Monte Carlo modeling and validation of a proton treatment nozzle by using the Geant4 toolkit

Modern commercial treatment planning systems for proton therapy use the pencil beam algorithm for calculating the absorbed dose. Although it is acceptable for clinical radiation treatment, the accuracy of this method is limited. Alternatively, the Monte Carlo method, which is relatively accurate in dose calculations, has been applied recently to proton therapy. To reduce the remaining uncertainty in proton therapy dose calculations, in the present study, we employed Monte Carlo simulations and the Geant4 simulation toolkit to develop a model for a of a proton treatment nozzle. The results from a Geant4-based medical application of the proton treatment nozzle were compared to the measured data. Simulations of the percentage depth dose profiles showed very good agreement within 1 mm in distal range and 3 mm in modulated width. Moreover, the lateral dose profiles showed good agreement within 3% in the central region of the field and within 10% in the penumbra regions. In this work, we proved that the Geant4 Monte Carlo model of a proton treatment nozzle could be used to the calculate proton dose distributions accurately.