[gate-users] Energy problem has been solved

[Schmidtlein, Ross/Sloan-Kettering Institute]

Hi Sandor,

As I understand it (I have fiddled with this a little bit), there are 2
QE modules in the digitizer.  The general QE seems to randomly remove
events according to the value you have set.  The other module cuts the
energy of the collected events by the value set.  The second model is
probably more realistic but it forces you to rescaled the energy on
crystal location basis in order for the thresholders to work properly.  

Below is a past post where had the same problem.  I solve this problem
by generating a Singles file where I used a root script to strip out the
unwanted events and then used a second script to turn the singles back
into hits so that I could run the remaining singles through the
digitizer.

ross

**************************
Martin Rey wrote:
Hi Ross,

It is actually what it does. In fact, as the scintillation photons are
not simulated in Gate (until now), it seemed righter to me to reduce the
energy of the pulse. In fact, the result will be rather something
proportional to the scintillation photon number than energy. I used it
to simulate the differences between the peak position of our pixels
observed on real data. Than, I could apply a kind of hardware threshold
(the same for all pixels) and then did a re-calibration in energy. I
hope you understood my explanation.

Schmidtlein, Ross/Sloan-Kettering Institute wrote:

>I am looking at how to mimic the behavior of a detector block (6x6
>crystals) by cutting some of the events in the corners and edges of the

>block.  I was trying to use the following commands:
>
>/gate/digitizer/Singles/insert quantumEfficiency 
>/gate/digitizer/Singles/quantumEfficiency/chooseQEVolume crystal 
>/gate/digitizer/Singles/quantumEfficiency/useFileDataForQE QE.dat
>
>Where QE.dat contains 36 numbers ranging from .5 to 1.0.
>
>Instead of randomly cutting events this command seems to be reducing 
>the energy per event in proportion to the QE.dat table.  Is this what 
>this command is supposed to be doing?  It doesn't look that way in the 
>users guide.  Does anyone have any ideas?  I'm hoping to avoid digging 
>through the code. ;)
>
>Thanks,
>
>ross
************************

-----Original Message-----
From: gate-users-bounces at lphe1pet1.epfl.ch
[mailto:gate-users-bounces at lphe1pet1.epfl.ch] On Behalf Of Kis Sandor
Attila
Sent: Thursday, February 09, 2006 9:44 AM
To: gate-users at lphe1pet1.epfl.ch
Subject: [gate-users] Energy problem has been solved


Dear Gate users,

I found that the small energy problem solved when I turned off the
quantum efficiency module. That is the detected gamma energy in this way
increased to the expected 511 KeV level from the perviously simulated
rate, scattered around 100 Kev (with quantum efficienci module on). Have
any of you encountered with this problem?

regards,

-----------------
Sandor Attila Kis
II. Ph.D. physicist
University of Debrecen, PET Centrum
tel.:(52)411600 /51398
mob.:(20)9215522


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