Purpose. To estimate Type B uncertainties in absorbed-dose calculations arising from the different implementations in current state-of-the-art Monte Carlo (MC) codes of low-energy photon cross-sections (<200 keV). Methods. MC simulations are carried out using three codes widely used in the low-energy domain: PENELOPE-2018, EGSnrc, and MCNP. Three dosimetry-relevant quantities are considered: mass energy-absorption coefficients for water, air, graphite, and their respective ratios; absorbed dose; and photon-fluence spectra. The absorbed dose and the photon-fluence spectra are scored in a spherical water phantom of 15 cm radius. 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. Results. 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), diminishing in all materials for larger energies and reaching values about 1% (40–50 keV) and 0.5% (50–75 keV). With respect to their ratios, the only significant Type B uncertainties are observed in the case of the water-to-graphite ratio for energies below 30 keV, being about 0.7% (k=2). Conclusions. 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 (tally volume averaging, manufacturing tolerances, etc). Therefore, the values reported here should be accommodated within the uncertainty budget in low-energy photon dosimetry studies.

目的。估计由当前最先进的低能光子横截面 (<200 keV) 的蒙特卡罗 (MC) 代码的不同实现引起的吸收剂量计算中的 B 类不确定性。方法。MC 模拟是使用在低能量领域广泛使用的三种代码进行的：PENELOPE-2018、EGSnrc 和 MCNP。考虑了三个与剂量学相关的量：水、空气、石墨的质量能量吸收系数及其各自的比率；吸收剂量；和光子通量光谱。吸收剂量和光子通量光谱在半径 15 cm 的球形水体模中进行评分。已经执行了使用类似横截面的基准模拟。当考虑不同的横截面时，这些量之间观察到的差异被认为是相应 B 类不确定性的良好估计。结果。吸收剂量的保守 B 类不确定性 ( k=2) 估计为 1.2%–1.7% (<50 keV)、0.6%–1.2% (50–100 keV) 和 0.3% (100–200 keV)。除了能量低于 25 keV 外，光子通量谱不存在值得考虑额外 B 型不确定性的临床相关差异，其中获得 0.5% 的 B 型不确定性。低于 30 keV，质量能量吸收系数显示 B 类不确定性 ( k = 2) 约为 1.5%（水和空气）和 2%（石墨），在所有材料中为较大能量递减并达到约 1% (40 –50 keV) 和 0.5% (50–75 keV)。关于它们的比率，在能量低于 30 keV 的水与石墨比率的情况下，观察到的唯一显着的 B 类不确定性约为 0.7% ( k = 2)。结论。与中等（约 500 keV）或高（约 1 MeV）能量域相比，由于不同横截面的实施，B 类不确定性不能被视为对 A 类不确定性或什至其他 B 类不确定性来源的次要地位（计数体积平均、制造公差等）。因此，此处报告的值应包含在低能光子剂量学研究的不确定性预算内。