对比分析大鼠局灶性脑缺血亚急性期USPIO与Gd-DTPA增强MRI

目的 基于动物模型,对比局灶性脑缺血亚急性期超小型超顺磁性氧化铁(USPIO)与Gd-DTPA增强MRI表现的异同.方法 以6只SD大鼠建立局灶性脑缺血模型,建模成功后将其分为USPIO增强组(n=3)及Gd-DTPA增强组(n=3).对USPIO增强组于建模后第5天以1000 μmolFe2 +/kg体质量静脉注射USPIO,并于24 h后(建模后第6天)行T2W扫描.对Gd-DTPA增强组于建模后第6天行常规T2WI及T1WI后,静脉注射Gd-DTPA行增强T1W扫描,剂量0.2 mmolGd3+/kg体质量. MR检查完成后,取脑组织切片行HE和IgG染色病理观察,对MRI与病理表现进行综合对比分析.结果 USPIO增强组脑缺血灶周围可见T2WI低信号区,MR扫描增强区域与IgG染色提示的血脑屏障破坏区有所差别.Gd-DTPA增强组增强T1WI示脑缺血区明显强化,MR扫描增强区域与IgG染色所示血脑屏障破坏区相一致.结论 大鼠局灶性脑缺血亚急性期USPIO与Gd-DTPA增强MRI具有不同的特征,USPIO图像侧重于反映细胞的反应性增生,而Gd-DTPA图像更利于对血脑屏障破坏的反映.

Sub-acute focal cerebral ischemia in rat models: An in vivo comparison of USPIO- and Gd-DTPA-enhanced MRI

Objective To compare the enhanced MRI manifestations of sub-acute cerebral ischemia with ultrasmall superparamagnetic iron oxide(USPIO) and Gd-DTPA as the contrast media based on animal models.Methods Sub-acute cerebral ischemia models were established in 6 SD rats,and the rats were equally divided into USPIO group and Gd-DTPA group(each n=3).On the 5th day after modeling,intravenous injection of USPIO(1000 μmolFe2+/kg) was done in USPIO group,and MR T2WI was performed 24 h after injection(the 6th day).In Gd-DTPA group,conventional T2W,T1W and enhanced T1W scan(Gd-DTPA,0.2 mmolGd3+/kg) were performed successively on the 6th day after modeling.Pathological observation of the brain tissue sections stained with HE and IgG was performed after MR examination.MRI manifestations and the pathologic findings were comparatively analyzed in both groups.Results Low signal area was observed in ischemic periphery on USPIO-enhanced T2WI,and the enhancement region on MRI was different from the impaired area of blood-brain barrier obtained by IgG staining pathological examination.Gd-DTPA-enhanced T1WI showed the ischemic area as obviously enhanced region,and the enhancement region on MRI was coincident with the pathology confirmed blood-brain barrier impaired area.Conclusion MRI features of USPIO-and Gd-DTPA-enhanced scanning of sub-acute cerebral ischemia rats models are different.USPIO-enhanced MRI is favorable to reflect the reactive cell proliferation,while Gd-DTPA-enhanced MRI stresses in reflecting the damage of blood-brain barrier.