[Gate-users] Re: [Gate-devel] full decay scheme vs pure emission

Nicolas Karakatsanis knicolas at mail.ntua.gr
Tue Jan 22 08:15:11 CET 2008

Dear Irene and Colleagues,

as far as the second question is concerned I have to say that based on a 
GATE performance study I carried out in the past using
- GATE version 2.2
- a single CPU system of 3.2 GHz and 1GB of RAM,
- F-18 isotope modeled as a positron or gamma back-to-back source 
(distributed activity map inside the Zubal phantom) inside a clinical 
PET system (GATE model of HR+)
- a Zubal high-resolution brain phantom (256x256x128 voxels) of 10 
materials (attenuation map of the Zubal phantom), surrounding the 
previously mentioned activity map
- a total activity of 10.2MBq inside the FOV

I came to the conclusion that when we replaced the F-18 positron source 
with a gamma back-to-back source we achieved a gain factor of 1.25 or 
speed up the simulation by 20%.

Moreover back-to-back gamma source gives one the option to limit the max 
emission solid angle that the emitted gammas are allowed to have. This 
can result to higher gain factors (2.5 or 4.5 times) depending on how 
narrow is the range of the allowed emission solid angles defined.

Best regards

PhD Candidate
Nicolas Karakatsanis
Biomedical Simulations and Imaging Technologies Lab
School of Electrical and Computer Engineer
National Technical University of Athens, Greece

Irène Buvat wrote:
> Dear Colleagues,
> Has anybody already tested the difference in computation time 
> depending on whether one simulates the full decay of a gamma emitter 
> or only the single emission energies (for instance for In111, or I123) ?
> Similarly, has anybody already characterized the gain in computation 
> time between positron emission and back-to-back photon emission?
> Thanks for any input you might have.
> All my best,
> Irene

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