MRI及DTI评估大鼠血管性认知障碍

目的 探讨早期诊断血管性认知障碍（VCI）的影像学指标。方法 将30只SD大鼠分为模型组（20只）和对照组（10只），对模型组采用改良四血管法建立VCI大鼠模型，对照组行假手术处理，通过Morris水迷宫检测大鼠认知功能变化。于建模后2周、1个月、3个月、5个月对2组大鼠行MR T2W和DTI扫描，利用手动分割ROI的方法分析海马体积及FA值变化；利用基于体素分析方法（VBA）分析大鼠FA值下降的脑区。最后处死大鼠，取脑组织切片进行HE和尼氏染色，观察海马区神经细胞受损情况。结果 模型组大鼠的学习和记忆能力较对照组降低。与对照组相比，模型组大鼠术后3、5个月海马体积萎缩，且海马区FA值明显减低（P均<0.05）。VBA分析结果显示，建模后1、3、5个月多处脑区FA值显著下降，且下降区域范围随时间延长逐渐扩大。病理结果显示，海马区锥体细胞排列紊乱、结构模糊，尼氏小体溶解、消失。结论 观察大鼠海马体积以及微观白质变化有助于早期诊断VCI；大脑FA值可作为早期诊断VCI以及评估严重程度的观察指标。

MRI and DTI in evaluation on vascular cognitive impairment of rat models

Objective To explore the imaging indexes of early diagnosis of vascular cognitive impairment (VCI). Methods Totally 30 rats were collected and divided into model group (n=20) and control group (n=10). Modified 4-VO method was used to establish the VCI rat models. Morris water maze test was used to detect learning and memory abilities of rats. T2W and DTI scanning were performed in all rats 2 weeks, 1 month, 3 months and 5 months after operation, respectively. ROI was used to analyze the change of hippocampal volume and FA value. Voxel-based analysis (VBA) was used to analyze the change of FA value in all brain on DTI images. Then the rats were sacrificed, HE staining and Nissl staining of brain tissue slices were performed to observe the morphological changes. Results Compared with control group, the learning and memory ability of rats in model group decreased significantly. Compared with the control group, the hippocampal volume and FA value in model group decreased significantly at 3 months and 5 months after operation, respectively (all P<0.05). FA in many brain areas reduced 1, 3, 5 months after operation in model group (all P<0.05), and the decrease regions expanded with time going. Pyramidal cells in the hippocampal showed degeneration and nuclear condensation, and cytoplasmic Nissl bodies demonstrated reduction and disappearance gradually. Conclusion Changes of rat hippocampal volume and microscopic white matter may be helpful to early diagnosis of VCI. Decrease of FA value can be used as an indicator for early diagnosis and severity evaluation of VCI.