LABORATOIRE de PHYSIQUE CORPUSCULAIRE Use of Geant4 for the interpretation of irradiation at low dose on melanoma human cells G.Montarou (LPC Clermont) IN2P3 / CNRS Université Blaise Pascal 24 rue des Landais AUBIERE Cedex FRANCE

Who are we ? LPC (Laboratoire de Physique Corpusculaire) is one of the laboratories of the « Institut National de Physique Nucléaire et des Particules » (IN2P3) LPC depends also of the Blaise Pascal University ► 56 physicists (University or CNRS position) ► 45 Engineers or technicians ► 24 PhD

Who are we ? You can see more at

Where are we ? Clermont-Ferrand is the capital of region Auvergne Auvergne University, Blaise Pascal University  students

What we do High Energy Experiments at :  CERN (ATLAS, LHCb, ALICE, NA60),  Fermilab (D0),  Brookhaven (Phenix), Nuclear Physics Experiments at :  GSI (FOPI),  TJNAF, But also Applied Physics with two groups : The PCSV group (1 physicist, 3 PhD and 2 associated engineers) works on the “Data grid” development especially in biomedical application (GATE Development on the GRID) The AVIRM group (4 physicists, 3 PhD and 3 associated engineers) works the interaction of with matter in different fields especially of the interaction of neutrons with biological matter at low dose

Irradiation with 14 MeV neutron of Human melanomia cells at low dose and low rate High Radioresistivity to X-ray (3Gy/h) Hypersensibility of cells to 14 MeV neutron at low dose rate (5cGy/h) Cellular reliability curves of human malanoma cells after low dose rate X-ray and 14 MeV neutrons irradiation

  The observation of this phenomenon push us to study the types of interactions which will take place between the neutrons and the human melanomia cells as well as the amount of energy deposited in the cells.   Same phenomenon observed with C12   Extension of irradiations to human glioblastoma and fibroblast cells   To understand experimental data we need to simulate the interaction of the neutrons with biological matter, down to DNA scale First step  dedicated MC code (DIANE) ML Nenot PhD Thesis 2003

Neutron-hydrogen collision constitutes the principal interaction of the neutrons with the biological matter Elastic diffused Neutron Hydrogène nucleus Cell Sub-cellular element Energy deposited Incident Neutron  Recoil Proton  ’’ electron ’’ R Track of the recoil protons Deposit of energy in the cells is primarily due to the recoil protons

Interaction of 14 MeV Neutrons with water Rate of charged particles produced expressed in percent

Energy deposition by the way of secondaries electrons from the interaction of the charged recoil particles 10 eV – 100 Energy of these electron go down to very low energy range (10 eV – 100 eV) Need of specific framework to deal with such electron production and propagation in matter See work of G Paretzke, H. Nikjoo, W Frieldland Interactions of neutrons with biological matter (like water): ► elastic collision ► Inelastic collision ( n, γ ) Reaction ( n, α ) Reaction …

The ionisation in Standard Geant4 1- Continue Energy loss by charged Ions: Bethe-Bloch Bethe-Bloch where m is the mass of the e- r e is e- radius r e is e- radius n e is e- density in the medium n e is e- density in the medium T up is min (Tcut, Tmax) T up is min (Tcut, Tmax) The maximum of the energie transfered to the e- is :

2- Process of production of deltas e (Discret) The differential cross-section for the ejection of a e- Kinetic energy T : The totale cross-section per atome :

At very low proton energy specific parametrisations are used : Se = dE / dX is electronic stopping power in eV/1015 atoms/cm2 Ai are experimental parameters given by:

electron rates ejected by specific recoil particles electron rates ejected by specific recoil particles

Energie distribution of the ejected electrons

The Cucinotta model and its implantation in Geant4 and (for water)

Comparison Geant4.6.0 Vs Cucinotta

Experimental Setup Irradiation bunker Irradiaton bunker door 14 MeV neutron Generator Zoom Bottles containing the human melanomia cells He 3 detector to monitor the neutron flux

What we need ! Implantation in GEANT4 of the framework to take into account: ► Production of low energy electrons from charges recoil particles (10 eV – 100 eV), ► Propagation of these electrons down to a very low energy range, ► Standard Modelisation of cells, A lot of work done by different groups all around the word that appears as dedicated code (PITS, SRIM, PARTRAC…) Could we implement all this existing matter in dedicated Version of GEANT4 ??