Whole-brain changes in white matter microstructure after radiotherapy for nasopharyngeal carcinoma: a diffusion tensor imaging study.

Radiation-induced local white matter (WM) damage has been observed by diffusion tensor imaging (DTI) within a priori-defined regions of interest following radiotherapy (RT) for nasopharyngeal carcinoma (NPC). In this study, we aimed to detect WM changes throughout the brain of NPC patients by DTI. Tract-based spatial statistics (TBSS) was used to analyze DTI data from 81 NPC patients. Fractional anisotropy (FA) and mean diffusivity (MD) were quantified across the whole brain in separate groups: pre-RT, and <6, 6-12, and >12 months post-RT. We found that fractional anisotropy values were significantly lower in the right frontal, parietal, and occipital WM <6 months post-RT compared with pre-RT and remained significantly lower in the right frontal and parietal WM at >12 months. MD values were significantly higher in the right occipital, bilateral temporal, right occipital-temporal junction, left parietal, left centrum semiovale, and left frontal-parietal junction WM <6 months post-RT and remained higher in the right occipital WM at >12 months. This study suggests that changes in white matter microstructure following RT for NPC were widespread, complex, and dynamic. Diffusion tensor imaging with TBSS analysis allows for early non-invasive detection of RT-induced WM damage.