[Gate-users] Too high count rates in thyroid scintigraphy simulations
Träuble, Korbinian Linus
korbinian.traeuble at tum.de
Mon Aug 29 10:44:01 CEST 2022
Dear all,
I’m a master student and try to replicate the Thyroid Gamma camera Mediso Nucline TH-22 with GATE. Therefore I’ve 3d printed a phantom, made a CT of it, filled it with Tc99m and water, and acquired some measurements of it.
For the source, I am using the segmented CT scan of the phantom and specified the activity filled into the phantom with the labels.
Now, I am facing the problem that the simulation of the measurement in GATE yield much higher count rates (by roughly 60%) than the original measurement. I was playing around with all kind of things in GATE, but did not yet get a better result. I have also checked for overlapping geometries already.
Have I missed something at the camera model that would reduce count rates? Is my physics model wrong or did I define my source wrong? There is also the possibility that there is something wrong with my experiment setup, and not with my GATE simulation.
I have attached some screenshots of the phantom and the source mhd files.
Any help is highly appreciated. Maybe I’m missing something obvious.
Cheers,
Korbinian Träuble
Code:
### MANDATORY
/gate/geometry/setMaterialDatabase {dataDir}/GateMaterials.db
### World
/gate/world/setMaterial Air
/gate/world/geometry/setXLength 50 cm
/gate/world/geometry/setYLength 50 cm
/gate/world/geometry/setZLength 50 cm
### Camera model
## Scanner Head
/gate/world/daughters/name SPECThead
/gate/world/daughters/insert box
/gate/SPECThead/geometry/setXLength 300 mm
/gate/SPECThead/geometry/setYLength 120 mm
/gate/SPECThead/geometry/setZLength 300 mm
/gate/SPECThead/placement/setTranslation 0 -61.75 0 mm
/gate/SPECThead/setMaterial Air
## CRYSTAL
/gate/SPECThead/daughters/name crystal
/gate/SPECThead/daughters/insert box
/gate/crystal/geometry/setXLength 230 mm
/gate/crystal/geometry/setYLength 6.4 mm
/gate/crystal/geometry/setZLength 210 mm
/gate/crystal/placement/setTranslation 0. 0. 0. mm
/gate/crystal/setMaterial NaITl
/gate/crystal/vis/setColor red
## Collimator
/gate/SPECThead/daughters/name collimator
/gate/SPECThead/daughters/insert box
/gate/collimator/geometry/setXLength 230 mm
/gate/collimator/geometry/setYLength 55 mm
/gate/collimator/geometry/setZLength 210 mm
/gate/collimator/placement/setTranslation 0. 30.7 0. mm
/gate/collimator/setMaterial Tungsten
/gate/collimator/vis/setColor yellow
/gate/collimator/vis/forceWireframe
#For Parallel Hexagonal holes:
/gate/collimator/daughters/name hole1
/gate/collimator/daughters/insert hexagone
/gate/hole1/geometry/setHeight 55 mm
/gate/hole1/geometry/setRadius 1.5 mm
/gate/hole1/placement/setRotationAxis 1 0 0
/gate/hole1/placement/setRotationAngle 90 deg
/gate/hole1/setMaterial Air
/gate/hole1/vis/setColor blue
/gate/hole1/vis/forceWireframe
# Repeat the hexagone in an array to achieve frame
/gate/hole1/repeaters/insert cubicArray
/gate/hole1/cubicArray/setRepeatNumberX 41
/gate/hole1/cubicArray/setRepeatNumberY 1
/gate/hole1/cubicArray/setRepeatNumberZ 65
/gate/hole1/cubicArray/setRepeatVector 5.542562584 0.0 3.2 mm
/gate/hole1/vis/forceWireframe
/gate/hole1/repeaters/insert linear
/gate/hole1/linear/setRepeatNumber 2
/gate/hole1/linear/setRepeatVector 2.771281292 0.0 1.6 mm
#Attach sensitive detector crystal to SPECThead
/gate/systems/SPECThead/crystal/attach crystal
/gate/crystal/attachCrystalSD
/gate/systems/SPECThead/describe
### PHANTOM
# Import the Thyroid Volume from the metaimage file
/gate/world/daughters/name patient_thyroid
