[Rtk-users] JosephForwardProjectionImageFilter - output intensity problem

[Thibault Pelletier]

Hi Simon,

Thank you for your reply.
I will try what you are suggesting and let you know.

Thibault


On Fri, Aug 13, 2021 at 7:59 AM Simon Rit <simon.rit at creatis.insa-lyon.fr>
wrote:

> 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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>
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