a general purpose dosimetric system for brachytherapy s. chauvie 0,1 s. agostinelli 2, f. foppiano...
TRANSCRIPT
A general purpose dosimetric A general purpose dosimetric system for brachytherapy system for brachytherapy
S. Chauvie0,1 S. Agostinelli2, F. Foppiano2, S. Garelli2,
S. Guatelli1, M.G. Pia1
INFN1
National Institute for Cancer Research, IST Genova2
AO S Croce e Carle, Cuneo0
20th April 2005,Monte Carlo 2005, Chattanooga, USA
http://www.ge.infn.it/geant4
Radioactive sources are used to deposit therapeutic doses near tumors, while
preserving surrounding healthy tissues
TechniquesTechniques: : endocavitaryendocavitary
– lung, vagina, uterus
interstitialinterstitial– prostate
superficialsuperficial– skin
BrachytherapyBrachytherapy
Dose calculation in brachytherapyDose calculation in brachytherapy
NB: No commercial software available for superficial brachytherapy with Leipzig applicators
PrecisionPrecision
CostCost
Based on analyticalanalytical methods methods Approximation in source source
dosimetrydosimetry Uniform materialUniform material: water
Each software is specific specific to one techniqueto one technique and one one type of sourcetype of source TPS is expensiveexpensive
(~ hundreds K $/euro)
TPS vs Monte Carlo
Full source description: physics + geometry
CTCT based based
Ages… Fast and reliable (FDA) SpeedSpeed
Virtually no cost
Develop a Develop a general purposegeneral purpose
precise precise dosimetric system
with the capability of
realistic geometryrealistic geometryand material modelingand material modeling
interface to CT imagesinterface to CT images
with a user-friendly interfaceuser-friendly interface
atat low costlow cost
adequate adequate speedspeed for clinical usage for clinical usageperforming atperforming at
The challengeThe challengeThe challengeThe challenge
PhysicsPrimary particles
Analysis
Visualisation
Experimental set-up Events
run
Detector
Energy deposit
User Interface
DesignDesign
1. Precision 1. Precision
2. Accurate model of the real experimental set-up
2. Accurate model of the real experimental set-up
3. Easy configuration for hospital usage
3. Easy configuration for hospital usage
4. Speed4. Speed
Calculation of 3-D dose distribution3-D dose distribution in tissueDetermination of isodose isodose curves
Based on Monte CarloMonte Carlo methodsAccurate description of physicsphysics interactionsExperimental validationvalidation of physics involved
Realistic description of geometrygeometry and tissuetissuePossibility to interface to CT images
Simple user interface + Graphic visualisation Elaboration of dose distributionsdose distributions and isodosesisodoses
Parallelisation Parallelisation (Talk: (Talk: Monte Carlo Simulation for radiotherapy in a distributed environment, 19th April, Monte
Carlo 2005) and ) and access to distributed computing distributed computing resourcesresources
5. Other requirements5. Other requirements Transparent, Transparent, open to extension extension and new functionality, publicly accessiblepublicly accessible
User RequirementsUser RequirementsUser RequirementsUser Requirements
Based on Monte Carlo methodsMonte Carlo methods
Extension of electromagnetic interactions down to low energies (< 1 keV)
MicroscopicMicroscopic validation of the physics models validation of the physics modelsMacroscopicMacroscopic validation validation with experimental data experimental data
specific to the brachytherapic practice
Accurate description of physicsphysics interactions
Experimental validationvalidation of physics involved
1. Precision1. Precision
Verification of Geant4 physics: once for allVerification of Geant4 physics: once for all
Geant4 Low Energy Package for photons and electrons
Geant4 Standard Package for positrons
Validation of the Geant4 physics models with respect to experimental data and recognised reference data
Results summerised in “Comparison of Geant4 electromagnetic physics models against the NIST reference data”, submitted to IEEE Transactions on Nuclear Science
Talk: Precision Validation of Geant4 electromagnetic physics, 20th April, Monte Carlo 2005
MicroscopicMicroscopic validation of the physics models validation of the physics models
Dosimetric validation in the experimental context for simple set-ups
Dosimetric validation in the experimental context for simple set-ups
0 10 20 30 40 500,0
0,2
0,4
0,6
0,8
1,0
1,2 Simulazione Nucletron Misure
Dose %
Distanza lungo Z (mm)Distance along Z (mm)
SimulationNucletronData
F. Foppiano et al., IST Genova
Comparison to:
manufacturer data, protocol data,
original experimental data
Ir-192
experimental mesurements
G. Ghiso, S. Guatelli S. Paolo Hospital Savona
I-125 Ir-192
MacroscopicMacroscopic validation validation with experimental data experimental data specific to the brachytherapic practice
Spectrum (192IrIr, 125II)Geometry
PhantomPhantom with realistic material model with realistic material modelPossibility to interface the system to Possibility to interface the system to CTCT images images
Radioactive source
Patient
2. Accurate model of the real experimental set-up
2. Accurate model of the real experimental set-up
Precise geometry and material model of any type of source
Iodium core
• Iodium core• Air• Titanium capsule tip• Titanium tube
Iodium core:Inner radius :0Outer radius: 0.30mmHalf length:1.75mm
Air:Outer radius:0.35mm half length:1.84mm
Titanium tube:Outer radius:0.40mmHalf length:1.84mm
Titanium capsule tip:Box Side :0.80mm
I-125 source for interstitial brachytherapy
Ir-192 source + applicator for superficial brachytherapy3 m m ste e l c a b le
5.0 m m
0.6 m m
3.5 m m
1.1 m m
Ac tive Ir-192 C o re
Geometry
Results: Effects of source anisotropyResults: Effects of source anisotropyResults: Effects of source anisotropyResults: Effects of source anisotropy
LongitudinalLongitudinal axis of the source axis of the sourceDifficult to make direct measurements
TransverseTransverse axis of the source axis of the sourceComparison with experimental data
Plato-BPS treatment planning algorithm makes some crude
approximation ( dependence,
no radial dependence)
-40 -30 -20 -10 0 10 20 30 400,0
0,5
1,0
1,5
2,0
2,5
Simulazioni Plato Misure
Dose %
Distanza lungo X (mm)Distance along X (mm)
SimulationSimulationPlatoPlatoDataData
-40 -30 -20 -10 0 10 20 30 400,0
0,5
1,0
1,5
2,0
2,5 Simulazioni Plato
Dose %
Distanza lungo Z (mm)
Distance along Z (mm)
Effects of source
anisotropySimulationSimulation
PlatoPlato
Rely on simulation for better accuracy than
conventional treatment planning software
source
Modeling a phantomModeling a phantom
of any material (water, tissue, bone, muscle etc.)
