S2218
Physics - Intra-fraction motion management and real-time adaptive radiotherapy
ESTRO 2026
breath-hold CT was analyzed. The blurring of the dose distribution caused by organ motion was modeled as a convolution of the planned dose distribution with a probability density function (PDF) [3]. Two dose distributions were constructed: one based on the residual motion after tracking (A), and the other simulating dose delivery without respiratory motion compensation (B). In a sub-cohort of 10 patients, 4DCT images were available and used to calculate the blurred dose distribution combining the effect of untracked motion and mismatch in motion trace between the tracking surrogate and the target (C).
the mask. References: 1.
Clover K, Oultram S, Adams C, et al (2011) Disruption to radiation therapy sessions due to anxiety among patients receiving radiation therapy to the head and neck area can be predicted using patient self-report measures. Psychooncology 20:1334–1341. https://doi.org/10.1002/pon.18542. Ben Bouchta Y, Gardner M, Sengupta C, et al (2024) The Remove- the-Mask Open-Source head and neck Surface-Guided radiation therapy system. Phys Imaging Radiat Oncol 29:100541. https://doi.org/10.1016/J.PHRO.2024.1005413. Wise FM, Harris DW, Olver JH. The DASS-14: Improving the Construct Validity and Reliability of the Depression, Anxiety, and Stress Scale in a Cohort of Health Professionals. J. Allied Health. 2017;46:e85–e90. Keywords: SGRT, Mask Anxiety, Surface Imaging STereotactic Arrhythmia Radioablation (STAR) using CyberKnife: including intra-fraction data for delivered dose estimation Yuliya Shpunarska 1 , Pavel Dvorak 2 , Lukas Knybel 2 , Piotr Pater 1 , Luuk H.G. van der Pol 3 , Martin F. Fast 3 , Jakub Cvek 2 1 Medical Physics Unit, McGill University, Montreal, Canada. 2 Department of Oncology, University Hospital Ostrava, Ostrava, Czech Republic. 3 Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands Purpose/Objective: STereotactic Arrhythmia Radioablation (STAR) is a non- invasive treatment of refractory ventricular tachycardia, which is complicated by cardiac and respiratory motion [1]. The CyberKnife (CK) is a stereotactic linac that compensates for breathing motion [2] with a respiratory model that records the correlation error (CE), or the difference between the predicted and actual position of the tracked point. During STAR, CE is greater than in treatments of other organs [2]. Given this increase, this work aims to validate whether respiratory motion compensation by the CK remains acceptable for STAR treatments. Additionally, CK tracking during STAR uses a surrogate (the tip of the ICD lead) that is potentially several centimeters away from the treatment target and may display differential motion relative to the target. This work further seeks to incorporate the uncertainty of this mismatch into the delivered dose estimation. Material/Methods: A cohort of 36 STAR patients with a planned dose distribution optimized and calculated on expiration Mini-Oral 1227
The target volume was recreated by shrinking the PTV isotropically by 2 mm. The stomach and esophagus were selected as the most critical OARs. Differences between dose distributions were evaluated based on common dosimetric constraints [4]. Results: Under CE blurring only (Table 1, A), changes to most dose statistics are under 5%, demonstrating good motion compensation despite increased CE due to heart motion. If no respiratory tracking is used (B), mean target coverage drops from 99.3% to 70.9%. When including both CE blurring and blurring due to surrogate-to-target mismatch (C), doses to the stomach are increased by 8.8% on average and 19.4% at most, and mean target coverage is reduced from 99.0% to 95.5%.
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