Title: A study of Type B uncertainties associated with the photoelectric effect in low-energy Monte Carlo simulations Show Chinese title

Title: 关于低能蒙特卡罗模拟中光电效应相关类型B不确定性的研究

Abstract: The goal of this manuscript is to estimate Type B uncertainties in absorbed-dose calculations arising from the different implementations in current state-of-the-art Monte Carlo codes of low-energy photon cross-sections (<200 keV). Monte Carlo simulations are carried out using three codes widely used in the low-energy domain: PENELOPE-2018, EGSnrc, and MCNP. Mass energy-absorption coefficients for water, air, graphite, and their respective ratios; absorbed dose; and photon-fluence spectra are considered. Benchmark simulations using similar cross-sections have been performed. The differences observed between these quantities when different cross-sections are considered are taken to be a good estimator for the corresponding Type B uncertainties. A conservative Type B uncertainty for the absorbed dose (k=2) of 1.2%-1.7% (<50 keV), 0.6%-1.2% (50-100 keV), and 0.3% (100-200 keV) is estimated. The photon-fluence spectrum does not present clinically relevant differences that merit considering additional Type B uncertainties except for energies below 25 keV, where a Type B uncertainty of 0.5% is obtained. Below 30 keV, mass energy-absorption coefficients show Type B uncertainties (k=2) of about 1.5% (water and air), and 2% (graphite), reaching values about 1% (40-50 keV) and 0.5% (50-75 keV). Type B uncertainties for the water-to-graphite ratios are observed for energies below 30 keV, about 0.7% (k=2). In contrast with the intermediate (about 500 keV) or high (about 1 MeV) energy domains, Type B uncertainties due to the different cross-sections implementation cannot be considered subdominant with respect to Type A uncertainties or even to other sources of Type B uncertainties. Therefore, the values reported here should be accommodated within the uncertainty budget in low-energy photon dosimetry studies. Show Chinese abstract

Abstract: 本文的目的是估算在当前最先进的蒙特卡罗代码中低能光子截面的不同实现所引起的吸收剂量计算中的B类不确定度（<200 keV）。使用三种在低能领域广泛使用的代码进行蒙特卡罗模拟：PENELOPE-2018、EGSnrc和MCNP。考虑了水、空气、石墨及其相应比值的质量能量吸收系数；吸收剂量；以及光子通量谱。进行了使用相似截面的基准模拟。当考虑不同截面时，这些量之间的差异被视为相应B类不确定度的良好估计。估计了吸收剂量的保守B类不确定度（k=2）为1.2%-1.7%（<50 keV）、0.6%-1.2%（50-100 keV）和0.3%（100-200 keV）。光子通量谱在低于25 keV的能量下没有临床上相关的差异，因此无需考虑额外的B类不确定度，此时得到的B类不确定度为0.5%。低于30 keV时，质量能量吸收系数显示出B类不确定度（k=2）约为1.5%（水和空气），以及2%（石墨），在40-50 keV时达到约1%，在50-75 keV时达到约0.5%。在低于30 keV的能量下观察到水与石墨比值的B类不确定度，约为0.7%（k=2）。与中间（约500 keV）或高能（约1 MeV）领域相反，由于不同截面实现导致的B类不确定度不能被视为相对于A类不确定度或其他B类不确定度的次级因素。因此，此处报告的数值应在低能光子剂量学研究的不确定度预算中予以考虑。