Transcript Geant4 Space Workshop

Riccardo Capra1, Stéphane Chauvie2 ,
Ziad Francis3, Sebastien Incerti4, Barbara
Mascialino1, Gerard Montarou3, Philippe Moretto4,
Petteri Nieminen5, Maria Grazia Pia1
The
Collaboration
1
INFN Sezione di Genova (Italy)
Ospedaliera Santa Croce e Carle Cuneo; INFN Sezione di Torino (Italy)
3 Université Blaise Pascal, Laboratoire de Physique Corpusculaire; IN2P3 (France)
4 Centre d’Etudes Nucléaires de Bordeaux-Gradignan and Université Bordeaux; IN2P3 (France)
5 European Space Agency (The Netherlands)
2 Azienda
Radiobiological models implementation
in
Toolkit
14th Symposium on Microdosimetry
November 13-18, 2005 – Venezia, Italy
Abstract
A project is in progress to extend the Geant4 simulation toolkit to model the effects of radiation with
biological systems, both at cellular and DNA level. For the first time a general-purpose Monte Carlo
system is equipped with functionality specific to radiobiological simulations.
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 project follows an iterative and incremental software
process; the first component implemented describes a primary biological endpoint: the fractional
survival of a population of cells irradiated with photons or charged particles. It provides the user the
option to choose among a wide set of cell survival models, such as models based on the target theory of
cell killing, the repair-misrepair model, the lethal-potentially lethal model, and the Scholz and Kraft
model. The flexible design adopted makes it open to further extension to implement other cell survival
models.
We present the architecture of the new Geant4 component for radiobiological modeling, the detailed
design of the cell survival models implemented and preliminary results of application in some specific
cell lines. The simulation tool developed for the study of radiation interaction with biological matter
would have a wide domain of application in several fields: from oncological radiotherapy to the
radiation protection of astronauts.
is a simulation toolkit for the simulation of the passage of
particles through matter.
object-oriented design and component architecture
allows the extension of the toolkit functionality
without affecting its kernel.
A project is in progress to extend the
simulation toolkit
to model the effects of radiation with biological systems, both at
cellular and DNA level.
For the first time a general-purpose Monte Carlo system is
equipped with functionality specific to radiobiological
simulations.
Biological models in Geant4
Relevance for space:
astronaut and aircrew radiation hazards
Collection of User Requirements
Physical
processes
Biological
processes
Known,
available
Courtesy Nature
Unknown,
not available
User requirements on
geometry and
visualisation
Process
requirements
E.g. generation
Chemical of free rad
icals
processes in the cell
Software process guidelines
Unified Process, specifically tailored to the project
– practical guidance and tools from the RUP
– both rigorous and lightweight
– mapping onto ISO 15504
Incremental and iterative life-cycle
mandatory in such a complex, evolving research field
Realistic, concrete objectives
– code release with usable functionality
SPIRAL APPROACH
First component
fractional survival of
a population of
cells irradiated with
photons or charged particles
Biological processes
Complexity
Multiple disciplines involved
– physics
– chemistry
– biology
Courtesy A. Brahme (KI)
Still object of active research
Courtesy A. Brahme
(Karolinska Institute)
– not fully known
– no general models, only
partial/empirical ones
Uncertainties
Physics
Particles / Fluence rates
Shielding
LOW
MODERATE
Radiobiology
LARGE
(cells, tissues, animals)
Extrapolations
to human
beings
Acute exposure
Chronic exposure
Space radiation effects
LARGE
LARGER
Scope
Goal: provide capabilities to study the biological
effects of radiation at multiple levels
Macroscopic
– calculation of dose
– already feasible with Geant4
– develop useful associated tools
Cellular level
Complexity of
software, physics and biology
addressed with an iterative and
incremental software process
– cell modelling
– processes for cell survival, transformation etc.
DNA level
Parallel development
at all the three levels
– DNA modelling
(domain decomposition)
– physics processes at the eV scale
– processes for DNA strand breaks, chromosome aberrations etc.
Different biological endpoints
Cell
survival
Cell
transformation
Chromosome
aberrations
Sublethal damage repair
Cell cycle
Temperature
Fractionation
Dose rate effect
Inverse dose rate effect
Low dose hypersensitivity
Courtesy Hall
Courtesy Blakely
Cellular level
Models for cell survival
SURVIVAL MODELS
 Single-hit model
 Multi-target single-hit model
 Single-target multi-hit model
 Theory of radiation action
 Theory of dual radiation action
 Repair-Misrepair model
 Lethal-Potentially lethal model
 Scholz-Kraft model
Critical evaluation of the models
done
Requirements
Problem domain analysis
in progress
Analysis & Design
Implementation
Test
future
Experimental validation of
Geant4 simulation models
The flexible design adopted makes it open to further extension to implement other cell survival models.
Primary and secondary particles deposit energy
Incident radiation
(electromagnetic and hadronic interactions)
Cell line
PROBLEM:
Describe the surviving fraction of cells starting from alternative theoretical models
- Repair-misrepair model
- Lethal – potentially lethal model
- Scholz-Kraft model
- Target theory models
- Radiation action model
- Dual radiation action model
Retrieve
the dose
in the cell
Model the cell in terms of
geometry and materials
Cell nucleus
Cell cytoplasm
Describe the
surviving fraction
On the basis of
the model selected
Retrieve the
biological outcome
of the targeted cells
DNA level
Low Energy Physics extensions
Current Geant4 low energy electromagnetic processes: down to
250/100 eV (electrons and photons)
– not adequate for application at the DNA level
Elastic
scattering
Excitation
Electrons
exchange
Ionisation
processes
Specialised processes down to the eV scale
– at this scale physics processes depend on material, phase etc.
– some models exist in literature (Dingfelder et al., Emfietzoglou et al. etc.)
In progress: Geant4 processes in water at the eV scale
http://www.ge.infn.it/geant4/dna