thanks to the flexibility of Geant4 materials package
Modeling geometry Modeling geometry and materials from and materials from CT data through a CT data through a DICOM interfaceDICOM interface
PhantomPhantom with realistic material model with realistic material modelPossibility to interface the system to Possibility to interface the system to CTCT images images
General purpose systemGeneral purpose systemGeneral purpose systemGeneral purpose system
Object Oriented TechnologySoftware system designed in terms of Abstract Interfaces
Abstract Factory design patternSource spectrum and geometry transparently interchangeableSource spectrum and geometry transparently interchangeable
For any brachytherapy technique
For any source type
3. Easy configuration for hospital usage
3. Easy configuration for hospital usage
Configure the source geometry
Ir-192 endocavitary source I -125 interstitial source Ir-192 source + Leipzig applicator
Abstract Factory
Configuration of
any brachytherapy any brachytherapy technique technique
any source type any source type
through an Abstract Abstract FactoryFactory to define geometry, geometry, primary spectrumprimary spectrum
Configure the source spectrum
Ir-192 source
I-125 source
No commercial general software exists!
Abstract Factory design patternSource spectrum and geometry transparently interchangeableSource spectrum and geometry transparently interchangeable
Results: DosimetryResults: DosimetryResults: DosimetryResults: Dosimetry
AIDA + PI Python
Analysis of the energy deposit in the phantom resulting from the simulation
Dose distribution
Isodose curves
for analysis for interactivity
could be any other AIDA-compliant analysis system
Simulation of energy deposit through Geant4 Low Energy Electromagnetic package
to obtain accurate dose distribution
Production threshold: 100 m2-D histogram
with energy deposit in the plane containing the
source
Dosimetry Interstitial brachytherapy
Dosimetry Interstitial brachytherapy
Bebig Isoseed I-125 source
0.16 mGy =100%
Isodose curvesIsodose curves
Leipzig applicatorMicroSelectron-HDR source
DosimetryEndocavitary brachytherapy
DosimetryEndocavitary brachytherapy
DosimetrySuperficial brachytherapy
DosimetrySuperficial brachytherapy
Transparent configuration in sequential or parallel mode
Transparent access to the GRID through an Transparent access to the GRID through an intermediate software layerintermediate software layer
Parallelisation
Access to distributed computing resources
Talk: Monte Carlo Simulation for radiotherapy in a distributed environment, 19th April, Monte Carlo 2005
4.Speed4.Speedadequate for clinical useadequate for clinical useadequate for clinical useadequate for clinical use
Transparency
OO technology: plug-ins for other techniquesTreatment head
Beam line for hadrontherapy...
Application code released with Geant4Application code released with Geant4Based on open source code Based on open source code (Geant4, AIDA etc.)(Geant4, AIDA etc.)
Openness to extension and new functionality
Publicly accessible
Design and code publicly distributedDesign and code publicly distributedPhysics and models exposed through OO designPhysics and models exposed through OO design
5. Other requirements5. Other requirements
Extension and evolutionExtension and evolution
General dosimetry system for radiotherapyGeneral dosimetry system for radiotherapy extensible to other techniques
plug-ins for external beamsplug-ins for external beams
((factories for beam, geometry, physics...)
Configuration of
any brachytherapy technique any brachytherapy technique
any source type any source type
System extensible to any source configuration
without changing the existing code
SummarySummary
A precise dosimetric system, based on Geant4– Accurate physics, geometry and material modeling, CT interface
A general dosimetric system for brachytherapy– Possibility of extensions to other radiotherapic techniques
Full dosimetric analysis– AIDA + PI or other AIDA - compliant analysis tools
Fast performance– parallel processing (look: Monte Carlo Simulation for radiotherapy
in a distributed environment, 19th April, Monte Carlo 2005)
Access to distributed computing resources– GRID (look: Monte Carlo Simulation for radiotherapy in a distributed
environment, 19th April, Monte Carlo 2005)
Beware: R&D prototype!Beware: R&D prototype!