Monte Carlo calculation of beam quality correction factors in proton beams using FLUKA

Abstract

Purpose. To provide Monte Carlo calculated beam quality correction factors (k Q ) for monoenergetic proton beams using the Monte Carlo code fluka. Materials and methods. The Monte Carlo code fluka was used to calculate the dose absorbed in a water-filled reference volume and the air-filled cavities of six plane-parallel and four cylindrical ionization chambers. The chambers were positioned at the entrance region of monoenergetic proton beams with energies between 60 and 250 MeV. Based on these dose values, f Q as well as k Q factors were calculated while factors were taken from Andreo et al (2020 Phys. Med. Biol. 65 095011). Results. k Q factors calculated in this work were found to agree with experimentally determined k Q factors on the 1%-level, with only two exceptions with deviations of 1.4% and 1.9%. The comparison of f Q factors calculated using fluka with f Q factors calculated using the Monte Carlo codes geant4 and penh showed a general good agreement for low energies, while differences for higher energies were pronounced. For high energies, in most cases the Monte Carlo codes fluka and geant4 lead to comparable results while the f Q factors calculated with penh are larger. Conclusion. fluka can be used to calculate k Q factors in clinical proton beams. The divergence of Monte Carlo calculated k Q factors for high energies suggests that the role of nuclear interaction models implemented in the different Monte Carlo codes needs to be investigated in more detail.