Geant4 DNA: physics and radiobiology models
S. Chauvie 1, Z. Francis 2, S. Incerti 4, B. Mascialino 3, G. Montarou 2,
Ph. Moretto 4, P. Nieminen 5, M. G. Pia 3
(The Geant4-DNA Collaboration)
(1) Azienda Ospedaliera Santa Croce e Carle Cuneo and INFN Sezione di Torino, I-10125
Torino, Italy
(2) Laboratoire de Physique Corpusculaire, CNRS/IN2P3, Université Blaise Pascal, F-63177
Aubière Cedex, France
(3) INFN Sezione di Genova, I-16146 Genova, Italy
(4) Centre d’Etudes Nucléaires de Bordeaux-Gradignan, CNRS/IN2P3, Université Bordeaux 1,
F-33175, Gradignan Cedex, France
(5) European Space Agency, 2200 AG Noordwijk, The Netherlands
Geant4 is a software toolkit for the simulation of the passage of particles through matter. It is
used by a large number of experiments and projects in a variety of application domains, including
high energy physics, astrophysics and space science, medical physics and radiation protection.
A project, named Geant4-DNA, is in progress to extend the Geant4 simulation toolkit to
model the effects of radiation with biological systems at cellular and DNA level. For the first
time a general-purpose Monte Carlo system is equipped with functionality specific to the
simulation of biological effects of radiation. The capability to address the simulation of biological
effects of radiation together with the advanced functionality offered by Geant4 in other
simulation areas (geometry, physics, interactive tools) opens a wide domain of novel applications
in several fields: from oncological radiotherapy to the radiation protection of astronauts.
Biological systems responses to irradiation exposure are of critical concern both to
radiotherapy and to risk assessment. The biological effects of radiation can be manifold, from cell
killing, to mutation in germ cells, up to carcinogenesis or leukemogenesis. The problem domain
is wide and complex; therefore, the project follows an iterative and incremental software process.
The results presented correspond to the first development cycle of the project.
A set of physics models describing elementary electromagnetic interactions for electrons,
protons, hydrogen, alpha particles and their charge states down to the eV range in liquid water –
the main component of living cells – has been implemented in Geant4. These models include
elastic scattering, excitation, charge exchange and ionization. They are of particular importance
to biomedical applications due to the abundance of this substance in biological tissues.
On the biological side, the first component implemented describes a primary biological
endpoint on a simple biological system: the survival of a population of cells irradiated with
photons or charged particles. Various mathematical models have been proposed to describe this
phenomenon. The object oriented technology adopted by Geant4 allows providing an ample set
of models to simulate the response of a cell line to irradiation, leaving the option to users to
choose among them the most appropriate ones for their simulation study. The software system
developed provides the user the option to choose among a wide set of alternative models for the
calculation of mammalian cell survival after irradiation. The flexible design adopted makes the
system open to further extension to implement other cell survival models available in literature.
We present the new physics models implemented in Geant4 and their validation activity, the
architecture of the new Geant4 component for radiobiological modeling, the detailed design of
the new cell survival models, their significant implementation features and preliminary results of
application in some selected cell lines (Chinese Hamster V79 and CHO cells). To assess the
various models’ agreement with respect to radiobiological data, simulation results are compared
with experimental data where available.