[Rtk-users] JosephForwardProjectionImageFilter - output intensity problem

[Thibault Pelletier]

Hi Simon,

Adding the FieldOfViewImageFilter and the truncation correction now yields
pretty close values for the forward projection and the original stack.

Thank you very much!
Thibault

On Fri, Aug 13, 2021 at 8:51 AM Thibault Pelletier <
thibault.pelletier at kitware.com> wrote:

> 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
>>> _______________________________________________
>>> Rtk-users mailing list
>>> Rtk-users at public.kitware.com
>>> https://public.kitware.com/mailman/listinfo/rtk-users
>>>
>>
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