ESTRO 2025 - Abstract Book

S3078

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

Conclusion: The daily sCT-based dose calculation software is an effective tool for automating the monitoring of target coverage and OARs, as well as identifying patients who may be receiving suboptimal treatment.

Keywords: prostate cancer, daily dose calculation, sCT

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Digital Poster Improved accuracy of dose calculations for online adaptive prostate radiotherapy using direct dose calculations on HyperSight CBCT vs synthetic CT Kate Keddie, Ewan Almond, Ghirmay Kidane Radiotherapy Physics, Queen's Hospital, Romford, United Kingdom Purpose/Objective: Online adaptive radiotherapy (oART) allows plan adaptation to patients' daily anatomy, enhancing accuracy and reducing normal tissue dose 1,2,3 . Varian's Ethos platform uses AI and deformable registration for oART, re-optimising plans using a synthetic CT (sCT) created by deformable registration of planning CT to CBCT, 4 which can introduce dosimetric uncertainties 5,6 . This project evaluates direct HyperSight CBCT dose calculation to eliminate the sCT in the Ethos pathway.

Material/Methods: HU calibration curves for HyperSight CBCT were created using the CIRS ED phantom 7 . Using this calibration, the