[Castor-users] Strange PET Artifacts in CASToR

[Joseph W Feld]

Hi CASToR users and developers,


I'm a new CASToR user trying to reconstruct my simulated PET data with CASToR. My images generally look correct, except some of them have a strange artifact where the image is repeated around the center.


I managed to recreate the issue by generating CASToR files in python to make sure my simulation wasn't the issue. I attached a python script that generates list-mode PET data describing a point source with error similar to what I was getting in my simulation. It randomly offsets the crystal id transaxially and axially. When I set the trans_error and ring_error variables in the script to 0, meaning I'm generating what would happen with a perfect point source in a vacuum, I don't get the artifacts.


I think I'm giving CASToR good data that should just be a point. My guess is that I'm using the wrong options for reconstruction. What can I change to make these artifacts go away?


I'm using this command to reconstruct images:


castor-recon -df generated_coincidences.cdh -dout output_generated_coincidences -it 5:1 -vb 3


I'm using castor v3.0.1 on Ubuntu 18.04.5 and reading my images with ImageJ.


To recreate the bug using minimal data, I removed all corrections. When I was using TOF correction, I would still get this issue. I haven't tried other types of correction.


I attached the python script generating point source data, the castor datafiles it generated with added error that makes the artifact, the castor datafiles it generated with no error that doesn't make artifacts, my resulting images, and the .geom of my scanner.


What could cause these kinds of artifacts? Have other people had this issue?


Thank you,

Joseph Feld

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