Dec - Modelling and simulation of particle interaction with matter for reference dosimetry protocol in hadrontherapy

Le 12 décembre 2018


Verónica Tessaro, completed her Licenciatura in Physics (bachelor’s + master’s degree) in 2015 at the Faculty of Exact Sciences, Engineering and Surveying, at the National University of Rosario (UNR), Argentina. That year, she began a PhD at the UNR-CONICET on the subject : "Deposition of ionizing radiation energy in biological systems of interest. Study of trace structure of hadrons and the application of dosimetry for the therapy of hadrontherapy." In 2017 she started a Phd in cotutela at the University of Lyon, by the direction of Prof. Michael Beuve from the IPNL.

Verónica Tessaro, second year thesis

Radiotherapy is the medical use of ionizing radiation to treat cancers. Unlike conventional radiotherapy which uses X-rays of high energy as beams, hadrontherapy uses charged particles such as protons or heavy ions for treatments. These particles have a specific dose profile in function of the depth, which allows an important localization of the dose in the tumor, with a considerably decreasing in the irradiation of healthy tissue. For treatments planning it is required a precise knowledge of the absorbed dose. The procedure to measure the absorbed dose in water for heavy ions is recommended by IAEA [1]. However, dosimetry control is performed using ionization chambers filled with gaz. To convert the measured values to dose on liquid water, conversion factors are required such as the stopping power and the W-values (mean energy required to form an ion-electron pair). The values of both are not accurate enough, which introduce significant uncertainties in the physical dose estimation and contributes directly to the overall uncertainty of the clinical treatments.
The calculation of these physical parameters is the main objective of my research. The inelastic cross sections of all the physical processes involve in the ion-matter interaction are necessary. The main ones considered are the ionization and electronic excitation. These values are required to obtain the cumulated counting processes induced by the incident and secondary particles. For this, we used two models : a recursive equation developed by Inokuti [2] called the Fowler Equation, based on the Continuum Slowing Down Approximation, and a Monte Carlo code developed by researchers from IPNL, CIMAP and IFIR [3], which allows us to represent the stochastic nature of the ion-matter interactions.

[1] IAEA, TECDOC-799 D (Chapter 8) ; Ed. M. Inokuti, Vienna (1995), p.547-631.
[2] M.Inokuti, Radiat. Res. Vol.64 6-22 (1975).
[3] Gervais et al, Chem. Phys. Lett. 410, 330-334 (2005) and Gervais, et al. Rad. Phys. And Chem. 75, 493 (2006).