Validation of recent Geant4 physics models for application in carbon ion therapy

Cancer treatment with energetic carbon ions has distinct advantages over proton or photon irradiation. In this paper we present a simulation model integrated into the Geant4 Monte Carlo toolkit (version 9.3) which enables the use of ICRU 73 stopping powers for ion transport calculations. For a few materials, revised ICRU 73 stopping power tables recently published by ICRU (P. Sigmund, A. Schinner, H. Paul, Errata and Addenda: ICRU Report 73 (Stopping of Ions Heavier than Helium), International Commission on Radiation Units and Measurements, 2009) were incorporated into Geant4, also covering media like water which are of importance in radiotherapeutical applications. We examine, with particular attention paid to the recent developments, the accuracy of current Geant4 models for simulating Bragg peak profiles of C-12 ions incident on water and polyethylene targets. Simulated dose distributions are validated against experimental data available in the literature, where the focus is on beam energies relevant to ion therapy applications (90-400 MeV/u). A quantitative analysis is performed which addresses the precision of the Bragg peak position and proportional features of the dose distribution. It is shown that experimental peak positions can be reproduced within 0.2% of the particle range in the case of water, and within 0.9% in the case of polyethylene. The comparisons also demonstrate that the simulations accurately render the full width at half maximum (FWHM) of the measured Bragg peaks in water. For polyethylene slight deviations from experimental peak widths are partly attributed to systematic effects due to a simplified geometry model adopted in the simulation setup. (C) 2010 Elsevier B.V. All rights reserved.