S2714
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
reproducible and efficient in reducing abdominal organ motion, with the largest benefit using NIMV60. These findings confirm the feasibility of NIMV for precise, repeatable respiratory motion management and support its clinical use for ion-beam therapy. References: Kiseleva V et al. Life (Basel) 2022; 12: 2071. doi: 10.3390/life12122071.Parkes MJ et al. Br J Radiol 2016;
echo (bFFE) sequence (TR/TE 2.9/1.13 ms, flip 50°, SENSE 2), acquired sequentially in sagittal and coronal planes. To ensure high temporal resolution, 750 dynamic scans (146 ms per scan) were performed per sequence. Organ motion was quantified using optical- flow- and demons-based non-rigid registration. Voxel- wise displacement fields were processed in Python, and motion amplitudes were derived from Euclidean distances. Reproducibility was evaluated in two MRI sessions (see Figure 1).
89: 20150741. doi: 10.1259/bjr.20150741. Keywords: non-invasive ventilation, motion management
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Value-Driven Precision radiotherapy : Clinical, Economic and Sustainable Impact of Reusing Encompass Masks in HyperArc SRT metinee wisetrintong, jumnong kumkhwao, warocha sankla, jaruek kanphet Radiation Oncology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand Purpose/Objective: This study evaluated whether reusing Encompass immobilization masks could maintain geometric accuracy comparable to new masks during HyperArc stereotactic radiotherapy (SRT) for brain lesions, while reducing treatment costs and plastic waste. The aim was to validate a value-based and sustainable model that enhances treatment accessibility and patient access to high-precision radiotherapy by lowering individual expenses and minimizing environmental burden. Material/Methods: A retrospective analysis was conducted on 31 patients treated with HyperArc SRT (3–5 fractions total 118 fractions analyzed, single-isocenter non-coplanar technique) between February 2024 and May 2025. Eighteen patients were immobilized with new masks and thirteen with reused masks, all combined with a
Figure 1: Workflow from image acquisition to analysis and visualization. Results: Average liver motion decreased by ≈ 55 % from 12.3±1.0 mm in FB to 5.5±0.4 mm at 60 brpm and by ≈ 13 % to 10.7±0.7 mm at 2 brpm. Kidney motion at 60 brpm decreased ≈ 40 % from 7.5±0.5 mm (FB) to 4.4±0.4 mm, with minimal change at 2 brpm (to 7.5±0.5 mm). Reproducibility between sessions was high: liver motion differed by ≤ 2 mm and kidney motion by ≤ 0.5 mm, both with and without the immo mask. The use of an additional immo mask does not add a significant advantage in further motion reduction. NIMV60 achieved the largest reduction in motion amplitude and decrease in variability (see Figure 2).
bite block. Reused masks were cleaned and disinfected following the hospital’s standard
procedures for medical plastic equipment before being reused once. Reused masks were visually inspected for structural integrity before use to ensure patient safety. Pre-treatment CBCT scans quantified translational (Vertical, Longitudinal, Lateral) and rotational (Pitch, Roll, Rotation) setup deviations. Systematic ( Σ ) and random ( σ ) errors were calculated using van Herk’s formula, and inter-group comparisons were performed using the Mann– Whitney U test. Economic evaluation covered mask fabrication and simulation workflow costs, while environmental benefit was assessed by the reduction in newly manufactured masks and plastic waste.
Figure 2: Effect of NIMV on abdominal organ motion. Boxplots show motion amplitudes of liver and kidneys during FB, NIMV60 and NIMV2 Conclusion: NIMV based motion reduction demonstrated to be
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