[Rtk-users] rtkadmmwavelets ring artifact

[Simon Rit]

Hi,
It looks very much like a displaced detector artefact (the Cho
<http://www.sciencedirect.com/science/article/pii/0895611196000316>
situation). If I refer to the doc of ADMM wavelets
<http://www.openrtk.org/Doxygen/classrtk_1_1ADMMWaveletsConeBeamReconstructionFilter.html>
and TV
<http://www.openrtk.org/Doxygen/classrtk_1_1ADMMTotalVariationConeBeamReconstructionFilter.html>,
you have these nice graphs that document the pipelines used for the
computation and indeed, the displaced detector situation is accounted for
in TV but not in wavelets. Maybe you can try to dig in the code and correct
that in ADMM wavelets? Otherwise, I'll ask Cyril if he agrees to do it next
week.
Simon

On Mon, Mar 16, 2015 at 11:00 PM, Joel Beaudry <joelbeaudry at gmail.com>
wrote:

> Sure thing, thanks for the reply Simon. I've attached a Coronal and Axial
> slice showing the ring. I'll wait for Cyril's reply.
>
> The image quality is pretty poor but I'm using ~70 projections (4DCBCT),
> so that's expected. Admittedly, I'm not using a high
> number of iterations (n=10) but I suspect this ring artifact is from
> something else. This does not occur when using rtkadmmtotalvariation, but
> only the admmwavelets.
>
> And just a general question regarding the nature of iterative
> reconstructions. I'm currently using no input image, so I assume the
> initial guess is just some uniform value but is it beneficial to first do a
> full (so use all projections) FDK reconstruction and use that as the input
> instead?
>
> Thanks,
> Joel
>
> On Mon, Mar 16, 2015 at 1:27 AM, Simon Rit <simon.rit at creatis.insa-lyon.fr
> > wrote:
>
>> Hi,
>> Could you provide a snapshot?
>> Cyril, the developer of this method, is away for a few days but he'll
>> be able to answer next weeks.
>> Cheers,
>> Simon
>>
>> On Fri, Mar 13, 2015 at 7:49 PM, Joel Beaudry <joelbeaudry at gmail.com>
>> wrote:
>> > Hi RTK users/developers,
>> >
>> > I've been using RTK for CBCT reconstructions and found it to be very
>> useful,
>> > so thanks for all the work done on it!
>> >
>> > As for my question,when I use rtkadmmwavelets I get a ring artifact in
>> the
>> > center of the image. I'm using it for 4DCBCT reconstructions, so I'm not
>> > using the full number of projections and not sure if this is a
>> contributing
>> > factor. From reading previous posts I know that the entire object must
>> be in
>> > the reconstruction, and so I have included both the patient and couch
>> in the
>> > reconstruction volume but still get the ring artifact. Has anyone else
>> > encountered this? Any ideas/suggestions?
>> >
>> > Cheers,
>> > Joel
>> >
>> > PS. When trying rtkadmmtotalvariation I don't encounter such issues.
>> >
>> > _______________________________________________
>> > Rtk-users mailing list
>> > Rtk-users at public.kitware.com
>> > http://public.kitware.com/mailman/listinfo/rtk-users
>> >
>>
>
>
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