Uehara S, Nikjoo H, Goodhead D T
School of Health Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan.
Radiat Res. 1999 Aug;152(2):202-13.
The purpose of this study was to make an intercomparison and assessment of cross sections for electrons in water used in electron track structure codes. This study is intended to shed light on the extent to which the differences between the input data and physical and chemical assumptions influence the outcome in biophysical modeling of radiation effects. Ionization cross sections and spectra of secondary electrons were calculated by various theories. The analyses were carried out for water vapor cross sections, as these are more abundant and readily available. All suitable published experimental total ionization cross sections were fitted by an appropriate function and used for generation of electron tracks. Three sets of compiled data were used for comparison of total excitation cross sections and mean excitation energy. The tracks generated by a Monte Carlo track code, using various combinations of cross sections, were compared in terms of radial distributions of interactions and point kernels. The spectrum of secondary electrons emitted by the ionization process was found to be the factor that has the most influence on these quantities. A different set of cross sections for excitation and elastic scattering did not affect the electron track structure as much as did ionization cross sections. It is concluded that all codes, using different cross sections and in different phase, currently used for biophysical modeling exhibit close similarities for energy deposition in larger size targets while appreciable differences are observed in B-DNA-size targets. We recommend fitted functions to all available suitable experimental data for the total ionization and elastic cross sections. We conclude that most codes produce tracks in reasonable agreement with the macroscopic quantities such as total stopping power and total yield of strand breaks. However, we predict differences in frequencies of clustering in tracks from the different models.
本研究的目的是对电子径迹结构代码中使用的水中电子截面进行相互比较和评估。本研究旨在阐明输入数据与物理和化学假设之间的差异在多大程度上影响辐射效应生物物理建模的结果。通过各种理论计算了电离截面和二次电子能谱。对水蒸气截面进行了分析，因为它们更为丰富且易于获取。所有合适的已发表实验总电离截面都用适当的函数进行拟合，并用于生成电子径迹。使用三组汇编数据比较总激发截面和平均激发能。使用蒙特卡罗径迹代码，利用不同截面组合生成的径迹，在相互作用的径向分布和点核方面进行了比较。发现电离过程中发射的二次电子能谱是对这些量影响最大的因素。与电离截面相比，另一组激发和弹性散射截面对电子径迹结构的影响没那么大。得出的结论是，目前用于生物物理建模的所有代码，使用不同的截面且处于不同的相，在较大尺寸靶中的能量沉积方面表现出密切的相似性，而在B - DNA尺寸的靶中观察到明显差异。我们建议对所有可用的合适实验数据的总电离和弹性截面采用拟合函数。我们得出结论，大多数代码生成的径迹与宏观量如总阻止本领和链断裂总产额合理一致。然而，我们预测不同模型的径迹中聚类频率存在差异。
