Phase space files can store the particle information in one or more planes of radiation particles simulated by the Monte Carlo (MC) method. The secondary calculation method based on phase space files is commonly used to improve the efficiency of MC simulations. However, it is still unclear whether phase space files are applicable for microdosimetric evaluations. In this study, voxel-type and mesh-type monolayer cell population models of different sizes were constructed, and phase space files of secondary electrons generated by photons with different initial energies were obtained using the MC software -- PHITS. The overall average dose caused by the secondary electron phase space files in the region of interest and their microdosimetric distribution within cells were calculated and compared with the results caused by the initial photons under the same geometric conditions. The results showed that the adoption of secondary electron phase space files had almost no impact on the evaluation of macroscopic average dose, with deviations lower than 3% compared to the overall dose caused by the initial photons in the Petri dish. For microdosimetric distributions of the voxel-type model and the two different morphologies of mesh-type cell models, with a macroscopic accumulated dose of 1 mGy, the relative deviation of the cell dose distribution generated by the initial photons and the phase space files was below 10% and the total computation time of phase space files was below 2% of initial photon's. For accumulated doses of 10, 50, and 100 mGy, the relative deviation of the cell nucleus specific energy obtained by secondary electrons and initial photons was greater than 10%. As the size of the culture dish increased, the differences in cell dose distributions also increased, with the root mean square error (RMSE) and coefficient of variation (Cv) of dose distributions both exceeding 30%. In conclusion, this study assessed the effectiveness of the secondary calculation method utilizing phase space files for dose evaluation at the cellular scale. This research offers essential technical support and theoretical foundations for the utilization of this approach in microdosimetric investigations at the cellular level.

中文翻译：

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相空间文件二次计算方法在细胞剂量分布中的应用


相空间文件可以将粒子信息存储在由 Monte Carlo （MC） 方法模拟的一个或多个辐射粒子平面中。基于相空间文件的二次计算方法通常用于提高 MC 仿真的效率。然而，目前尚不清楚相空间文件是否适用于微观剂量学评估。在本研究中，构建了不同大小的体素型和网状单层细胞群模型，并使用 MC 软件 -- PHITS 获得了具有不同初始能量的光子产生的二次电子的相空间文件。计算了感兴趣区域中次级电子相空间文件引起的总体平均剂量及其在细胞内的微观剂量分布，并与相同几何条件下初始光子引起的结果进行了比较。结果表明，采用二次电子相空间文件对宏观平均剂量的评价几乎没有影响，与培养皿中初始光子引起的总剂量相比，偏差小于 3%。对于体素型模型的微观剂量分布和网状型单元模型的两种不同形态，在宏观累积剂量为 1 mGy 的情况下，初始光子和相空间文件产生的单元剂量分布的相对偏差低于 10%，相空间文件的总计算时间低于初始光子的 2%。对于 10、50 和 100 mGy 的累积剂量，二次电子和初始光子获得的细胞核比能量的相对偏差大于 10%。 随着培养皿尺寸的增加，细胞剂量分布的差异也增加，剂量分布的均方根误差 （RMSE） 和变异系数 （Cv） 均超过 30%。总之，本研究评估了利用相空间文件在细胞尺度上进行剂量评估的二次计算方法的有效性。这项研究为在细胞水平的显微剂量学研究中利用这种方法提供了重要的技术支持和理论基础。