When CASToR computes the sensitivity image from only the system geometry i.e, the default behavior (no normalization or attenuation correction is provided to CASToR), which geometric corrections are accounted for? Specifically, I would like to know if CASToR accounts for the solid angle effect during this process. I have briefly looked into the source code and if I am not wrong, I did not find anything that the computation of sensitivity handles the solid angle effect. Based on what I have seen in this forum, the documentation, and the source code, it considers only the optimal detector efficiency, “min angle difference”, and “Maximum axial difference mm” and computes the sensitivity.
Could you please let me know if CASToR corrects for the solid angle effect during the default behavior of the sensitivity calculation?
For default list-mode PET reconstruction, CASToR will load your geometry and loop over the lines of response form by any pairing of detectors of your system of the geometry to generate the sensitivity image. This process takes into account the solid angle of your system.
Picking a standard system you could disable normalization and attenuation and have a look at the generated sensitivity image, for instance the one from the PET benchmark:
The variables “min angle difference” and “maximum axial difference mm” just add a bit of control over the lines of response which will be taken into account, with restrictions over transaxial angles et axial distance respectively between detectors, to match the generated sensitivity image with data acquired with specific geometrical conditions. However they don’t provide as much agency as a normalization datafile which directly specifies every data channels available in the system.
