Sciences & Société
Soutenance de thèse : Alessio ELIA
Characterization of the GATE Monte Carlo platform for nonisocentric treatments and patient specific treatment plan verification at MedAustron
Doctorant : Alessio ELIA
Laboratoire INSA : CREATIS
Ecole doctorale : ED160 : E.E.A
For independent dose recalculation by means of a Monte Carlo particle transport code, a beam model for the MedAustron Ion Therapy Centre has been developed in the entire clinical energy range (from 62.4 up to 252.7 MeV). The proposed model allows for accurate dose calculations in non-isocentric treatment conditions as well as for superficial tumor treatments, where a range shifter (RaShi) has to be used. Furthermore, the secondary particle spectra is modeled as particles were tracked through the entire treatment head.
The beam model was derived and validated on measured lateral dose profiles in air at several distances from the isocencer in terms of spot sizes, beam diverge and beam emittance of the proton pencil beam at the nozzle entrance. Energy and momentum spread were optimized to match measurements. The number of particles to absolute dose was calibrated against the dose-area product at reference conditions in the dose plateau. The dose calculation accuracy for different clinical scenarios was benchmarked against cubic uniform dose distributions of varying side lengths and depths. Finally, a set of clinical cases of particular interest were recalculated by the MC dose simulation in water, in order to reproduce the patient specific quality assurance methodology.
For all energies, the FWHM in air and the ranges agrees better than 1mm/10% and 0.2 mm with measurements, respectively. Whenever the RaShi is considered in the beam path, agreement generally decreased only about small %. The simulated dose cubes were in average +2.7% off from measurements and was therefore rescaled by this factor. For the patient specific QA average agreement was -0.3%.