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A combined automatic organ at risk contouring and synthetic Computed Tomography solution for pelvic Magnetic Resonance-only radiotherapy

Lookup NU author(s): JJ Wyatt, Dr Rachel Pearson, Dr Ross Maxwell, Dr Hazel McCallum

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2026 The Authors. Published by Elsevier B.V. on behalf of European Society of Radiotherapy & Oncology. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/Background and Purpose:Magnetic Resonance (MR)-only radiotherapy improves treatment accuracy and efficiency but requires a synthetic Computed Tomography (sCT) for dose calculations. Automatic MR-based Organs At Risk (OARs) contouring could further improve consistency and efficiency. A combined automatic MR OAR contouring and sCT solution has been developed, with each component separately validated. This study aimed to evaluate this combined MR-only workflow against a manual MR-CT workflow for pelvic cancers.Materials and Methods:Radiotherapy MR and CT scans were acquired for 20 patients (10 prostate, 4 rectum, 6 anus cancer). The MR-only workflow used sCTs and automatic contours for the bladder, bowel bag, femoral heads, rectum, penile bulb, prostate, seminal vesicles and urethra along with manual target contours to optimise a MR-only plan. Doses were compared to the current clinical standard of deformably registered CT and manual MR OAR contours (MR-CT).Results:Mean dose differences were (Formula presented) ; 1 percentage point relative volume for all OARs except the bowel bag. Mean absolute dose differences were also (Formula presented) for all OARs except bowel bag in ano-rectal patients and except bowel bag, bladder V(Formula presented), V(Formula presented), V(Formula presented) and rectum V(Formula presented) in prostate patients.Conclusions:The automatic MR OAR contouring and sCT workflow had similar dose differences to manual inter-observer variability for all OARs except the lower dose bladder and rectum volumes (prostate patients only) and bowel bag (prostate and ano-rectal patients). This combined OAR contouring and MR-only workflow could enable more efficient and consistent pelvic radiotherapy treatment.

Publication metadata

Author(s): Wyatt JJ, Kaushik S, Cozzini C, Kolozsvari B, Deak-Karancsi B, Pearson RA, Petit S, Capala M, Hernandez-Tamames JA, Hideghety K, Maxwell RJ, Rusko L, Wiesinger F, McCallum HM

Publication type: Article

Publication status: Published

Journal: Physics and Imaging in Radiation Oncology

Year: 2026

Volume: 37

Online publication date: 09/02/2026

Acceptance date: 02/02/2026

Date deposited: 13/04/2026

ISSN (electronic): 2405-6316

Publisher: Elsevier Inc.

URL: https://doi.org/10.1016/j.phro.2026.100918

DOI: 10.1016/j.phro.2026.100918

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