Computer Simulation for Emission Tomography: Geant4 and GATE Xiao Han Aug. 2006

Outline Introduction Introduction Geant4 Geant4 GATE GATE Conclusion Conclusion

Introduction Computer simulation is a necessary step in designing modern emission tomography instruments Computer simulation is a necessary step in designing modern emission tomography instruments Evaluation of simulation packages Evaluation of simulation packages –History and purpose –Features –User interface –How it works –Validation and reliability –Cost and accessibility –Current users

Geant4 Toolkit Created by G EANT 4 Collaboration (1998), to provide simulation for any area where particle interacts with matter Created by G EANT 4 Collaboration (1998), to provide simulation for any area where particle interacts with matter Provides C++ classes for users to choose to assemble their own packages Provides C++ classes for users to choose to assemble their own packages Main feature Main feature –Software engineering –Object-oriented technology

GATE Created by OpenGate Collaboration in 2002 Created by OpenGate Collaboration in 2002 GATE – Geant4 Application for Tomographic Emission GATE – Geant4 Application for Tomographic Emission Free Free Interface Interface –Input: script –Output: online plotter online plotter ASCII ASCII Root … Root …

Features Well validated physics model Well validated physics model Sophysticated geometry description Sophysticated geometry description Powerful visualization & 3D rendering Powerful visualization & 3D rendering Original features specific to emission tomography (temporal synchronization) Original features specific to emission tomography (temporal synchronization)

GATE work flow Scanner Phantom Physics Source Digitization Acquisition

Scanner geometry

Scanner Volume shape: Volume shape: –Box –Sphere –Cylinder –Cone –Ellipse, etc. Material: Material: Geant4 database & user modifiable

Phantom Similar to definition of scanner geometry Similar to definition of scanner geometry or: or: Voxellized phantom (e.g. real patient data) Voxellized phantom (e.g. real patient data)

Source Geant4 class General Particle Source Geant4 class General Particle Source Source properties Source properties –Activity –Type of particle –Energy distribution –Angular emission –Spatial distribution –Half-life Hoffman brain phantom

Physics modeling Photon: Photon: –Photoelectric –Compton scattering –Rayleigh scattering Electron: Electron: –Ionization –Moller scattering –Bremsstrahlung Electron-positron annihilation: Electron-positron annihilation: –Gamma pair non- collinearity

Gamma photon emission Positron emission Positron emission Positron range Positron range Positron-electron annihilation Positron-electron annihilation Residual momentum Residual momentum radionuclidee+e+ hv=511keV

Gamma photon transport Rayleigh scattering Rayleigh scattering Compton scattering Compton scattering Photoelectric Photoelectric hv<511keV hv=511keV recoil e - photoelectron

Electron transport & energy deposition Ionization Ionization Moller scattering Moller scattering Bremsstrahlung Bremsstrahlung e-e- secondary electron hv e-e-

Optical photon generation and transport Scintillation Scintillation Transport Transport Surface Surface –Reflection –Transmission

Physics modeling Positron decay Optical photon transport (before PMT)

Digitization A particle-matter interaction event A physical observable

Acquisition Set time slice Set time slice Update time-dependent properties (geometry, activity) at the beginning of time-slices Update time-dependent properties (geometry, activity) at the beginning of time-slices Proceed particle transport and data acquisition within time-slices, while system is kept static Proceed particle transport and data acquisition within time-slices, while system is kept static

Validation Scanner typeStudied FOMAgreementReferences ECAT EXACT HR+, CPS Spatial resolution Sensitivity Count rates Scatter fraction about 3 % < 7 % good at activity concentrations < 20 kBq/ml about 3 % Jan et al 2005 Hi-Rez, Siemens Scatter fraction Count rates NEC curves about 1 % good at activity concentrations < 40 Bq/ml good at activity concentrations < 40 Bq/ml Michel et al 2006 Allegro, Philips Count rate Scatter fraction < 8 % 8 % Lamare et al 2006 GE Advance, GEMS Energy spectra Scatter fraction not reported < 1 % Schmidtlein et al 2006 MicroPET P4, Concorde Spatial resolution Sensitivity Miniature Derenzo phantom about 7 % < 4 % visual assessment Jan et al 2003 MicroPET Focus, Concorde Spatial resolution Sensitivity about 5 % about 3 % Jan et al

