[Gate-users] Projection data contain zero counts for confined source

[Steven Marsh]

Hi All - Perhaps you can help me yet again


I am trying to simulate the collection of projection data for activity within the heart.

I have successfully made a two-head SPECT system based on the gate example and for a point source or other simple geometry (cylinder) I can record projection data on each camera. I have also successfully imported STL data for the heart and I can confine a larger volume on to this anatomy to replicate the heart volume which will define the shape of the activity source.

Independently I have managed the above two tasks, however when I try to combine the two, the projection data (interfile output) contain zero counts.  My tests are suggesting that my code breaks down as soon as I try to confine the activity - a cylinder of activity works but a confined cylinder of activity seems to produce photons originating from the cylinder that do not register on either of the two gamma camera heads.

Does this scenario seem familiar to anybody?

Any help much appreciated - happy to supply code if that helps of course
Steve

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