[Gate-users] Number of counts too low

Tue Nov 10 16:57:35 CET 2020

Dear Maxime,

once again, thank you for your reply. Of course I understand that you wont
read a full set of mac files. Nevertheless, I havent found a publication
yet with reproducible GATE  settings for a validated model, let alone a
validated model which is available online. Do you know of a GATE model which
was validated with the NEMA NEC measurements you can point me to?

Thank you in advance,

Kind regards,

Nicole

Von: Gate-users <gate-users-bounces at lists.opengatecollaboration.org> Im
Auftrag von Maxime Toussaint
Gesendet: Dienstag, 10. November 2020 16:46
An: gate-users at lists.opengatecollaboration.org
Betreff: Re: [Gate-users] Number of counts too low

Greetings,

In short, I don't know. It could be too many thing since I am missing a
great portion of your simulation configuration. As it stand, I am not even
sure if the problem is in the choice of digitizer. 

Most, including I, won't take the time to analyze/read a complete list of
mac files. Thus, I suggest that you start from one of Gate example, which we
know should work, and slowly replace it with your simulation configuration
(Or do the reverse). This way, you will be able to "find" the part, 3-4
lines, from where the problem is born.

Good luck in your hunt!

Bests,

Maxime Toussaint

  _____  

De : nicole.jurjew at gmail.com <mailto:nicole.jurjew at gmail.com>
<nicole.jurjew at gmail.com <mailto:nicole.jurjew at gmail.com> >
Envoyé : 10 novembre 2020 05:47
À : Maxime Toussaint <Maxime.Toussaint at USherbrooke.ca
<mailto:Maxime.Toussaint at USherbrooke.ca> >;
gate-users at lists.opengatecollaboration.org
<mailto:gate-users at lists.opengatecollaboration.org>
<gate-users at lists.opengatecollaboration.org
<mailto:gate-users at lists.opengatecollaboration.org> >
Objet : AW: [Gate-users] Number of counts too low 

Dear Maxime,

thank you for your reply!

I tried your suggestions out: The DTVolume level changes the number of
counts a little, but by far not significantly (about 0.5% more counts where
I need around 50% more for low energies). I also ran with the most simple
digitizer: no energy blurring, no time resolution or dead time added. I get
the same results: about 0.5 % increase of counts, but no significant
changes.

Do you maybe have any other ideas why I get too little counts?

Thank you!

Kind regards,

Nicole

Von: Gate-users <gate-users-bounces at lists.opengatecollaboration.org
<mailto:gate-users-bounces at lists.opengatecollaboration.org> > Im Auftrag von
Maxime Toussaint
Gesendet: Dienstag, 10. November 2020 05:18
An: gate-users at lists.opengatecollaboration.org
<mailto:gate-users at lists.opengatecollaboration.org> 
Betreff: Re: [Gate-users] Number of counts too low

Greetings,

I have never used the deadtime module, but are you sure about your choice
for the following?

"""

/gate/digitizer/Singles/deadtime/chooseDTVolume rsector

"""

It seems to be to "low" in "geometry level" for classical scanner
configuration.

If yes, did you try to simplify (e.g. remove dead time) of your digitizer to
find the origin of the problem? 

Bests,

Maxime Toussaint

  _____  

De : Gate-users <gate-users-bounces at lists.opengatecollaboration.org
<mailto:gate-users-bounces at lists.opengatecollaboration.org> > de la part de
Nicole Jurjew <nicole.jurjew at gmail.com <mailto:nicole.jurjew at gmail.com> >
Envoyé : 6 novembre 2020 06:32
À : gate-users at lists.opengatecollaboration.org
<mailto:gate-users at lists.opengatecollaboration.org>
<gate-users at lists.opengatecollaboration.org
<mailto:gate-users at lists.opengatecollaboration.org> >
Objet : [Gate-users] Number of counts too low 

Dear Gate Users!

I am using GATE v.8.0 to model a preclinical PET system. I carried out the
NEMA - NEC measurements on the real scanner and also simulated them in GATE.
The curves don't look much alike. The simulation produces significantly less
counts than what is detected with the real system.

I determined the number of gamma particles entering my crystal with the
"Kill Tracks" Actor. (I always ran one simulation to count the Nb of tracks
killed in the crystal and one where no tracks are killed to be able to
calculate the Nb of prompts generated.)

An activity of 0.58 MBq inside a polyethylene cylinder results in a total
number of ~21.000 counts with the digitizer settings you can see below.
Number of killed gamma particles is ~855000.
Energy window, coincidence timing window and dead time are set to align
with specifications given by the vendor. I tried out many different
digitizer settings, but none of them leads to a result close to the
measurements, also not for higher activities up to 40 MBq.

Do you have an idea where too little counts could come from?

Thank you in advance!
Nicole Jurjew

### DIGITIZER ###

/gate/digitizer/Singles/insert adder
/gate/digitizer/Singles/insert readout
/gate/digitizer/Singles/readout/setPolicy TakeEnergyWinner
/gate/digitizer/Singles/readout/setDepth 1

/gate/digitizer/Singles/insert blurring
/gate/digitizer/Singles/blurring/setResolution 0.1
/gate/digitizer/Singles/blurring/setEnergyOfReference 511. keV

/gate/digitizer/Singles/insert thresholder
/gate/digitizer/Singles/thresholder/setThreshold 250.39 keV
/gate/digitizer/Singles/insert upholder
/gate/digitizer/Singles/upholder/setUphold 771.61 keV

# C O I N C I    S O R T E R 
/gate/digitizer/Coincidences/setWindow 7. ns
/gate/digitizer/Coincidences/MultiplesPolicy  takeWinnerOfGoods

/gate/digitizer/name                            delay
/gate/digitizer/insert                          coincidenceSorter
/gate/digitizer/delay/setWindow                 7. ns
/gate/digitizer/delay/setOffset                 20 ns

# TIME RESOLUTION
/gate/digitizer/Singles/insert timeResolution
/gate/digitizer/Singles/timeResolution/setTimeResolution 0.5 ns 

#   DEAD TIME
/gate/digitizer/Singles/insert deadtime
/gate/digitizer/Singles/deadtime/setDeadTime 850. ns
/gate/digitizer/Singles/deadtime/setMode nonparalysable
/gate/digitizer/Singles/deadtime/chooseDTVolume rsector

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