[Gate-users] with and without nanoparticules -> surprising output

[Sarah Blind]

Dear Gate users, 

I want to model a spheroid which contains 30 000 cells in each of which there are 10 clusters of 10 nanoparticles. 
The composition of my nanoparticles is the following 




+el: name=Gadolinium ; f=0.15 
+el: name=Silicon ; f=0.10 
+el: name=Carbon ; f=0.25 
+el: name=Nitrogen ; f=0.08 
+el: name=Oxygen ; f=0.22 
+el: name=Hydrogen ; f=0.20 




My spheroid, the cells and the clusters are all spheres full with water. 
For the moment, what I'm trying to observe is very simple : with and without the nanoparticles (and thus only water) I should observe a difference, shouldn't I ? 

I use Geant4-DNA; with 10 000 000 photons sent ; here is what my .hdr outpout file looks like 

Nanoparticles 
	Average in Gy 

No 
	0.002 

Yes 
	
0.001 


There is almost no difference between with and without the nanoparticles, this surprises me. 


I'm not a physicist, do you find this normal ? 


Here is my Gate code : 




BQ_BEGIN


======= world.mac ======= 


/gate/world/geometry/setXLength 0.5 cm 
/gate/world/geometry/setYLength 0.5 cm 
/gate/world/geometry/setZLength 0.5 cm 
/gate/world/setMaterial Air 


/gate/world/daughters/name spheroide 
/gate/world/daughters/insert sphere 
/gate/spheroide/geometry/setRmin 0.0 mm 
/gate/spheroide/geometry/setRmax 400 um 
/gate/spheroide/placement/setTranslation 0 0 0 mm 
/gate/spheroide/setMaterial G4_WATER 
/gate/spheroide/vis/setVisible 1 
/gate/spheroide/vis/setColor blue 
/gate/spheroide/vis/forceSolid false 


/gate/spheroide/daughters/name cell 
/gate/spheroide/daughters/insert sphere 
/gate/cell/geometry/setRmin 0.0 mm 
/gate/cell/geometry/setRmax 10 um 
/gate/cell/placement/setTranslation 100 0 0 um 
/gate/cell/setMaterial G4_WATER 
/gate/cell/vis/setVisible 1 
/gate/cell/vis/setColor green 
/gate/cell/vis/forceSolid false 

/gate/cell/daughters/name cluster 
/gate/cell/daughters/insert sphere 
/gate/cluster/geometry/setRmin 0 mm 
/gate/cluster/geometry/setRmax 0.05 um 
/gate/cluster/placement/setTranslation 0 0 0 mm 
/gate/cluster/setMaterial G4_WATER 
/gate/cluster/vis/setVisible 1 
/gate/cluster/vis/setColor yellow 
/gate/cluster/vis/forceSolid false 

/gate/cluster/daughters/name NP 
/gate/cluster/daughters/insert sphere 
/gate/NP/geometry/setRmin 0 mm 
/gate/NP/geometry/setRmax 0.004 um 
/gate/NP/placement/setTranslation 0 0 0 mm 
/gate/NP/setMaterial AGuIX 
/gate/NP/vis/setVisible 1 
/gate/NP/vis/setColor red 
/gate/NP/vis/forceSolid true 

### repeaters ### 

/gate/NP/repeaters/insert genericRepeater 
/gate/NP/genericRepeater/setPlacementsFilename ../data/NP.placements 
/gate/NP/genericRepeater/useRelativeTranslation 1 

/gate/cluster/repeaters/insert genericRepeater 
/gate/cluster/genericRepeater/setPlacementsFilename ../data/cluster.placements 
/gate/cluster/genericRepeater/useRelativeTranslation 1 


/gate/cell/repeaters/insert cubicArray 
/gate/cell/cubicArray/setRepeatNumberX 32 
/gate/cell/cubicArray/setRepeatNumberY 32 
/gate/cell/cubicArray/setRepeatNumberZ 32 
/gate/cell/cubicArray/setRepeatVector 20 20 20 um 



