急性脑梗塞早期MRI表现与病理对照研究

目的阻断狗大脑中动脉建立急性脑梗塞动物模型，观察早期MRI表现及其病理改变。材料与方法将16只成年狗随机分为实验组(10只)和对照组(6只)。经颞开颅阻断一侧大脑中动脉(MCA)，造成其供应区急性缺血性脑梗塞，只成年狗随机分为实验组(10只)和对照组(6只)。经颞开颅阻断一侧大脑中动脉(MCA)，造成其供应区急性缺血性脑梗塞，术后2，4，6，8，12小时行MRI薄层扫描；取出动物大脑观察病理改变，测定不同时相梗塞区T2时间和组织水含量。结果MRI最早2小时表现异常，T2加权像可见尾状核头部、豆状核信号增高；梗塞6小时，MRI可见尾状核、豆状核形成明确梗塞，并出现占位征象。梗塞2小时，电镜下已有缺血水肿改变，4小时光镜下出现脑缺血水肿改变，电镜下见血脑屏障受损。相关分析表明病灶区T2时间变化与组织水含量变化在时序上有密切关系，经t检验差别具显著意义(P＜0．01)。结论本项实验结果表明，MRI可用于脑梗塞早期的诊断，在显示病灶方面，MRIT2加权像优于T1加权像。急性脑梗塞早期MRI表现的病理基础是脑水肿。

Experimental study of acute cerebral infarction: early MRI appearances and pathologic findings

Purposes The early MRI appearances of acute cerebral infarction and its pathologic changes were studied on the model of acute cerebral ischemic dogs. Materials and methods Sixteen adult dogs were randomized into experimental groups(10 dogs) and contrast groups(6 dogs). All the dogs underwent craniectomy through transtemporal and their middle cerebral artery (MCA) ;were occuluded. The thin- slice MRI scan were examed at 2,4,6,8, 10, 12 hours on the experimental group' The histopaho- logical changes in different period were studied. The T2 relaxation time and water content in the infect regions were measured at differ- ent time. Results The MRI intensity was abnormal a early as 2 bans after ischemia: the increased signal intensity on T2WI imaging were observed at the head of caudate nucleus and the lentiform nucleus. At 6h after ischemia both MRI were found to indicate definite infarct foci in the caudate nucleus and the lentiform nucleus, mass effect was ween too. Histopathologic findings:At 2H after ischemia, electron micrograph revealed the changes of ischemic edema. At 4h after ischemia, the photomicrograph demonstrated the changes of ischemic edema and the electron micrograph indicated the damage to blood brain barrier. The correlation analysis demonstrated that the changes of T2 the were closely relative to the alteration of water content,which were confirmed to be highly statistical significant by t- test(P<0.01). Conclusion The brain edema is the histopathological basis of early MRI appearances (in 12h)of acute cerebral infarction.MRI can be applied to early diagnosis of acute cerebral infarction. MRI T2W images appeared to be more sensitive than T1W images in showing the infarction.