Modeling of scavenging systems in water radiolysis with Geant4-DNA. (April 2023)

• Record Type: Journal Article
• Authors: Chappuis, Flore; Grilj, Veljko; Tran, Hoang Ngoc; Zein, Sara A.; Bochud, François; Bailat, Claude; Incerti, Sébastien; Desorgher, Laurent
• Is Part Of: Physica medica. Volume 108(2023)
• Publication Date: 2023-04
• Subjects: Water radiolysis -- Scavenger -- Geant4-DNA -- FLASH effect; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2023.102549
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Extension of Geant4-DNA to provide a comprehensive framework for the use of scavengers. Presentation of an example in radiochemistry and another focused on radiobiology. Agreement between the step-by-step and the independent reaction times methods. Discussion of the oxygen depletion hypothesis proposed to explain the FLASH effect. Abstract: Purpose: This paper presents the capabilities of the Geant4-DNA Monte Carlo toolkit to simulate water radiolysis with scavengers using the step-by-step (SBS) or the independent reaction times (IRT) methods. It features two examples of application areas: (1) computing the escape yield of H 2 O 2 following a 60 Co γ-irradiation and (2) computing the oxygen depletion in water irradiated with 1 MeV electrons. Methods: To ease the implementation of the chemical stage in Geant4-DNA, we developed a user interface that helps define the chemical reactions and set the concentration of scavengers. The first application area example required two computational steps to perform water radiolysis using N O 2 - and N O 3 - as scavengers and a 60 Co irradiation. The oxygen depletion computation technique for the second application area example consisted of simulating track segments of 1 MeV electrons and determining the radio-induced loss and gain of oxygen molecules. Results: The production of H 2 O 2 under variable scavenging levels is consistent with the literature; the mean relative difference between the SBS and IRT methods is 7.2 % ± 0.5 %. For the oxygen depletion 1 µs post-irradiation, the mean relative difference between both methods is equal to 9.8 % ± 0.3 %. The results in the microsecond scale depend on the initial partial pressure of oxygen in water. In addition, the computed oxygen depletions agree well with the literature. Conclusions: The Geant4-DNA toolkit makes it possible to simulate water radiolysis in the presence of scavengers. This feature offers perspectives in radiobiology, with the possibility of simulating cell-relevant scavenging mechanisms.