TY  - JOUR
AU  - Valdes-Cortez, C.
AU  - Mansour, I.
AU  - Rivard, M. J.
AU  - Ballester, F.
AU  - Mainegra-Hing, E.
AU  - Thomson, R. M.
AU  - Vijande, J.
PY  - 2021
DA  - 2021//
TI  - A study of Type B uncertainties associated with the photoelectric effect in low-energy Monte Carlo simulations
T2  - Phys. Med. Biol.
JO  - Physics in Medicine and Biology
SP  - 105014
EP  - 14pp
VL  - 66
IS  - 10
PB  - Iop Publishing Ltd
KW  - Monte Carlo simulations
KW  - brachytherapy
KW  - low energy physics
KW  - photoelectric effect
AB  - 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.
SN  - 0031-9155
UR  - https://arxiv.org/abs/2103.02874
UR  - https://doi.org/10.1088/1361-6560/abebfd
DO  - 10.1088/1361-6560/abebfd
LA  - English
N1  - WOS:000655291500001
ID  - Valdes-Cortez_etal2021
ER  -