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目的对急性脑静脉闭塞模型进行磁共振扩散张量成像(DTI),观察脑实质损害的扩散规律及脑白质纤维束的完整性。材料与方法取家猫30只随机分为手术组(n=24)和假手术组(n=6)。手术组制备急性脑静脉闭塞动物模型,假手术组仅行开颅上矢状窦暴露。术后采用常规MRI和DTI对各组模型脑实质损害病灶进行连续动态观察,测量病变区的平均扩散系数(ADCav)和各向异性分数(FA)值,计算病变区与健侧区的ADCav、FA比值,用纤维示踪技术(FT)显示脑白质纤维束的完整性,并与病理学对照。结果手术组24只猫,9只常规MRI检查为阴性;15只猫脑实质出现异常信号,术后1 h ADCav值较健侧降低,3 h后ADCav值较健侧逐渐增高,12 h后增高明显。FA值于术后各时间点均降低。各时间点病变区与健侧ADCav、FA值差异有统计学意义(P<0.05)。各时间点ADCav、FA比值差异有统计学意义(F值分别为62.07、9.37,P<0.05)。术后1 h,FT显示脑白质纤维束移位和穿过病灶区,6 h后脑白质纤维束断裂、破坏,12 h后脑白质纤维束于病灶边缘处中断。术后1 h病灶区出现细胞毒性脑水肿,3 h后以血管源性水肿为主,12 h后出现静脉性脑梗死、脑出血。假手术组未见上述异常表现。结论DTI能清楚显示并定量判断急性脑静脉闭塞脑实质损害的动态变化规律,FT能更好地显示脑白质纤维束的受损和移位。
Objective To investigate the diffusion rules of cerebral parenchymal damage and the integrity of white matter fiber bundles by magnetic resonance diffusion tensor imaging (DTI) in acute cerebral venous occlusion model. Materials and Methods 30 domestic cats were randomly divided into operation group (n = 24) and sham operation group (n = 6). The animal model of acute cerebral venous occlusion was prepared in the operation group, while the sagittal sinus was exposed in the sham operation group. The postoperative MRI and DTI were used to observe the lesions of brain parenchyma in each group continuously. The mean ADC (ADCav) and anisotropic fraction (FA) were measured. The ADCav, FA ratio, the integrity of the white matter fiber bundle was demonstrated by fiber tracing technique (FT) and compared with pathology. Results In the operation group, 24 cats and 9 normal MRI were negative. Fifteen cats had abnormal signal in brain parenchyma, ADCav value decreased 1 h after operation, ADCav value gradually increased after 3 h, and increased after 12 h obvious. FA values decreased at all time points after surgery. At each time point lesion and contralateral ADCav, FA values were significantly different (P <0.05). ADCav, FA ratio at each time point had statistical significance (F value was 62.07,9.37, P <0.05). At 1 h after FT, FT showed the translocation of the white matter and traversing the lesion area. After 6 h, the white matter fiber bundle ruptured and ruptured. After 12 h, the white matter fiber bundle was interrupted at the edge of the lesion. Cytotoxic brain edema occurred in the focal lesion area 1 h after operation, followed by vasogenic edema at 3 h. Venous cerebral infarction and cerebral hemorrhage occurred 12 h later. Sham-operated group showed no abnormalities. Conclusion DTI can clearly show and quantitatively determine the dynamic changes of cerebral parenchymal lesions in patients with acute cerebral venous occlusion. FT can better show the damage and displacement of white matter.