[Gate-users] question about the coincidence window

[yuxuan.zhang at di.mdacc.tmc.edu]

Hi, Fernando and Yu,

Thank you for your comments.

First I agree with Fernando for this statement:
" If an event arrives at time t, then a coincidence will be
counted for en event in [t-tau] or [t+tau] but not [t+2tau] or [t-2tau]"

Sencond, I would explain a little more. In Gate, according to the 
algorithm been used
((newPulse->GetTime()>=m_startTime+m_offsetWindow) && 
(newPulse->GetTime()<(m_startTime+m_offsetWindow+m_coincidenceWindow)) ,
when we setup the parameter by the command 
"/gate/digitizer/Coincidences/setWindow", we should set the value as tau, 
not two tau.
When the PET manufacturer provides the specification of "coincidence 
window", they mean two tau. This is the difference.







Fernando Rannou <rannou at diinf.usach.cl>
04/26/2007 11:28 AM

 
        To:     "Chen, Yu" <Yu.Chen at umassmed.edu>
        cc:     yuxuan.zhang at di.mdacc.tmc.edu, gate-users at lists.healthgrid.org
        Subject:        RE: [Gate-users] question about the coincidence window


This issue was discussed 3 years ago. I asked a very similar
question when I wanted to compare random rates using two approaches.

If an event arrives at time t, then a coincidence will be
counted for en event in [t-tau] or [t+tau] but not [t+2tau] or [t-2tau]


Fernando Rannou

On Thu, 2007-04-26 at 12:14 -0400, Chen, Yu wrote:
> 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
> 
> 
> 
> 
> 
> -- 
> Este mensaje ha sido analizado por MailScanner 
> en busca de virus y otros contenidos peligrosos, 
> y se considera que está limpio. 
> MailScanner agradece a transtec Computers por su apoyo. 
> _______________________________________________
> Gate-users mailing list
> Gate-users at lists.healthgrid.org
> http://lists.healthgrid.org/mailman/listinfo/gate-users


-- 
Este mensaje ha sido analizado por MailScanner
en busca de virus y otros contenidos peligrosos,
y se considera que est�impio.
MailScanner agradece a transtec Computers por su apoyo.




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20070427/a32f2c6f/attachment.htm>