[Gate-users] coincidences

[Pietrzyk, Uwe]

Hi Mattia,

there is nothing wrong, that you find much less coincidences than just half
the singles. Consider the requirement for true coincidences:
- the singles have to come from the same event,
- scattered photons might miss the threshold you have set
- there is absorption in the phantom and you lose one of the annihilation photons

Maybe it would be a good exercise if you use the PET benchmark
or have a look at the very simple EduGATE- examples you find on the GATE WEB-page,
like "Coin-Chan"

Hope this helps!

Kind regards and best wishes,

Uwe Pietrzyk
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On 22 Jun 2016, at 18:16, mattia cani <mattiacani at hotmail.it<mailto:mattiacani at hotmail.it>> wrote:


Hi everybody,

I am using Gate for my thesis project and now I am doing some simulations with a Derenzo phantom. I have a question about the expected number of coincidences. I am doing some short simulations just to understand how it works so I have 1s of time with 28 different sources of 5000 Bq each one. At the end of the simulation on the ROOT output I can see that we have about 22000 singles but just 1468 concidences, while I expected about 11000. Maybe the problem is the digitizer setting so I enclose that part of the code.


#    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 2.2 mus
/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 24. ns
/gate/digitizer/Coincidences/MultiplesPolicy         takeAllGoods
/gate/digitizer/Coincidences/setOffset 0. ns
/gate/digitizer/Coincidences/describe

/gate/digitizer/name delay
/gate/digitizer/insert coincidenceSorter
/gate/digitizer/delay/setWindow 24. ns
/gate/digitizer/delay/setOffset 500. ns
/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/describe




Thank you for your disposability

Best regards

Mattia

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