【作者】 刘红军；

【导师】 梁长虹；

【作者基本信息】 南方医科大学 ， 影像医学与核医学， 2009， 博士

【摘要】 目的:1.初步探讨磁敏感加权成像在大鼠超急性脑缺血中的价值。2.对比磁敏感加权成像与灌注加权成像在大鼠超急性脑缺血中的应用,评价磁敏感加权成像对缺血半暗带的检测作用。3.应用磁敏感加权成像评价慢性大脑中动脉狭窄或闭塞患者的脑氧代谢。4.联合应用磁敏感加权成像及弥散加权成像检测急性期脑梗死半暗带,探讨脑梗死缺血半暗带的存在规律。材料与方法:1.健康雄性Wistar大鼠40只,采用线栓法制备超急性期MCAO模型。模型制作成功后20分钟及2.5小时分别行SWI及DWI检查,经过后处理得到校正后相位图及ADC图,参照缺血2.5小时DWI及ADC图,分别测量梗死核心区、周围区及对侧镜像区的相位弧度值及SWI信号值,并比较不同兴趣区之间以及相同兴趣区两个时间点之间的相位弧度值及SWI信号值。2.健康雄性Wistar大鼠20只,MCAO模型制作成功后2.5小时分别行SWI、PWI及DWI检查,分别测量SWI异常信号区、SWI梗死核心相对正常信号区占同层全脑面积相对百分比,以及PWI灌注减低区、DWI高信号区占同层全脑面积相对百分比,并比较SWI异常信号区与PWI灌注减低区、SWI梗死核心相对正常信号区与DWI高信号区、SWI低信号区及PWI/DWI不匹配区的面积百分比。3.单侧大脑中动脉狭窄或重度闭塞患者11例及性别、年龄相匹配的健康对照组10例,分别行TOF-MRA及SWI检查,测量并比较患者病变侧、健侧以及对照组两侧脑组织的相位弧度值及SWI信号值。4.发病6-24小时的急性脑梗死患者20例,分别行SWI及DWI检查,参照DWI及ADC图,测量梗死核心周围区脑组织的相位弧度值及SWI信号值,确定SWI半暗带的存在情况。结果:1.大鼠大脑中动脉栓塞20分钟梗死核心区、核心周围区及对侧镜像区相位弧度平均值分别为-0.05060±0.03201,0.04508±0.0205l,-0.03791±0.01735,0.04315±0.01740,之间存在显著差异(F=164.341,P=0.000);SWI信号平均值分别为201.66±59.86,289.72±55.51,203.48±47.19,304.43±79.91,亦存在显著性差异(F=25.250,P=0.000);梗死核心区、核心周围区的相位弧度值及SWI信号值均低于对侧镜像区脑组织(P=0.000),但梗死核心区、核心周围区之间无显著性差异(P值分别为0.279,0.906)。栓塞2.5小时梗死核心区、核心周围区及对侧镜像区相位弧度平均值分别为0.04681±0.01689,0.04287±0.01906,-0.03866±0.01691,0.04596±0.01784,之间存在显著差异(F=180.038,P=0.000);SWI信号平均值分别为293.18±73.22,284.48±39.89,200.36±43.08,308.14±59.53,亦存在显著性差异(F=24.323,P=0.000);梗死核心周围区的相位弧度值及SWI信号值均低于梗死核心区及对侧镜像区脑组织(P=0.000),但梗死核心区与对侧镜像区脑组织之间无显著性差异(P>0.05)。2.大鼠大脑中动脉栓塞2.5小时PWI灌注减低区与SWI异常信号区面积百分比分别为35.75±9.44(%)、35.56±8.07(%),二者之间无显著性差异(t=0.226,P=0.824)。DWI高信号区与SWI梗死核心相对正常信号区面积百分比分别为29.15±8.57(%)、26.68±6.53(%),二者之间亦无显著性差异(t=2.007,P=0.062)。PWI灌注减低区与SWI异常信号区面积百分比之间相关性较强(Pearson相关系数为0.932,P=0.000);ADC减低区与SWI梗死核心相对正常信号区面积百分比之间亦具有明显的相关性(Pearson相关系数为0.807,P=0.000)。3.单侧大脑中动脉重度狭窄或闭塞患者病变侧、健侧、正常对照组左侧及右侧的相位弧度平均值分别为0.00600±0.00210,0.01166±0.00352,0.01208±0.00286,0.01051±0.00230(F=13.476,P=0.000).SWI信号平均值分别为194.29±28.08,238.33±24.76,245.05±8.76,233.06±11.66(F=13.360.P=0.000),均存在显著性差异。病变侧相位弧度值及SWI信号值均低于健侧及正常对照组(P<0.05)。4.20例脑梗死患者中基底节、丘脑区病灶6个,脑叶病灶14个,其中基底节、丘脑6病灶均未见存在SWI半暗带;脑叶病灶有5例出现SWI半暗带,其中直径<2.0 cm病灶2个,直径≥2.0 cm病灶3个,其发病时间依次为7、10、10、15、19小时。结论:1.SWI能在大鼠大脑中动脉栓塞20分钟即可显示脑缺血,表现为SWI信号及相位弧度值降低。随着缺血时间的延长,缺血核心区在SWI上又升高接近正常脑组织信号,预示不可逆梗死。2.SWI能间接反映超急性脑梗死缺血半暗带血流变化及代谢情况,可以代替MR灌注成像用于脑缺血半暗带的检测。3.SWI能间接反映慢性缺血脑组织OEF的升高及CBF的降低,可代替CT或MR灌注成像评价大脑中动脉狭窄或闭塞患者缺血范围及缺血程度,指导临床治疗。4.缺血半暗带没有严格的时间窗,其存在一定的个体差异,发病6-24小时的脑梗死患者中有仍有25%左右存在缺血半暗带。磁敏感加权成像联合弥散加权成像能敏感地检测到脑缺血半暗带,为临床实施个体化溶栓方案提供有力的影像学证据。更多还原

【Abstract】 Objectives:1.To investigate the value of susceptibility weighted imaging in the rat hyperacute cerebral ischemia.2.To compare the application of susceptibility weighted imaging and perfusion weighted imaging in the rat hyperacute cerebral ischemia,and to evaluate the usefulness of susceptibility weighted imaging in the detection of ischemic penumbra.3.To evaluate the brain oxygen metabolism in patients of chronic middle cerebral artery stenosis or occlusion with susceptibility weighted imaging.4.To detect the ischemic penumbra of acute cerebral infarction with susceptibility weighted imaging and diffusion weighted imaging,and to explore the existing duration of ischemic penumbra.Materials and Methods:1.40 male healthy Wistar rats were enrolled in this study.The rat model of middle cerebral artery