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

Purpose.To provide Monte Carlo calculated beam quality correction factors (kQ) for monoenergetic proton beams using the Monte Carlo codefluka.Materials and methods.The Monte Carlo codeflukawas 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,fQas well askQfactors were calculated whilefQ0factors were taken from Andreoet al(2020Phys. Med. Biol.65095011).Results. kQfactors calculated in this work were found to agree with experimentally determinedkQfactors on the 1%-level, with only two exceptions with deviations of 1.4% and 1.9%. The comparison offQfactors calculated usingflukawithfQfactors calculated using the Monte Carlo codesgeant4 andpenhshowed a general good agreement for low energies, while differences for higher energies were pronounced. For high energies, in most cases the Monte Carlo codesflukaandgeant4 lead to comparable results while thefQfactors calculated withpenhare larger.Conclusion.flukacan be used to calculatekQfactors in clinical proton beams. The divergence of Monte Carlo calculatedkQfactors 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.