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The accuracy of Magnetic Resonance – Cone Beam Computed Tomography soft-tissue matching for prostate radiotherapy

Lookup NU author(s): JJ Wyatt, Dr Rachel Pearson



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


© 2019 The AuthorsBackground and purpose: Magnetic Resonance (MR)-Only radiotherapy requires a method for matching image with on-treatment Cone Beam Computed Tomography (CBCT). This study aimed to investigate the accuracy of MR-CBCT soft-tissue matching for prostate MR-only radiotherapy. Materials and methods: Three patient cohorts were used, with all patients receiving MR and CT scans. For the first cohort (10 patients) the first fraction CBCT was automatically rigidly registered to the CT and MR scans and the MR-CT registration predicted using the MR-CBCT and CT-CBCT registrations. This was compared to the automatic MR-CT registration. For the second and third cohorts (five patients each) the first fraction CBCT was independently matched to the CT and MR by four radiographers, the MR-CBCT and CT-CBCT matches compared and the inter-observer variability assessed. The second cohort used a CT-based structure set and the third a MR-based structure set with the MR relabelled as a ‘CT’. Results: The mean difference between predicted and actual MR-CT registrations was ΔRAll=-0.1±0.2mm (s.e.m.). Radiographer MR-CBCT registrations were not significantly different to CT-CBCT, with mean differences in soft-tissue match ⩽0.2mm and all except one difference ⩽3.3mm. This was less than the MR-CBCT inter-observer limits of agreement [3.5,2.4,0.9]mm (vertical, longitudinal, lateral), which were similar (⩽0.5mm) to CT-CBCT. Conclusions: MR-CBCT soft-tissue matching is not significantly different to CT-CBCT. Relabelling the MR as a ‘CT’ does not appear to change the automatic registration. This suggests that MR-CBCT soft-tissue matching is feasible and accurate.

Publication metadata

Author(s): Wyatt JJ, Brooks RL, Ainslie D, Wilkins E, Raven E, Pilling K, Pearson RA, McCallum HM

Publication type: Article

Publication status: Published

Journal: Physics and Imaging in Radiation Oncology

Year: 2019

Volume: 12

Pages: 49-55

Online publication date: 05/12/2019

Acceptance date: 20/11/2019

Date deposited: 16/12/2019

ISSN (electronic): 2405-6316

Publisher: Elsevier Ireland Ltd


DOI: 10.1016/j.phro.2019.11.005


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