Presenter 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.
Author Of 2 Presentations
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.
PROTON BEAM FLASH ONLINE MONITORING AT ARRONAX CYCLOTRON
Abstract
Background and Aims
The beam monitoring tools used in conventional irradiation may not be suitable in the case of irradiation using ultra-high dose rate > 40 Gy/sec (FLASH conditions). To monitor the beam, a fast detector coupled with a high dynamic range is needed. A photomultiplier tube measuring the nitrogen fluorescence produced by the beam-air interaction
can be a solution (figure below).
Methods
The ARRONAX facility has been used to deliver proton beams (68 MeV) ranging from low (0.25 Gy/s) to very high (30 kGy/s) dose rates. An in-house prototype consisting of a photomultiplier coupled to an air cavity was used. The signal intensity can be adjusted by changing the solid angle. To verify the measured beam charge, several aluminum targets were irradiated and the produced activities of the radioisotope 24Na were measured after the end of the beam. Several beam time structures with a high number of pulses were tested. In the case of a low doses, radiochromic films (for which we have shown a response independent of the dose rate) were used.
Results
The measured beam charge using the photomultiplier tube was found in good agreement with the produced activity (1.5 %) and with the film responses (< 5 %). A wide range of dose rates was successfully monitored in the linear response region of the photomultiplier using multiple detectors.
Conclusions
We have established a new robust noninvasive method to measure doses in Flash irradiations. The next step is to use the same technology to measure beam geometrical characteristics.