[Gate-users] How to use eccentric orbits ?

[Henri Der Sarkissian]

Hello dear Gate-Users,

I have a problem concerning the eccentric orbit for SPECT systems. I am 
reading the user's guide but I don't really understand what the 
"shiftXYZ" parameter means...
Is it the "linear eccentricity" (c) between the focus and the center of 
the ellipse ?
How may I use it if I have the value of the semi-major axis (X) and the 
semi-minor axis (Y), considering the phantom is centered on the origin ?

Thanks a lot,

Henri Der Sarkissian