Transcript GATE (Geant4 Application for Tomographic Emission): a PET

GATE
(Geant4 Application for Tomographic Emission):
a PET/SPECT general-purpose simulation platform
G.Santin (ESA-ESTEC & Trieste University)
D.Strul, C.Morel (Lausanne University)
(for the OpenGATE Collaboration)
8th Topical Seminar on Innovative
Particle and Radiation Detectors
21 - 24 October 2002
Siena, Italy
Imaging in Nuclear Medicine
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GATE
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Anatomical imaging
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X-rays, MRI scanners, CAT, ultrasound
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Detailed info about the tissue structure and composition
Functional imaging
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In vivo physiologic analysis
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Spatial distribution (and evolution!) of radio nuclides in the body
(pharmacokinetics, metabolism)
 We see the organ during its activity
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Quantitative analysis (concentrations)
• PET:
– Biological molecules tagged with radioactive isotopes with short
life-time (15OT1/2~2 min, 11C20 min)
– Resolution down to a few mm3
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• SPECT:
– Longer decay times (99mTc6 h, 123I13 h , 133Xe5 d)
• no need for accelerator facilities
– Poorer sensitivity (and resolution)
• Multimodality
– Due to low resolution  recently often associated to other
modalities of scanning (MRI, CT)
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Simulations in Nuclear Medicine
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Wide range of applications
– scanner design, image reconstruction, scatter correction, protocol
optimization,…
Analytical computations
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Since a couple of decades: accurate Monte Carlo simulations are widely
used in parallel to analytical computations or experimental studies for a
large range of PET and SPECT applications
GATE
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– PETsim, SimSET, EIDOLON, SIMIND, SimSPECT, SORTEO, MCMATV, PETEGS, …
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– Non exaustive list
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Computation time
– Is still a concern
– ( see later)
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Two approaches…
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Dedicated simulation programs (PETsim, SimSET, Eidolon,… )
– Simple geometry, limited number of requirements
– Fast development
– Optimized on application
– Limits in the physics description
– Maintenance, upgrades?
GATE
GATE
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General purpose simulation codes (Geant4, EGS4, MCNP)
– Wide community of developers and users
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– code and physics validation
– documentation and support
– Complexity
– Speed
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GATE
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Based on Geant4
– Physics description
– Long term availability
– Upgrades, documentation & support
GATE
– Object Oriented Analysis & Design
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Extensions to build a simulation platform for PET/SPECT
– Ease of use for non C++ programmers
• scripting almost everywhere, geometry included…
– Typical Nuclear Medicine options included
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• material database, sources, readout,…
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AND MORE !
– Time management
– Movements
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How it works
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3 different layers
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Developer level
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GATE
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User Interface
User level
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Simulation parameters
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Framework and application classes
C++ programming
Geometry
Sources
…
Scripting only
Application classes
Framework
Geant4
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GATE detailed structure
Timing
scripting
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GATE
Source
scripting
Geometr
y
scripting
Analysis
scripting
Specific
source type
Specific I/O
Specifi
c
analysi
s
Specifi
c
volume
Time
mgr
Source
mgr
Geometry
mgr
I/O
choice
scripting
Specifi
c
source
Analysis
mgr
I/O
mgr
Geant4
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Geometry scripting
/gate/world/daughters/name source
/gate/world/daughters/insert cylinder
…
/gate/source/daughters/name body
/gate/source/daughters/insert cylinder
…
world
Scanner
Sourc
e
Body
Head
Rsector
GATE
/gate/source/daughters/name head
/gate/source/daughters/insert sphere
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/gate/world/daughters/name scanner
/gate/world/daughters/insert cylinder
…
Crystal
/gate/scanner/daughters/name rsector
/gate/scanner/daughters/insert box
…
LSO
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/gate/rsector/daughters/name crystal
/gate/rsector/daughters/insert box
…
BG
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/gate/crystal/daughters/name LSO
/gate/crystal/daughters/insert box
…
/gate/crystal/daughters/name BGO
/gate/crystal/daughters/insert box
…
D.Strul
Uni Lausanne
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Geometry examples
PET
GATE
SPECT
G.Santin
S. Staelens, Univ. Ghent
Collimator detail
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GATE
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G.Santin
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Multiple sources
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Controlled by source manager
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Inserted via scripting
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Complex geometries: customized GPS
Optimized decay
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Customized G4 Radioactive Decay Module
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PET-specific sources
An example:
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Dual isotope scan
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Simulation for independent time frames
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/gate/source/addSource twogamma
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/gate/source/twogamma/setActivity
