Dose calculations for clinical proton broad beams by GEANT4

Abstract

The aim of this work is to develop a dose calculation engine for clinical proton beams based on a Monte- Carlo code, GEANT4 (G4 dose engine), and to evaluate the dose distributions calculated by the engine by comparing with the measurements and the calculations of the pencil-beam algorithm (PBA). The beam delivery system at Hyogo Ion Beam Medical Center was modeled and implement in the G4 dose engine. Treatment parameters for patients were transferred to the dose engine by using DICOM-RTPlan interface employed at HIBMC. Physics processes were verified by examining the Bragg curves in water and the scattering in the scatterer and the range-shifter, and were confirmed to be implemented properly in the GEAN4. The dose calculations were then done by the G4 dose engine in a water phantom with the treatment parameters of a sample patient to verify the DICOM-RTPlan interface as well as the effect of the range compensator. The dose distributions were compared with the measurements, and the calculations and the measurements were in good agreement. The dose calculations on CT images of a patient were performed and were compared with the calculations by the PBA. The calculations were in good agreement but a small disagreement at the distal edge was seen, and was presumably caused by the heterogeneity of the patient. © 2009 Springer-Verlag.