ESTRO 2025 - Abstract Book

S2513

Physics - Autosegmentation

ESTRO 2025

Results: The vertebral segmentation network achieved Dice Similarity Coefficients above 0.8 and mean surface distance below 3.5 ± 0.8 mm for test cases. Manual verification of landmarks confirmed their accuracy. The Wilcoxon test revealed significant differences between CT and MR measurements of the same vertebrae, with paired mean differences ranging from 2.0 mm at T3 to 3.9 mm at L1 (Figure 2). These differences can be attributed to the hypointense appearance of cortical bone on SE T2w-MR images due to low proton density and rapid signal decay [1,2]. Differences are consistent with observable cortical bone thickness, which is difficult to measure due to CT voxel averaging [3]. Spatial resolution differences between CT and MR further contribute to differences, particularly when assessing small structures like paediatric vertebrae.