Published online by Cambridge University Press: 19 March 2013
A radiation transport code based on a Monte Carlo tool is used to simulate a protontherapy beamline designed to treat paediatric patients with intracranial tumours. Thetreatments are performed using the IBA gantry at the Proton Therapy Centre of the InstitutCurie. The treatment is undertaken at 178.16 MeV using the double scattering technique.The aim of this study is to present the Monte Carlo model of the transported proton beam,beamline and treatment room, as well as the experimental validation of the proton dosedistributions calculated by this model. The beamline components and the treatment room areaccurately modelled using the Monte Carlo code MCNPX. The proton source at the beamlineentrance is defined on the basis of IBA data, measurements and calculations. Measured andcalculated relative proton dose distributions in a water phantom are compared for thevalidation. Depth dose profiles, including pristine Bragg peaks and a spread–out Braggpeak, and lateral dose profiles are studied. A general good agreement was found betweencalculated and measured distributions with discrepancies of less than 2 mm. Relativeproton dose distributions are therefore considered to be correctly described by oursimulated geometry and proton source parameters. The Monte Carlo simulation will be usedsubsequently for radiation protection purposes: calculation of secondary neutron dosesreceived by treated patients of different ages.