Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China.
PLoS One. 2012;7(7):e41441. doi: 10.1371/journal.pone.0041441. Epub 2012 Jul 19.
Although diffusion tensor imaging has been used to monitor Wallerian degeneration, the exact relationship between the evolution of diffusion indices and its underlying pathology, especially in central nervous system, remains largely unknown. Here we aimed to address this question using a cat Wallerian degeneration model of corticospinal tract.
METHODOLOGY/PRINCIPAL FINDINGS: Twenty-five domestic mature Felis catus were included in the present study. The evolution of diffusion indices, including mean diffusivity (MD), fractional anisotropy (FA), primary (λ1) and transverse eigenvalues (λ23) of the degenerated corticospinal tract, were observed at baseline (before modeling) and at 2, 4, 6, 8, 10, 15, 20, 25, 30, 45 and 60 days after modeling in 4 cats. Pathological examinations were performed at eight time points mentioned above. Wallerian degeneration can be detected as early as the 2nd day after modeling by both diffusion tensor imaging and pathology. According to the evolution of diffusion indices, Wallerian degeneration can be classified into 2 stages. During the early stage (within 8 days after modeling), progressive disintegration of axons and myelin sheaths underlies the decreases in FA and λ1 and the increase in λ23. However, during the late stage (after 8 days), the gradual increases in FA, MD and λ1 and the unchanged λ23 seem to be a comprehensive reflection of the pathological processes including microglia activation, myelin clearance, and astrocytosis.
CONCLUSIONS/SIGNIFICANCE: Our findings help the understanding of the altered diffusion indices in the context of pathology and suggest that diffusion tensor imaging has the potential to monitor the processes of Wallerian degeneration in the central nervous system in vivo after acute damage.
尽管弥散张量成像已被用于监测沃勒氏变性，但弥散指数的演变与其潜在的病理学之间的确切关系，特别是在中枢神经系统中，仍然知之甚少。在这里，我们使用猫皮质脊髓束沃勒氏变性模型来解决这个问题。
方法/主要发现：本研究纳入了 25 只国内成熟的家猫。在建模前（基线）和建模后第 2、4、6、8、10、15、20、25、30、45 和 60 天，在 4 只猫中观察了退化皮质脊髓束的弥散指数演变，包括平均弥散度（MD）、各向异性分数（FA）、主（λ1）和横向特征值（λ23）。在上述 8 个时间点进行了病理检查。弥散张量成像和病理学检查均可在建模后第 2 天检测到沃勒氏变性。根据弥散指数的演变，沃勒氏变性可分为 2 个阶段。在早期（建模后 8 天内），轴突和髓鞘的渐进性解体导致 FA 和 λ1 的降低以及 λ23 的增加。然而，在晚期（8 天后），FA、MD 和 λ1 的逐渐增加而 λ23 不变似乎是小胶质细胞激活、髓鞘清除和星形胶质细胞增生等病理过程的综合反映。
结论/意义：我们的研究结果有助于理解病理背景下改变的弥散指数，并表明弥散张量成像有可能在中枢神经系统急性损伤后活体监测沃勒氏变性过程。