Current users of GATE Ecole Polytechnique F é d é rale de Lausanne (LPHE), Lausanne University of Clermont-Ferrand (LPC) University of Ghent (ELIS) U678 INSERM, CHU Piti é -Salpêtri è re, Paris Vrije Universiteit Brussel (IIHE) Centre d'Exploration et de Recherche M é dicales par Emission de Positons (CERMEP), Lyon Service Hospitalier Fr é d é ric Joliot (SHFJ), CEA-Orsay U601 INSERM, CHU Nantes Sungkyunkwan University School of Medicine (Division of Nuclear Medicine), Seoul University Louis Pasteur (IRES), Strasbourg University Joseph Fourier (LPSC), Grenoble Forschungszentrum-Juelich (IME), Juelich University of Massachusetts Medical School (Division of Nuclear Medicine), Worcester U650 INSERM, LATIM, CHU Morvan, Brest University of California (Crump Institute for Molecular Imaging), Los Angeles DAPNIA, CEA-Saclay Memorial Sloan-Kettering Cancer Center (Department of Medical Physics), New York John Hopkins University (Division of Medical Imaging Physics), Baltimore University of Santiago of Chile (USACH) NIMgroup, BIOSIM, National Technical University of Athens Centre de Physique des Particules de Marseille (CPPM), Marseille Laboratoire de Physique Subatomique et des technologies associ é es (SUBATECH), Nantes Ecole Polytechnique F é d é rale de Lausanne (LPHE), Lausanne University of Clermont-Ferrand (LPC) University of Ghent (ELIS) U678 INSERM, CHU Piti é -Salpêtri è re, Paris Vrije Universiteit Brussel (IIHE) Centre d'Exploration et de Recherche M é dicales par Emission de Positons (CERMEP), Lyon Service Hospitalier Fr é d é ric Joliot (SHFJ), CEA-Orsay U601 INSERM, CHU Nantes Sungkyunkwan University School of Medicine (Division of Nuclear Medicine), Seoul University Louis Pasteur (IRES), Strasbourg University Joseph Fourier (LPSC), Grenoble Forschungszentrum-Juelich (IME), Juelich University of Massachusetts Medical School (Division of Nuclear Medicine), Worcester U650 INSERM, LATIM, CHU Morvan, Brest University of California (Crump Institute for Molecular Imaging), Los Angeles DAPNIA, CEA-Saclay Memorial Sloan-Kettering Cancer Center (Department of Medical Physics), New York John Hopkins University (Division of Medical Imaging Physics), Baltimore University of Santiago of Chile (USACH) NIMgroup, BIOSIM, National Technical University of Athens Centre de Physique des Particules de Marseille (CPPM), Marseille Laboratoire de Physique Subatomique et des technologies associ é es (SUBATECH), NantesLPHELPCELIS U678 INSERM Vrije Universiteit BrusselCERMEPSHFJ U601 INSERMIRESLPSC Forschungszentrum-JuelichDivision of Nuclear Medicine U650 INSERMCrump Institute for Molecular Imaging DAPNIA Memorial Sloan-Kettering Cancer Center John Hopkins University of Santiago of Chile NIMgroup Centre de Physique des Particules de MarseilleSUBATECHLPHELPCELIS U678 INSERM Vrije Universiteit BrusselCERMEPSHFJ U601 INSERMIRESLPSC Forschungszentrum-JuelichDivision of Nuclear Medicine U650 INSERMCrump Institute for Molecular Imaging DAPNIA Memorial Sloan-Kettering Cancer Center John Hopkins University of Santiago of Chile NIMgroup Centre de Physique des Particules de MarseilleSUBATECH

Conclusion GATE is capable to simulate from source decay to optical photon transport GATE is capable to simulate from source decay to optical photon transport GATE Simulation for Optical photon generation & transport is time- consuming GATE Simulation for Optical photon generation & transport is time- consuming