超急性脑缺血再灌注MRI弥散及灌注成像的实验研究

Study of DWI and PWI in superacute cerebral ischemia

目的运用磁共振弥散及灌注成像,研究栓塞前、后及溶栓后脑组织不同区域的血液动力学的变化,及其判定半暗带的价值。方法60只雄性SD大鼠(280～320g),随机分成3组A、B、C组,A组为对照组(n=10),B组为缺血2小时组(n=5×5),C组为缺血6小时组(n=5×5)。采用改良Zea Longa线栓法建立大鼠可逆性大脑中动脉栓塞模型,于再通前及再通后2h、24h用Signa Profile3.0T MRI分别行大鼠脑冠状位弥散成像、灌注加权(perfusion weighted imaging,PWI)评价血流再灌注情况。结果A组(假手术组)DWI及脑血流灌注NEI参数图均未见异常。B组(缺血2h再灌注组)再通前DWI出现大片浅淡的高信号,灌注图示大面积的灌注减低区,DWI异常面积明显小于PWI异常面积;再灌注后2h及24h DWI异常面积较灌注前稍缩小(P>0.05),灌注图像上,血流逐渐基本恢复,rNEI值逐渐升高,DWI异常面积与PWI异常面积趋向一致。C组(缺血6h再灌注组)再通前DWI出现大片高信号,范围与PWI基本一致;再灌注后随着再灌注时间的延长DWI面积无明显变化,灌注图像上,血流恢复不均,局部存在灌注缺损。结论磁共振脑血流弥散及灌注成像可定量地提供脑组织血流量的动态变化信息,并可提供脑组织的病生理状态、判定缺血半暗带的存在、溶栓可能性的评估手段。

Objective To investigate the Characterization of DWI and PWI during ischemia and reperfusion and their value in the assessment of penumbra in ischemic rats. Methods 70 SD rats were randomly divided into three groups, group A （n=10） was sham-operated for control study, group B, C（n=30 for each） experience the occlusion and reperfusion of the right middle cerebral artery with thread. DWI, PWI were performed at B（I2h/R2h, 12h/R24h）and C（I6h/R2h, 16h/R24h） respectively. NEI topographical maps were achieved through reconstruction of raw data of DWI and PWI at workstation. The ratios of NEI （relative value to the contralateral side） were measured at areas of ischemic core and border area. Results Rats in group A had no change on DWI and PWI, hyper-intensity was found on DW I in group B. RNEI map in group B showed recovery of perfusion after reperfusion. The recovery of perfusion in group C showed more inadequacy and more uneven, and perfusion deficit still can be seen in the lesion. Conclusion Semi-quantitative parameters of DWI and PWI can distinguish the penumbra from ischemic necrosis. DWI can reflect the changes of the ischemic lesion, while PWI can monitor changes of blood dynamics following ischemia and reperfusion.