[Gate-users] gate users question

[Natacha Ruiz]

Hi,
I was studying the distribution of the positron annihilation position for
the F-18, O-15, etc radionuclides. I noticed that the annihilation
distribution is strange and doesn't fit with the theoretical curves (see
joined schemesfor the two cases). In fact, for a point source, the
theoretical curves decrease from a maximum at position 0 contrary to the
simulated data, we can see in the root file (Positron_annihil_distance_mm )
that we have 2 curves.  This problem has been reported before? Does somebody
have an idea about the origin of this distribution?

Another question, if we define the F-18 as an ion (for e.g.
/Gate/source/nameSource/particle ion ; /Gate/source/nameSource/gps/ion 9 18
0 0) , do we model the acolinearity? because in the root file
Acolinea_Angle_Distribution_deg we see nothing.

I have also a question to the GATE developers : How did you define the
position emission distribution (for e.g. Fit =
CLHEP::RandExponential::shoot(0.7) ) ?  0.7 is found empirically or how?

Thank you

Natacha Ruiz
Service de médecine nucléaire, Hôpital Tenon
4, rue de la Chine, 75970, Paris cedex 20
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