[Rtk-users] Problem reconstructing from synthetic data

[Simon Rit]

Yes, the origin is the center of the first pixel in ITK see e.g. figure 4.1
of ITK's software guide
<https://itk.org/ITKSoftwareGuide/html/Book1/ITKSoftwareGuide-Book1ch4.html#x45-54001r1>
.
Simon

On Mon, Jun 26, 2023 at 11:03 AM Albert MURIENNE <Albert.MURIENNE at b-com.com>
wrote:

> Hello Simon,
>
>
>
> Glad to hear you’re still actively maintaining RTK J
>
> I made some tests following your advices, and everything is now working
> fine!
>
> I had already started playing with the projections origin, but I was
> missing the point about the rotation convention.
>
> I guess the xxx.75 origin coordinates are related to the origin being at
> the “center” of the pixel?
>
>
>
> Regards,
>
>
>
> Albert
>
>
>
> *De :* Simon Rit [mailto:simon.rit at creatis.insa-lyon.fr]
> *Envoyé :* jeudi 22 juin 2023 11:47
> *À :* Albert MURIENNE <Albert.MURIENNE at b-com.com>
> *Cc :* rtk-users at openrtk.org
> *Objet :* Re: [Rtk-users] Problem reconstructing from synthetic data
>
>
>
> Hi Albert,
>
> Nice to hear that you are still working on CT. There are two things that
> must be accounted for
>
> - there is a difference in convention for the rotation angle between
> gVirtualXRay and RTK,
>
> - the projections are not centered if the origin is 0.
>
> The following command lines work for me:
>
> rtksimulatedgeometry -n 360 -a -360 -o g  --sdd 1000 --sid 500
> rtkfdk -p . -r 'projection([0-9]*).tif' -o fdk.mha --neworigin
> -159.75,-119.75,0 --newspacing 0.5 --nsort --submatch 1 --hardware cuda -g g
>
> Let me know if something is unclear,
>
> Simon
>
>
>
> On Wed, Jun 21, 2023 at 10:04 AM Albert MURIENNE <
> Albert.MURIENNE at b-com.com> wrote:
>
> Hello,
>
> I'm struggling to reconstruct properly a synthetic projection images
> sequence using RTK.
> The sequence was generated using gVirtualXRay (
> https://gvirtualxray.fpvidal.net/) and a dragon 3D model, and represents
> a full 360 degrees CBCT tomographic sequence, with a 500mm SID and 1000mm
> SDD, 0.5mm pixel size with a 640x480 image resolution, and without any
> offsets (perfect circular geometry). I tried reconstructions with the
> simplest FDK and SART implementations, inspired by RTK provided code
> examples, using rtk::ProjectionsReader to read the images and
> rtk::ThreeDCircularProjectionGeometry to read the geometry, but the results
> are not good, and I don't really know if the problem comes from the data or
> from my reconstruction implementation.
>
> The images data, as well as the xml geometry I generated, are available
> for download at this link:
>
>
> https://filesender.renater.fr/?s=download&token=bc8f87b4-989c-46d7-8c4b-dac39a4df0e1
>
> Could you help me pinpoint the origin of my problem? Does it come from the
> data itself?
>
> Thanks,
>
> Albert
> Murienne
>
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