[Gate-users] PET Count Rate simulations

[Hunor Kertesz]

Dear Gate users,

I am modelling the Siemens mMR PET/MR and the Siemens Biograph 64 True 
Point True View scanners.

For the Siemens mMR, I built my model based on the published values of 
Aklan et al 2015 
(http://iopscience.iop.org/article/10.1088/0031-9155/60/12/4731/meta)
and Delso et al 2011 (https://www.ncbi.nlm.nih.gov/pubmed/22080447).
You can find my digitizer below.

For the validation of the model I am following the NEMA protocol. When 
calculating the sensitivity of the system I get similar values compared 
to the published values, but for the count rate I experience a strange 
behaviour at low activities.

When I run a simulation using 48MBq, the number of random coincidences 
are higher with a factor of 0.7 compared the number of true 
coincidences. (~10.000->~17,000)

For the Siemens Biograph scanner I notice the same behaviour but less 
pronounced compared to the Siemens mMR.

I would like to ask if somebody did model one of these systems and could 
give me a hint?

Thank you!

Best regards,
Hunor Kertesz
Medical University of Vienna

#### Digitizer

/gate/digitizer/Singles/insert adder

/gate/digitizer/Singles/insert readout
/gate/digitizer/Singles/readout/setDepth 1

/gate/digitizer/Singles/insert timeResolution
/gate/digitizer/Singles/timeResolution/setTimeResolution 3.6 ns

/gate/digitizer/Singles/insert crystalblurring
/gate/digitizer/Singles/crystalblurring/setCrystalResolutionMin 0.15
/gate/digitizer/Singles/crystalblurring/setCrystalResolutionMax 0.35
/gate/digitizer/Singles/crystalblurring/setCrystalQE 0.8
/gate/digitizer/Singles/crystalblurring/setCrystalEnergyOfReference 511 
keV

/gate/digitizer/Singles/insert blurring
/gate/digitizer/Singles/blurring/setResolution 0.15
/gate/digitizer/Singles/blurring/setEnergyOfReference 511 keV

/gate/digitizer/Singles/insert thresholder
/gate/digitizer/Singles/thresholder/setThreshold 430 keV
/gate/digitizer/Singles/insert upholder
/gate/digitizer/Singles/upholder/setUphold 610 keV

/gate/digitizer/Singles/insert deadtime
/gate/digitizer/Singles/deadtime/setDeadTime 355 ns
/gate/digitizer/Singles/deadtime/setMode nonparalysable
/gate/digitizer/Singles/deadtime/chooseDTVolume module

/gate/digitizer/Coincidences/setWindow 5.9 ns
/gate/digitizer/Coincidences/setOffset 0. ns
/gate/digitizer/Coincidences/MultiplesPolicy takeWinnerOfGoods
/gate/digitizer/Coincidences/describe

/gate/digitizer/name delay
/gate/digitizer/insert coincidenceSorter
/gate/digitizer/delay/setWindow 5.9 ns
/gate/digitizer/delay/setOffset 50. ns
/gate/digitizer/delay/MultiplesPolicy takeWinnerOfGoods
/gate/digitizer/delay/describe

/gate/digitizer/name finalCoinc
/gate/digitizer/insert coincidenceChain
/gate/digitizer/finalCoinc/addInputName delay
/gate/digitizer/finalCoinc/addInputName Coincidences
/gate/digitizer/finalCoinc/usePriority true
/gate/digitizer/finalCoinc/insert deadtime
/gate/digitizer/finalCoinc/deadtime/setDeadTime 100 ns
/gate/digitizer/finalCoinc/deadtime/setMode nonparalysable
/gate/digitizer/finalCoinc/describe

/gate/digitizer/finalCoinc/insert buffer
/gate/digitizer/finalCoinc/buffer/setBufferSize 64 B
/gate/digitizer/finalCoinc/buffer/setReadFrequency 12 MHz
/gate/digitizer/finalCoinc/buffer/setMode 1

#### NEMA scatter phantom

/gate/world/daughters/name cylinderPhantom
/gate/world/daughters/insert cylinder
/gate/cylinderPhantom/geometry/setRmax   100 mm
/gate/cylinderPhantom/geometry/setRmin   0.0 mm
/gate/cylinderPhantom/geometry/setHeight 700 mm
/gate/cylinderPhantom/placement/setTranslation 0.0 0 0.0 cm
/gate/cylinderPhantom/setMaterial Polyethylene
/gate/cylinderPhantom/vis/setColor blue
/gate/cylinderPhantom/vis/forceSolid
/gate/cylinderPhantom/vis/setVisible 1

/gate/cylinderPhantom/daughters/name sourceCylinder
/gate/cylinderPhantom/daughters/insert cylinder
/gate/sourceCylinder/placement/setTranslation 0.0 -45 0.0 mm
/gate/sourceCylinder/geometry/setRmax 3.3 mm
/gate/sourceCylinder/geometry/setRmin 0.0 mm
/gate/sourceCylinder/geometry/setHeight 710 mm
/gate/sourceCylinder/setMaterial Air
/gate/sourceCylinder/vis/forceSolid
/gate/sourceCylinder/vis/setColor yellow
/gate/sourceCylinder/vis/setVisible 1

/gate/sourceCylinder/daughters/name tubeCylinder
/gate/sourceCylinder/daughters/insert cylinder
/gate/tubeCylinder/setMaterial Polyethylene
/gate/tubeCylinder/vis/setColor green
/gate/tubeCylinder/geometry/setRmax 2.4 mm
/gate/tubeCylinder/geometry/setRmin 1.5 mm
/gate/tubeCylinder/geometry/setHeight 700 mm
/gate/tubeCylinder/placement/setTranslation 0.0 0.0 0.0 mm
/gate/tubeCylinder/vis/forceSolid
/gate/tubeCylinder/vis/setVisible 1

#### NEMA cylinder scatter phantom source

/gate/source/addSource twogamma
/gate/source/twogamma/setActivity 45000000 becquerel
/gate/source/twogamma/setType backtoback
/gate/source/twogamma/setForcedHalfLife 6586.2 s
/gate/source/twogamma/gps/particle gamma
/gate/source/twogamma/gps/energytype Mono
/gate/source/twogamma/gps/monoenergy 511 keV

/gate/source/twogamma/gps/type Volume
/gate/source/twogamma/gps/shape Cylinder
/gate/source/twogamma/gps/radius 1.5 mm
/gate/source/twogamma/gps/halfz  350 mm
/gate/source/twogamma/gps/centre 0.0 -45.0 0. mm
/gate/source/twogamma/gps/angtype iso

/gate/source/list