OSEM reconstruction for SPECT using SIMIND

Usage Questions
1

Hello, everyone.
I have a trouble, about OSEM reconstruction.
I was doing OSEM with pytomography, but the image after reconstruction dose not work. I was using a cylindrical homogeneous phantom with a diameter of 18cm, but the image is smaller when reconstructed.
I also do scatter correction and attenuation correction using CT images.

What are the possible causes of this and what is the solution?
Please help me.

SIMIND_image_bold
Projection image

Rec_image_bold
Reconstruction image

2

@Haruki which version of SIMIND are you using? There’s an issue in SIMIND v8.0 (where collimator dimensions are now expressed in mm instead of cm) that messes with PyTomography

3

Dear Luke.

Thank you for your reaction.
This was exactly the problem And I was able to resolve it.

One question: what do the units mean after reconstruction?
Is it [counts/MBq/sec] as in projection data?