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F. Foppiano, B. Mascialino, M. G. Pia, M. Piergentili
Geant4 Simulation of an Geant4 Simulation of an Accelerator Head for Intensity Accelerator Head for Intensity
Modulated RadioTherapyModulated RadioTherapy
Monte Carlo 2005Topical Meeting
Chattanooga, April 2005
Radiotherapy with external beamsRadiotherapy with external beams
A cancer or a tissue near a surgically removed tumour may be irradiated with
photons in order to reduce the tumour size or to sterilize the zone
Cancer cells are more sensitive to radiation damage compared to
healthy cells
The goal of radiotherapy is delivering the required therapeutic dose to the tumor area with high precision, while preserving the surrounding healthy tissue
Accurate dosimetry is at the basis of radiotherapy treatment planning
GANTRY
COUCH
Intensity Modulated Radiation TherapyIntensity Modulated Radiation Therapy
step and shoot • Dose distribution more homogeneous within the Planned Target Volume (PTV)
• Sharper fall-off of dose at PTV boundary
• Non-homogeneous dose distribution to treat concave surface
Progress in 3D medical imaging
The exposure of healthy tissue to high doses can be reduced
Beam aperture is shaped to the irregular shape of the target
Photon fluence is modulated
head and neckbreast
prostate IMRT
Conformationaltechnique
dynamic technique
• Target
• Primary collimators
• Vacuum windows
• Flattening filter
• Mirror
• Monitor chamber
• Secondary collimators
• Multileaf collimator
The LINACThe LINAC
EEee=6 MV=6 MV
GANTRY
COUCH
Dosimetric system
Commercial systems
Analytic algorithmsAnalytic algorithmsEs.: Eclipse, Plato
fast, but based on approximations
precise
Accurate modeling of the experimental
set-up
Dose distribution
in a phantom
easy to configure
quick
Problem StatementProblem Statement
determine the dose distribution in a phantom resulting from the head of a linear accelerator
General planGeneral plan
Geant4
AIDA/Anaphe
OO technology
Specific software process
Functionality Design Advanced
software
Microscopic validation of Geant4 processes
(established references - NIST) Dosimetric validation of the
system(experimental measurements -
IST)
validation of the
dosimetric system
planning and developing the
dosimetric system
simulation analysis+
DIANE
Goodness-of-FitStatistical Toolkit
Validation of the dosimetric systemValidation of the dosimetric system
EXPERIMENTAL MEASUREMENTSEXPERIMENTAL MEASUREMENTS
• Ion chamber PTW 31002 flexibleIon chamber PTW 31002 flexible• Water Phantom PTW MP3Water Phantom PTW MP3• no MLC (squared fields)no MLC (squared fields)
Lateral dose profileLateral dose profile
• Radiographic film Radiographic film Kodak X-Omat V• Plexiglass phantomPlexiglass phantom• with MLCwith MLC
Dose distribution in a planeDose distribution in a plane
Percent depth dosePercent depth dose Isodoses Isodoses
SIMULATION RESULTSSIMULATION RESULTS
The simulationThe simulation
Geant4Geant4simulation of the passage of particles through matter
flexibility openness to extension and evolution trasparency
rigorous software engineering methodologies and OO technology
Low Energy
Electromagnetic
Package
Low Energy
Accurate dose calculation
• the geometry of the system and the materials involved (Geometry, Materials),• physics interactions of particles through matter (Processes),• detector response (Hit, Digits, Read-out geometry),• track of the particles (Tracking),• to manage the events (Event, Run),• visualisation of the detector and of the particles trajectories (Visualization),• user interface (Interfaces).
< 1 keV
Dosimetric systemDosimetric system
The analysis produces some histograms from which the user can calculate the Percent Depth Dose (PDD), the lateral profiles at the following depths in the phantom: 15 mm, 50 mm, 100 mm and 200 mm, and the isodoses curves in a plane
Gaussian distribution for energy and momentum of primary particles
Each pair of jaws can be rotated through an axis perpendicular to the beam axis
The user can choose the position of every single leaf
phantom
jaws
flatteningfilter
primarycollimator
Dosimetric systemDosimetric system Flattening filter
MLC
Primary collimators and target
Multi-leaf collimator
phantom
MLC
jaws
primarycollimator
target
DesignDesign
FlexibilityExtensibilityDistributed responsibility
Design Pattern
Decorator
Design Pattern
Decorator
Software technologiesSoftware technologies
Mapped on ISO 15504
Dinamic dimension
Based on use cases
Rational Unified Process
Specific software process for this
dosimetric system
Software process artifacts
based on the Unified Process
Sta
tic
dim
ensi
on
The process was tailored tothe specific needs of the project
Specific software process for the dosimetric systemSpecific software process for the dosimetric system
Time
Inception Elaboration Construction Transition
Vision
Use cases
User requirements
Risk list
Requirements analysis
Architecture elaboration
Implementation
Design analysis
Test
Public deployment of the code
Documentation
DISCIPLINES:Business Modeling, Requirements, Analysis & Design, Implementation, Test,
Deployment, Configuration & Change Management, Project Management, Enviroment.
