Uncertainties in the relative biological effectiveness (RBE) of proton remains a major barrier to the biological optimization of proton therapy. A large amount of experimental data suggest that proton RBE is variable. As an evolving Monte Carlo code toolkit, Geant4-DNA is able to simulate the initial DNA damage caused by particle beams through physical and chemical interactions at the nanometer scale over a short period of time. This contributes to evaluating the radiobiological effects induced by ionizing radiation. Based on the Geant4-DNA toolkit, this study constructed a DNA geometric model containing 6.32Gbp, simulated the relationship between radiochemical yields (G-values) and their corresponding chemical constructors, and calculated a detailed calculation of the sources of damage and the complexity of damage in DNA strand breaks. The damage model constructed in this study can simulate the relative biological effectiveness (RBE) in the proton Bragg peak region. The results indicate that: (1) When the electron energy is below 400 keV, the yield of OH^· account for 18.1% to 25.3% of the total water radiolysis yields. (2) Under the influence of histone clearance function, the yield of indirect damage account for over 72.93% of the yield of DNA strand breaks (SBs). When linear energy transfer (LET) increased from 29.79 (keV/μm) to 64.29 (keV/μm), the yield of double strand breaks (DSB) increased from 17.27% to 32.65%. (3) By investigating the effect of proton Bragg peak depth on the yield of direct DSB (DSB_direct) and total DSB (DSB_total), the RBEDSBtot and RBEDSBdir levels of cells show that the RBE value of protons reaches 2.2 in the Bragg peak region.

中文翻译：

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基于 Geant4 诱导 DNA 双链断裂的质子相对生物有效性

质子相对生物有效性（RBE）的不确定性仍然是质子治疗生物优化的主要障碍。大量实验数据表明质子RBE是可变的。作为一个不断发展的蒙特卡罗代码工具包，Geant4-DNA能够在短时间内通过纳米尺度的物理和化学相互作用来模拟粒子束引起的初始DNA损伤。这有助于评估电离辐射引起的放射生物学效应。本研究基于Geant4-DNA工具包，构建了包含6.32Gbp的DNA几何模型，模拟了放射化学产率（G值）与其对应的化学构造子之间的关系，并详细计算了损伤来源和复杂程度。 DNA 链断裂造成的损伤。本研究构建的损伤模型可以模拟质子布拉格峰区域的相对生物有效性（RBE）。结果表明：(1)当电子能量低于400 keV时，OH ^·的产率占水辐解总产率的18.1%～25.3%。 (2)在组蛋白清除功能的影响下，间接损伤的发生率占DNA链断裂(SBs)发生率的72.93%以上。当线性能量转移（LET）从 29.79（keV​​/μm) 至 64.29 (keV/μm)，双链断裂(DSB)的产率从17.27%增加到32.65%。 (3) 通过考察质子布拉格峰深度对直接 DSB (DSB _direct ) 和总 DSB (DSB _Total )产率的影响， RBEDS乙t哦t 和 RBEDS乙d我r 细胞水平显示质子的RBE值在布拉格峰区域达到2.2。