[Castor-users] Random factor query

tmerlin Thibaut.Merlin at univ-brest.fr
Wed Jul 5 21:02:04 CEST 2017


Dear Alberto Sanchez,

The random correction factors are expected to be rates (count/s). They 
are normalized during the reconstruction by the frame/acquisition 
duration in seconds (if provided), and added to the forward projection 
value alongside scatter correction factors.

Thank you for the bug report, we are currently working on a patch. As 
Niccolo previously mentioned, the corrected version (attached file) 
should work fine.

Best regards,
Thibaut


On 04/07/2017 12:05, Alberto Sánchez-Pastor Gomis wrote:
> Dear all,
>
> I would like to apologize for not being able to figure this out but, 
> how do the random corrections work in CASToR?
>
> I've seen that there is the option of providing a file containing the 
> "randoms correction factors" and that the PET data formats can include 
> the random intensity rates but is this based around the calculation 
> from the singles' rates or is this applicable to the delayed window 
> method? And what do "randoms correction factors" represent? Is it the 
> fraction of counts in an LOR that you expect to be random counts?
>
> Additionally I would like to mention that I believe that there is a 
> bug in the sensitivity calculation when using the "min angle 
> difference" other than 0. I was attempting to implement a scanner 
> using 8 rectors and a min angle difference of 90 but it just meant 
> that the sensitivity dropped in an angular section of 90 deg of the 
> FOV leaving it asymmetrical.
>
> Regards,
> Alberto Sanchez
>
>
>
>
> _______________________________________________
> Castor-users mailing list
> Castor-users at lists.castor-project.org
> http://lists.castor-project.org/listinfo/castor-users

-- 
Thibaut MERLIN -- PhD

Docteur en Imagerie Médicale au Laboratoire de Traitement de l'Information Medicale (LaTIM - INSERM UMR 1101)
Bâtiment 1
CHRU Morvan - 2, Av. Foch
29609 Brest CEDEX - FRANCE
Tel: 06.75.12.24.90

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