[Gate-users] Positron travel prior to annihilation

[Pieter Mollet]

Dear Martin,

You should use "/gate/source/twogamma/setType backtoback" when defining
a source, this way the range of the positron and the noncollinearity are
ignored. See the manual for more information.
Best Regards,

Pieter Mollet


Op donderdag 21-01-2010 om 15:00 uur [tijdzone +0100], schreef Martin
Schain:
> Dear GATE users,
> 
> I am new to this community and have not really figured out an efficient
> way to search the archives, so I apologize if this matter is already
> discussed.
> 
> We would like to simulate PET data in which the effect of positron
> travel prior to annihilation is absent. It seems from the user manual
> that this effect is hardcoded into geant4 and is therefore not easy to
> alter, but as it would be very convenient for our work I wonder if
> anyone has any experience or knowledge in how to accomplish this. 
> 
> If I recall the physics properly, the range which the positron travels
> before it is annihilated depends on the energy it receives in the decay.
> If it is possible to design a ligand which decays into positrons with
> 511 keV, causing immediate annihilation of the positrons and therefore
> forcing their travelled distance to 0, then that could be an artificial
> way to circumvent the problem. Is it possible to design such a ligand?
> However it is of course preferred if the effect could simply be turned off.
>  
> I am grateful for all hints, suggestion or ideas in this matter. 
> Best Regards
> Martin Schain 
> 
> 
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