ESTRO 2025 - Abstract Book

S2898

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

3813

Digital Poster Skin dose in prone breast radiotherapy with a novel personalized 3D-printed immobilization device Mania Aspradakis 1 , Alessandro Clivio 1 , Martin Staudacher 2 , Giovanna Dipasquale 3 , Johannes W. E. Uiterwijk 3 , Ruggero Ruggieri 4 , Cédric De Marco 5 , Marie Fargier-Voiron 5 , Maud Jaccard 5 , Luca Nicosia 4 , Andrea Romei 4 , Gunther Gruber 2 , Filippo Alongi 4,6 , Oscar Matzinger 5,7 , Daniel R. Zwahlen 1 1 Radiation Oncology, Kantonsspital, Winterthur, Switzerland. 2 Institute for Radiotherapy, Klinik Hirslanden, Zurich, Switzerland. 3 Development Department, HeroSupport SA, Veyrier, Switzerland. 4 Advanced Radiation Oncology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, Italy. 5 Radiation Oncology, Clinique de Genolier, Genolier, Switzerland. 6 Faculty of Medicine, University of Brescia, Brescia, Italy. 7 Health Science and Technology, ETH Zurich, Zurich, Switzerland Purpose/Objective: The purpose of this study was to demonstrate the feasibility of optimizing skin dose in prone breast radiotherapy using the VENUS Shell™ 3D-printed immobilization device (shells) [1] across various treatment machines. Additionally, we aimed to verify calculated doses in the build-up region and skin through measurements in both geometric and anthropomorphic phantoms. Material/Methods: IMRT plans were generated on a RANDO phantom with four configurations, (no shell, solid cup, mesh cup and VENUS Shell™ (Fig.1)), for delivery on Varian Truebeam v3.0 (6, 10MV beams), Accuray Radixact v3.5 (6FFF), Elekta Unity MR-Linac (7MV). Planning was done using Eclipse (Acuros XB v17.0.1), Raystation (v.12ASP2), Monaco (v.6.2). PTVs were cropped 3mm from the skin, and dose prescription was 40.05Gy in 15 fractions. Skin dose was analysed using dose-volume metrics for 3mm (“skin3mm”) and 5mm (“SkinBody5mm”) structures. Dose calculations at 6MV with Acuros XB were verified on the Alderson phantom with TLDs (100H, chip 0.6mm thick) at 19 positions repeated five times (Fig.1). The shell’s impact on dose in the build-up region was evaluated from measurements in 6 and 10MV beams with a plane-parallel ionization chamber (Advanced Markus) in Solid Water HE with and without a 5mm thick shell either solid or mesh (source-to-surface distance at 90cm and for square collimator settings (4, 10, 20cm)) (Fig,1).