Modelling and simulation of physics processes for in-beam imaging in hadrontherapy

Hadrontherapy is taking an increasingly important role in radiotherapy thanks to the ballistic properties of ions and, for those heavier than protons, an enhancement in the relative biological effectiveness in the tumour region. These features allow for a higher tumour conformality possible and gives the opportunity to tackle the problem of radioresistant tumours. However, they may lead to a great sensitivity of ion range to treatment uncertainties, namely to morphological changes along their path. In view of this, the detection of secondary radiations emitted after nuclear interactions between the incoming ions and the patient have been long proposed as ion range probes and, in this regard, positron emitters and prompt gammas have been the matter of intensive research. The European training network ENTERVISION, supported by the ENLIGHT community, was created in the end of 2009 in order to develop such imaging techniques and more generally to address treatment uncertainties during hadrontherapy. The present work is one of the many resulting from this project, under the subject 'Modelling and simulation of physics processes for in-beam imaging in hadrontherapy'. Despite the extensive range of the topic, the purpose was always to make a systematic study towards the clinical implementation of a prompt-gamma imaging device to be used for both proton and carbon ion treatments. In respect to the imaging device design, the focus of this work has been on the multi-slit collimated camera due to its simplicity in concept and proven feasibility from previous studies. This is a collaborative work, initiated within the ETOILE project, with the aim of providing reliable data concerning prompt-gamma emission yields both with homogeneous and heterogeneous targets, Geant4 Monte Carlo simulations accuracy, improvement and acceleration, and camera design optimisation. It comprises experimental data collected at GANIL (Caen), GSI (Darmstadt), HIT (Heidelberg), and WPE (Essen), along with Geant4 simulations and the presentation of novel approaches for the use in hadrontherapy monitoring, in particular background subtraction techniques, new quantities to assess ion ranges based on the prompt-gamma spatial distributions, acceleration schemes to be used in Geant4, and considerable improvements of Geant4 simulations concerning prompt-gamma emission modelling. (author)