ESTRO 2025 - Abstract Book

S2719

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

ESTRO 2025

Conclusion: The amount of back scatter from an eye shield is significant. Depending on the aluminum cap thickness, the dose to eyelid near the tissue - eye shield interface increases as much as 50% over what the dose would be without a tungsten eye shield when a 6 MeV electron beam is used.

Keywords: Eye shields, backscatter, dose enhancement,

References: [1] D.W.O. Rogers, B.A. Faddegon, G.X. Ding, C.M. Ma, J. We, T.R. Mackie, BEAM: a Monte Carlo code to simulate radiotherapy treatment units, Medical physics, 22 (1995) 503-524. [2] G.X. Ding, E.C. Osmundson, E. Shinohara, N.B. Newman, M. Price, A.N. Kirschner, Monte Carlo study on dose distributions from total skin electron irradiation therapy (TSET), Physics in medicine and biology, 66 (2021).

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Digital Poster Hybrid ultra-high and conventional dose rate treatments to ease technical challenges for the clinical transfer of FLASH-RT Till T Böhlen 1 , Michele Zeverino 1 , Jean ‐ François Germond 1 , Rémy Kinj 2 , Luis Schiappacasse 2 , François Bochud 1 , Fernanda Herrera 2 , Jean Bourhis 2 , Raphaël Moeckli 1 1 Institute of Radiation Physics, Lausanne University Hospital and Lausanne University, Lausanne, Switzerland. 2 Department of Radiation Oncology, Lausanne University Hospital and Lausanne University, Lausanne, Switzerland Purpose/Objective: Delivering dosimetrically conformal treatments to deeper-seated tumours at ultra-high dose rates (UHDR, average dose rate ≳ 100 Gy/s) poses a considerable technical challenge for the clinical adoption of FLASH-RT. This work presents hybrid UHDR-conventional dose rate (HUC) treatments as a potential solution to reduce technical burdens in delivering conformal FLASH-RT and to improve its accessibility. Material/Methods: HUC treatments utilize a single broad UHDR electron beam with a case-specific energy between 10-50 MeV, delivering the bulk treatment dose, complemented by a conventional dose rate (CDR) IMRT/VMAT plan to enhance dosimetric target coverage and conformity. HUC plans based on clinical prescriptions were optimized using