[Gate-users] Understanding the (x, y, z) location reported in the Hits data

[Andre Kyme]

Hi all,

I've been trying to understand the ROOT hits output by comparing it with the TEXT output from my PET simulations.

What I'm confused by is that the (x,y,z) location recorded in the ROOT hits output always corresponds to the step in the TEXT output that is immediately before the interaction itself. I've attached a portion of the TEXT output for one recorded coincidence event to show what I mean. Here, for each interaction (Compton, Photoelectric etc) in a sensitive detector element, the values appearing in the ROOT hits data are highlighted the same colour. Can anyone explain why the ROOT hits entry doesn't specify the (x,y,z) for the actual step where the interaction is listed and instead uses the preceding step?


(Note  that the TEXT output has many more entries than the ROOT hits output because it records all steps for all photons and secondaries, regardless of whether they interact in the sensitive detector. The ROOT hits output on the other hand only records steps for interactions involving sensitive detector elements.)


Thanks,

Andre

________________________________
Andre Kyme, PhD
Department of Biomedical Engineering
University of California, Davis
T: +1 (530) 302 6800
E: akyme at ucdavis.edu<mailto:msjudenhofer at ucdavis.edu>
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