超早期脑梗塞及再灌注动物模型的磁共振弥散加权成像研究

Study on Hyperacute Cerebral Infarction and Reperfusion in Rat with Diffusion Weighted Magnetic Resonance Imaging

目的 用线栓法制作大脑中动脉阻塞 (MCAO)模型 ,探讨超早期脑梗塞及再灌注后的磁共振弥散加权成像 (DWI)的表现及相应病理基础。材料与方法 2 7只Wistar大白鼠随机分 5组 :非再通组 6只 ;再通组 12只 ,分 3组 ,每组 4只 ,分别于MCAO后 3 0分钟、1小时、2小时再通 ,各组于不同时间点进行DWI和T2 WI ,于最后一次成像后取脑行红四氮唑 (TTC)染色观察 ;病理组 9只 ,于不同时间点进行光镜及电镜检查。计算各时间点的DWI和T2 WI上的异常高信号面积及兴趣区的表观弥散系数 (ADC)值及相对ADC值 (rADC)。结果 MCAO后 3 0分钟所有动物缺血区于DWI上均出现高信号 ,而T2 WI显示正常 ,随时间延长 ,信号强度升高 ,范围扩大 ,6小时内ADC值呈下降趋势。MCAO 3 0分钟及 1小时后再通者DWI上的高信号完全或部分恢复 ,而MCAO 2小时后再通者缺血区范围无恢复。结论 DWI是评价超早期脑梗塞及再灌注的敏感方法 ,可以科学地指导超早期动脉溶栓治疗 ,并为各种治疗方法的疗效评价提供客观指标。

Objective To observe the appearance of hyperacute cerebral infarction and reperfusion in rat model after middle cerebral artery occlusion (MCAO) on diffusion weighted imaging and to study the relevant pathologic basis.Materials and Methods Twenty seven Wistar rats were divided into 5 groups: group 1 (n=6), non reperfusion; group 2, 3 and 4 (n=4 for each), reperfusion at 30min, 1h and 2h ofter MCAO, respectively; group 5 (n=9), sacrificed at different intervals after MCAO for histologic and electro microscopic examination. DWI and T 2WI at different intervals were performed in all rats of group 1～4. TTC was done after the last examination. Apparent diffusion coefficient (ADC), relative ADC (rADC) and the area of hyper intensity on DWI and T 2WI were measured.Results DWI demonstrated hyper intensity in the ipsilateral hemisphere at 30min after MCAO in all rats, while T 2WI showed normal. With the lapse of time, DWI signal intensity and the area of hyper intensity increased. ADC and rADC of abnormal areas continuously declined within 6 hours after MCAO. Microscopic changes varied from scattered neural cell necrosis at 30 min to diffuse histologic damages at 24h. After reperfusion, abnormal area recovered entirely or partially in both group 2 and group 3, but no obvious changes were found in the rats of group 4.Conclusion DWI is highly sensitive to hyperacute cerebral infarction, it is very helpful in guiding clinical therapy and in evaluating therapeutic effect.