DWI、ADC图对急性脑梗塞诊断的应用及病理生理基础

目的:探讨磁共振弥散加权成像(DW-MRI)及表观弥散系数图(ADC mapping)在急性脑梗塞诊断中的应用价值及病理生理基础。方法:应用单次激发平面回波三向同性弥散加权MRI和常规MRI对21例脑梗塞患者进行检查。其中超急性期8例,急性期13例,测定病灶平均表观弥散系数(ADC)值、相对表现弥散系数(rADC)及中心边缘ADC值。结果:超急性期8例均在DWI及ADC图上显示出缺血灶,但其在CT及T₂WI上表现正常。超急性、急性期脑梗塞在DWI上表现为高信号,其ADC值明显低于对侧相应区域,平均ADC值为(0.698±0.104)×10^-3mm²/s vs(0.990±0.161)×10^-3mm²/s(P<0.01),21例超急性、急性期病灶ADC值出现梯度征。结论:三向同性DWI及ADC图对急性脑梗塞,尤其是超急性脑梗塞较常规MRI及CT具有更高的敏感性,能快速、准确地诊断超急性、急性脑硬塞,并能反映缺血半暗带等相应的病理生理变化。

The application of DWI and ADC mapping in acute cerebral infarction and basis of pathophysiology

AIM:To study the roles of isotropic diffusion weighted imaging(DWI)and apparent diffusion coeficient(ADC)mapping in diagnosing early cerebral infarction.METHODS:21 patients with cerebral in farction (8hyperacute,13 acute)were imaged with both convent ional MRI and single-shot echo-planar isotropic diffusion weighted imaging.Among them 12 pat ients had CT scanning simultaneously within 24 hours after onset.The positive rate of early in farction was comparted on CT,T₂WI and DEI.The change of the infarct lesion in DWI and T₂WI was also analysed.The av erage ADC,relat ive ADC(rADC)and the ADC from center to periphery of the lesion were calculated.RESULTS:8 hypera cute cerebral ischemic regions were revealed at DWI and ADC mapping,but CT and conventional MR were not.Hyperacute and acute infarcts appeared as areas of hyperintensity on DWI,and their average ADC was significantly depressed comparted with homologous contralateral tissue(0.698±0.104)×10^-3mm²/s vs(0.990±0.161)×10^-3mm²/s(P<0.01).ADC value in 21 hypera cute had gradient sign.CONCLUSION:Isotropic diffusion weighted imaging and ADC mapping have greater senstitivity for acute and hyperacute cerebral infarction than conventional MRI and CT,and may be used to defined the core and penumbra of ischemic lesion.