ESTRO 2025 - Abstract Book

S2392

Interdisciplinary – Other

ESTRO 2025

Results We obtained LET values of 1.13 keV/µm for protons and 14.7 keV/µm for alpha particles. Simulated G(H 2 O 2 ) and G(e aq ) values were obtained 1 hour post-irradiation along the time. The results under aerated conditions with protons showed that the lifetimes of e aq and H ⦁ were shorter due to scavenging by O ₂ , leading to higher G(H 2 O 2 ) and faster G(e aq ) consumption than deaerated conditions. The alpha beamline showed a similar tendency to the proton’s results; however, its higher LET, G(e aq ), was consumed more rapidly than the proton’s. In measurements, G(H 2 O 2 ) was obtained after 15 minutes at saturation, while G(e aq ) was measured at 2 µs before being completely consumed. G(e aq ) showed faster consumption in both measurement and simulation under aerated conditions. Additionally, higher dose rates and LET resulted in lower G-values of H ₂ O ₂ and faster consuming e aq . Conclusion These findings indicate that reduced H ₂ O ₂ production may result from OH ⦁ and e-aq reactions taking precedence over OH ⦁ combining to form H ₂ O ₂ [2]. To go further, we will estimate radiolytic species' interaction with various biomolecules to understand radiation-induced biochemical changes and improve radiation therapy. References [1] Favaudon V, Caplier L, Monceau V, Pouzoulet F, Sayarath M, Fouillade C, Poupon MF, Brito I, Hupé P, Bourhis J, Hall J, Fontaine JJ and Vozenin MC. Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice. Science translational medicine 6, 245, 2014. [2] Guillaume B, Johan V, Daphnée V, Vincent F, Giovanna F, Ferid H, Charbel K, Lydia M, Vincent M, Freddy P, et al. Proton Irradiations at Ultra-High Dose Rate vs. Conventional Dose Rate: Strong Impact on Hydrogen Peroxide Yield. Radiation Research, 198, 318, 2022. Keywords: UHDR, water radiolysis , Monte Carlo simulation