ESTRO 2025 - Abstract Book

S3153

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

Keywords: cumulative dose, deformable image registration

References: 1. Rigaud, Bastien, et al. "Deformable image registration for radiation therapy: principle, methods, applications and evaluation." Acta Oncologica 58.9 (2019): 1225-1237 2. Oh, Seungjong, and Siyong Kim. "Deformable image registration in radiation therapy." Radiation oncology journal 35.2 (2017): 101 3. Way, S. M., et al. "Physician Assessment and Clinical Evaluation of the Suitability of Deep Learning Based Auto Segmentation Contours for Organs at Risk Delineation in Radiation Oncology." International Journal of Radiation Oncology, Biology, Physics 120.2 (2024): e594 4. Czajkowski, Paweł, and Tomasz Piotrowski. "Registration methods in radiotherapy." Reports of Practical Oncology and Radiotherapy 24.1 (2019): 28-34

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Digital Poster Revisiting inter-fraction setup errors in head and neck patients: two-dimensional versus three-dimensional IGRT Abousaleh Elawadi 1 , Fawaz Alasmari 1 , Reem Alomran 2 , Ahmed Maklad 2 , Amal Marie 2 , Nwaf Alkhanein 2 , Mukhtar Alshanqity 1 1 Department of Medical Physics, King Fahad Medical City, Riyadh, Saudi Arabia. 2 Department of Radiation Oncology, King Fahad Medical City, Riyadh, Saudi Arabia Purpose/Objective: This study investigated the accuracy of patient setup and positioning errors for brain and head and neck (H&N) cancers during image guided radiotherapy (IGRT) to determine required tumor margin. Material/Methods: The study included 363 cancer patients, comprising 183 brain cancer cases and 183 head and neck (H&N) cancer cases. It evaluated setup errors and the Planning Target Volume (PTV) margin using kV imaging. Results: The mean setup errors using 2-D kV imaging in the vertical, longitudinal, lateral, and rotational directions were - 0.25±1.10 mm, -1.03±1.19 mm, -0.12±0.93 mm, and 0.07°±0.33°, respectively. With CBCT, these values were 0.17±0.73 mm, 0.12±0.82 mm, -0.18±0.74 mm, and 0.06°±0.38°, respectively. The mean 3-D Total Vector Error (TVE) was 1.91±0.99 mm using 2-D kV and 1.18±0.67 mm with CBCT. For head and neck (H&N) cancers, the mean translational setup errors with 2-D kV imaging in the vertical, longitudinal, lateral, and rotational directions were - 0.95±1.3 mm, 0.11±1.22 mm, -0.29±1.01 mm, and 0.05°±0.31°, respectively. With CBCT, these values were -0.06±0.9 mm, 0.22±0.69 mm, -0.27±0.80 mm, and -0.01°±0.36°, respectively. The mean 3-D TVE was 2.08±0.95 mm using 2-D kV and 1.21±0.77 mm with CBCT. For brain treatments, the maximum inter-fraction setup error was less than 4 mm with 2-D kV imaging and less than 3 mm with CBCT. For H&N treatments, the maximum PTV margin was less than 4.6 mm with 2-D kV and less than 3.5 mm with CBCT.