Dear CASToR users,
I am using CASToR to reconstruct simulated SPECT images using GATE.
However, whenever I try to convert the ROOT files using the “castor-GATERootToCastor” function, the following error message is issued:
**** castor-GATERootToCastor :: Error : Axial and transaxial bins values expected (use option -sp_bins)
After reading the CASToR documentation, I still don’t understand how or where I can get the information regarding the number of bins or projections to perform the image reconstruction. Is it related to acquisition specifics on the GATE macro files?
Thank you in advance for your help.
Best regards,
Adriana
Hi Adriana,
This is related to the detector discretization. CASToR uses discrete detector for the generation of the geometry (the datafile contains the index of a detector. During reconstruction it is associated to a XYZ position using the geometry information).
The sp_bins command purpose is to generate a matrix of “virtual” detectors if your macro does not define explicit discretization (pixels). The detected singles in your file will be associated to a detector depending on their position, so you should provide to -sp_bins a matrix of virtual detector/pixels (ideally matching the collimator geometry).
Hope this helps,
Thibaut
Hello Thibault,
Thank you very much for your reply. Theoretically, I understand the purpose of the sp_bins function, the detected gamma ray events from the SPECT data file need to be associated with specific detector elements or pixels during the reconstruction.
But in a more practical approach, I am not sure how to determine a reasonable number for the pixel matrix or how to match it with the collimator geometry I have previously defined in the GATE macro.
I am sorry for the persistence, but I would really appreciate some guidance in this.
Kind regards,
Adriana