大鼠局灶性脑缺血后水分子弥散的异常

背景:有研究表明,弥散加权成像可以在脑缺血后数分钟即出现异常信号。目的:观察大鼠大脑中动脉脑缺血后表观弥散系数的表现及变化规律。设计:随机对照实验。单位:重庆医科大学临床学院神经内科。材料:实验于2004-04/07在重庆医科大学附属第一医院放射科完成,选择成年Wistar清结级大鼠18只。随机分为正常对照组,假手术组和脑缺血组,每组6只。方法:采用右侧大脑中动脉栓塞法制作脑缺血模型,假手术组栓塞线仅插入颈内动脉未深及大脑中动脉的起始处,正常对照组麻醉后不作任何处理。于术后7,15,30min,1,3,6,12,24h,3,7,15d,1,2个月做1HMRS检查,获得弥散加权成像和表观弥散系数值。主要观察指标:大鼠脑梗死区域和对侧半球相应区域表观弥散系数值的变化。结果:大鼠缺血组DWI于术后7min出现异常高信号,此时T1WI,T2WI扫描示正常。T1WI,T2WI于缺血后1～3h出现异常高信号,随时间的推移,异常高信号的区域扩大,12h后右侧基底节和额顶叶皮质梗死,以后梗死面积增加不明显。表观弥散系数值于7min时发现降低,30min时表观弥散系数明显升高,1h后开始降低,12h时降到最低水平,24h以后又开始上升,2个月时表观弥散系数值较最低水平约增加5倍,而且随访的2个月中表观弥散系数始终保持明显上升的趋势。相对表观弥散系数显示出相反的变化。结论:表观弥散系数均可以超早期揭示脑缺血的发生,同时对脑血管疾病慢性期也非常敏感。

Abnormality of water molecular diffusion of rats after focal cerebral ischemia

BACKGROUND: Some researches report that diffusion-weighted imaging (DWI) can appear abnormal signal in minutes after cerebral ischemia.OBJECTIVE: To investigate the manifestation and regularity of diffusion coefficient in middle cerebral artery occlusion (MCAO) of rats after cerebral ischemia.DESIGN: Randomized controlled study.SETTING: Neurological Department of Clinical College of ChongqingMedical University.MATERIALS: The experiment was conducted at the Radiological Department of the First Affiliated Hospital of Chongqing Medical University from April to July 2004. Totally 18 adult Wistar rats with clean grade were randomly divided into three groups: control group, sham operation group and cerebral ischemia group with 6 rats in each group.METHODS: The origin of right middle cerebral artery was blocked with filament into right internal carotid. In the sham-operated group, the filament was just inserted into the common carotid artery not into the origin of middle cerebral artery, rats in normal control group were not treated with anything after anesthesia. MRI experiments were performed on a 1.5 T GE signa Highspeed NMR spectrometer to obtain DWI and ADC values at the time-point of 7, 15, 30, 60 minutes, 3,6, 12, 24 hours, 3, 7, 15 days, 1 and 2 months after operation.MAIN OUTCOME MEASURES: Changes of ADCs in infarct hemisphere and contralateral hemisphere.RESULTS: There was no significant change in MRI T1-and T2-weighted imaging in rats at 7 minutes post-infarction, but abnormal high intensity was emerged during the period of 1 hour to 3 hours, and enlarged over time. Finally, the infarction area located the right basal ganglia and the frontal-parietal lobes at 12 hours and increased less significantly later.Focal abnormal high signal was noted in DWI 7 minutes after cerebral ischemic insult, and the ADC values was decreased at the same time,reduced gradually after significant recover at 30 minutes, dropped to the lowest level at 12 hours and again increased at 24 hours, since then all the ADC values were remained high throughout follow-up, which increased by 5 times at 2 months than that at 12 hours. Correspondingly,rADC values showed the contrary pattern of evolution.CONCLUSION: It is reflected that ADC is highly sensitive not only to onset of cerebral ischemia but also to chronic cerebral ischemia.