Radiation therapy effects on white matter fiber tracts of the limbic circuit

Abstract

Purpose: To segment fiber tracts in the limbic circuit and to assess their sensitivity to radiation therapy (RT). Methods: Twelve patients with brain metastases who had received fractionated whole brain radiation therapy to 30 Gy or 37.5 Gy were included in the study. Diffusion weighted images were acquired pre-RT, at the end of RT, and 1-month post-RT. The fornix, corpus callosum, and cingulum were extracted from diffusion weighted images by combining fiber tracking and segmentation methods based upon characteristics of the fiber bundles. Cingulum was segmented by a seed-based tractography, fornix by a region of interests (ROI)-based tractography, and corpus callosum by a level-set segmentation algorithm. The radiation-induced longitudinal changes of diffusion indices of the structures were evaluated. Results: Significant decreases were observed in the fractional anisotropy of the posterior part of the cingulum, fornix, and corpus callosum from pre-RT to end of RT by -14.0%, -12.5%, and -5.2%, respectively (p < 0.001), and from pre-RT to 1-month post-RT by -11.9%, -12.8%, and -6.4%, respectively (p < 0.001). Moreover, significant increases were observed in the mean diffusivity of the corpus callosum and the posterior part of the cingulum from pre-RT to end of RT by 6.8% and 6.5%, respectively, and from pre-RT to 1-month post-RT by 8.5% and 6.3%, respectively. The increase in the radial diffusivity primarily contributed to the significant decrease in the fractional anisotropy, indicating that demyelination is the predominant radiation effect on the white matter structures. Conclusions: Our findings indicate that the fornix and the posterior part of the cingulum are significantly susceptible to radiation damage. We have developed robust computer-aided semiautomatic segmentation and fiber tracking tools to facilitate the ROI delineation of critical structures, which is important for assessment of radiation damage in a longitudinal fashion.

Effects of Surgery and Proton Therapy on Cerebral White Matter of Craniopharyngioma Patients

“…Short-term changes in FA indices after treatment have been reported in previous studies on adult patients with brain tumor treated by photon therapy (9,15,16,25). In contrast to our results, however, more severe and progressive changes were often observed.…”

“…Several studies have reported correlation between changes in DTI indices and decreased neurocognitive functionality such as intelligence quotient scores and processing speeds (11)(12)(13)(14), suggesting DTI as a potential imaging biomarker for treatmentrelated neurotoxicity. A notable finding in these studies is that radiation dose-effect is fiber tract-or region-dependent (15)(16)(17)(18). If an association with observed neurotoxicity can be established, then knowledge of differential radiation sensitivity would be valuable in treatment planning to protect more vulnerable brain regions.…”

Lateralization of temporal lobe epilepsy using a novel uncertainty analysis of MR diffusion in hippocampus, cingulum, and fornix, and hippocampal volume and FLAIR intensity

“…Using previously described segmentation and fiber tracking methods [34], the cingulum and its subregions were bilaterally segmented for both datasets. In brief, the cingulum was segmented using an automatic seed-based algorithm: 1.…”

Standard chemoradiation for glioblastoma results in progressive brain volume loss

“…[5][6][7] Recent studies have investigated the effects of chemotherapy and radiation on global and regional brain anatomy using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI). [8][9][10][11][12][13][14][15][16][17][18][19] While the design and results of these studies vary, they collectively suggest that CNS toxicity is associated with cancer therapy even for non-CNS malignancies, with widespread gray matter (GM) and white matter (WM) loss, and associated deficits in multiple cognitive domains. 15,16 Few studies, however, have examined the extended time course of these effects, and none has assessed longitudinal changes on MRI in patients receiving chemotherapy and cranial RT.…”