水通道蛋白磁共振分子成像对脑缺血半暗带的评价

Assessment of Ischemic Penumbra Using Aquaporin Magnetic Resonance Imaging

目的探讨多b值磁共振扩散加权(MR-DWI)水通道蛋白分子成像(AQP-MRI)对脑缺血半暗带的诊断价值。材料与方法将30只SD大鼠按随机区组设计法分为缺血组(25只,缺血1、3、6、24、48 h各5只)和对照组(5只),缺血组经历1h短暂性大脑中动脉栓塞(MCAO)建立脑缺血模型,两组分别行多模态MRI扫描,采集T2加权液体衰减反转恢复成像(T2-FLAIR)、扩散加权成像(DWI)、动脉自旋标记(ASL)及AQP-MRI(18b值DWI)图像。将AQP-MRI与T2-FLAIR不匹配的区域与传统DWI/T2-FLAIR不匹配和ASL/DWI不匹配作比较,验证AQP-MRI对缺血半暗带的诊断价值,并结合组织病理学进行评价。结果对照组在每个时间点各序列均未见异常信号。缺血组24 h内,AQP-MRI/T2-FLAIR不匹配面积与DWI/T2-FLAIR不匹配面积比较,差异有统计学意义(P<0.001);6 h内,AQP-MRI/T2-FLAIR不匹配面积与ASL/DWI不匹配面积比较,差异有统计学意义(P=0.001)。24 h内半暗带区相对比值与梗死区相对比值及正常脑组织相对比值比较,差异均有统计学意义(P均<0.001),组织病理学结果显示,半暗带区是正常脑组织向坏死转变的过渡。结论与传统的不匹配相比,AQP-MRI/T2-FLAIR不匹配可多层次、更精准地实时动态显示缺血半暗带。AQP-MRI与T2-FLAIR相结合可对缺血半暗带的评价提供有价值的影像学信息。

Purpose To investigate the diagnostic value of multiple b-value MR diffusion weighted(MR-DWI) aquaporin magnetic resonance imaging(AQP-MRI) on ischemic penumbra. Materials and Methods A total of 30 SD rats were randomly divided into ischemic group(25 rats, 1 h, 3 h 6 h, 24 h and 48 h after stroke, with five rats in each subgroup) and control group(5 rats). Ischemic model was established in ischemic group one hour after middle cerebral artery occlusion(MCAO). Multimodality MR scanning was performed in both groups and T2-weighted and fluid-attenuated inversion recovery imaging(T2-FLAIR), diffusion weighed imaging(DWI), arterial spin labeling(ASL) and AQP-MRI(18 b value DWI) images were collected. Mismatched areas of AQP-MRI and T2-FLAIR were compared with that of DWI/T2-FLAIR mismatch and ASL/DWI mismatch to verify diagnostic value of AQP-MRI on ischemic penumbra. Meanwhile, histopathology was combined for assessment. Results No abnormal signals on each sequence were seen at each time point in control group. Within 24 hours in ischemic group, difference of mismatched area of AQP-MRI/T2-FLAIR and DWI/T2-FLAIR was of statistical significance(P<0.001). Within 6 hours, difference of mismatched area of AQP-MRI/T2-FLAIR and DWI/T2-FLAIR was of statistical significance(P=0.001). Regarding comparison between relative ischemic penumbra and relative infarct core as well as relative normal cerebrum within 24 hours, the difference was of statistical significance(P<0.001). Histopathological results showed that ischemic penumbra was a transition process from normal brain tissue to necrosis. Conclusion Compared with conventional mismatch, AQPMRI/T2-FLAIR mismatch can indicate real time and dynamic ischemic penumbra multi-layerly and more precisely. Combination of AQPMRI and T2-FLAIR can provide valuable imaging information to the assessment of ischemic penumbra.