occlusion(MCAO)was performed according to the intraluminal filament technique.Susceptibility weighted imaging and diffusion weighted imaging were performed at 20 minutes and 2.5 hours respectively after MCAO model was successfully accomplished,and corrected phase images and ADC map were acquired through postprocessing.According to the DWI and ADC map of 2.5 hours after occlusion,the phase radians and SWI signal intensity values of the infarction core,peri-core area,and counterparts in the contralateral hemisphere were measured respectively,the phase radians and SWI signal intensity values in different ROIs and same ROI in different times were compared.2.20 male healthy Wistar rats were enrolled in this study.Susceptibility weighted imaging,perfusion weighted imaging and diffusion weighted imaging were performed at 2.5 hours after MCAO model was successfully accomplished.The area percent of abnormal signal and the core showed relative normal signal on SWI,the hypoperfusion area percent on PWI and hyperintensity area percent on DWI versus the whole brain area in the same slice were measured respectively. Finally the area percent of abnormal signal on SWI and the hypoperfusion area percent on PWI,the area percent of the core showed relative normal signal on SWI and the hyperintensity area percent on DWI,the hypointensity area percent on SWI and PWI/DWI mismatch area percent were compared and correlated respectively.3.11 patients with severe unilateral middle cerebral artery(MCA)chronic stenosis or occlusion and 10 healthy controls with matched gender and age were performed TOF-MRA and susceptibility weighted imaging,the phase radians and SWI signal intensity values of lesion side,normal side of patients and the two sides of controls were measured and compared.4.20 patients with acute cerebral infarction within 6-24 hours after onset of clinical symptoms were underwent susceptibility weighted imaging and diffusion weighted imaging,according to the DWI and ADC map,the phase radians and SWI signal intensity values of brain tissue around the infarction core were measured,to identify the presence of ischemic penumbra.Results:1.20 minutes after occlusion of MCA in rats,the phase radians of the infarction core,the peri-core area,and the counterparts in the contralateral hemisphere were -0.05060±0.03201,0.04508±0.02051,-0.03791±0.01735,0.04315±0.01740 respectively,the difference was significant(F=164.341,P=0.000).and the SWI signal intensity values were 201.66±59.86,289.72±55.51,203.48±47.19, 304.43±79.91 respectively,the difference was also significant(F=25.250, P=0.000).The phase radians and SWI signal intensity values of the infarction core,the peri-core area were lower than that of the counterparts in the contralateral hemisphere(P=0.000),but the infarction core and the peri-core area had no significant difference(P values were 0.279,0.906 respectively).2.5 hours after occlusion of MCA,the phase radians of the infarction core,the peri-core area,and the counterparts in the contralateral hemisphere were 0.04681±0.01689,0.04287±0.01906,-0.03866±0.01691,0.04596±0.01784 respectively,the difference was significant(F=180.038,P=0.000).and the SWI signal intensity values were 