[Gate-users] question about the coincidence window

[Chen, Yu]

Hi, Yuxuan,

nice question.
I have not any experience on coincidence package in GATE since
I use our standalone coincidence program from GATE singles output, and
we can have complete control such as choosing of paralyzable or nonparalyzable
model.

In my opinion, coincidence window is an very important parameter in any
coincidence experiment. It must be allowed to easily changed by users either
for GATE or for any specific PET scanner. 

I do not completely understand what you said here for single pulse width.

Do you talk about width of two singles or coincidence output signal?

If about width of single photon pulse, I do not think this width should be
directly associated with coincidence window. As I know, GATE only gives a time stamp 
to any particular singles since no electronics response is simulated in GATE. 

If about width of coincidence signal, why are you bothered with it? What you need is
a count which is only dependent on coincidence window and model in GATE, and of course
in real scanner also dependent on the width of two single pulses. As long as you set 
your coincidence window greater than twice of single pulse width, coincidence count would
be no longer dependent on single pulse width.   

For GATE application, what you need to do is to use the same parameters from your real scanner,
e.g., 10 ns coincidence window, paralyzable model to get the same results.

Hope it helps.

Yu Chen, Ph.D.
University of Massachusetts Medical School
Division of Nuclear Medicine
55 Lake Avenue North
Worcester, MA 01655-0243
Phone:  (508) 856-6123
Fax:    (508) 856-4572



-----Original Message-----
From: gate-users-bounces at lists.healthgrid.org on behalf of yuxuan.zhang at di.mdacc.tmc.edu
Sent: Wed 4/25/2007 6:35 PM
To: gate-users at lists.healthgrid.org
Subject: [Gate-users] question about the coincidence window
 
hi All,

I have a question about the definition of the coincidence time window, 
which might be
different among the GATE society and the nuclear electronics people.

According to the GATE user's manual, the coincidence window is the width 
of the single pulse,
however, according to some literature and electronics engineering people, 
the coincidence windows
are defined as twice of the width of the single pulse. So if they say one 
PET camera has a 
coincidence window of 10 ns, this should mean that the width of the single 
pulse is 5 ns. 
If this is the case, then we should setup the coincidence window in GATE 
simulation as 5 ns 
rather than 10 ns.

I've checked several published papers about the validation of the GATE, no 
one has made any comment
on this issue explicitly. So I brought this to you attention and hope you 
can give some comments.

Best regards,

Yuxuan


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