Modeling the effect of oxygen on the chemical stage of water radiolysis using GPU-based microscopic Monte Carlo simulations, with an application in FLASH radiotherapy.
Modeling the effect of oxygen on the chemical stage of water radiolysis using GPU-based microscopic Monte Carlo simulations, with an application in FLASH radiotherapy.
复制标题
使用基于GPU的显微镜蒙特卡洛模拟对氧对氧气的影响进行建模，并在闪光放射疗法中应用。
DOI：
10.1088/1361-6560/abc93b
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发表时间：
2021-01-26
影响因子：
3.5
通讯作者：
Chi Y
中科院分区：
文献类型：
--
作者：
Lai Y;Jia X;Chi Y
氧在决定电离辐射引起的初始DNA损伤中起着关键作用。对水辐射分解过程中的氧效应进行机械模拟具有重要意义。然而，由于多体相互作用问题的计算成本，在使用常见的微观蒙特卡罗工具进行模拟时，氧经常被忽略或视为一个恒定的连续统辐射分解-清除背景。在这项工作中，我们报告了基于我们最初开发的基于开源图形处理单元（GPU）的MC模拟工具gMicroMC，在明确考虑氧效应的水辐射分解化学阶段建模方面的最新进展。氧的加入主要降低了eh和H·化学自由基的产率，使它们变成剧毒的物种。为了证明gMicroMC在大规模模拟问题中的实用价值，我们应用支持氧模拟的gMicroMC计算高瞬时剂量率下化学自由基的产率，研究FLASH放疗中的氧耗尽假设。由于反应概率的降低，氧气消耗速率（OCR）的降低与初始氧浓度水平的降低有关。在剂量率方面，当氧浓度为21%，电子能量为4.5 keV时，在106、107 Gy/s时，OCR基本保持不变（~0.22 μM/Gy），在108 Gy/s时，OCR降至0.19 μM/Gy，这是因为增加的剂量率提高了自由基之间的相互反应频率，从而减少了自由基与氧的反应。我们计算了在闪光灯照射下氧浓度的时间演变。在剂量率为107 Gy/s，初始氧浓度为0.01%~21%的情况下，累计剂量为30 Gy （FLASH实验的典型剂量），氧不太可能完全耗尽。通过模拟等量自由基对Geant4-DNA的基准工作，评价了gMicroMC在考虑化学阶段氧分子时的计算效率。在初始氧浓度为3%（~105个分子）的情况下，gMicroMC在单个GPU卡上的加速系数比在单个CPU上的Geant4-DNA提高了1228倍。
Oxygen plays a critical role in determining the initial DNA damages induced by ionizing radiation. It is important to mechanistically model the oxygen effect in the water radiolysis process. However, due to the computational costs from the many body interaction problem, oxygen is often ignored or treated as a constant continuum radiolysis-scavenger background in the simulations using common microscopic Monte Carlo tools. In this work, we reported our recent progress on the modeling of the chemical stage of the water radiolysis with an explicit consideration of the oxygen effect, based upon our initial development of an open-source graphical processing unit (GPU)-based MC simulation tool, gMicroMC. The inclusion of oxygen mainly reduces the yields of eh and H· chemical radicals, turning them into highly toxic and species. To demonstrate the practical value of gMicroMC in large scale simulation problems, we applied the oxygen-simulation-enabled gMicroMC to compute the yields of chemical radicals under a high instantaneous dose rate to study the oxygen depletion hypothesis in FLASH radiotherapy. A decreased oxygen consumption rate (OCR) was found associated with a reduced initial oxygen concentration level due to reduced probabilities of reactions. With respect to dose rate, for the oxygen concentration of 21% and electron energy of 4.5 keV, OCR remained approximately constant (~0.22 μM/Gy) for ’s of 106, 107 Gy/s and reduced to 0.19 μM/Gy at 108 Gy/s, because the increased dose rate improved the mutual reaction frequencies among radicals, hence reducing their reactions with oxygen. We computed the time evolution of oxygen concentration under the FLASH irradiation setups. At the dose rate of 107 Gy/s and initial oxygen concentrations from 0.01%~21%, the oxygen is unlikely to be fully depleted with an accumulative dose of 30 Gy, which is a typical dose used in FLASH experiments. The computational efficiency of gMicroMC when considering oxygen molecules in the chemical stage was evaluated through benchmark work to Geant4-DNA with simulating an equivalent number of radicals. With an initial oxygen concentration of 3% (~105 molecules), a speedup factor of 1228 was achieved for gMicroMC on a single GPU card when comparing with Geant4-DNA on a single CPU.
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影响因子：
3.5
作者：
Grimes DR;Fletcher AG;Partridge M
通讯作者：
Partridge M
影响因子：
5.7
作者：
Montay-Gruel, Pierre;Bouchet, Audrey;Vozenin, Marie-Catherine
通讯作者：
Vozenin, Marie-Catherine
影响因子：
5.7
作者：
Montay-Gruel, Pierre;Petersson, Kristoffer;Vozenin, Marie-Catherine
通讯作者：
Vozenin, Marie-Catherine
影响因子：
1.4
作者：
Grimes DR;Partridge M
通讯作者：
Partridge M
影响因子：
3.1
作者：
LONGMUIR, IS;MARTIN, DC;SUN, S
通讯作者：
SUN, S