S2725
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
Digital Poster Highlight 2301
a customised stereotactic immobilisation system using pre and post treatment imaging and to estimate appropriate planning target volume (PTV) margins based on observed systematic and random errors. Material/Methods: A total forty-nine patients who received SRS treatment over five year period were retrospectively reviewed, comprising six single high-dose fraction and forty- three hypo fractionation (3-5 fractions). Treatment were delivered using 6 MV FFF photon beam on Varian True beam (V. 2.7). SRS doses ranged from 27-32 Gy in 3-5 fractions, and from 13-22 Gy in a single fraction. Each plan used 4-6 full or partial arcs, depending on PTV location, and was created on Eclipse TPS (version 16.5). Patient positioning was achieved using CIVCO trUpoint ARCH system with a thermoplastic mask in the supine position to ensure sub-millimetre accuracy. All patients received pre-treatment medications. Pre- treatment Cone-beam CT (CBCT) imaging was performed to assess set up errors and post- treatment imaging was acquired to evaluate residual error along the lateral (X), longitudinal (Y), and vertical (Z) axes. PTV margins were estimated using the Van Herk Pre-treatment CBCTs analysis showed mean displacements in lateral (X), longitudinal (Y), and vertical (Z) axes are +0.64, +0.13 and -0.12 mm, respectively. The corresponding systematic error were 0.61, 0.85, and 0.62 mm and the random error were 0.06, 0.11, and 0.06 mm, respectively, indicating good anatomical reproducibility. Based on these parameters, the calculated PTV margins were 2.09 mm in the lateral, 2.85 mm in the longitudinal, and 2.08 mm in the vertical direction. Post treatment CBCT residual error analysis showed mean displacements in lateral (X), longitudinal (Y), and vertical (Z) axes were +0.14, +0.25 and -0.04 mm, respectively. Conclusion: formula. Results: Evaluation of pre- and post-treatment CBCT data in SRS for intracranial lesions demonstrated high setup accuracy and reproducibility. Although the estimated PTV margins were slightly higher than the clinical tolerance, the pre-treatment mean translational shifts with Systematic and random errors and the mean residual errors remained well within the 1 mm margin, confirming the robustness and precision of the immobilisation system and image-guided setup verification in ensuring accurate and consistent patient positioning for intracranial stereotactic treatments. References: https://www.annalsofoncology.org/article/S0923- 7534(19)47784- 3/fulltexthttps://pmc.ncbi.nlm.nih.gov/articles/PMC707 5371/ Keywords: Set-up Errors, Cranial, SRS
Patient Information in preparation for Radiotherapy; Current Status in UK Helen A McNair 1,2 , Amanda Webster 3,4 , Sophie E Alexander 1,2 1 Academic Radiography, Royal Marsden NHS Foundation Trust, London, United Kingdom. 2 Divsion of Radiotherapy and Imaging, Institute of Cancer Research, London, United Kingdom. 3 Radiotherapy and Proton Beam Therapy, University College London Hospital, London, United Kingdom. 4 Medical Physics and Biomedical Engineering, University College London, London, United Kingdom Purpose/Objective: Despite being a core cancer treatment, public understanding of radiotherapy (RT) remains limited, with patients reporting fears such as ‘burning’, ‘being radioactive’, or ‘internal damage’(1). Standardised RT information may not meet individual needs. Tailoring by age, literacy, or tumour type could enhance inclusivity and patient experience, but practical guidance is lacking (2,3). This study explores current UK RT information practices to assess the need for tailored communication guidelines. Material/Methods: A survey was developed from an existing instrument (4) and refined with information-expert radiographers (RTT’s). Nine experts completed content validity (all items scored >0.78). The survey was piloted with five RTTs, leading to the addition of a “Not applicable” option, clarification of ‘patient groups’, and condensed response options.The Qualtrics platform was used to collect multiple-response matrix questions on information formats by tumour site. The survey was emailed to all 64 UK NHS radiotherapy providers. Descriptive statistics summarised results: free-text answers were thematically grouped. Completion indicated consent, and all responses were anonymised. Results: The response rate was 69% (44/64). RT Information was most frequently provided verbally (34/44) or in print (35/44) at RT consent, followed by verbal explanations pre-treatment (25/44) and first treatment (33/44).Information was mainly delivered by RTTs/tumour-site-specialist RTTs (40/44 and 33/44, respectively), clinical oncologists (40/44) and clinical nurse specialists (23/44). Additional methods included QR codes linking to videos or charity websites.Across tumour sites, the median (range) of formats was 123 (80-157). Prostate cancer (n=157) and breast cancer patients (n=145) receive the widest range of formats and greater signposting to additional resources including exercise programs and support groups.
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