Fano cavity test for electron Monte Carlo transport algorithms in magnetic fields: comparison between EGSnrc, PENELOPE, MCNP6 and Geant4

Abstract

A Fano cavity test was performed for four general-purpose Monte Carlo codes, EGSnrc, PENELOPE, MCNP6 and Geant4 to evaluate the accuracy of their electron transport algorithms in magnetic fields. In the simulations, a plane-parallel ionization chamber was modelled as a circular gas disk sandwiched between two circular solid wall disks. It was assumed that an isotropic and uniform line source per unit mass along the central axis of the gas and solid emits mono-energetic electrons with energies 0.01, 0.1, 1.0 and 3.0 MeV at different magnetic field strengths 0, 0.35, 1.0, 1.5 and 3.0 T in the electron transport mode (no Bremsstrahlung). The relative difference between the calculated dose to the gas region and the initial total energy of emitted electrons per unit mass was defined as the accuracy of Monte Carlo codes. In all results, EGSnrc with the enhanced electric and magnetic field (EEMF) macros was not considerably sensitive to the step size parameters and showed accuracy less than 0.18% ± 0.06% with a coverage factor k = 2. The other codes could not achieve competent accuracy with their default settings of step size parameters, compared to EGSnrc with the EEMF macros. With the step size parameters carefully selected, the accuracy of PENELOPE and MCNP6 was within 1.0% and 0.4%, respectively. However, Geant4 showed accuracy within 1.7% except in 3.0 T. EGSnrc with the EEMF macros achieved the best accuracy for the Fano test at the electron energies and the magnetic field strengths investigated in this study and thus, would be recommended to simulate dose responses of ionization chambers in the presence of magnetic fields.

Monte Carlo simulations of out‐of‐field skin dose due to spiralling contaminant electrons in a perpendicular magnetic field

“…In that work, it was recommended that EM ESTEPE, the parameter which limits the step size to ensure that the change in the direction of motion induced by the magnetic field is less than the set fractional value, should be set to 0.2. Recently, Lee et al . have found that the EGSnrc enhanced electric and magnetic field macros, which are used in this study, achieved the best accuracy in ion chamber Fano tests when compared to the magnetic field transport of PENELOPE, Geant4, and MCNP6.…”

Monte Carlo simulation of the effect of magnetic fields on brachytherapy dose distributions in lung tissue material

“…First, the TOPAS Monte Carlo model of the brachytherapy source was verified by comparing calculated TG43 parameters with data from the literature. Second, this work relies on the accuracy of Geant4 toolkit to model transport of charged particles in magnetic fields, which has been already shown experimentally [7,38,39] and theoretically [40,41]. Third, we relied on the TOPAS tool for the implementation of magnetic field, DICOM patient, detailed geometry and source of the brachytherapy seed, and scoring.…”

Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams

“…It applies the adaptive multipoint integration algorithm, and allows for proper boundary crossing. Lee et al reported that EGSnrc with the EEMF macros achieved the highest accuracy for the Fano cavity test under the field strengths of 0.35, 1.0, 1.5, and 3.0 T, compared with the MC codes of PENELOPE, MCNP6, and Geant4.…”

“…It applies the adaptive multipoint integration algorithm, and allows for proper boundary crossing. Lee et al 29 reported that EGSnrc with the EEMF macros achieved the highest accuracy for the Fano cavity test under the field strengths of 0.35, 1.0, 1.5, and 3.0 T, compared with the MC codes of PENELOPE, MCNP6, and Geant4. The depth parameter of the RGD was set to 1 cm, d max (depth of the maximum dose), 5, 10, 15, 20, and 25 cm for a 10 cm 9 10 cm field at the detector center in a solid water phantom (RMI-457, q = 1.042 g/cm 3 GAMMEX, USA), with the dimensions of 30 cm 9 30 cm 9 30 cm.…”