OBJECTIVE: Therefore, in this study, we propose to validate a new Geant4-DNA chemistry module through the simulation of water radiolysis and Fricke dosimetry experiments on a proton preclinical beam line.
METHODS: In this study, we used the GATE Monte Carlo simulation platform (version 9.3) to simulate a 67.5 MeV proton beam produced with the ARRONAX isochronous cyclotron (IBA Cyclone 70XP) at conventional dose rate (0.2 Gy/s) to simulate the irradiation of ultra-pure liquid water samples and Fricke dosimeter. We compared the depth dose profile with measurements performed with a plane parallel Advanced PTW 34045 Markus ionization chamber. Then, a new Geant4-DNA chemistry application proposed from Geant4 version 11.2 has been used to assess the evolution of HO • ${\\mathrm{HO}}^ \\bullet $ , e aq - ${\\mathrm{e}}_{{\\mathrm{aq}}}^ - $ , H 3 O + ${{\\mathrm{H}}}_3{{\\mathrm{O}}}^ + $ , H 2 O 2 ${{\\mathrm{H}}}_2{{\\mathrm{O}}}_2$ , H 2 ${{\\mathrm{H}}}_2$ , HO 2 • ${\\mathrm{HO}}_2^ \\bullet $ , HO 2 - , O 2 • - ${\\mathrm{HO}}_2^ - ,{\\mathrm{\\ O}}_2^{ \\bullet - }$ and HO - ${\\mathrm{HO}}^ - $ reactive species along time until 1-h post-irradiation. In particular, the effect of oxygen and pH has been investigated through comparisons with experimental measurements of radiolytic yields for H 2 O 2 ${{\\mathrm{H}}}_2{{\\mathrm{O}}}_2$ and Fe3+.
RESULTS: GATE simulations reproduced, within 4%, the depth dose profile in liquid water. With Geant4-DNA, we were able to reproduce experimental H 2 O 2 ${{\\mathrm{H}}}_2{{\\mathrm{O}}}_2$ radiolytic yields 1-h post-irradiation in aerated and deaerated conditions, showing the impact of small changes in oxygen concentrations on species evolution along time. For the Fricke dosimeter, simulated G(Fe3+) is 15.97 ± 0.2 molecules/100 eV which is 11% higher than the measured value (14.4 ± 04 molecules/100 eV).
CONCLUSIONS: These results aim to be consolidated by new comparisons involving other radiolytic species, such as e aq - ${\\mathrm{e}}_{{\\mathrm{aq}}}^ - $ or , O 2 • - $,{\\mathrm{\\ O}}_2^{ \\bullet - }$ to further study the mechanisms underlying the FLASH effect observed at ultra-high dose rates (UHDR).
目标:因此,在这项研究中,我们建议通过在质子临床前束线上模拟水放射分解和Fricke剂量测定实验来验证新的Geant4-DNA化学模块。
方法:在本研究中,我们使用GATEMonteCarlo模拟平台(9.3版)模拟了用ARRONAX等时回旋加速器(IBACyclone70XP)以常规剂量率(0.2Gy/s)产生的67.5MeV质子束,以模拟超纯液态水样品和Fricke剂量计的辐照。我们将深度剂量分布与使用平面平行的高级PTW34045Markus电离室进行的测量进行了比较。然后,从Geant4版本11.2提出的新的Geant4-DNA化学应用程序已用于评估HO•${\\mathrm{HO}}^\\bullet$的演变,eaq-${\\mathrm{e}}_{{\\mathrm{aq}}}^-$,H3O+${\\mathrm{H}}}_3{{\\mathrm{O}}}^+$,H2O2${\\mathrm{H}}}_2{{\\mathrm{O}}}_2$,H2${{\\mathrm{H}}}_2$,HO2•${\\mathrm{HO}}_2^\\bullet$,HO2-,O2•-${\\mathrm{HO}}_2^-,{\\mathrm{\\O}}_2^{\\bullet-}$和HO-${\\mathrm{HO}}^-反应性物种沿着时间直到辐照后1小时。特别是,通过与H2O2${{\\mathrm{H}}}_2{{\\mathrm{O}}}_2$和Fe3+的放射产率的实验测量结果进行比较,研究了氧气和pH值的影响。
结果:复制了GATE模拟,4%以内,液态水中的深度剂量曲线。有了Geant4-DNA,我们能够重现实验H2O2${{\\mathrm{H}}}_2{{\\mathrm{O}}}_2$在曝气和脱气条件下辐照后1小时的辐射分解产量,显示氧气浓度的微小变化对物种随时间进化的影响。对于Fricke剂量计,模拟G(Fe3)为15.97±0.2分子/100eV,比测量值(14.4±04分子/100eV)高11%。
结论:这些结果旨在通过涉及其他放射性物种的新比较来巩固,例如eaq-${\\mathrm{e}}_{\\mathrm{aq}}^-$或,O2•-$,{\\mathrm{\\O}}_2^{\\bullet-}$进一步研究在超高剂量率(UHDR)下观察到的FLASH效应的潜在机制。