DWI检测超急性期兔大脑中动脉梗死模型神经血管单元损伤的初步研究

目的　评价磁共振弥散加权成像（diffused weighted imaging, DWI）对兔脑超急性期脑梗死模型中神经血管单元（neurovascular unit , NVU）损伤的诊断价值。 方法　15只健康新西兰大白兔，随机分为对照组（5只）和实验组（10只）。 其中实验组用微导丝超选择性栓塞法制作兔大脑中动脉阻塞(middle cerebral artery occlusion, MCAO)模型，并根据存活时间分为0.5 h和4 h组。所有动物行磁共振DWI扫描和T2-flair扫描并分析表观弥散系数（apparent diffusion coefficient，ADC）和相对表观弥散系数（relative apparent diffusion coefficient，rADC），之后立即取全脑固定，切片进行尼氏染色、GFAP（glial fibrillary acidic protein， 星形胶质细胞标记物）和CD31（血管内皮标记物）染色。 结果　和对照组相比， 0.5 h组缺血区DWI成像见高信号，ADC成像见低信号，T2-Flair成像未见异常信号，尼氏染色未见异常，GFAP染色表达增加；4h组缺血区DWI成像见高信号，ADC成像见低信号，二者成像范围和强度较0.5h组扩大增强，T2-Flair成像见高信号，尼氏染色见尼氏体数目显著减少，GFAP染色表达较0.5h组显著增加。与0.5h组比，4h组缺血区的ADC值及rADC值均有显著差异（P<0.01）。实验组rADC值与GFAP荧光强度值呈负直线相关关系（r=－0.672，P<0.001）。 结论　DWI对超急性期兔脑梗死可以及时准确的进行诊断，对应时间点梗死模型的NVU损伤特点符合影像学特征。

The preliminary research on neurovascular unit injury of hyperacute infarction of rabbit middle cerebral artery by magnetic resonance diffusion-weighted imaging

Objective　To investigate the diagnostic efficacy of magnetic resonance diffusion-weighted imaging (DWI) on the injury characteristics of neurovascular unit (NVU) of hyperacute infarction of rabbit brain.　Methods　Fifteen New Zealand rabbits were randomly separated into two groups: the contrast group (n=5) and the experimental group (n=10). Micro-catheter was used to produce middle cerebral artery occlusion (MCAO) on the experimental group animals via internal carotid artery. According to different occlusion time, the experimental group was divided into 2 sub-groups (sub-group 0.5 h and 4 h) with 5 animals per group. All the animals underwent T2-flair and DWI scanning before and after MCAO. The imaging characteristics of DWI and the values of apparent diffusion coefficient (ADC) and relative apparent diffusion coefficient (rADC) were analyzed. After MRI, the animals were sacrificed for the Nissl′s staining, the glial fibrillary acidic protein (GFAP) and CD31 detection of brains.　Results　Compared with the contrast group, abnormal high intensity signal on DWI, low signal on ADC, unaltered T2-flair signal, high expression of GFAP were observed at sub-group 0.5 h in the right basal ganglia region. At sub-group 4 h, abnormal high intensity signal on DWI and low signal on ADC which appeared more intense than sub-group 0.5 h. T2-flair scanning showed high signal. The Nissl’s results showed that the number of Nissl’s body at the control group and sub-group 0.5 h appeared intact, while the number of Nissl’s body decreased and neurons were damaged at sub-group 4 h. The high expression of GFAP were observed. The values of ADC and rADC in sub-group 0.5 h were significantly different with those in sub-group 4 h. The value of rADC and the intensity of GFAP showed linear correlation (r=-0.672, P<0.01).　Conclusions　The DWI can diagnose accurately on hyperacute infarction of rabbit brain, and the DWI changes of relative time were consistent with the injury of NVU.