中文摘要：

目的探讨超微超顺磁性氧化铁粒子（USPIO）增强磁共振（MR）活体监测局部脑缺血再灌注损伤炎症反应的可行性。方法40只雄性SD大鼠按照随机数字表法分为5组：氯化三苯基四氮唑（TTC）染色组（n=4）、假手术组（n=6）、缺血再灌注24h组（n=10）、缺血再灌注48h（n=10）和缺血再灌注72h组m=10）。局部脑缺血再灌注模型制作成功后经大鼠尾静脉注射USPIO，分别于再灌注24h、48h、72h行MR扫描。成像后分别于相应的时间点处死大鼠，取脑组织冰冻切片行HE染色观察细胞死亡，普鲁士蓝染色观察铁粒，CD68免疫组织化学染色和荧光标记观察巨噬细胞（活化的小胶质细胞）。结果成功的模型可以在T2WI上看到高信号的水肿区，USPIO在T1WI上呈正性强化，T2WI上呈负性增强；24hTlWI增强信号缺血侧／对侧比值为1．60±0．28，稍高于48h和72h，48h T2WI增强信号缺血侧／对侧比值为0．92±0．17，稍高于24h和72h，对照组中信号无类似变化；各时间点T1WI缺血侧增强效应均明显高于T2WI，差异有统计学意义（氏0．05）。普鲁士蓝染色证实梗死灶周边及坏死灶内可见铁粒子沉积。CD68免疫组化染色显示小胶质细胞增生活跃。结论应用USPIO这种相对细胞特异的MR对比剂，可以活体动态观察局部脑缺血再灌注损伤的炎症反应变化。

英文摘要：

Objective To assess the feasibility of ultrasmall superparamagnetic iron oxide （USPIO）-enhanced magnetic resonance imaging （MRI） for monitoring the phagocytic activity in the brain tissue of rats following focal cerebral ischemia-reperfusion （IR） injury. Methods Forty male SD rats were randomized into 5 groups, namely 2, 3, 5-triphenyltetrazolium chloride （TTC） staining group （n=4）, sham-operated group （n=6）, and 3 cerebral IR injury groups with reperfusion time of 24, 48, and 72 h （n=10）. USPIO was intravenously injected after focal cerebral IR injury, and MRI was performed at 24, 48, and 72 h after the reperfusion. The rats were sacrificed at 24, 48 and 72 h, and fi＇ozen sections of the local brain tissues were prepared to observe the cell death with HE staining, iron particle distribution with Prussian blue staining and the activity of the macrophages by CD68 immunohistochemical staining and immunofluorescent labeling. Results The ischemic lesions were identified as hyperintense area on T2-weighted images （T2WI） after middle cerebral artery occlusion （MCAO）. The accumulation of USPIO appeared as hyperintense areas on T1WI and hypointense area on T2WI. The maximum signal change was observed at 24 h on T1WI （1.60±0.28） and at 48 h on T2WI （0.92±0.17） （P〈0.05）, and at each of the time points, the enhancement was significantly greater on T1WI than on T2WI （P〈0.05）. No obvious signal changes were found in the control group. Prussian blue staining detected iron oxide particles in both the peripherals of the ischemic region and the necrotic area. A similar distribution pattern of the macrophages or activated microglia was found by CD68 immunohistochemistry and immunofluorescent labeling. Conclusion USPIO-enhanced MRI allows dynamic monitoring of the inflammatory reaction in the local brain tissues after focal cerebral IR injury.