293.18±73.22,284.48±39.89,200.36±43.08, 308.14±59.53 respectively,the difference was also significant(F=24.323, P=0.000).The phase radians and SWI signal intensity values of the peri-core area were lower than that of infarction core and counterparts in the contralateral hemisphere(P=0.000),but that of infarction core and counterparts in the contralateral hemisphere had no significant difference(P>0.05).2.2.5 hours after occlusion of MCA in rats,the hypoperfusion area percent on PWI and the area percent of abnormal signal on SWI were 35.75±9.44(%)、35.56±8.07(%)respectively,there was no significant difference(t=0.226,P=0.824). The hyperintensity area percent on DWI and the area percent of the core showed relative normal signal on SWI were 29.15±8.57(%)、26.68±6.53(%),there was also no significant difference(t=2.007,P=0.062).The area percent of abnormal signal on SWI and the hypoperfusion area percent on PWI were well correlated(Pearson correlate coefficient is 0.932,P=0.000).The hyperintensity area percent on DWI and the area percent of the core showed relative normal signal on SWI were also well correlated(Pearson correlate coefficient is 0.807, P=0.000).3.The phase radians of lesion side,normal side of patients and the two sides of controls were 0.00600±0.00210,0.01166±0.00352,0.01208±0.00286, 0.01051±0.00230(F=13.476,P=0.000),and the SWI signal intensity values were 194.29±28.08,238.33±24.76,245.05±8.76,233.06±11.66(F=13.360, P=0.000),the difference were all significant.The phase radians and SWI signal intensity values of lesion side were all lower than that of normal side and two sides of controls(P＜0.05).4.In the 20 patients with acute cerebral infarction,6 lesions located at basal ganglia and hypothalamus region,14 lesions located at lobes.All the 6 lesions located at basal ganglia and hypothalamus region had no SWI penumbra,while 5 lesions at lobes had SWI penumbra,2 of the 5 lesions were smaller than 2.0cm,and other 3 lesions were equal to or larger than 2.0cm,the time after onset of clinical symptoms were 7、10、10、15、19 hours respectively.Conclusions:1.SWI can detect cerebral ischemia in rat as early as 20 minutes after occlusion of MCA,which demonstrate as decrease of the signal on SWI and phase radian. With the development of the ischemia,the signal of the infarction core may increase to relative normal signal on SWI,which signify irreversible infarction.2.SWI can reflect the hemodynamics and metabolism of ischemic penumbra in hyperacute infarction inderectly,so may substitute for MR perfusion weighted imaging to detect cerebral ischemic penumbra.3.SWI can reflect the increase of OEF and decrease of CBF in chronic cerebral ischemia indirectly,may substitute for CT or MR perfusion to evaluate the cerebral ischemia volume and extent in patients with MCA stenosis or occlusion, and guide to make a therapeutic plan.4.There is no absolute time window of ischemic penumbra,it’s duration has individual differences.Ischemic penumbra can be detected in about 25%of patients with cerebral infarction within 6-24 hours after onset.SWI combined with DWI can detect ischemic penumbra sensitively and provide convincing imaging evidence for individual thrombolytic protocol.更多还原