ESTRO 2025 - Abstract Book

S3326

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Results: The median time between pre- and verification CBCTs was 25min. Residual errors are shown in Table 1. Noteworthy are the ∑translations and rotations for lymph nodes, which are reduced by half. For the prostate specifically, the ∑R LR is reduced, from 2.4 to 1.2 degrees. Two out of 19 patients still had a relatively large >0.25mm ∑residual lymph nodes error after adaptations, caused by intra-fraction prostate motion. Evaluation of verification and post-treatment CBCT differences reveal little motion during beam delivery for the lymph node regions, but a larger random motion for the prostate (Table 1). Possible margin reductions for lymph node regions were 2.0mm LR, 1.6mm CC and 2.4mm AP, and for prostate 0.1mm LR, 0.9mm CC and 1.0mm AP.