<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> Dear JinSu regarding your first question this is a warning message generated by GATE in the following cases a) a positron was generated but no annihilation gamma photons were produced. If your geometry around your source was not dense enough to ensure annihilation of some emitted positrons then it is very likely that this warning message will appear during GATE simulation. This warning is repeated every time a trajectory with this properties is processed by GATE trajectory navigator. b) a positron was generated and then either 1 or more than 2 annihilation gammas were produced. In most cases you would expect to have two annihilation gammas. So this is unlikely to happen. In your case one gamma photon was generated after the positron. This is strange for GATE trajectory navigator and we might need to investigate it further. Please can you give us more details on this. For example, was this warning message produced many times? What kind of source have you used? What was the geometry of your phantoms? If you repeat the simulation with a thicker surrounding attenuation volume, will you still get these warnings? As far as the second question is concerned the GATE developers community has been investigating the methods used by GATE to calculate positron range recently because we observed some strange results regarding the positron annihilation distance. It is likely to have discrepancies between literature and GATE. However we would like you to tell us how did you estimate the positron range you mention. Is this question related to the same simulation that generated the previous warning message?If not, then what kind of source have you used and what was it's shape and dimensions. Moreover it will be helpful if you can tell us a little more about the properties (shape, dimensions) of the water volume that surrounded your source. Nicolas Nicolas Karakatsanis PhD Candidate School of Electrical and Computer Engineer National Technical University of Athens   JinSu Kim wrote: <blockquote cite="mid:001601c82db3$281af3b0$3f8311ac@LocalHost" type="cite"> <meta http-equiv="Content-Type" content="text/html; "> <meta name="Generator" content="Microsoft Word 11 (filtered medium)"> <style>  </style>  <div class="Section1" style=""> Dear Gate users<o:p></o:p> <o:p> </o:p> 1st question is ..<o:p></o:p> During gate simulation, I found following error message<o:p></o:p> Is it negligible?<o:p></o:p> [GateTrajectoryNavigator::FindAnnihilationGammasTrackID]  WARNING : positron found and photonID vector size: 1<o:p></o:p> <o:p> </o:p> 2nd question is about the Positron range of F-18<o:p></o:p> In the literature, positron range of F-18 was 0.2 mm at water<o:p></o:p> However, I found that the positron range of F-18 was 0.43 mm at water in GATE simulation.<o:p></o:p> What is the difference of that?<o:p></o:p> <o:p> </o:p> Best regards<o:p></o:p> <o:p> </o:p> <o:p> </o:p> <o:p> </o:p> <div>  <o:p></o:p> </div> <o:p> </o:p> </div> __________ NOD32 2680 (20071123) Information __________ This message was checked by NOD32 antivirus system. <a moz-do-not-send="true" href="http://www.eset.com">http://www.eset.com</a> <pre wrap=""> <hr size="4" width="90%"> _______________________________________________ Gate-users mailing list <a class="moz-txt-link-abbreviated" href="mailto:Gate-users@lists.healthgrid.org">Gate-users@lists.healthgrid.org</a> <a class="moz-txt-link-freetext" href="http://lists.healthgrid.org/mailman/listinfo/gate-users">http://lists.healthgrid.org/mailman/listinfo/gate-users</a> __________ NOD32 2680 (20071123) Information __________ This message was checked by NOD32 antivirus system. <a class="moz-txt-link-freetext" href="http://www.eset.com">http://www.eset.com</a> </pre> </blockquote> </body> </html>