Department of Radiation Medicine, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA.
Radiat Res. 2010 Jun;173(6):729-37. doi: 10.1667/RR1832.1.
56Fe-particle radiation-induced brain disturbances are a major health concern for astronauts during long-term space travel. The present study investigated temporal modifications within the brain after 56Fe-particle exposure using in vivo magnetic resonance imaging (MRI) correlated to histology. Male Sprague-Dawley rats were exposed to brain-only 56Fe-particle radiation. MRI including T2-weighted, diffusion-weighted, pre/postcontrast enhanced T1-weighted imaging was performed 0.25-18 months after exposure. T2 relaxation times and the apparent diffusion coefficient were quantified within the hippocampus, entorhinal cortex, retrosplenial cortex and thalamus, and correlative histopathology was then performed at each time. In the absence of visible lesions on MR images, the apparent diffusion coefficient and T2 relaxation times revealed 56Fe-particle-induced dynamic changes in all ROIs over the 18-month time course. The patterns of MR changes were spatially similar within the different regions. The temporal alterations in the apparent diffusion coefficient corresponded to the glial cell changes within the brain. Quantitative MRI provides a non-invasive approach to monitor spatio-temporal brain alterations after 56Fe-particle irradiation. The apparent diffusion coefficient appears to be a sensitive metric to reveal ongoing tissue modifications involving multiple cellular components in vivo.
56Fe 粒子辐射诱导的脑损伤是宇航员在长期太空旅行中面临的主要健康问题。本研究通过与组织学相关的活体磁共振成像 (MRI) 研究了 56Fe 粒子照射后大脑内的时间变化。雄性 Sprague-Dawley 大鼠仅接受脑部 56Fe 粒子照射。暴露后 0.25-18 个月进行包括 T2 加权、弥散加权、对比前/后增强 T1 加权成像的 MRI 检查。在海马体、内嗅皮层、后扣带回皮层和丘脑内定量 T2 弛豫时间和表观弥散系数，并在每个时间点进行相关的组织病理学检查。在 MR 图像上未见可见病变的情况下，在 18 个月的时间过程中，所有 ROI 中的表观弥散系数和 T2 弛豫时间均显示出 56Fe 粒子诱导的动态变化。不同区域内的 MR 变化模式在空间上相似。表观弥散系数的时间变化与脑内神经胶质细胞的变化相对应。定量 MRI 提供了一种非侵入性的方法来监测 56Fe 粒子照射后时空大脑变化。表观弥散系数似乎是一种敏感的指标，可以在体内揭示涉及多个细胞成分的持续组织变化。
