Microdosimetric calculations of the direct DNA damage induced by low energy electrons using the Geant4-DNA Monte Carlo code
Microdosimetric calculations of the direct DNA damage induced by low energy electrons using the Geant4-DNA Monte Carlo code
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DOI：
10.1088/1361-6560/ab6b47
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发表时间：
2020-02-01
影响因子：
3.5
通讯作者：
Emfietzoglou, Dimitris
中科院分区：
文献类型：
--
作者：
Margis, Stefanos;Magouni, Maria;Emfietzoglou, Dimitris
利用Monte Carlo产生的纳米尺度微剂量谱计算低能电子对DNA的直接损伤产额，并考察不同模拟输入的影响。经典的微剂量学提供了一个可行的和更简单的替代更复杂的机械方法的实际应用的潜力进行了讨论。使用Geant 4 Monte Carlo工具包的Geant 4-DNA低能扩展的轨道结构模拟用于计算与双链断裂（DSB）诱导相关的尺寸的球形体积中的线性能谱。根据文献中DNA损伤的阈值能量，利用微剂量谱计算了简单DSB和成簇DSB的产率。Geant 4-DNA中液态水介电函数的不同实现的影响（选项2和选项4构造器），以及粒子跟踪截止能量和目标尺寸的影响进行了检查。在2，2.3，2.6和3.4 nm直径的液态水球体中的频率和剂量平均线性能量，以及，对于100 eV至100 keV能量范围内的电子，给出了简单和成簇DSB/戈伊/电池的数量。应用几种常用的跟踪截止能量（10、20、50、100 eV），给出了Geant 4-DNA的“默认”（选项2）和“约阿尼纳”（选项4）物理模型的结果。总体而言，物理模型和靶直径的选择对DSB产率具有中等影响（高达类似于10%-30%），而跟踪截止能量的影响可能是显著的（>100%）。重要的是，发现简单和簇DSB的产率随电子能量在所检查的范围内显著变化（2倍或更多）。电子诱导的简单和簇DSB的产率在100 eV-100 keV范围内表现出强烈的能量依赖性，这与辐射质量问题有关。结果表明，一个经典的微剂量学方法的基础上线性能谱在纳米尺寸的目标DNA损伤的计算预测计算密集的机械方法，使用详细的原子DNA几何形状的结果相当，因此，提供了一个相对简单和强大的替代一些实际应用。
To calculate the yield of direct DNA damage induced by low energy electrons using Monte Carlo generated microdosimetric spectra at the nanometer scale and examine the influence of various simulation inputs. The potential of classical microdosimetry to offer a viable and simpler alternative to more elaborate mechanistic approaches for practical applications is discussed. Track-structure simulations with the Geant4-DNA low-energy extension of the Geant4 Monte Carlo toolkit were used for calculating lineal energy spectra in spherical volumes with dimensions relevant to double-strand-break (DSB) induction. The microdosimetric spectra were then used to calculate the yield of simple and clustered DSB based on literature values of the threshold energy of DNA damage. The influence of the different implementations of the dielectric function of liquid water available in Geant4-DNA (Option 2 and Option 4 constructors), as well as the effect of particle tracking cutoff energy and target size are examined.Frequency- and dose-mean lineal energies in liquid-water spheres of 2, 2.3, 2.6, and 3.4 nm diameter, as well as, number of simple and clustered DSB/Gy/cell are presented for electrons over the 100 eV to 100 keV energy range. Results are presented for both the 'default' (Option 2) and 'Ioannina' (Option 4) physics models of Geant4-DNA applying several commonly used tracking cutoff energies (10, 20, 50, 100 eV). Overall, the choice of the physics model and target diameter has a moderate effect (up to similar to 10%-30%) on the DSB yield whereas the effect of the tracking cutoff energy may be significant (>100%). Importantly, the yield of both simple and clustered DSB was found to vary significantly (by a factor of 2 or more) with electron energy over the examined range.The yields of electron-induced simple and clustered DSB exhibit a strong energy dependence over the 100 eV-100 keV range with implications to radiation quality issues. It is shown that a classical microdosimetry approach for the calculation of DNA damage based on lineal energy spectra in nanometer-size targets predicts comparable results to computationally intensive mechanistic approaches which use detailed atomistic DNA geometries, thus, offering a relatively simple and robust alternative for some practical applications.