Ponente
Descripción
The use of energetic ions in radiotherapy, including protons, has several advantages when compared with conventional treatments. The great targeting precision of ion beams comes from their reduced angular scattering, as well as the fact that they deposit the main part of their energy at the end of their trajectories, giving place to the depth-dose curve known as the Bragg peak. These facts make protons optimal particles to treat deep-seated tumors while minimizing the damage on the surrounding healthy tissues. In addition, physics is essential in the task of understanding not only the cellular damaging processes, but also the fundamental aspects involved in the energy deposition by primary ion beams in biologically relevant materials[1].
This work shows the simulated Bragg curves for swift proton beams, for different energies characteristic of protontherapy, interacting with biologically relevant materials such as liquid water[2] and cortical bone[3], with the aim of determining the relevant quantity known as water equivalent ratio (WER). The depth-dose distributions are obtained with the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids), which has been developed by our research group. This code considers the energy loss due to inelastic collisions, as well as elastic collisions, the fragmentation nuclear reactions, and the projectile electron capture and loss processes. It uses accurate stopping powers and energy-loss straggling values obtained from a detailed description of the electronic excitation spectrum of the condensed-phase targets, accounted for by the MELF-GOS (Mermin Energy-Loss Function–Generalized Oscillator Strengths) method[2].
Simulations for relevant energies in protontherapy (of tens and hundreds of MeV) are compared with reference simulations and experimental data for both Bragg curves and WER values (Figs. 1 and 2, respectively) for liquid water and solid cortical bone, showing a good agreement.
This work underlines the relevance of Monte Carlo simulations for analyzing the proton beams depth-dose distributions for the development and improvement of protontherapy treatments.
References
[1] de Vera, P.; Abril, I.; Garcia-Molina, R. Radiat. Res. 2018, 190, 282-297.
[2] Garcia-Molina, R.; Abril, I.; Heredia-Avalos, S.; Kyriakou, I.; Emfietzoglou, D. Phys. Med. Biol. 2011, 56, 6475-6493.
[3] Limandri, S.; de Vera, P.; Fadanelli, R.C.; Nagamine, L.C.C.M.; Mello, A.; Garcia-Molina, R.; Behar, M.; Abril, I. Phys. Rev. E, 2014, 89.
[4] Zhang, X.; Liu, W.; Li, Y.; Li, X.; Quan, M.; Mohan, R.; Anand, A.; Sahoo, N.; Gillin, M.; Zhu, X.R. Phys. Med. Biol. 2011, 56, 7725–7735.
[5] Burin, A.L.; Branco, I.S.L.; Yoriyaz, H. Radiat. Phys. Chem., 2023, 203.
