[Gate-users] GATE running problem--WARNING : positron found and photonID vector size 1

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

The first two question, Nicolas already has a clear answer and explanation for that.

>From my experience, few warning messages per second is not a big deal as 
long as the simulation goes on
without crash. Usually if  the source is partially not surrounded by any 
phantom, the simulation
will crash in a short while. 

I also have the same problem with voxelized phantom/source such as the 
MOBY phantom. I am
thinking maybe we can suggest the developer of MOBY phantom to put a 
"skin" outside the MOBY,
so we can set the activity in the "skin" as 0.

Anyway even with current version of MOBY phantom, the escaped positrons 
are very small portion of the
total events and should not have any significant effect on your result.

yuxuan







"Su, Yi" <suy at mir.wustl.edu>
01/04/2008 03:59 PM

 
        To:     "'yuxuan.zhang at di.mdacc.tmc.edu'" <yuxuan.zhang at di.mdacc.tmc.edu>
        cc:     "'gate-users at lists.healthgrid.org'" <gate-users at lists.healthgrid.org>
        Subject:        RE: [Gate-users] GATE running problem--WARNING : positron found and 
photonID vector size 1


Thanks a lot for the information. So exactly what triggers the warning 
message, when the positron escapes the 'world' or the phantom volume? 
Would these positrons interact with the detector and messing up the 
simulation? Right now I am seeing a couple of such warning messages per 
second.
Another question is if we are simulating a mouse PET scan using voxelized 
phantom/source, I assume the same volume is phantom and source at the same 
time, would this cause more such warning messages?
 
Thanks again.
 
Yi
 
From: yuxuan.zhang at di.mdacc.tmc.edu [mailto:yuxuan.zhang at di.mdacc.tmc.edu] 
Sent: Friday, January 04, 2008 3:44 PM
To: Su, Yi
Cc: 'gate-users at lists.healthgrid.org'; 
gate-users-bounces at lists.healthgrid.org
Subject: Re: [Gate-users] GATE running problem--WARNING : positron found and 
photonID vector size 1
 

Usually it is because that the size of your phantom is not big enough 
therefore some positron can escape from the phantom without 
annihilation. If there are not a lot of warning messages, (less than a few 
per second) then that's fine. Otherwise you need to 
check your phantom and source definition. The common error is that the 
part of the source is outside the phantom. 

yuxuan 







"Su, Yi" <suy at mir.wustl.edu> 
Sent by: gate-users-bounces at lists.healthgrid.org 
01/04/2008 01:31 PM 
 
        To:        "'gate-users at lists.healthgrid.org'" 
<gate-users at lists.healthgrid.org> 
        cc:         
        Subject:        [Gate-users] GATE running problem--WARNING : 
positron found and photonID vector size 1



Hi there, 
  
I am running a GATE simulation and the following warning message keeps 
popping up: 
  
[GateTrajectoryNavigator::FindAnnihilationGammasTrackID]  WARNING : 
positron found and photonID vector size: 1 
  
Does anyone know what is going on, and what might be the problem? I am 
using Gate 3.1.2 and I am simulating an ecat system with a simple cylinder 
phantom and source. 
  
Thanks a lot, 
  
Yi 
__________________________________________ 
Yi Su, PhD 
Division of Radiological Sciences 
Mallinckrodt Institute of Radiology 
Washington University School of Medicine 
Campus Box 8225 
510 S. Kingshighway Blvd 
St. Louis MO 63110 
Phone: 314-362-8363 
Fax:       314-362-9940 
Email: suy at mir.wustl.edu 
  
 

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