[Gate-users] Three problems with Gate 6.1

[Nikolaos A. Karakatsanis]

Dear Min-Jae,

thank you for reporting this potential problem in GATE.

I personally had come up with this suspicious behavior in the past too. 
After conducting a validation study using different materials and sizes 
for the source and the attenuating medium, I concluded that the problem 
is related with the set-up of source-medium employed to access positron 
range.

The distance corresponding to the local minimum observed between the two 
peaks of the positron range is strongly related with the distance of the 
outer boundary of the source from the center of the source. In other 
words, the local minimum is observed almost exactly at the interface 
between the source and the surrounding attenuating material.

I would suggest you not to use different materials for the source and 
the attenuating volume. You can use water for both volumes, which is a 
very realistic set-up to access positron range.

However, even if the problem is eliminated, the behavior you report is 
suspicious and probably we need to go through the implementation of the 
physical processes in GATE and Geant4.

To assist us, please attach the positron range spectrum after using GATE 
6.1 and GATE 5 and kindly provide us with a description of the materials 
and the geometry of source and attenuating medium that you have been using

thank you.
Nicolas

____________________________________________________
Nikolaos A. Karakatsanis, PhD
Division of Nuclear Medicine
Department of Radiology
Johns Hopkins Medical Institutions
Room 3263, JHOC Bldg
601 N. Caroline Street
Baltimore, MD, USA, 21287


On 7/6/11 5:52 PM, MinJae Park wrote:
> Dear Gaters,
>
> Recently, I installed Gate 6.1 to investigate the positron range of Rb-82.
>
> But, I can't use different physical model using "setModel" command.
> I got an error as below when I tried to use setModel.
> [G4-cerr] ***** COMMAND NOT FOUND
> </gate/physics/processes/ElectronIonisation/setModel PenelopeModel e+>
> *****
>
>
> In addition, since the positron range was deactivated by default,
> I modified the source code to get the positron range.
>
> However, even though ion source (37 82 0 0) was used,
> the positron range was little bit different from Gate 5.0 and
> also from the reference paper (Levin, Calculation of positron
> range..., PMB, 1999).
>
> I guess this might be a problem with physical model at low energy.
>
>
> One more, I can't use parameterization on batch mode.
> For example, "Gate -a nZ 37 -a nA 82<  sim.mac".
> "Gate -a nZ 37 -a nA 82 sim.mac" is working, though.
>
>
> Thank you,
> MJ
>
> //=================================================
> //  MinJae Park, Ph.D.
> //
> //  Johns Hopkins University
> //  School of Medicine, Dept of Radiology
> //  Division of Medical Imaging Physics
> //
> //  DialTo:+1-443-287-2005 (Office)
> //  MailTo:MJ at ToTi.us, MJ at JHMI.edu
> //
> //  "You see, But you do not Observe"  - Sherlock Holmes -
> //=================================================
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