[Castor-users] GATE ecat reconsstruction

[STUTE Simon]

Hi,

Yes likely multiple problems.

You should provide details about your detector in order to be able to understand the choice of some parameters.

Why 64 itérations with 128 subsets ?! A rule of thumb without TOF would be to have a maximum number of subsets equal to the number of crystals in a ring divided by 16 to 20. Then, without any post-smoothing or regularization, aim for a maximum of 50 to 100 updates (i.e. iterations x subsets). For your first reconstructions, consider including a post-smoothing.

Voxels of 1mm^3 ? Is you scanner for small animals ? Otherwise, for a first reconstruction, aim for voxels with their side equal to the crystal width.

Finally, in a second step, you should consider including a normalization correction. There are already many discussions about that in the forum.

For your first reconstructions with Gate simulated data, I would also recommend to include only true coincidences.

Best
Simon


Le 12 avr. 2024 21:02, Dimitrios Thanasas <dthanas at uoa.gr> a écrit :
Dear CASTOR-users,

I simulate a simple PET ECAT system using GATE (V8.2 - I couldn't install
CASTOR on version 9 or later).
I simulated an orthogonal parallelepiped source (xlength:5 mm, ylength:1
mm, zlength:10 mm).
According to the guidelines, I have used castor-GATEMacToGeom to generate
the geom file and castor-GATERootToCastor to create the Cdh and Cdf files.
Then I ran the command
castor-recon -df ecat_df.Cdh -opti MLEM -it 64:128 -dim 64.,64.,64. -vox
1.,1.,1. -dout myimages1
after the termination of the reconstruction I get the attached image.

I see something like circles in transverse1 plane instead of a orthogonal
plane as I am expected. In coronal1 and sagital1 planes look like a slice
to appear as I am expected but I think the images have few points. My GATE
output root file includes 862000 coincidences.
Is there something wrong with the reconstruction?

Any help will be appreciated,
Best regards,
Dimitris

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