Slide1 : GATE
Overview and recent advances Nicolas Karakatsanis
Irène Buvat National Technical University of Athens, Greece
Laboratory of Functional Imaging, U678 INSERM, Paris, France
Slide2 : Outline Evolution of the use of MC simulations in ET since 1996
OpenGATE motivation and short history
New features in MC simulators in ET
New applications for MC simulations
Upcoming developments in MC simulations
Conclusion
Slide3 : Evolution of the codes used for MC simulations in ET since 1996 1996-2000 14 different codes:
- 10 « home-made »
- 4 publicly released or available from authors
Slide4 : Motivation for developing GATE in 2001 Provide a public code
based on a standard code to ensure reliability
enabling SPECT and PET simulations (possibly even more)
accommodating almost any detector design (including prototypes)
modeling time-dependent processes
user-friendly
Developed as a collaborative effort
Slide5 : The OpenGATE collaboration From 4 to 23 labs worldwide U601 Inserm, Nantes
U650 Inserm, Brest
U678 Inserm, Paris
LPC CNRS, Clermont Ferrand
IReS CNRS, Strasbourg
UMR5515 CNRS, CREATIS, Lyon,
CPPM CNRS, Marseilles
Subatech, CNRS, Nantes
SHFJ CEA, Orsay
DAPNIA CEA, Saclay
Joseph Fourier University, Grenoble Delft University of Technology, Delft, The Netherlands
Ecole Polytechnique Fédérale de Lausanne, Switzerland
Forschungszentrum Juelich, Germany
Ghent University, Belgium
National Technical University of Athens, Greece
Vrije Universiteit Brussel, Belgium John Hopkins University, Baltimore, USA
Memorial Sloan-Kettering Cancer Center, New York, USA
University of California, Los Angeles, USA
University of Massachusetts Medical School, Worcester, USA
University of Santiago of Chile, Chile
Sungkyunkwan University School of Medicine, Seoul, Korea
Slide6 : Product of OpenGATE: GATE Publicly released on May 2004 http://www.opengatecollaboration.org
An official publication:
Jan S, Santin G, Strul D, Staelens S, Assié K, Autret D, Avner D, Barbier R, Bardiès M, Bloomfield PM, Brasse D, Breton V, Bruyndonckx P, Buvat I, Chatziioannou AF, Choi Y, Chung YH, Comtat C, Donnarieix D, Ferrer L, Glick SJ, Groiselle CJ, Guez D, Honore PF, Kerhoas-Cavata S, Kirov AS, Kohli V, Koole M, Krieguer M, van der Laan DJ, Lamare F, Largeron G, Lartizien C, Lazaro D, Maas MC, Maigne L, Mayet F, Melot F, Merheb C, Pennacchio E, Perez J, Pietrzyk U, Rannou FR, Rey M, Schaart D, Schmidtlein CR, Simon L, Song TY, Vieira JM, Visvikis D, Van de Walle R, Wiers E, Morel C. GATE: a simulation toolkit for PET and SPECT. Phys Med Biol 49: 4543-4561, 2004.
More than 800 subscribers to the Gate users mailing list
Slide7 : Tasks of the OpenGATE collaboration Upgrade GATE for following GEANT4 new releases (1 major release per year)
Incorporate new developments in GATE (1 minor release per year) e.g.:
variance reduction techniques (to be released soon)
speed-up options (e.g., analytical modeling of the collimator response in SPECT) (to be released soon)
tools for running GATE on a cluster or on a grid environment (to be released soon)
extension of GATE for dosimetry applications
tools for interfacing GATE output with other software (STIR)
Organize training
Slide8 : GATE today: technical features Based on GEANT 4
Written in C++
User-friendly: simulations can be designed and controlled using macros, without any knowledge in C++
Appropriate for SPECT and PET simulations
Flexible enough to model almost any detector design, including prototypes
Explicit modeling of time (hence detector motion, patient motion, radioactive decay, dead time, time of flight, tracer kinetics)
Can handle voxelized and analytical phantoms
Slide9 : GATE today: practical features Can be freely downloaded, including the source codes
Can be run on many platforms (Linux, Unix, MacOs)
On-line documentation, including FAQ and archives of all questions (and often answers) about GATE that have been asked so far
Help about the use of GATE can be obtained through the gate-user mailing list
Many commercial tomographs and prototypes have already been modeled (including validation of the model)
Slide10 : www.opengatecollaboration.org
Slide11 : PET systems already modeled by the OpenGATE collaboration
Slide12 : Some examples
Slide13 : Some examples Guez et al, DAPNIA and SHJF HRRT
Slide14 : SPECT systems already modeled by the OpenGATE collaboration
Slide15 : Example Schielding Backcompartment NaI(Tl)
crystal Scanning table Phantom holder MEHR collimator DST Xli camera Assié et al, Phys Med Biol 2005
Slide16 : Some examples Counts (AU) Assié et al, Phys Med Biol 2005 Energy (keV) Counts (AU) 0 2 4 6 8 10 12 14 50 70 90 110 130 150 170 190 210 230 250 270 Indium 111 source in air Indium 111 source in water
Slide17 : Prototypes already modeled by the OpenGATE collaboration
Slide18 : Example PSPMT crystal collimator Experiment GATE Energy (keV) Number of counts Energy spectrum Lazaro et al, Phys Med Biol 2004 IASA CsI(Tl) gamma camera …
Slide19 : Monte Carlo simulations today: what is new?
