SPECT reconstruction with non-constant distance camera surface to COR

Dear Castor Developers and users,

I hope this email finds you well. I am trying to reconstruct SPECT imaging acquired by the Siemens Symbia gamma camera. In the SPECT acquisition, the distance between camera head and centre of rotation was not constant for all projection angles. In castor input file, I provided this information using “Distance camera surface to COR” as described in the Castor Manual. The result was unexpected (visible misplacement of activity is visible; see arrow in the attached image for NEMA phantom with 5 hot spheres).

I tried to reconstruct again the data with a constant camera distance using “Global distance camera surface to COR” with the value equal to the distance of the first projection angle and the results were identical with the above mentioned reconstruction. So, I assume the way that I provide camera to COR distance is not appropriate. I am wondering if someone could help me to resolve this issue.


· CASToR_synopsis.txt → running synopsis

· NEMA_tomo.cdh → Header of input acquisition data with camera provided head and COR distance

· NEMA_tomo_constantCOR.cdh → Header of input acquisition data with constant head and COR distance

· Screenshot_recons.png → screenshot of recons (first row: recon of NEMA_tomo.cdh/ second row: recon of NEMA_tomo_constantCOR.cdh / third row: difference between first two recons)

kind regards,

Esmaeel Jafargholi Rangraz

CASToR_synopsis.txt (776 Bytes)

NEMA_tomo.cdh (2.18 KB)

NEMA_tomo_constantCOR.cdh (488 Bytes)


Could you send the log file for each recon, this would probably help.

In the header files, the duration is set to 1s.

This would mean that if you have some projections with a time flag later than 1 second, they will be ignore in both cases. Could it be the problem ?