ESTRO 2025 - Abstract Book

S3151

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

References: [1] Bäumer, C et al. “Can a ToF-PET photon attenuation reconstruction test stopping-power estimations in proton therapy? A phantom study.” Physics in Medicine and Biology vol. 66,21 10.1088/1361-6560/ac27b5. (2021), doi:10.1088/1361-6560/ac27b5 [2] Rezaei, A et al. “Simultaneous reconstruction of activity and attenuation in time-of-flight PET.” IEEE transactions on medical imaging vol. 31,12 (2012): 2224-33. doi:10.1109/TMI.2012.2212719

2686

Digital Poster Assessment of the impact of rectal volume change on cumulative dose using AI tools Pawel Czajkowski 1 , Michał Posiewnik 2 1 Medical Physics Department, Oncology Center, Gdynia, Poland. 2 Medical Physics, Oncology Center, Gdynia, Poland Purpose/Objective: The aim of the study is to progressively evaluate the impact of filling the rectum during prostate radiotherapy with the CHHiP regiment using auto-contouring tools. Material/Methods: The study was conducted in a progressive manner based on data from 50 patients who underwent external beam irradiation of prostate cancer. Automatic contouring and cumulative dose calculations were performed using MIM Software, while the implementation of treatment plans was performed in the TPS Aria. In each patient, CBCT imaging was performed during the first 5 treatment fractions and the patient was positioned for markers placed inside the prostate. The acquired images were then imported into MIM Software, and a cumulative dose simulation was calculated using deformation registration of medical images. A cumulative dose analysis was performed between the 5th and 6th fraction, and then a decision was made about possible replanning.

Results: The analysis was based on results for 50 patients. First, we examined the size of the change in the volume of the bladder and rectum during irradiation of prostate cancer. Graphs show the median values for the change in volume of both the urinary bladder and rectum.