Study of the influence of ionizing radiation on the scattering properties of the brain white matter

Abstract

Radiation therapy is a vital part of combined treatment for brain neoplasms. In order to enhance treatment effectiveness during irradiation, ionizing radiation is used to expose both the tumor and nearby tissues. This leads to pathological changes within the surrounding brain tissues, particularly affecting the white matter [1]. This can create challenges when attempting to differentiate between tumor and normal brain tissues during surgical resection, ultimately resulting in potential postoperative complications. Therefore, the development of novel techniques for identifying white matter alterations caused by radiation therapy during surgical procedures is required. The aim of this study was to examine the impact of ionizing radiation on the scattering characteristics of the brain’s white matter and assess the feasibility of using optical coherence tomography (OCT) to identify potential changes. The study analyzed ex vivo rat brain samples, examining a control group and a group exposed to ionizing radiation at a 15 Gy dose to the right hemisphere. Subsequently, the animals were euthanized at seven different times throughout the study (2–14 weeks). An OCT study and an immunohistochemical study of the frontal sections of the brain followed. The attenuation coefficient was calculated and en-face color-coded optical maps were constructed to quantitatively process OCT data. The corpus callosum was selected as the region of interest. As a result of the study, acute changes in the white matter were observed 2 weeks after irradiation, along with early delayed changes occurring at 6 and 12 weeks post-irradiation. These changes were characterized by reversible edema of the corpus callosum. Two weeks after irradiation, a moderate edema only occurred in the irradiated hemisphere. However, at 6 and 12 weeks, edema was also present in the contralateral hemisphere, with significant severity, indicating the spread of the process along myelinated nerve fibers. The analysis of OCT data showed changes in the attenuation coefficient values. We observed statistically significant reductions in the attenuation coefficient values at all time points with edema of the corpus callosum in different brain hemispheres compared to the control group (p 0.05). During this study, the corpus callosum demonstrated structural changes from ionizing radiation exposure. These changes were identified by a reduction in its scattering properties, which can be observed using OCT.