7.0T磁共振扩散张量成像在实验性自身免疫性脑脊髓炎大脑皮层及胼胝体病变中的应用

Diffusion Tensor Imaging of 7.0T Magnetic Resonance on Cerebral Cortex and Corpus Callosum Lesions in Experimental Autoimmune Encephalomyelitis

目的大脑白质是多发性硬化(MS)的常见发病部位,MS皮层及胼胝体病变逐渐受到关注。本文使用7.0T磁共振扩散张量成像(DTI)技术,以实验性自身免疫性脑脊髓炎(EAE)模型研究MS大脑皮层病变及胼胝体病变。材料与方法实验准备SPF级6~8周龄健康雌性C57BL/6小鼠20只,其中MOG_(35-55)诱导制备实验组10只、健康对照组10只。造模后20 d,对实验组和对照组行头颅T2WI和DTI扫描,比较两组感兴趣区(双侧前额皮层、双侧扣带回、胼胝体)的DTI量化指标各向异性分数(FA)、平均扩散率(MD)、轴向扩散系数λ_∥、径向扩散系数λ_⊥的差异。结果两组T2WI均未发现明显病变。实验组FA图显示的胼胝体左侧完整性受到破坏。实验组双侧前额皮层FA、MD、λ_∥、λ_⊥与对照组比较差异均有统计学意义(P<0.05);胼胝体FA、MD、λ_∥、λ_⊥与对照组比较,差异有统计学意义(P<0.05);双侧扣带回λ_⊥的升高较对照组差异有统计学意义(P<0.05)。HE染色结果显示,实验组皮层及皮层下血管周围有炎症细胞聚集。LFB染色显示实验组染色较对照组浅淡,胼胝体呈斑片状髓鞘脱失。结论 7.0T磁共振DTI能够检测常规MRI序列不能发现的皮层及胼胝体病变,可以为研究MS皮层及胼胝体病变提供影像证据。

Purpose Cortex is one of the frequently involved sites of multiple sclerosis（MS）, and the cortex and corpus callosum lesions of MS are gradually concerned. The study aims to observe the changes of cerebral cortex and corpus callosum of MS in experimental autoimmune encephalomyelitis（EAE） model by using 7.0T MRI diffusion tensor imaging（DTI）. Materials and Methods Twenty female C57BL/6 mice of 6-8 week old were enrolled in the study, 10 of which were induced by MOG（35-55） to make EAE models and the rest 10 of which were taken as control group. On the 20 days after model establishment, the head T2WI and DTI were performed on both control and EAE mice. DTI quantitative indicators such as fractional anisotropy（FA）, mean diffusivity（MD）, axial dispersion coefficient λ∥, and radial dispersion coefficient λ⊥ in region of interest including bilateral prefrontal cortex, bilateral cingulate cortex and corpus callosum were compared between the two groups. Results No obvious lesions were observed on the T2WI in both control and EAE groups. In the experimental group, the FA mapping suggested the integrity of the left side of the corpus callosum was destroyed. The FA, MD, λ∥, λ⊥ of bilateral prefrontal cortex and corpus callosum showed significant difference between experimental group and control group（P〈0.05）; the increase of λ⊥ in bilateral cingulate was significantly different from that in the control group. Meanwhile, HE staining in the experimental group showed that inflammatory cells gathered around the cortical and subcortical vessels. The LFB staining in experimental group showed a bit paler than that in the control group, and the corpus callosum showed patchy demyelination. Conclusion The technique of 7.0T MRI DTI sequence can detect cortex and corpus callosum lesions which cannot be found by conventional MRI, so that it provides radiological evidence for the study of MS with cortex and corpus callosum lesions.