小鼠缺血性脑梗死模型的制作及7TMR成像的实验研究

Construction and 7T MR imaging of mouse ischemic cerebral infarction model

目的线栓法制作小鼠缺血性脑梗死模型,小动物专用高场MR(7T)观察其不同时间段成像特点。方法线栓法制作小鼠脑梗死模型30只,术前及术后不同时间应用MR进行扫描,以出现神经症状及弥散加权像(DWI)高信号判断为模型成功,并将MR影像与病理切片对照分析。结果模型成功率为90%(27/30,1只术中死亡,2只未见明显病灶);DWI于术后40min即可见高信号区,范围随时间延长而扩大,6h后T2加权像(T2WI)出现高信号改变,T1WI相应区域脑组织肿胀,表现为稍低信号;12h内T2WI高信号区域面积较DWI高信号区域面积小(P<0.05);病理TCC染色证实病变区为梗死区,该区域细胞溶解。结论线栓法制作小鼠缺血性脑梗死模型稳定可行,7T MR扫描反映脑组织改变具有高度的敏感性及特异性,与病理具有良好的一致性,为脑梗死范围的评价、后期治疗评价提供实验基础。

Objective To establish an experimental model of ischemic cerebral infarction by occluding the right middle cerebral artery in mouse, and then to observe the images characteristics of it with 7T magnetic resonance system. Methods Thirty male mice underwent operation and were observed by MR before and after surgery on different time points randomly. The model was defined as successful model with neurological scores and high signal on diffusion-weighted imaging （DWI）. The MRI findings were confirmed by pathology. Results The successful rate of making model was 90% （27/30, one died during operation and the other two had no obvious abnormal）. High signal on DWI was detected on 40 min after operation, and the range of high signal extended with the lasting of time. High signal on T2WI was found after 6 h and swelling of brain tissue was observed on T1WI, which were moderate low signal. Within 12 h after surgery, the range of high signal in T2WI was less than that in DWI （ P 〈0.05）. The site of abnormal signal was proved as infarcted area by TTC, as well as cytolysis was observed in the region supplied by the occluded artery. MRA showed the signal of the occluded artery disappeared and resumed after pulled out the line embolism. Conclusion Modified method of constructing model is reliable and stable. 7T MR has high sensitivity and specificity in reflecting the ischemic changes of brain and has some significance in early diagnosis and therapeutic review of cerebral isehemia.