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!