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背景:大鼠线栓法大脑中动脉闭塞再灌注模型已被广泛应用于急性局灶性脑梗死的研究,而在兔应用较少。磁共振弥散加权成像对脑缺血的检测非常敏感,是近年关注的研究热点之一。目的:应用线栓法建立兔大脑中动脉闭塞再灌注模型,探讨兔缺血再灌注后磁共振扩散加权成像的特点。设计:随机对照动物实验。单位:青岛大学医学院附属医院脑血管病研究所。材料:实验于2005-03/06在山东省脑病防治重点实验室完成。新西兰兔103只,雌雄不限,体质量1.8～3.3kg,健康状况良好,由山东省农业科学院实验动物中心提供(SCX20040013)。安静、卫生、干燥环境中饲养。兔龄10～12周。方法:动物分组:分为A组53只和B组50只。A组动物均使用标准头径0.51～0.55mm的线栓,B组线栓的头径分别为B1组0.46～0.50mm,B2组0.51～0.55mm,B3组0.56～0.60mm。将造模成功的57只兔大脑中动脉闭塞再灌注模型随机分为永久性缺血组30只(分为缺血1,3,6,12,24,48h组,每组5只)和缺血再灌注组27只(再灌注0h5只,2h5只,5h5只,11h4只,23h4只,47h4只);另取10只兔行假手术作为对照组(永久性缺血对照组5只,缺血再灌注对照组5只)。主要观察指标:①永久性缺血组磁共振弥散加权成像上高信号范围及表观扩散系数值的变化。②缺血再灌注组磁共振弥散加权成像上高信号范围及表观扩散系数值的变化。结果:造模成功的57只实验兔数据均进入结果分析。①A组缺血动物模型的成功率(26只,49.1%)明显低于B组(31只,62.0%)。②缺血组:缺血1h表现磁共振扩散加权成像的高信号伴表观扩散系数值下降,缺血不同时间点磁共振扩散加权成像上的高信号区自缺血1h逐渐增大,24h后趋于稳定,平均表观扩散系数值呈先下降后上升趋势。③再灌注组:再灌注2,5h表现为磁共振扩散加权成像上高信号区缩小及表观扩散系数值升高,再灌注11h高信号区增大伴表观扩散系数值升高,再灌注23,47h高信号区增大而表观扩散系数值下降。结论:线栓的头径和插线深度是影响大脑中动脉闭塞再灌注模型成败的主要因素。急性脑缺血后磁共振扩散加权成像高信号区及表观扩散系数值的下降,经早期再灌注后可明显改善,但持续再灌注可导致表观扩散系数值再次下降。
BACKGROUND: The rat model of middle cerebral artery occlusion and reperfusion with thread occlusion has been widely used in the study of acute focal cerebral infarction, but less in rabbits. MRI diffusion-weighted imaging is very sensitive to the detection of cerebral ischemia, which is one of the research focuses in recent years. OBJECTIVE: To establish a model of occlusion and reperfusion of middle cerebral artery (MCAO) in rabbits by thread occlusion and investigate the characteristics of MR diffusion-weighted imaging after ischemia-reperfusion in rabbits. Design: Randomized controlled animal experiments. Unit: Institute of Cerebrovascular Diseases, Affiliated Hospital of Qingdao University Medical College. Materials: The experiment was performed at Key Laboratory of Encephalopathy Prevention and Control of Shandong Province on March 13, 2005. 103 New Zealand rabbits, both male and female, body weight 1.8 ~ 3.3kg, good health, provided by the Experimental Animal Center of Shandong Academy of Agricultural Sciences (SCX20040013). Quiet, hygienic and dry environment. Rabbit age 10 to 12 weeks. Methods: Animal groups: divided into group A 53 and group B 50. Group A animals were used standard diameter 0.51 ~ 0.55mm thread bolt, the diameter of the group B thread bolt group B1 0.46 ~ 0.50mm, B2 group 0.51 ~ 0.55mm, B3 group 0.56 ~ 0.60mm. Fifty-seven models of middle cerebral artery occlusion and reperfusion injury were randomly divided into permanent ischemic group (divided into ischemia 1, 3, 6, 12, 24 and 48 hours group, 5 rats in each group) Blood reperfusion group 27 (0h5 reperfusion, 2h5 only, 5h5 only, 11h4 only, 23h4 only, 47h4 only); another 10 rabbits were sham operated as control group (5 permanent ischemic control group, missing Blood reperfusion control group 5). MAIN OUTCOME MEASURES: ① The changes of high signal range and apparent diffusion coefficient in MR perfusion weighted imaging of permanent ischemic group. ② The change of high signal range and apparent diffusion coefficient in MR diffusion-weighted imaging in ischemia-reperfusion group. Results: The data of 57 experimental rabbits with successful modeling all entered the result analysis. ① The success rate of ischemic animal model in group A (26, 49.1%) was significantly lower than that in group B (31, 62.0%). ② Ischemia group: 1 h ischemia showed high signal diffusion-weighted imaging with apparent diffusion coefficient decreased, at different time points of ischemia, the high signal area on MRI diffusion-weighted imaging gradually increased from ischemia 1h, 24h Tends to be stable, the average apparent diffusion coefficient values first and then upward trend. (3) In the reperfusion group, the high signal area and the apparent diffusion coefficient were increased in MR diffusion-weighted imaging at 2,5h after reperfusion. The high signal area increased with the apparent diffusion coefficient at 11h after reperfusion, , 47h high signal area increased apparent diffusion coefficient decreased. Conclusions: The diameter of the thread plug and the depth of the thread plug are the main factors influencing the success or failure of middle cerebral artery occlusion and reperfusion model. The decrease of high signal area and apparent diffusion coefficient of MR diffusion-weighted imaging after acute cerebral ischemia can be obviously improved after early reperfusion, but continuous reperfusion can lead to the decrease of apparent diffusion coefficient again.