[Rtk-users] fdk artefact, sourceOffsetY

[Simon Rit]

Hi Mathieu,
Thanks for the observation. The truth is that we haven't tested thoroughly
this kind of geometry because I generally prefer to keep the source in the
central plane... Still, I have looked into the artifact that you pointed
out, which is only visible with a narrow window / level, and found the
cause which was a bug. I think this will fix it:
https://github.com/SimonRit/RTK/commit/b0dd88821b751671d32ef0fa2f1ff2ae85a4083c
Indeed, this only concerns FBP reconstruction, SART and other iterative
algorithms should not be impacted. Let us know if you observe some other
surprising artifacts.
Thanks again,
Simon

On Fri, Feb 6, 2015 at 6:27 PM, Mathieu DUPONT <mdupont at cppm.in2p3.fr>
wrote:

> Hello rtk users,
>
> I try to use RTK for reconstruction in my lab but I encounter some
> problems.
>
> I try to reconstruct a simulated spheroid. I join my phantom text file
> (SheppLogan.txt).
>
> If I set source_y=0, I get a correct (I guess) reconstruction, see the
> joined figure1.png. I use the followind set of commands :
>
> rtksimulatedgeometry -n 180 --sdd=508.1658133423730
> --sid=242.7169928585076  --proj_iso_x=-53.500206362627239
> --proj_iso_y=-10.768620138555379   --source_y=0     -o geometry.xml &&
> rtkprojectgeometricphantom -g geometry.xml -o /tmp/tmpfs/projections.mha
> --spacing 1 --dimension 512 --phantomfile SheppLogan.txt && rtkfdk -v  -p
> /tmp/tmpfs/  -r projections.mha -o /tmp/tmpfs/fdk_ccd.mha -g geometry.xml
> --spacing 0.07 --origin -20,14,-20 --dimension 600,600,600 --hardware="cuda"
>
> But If I set source_y=15, I obtain some strange artefacts as you can see
> on figure2.png. Do you know the origin of this pattern (the vertical one) ?
> Is it normal ? Or my geometry is completely wrong ? If I use  rtksart, this
> artefact doesn't exist.
>
> Thanks in advance and thanks for this nice toolkit.
>
> regards,
> Mathieu Dupont
>
>
>
>
>
>
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