O and 11C0.00001 Ci
/gate/source/twogamma/setType backtoback
7000
/gate/source/twogamma/gps/centre
1. 0. 0. cm
6000
/gate/source/twogamma/gps/type
Volume
/gate/source/twogamma/gps/shape
Cylinder
5000
(RDM)
/gate/source/twogamma/gps/radius
1. cm
4000
/gate/source/twogamma/gps/halfz
.05 cm
3000
/gate/source/twogamma/gps/energytype
Mono
2000
/gate/source/twogamma/gps/monoenergy
0.511 MeV
1000
/gate/source/twogamma/gps/angtype
iso
0
/gate/source/twogamma/gps/mintheta
0
5
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1590. deg
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/gate/source/twogamma/gps/maxtheta
time (min) 90. deg
/gate/source/twogamma/gps/minphi
0. deg
/gate/source/twogamma/gps/maxphi
360. deg
/gate/source/twogamma/gps/particle gamma
counts
Source
management
/gate/source/addSource fluor18
/gate/source/fluor18/setActivity 5. becquerel
/gate/source/fluor18/gps/particle ion
/gate/source/fluor18/gps/ion 9 18 0 0
/gate/source/fluor18/gps/energytype Mono
/gate/source/fluor18/gps/monoenergy 0. MeV
/gate/source/fluor18/gps/angtype iso
/gate/source/fluor18/gps/number 1
/gate/source/fluor18/gps/centre 0. 0. 0. cm
/gate/source/fluor18/gps/type Volume
/gate/source/fluor18/gps/shape Sphere
/gate/source/fluor18/gps/radius 1. mm
/gate/source/fluor18/gps/confine head_P
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0-2 and 14-16 min
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/control/execute sourcemgr.mac
Timing
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GATE
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/gate/application/setTimeSlice
/gate/application/setTimeStart
/gate/application/setTimeStop
/gate/application/startDAQ
20 s
0.
80.
s
s
Simulation time
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A clock models the passing of time
during experiments
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The user defines the experiment
timing
Time-dependent objects
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Updated when time changes
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Allows programming of movement,
tracer kinetics...
0s
20s
40s
60s
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Sensitive volumes and digitisation
Hits
Digis
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Energy
response
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Centroid
readout
Threshold
Electronics
Pre-programmed components
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Spatial
response
Sensitive detectors
Trajectory analyser
Digitizer
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Linear signal processing chain
Modular: set-up via scripting
/gate/digitizer/modules/insert blurring
/gate/digitizer/blurring/setResolution 0.15
/gate/digitizer/modules/insert spblurring
/gate/digitizer/spblurring/setResolution 0.15
/gate/digitizer/modules/insert readout
/gate/digitizer/modules/insert thresholder
/gate/digitizer/thresholder/setThreshold 50. keV
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Data output
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Pluggable output modules
– Multiple parallel output channels ROOT, ASCII…
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GATE
– Include features for real-time display
/gate/output/plotter/showPlotter
/gate/output/plotter/setNColumns 2
/gate/output/plotter/setPlotHeight 250
/gate/output/plotter/setPlotWidth 300
/gate/output/plotter/addPlot hist Ion_decay_time_s
/gate/output/plotter/addPlot hist Positron_Kinetic_Energy_MeV
/gate/output/plotter/addPlot tree Singles compton
/gate/output/plotter/addPlot tree Coincidences energy1
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Output management
ASCII
ROOT
Binary format
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Validation
GATE
IASA gamma camera
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D. Lazaro, LPC-IN2P3, Clermont-Ferrand
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Several SPECT/gamma camera projects
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Clermont-Ferrand
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Ghent
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PET validation work to start soon
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Lausanne, ….
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Toward parallel computation
Input
file
GATE
on the
Grid
Data
base
file
GATE
Data
base
file
Input file exploding
Output file merging
Output
result file
Grid-GATE
output file
D. Lazaro, LPC-IN2P3, Clermont-Ferrand
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Computation speed is essential
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“Simple” geometry
But: voxels, huge number of events, …
Projects
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LAN parallelisation
Implementation on DATAGRID (W.I.P.)
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OpenGATE collaboration
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GATE
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G.Santin
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Shared development
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Optimal use of manpower and skills
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Long-term maintenance and support
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Coordination of efforts
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Multiple development axes: tool implementation, validation, …
Current composition
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10 groups
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Fields: SPECT, PET, PET
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Application: design, validation
All members contribute
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According to their interests and know-how
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On a best-effort basis
Coordination
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A spokesman
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Steering committee (one delegate/member)
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Technical meetings
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Summary
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On-going project
– Develop a versatile simulation platform for
PET/SPECT
– Build a shared-development collaboration
GATE
– Development and validation work on their way
G.Santin
The End
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For more info
http://www-iphe.unil.ch/~PET/research/gate/
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