[Gate-users] Digitizer

[Cristian C]

Dear all,

I'm simulating a SPECT system and I have some doubts regarding the output ascii data files. I've included spatial resolution, quantum efficiency and dead time and, from all the data files produced I focus on two of them: "Singles.dat" and "SinglesSpblurring.dat", which have a different number of entries. As an example, I've run a short simulation which has produced 2305 entries in the "Singles" file and 2344 in the "SinglesSpblurring" file. When I include quantum efficiency these two values remain the same, even if I set "setUniqueQE 0.", in which case I would expect to have no entries. In addition, if I also include a dead time, the number of entries in the "Singles" file is 2188, whereas the number of entries in the "SinglesSpblurring" file doesn't change (it's still 2344, as before). My questions are:

1) Why do we have a different number of entries in the "Singles" and "SinglesSpblurring" files?
2) Why adding QE doesn't change the number of entries in this case? How can I then reduce the detected number of photons?
3) Why the dead time affects the "Singles" file but not the "SinglesSpblurring" file?

Below I've copied the lines I use to produce the digitizer. I would really appreciate your help.
Thanks,
Cristian.



# D I G I T I Z E R
#####
# ADDER
/gate/digitizer/Singles/insert adder                          

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

# ENERGY BLURRING
/gate/digitizer/Singles/insert blurring                         
/gate/digitizer/Singles/blurring/setResolution 0.10             
/gate/digitizer/Singles/blurring/setEnergyOfReference 140. keV

# SPATIAL BLURRING
/gate/digitizer/Singles/insert spblurring                       
/gate/digitizer/Singles/spblurring/setSpresolution 1.54 mm      
/gate/digitizer/Singles/spblurring/verbose 0

# THRESHOLD ELECTRONICS
/gate/digitizer/Singles/insert thresholder                      
/gate/digitizer/Singles/thresholder/setThreshold 20. keV
/gate/digitizer/Singles/insert upholder                        
/gate/digitizer/Singles/upholder/setUphold 190. keV 

# DEFINE TRANSFER EFFICIENCY FOR EACH LAYER 
/gate/digitizer/Singles/insert transferEfficiency 
/gate/digitizer/Singles/transferEfficiency/chooseNewVolume sensible_crystal 
/gate/digitizer/Singles/transferEfficiency/sensible_crystal/setTECoef 0.28 

# DEFINE LIGHT YIELD FOR EACH LAYER 
/gate/digitizer/Singles/insert lightYield 
/gate/digitizer/Singles/lightYield/chooseNewVolume sensible_crystal
/gate/digitizer/Singles/lightYield/sensible_crystal/setLightOutput 27000 

# DEFINE QUANTUM EFFICIENCY OF THE PHOTODETECTOR 
/gate/digitizer/Singles/insert quantumEfficiency 
/gate/digitizer/Singles/quantumEfficiency/chooseQEVolume sensible_crystal 
/gate/digitizer/Singles/quantumEfficiency/setUniqueQE 0.19

# DEADTIME 
#/gate/digitizer/Singles/insert deadtime 
#/gate/digitizer/Singles/deadtime/setDeadTime 0.1 ms 
#/gate/digitizer/Singles/deadtime/setMode paralysable 
#/gate/digitizer/Singles/deadtime/chooseDTVolume sensible_crystal