[Gate-users] Multiple sources

ambwani at bu.edu ambwani at bu.edu
Thu Nov 13 20:09:52 CET 2008

Dear Gate users,

I am trying to simulate an ECAT scanner with a cylindrical phantom that 
has 2 point sources of different F18 activity. The simulation executes 
without error, but as I look at the 2D sinograms, I dont see anything. 
They look empty.

When I run the execution with a single point source, the sinograms look 

Here is my macro :
#     E C A T
/gate/world/daughters/name ecat
/gate/world/daughters/insert cylinder
/gate/ecat/setMaterial Air
/gate/ecat/geometry/setRmax 44.2 cm
/gate/ecat/geometry/setRmin 41.2 cm
/gate/ecat/geometry/setHeight 15.52 cm

#     B L O C K
/gate/ecat/daughters/name block
/gate/ecat/daughters/insert box
/gate/block/placement/setTranslation 427.0 0.0 0.0 mm
/gate/block/geometry/setXLength 30.0 mm
/gate/block/geometry/setYLength 35.8594 mm
/gate/block/geometry/setZLength 38.7 mm
/gate/block/setMaterial Air

#       C R Y S T A L
/gate/block/daughters/name crystal
/gate/block/daughters/insert box
/gate/crystal/geometry/setXLength 30.0 mm
/gate/crystal/geometry/setYLength 4.4 mm
/gate/crystal/geometry/setZLength 4.75 mm
/gate/crystal/setMaterial BGO

#       R E P E A T    C R Y S T A L
/gate/crystal/repeaters/insert cubicArray
/gate/crystal/cubicArray/setRepeatNumberX 1
/gate/crystal/cubicArray/setRepeatNumberY 8
/gate/crystal/cubicArray/setRepeatNumberZ 8
/gate/crystal/cubicArray/setRepeatVector 0. 4.4942 4.85 mm

#       R E P E A T    BLOCK
/gate/block/repeaters/insert linear
/gate/block/linear/setRepeatNumber 4
/gate/block/linear/setRepeatVector 0. 0. 38.8 mm
/gate/block/repeaters/insert ring
/gate/block/ring/setRepeatNumber 72

#      T U N G S T E N    S H I E L D

#     A T T A C H    S Y S T E M
/gate/systems/ecat/block/attach block
/gate/systems/ecat/crystal/attach crystal

#       A T T A C H    C R Y S T A L  SD

/gate/world/daughters/name phantom
/gate/world/daughters/insert cylinder
/gate/phantom/setMaterial Water
/gate/phantom/vis/setColor green
/gate/phantom/geometry/setRmax   10.0 cm
/gate/phantom/geometry/setHeight 20. cm

#       EM  P R O C E S S
/gate/physics/gamma/selectRayleigh lowenergy
/gate/physics/gamma/selectPhotoelectric standard
/gate/physics/gamma/selectCompton standard

#       I N A C T I V E    S E C O N D A R Y   E L E C T R O N S
/gate/physics/setElectronCut 1. m

#       I N A C T I V E    X - R A Y S
/gate/physics/setXRayCut 1. GeV
/gate/physics/setDeltaRayCut 1. GeV


#       A D D E R
/gate/digitizer/Singles/insert adder

#       R E A D O U T
/gate/digitizer/Singles/insert readout
/gate/digitizer/Singles/readout/setDepth 1

#      E N E R G Y   B L U R R I N G
/gate/digitizer/Singles/insert blurring
/gate/digitizer/Singles/blurring/setResolution 0.26
/gate/digitizer/Singles/blurring/setEnergyOfReference 511. keV

#       E N E R G Y   C U T
/gate/digitizer/Singles/insert thresholder
/gate/digitizer/Singles/thresholder/setThreshold 250. keV
/gate/digitizer/Singles/insert upholder
/gate/digitizer/Singles/upholder/setUphold 750. keV

#       D E A D    T I M E
/gate/digitizer/Singles/insert deadtime
/gate/digitizer/Singles/deadtime/setDeadTime 3000000. ps
/gate/digitizer/Singles/deadtime/setMode paralysable
/gate/digitizer/Singles/deadtime/chooseDTVolume block

#       C O I N C I    S O R T E R
/gate/digitizer/Coincidences/setWindow 10. ns
/gate/digitizer/Coincidences/setOffset 0. ns

/gate/digitizer/name delay
/gate/digitizer/insert coincidenceSorter
/gate/digitizer/delay/setWindow 10. ns
/gate/digitizer/delay/setOffset 500. ns

/gate/digitizer/name finalCoinc
/gate/digitizer/insert coincidenceChain
/gate/digitizer/finalCoinc/addInputName delay
/gate/digitizer/finalCoinc/addInputName Coincidences
/gate/digitizer/finalCoinc/usePriority true

##### Here I define the outputs I want ####

/gate/source/addSource F18CylinderSource
/gate/source/F18CylinderSource/setActivity 10000000. becquerel
/gate/source/F18CylinderSource/gps/particle e+
/gate/source/F18CylinderSource/setForcedUnstableFlag true
/gate/source/F18CylinderSource/setForcedHalfLife 6586 s
/gate/source/F18CylinderSource/gps/energytype Fluor18
/gate/source/F18CylinderSource/gps/type Volume
/gate/source/F18CylinderSource/gps/shape Cylinder
/gate/source/F18CylinderSource/gps/radius 3 mm
/gate/source/F18CylinderSource/gps/halfz 0.5 mm
/gate/source/F18CylinderSource/gps/angtype iso
/gate/source/F18CylinderSource/gps/centre 0.0 0.0 0. cm

/gate/source/addSource F18Cylinder
/gate/source/F18Cylinder/setActivity 100000. becquerel
/gate/source/F18Cylinder/gps/particle e+
/gate/source/F18Cylinder/setForcedUnstableFlag true
/gate/source/F18Cylinder/setForcedHalfLife 6586 s
/gate/source/F18Cylinder/gps/energytype Fluor18
/gate/source/F18Cylinder/gps/type Volume
/gate/source/F18Cylinder/gps/shape Cylinder
/gate/source/F18Cylinder/gps/radius 5 mm
/gate/source/F18Cylinder/gps/halfz 1 mm
/gate/source/F18Cylinder/gps/angtype iso
/gate/source/F18Cylinder/gps/centre 0.0 0.0 0. cm

/gate/application/setTimeSlice     1.  s
/gate/application/setTimeStart     0.   s
/gate/application/setTimeStop      1.  s


What I want actually is to have a high activity source against a low 
activity background. The sinograms I got were nothing like I expected. 
Maybe the acquisition time is too small, so I am running a big 
simulation also. But overall, I tried a bunch of different 
combinations. 2 point sources off center with same activity.....2 point 
sources off center with different activities....a single point source 
on or off center. I check the sinograms at the end of each sim, and 
only the single point source cases look appropriate.

Could someone point out what I am missing? I'd appreciate any help.


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