/gate/world/daughters/insert ImageNestedParametrisedVolume
/gate/patient_thyroid/geometry/setImage {pathphantom}
/gate/patient_thyroid/geometry/setRangeToMaterialFile {dataDir}/AttenuationRange.dat
/gate/patient_thyroid/placement/setTranslation 43.5 41.0 -0.8 mm
AttenuationRange.dat
3
-2000 -10 Air
-10 1 Water
1 2000 PETG
## PHYSICS
/gate/physics/addPhysicsList emstandard_opt4
##ACTORS
/gate/actor/addActor SimulationStatisticActor stat
/gate/actor/stat/save {outputFolder}/stat.txt
/gate/actor/stat/saveEveryNSeconds 20
/gate/actor/addActor EnergySpectrumActor MyActor
/gate/actor/MyActor/save {outputFolder}/MyOutputFile.txt
/gate/actor/MyActor/energySpectrum/setEmin 50 keV
/gate/actor/MyActor/energySpectrum/setEmax 200 keV
/gate/actor/MyActor/energySpectrum/setNumberOfBins 300
/gate/actor/MyActor/attachTo crystal
/gate/actor/MyActor/saveAsText true
### INITIALIZATION :
/gate/run/initialize
### SOURCE
/gate/source/addSource thyroidSource voxel
/gate/source/thyroidSource/reader/insert image
/gate/source/thyroidSource/imageReader/translator/insert range
/gate/source/thyroidSource/imageReader/rangeTranslator/readTable {dataDir}/ActivityRange.dat
/gate/source/thyroidSource/imageReader/rangeTranslator/describe 1
/gate/source/thyroidSource/imageReader/readFile {pathsource}
/gate/source/thyroidSource/imageReader/verbose 1
/gate/source/thyroidSource/setPosition -36.412 -13.887 -33.5 mm
/gate/source/thyroidSource/dump 1
/gate/source/thyroidSource/attachTo patient_thyroid
/gate/source/thyroidSource/gps/particle gamma
/gate/source/thyroidSource/gps/ene/type Mono
/gate/source/thyroidSource/gps/ene/mono 140.5 keV
/gate/source/thyroidSource/gps/ang/type iso
/gate/source/thyroidSource/gps/pos/confine NULL
/gate/source/thyroidSource/setForcedUnstableFlag true
/gate/source/thyroidSource/setForcedHalfLife 21636 s #1 s 6h half-life
ActivityRange.dat:
4
1 1 2.5493227313607107
2 2 0
3 3 7.584677308945539
4 4 0
### DIGITIZER
#Energyblurring
/gate/digitizer/Singles/insert adder
/gate/digitizer/Singles/insert readout
/gate/digitizer/Singles/readout/setDepth 1
/gate/digitizer/Singles/insert blurring
/gate/digitizer/Singles/blurring/setLaw inverseSquare
/gate/digitizer/Singles/blurring/inverseSquare/setResolution 0.1 #0.08 default, 0.095 bisher immer
/gate/digitizer/Singles/blurring/inverseSquare/setEnergyOfReference 140.5 keV
#spatialblurring
/gate/digitizer/Singles/insert spblurring
/gate/digitizer/Singles/spblurring/setSpresolution 3.2 mm
/gate/digitizer/Singles/spblurring/verbose 0
#threshholder
/gate/digitizer/Singles/insert thresholder
/gate/digitizer/Singles/thresholder/setThreshold 126.45 keV
/gate/digitizer/Singles/insert upholder
/gate/digitizer/Singles/upholder/setUphold 154.55 keV
### OUTPUT
/gate/output/projection/enable
/gate/output/projection/setFileName {outputFolder}/projection
/gate/output/projection/pixelSizeX 0.9 mm
/gate/output/projection/pixelSizeY 0.9 mm
/gate/output/projection/pixelNumberX 256
/gate/output/projection/pixelNumberY 256
/gate/output/projection/projectionPlane ZX
/gate/output/tree/enable
/gate/output/tree/addFileName {outputFolder}/output.npy
/gate/output/tree/addCollection Singles
### RANDOM
/gate/random/setEngineName Ranlux64
/gate/random/setEngineSeed 123456789
### EXPERIMENT
/gate/application/setTimeSlice 300 s
/gate/application/setTimeStart 0 s
/gate/application/setTimeStop 300 s
# L E T' S R U N T H E S I M U L A T I O N !
/gate/application/startDAQ
[cid:A0BDFB23-71F3-4335-80FE-56C1A9F49640][cid:AC3D6207-94AA-4D29-B9B7-AAEFBEA9CDD4]
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