Speaker
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Although the use of ion beams in cancer therapy has experienced a significant progress in the last decades, it is still needed to gain further basic knowledge on the physical processes underlying hadrontherapy in order to better understand and improve it [1]. These involve different space, time and energy scales, spanning from the macroscopic propagation of the ion beam (with the subsequent generation and transport of secondary electrons on the micro- and nanoscale) to the clustered damage of the sensitive biomolecules such as DNA by different types of interactions.
In recent years we have developed models for the computer simulation of the physical phenomena behind hadrontherapy. First, a dielectric response model for obtaining reliable electronic excitation and ionisation cross sections for ion beams in complex condensed-phase biomaterials was introduced, producing accurate energy and angular distributions of secondary electrons [2,3]. This allows the precise simulation of ions propagation through biologically relevant materials and to assess the electron production along their trajectories by using the SEICS (Simulation of Energetic Ions and Clusters through Solids) code [4].
This model has been extended to electron impact by introducing exchange and low-energy corrections [5,6], yielding excitation and ionisation cross sections in liquid water, DNA molecular components and other biomaterials in excellent agreement with experiments. These cross sections permit detailed simulations of the transport of secondary electrons in realistic biomaterials with the SEED (Secondary Electron Energy Deposition) code [7], which has been used to assess how the relevant physical interactions (excitation, ionisation and dissociative electron attachment –DEA–) contribute to the generation of complex DNA damage for carbon ions in liquid water in a wide energy range [8]. While ionisations sum up ~70% of the complex biodamage and excitations contribute around 20-25%, DEA (a process usually regarded as very relevant) only accounts for 5-10%. These results are important for the improvement of nanodosimetry, in which only ionisations can be currently measured in experimental setups.
[1] Nanoscale Insights into Ion-Beam Cancer Therapy, ed. A. V. Solov’yov, Springer International Publishing AG, Cham, Switzerland, 2017.
[2] P. de Vera, R. Garcia-Molina, I. Abril, A. V. Solov’yov, Phys. Rev. Lett. 110 (2013) 148104
[3] P. de Vera, R. Garcia-Molina, I. Abril, Phys. Rev. Lett. 114 (2015) 018101
[4] P. de Vera, I. Abril, R. Garcia-Molina, Rad. Res. 190 (2018) 282
[5] P. de Vera, R. Garcia-Molina, J. Phys. Chem. C 123 (2019) 2075
[6] P. de Vera, I. Abril, R. Garcia-Molina, Phys. Chem. Chem. Phys. (2020, in press). aXiv:2009.09267v1 [physics.chem-ph]
[7] M. Dapor, I. Abril, P. de Vera, R. Garcia-Molina, Phys. Rev. B 96 (2017) 064113
[8] S. Taioli, P. E. Trevisanutto, P. de Vera, S. Simonucci, I. Abril, R. Garcia-Molina, M. Dapor (2020, submitted). arXiv:2010.02366v1 [physics.bio-ph]