S. Guatelli, B. Mascialino, L. Moneta, I. Papadopouls, A. Pfeiffer, M. G. Pia, M. PiergentiliExperience with software process in physics experiments
Microscopic validation of Microscopic validation of Geant4 processesGeant4 processes
• Validation of Geant4 electromagnetic models against established references (ICRU - NIST)
• Simulation of physics quantities in the same experimental set-up as reference data
• Rigorous quantitative statistical comparison
PHYSICAL TESTGOODNESS-OF-FIT
TESTINGQuantitative statistical analysis
- Evaluation of Geant4 physics goodness- How the various Geant4 models behave in the same experimental condition - Systematic data analysis allows to improve the physics models and guarantees the reliability
Scope
Microscopic validation of Geant4 Microscopic validation of Geant4 processesprocesses
• PhotonPhoton Attenuation Coefficient
• PhotonPhoton Cross Sections (attenuation coefficients with only one process activated)
• ElectronElectron CSDA range and Stopping Power
(no multiple scattering, no energy fluctuations)Elements: Be, Al, Si, Fe, Ge, Ag, Cs, Au, Pb, U
+ waterEnergy range: 1 keV – 10 GeV
Geant4 processes pertinent to this Geant4 processes pertinent to this applicationapplication
Microscopic validation of Geant4 Microscopic validation of Geant4 processesprocesses
Physics models under test:• Geant4 Standard• Geant4 Low Energy - Livermore• Geant4 Low Energy – Penelope
Reference data:• NIST
K. Amako, S. Guatelli, V. Ivanchenko, M. Maire, B. Mascialino, K. Murakami, P. Nieminen, L. Pandola, S.
Parlati, A. Pfeiffer, M. G. Pia, M. Piergentili, T. Sasaki, L. Urban
Precision validation of Geant4 electromagnetic physics
G4 LowE G4 LowE PackagePackage
QUANTITATIVEQUANTITATIVECOMPARISONSCOMPARISONS
Validation of the dosimetric Validation of the dosimetric system:system:
- lateral dose profiles - lateral dose profiles - depth dose profiles- depth dose profiles
Experimental measurements with ion Experimental measurements with ion chamberchamber
IAEA 398
Percent Depth Dose
Squared fields 5x5 cm, 10x10 cm, 40x40 cm
Ion chamber:PTW 31002 Flexible.
Water phantom: PTW MP3
Distance (mm)
Per
cent
dos
e
PDD6MV – 10x10 field
Distance (mm)
Per
cent
dos
e
Lateral profile6MV – 10x10 field
International AtomicEnergy Agency
Comparison with experimental dataComparison with experimental data
range D p-value
-84 -60 mm 0.39 0.23
-59 -48 mm 0.27 0.90
-47 47 mm 0.43 0.19
48 59 mm 0.30 0.82
60 84 mm 0.40 0.10
range D p-value
-56 -35 mm 0.26 0.89
-34 -22 mm 0.43 0.42
-21 21 mm 0.38 0.08
22 32 mm 0.26 0.98
33 36 mm 0.57 0.13
1010 events
100 CPU dayson Pentium IV 3 GHz
Lateral profiles
B. Mascialino, A. Pfeiffer, M. G. Pia, A. Ribon, P. ViarengoA Toolkit for statistical comparison of data distributions
Distance (mm)
Per
cent
dos
e
Lateral profile6MV – 5x5 field – 15mm depth
Dosimetric system
Experimental data
Distance (mm)
Per
cent
dos
e
Lateral profile6MV – 10x10 field – 50mm depth
Dosimetric system
Experimental data
Kolmogorov-Smirnov test
Kolmogorov-Smirnov test
Comparison with experimental dataComparison with experimental data
D = 0.005; p-value = 1
range D p-value
0 14 mm 0.55 0.09
15 300 mm
0.14 0.12 Kolmogorov-Smirnov test
percent depth dose
Per
cent
dos
e
PDD6MV – 40x40 field
Dosimetric system
Experimental data
Voxels 5mmVoxels 5mm
Depth (mm)
Depth (mm)
Per
cent
dos
e
PDD6MV – 10x10 field
Voxels 5mmVoxels 5mm
Dosimetric system
Experimental data
Application of the Application of the dosimetric system:dosimetric system:
- dose distribution in a - dose distribution in a plane plane
- isodose lines- isodose lines
Experimental measurements with radiographic Experimental measurements with radiographic filmsfilms
Kodak X-Omat V filmsScanner VXR16 Dosimetry ProSoftware Rit 113
Grey tone Optical density Dose
Spatial resolution = 89 m
Field used to treat prostate cancer
using the MLC
Experimental data and simulation resultsExperimental data and simulation results
radiographicradiographicfilmfilm
Dose distribution in a Dose distribution in a planeplane
dosimetricdosimetricsystemsystem
dosimetricdosimetricsystemsystem
radiographicradiographicfilmfilm
Isodose linesIsodose lines
dosimetricdosimetricsystemsystem
RIT 113RIT 113
dosimetricdosimetricsystemsystemRIT 113RIT 113
intra-leaf transmission
ConclusionsConclusions
• Dosimetric system for IMRT based on Geant4 – reproduces with high accuracy experimental data – can be used to verify treatment plans in a reliable way
• Open source dosimetric system
• Geant4 Low Energy electromagnetic package
- Validation of physical processes in Geant4
• Quantitative comparison with experimental measurements
precision
This is an Advanced Example of
Activities in progressActivities in progress
• Phase space
• Dynamic tecnique
• Parallelisation
For furher informations:
[email protected]@ge.infn.it
J. T. Moscicki, S. Guatelli, M. G. Pia, M. PiergentiliMonte Carlo simulation for radiotherapy in a distributed
computing environment
