[Gate-users] [BUG] FFDA - Displaced detector geometry and primary projections

[Gabriele Belotti]

Hello everyone,

I'm posting this to inquire on a possible bug in GATE.
BACKGROUND:
I'm conducting some fixed forced detection simulations, with a voxelized
phantom and a moving gantry described by an RTK .XML geometry file.
The specific condition in my geometry file is that I have source and
detector offsets.
My simulation saves primary as well as attenuation images.
BUG(?):
When inspecting the primary images I have a vertical band of values that is
consistently put to 0. The position of this band is on the same side of the
detector offset (i.e. toward the center of the phantom being projected). At
the same time, the attenuation images have no such issue and represent the
complete projection consistently.

I tried changing phantom and the issue was reproduced in the same way.
While if I changed the RTK geometry to one with no offsets I get correct
primary and attenuation images. I will try to find a culprit with
further tests but I wanted to share this with you.

PS: Issue reproduced in vGATE (GATE 9.1 and GEANT4 10.7) and on a cluster
(with GATE master and GEANT4 11.0)

Gabriele Belotti
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