Ultra-high dose rate protons in clinical irradiation suppress DNA single-strand breaks induction in the below nano-second time scale of physicochemical stages.

Purpose: This study investigated the impact of ultra-high dose rate (UHDR) proton radiotherapy on DNA damage compared to conventional dose rate (CONV) radiotherapy. We hypothesized that the unique physicochemical processes associated with UHDR could lead to a reduction of DNA damage. Thus, the aim of this study is to clarify the time scale of the physicochemical processes in which the suppression of SSBs by UHDR proton irradiation occurs.

Dose Rate Effects on Hydrated Electrons, Hydrogen Peroxide, and a OH Radical Molecular Probe Under Clinical Energy Protons.

We report the dose rate dependence of radiation chemical yields (G value) of water radiolysis products under clinical energy protons (230 MeV) to understand mechanisms of the FLASH radiotherapy performed at ultra-high dose rate (>40 Gy/s). The G value of 7-hydoroxy-coumarin-3-carboxylic acid (7OH-C3CA) produced by reactions of coumarin-3-carboxylic acid (C3CA) with OH radicals and oxygen is evaluated by fluorescence method. Also, those of hydrated electrons and hydrogen peroxide are derived by absorption method using Saltzman and Ghomley techniques, respectively.

FLASH dose rate calculation based on log files in proton pencil beam scanning therapy.

Background: In radiation therapy, irradiating healthy normal tissues in the beam trajectories is inevitable. This unnecessary dose means that patients undergoing treatment risk developing side effects. Recently, FLASH radiotherapy delivering ultra-high-dose-rate beams has been re-examined because of its normal-tissue-sparing effect.