[gate-users] about the acolinearity of two gamma photons

yuxuan.zhang at di.mdacc.tmc.edu yuxuan.zhang at di.mdacc.tmc.edu
Fri Jun 3 23:48:52 CEST 2005

Dear Gate User,

I have some questions about the acolinearity of the two 511 keV gamma
photons in Gate simulation. According to GATE manual and the output
of root file, if a positron source was used, the acolinearity is taken
into account in the calculation. Then my questions are:
 1. If a backtoback gamma source is used, is the acolinearity be 
 2. If a isotope source is used, (F18, O15, etc), is the acolinearity be 

As for the second question, in the 3.2 part of the paper "GATE:a 
simulation toolkit for
PET and SPECT" (Phys. Med. Biol. 49, 2004), it is said "The second modules 
deals with the
acollinearity of the two annihilation photons, which is not accounted for 
in Geant4...",
but in the Physics Reference Manual of Geant4, the acolinearity should be 
calculated in

Anyone can give some explainations about that? Thanks.

Yuxuan ZHANG 
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