ESTRO 2025 - Abstract Book

S2990

Physics - Image acquisition and processing

ESTRO 2025

Results: All diagnostic reference plans REF diag optimised successfully, meeting all mandatory goals.

Deformed bones and body contours from the diagnostic reference to the clinical #1 MRL image required no edits. All adapted plans ATS diag optimised successfully, meeting all mandatory clinical goals. All ATS clin optimal goals were also achieved in ATS diag , apart from 1 patient. Conversely for 2 patients, ATS diag achieved 2 additional optimal goals than ATS clin . The median PTV D50% deviation between ATS diag and ATS ED was 0.75% (range -0.1-1.2%), with median gamma pass rates 99.6% (range 99.2-99.7%). Conclusion: Non RT-dedicated diagnostic MRs can be used for reference prostate planning on the MRL, generating clinically acceptable adapted plans with acceptable dose calculation accuracy. Despite diagnostic MRs not using RT-specific setup including flat tabletops and patient preparation, the online adaption is able to manage large anatomy changes in the body and bone contours. In future, autosegmentation may also eliminate the need for manual recontouring online. Treatment planning on already acquired diagnostic scans would remove the wait for simulation appointments removing any associated delay from the treatment pathway.

Keywords: Simulation-free radiotherapy, MR linac, adaptive

References: [1] Westley et al. Clin Oncol (R Coll Radiol). 2022 Jul;34(7) [2] Stankiewicz et al. STEF, 2023