Computer Simulation Computer Simulation for Emission for Emission Tomography:Tomography:Geant4 and GATEGeant4 and GATE

Xiao HanXiao Han

Aug. 2006Aug. 2006

OutlineOutline

IntroductionIntroduction Geant4Geant4 GATEGATE ConclusionConclusion

IntroductionIntroduction

Computer simulation is a necessary Computer simulation is a necessary step in designing modern emission step in designing modern emission tomography instrumentstomography instruments

Evaluation of simulation packages Evaluation of simulation packages – History and purposeHistory and purpose– FeaturesFeatures– User interfaceUser interface– How it worksHow it works– Validation and reliabilityValidation and reliability– Cost and accessibilityCost and accessibility– Current usersCurrent users

Geant4 ToolkitGeant4 Toolkit

Created by GCreated by GEANTEANT4 Collaboration (1998), 4 Collaboration (1998), to provide simulation for any area where to provide simulation for any area where particle interacts with matterparticle interacts with matter

Provides C++ classes for users to choose Provides C++ classes for users to choose to assemble their own packagesto assemble their own packages

Main featureMain feature– Software engineeringSoftware engineering– Object-oriented technologyObject-oriented technology

GATEGATE

Created by OpenGate Collaboration in 2002Created by OpenGate Collaboration in 2002 GATE – Geant4 Application for TomographiGATE – Geant4 Application for Tomographi

c Emissionc Emission FreeFree InterfaceInterface

– Input: scriptInput: script– Output:Output:

online plotteronline plotter ASCIIASCII Root …Root …

FeaturesFeatures

Well validated physics modelWell validated physics model Sophysticated geometry descriptionSophysticated geometry description Powerful visualization & 3D renderingPowerful visualization & 3D rendering Original features specific to emission tomOriginal features specific to emission tom

ography (temporal synchronization)ography (temporal synchronization)

GATE work flowGATE work flow

Scanner

Phantom

Physics

Source

Digitization

Acquisition

Scanner geometryScanner geometry

ScannerScanner

Volume shape:Volume shape:– BoxBox– SphereSphere– CylinderCylinder– ConeCone– Ellipse, etc.Ellipse, etc.

Material:Material:Geant4 database & Geant4 database &

user modifiableuser modifiable

PhantomPhantom

Similar to definition of Similar to definition of scanner geometryscanner geometry

or:or: Voxellized phantom (e.Voxellized phantom (e.

g. real patient data)g. real patient data)

SourceSource

Geant4 class Geant4 class ‘General Particle ‘General Particle Source’Source’

Source propertiesSource properties– ActivityActivity– Type of particleType of particle– Energy distributionEnergy distribution– Angular emissionAngular emission– Spatial distributionSpatial distribution– Half-lifeHalf-life

Hoffman brain phantom

Physics modelingPhysics modeling

Photon:Photon:– PhotoelectricPhotoelectric– Compton scatteringCompton scattering– Rayleigh scatteringRayleigh scattering

Electron: Electron: – IonizationIonization– Moller scatteringMoller scattering– BremsstrahlungBremsstrahlung

Electron-positron annElectron-positron annihilation:ihilation:– Gamma pair non-collinGamma pair non-collin

earityearity

Gamma photon Gamma photon emissionemission

Positron Positron emissionemission

Positron rangePositron range Positron-electron Positron-electron

annihilationannihilation Residual Residual

momentummomentum

radionuclide

e+

hv=511keV

hv=511keV

Gamma photon Gamma photon transporttransport

Rayleigh scaRayleigh scatteringttering

Compton scCompton scatteringattering

PhotoelectriPhotoelectricc

hv<511keV

hv=511keV

recoil e-

photoelectron

Electron transport & Electron transport & energy depositionenergy deposition

IonizationIonization Moller scatteringMoller scattering BremsstrahlungBremsstrahlung

e-

secondary electron

hve-

Optical photon generation and Optical photon generation and transporttransport

ScintillationScintillation TransportTransport SurfaceSurface

– ReflectionReflection– TransmissionTransmission

Physics modelingPhysics modeling

Positron decay

Optical photon transport

(before PMT)

DigitizationDigitization

A particle-matter interaction event

A physical observable

AcquisitionAcquisition

Set time sliceSet time slice Update time-dependent Update time-dependent

properties (geometry, activity) at properties (geometry, activity) at the beginning of time-slicesthe beginning of time-slices

