Youssef Saghir¶
Caractérisation à l’aide de modèles de Multiple Coulomb Scattering de l’impact d’éléments de mise en forme passifs sur les propriétés d’un faisceau de protons
Abstract¶
The specific nuclear and electronic interactions of charged particles with matter, particularly in terms of energy loss, coupled with advanced treatment planning methods, provide the benefits of proton therapy compared to conventional radiotherapy. Although the physical reality of the Bragg peak is a key element in hadron therapy, a detailed knowledge of scattering phenomena is crucial for the establishment of cutting-edge therapeutic methods. The aim of this work is to implement and validate a set of numerical methods allowing to take into account of scattering phenomena when modeling the transport of proton beams. We use the Fermi-Eyges formalism that models the scattering via the "scattering power" parameter, by analogy with the "stopping power" modeling the energy loss phenomenon. Multiple scattering power models exist and this study aims to implement them numerically, to validate them against data available in the littérature and to show that the "differential Moliere" model gives the best agreement with Monte-Carlo (Geant4) simulations. Afterwards, using this model, we apply our Fermi-Eyges implementation to the computation of the scattering effects in energy degraders and to passive scattering treatment systems (nozzles). As a main result we show the advantages of new degrader materials (boron carbide and diamond) in terms of transmitted beam emittance. By applying the code to the calculation of the parameters of a passive scattering eyeline treatment beamline, we can establish a relationship between the thickness of Tantalum (scatterer) and the size of the clinical field.