Computational science to uncover the physical and chemical processes underlying hadrontherapy

Hadrontherapy is a cutting-edge modality of radiotherapy in which energetic ion beams (protons, as used in the Trento protontherapy centre, as well as carbon ions) are employed to kill cancer cells while sparing surrounding healthy areas. The depth-dose curve of ions in tissue presents a sharp peak towards the end of their trajectories (the Bragg peak), which allows the precise deposition of energy in the tumour. Ion beams also kill cells more effectively than photons do for the same delivered dose. These characteristics arise from a concatenation of physico-chemical events happening on different space, time and energy scales, comprising the propagation of the ion beam in the body, the excitation and ionisation of the biological materials, the transport of secondary electrons and free radicals in the micro- and nanoscale, and the damage these can produce to the sensitive DNA molecules. To gain a deeper understanding of these basic mechanisms, computational models have been developed over the years in which different techniques are used to address each specific problem: Monte Carlo simulations for describing radiation transport, dielectric response theory and time-dependent density functional theory for treating electronic excitations, or molecular dynamics for simulating radiation effects at the molecular level. A review of these models and their usefulness in the context of hadrontherapy will be given in this seminar.