonstrate the perfusion defect zone. ADC ratio is decreased, and the lesion's extent is gradually enlarged. High signal area on DWI is in accord with the abnormal staining area on TTC stain. DWI-PI combination can well show the ischemic penumbra and its changing occurred in hyperacute cerebral infarction.