Slide20 : Modeling time dependent processes SPECT and PET intrinsically involves time:
Change of tracer distribution over time (tracer biokinetic)
Detector motions during acquisition
Patient motion
Radioactive decay
Dead time of the detector
Time-of-flight PET
GEANT 4 (hence GATE) is perfect in that regard
Slide21 : Modeling of radioactive decay Santin et al, IEEE Trans Nucl Sci 2003 15O (2 min)
11C (20 min)
Slide22 : Modeling of time of flight PET Groiselle et al, IEEE MIC Conf Rec 2004
Slide23 : Realistic phantoms can be easily used as GATE input NCAT Modeling realistic phantoms Segars et al, Mol Imaging Biol 2004 MOBY Segars et al, IEEE TNS 2001 Descourt et al, IEEE MIC Conf Records 2006
Slide24 : Modeling original detector designs Non-conventional geometries TEP/CT BIOGRAPH Siemens Spherical geometry of the Hi-Rez PET scanner Michel et al, IEEE Conf Records 2006 lead
end-shielding detection block GEANT 4 is a very flexible tool
Slide25 : Modeling original detector designs TEP/CT BIOGRAPH Siemens Sakellios et al, IEEE MIC Conf Records 2006 Small animal imaging Mouse-size gamma camera
2 Hamamatsu H8500 PSPMT
NaI pixelized scintillator
Tungsten collimator Mouse-size PET
1 Hamamatsu H8500 PSPMT
pixelated LYSO scintillator (30 x 35 crystals per block, 1 head = 1 block)
Slide26 : Modeling original detector designs Sakellios et al, IEEE MIC Conf Records 2006 Small animal imaging Simulated mouse gamma camera image
(MOBY phantom) Simulated mouse PET image
(MOBY phantom)
Slide27 : New applications for Monte Carlo simulations Design and assessment of correction and reconstruction methods Study of an imaging system response Use in the very imaging process Data production for evaluation purpose Description and validation of a code 1995-1999
Slide28 : Optimizing detector design Michel et al IEEE MIC Conf Records 2006 NEC curves as a function of the crystal in the PET HiRez scanner
Slide29 : Using Monte Carlo simulations for calculating the system matrix “Object” f Projection p p = R f GATE is very appropriate but slow
Slide30 : Example: SPECT Tc99m phantom Simulated data El Bitar et al IEEE MIC Conf Records 2006
Slide31 : What next?
Slide32 : Bridging the gap between MC modeling in imaging and dosimetry Dewaraja et al, J Nucl Med 2005 SIMIND DPM DPM The validity of the physics at low energy will have to be checked
Problems in G4 have been identified, e.g., multiple scattering and corresponding energy deposit calculation
Slide33 : Modeling hybrid machines (PET/CT, SPECT/CT, OPET) Integrating Monte Carlo modeling tools for:
- common coordinate system
- common object description
- consistent sampling
- convenient assessment of multimodality imaging GATE Brasse et al, IEEE MIC Conf Rec 2004 GATE Alexandrakis et al, Phys Med Biol 2005 OPET GATE TOAST PET/CT SPECT/CT On-going studies regarding the use of GATE for CT simulations
Slide34 : Conclusion GATE is a very relevant tool for Monte Carlo simulations in ET Simulations will be more and more present in (nuclear) medical imaging in the future:
as a invaluable guide for designing scanners, imaging protocols and interpreting SPECT and PET scans
in the very imaging process of a patient
Slide35 : Last but not least: next GATE training
3 days, March 7-9th, 2007 in Clermont-Ferrand, France
GATE installation, GATE use through lectures and practical sessions given by GATE experts
Registration will open on December, attendance will be limited Registration from mid-december on http://www.opengatecollaboration.org
Slide36 : Acknowledgments The OpenGATE collaboration
Thank you!!! : Thank you!!!
Slide38 : Throughput of the simulations The major problem with GATE and GEANT4! High throughput needed for efficient data production
Large number of particles to be simulated
low detection efficiency
in SPECT, typically 1 / 10 000 is detected
in PET, 1 / 200 is detected
Big “World”:
- detectors have a “diameter” greater than 1 m
emitting object (e.g., patient) is large (50 cm up to 1.80 m)
emitting object is finely sampled (typically 1 mm x 1 mm x 1 mm cells)
voxelized objects are most often used At least 4 approaches can be used to increase the throughput of the simulations
Slide39 : Using acceleration methods Variance reduction techniques such as importance sampling (e.g. in SimSET) speed-up factors between 2 and 15
Slide40 : Combining MC with non MC modeling increase in efficiency > 100 Song et al, Phys Med Biol 2005 Full MC Collimator Angular Response Function
Slide41 : Parallel execution of the code on a distributed architecture PET old merger new merger Speed-up factor
~ number of jobs De Beenhouwer et al, IEEE MIC Conf Records 2006
Slide42 : Smart sampling Taschereau et al, Med Phys 2006