A study of the beam quality correction factor in clinical proton beam conditions using Monte Carlo simulations

When measuring the absorbed dose from a proton beam, the beam quality correction factor provided by IAEA TRS-398 has been used. However, that factor calculates the absorbed dose by applying the same value to clinical dosimetry without considering the initial energy of the radiation particle or the energy spectrum at the measurement position. In this study, the beam quality correction factors for the PTW 30013 farmer chamber and the PTW Advanced Markus chamber are calculated by using the TOPAS Monte Carlo simulation program to implement various clinical proton beam conditions of the National Cancer Center. In both chamber simulations, the quality correction factor measured at the Spread-Out Bragg Peak (SOBP) region shows a good agreement with the quality correction factors suggested by TRS-398. However, the quality correction factor increases at a single Bragg Peak region by 2.4% for the PTW Advanced Markus chamber and 7.1% for the PTW 30013 farmer chamber in the clinical dosimetry scenarios. The precise measurement of beam quality correction factors for mono-energy proton beams using the Monte Carlo technique is required in future studies.