ESTRO 2025 - Abstract Book

S4135

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

3775

Digital Poster Application of open-face masks and a surface-guided radiotherapy system in patients undergoing stereotactic radiotherapy for head and neck regions Dawid Bodusz 1 , Michał Nachlik 1 , Tomasz Rutkowski 2 , Jerzy Wydmański 1 1 Radiotherapy Department, National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 2 Department of Science and Clinical Research Coordination, National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland Purpose/Objective: Potential geometric errors in the delivery of therapeutic beams during stereotactic radiotherapy can significantly affect clinical outcomes in terms of both efficacy and complications. Ensuring maximum possible patient comfort during positioning is another critical factor in treatment. This study aimed to evaluate the precision of therapeutic position reproducibility and stability during radiotherapy sessions in patients treated for head and neck areas using open-face thermoplastic masks and a surface-guided radiotherapy (SGRT) system. Material/Methods: The study included 60 patients (232 fractions) undergoing stereotactic radiotherapy for head and neck regions, where open-face thermoplastic masks were used for immobilization. Patient positioning was facilitated using a surface-guided radiotherapy system, followed by cone-beam computed tomography (CBCT) imaging to assess setup accuracy. Intrafractional motion was monitored throughout each session using the surface-guided system. Results: The mean deviations between planned and actual positions were 2.9 mm (SD=1.4) in the vertical (vrt) direction, 1.3 mm (SD=1.1) in the longitudinal (lng) direction, and 0.7 mm (SD=0.6) in the lateral (lat) direction. The median deviations were 3.0 mm, 0.8 mm, and 0.5 mm, respectively. The mean rotational deviations around the three axes were 0.94° (SD=0.71) in vrt, 0.58° (SD=0.45) in lng, and 0.55° (SD=0.56) in lat. The maximum mean intrafractional motion detected by the SGRT system was 0.5 mm in vrt, 0.7 mm in lng, and 0.5 mm in lat, with a maximum mean rotational motion of 0.5° across all axes. The use of a bite block did not influence positional reproducibility in lng or lat (p>0.05). The mean deviation in the vrt direction was 2.7 mm for masks with a bite block and 3.1 mm for masks without a bite block, a statistically significant difference (p=0.0001). Conclusion: The application of open-face thermoplastic masks in stereotactic radiotherapy for head and neck regions appears to offer a comfortable solution for patients while ensuring precise reproducibility and stability of therapeutic positioning during each radiotherapy session. The integration of SGRT for markerless/tattooless positioning is feasible in this patient group. The use of masks with a bite block improves the stability of patient positioning during radiotherapy.

Keywords: open-face mask, surfice guided radiotherapy

3792

Mini-Oral Feasibility and accuracy of patient setup in gynaecological cancer treatments using Surface-Guided Radiotherapy

Kirsten Offereins - van Harten, Maarten L.P. Dirkx, Joan J. Penninkhof Radiotherapy, Erasmus MC Cancer Institute, Rotterdam, Netherlands