Hi, Fernando and Yu, Thank you for your comments. First I agree with Fernando for this statement: " <tt>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]"</tt> <tt>Sencond, I would explain a little more. In Gate, according to the algorithm been used</tt> <tt>((newPulse->GetTime()>=m_startTime+m_offsetWindow) && (newPulse->GetTime()<(m_startTime+m_offsetWindow+m_coincidenceWindow)) ,</tt> <tt>when we setup the parameter by the command "/gate/digitizer/Coincidences/setWindow", we should set the value as tau, not two tau.</tt> <tt>When the PET manufacturer provides the specification of "coincidence window", they mean two tau. This is the difference.</tt> <tt> </tt> <table width=100%> <tr valign=top> <td> <td>Fernando Rannou <rannou@diinf.usach.cl> 04/26/2007 11:28 AM <td>                To:        "Chen, Yu" <Yu.Chen@umassmed.edu>         cc:        yuxuan.zhang@di.mdacc.tmc.edu, gate-users@lists.healthgrid.org         Subject:        RE: [Gate-users] question about the coincidence window</table> <tt>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@lists.healthgrid.org on behalf of > yuxuan.zhang@di.mdacc.tmc.edu > Sent: Wed 4/25/2007 6:35 PM > To: gate-users@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</tt> <tt>> 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@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. </tt>