[Castor-users] castor-recon -conv Parameters

[Simon Stute]

Hi Reza,

Thanks for your feedback. This is a good question, but with no easy good 
answer!

For an arbitrary PET scanner, I think your suggestion of using the 
crystal width is not too far from the reality (considering no 
depth-of-interaction measurement).

About the images you sent, there clearly are artifacts with 1mm FWHM 
which cannot be seen with 2mm FWHM. They can come from several sources:
  - reconstruction of simulated data without proper normalization 
correction factors (in that case, the use of a PSF may artificially 
reduce such artifacts)
  - a strictly line projector with too small voxels (if you are using 
Siddon for example; in this case try the Joseph projector which makes 
use of interpolations, it can decrease such artifacts)
  - or a combination of the two.

Cheers,
Simon

Le 28/04/2017 à 18:55, M.R Teimoori a écrit :
> Hello CASToR Users,
>
> I've been using CASToR to reconstruct images of various human PET 
> scanners to compare their image quality. So far, through working with 
> CASToR, I learned that the quality of the reconstructed images for any 
> PET scanner significantly varies when changing the image convolver's 
> FWHM.
>
> For example, the attached file shows images of a Derenzo-like phantom 
> obtained from simulations of a brain-dedicated PET scanner and 
> reconstructed with CASToR using listmode EM reconstruction. This 
> arbitrary PET scanner had LSO detectors with a crystal width of 2 x 2 
> mm^2 and a crystal depth of 20 mm. In (A), images were reconstructed 
> using "-conv gaussian,2,2,3::psf" and in (B), the same listmode data 
> were reconstructed using the same reconstruction parameters but with 
> convolution parameters of "-conv gaussian,1,1,3::psf".
>
> How legitimate does this sound to say that "for a PET scanner, the 
> convolver's FWHM should be equal to the scanner's crystal width"? In 
> general, are there any recommendations as to how image convolver's 
> parameters should be chosen for any arbitrary PET scanner?
>
> Thank you for your responses,
>
> Cheers,
> Reza
>
>
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