Abstract
PurposeNumerous brain MR imaging studies have been performed to understand radiation-induced cognitive decline. However, many of them focus on a single region of interest, e.g. cerebral cortex or hippocampus. In this study, we use deformation-based morphometry (DBM) and voxel-based morphometry (VBM) to measure the morphological changes in patients receiving fractionated photon RT, and relate these to the dose. Additionally, we study tissue specific volume changes in white matter (WM), grey matter (GM), cerebrospinal fluid and total intracranial volume (TIV). Methods and materialsFrom our database, we selected 28 patients with MRI of high quality available at baseline and 1 year after RT. Scans were rigidly registered to each other, and to the planning CT and dose file. We used DBM to study non-tissue-specific volumetric changes, and VBM to study volume loss in grey matter. Observed changes were then related to the applied radiation dose (in EQD2). Additionally, brain tissue was segmented into WM, GM and cerebrospinal fluid, and changes in these volumes and TIV were tested. ResultsPerforming DBM resulted in clusters of dose-dependent volume loss 1 year after RT seen throughout the brain. Both WM and GM were affected; within the latter both cerebral cortex and subcortical nuclei show volume loss. Volume loss rates ranging from 5.3 to 15.3%/30 Gy were seen in the cerebral cortical regions in which more than 40% of voxels were affected. In VBM, similar loss rates were seen in the cortex and nuclei. The total volume of WM and GM significantly decreased with rates of 5.8% and 2.1%, while TIV remained unchanged as expected. ConclusionsRadiotherapy is associated with dose-dependent intracranial morphological changes throughout the entire brain. Therefore, we will consider to revise sparing of organs at risk based on future cognitive and neurofunctional data.
Highlights
Radiation-induced brain injury is a phenomenon experienced after radiotherapy (RT) for brain tumors [1,2]
Anatomical and functional changes can lead to cognitive impairments, ranging from mild symp toms to severe dementia-like states, and occur in 50–90% of cases [1,2]
All patients were treated with volumetric modulated arc therapy (VMAT)
Summary
Radiation-induced brain injury is a phenomenon experienced after radiotherapy (RT) for brain tumors [1,2]. Anatomical and functional changes can lead to cognitive impairments, ranging from mild symp toms to severe dementia-like states, and occur in 50–90% of cases [1,2]. This phenomenon is seen in patients receiving treatment for primary brain tumors, as well as those receiving whole-brain radiotherapy for brain metastases and prophylactic cranial radiotherapy. Changes of white matter (WM) [3], cerebral cortex [4,5,6,7], and subcortical grey matter (GM) structures [8,9,10] have already been linked to received dose in several studies These investigations have focused on specific parts or structures of the brain, which may limit the generalizability of the acquired knowledge. Techniques are available to analyze the brain in its entirety, in order to give a comprehensive estimation of the effect of RT on the brain
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