<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7651.59"> <TITLE>RE: [Gate-users] question about the coincidence window</TITLE> </HEAD> <BODY>  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 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 </BODY> </HTML>