Author Of 1 Presentation
UHDR PROTON BEAM VS. CONVENTIONAL: HYDROGEN PEROXIDE AS FLASH EFFECT SENSOR
Abstract
Background and Aims
Several models assume that delivering radiation at ultra-high dose rates (UHDR) reduces the yields of reactive oxygen species (ROS). Montay-Gruel et al [1] measured a significant decrease of Hydrogen Peroxide (H2O2) after UHDR irradiation compared to conventional dose-rate irradiation (CONV) with electrons. This study aims to verify this assumption in proton beams. We study the UHDR radiation chemistry by the measurement of H2O2 produced by the water radiolysis. Fricke dosimeter is used as dose control and as ROS sensor as well.
Methods
Using ARRONAX facility, we produced proton beams (68MeV) ranging from low (0.25Gy/s, 100Hz, pulse dose rate=6.3Gy/s) to ultra-high dose rates (7500Gy/s, single pulse). Doses ranging from 5Gy to 80Gy were delivered to 1.5ml Eppendorf tubes filled with water. In this investigation, Fricke dosimetry [2] is used to verify the dose for both irradiation modes. The second step is the determination of H2O2 concentrations after irradiation with the Ghormley triiodide method [3].
Results
In this work, we have brought the evidence of the Flash effect by the H2O2 measurement in the two cases: (i) For CONV irradiations, we determined a H2O2 chemical yield close to the literature at 0.9 10-7 mol.J-1 [4], (ii) For UHDR irradiations, this yield is measured to a significant lower value. Observed Fricke values are the same for both modes.
Conclusions
We have revealed a radio-chemical FLASH effect for the proton beam by the H2O2 measurement as radiolytic species during the irradiation of water. Further studies will be performed to determine the beam time structure effect.