[Rtk-users] JosephForwardProjectionImageFilter - output intensity problem

[Simon Rit]

Hi,
I'm not sure but one thing is that after reconstruction, you should mask
out everything which is out of the field of view. This can be done with the
FieldOfViewImageFilter
<http://www.openrtk.org/Doxygen/classrtk_1_1FieldOfViewImageFilter.html> to
which you should pass the reconstructed image as first input, the
ProjectionsStack and the Geometry.
If this is not the issue, I would check that you have reconstructed the
whole field of view, that your projections do not have any truncation issue.
Simon

On Wed, Aug 11, 2021 at 12:55 PM Thibault Pelletier via Rtk-users <
rtk-users at public.kitware.com> wrote:

> Hi everyone,
>
> I'm currently implementing the NMAR algorithm using RTK and I have a
> problem regarding the forward projection step.
>
> To make sure my building blocks are correct, I decided to first read my
> projection stack using the rtk::ProjectionsReader class, do a FDK Cone Beam
> reconstruction and forward project this reconstructed image using the
> rtk::JosephForwardProjectionImageFilter class.
>
> I then compare the images that I have after reading my projection stack
> with the images that I have after my JosephForwardProjectionImageFilter
> pass.
>
> My problem is that the values I obtain are quite different (sinogram of
> the images attached).
> The forward projected images are overall 1.7 times brighter than the
> reader images.
>
> Does anyone have an insight on what I could be doing wrong?
>
> Thanks in advance,
> Thibault
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