S2736
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
Material/Methods: 174 patients and healthy volunteers were imaged under PRIMER (NCT02973828 (1)), a multi-institution imaging study between 2019 and 2025. Validated questionnaires scoring experience on a 5-point Likert scale were administered to participants at a single institution following each session to measure experience and tolerability of site-specific procedures. For participants that had more than one scan, only the questionnaire from the first session was used. Additionally, participants were asked to compare their MR Linac experience to recent diagnostic imaging on diagnostic magnetic resonance imaging (MRI). Participants were grouped according to site-specific immobilisation and positioning to assess relationships between this factor and adverse experience using Pearson correlation testing. Results: A total of 231 questionnaires were completed by 174 participants following imaging with various immobilisation devices for the anatomical sites: head and neck (H&N) (n=41), pelvis (n=48), abdomen (n=39), and thorax (n=46). Questionnaire completeness was 33%, with the final two questions comparing MRL scan with a diagnostic MRI commonly being omitted.Mean scan time for all participants was 44 m 13 s (SD 11 m 19s). For participants who reported discomfort during the scan, 55% were positioned using additional immobilisation devices beyond a pillow under their head. These included:33% on a lung board,12% with a 5-point mask,9% with abdominal compression.No relationship was found between scan length and reported discomfort (r = 0.15). Instead, the type of immobilisation device was the strongest predictor of tolerability, for example participants scanned using only a pillow under their head generally tolerated the scan better.Among the 57 participants who completed the full questionnaire, 88% did not find scans on the MR Linac more difficult than those on a diagnostic MRI. Additionally, 75% of participants expressed no anxiety about undergoing future scans on the MR Linac. Report details are shown in Fig. 1.
Chest wall setup errors for both LMT and LLT were consistently within 2.5 mm. These results support reducing the current 10 mm gating window to approximately 5 mm, which may further minimize cardiac exposure and enhance the therapeutic benefit of DIBH without compromising setup accuracy. Consistent coaching and video-assisted guidance remain essential to maintain breath-hold stability when implementing a smaller gating window References: 1. S. C. Darby et al.,Risk of ischemic heart disease in women after radiotherapy for breast cancer., N. Engl. J. Med., vol. 368, no. 11, Mar. 20132. C. Bergom, A. Currey, N. Desai, A. Tai, and J. B. Strauss, Deep Inspiration Breath Hold: Techniques and Advantages for Cardiac Sparing During Breast Cancer Irradiation.,” Front. Oncol., vol. 8, 2018.3. J. Boda-Heggemann et al.,Deep Inspiration Breath Hold-Based Radiation Therapy: A Clinical Review.,” Int. J. Radiat. Oncol. Biol. Phys., vol. 94, no. 3, Mar. 2016.4. W. Lu et al.,Reproducibility of chestwall and heart position using surface-guided versus RPM-guided DIBH radiotherapy for left breast cancer., J. Appl. Clin. Med. Phys., vol. 24, no. 1, Jan. 2023. Keywords: Breath-hold, cine image, cardiac sparing Impact of immobilisation on patient comfort on the MR Linac: results of a patient experience questionnaire Rebecca Riding 1 , Alice Greenwood-Wilson 1 , Claire Nelder 1 , Lee Whiteside 1 , Lisa McDaid 1 , Benedict Dobby 1 , James Tallon 1 , Mairead Daly 2 , Robert Chuter 3,2 , Michael Dubec 4 , Corinne Faivre-Finn 5,2 , Marcel Van Herk 2 , Ananya Choudhury 2,5 , Cynthia L Eccles 1,2 1 Radiotherapy, The Christie NHS Foundation Trust, Manchester, United Kingdom. 2 Division of cancer sciences, The University of Manchester, Manchester, United Kingdom. 3 Radiotherapy Physics, The Christie NHS Foundation Trust, Manchester, United Kingdom. 4 MR physics, The Christie NHS Foundation Trust, Manchester, United Kingdom. 5 Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom Purpose/Objective: Magnetic resonance linear accelerators (MR Linac) are an increasingly popular option for adaptive radiotherapy to complex anatomical areas difficult to visualise on cone beam computed tomography (CBCT). Imaging and adaptation increase treatment duration compared to conventional Linacs. This work evaluates the experience and tolerability of imaging and treatment on the Elekta Unity MR Linac. Digital Poster 3073
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