Proceed particle transport and Proceed particle transport and data acquisition within time-data acquisition within time-slices, while system is kept staticslices, while system is kept static

ValidationValidationScanner type Studied FOM Agreement References

ECAT EXACT HR+, CPS

Spatial resolutionSensitivity

Count rates

Scatter fraction

about 3 %< 7 %

good at activityconcentrations < 20 kBq/ml

about 3 %

Jan et al 2005

Hi-Rez, Siemens

Scatter fractionCount rates

NEC curves

about 1 %good at activity

concentrations < 40 Bq/mlgood at activity

concentrations < 40 Bq/ml

Michel et al 2006

Allegro, PhilipsCount rate

Scatter fraction< 8 %8 %

Lamare et al 2006

GE Advance, GEMSEnergy spectraScatter fraction

not reported< 1 %

Schmidtlein et al 2006

MicroPET P4, ConcordeSpatial resolution

SensitivityMiniature Derenzo phantom

about 7 %< 4 %

visual assessmentJan et al 2003

MicroPET Focus, ConcordeSpatial resolution

Sensitivityabout 5 %about 3 %

Jan et al 2005

http://opengatecollaboration.healthgrid.org/physics/validation.html

Current users of GATECurrent users of GATE Ecole Polytechnique Fédérale de Lausanne (Ecole Polytechnique Fédérale de Lausanne (LPHELPHE), Lausanne), Lausanne

University of Clermont-Ferrand (University of Clermont-Ferrand (LPCLPC))University of Ghent (University of Ghent (ELISELIS))U678 INSERMU678 INSERM, CHU Pitié-Salpêtrière, Paris, CHU Pitié-Salpêtrière, ParisVrijeVrije UniversiteitUniversiteit BrusselBrussel (IIHE) (IIHE)Centre d'Exploration et de Recherche Médicales par Emission de Positons (Centre d'Exploration et de Recherche Médicales par Emission de Positons (CERMEPCERMEP), Lyon), LyonService Hospitalier Frédéric Joliot (Service Hospitalier Frédéric Joliot (SHFJSHFJ), CEA-Orsay), CEA-OrsayU601 INSERMU601 INSERM, CHU Nantes, CHU NantesSungkyunkwan University School of Medicine (Division of Nuclear Medicine), Sungkyunkwan University School of Medicine (Division of Nuclear Medicine), SeoulSeoulUniversity Louis Pasteur (University Louis Pasteur (IRESIRES), Strasbourg), StrasbourgUniversity Joseph Fourier (University Joseph Fourier (LPSCLPSC), Grenoble), GrenobleForschungszentrum-JuelichForschungszentrum-Juelich (IME), Juelich (IME), JuelichUniversity of Massachusetts Medical School (University of Massachusetts Medical School (Division of Nuclear MedicineDivision of Nuclear Medicine), Wo), WorcesterrcesterU650 INSERMU650 INSERM, LATIM, CHU Morvan, Brest, LATIM, CHU Morvan, BrestUniversity of California (University of California (Crump Institute for Molecular ImagingCrump Institute for Molecular Imaging), Los Angeles), Los AngelesDAPNIADAPNIA, CEA-Saclay, CEA-SaclayMemorial Sloan-Kettering Cancer Center (Department of Medical Physics), NMemorial Sloan-Kettering Cancer Center (Department of Medical Physics), New Yorkew YorkJohn Hopkins University (Division of Medical Imaging Physics), BaltimoreJohn Hopkins University (Division of Medical Imaging Physics), BaltimoreUniversity of Santiago of Chile (USACH)University of Santiago of Chile (USACH)NIMgroup, BIOSIM, National Technical University of AthensNIMgroup, BIOSIM, National Technical University of AthensCentre de Physique des Particules de Marseille (CPPM), Marseille Centre de Physique des Particules de Marseille (CPPM), Marseille Laboratoire de Physique Subatomique et des technologies associées (SUBATLaboratoire de Physique Subatomique et des technologies associées (SUBATECH), NantesECH), Nantes

ConclusionConclusion

GATE is capable to simulate from GATE is capable to simulate from source decay to optical photon source decay to optical photon transporttransport

GATE Simulation for Optical GATE Simulation for Optical photon generation & transport is photon generation & transport is time-consumingtime-consuming