Aca - Departamento de Física - Universidad Técnica Federico Santa ...

V Encuentro Sud Americano de Colisiones Inelásticas en la Materia
Monte Carlo simulation for proton track structure in biological matter
H. Lekadir 1 , C. Champion 1 , S. Incerti 2 , M. E. Galassi 3 , O. Fojón 3 , R. D. Rivarola 3 , and
J. Hanssen 1
1 Laboratoire de Physique Moléculaire et des Collisions, Université Paul Verlaine-Metz, Metz, France
2 Université Bordeaux 1, CNRS/IN2P3, CENBG, Bordeaux-Gradignan, France
3 Instituto de Física Rosario, CONICET, Universidad Nacional de Rosario, Rosario, Argentina
Corresponding author: lekadir@univ-metz.fr
Monte Carlo simulations are well suited
for describing the transport of charged particles
in matter and more particularly in biological
medium for predicting the radio-induced biological
consequences.
Ion beams are commonly used in radiotherapy
essentially due to their physical and radiobiological
characteristics which radically differ
from those of conventional radiation beams
(photons). Nowadays, protons are employed in
many countries for treating particular pathologies.
Indeed, in comparison to conventional
techniques, protons offer an increased biological
efficiency and a better ballistic by depositing in
particular a large part of their initial energy in a
narrow region - at the end of their path- called
the Bragg peak region. Then, they allow a better
protection of organs at risk in cancer therapy.
To model in details the track-structure of
protons in biological matter, we have then developed
a full-history Monte Carlo code called
TILDA2 which is able to describe, step by step,
all the proton induced-collisions in biological
matter, this latter being alternatively modelled
by water and by some of its most important biological
entities, namely, the DNA bases. The
originality of our code resides in the physical
processes that are integrated. Thus, TILDA2
takes into account a large panel of ionizing processes
such as single and double ionization and
capture, transfer ionization and excitation.
To do that, we have first investigated different
theoretical models for providing the
needed input data, namely, the total cross sections:
a first classical one based on a CTMC-
COB [1,2] approach and two quantum mechanical
ones, namely, a Coulomb Born (CB1) model
and a continuum-distorted wave eikonal-initialstate
(CDW-EIS) one. All the obtained cross
sections have been validated via theory/exp
comparisons.
TCS (10 -16 cm 2 )
10 3 a) H 2
O
10 2
10 1
10 0
10 -1
10 -2
10 -3
10 -4
10 2 10 3 10 4
7
Incident energy (keV/u)
b) Guanine
10 2 10 3 10 4
Figure 1. Total cross sections of the ionizing
processes included into the Monte Carlo code
TILDA2 for describing the proton transport in water
and guanine.
Under these conditions, we have access to
a large number of physical quantities such as
stopping power, energy deposition, charge fraction,
range… in water and DNA components.
Then, we have shown that the energy deposit
patterns were extremely dependent on the
medium description.
References
[1] H. Lekadir et al., Nucl. Instr. Meth. Phys
Res. B 267, 1014 (2009).
[2] H. Lekadir et al., Phys. Rev. A 79, 062710
(2009).
67 Valparaíso, Chile