======= physics.mac ======= 



# Geant4-DNA 
/gate/physics/addPhysicsListMixed emstandard_opt3_mixed_emdna 
/gate/physics/SetDNAInRegion spheroide 
/gate/physics/ConstructProcessMixed 

/gate/physics/Gamma/SetCutInRegion world 0.5 mm 
/gate/physics/Electron/SetCutInRegion world 0.5 mm 
/gate/physics/Positron/SetCutInRegion world 0.5 mm 

/gate/physics/displayCuts 

# Choice of pseudo-random number generation algorithm 
/gate/random/setEngineName MersenneTwister 

# Auger electron activation 
/gate/physics/addAtomDeexcitation 


/gate/physics/addProcess PhotoElectric gamma 
/gate/physics/processes/PhotoElectric/setModel LivermoreModel 
/gate/physics/processes/PhotoElectric/setAugerElectron true 
/gate/physics/processes/PhotoElectric/setDeltaRayCut 10 eV 
/gate/physics/processes/PhotoElectric/setXRayCut 10 eV 
/gate/physics/processes/PhotoElectric/setStepFunction e- 0.2 0.1 nm 

/gate/physics/addProcess Compton gamma 
/gate/physics/processes/Compton/setModel LivermoreModel 
/gate/physics/processes/Compton/setStepFunction e- 0.2 0.1 nm 

/gate/physics/addProcess RayleighScattering 
/gate/physics/processes/RayleighScattering/setModel LivermoreModel 

# transformation of a photon into an electron-positron pair 

/gate/physics/addProcess GammaConversion 
/gate/physics/processes/GammaConversion/setModel LivermoreModel 

/gate/physics/addProcess ElectronIonisation 
/gate/physics/processes/ElectronIonisation/setModel LivermoreModel e- 
/gate/physics/processes/ElectronIonisation/setModel PenelopeModel e+ 
/gate/physics/processes/ElectronIonisation/setStepFunction e- 0.2 0.1 nm 

/gate/physics/addProcess Bremsstrahlung e- 
/gate/physics/addProcess Bremsstrahlung e+ 
/gate/physics/processes/Bremsstrahlung/setModel LivermoreModel e- 
/gate/physics/processes/Bremsstrahlung/setModel PenelopeModel e+ 

/gate/physics/addProcess eMultipleScattering e- 
/gate/physics/addProcess eMultipleScattering e+ 
/gate/physics/processes/eMultipleScattering/setModel UrbanModel e- 
/gate/physics/processes/eMultipleScattering/setModel UrbanModel e+ 




======= detectors.mac ======= 





/gate/actor/addActor DoseActor dose 
/gate/actor/dose/save output/dose.hdr 
/gate/actor/dose/attachTo spheroide 
/gate/actor/dose/stepHitType random 
/gate/actor/dose/setPosition 0.0 0.0 0.0 mm 
/gate/actor/dose/setSize 800 800 800 um 
/gate/actor/dose/setResolution 400 400 400 
/gate/actor/dose/enableDose true 
/gate/actor/dose/saveEveryNSeconds 30 




======= source.mac ======= 





/gate/source/addSource mybeam gps 
/gate/source/mybeam/gps/particle gamma 
/gate/source/mybeam/gps/pos/type Beam 
/gate/source/mybeam/gps/ene/mono 170 keV 
/gate/source/mybeam/gps/ene/type Gauss 
/gate/source/mybeam/gps/ene/sigma 1.0 keV 
/gate/source/mybeam/gps/direction 0 0 -1 

/gate/source/mybeam/gps/position 0 0 0.2 cm 
/gate/source/mybeam/gps/pos/type Volume 
/gate/source/mybeam/gps/pos/shape Cylinder 
/gate/source/mybeam/gps/pos/inner_radius 0 mm 
/gate/source/mybeam/gps/pos/radius 500 um 
/gate/source/mybeam/gps/pos/halfz 0.01 cm 
/gate/source/mybeam/gps/ang/type beam2d 



BQ_END


Thank you for your help, 

Sarah Blind 




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