Evaluating radiation-induced white matter changes in patients treated with stereotactic radiosurgery using diffusion tensor imaging: A pilot study

Stereotactic radiosurgery (SRS) has been an effective treatment method for brain tumors; however, few data are available regarding radiation-induced white matter (WM) damage by SRS. In this work, diffusion tensor imaging (DTI) was used to investigate WM changes following SRS. Fifteen patients with gliomas were enrolled, with prescription doses ranging 18-25 Gy. Patients were scanned with magnetic resonance imaging (MRI) including DTI before and after SRS. Diffusion tensors were calculated and fiber tracking was performed. Non-irradiated WM volumes and irradiated WM volumes receiving ≥12 Gy and ≥5 Gy were contoured as volumes of interest (VOI). Apparent diffusion coefficient (<D>), fractional anisotropy (FA) and number of fibers (NF) were calculated and assessed using the Wilcoxon signed-rank test. Compared with those of non-irradiated VOIs, FA and NF decreased considerably after two months of SRS in the irradiated WM VOIs. The variation in <D> was however small and was not statistically significant. The preliminary results suggested that FA and NF might potentially be more sensitive indicators than <D> in measuring radiation-induced WM changes and DTI could be a valuable tool to assess radiation-induced WM changes in SRS. Although it is still preliminary, this pilot study may be useful to provide insights for future studies.