S2729
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
bladder volume where dose constraints are still met. Material/Methods: A script was used to create a structure, Help_Structure_Bladder, to represent the minimum acceptable bladder filling by reducing the bladder volume until the dose-volume-constraints are just barely passing. The volume was reduced iteratively by applying smaller and smaller expanding margins around the Planning Target Volume. The structure was created after plan approval for all prostate cancer patients receiving ultra hypo fractionated radiotherapy treatment (6.1 Gy x 7 Fx) during 2025. For patients receiving treatments during 2024, there was no Help_Structure_Bladder.
with SGRT workflows in all cases, without compromising surface acquisition or tracking accuracy. Its use in combination with SGRT improved patient setup reproducibility and reduced intrafractional motion compared with conventional workflows, with a single case requiring repeated setup and imaging. A slight increase in setup time was also observed relative to standard workflows. Conclusion: Preliminary results suggest that the Chabner XRT® Radiation Bra can be effectively integrated into SGRT workflows without compromising setup accuracy. The combination improves setup reproducibility while supporting its feasibility for routine clinical implementation. Continued data collection and long- term evaluation are needed to validate these findings and assess their impact on clinical outcomes. References: Chua JZ, Lim LH, Pang EPP, Kusumawidjaja G. Use of immobilisation bra for daily setup of patients with pendulous breasts undergoing radiotherapy. Strahlenther Onkol. 2023.Park SH, Choi J. Analysis of geometric and dosimetric effects of bra application to support large or pendulous breasts during radiotherapy planning: A retrospective single-center
study. Technol Cancer Res Treat. 2021;20:15330338211027909.
doi:10.1177/15330338211027909González-Sanchis A, Brualla-González L, Fuster-Diana C, Gordo-Partearroyo JC, Piñeiro-Vidal T, García-Hernández T, et al. Surface- guided radiation therapy for breast cancer: more precise positioning. Radiother Oncol. 2021;160:165- 170. doi:10.1016/j.radonc.2021.05.037 Keywords: Immobilisation, setup reproducibility, workflow
During 2024 and 2025, every fraction where RTTs needed physician support during on-line anatomy assessment was documented, as well as every instance of off-line image review by physicians. Results: During 2024, RTTs required no support from physicians during on-line image assessment for 33 % of patients (15 of 45). For 40 % of the patients (18 of 45), physician support was needed during at least 2 fractions, and for 20% of the patients (9 of 45) physician support was needed during 3 or more fractions. Off-line review was performed the standard one time for 89 % of patients (40 of 45), 2 or more times for 11 % of patients (5 of 45), and 3 times for 2 % of patients (1 of 45). During 2025, RTTs required no support from physicians during on-line image assessment for 76 % of patients (13 of 17). For 6 % of the patients (1 of 17), physician support was needed during 2 fractions. Off-line review was performed the standard one time for 82 % of patients (14 of 17), 2 or more times for 18 % of patients (3 of 17), and 3 times for 6 % of patients (1 of 17).
Digital Poster Highlight 2769
Structure for minimum acceptable bladder filling facilitates efficient on-line image assessment by RTTs for UHRT prostate cancer patients Simon Jansson MFT, Region Sörmland, Eskilstuna, Sweden
Purpose/Objective: For patients receiving ultra hypo fractionated radiotherapy treatment to the prostate it is
advantageous to perform bladder preparations before treatment, to ensure adequate bladder volume and reduce toxicity. However, it can be difficult to assess the threshold for adequate bladder filling if the bladder volume is smaller on the CBCT compared to the reference CT.The purpose of this study was to simplify the assessment of adequate bladder filling by creating a structure representing the minimum
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