7.O T磁共振灌注和弥散加权成像的缺血半暗带实验研究

目的 探讨高场强磁共振(7.0T)灌注和弥散加权成像在大鼠急性脑梗死缺血半暗带研究中的价值.方法 利用线栓法建立大鼠急性脑梗死模型.60只SD大鼠随机分成6组,即假手术对照组,栓塞0.5、1.5、3、6和24 h组,每组10只.各组大鼠于相应时间点行头颅MRI扫描:PWI、DWI、T1WI、T2WI及MRA.后处理获得脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)形态图,并分别计算rCBV、rCBF、rMTT相对值.测量DWI异常信号区相对体积(rVD)及PWI异常灌注区相对体积(rVP).将结果与四氮唑红(TTC)染色和病理对比.结果 假手术组各序列扫描、TTC染色及病理均未见异常.各栓塞组栓塞侧大脑中动脉供血区rCBV、rCBF明显降低,rMTT明显延长,梗死核心严重,梗死边缘较轻.各栓塞组栓塞侧大脑中动脉供血区于DWI和PWI均可见异常信号区;DWI异常信号区体积随栓塞时间延长而增大,PWI异常信号区体积随时间延长变化不明显,栓塞6 h前PWI异常信号区大于DWI异常信号区(P<0.05),6 h以后PWI、DWI梗死体积大小差异无统计学意义(P>0.05).3 h以后DWI梗死体积与24 hTTC梗死体积差异无统计学意义(P>0.05).结论 高场强磁共振灌注和弥散加权成像动态显示急性脑梗塞缺血半暗带的时间、空间变化,为进一步研究提供基础.

A study of ischemic penumbra by perfusion and diffusion-weighted imaging at high-field MRI (7.0 T)

Objective To approach the value of perfusion-weighed and diffusion-weighted imaging at high field intensity (7.0 T) MR in research of the ischemic penumbra in acute cerebral infarction of rats.Methods Acute cerebral infarction of rat was induced by octluding middie cerebral artery (MCAO) with suture.Sixty SD rats were divided into six groups randomly of ten including sham operation group.and groups of MCAO for 0.5,1.5,3.6,24 h.Then all rats were examined by PWI,T1WI,T2WI and MRA at corresponding time point.Regional cerebral blood volume (rCBV),relative cerebral blood flow (rCBF),mean transit time (MTT) topographical maps were reconstructed and the relative values of rCBV,rCBF,MTT,DWI-derived (rVD) and PWI-derived (rVP) lesion volume were calculated.The outcomes of serial MRI were compared with TTC stain and pathological findings.Results Neither abnormal sisnal of MBI nor TTC stain or pathological changes were found in sham operation group.The rCBV.rCBF was significantly decreased but rMTT obviously extended of the area of middle cerebral artery blood-supply of each group of MCAO.The core of infarction was more serious than the edge of infarction. Abnormal signals were found in the MCA-supplying regions in the DWI and PWI of all of the groups of MCAO.The size of rVD became bigger with the time going on but no significant difference of rVP The size of rVP was larger than rVD before MCAO of 6h(P<0.05).There was no significant difference between PWI and DWI after 6 h (P>0.05) and also between TTC at 24 h and DWI after 3 h (P>0.05).Conclusion Perfusion-weighed and diffusion-weighted imaging at high field intensity (7.0 T) MR dynamic displaying the existence and the process of ischemic penumbra in acute cerebral infarction of rats provides a basis for further study.