[Rtk-users] Reconstruction Artifact

[Simon Rit]

Hi,
Sometimes rotating in the wrong direction gives this kind of artefacts.
It's quite possible that we don't use the same convention as other toolkits
regarding this.
For other questions:
1. Yes, you can use pixel as the unit. Then the image spacing should be 1
obviously and indeed, sdd and sid should be in pixels.
2. I don't fully understand. If your data is the output of a count
detector, then you either rely on RTK to guess the counts without object to
compute the line integral, or your preprocess your projections to pass line
integrals in a float format.
Simon

On Tue, Jun 2, 2020 at 4:51 PM Benjamin W. Maloney <
Benjamin.W.Maloney.TH at dartmouth.edu> wrote:

> Hi all,
>
> Not sure if this is the right group to post to but here's my question:
>
> I have a code that pulls in my own projection images and uses
> the FDKConeBeamReconstructionFilter for reconstruction
>
> The reconstruction I am getting has an artifact where it looks like there
> are two overlapping objects rotated.
> I have used other reconstruction toolboxes (mainly TIGRE in MATLAB) with
> the similar geometry inputs and not had this issue. I suspect the
> difference is in the parts of the geometry that are set by default. My
> question is if anyone has seen this before and what input I should look
> into?
>
> I have a few more questions I may or may not be related:
> 1. I assume that since I set the origin etc of my images in pixel, sid and
> sdd should be in pixels as well?
> 2. Are there restrictions related the scalar values of the projection
> data? My data will be in detector counts rather than linear attenuation
> coefficients, is that okay?
> I have attached an image to show this issue. It is supposed to be a
> rectangular mammography phantom. It is a slice in XZ plane
>
> Thanks for the help!
> Ben
>
>
>
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