Preliminary modelling for the Proton Boron Capture Therapy (PBCT)

Radiotherapy is one of the most common treatments received nowadays for tumour control. Heavy particles use, compared to photons, is one of the most fast-growing techniques, as it grants great tumour control saving healthy tissues as well. The most used ions are protons and 12C. The former have an efficiency close to photons (they are usually considered only 10% more effective), whereas the latter are usually more effective and are recommended especially for radiation resistant tumours. Nev- ertheless, proton facilities and treatments cost far less than carbon ones, therefore many radiotherapy enhancements have been theorized and analyzed over the last decades in order to improve the quality of cheaper techniques to obtain results similar to expensive ones. In this thesis work, an innovative technique for protontherapy enhancement, called Proton Boron Capture Therapy (PBCT), will be briefly discussed and studied. The idea is to exploit a nuclear reaction involving 11B that produces three high LET alpha particles that could enhance protons lethality: if a boron-containing drug is located close to tumour cells, the occurrence of this reaction should permit effective treatment also of radiation resistant tumours. Moreover the shape of the cross section as a function of incoming proton energy, should grant an enhancement only in the tumour region while saving healthy tissues. The biological effectiveness of this technique has already been published. In this work both an experimental approach (using techniques such as clonogenic assay) and a mod- elling approach (using mainly TALYS and Geant4 toolkits) are discussed. Moreover, a semi-analytical study permitted to understand whether the exploited reaction was responsible for the enhancement of biological effectiveness or not. The results of this thesis suggest that alpha particles creation, due to p + 11B, cannot explain the experimental increase of radiation lethality. Nevertheless, some of the tools obtained can still be used for future studies of this technique. In chapter 1 a brief introduction on radiotherapy will be given, together with some information about protontherapy and radiotherapy enhancement; in chapter 2 experimental facilities and methods will be presented; in chapter 3 some experimental results will be described and discussed; in chapter 4 the computational methods which have been used will be described and in chapter 5 the software that have been written will be described and discussed, as well as with the results obtained from simulations. In chapter 6 a conclusion to this thesis work will be given, and in Appendix A a description of some libraries (ParticleHP) used in this thesis can be found.