[Rtk-users] Result from SART is worse than from FDK

[Simon Rit]

Hi Andreas,
Thanks for the report. We know that the implementation of SART is
imperfect, we haven't been working a lot on it... It seems that you
haven't reached convergence. One potential cause is that we use a
heuristic for the sum of the weights (denominator in the SART formula)
instead of the exact sum. The weight is constant and equals the
diagonal of your volume (see line 165 in
rtkSARTConeBeamReconstructionFilter.txx). Maybe this is completely
wrong in your case. Could you try to increase lambda to see if that
helps?
To help us do some tests, I would advise you do reproduce your
geometry with simulations of the Shepp Logan phantom (see
wiki.openrtk.org).
Simon

On Tue, Nov 5, 2013 at 5:11 PM, Staude, Andreas <andreas.staude at bam.de> wrote:
> Hello RTk-users,
>
> I try to use the SART algorithm, but the results are worse than those
> obtained with FDK (see attached images).
>
> The FDK result looks like expected, so I assume that I have the data
> format and the reconstruction geometry set properly. For SART I used the
> same parameters and already tried with different values of lambda and
> niterations.
>
> Does anyone have an idea what went wrong? Is there some kind of
> smoothing or regularisation applied in the SART implementation?
>
> Many thanks in advance!
>
> Cheers,
>
> Andreas
>
>
> --
>
> ===============================================================
> Dr. Andreas Staude
> Fachbereich 8.5 "Mikro-ZfP", Computertomographie
> BAM Bundesanstalt für Materialforschung und -prüfung
> Unter den Eichen 87
> D-12205 Berlin
> Germany
>
> Tel.: ++49 30 8104 4140
> Fax:  ++49 30 8104 1837
> ===============================================================
>
>
>
>
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