摘要
目的探讨双指数衰减多b值模型的表观扩散系数(ADC)值对超急性期脑缺血大鼠的评价。方法首先,对14只SD大鼠用线栓法行单侧大脑中动脉闭塞(MCAO)的急性脑缺血手术。然后,分别在术后0.5、1.5、2、3和4 h行3.0T MRI检查,包括T_1WI和T_2WI、扩散加权成像(DWI)和体素内不均匀一运动(IVIM)序列;其中IVIM序列采用双指数模型,b值取0至4000之间递增的12个值,观察各时间点患侧及健侧皮层和基底节区的Mono-ADC值、Fast-ADC值和Slow-ADC值之间的差异。最后,病理TTC染色以明确脑组织的梗死部位及范围。结果皮层和基底节区的Mono-ADC值、Slow-ADC值均随时间而缓慢减低,但患侧和健侧之间差异无统计学意义(P>0.1);皮层和基底节区的Fast-ADC值随时间增加而显著减低,以术后0.5 h～1.5 h之间减低为著;术后早期(0.5 h)患侧Fast-ADC值高于健侧(P<0.05),术后晚期(4 h)患侧低于健侧(P<0.05)。结论双指数衰减中Fast-ADC值所表现出的特征性可能反映了多种b值扩散成像中的灌注因素,可能为活体超急性期缺血脑组织中的微循环变化提供有意义的参考。
Objective To assess the value of bi-exponential apparent diffusion coefficient of multi-b factors in super-acute cerebral ischemia of rats. Methods After unilateral middle cerebral artery ligation （MCAO） on fourteen SD rats, TI-, T2-, diffusion- weighted imaging （DWI） and intra-voxel incoherent motion （IVIM） MR Imaging were performed using a 3-T MRI system at 0.5 h, 1.5 h, 2 h, 3 h and 4 h. The IVIM sequence was applied using a bi- exponential model with 12 b factors between 0 and 4000. We compared the mono-ADCs, fast-ADCs and slow-ADCs of the bilateral cerebral cortex and basal ganglia. The rats were then sacrificed and the brain infarct size was measured using Trc stain. Results The reduction of mono-ADCs and slow-ADCs of the infarcted cerebral cortex and basal ganglia with time after MCAO was not statistically significant from that of the contralateral side （P 〉 0.1）. Fast-ADCs of the infarcted cortex and basal ganglia were significantly （P 〈 0.05） higher from those of the contralateral side at 0.5 h to 1.5 h and lower at 4 h later stage after MCAO. Conclusion Bi-exponential fast-ADC may be attributed to the perfusion effect in multi-b factor diffusion-weighted imaging and may reflect the microcirculation change of super-acute brain ischemia in vivo.
出处
《影像诊断与介入放射学》
2012年第1期61-66,共6页
Diagnostic Imaging & Interventional Radiology
