Experimental and simulated H2O2 in pure water under conventional and ultra-high dose rates for single pulse proton irradiation
Abstract
Background: Despite the remarkable sparing of normal tissue by FLASH radiotherapy, the fundamental mechanisms that link physics to biological outcomes remain unclear. Among water radiolysis species produced after irradiation, hydrogen peroxide (H2O2 ) is a final product resulting from hydroxyl radical (OH • ) and reactive oxygen species ( HO2 • /O2•- ) reactions, sources of biological damage. Many experiments have shown that increasing the dose rate, reduces H2O2 yields, supporting hypotheses related to a transient hypoxia during irradiation. Reproducing experimental data using Monte Carlo simulations can be challenging due to incomplete or ambiguous information about the actual experimental conditions, such as the thorough measurement of oxygen or pH levels. Purpose: Through water radiolysis experiments and simulations, we propose to understand the fundamental mechanisms responsible for the production of H2O2 under varying oxygen and dose rate conditions. A new Geant4-DNA chemistry module, managing pulse duration, is specifically tested. Methods: Ultra-pure water samples were irradiated with a 67.5 MeV proton beam delivered by the ARRONAX isochronous cyclotron (IBA Cyclone 70XP) at dose rates ranging from a conventional dose rate (CDR, 0.2 Gy/s) to ultra-high dose rates (UHDR, ~6 kGy/s). The concentration of H2O2 , used as a final endpoint providing insight into earlier processes, was quantified using the Ghormley triiodide protocol. We reproduced irradiation conditions using the GATE and Geant4-DNA Monte Carlo libraries. Beam alignment and dose homogeneity were verified using a gamma-index method. A Geant4-DNA chemistry module (Geant4 11.4beta version) was used to calculate the time-dependent evolution of radiolytic yields for H • , OH • , eat- , HO2 • , O2•- and H2O2 species until 15 minutes post irradiation, taking into account the oxygen concentration, pH, absorbed dose, and pulse duration. Results: Under aerated conditions, for CDR, the simulated (2.18) and experimental (2.13) G(H2O2 ) are in close agreement. At higher dose rates, the decrease of G(H2O2 ) is very similar between experiments and simulations. Under deaerated conditions, simulated G( H2O2) decreased from 1.56 at 0.26 Gy/s to 1.22 at 42 Gy/s, with relative differences of 1.3% and 0.8 % compared to the experiment. The impact of CO2 content is evaluated through simulation studies and discussed. Conclusions: The Geant4-DNA chemistry module reproduces with a good agreement experimental H2O2 yields measured under different oxygen levels and dose rates. Both experiments and simulations show an oxygen dependent decrease in G(H2O2 ) under UHDR conditions. Simulations indicate an impact of the CO2 content at physiological level. As perspectives, we aim at studying the role of hydrated electron associated to the understanding of CO2 and O2 effects through time resolved radicals' measurement.
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BibTeX
@article{kwon2026experimental,
title = {{Experimental and simulated H2O2 in pure water under conventional and ultra-high dose rates for single pulse proton irradiation}},
author = {Daeun Kwon and Vincent Fiegel and Guillaume Blain and Sophie Chiavassa and Tuan Anh Le and Hoang Ngoc Tran and Sarra Terfas and Manon Evin and Emeline Craff and Sébastien Incerti and Grégory Delpon and Ferid Haddad and Charbel Koumeir and Lydia Maigne},
journal = {Medical Physics : The international journal of medical physics research and practice},
year = {2026},
month = jun,
doi = {10.1002/mp.70531},
url = {https://hal.science/hal-05800660v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Experimental and simulated H2O2 in pure water under conventional and ultra-high dose rates for single pulse proton irradiation
AU - Daeun Kwon
AU - Vincent Fiegel
AU - Guillaume Blain
AU - Sophie Chiavassa
AU - Tuan Anh Le
AU - Hoang Ngoc Tran
AU - Sarra Terfas
AU - Manon Evin
AU - Emeline Craff
AU - Sébastien Incerti
AU - Grégory Delpon
AU - Ferid Haddad
AU - Charbel Koumeir
AU - Lydia Maigne
PY - 2026
DA - 2026/06/25
JO - Medical Physics : The international journal of medical physics research and practice
DO - 10.1002/mp.70531
UR - https://hal.science/hal-05800660v1
AB - Background: Despite the remarkable sparing of normal tissue by FLASH radiotherapy, the fundamental mechanisms that link physics to biological outcomes remain unclear. Among water radiolysis species produced after irradiation, hydrogen peroxide (H2O2 ) is a final product resulting from hydroxyl radical (OH • ) and reactive oxygen species ( HO2 • /O2•- ) reactions, sources of biological damage. Many experiments have shown that increasing the dose rate, reduces H2O2 yields, supporting hypotheses related to a transient hypoxia during irradiation. Reproducing experimental data using Monte Carlo simulations can be challenging due to incomplete or ambiguous information about the actual experimental conditions, such as the thorough measurement of oxygen or pH levels. Purpose: Through water radiolysis experiments and simulations, we propose to understand the fundamental mechanisms responsible for the production of H2O2 under varying oxygen and dose rate conditions. A new Geant4-DNA chemistry module, managing pulse duration, is specifically tested. Methods: Ultra-pure water samples were irradiated with a 67.5 MeV proton beam delivered by the ARRONAX isochronous cyclotron (IBA Cyclone 70XP) at dose rates ranging from a conventional dose rate (CDR, 0.2 Gy/s) to ultra-high dose rates (UHDR, ~6 kGy/s). The concentration of H2O2 , used as a final endpoint providing insight into earlier processes, was quantified using the Ghormley triiodide protocol. We reproduced irradiation conditions using the GATE and Geant4-DNA Monte Carlo libraries. Beam alignment and dose homogeneity were verified using a gamma-index method. A Geant4-DNA chemistry module (Geant4 11.4beta version) was used to calculate the time-dependent evolution of radiolytic yields for H • , OH • , eat- , HO2 • , O2•- and H2O2 species until 15 minutes post irradiation, taking into account the oxygen concentration, pH, absorbed dose, and pulse duration. Results: Under aerated conditions, for CDR, the simulated (2.18) and experimental (2.13) G(H2O2 ) are in close agreement. At higher dose rates, the decrease of G(H2O2 ) is very similar between experiments and simulations. Under deaerated conditions, simulated G( H2O2) decreased from 1.56 at 0.26 Gy/s to 1.22 at 42 Gy/s, with relative differences of 1.3% and 0.8 % compared to the experiment. The impact of CO2 content is evaluated through simulation studies and discussed. Conclusions: The Geant4-DNA chemistry module reproduces with a good agreement experimental H2O2 yields measured under different oxygen levels and dose rates. Both experiments and simulations show an oxygen dependent decrease in G(H2O2 ) under UHDR conditions. Simulations indicate an impact of the CO2 content at physiological level. As perspectives, we aim at studying the role of hydrated electron associated to the understanding of CO2 and O2 effects through time resolved radicals' measurement.
SN - 0094-2405
SN - 2473-4209
ER -