ESTRO 2021 Abstract Book

S468

ESTRO 2021

readout of 3D dosimeters. The quality of 3-D readout from this optical scanner is comparable or better than the single-beam raster scanning system, but with a scanning time of 10 minutes or less.

Poster highlights: Poster Highlights 23: CNS 2

PH-0602 Effect of radiation therapy on cerebral cortical thickness in glioma patients J. Kallehauge 1 , C.S. Byskov 2 , L. Haldbo-Classen 2 , A. Harbøll 3 , S. Lukacova 2

1 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus , Denmark; 2 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 3 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark Purpose or Objective One of the side effects of radiation therapy (RT) is thinning of the cerebral cortex, which may contribute to cognitive impairment. In this study, we assessed the effect of RT on the thickness of the cerebral cortex in the supramarginal, inferior parietal, superior parietal, superior temporal, posterior cingulate, paracentral and lateral orbitofrontal regions. These regions have previously been found susceptible to dose-dependent Six adult lower grade glioma patients were included in this study. Clinical CTs and MRIs were collected and co- registered before RT and one year post-RT. The scans were processed via an automated image processing pipeline (CAT12 v1742), that enables measuring changes of the cortical thickness (figure 1B), which were subsequently related to local dose (figure 1A). Cortical parcellations were performed according to the Desikan-Killiany atlas (figure 1C+D). Changes in supramarginal, inferior parietal, superior parietal, superior temporal, posterior cingulate, paracentral and lateral orbitofrontal regions cortical thicknesses were correlated to local dose. Pooled data for corresponding left and right structures were used for the analysis. Spearmans' correlation was used to test for significant dependence between change in thickness and radiation dose. P-value <0.05 was considered significant. Bonferroni correction was applied for multiple testing (N=7). cortical thinning [1,2]. Materials and Methods

Results The mean changes in cortical thickness and corresponding dose in the supramarginal region were 0.04±0.05 mm and 16.9±17.0Gy, respectively. In the inferior parietal region, the values were 0.02±0.03 mm and 11.2±11.5Gy. In the superior parietal region, the values were 0.02±0.04 mm and 14.9±15.9Gy. In the superior temporal region, the values were 0.01±0.06 mm and 11.9±11.6Gy. In the posterior cingulate region, the values were -0.06±0.11 mm and 31.9±21.4Gy. In the paracentral region, the values were -0.02±0.07 mm and 26.3±24.6Gy. In the lateral orbitofrontal region, the values were 0.04±0.06 mm and 23.1±17.6Gy. Only the posterior cingulate region showed significant correlation between cortical thinning and local dose with a Spearmans' correlation coefficient of ρ=-0.93 (figure 2).