Contribution to the study of nuclear processes in hadrontherapy and of their impact on dose deposition delocalization

Hadrontherapy consists of the use of heavy particles (hadrons) for treatment of radio-resistant or/and inoperable cancerous tumors. The aim is to deposit the necessary dose, in the tumor volume, to sterilize the cancerous cells while spearing the surrounding volumes. Dose deposition is mainly due to the electromagnetic interactions between the incoming beam particles and the target material leading principally to ionizations of the target molecular or atomic constituents. However, light nuclear fragments, issued from the nuclear interactions between the projectile and the target nuclei, do also contribute to the dose deposition. Even thought the amount of the later is small (few % of the total dose), its quantification is crucial since it is the main contribution to the dose delocalization out of the aimed target volume. This quantification is difficult because of the lack of experimental cross-sections at the energies used in hadrontherapy: a few tens or hundreds of MeV per nucleon of the projectile. The principal aim of this work is to develop a method in order to predict the dose distribution effectively delivered in the real conditions of therapeutic irradiation. Two complementary approaches were followed for this work. The first, phenomenological, consists of the study and the compilation of the existing experimental data available in the literature and the improvement of an empirical nuclear fragmentation cross-sections model. The second approach is purely experimental and consisted in two campaigns of data acquisition, measurement of β⁺ emitters profile in a water target irradiated by carbon ions at GANIL (Caen) using techniques of positron emission tomography, and acquisition of longitudinal and transversal dose distributions in carbon and water equivalent (PMMA) targets irradiated by protons at the PSI (Villigen) facility. Then a method of data analysis to compare the predictions of the Monte Carlo simulations to the measurements were developed. (author)