Validation and investigation of reactive species yields of Geant4-DNA chemistry models
Validation and investigation of reactive species yields of Geant4-DNA chemistry models
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DOI：
10.1002/mp.13332
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发表时间：
2019-02-01
期刊：
影响因子：
3.8
通讯作者：
Bezak, Eva
中科院分区：
文献类型：
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作者：
Peukert, Dylan;Incerti, Sebastien;Bezak, Eva
目的水辐解反应中产生的活性物质是低线性能量转移（LET）辐射生物效应的主要来源。模拟水辐解和随后的反应物种的相互作用，以及轨道结构，是必不可少的微尺度上的放射性生物学模型。最近，已经开发了Geant 4-DNA的化学模型，以与现有的综合物理模型结合使用。在目前的工作中，第一个详细的，独立的，在硅片验证所有物种的产量与发表的实验观察和比较与其他放射生物学模拟。此外，质子和较重离子的LET对模型中反应性物种产率的影响被检查，以及在模型中模拟的物理相互作用之后的时间内辐解之后的化学反应的完整性。和离子与各种LET使用Geant 4和RITRACKS模拟工具。使用Geant 4模拟水的解离和复合，以确定在模拟结束时化学反应的完整性。通过将使用Geant 4模拟的产率与实验观察和其他模拟进行比较来进行产率验证。验证进行低LET辐射和高LETions.ResultsIt的溶剂化电子和羟基自由基的所有物种被发现，Geant 4-DNA化学产率一般与实验观察和其他模拟良好的协议。然而，发现在化学阶段结束时羟基自由基和过氧化氢的Geant 4-DNA产率分别显著高于和低于实验观察到的产率。增加入射强子的LET会增加次级粒子的产额，而减少初级粒子的产额。用Geant 4模拟了100 ns时LET对羟基自由基产率的影响，结果与实验测量结果吻合较好。此外，到年底的模拟只有40%的解离水分子已经重组和重组的速度放缓。ConclusionsThe产量模拟使用Geant 4是合理的协议与实验观察。较高的LET辐射对应于次生物种产量的增加和初级物种产量的减少。这些趋势与LET具有类似的影响，对100纳秒的羟基自由基产率的Geant 4和实验测量相结合，表明Geant 4准确地模拟了LET对辐解产率的影响。模拟化学阶段内的有限重组和阶段结束时的重组速率减慢表明潜在的远程间接生物损伤。
PurposeIndirect biological damage due to reactive species produced in water radiolysis reactions is responsible for the majority of biological effect for low linear energy transfer (LET) radiation. Modeling water radiolysis and the subsequent interactions of reactive species, as well as track structures, is essential to model radiobiology on the microscale. Recently, chemistry models have been developed for Geant4-DNA to be used in combination with the comprehensive existing physics models. In the current work, the first detailed, independent, in silico validation of all species yields with published experimental observations and comparison with other radiobiological simulations is presented. Additionally, the effect of LET of protons and heavier ions on reactive species yield in the model was examined, as well as the completeness of the chemical reactions following the radiolysis within the time after physical interactions simulated in the model.MethodsYields over time of reactive species were simulated for water radiolysis by incident electrons, protons, alpha particles, and ions with various LETs using Geant4 and RITRACKS simulation tools. Water dissociation and recombination was simulated using Geant4 to determine the completeness of chemical reactions at the end of the simulation. Yield validation was performed by comparing yields simulated using Geant4 with experimental observations and other simulations. Validation was performed for all species for low LET radiation and the solvated electron and hydroxyl radical for high LET ions.ResultsIt was found that the Geant4-DNA chemistry yields were generally in good agreement with experimental observations and other simulations. However, the Geant4-DNA yields for the hydroxyl radical and hydrogen peroxide at the end of the chemistry stage were found to be respectively considerably higher and lower than the experimentally observed yields. Increasing the LET of incident hadrons increased the yield of secondary species and decreased the yield of primary species. The effect of LET on the yield of the hydroxyl radical at 100ns simulated with Geant4 was in good agreement with experimental measurements. Additionally, by the end of the simulation only 40% of dissociated water molecules had been recombined and the rate of recombination was slowing.ConclusionsThe yields simulated using Geant4 are within reasonable agreement with experimental observations. Higher LET radiation corresponds with increased yields of secondary species and decreased yields of primary species. These trends combined with the LET having similar effects on the 100ns hydroxyl radical yield for Geant4 and experimental measurements indicate that Geant4 accurately models the effect of LET on radiolysis yields. The limited recombination within the modeled chemistry stage and the slowing rate of recombination at the end of the stage indicate potential long-range indirect biological damage.