[Rtk-users] Reconstruction geometry

[Christian Riesch]

Hello Simon,

Thanks for the quick response.
So I have tried rtksimulatedgeometry with --arc 273 together with adding --neworigin=-153.5985,-153.2025,0 to rtkfdk.
The result is different than before, but still looks very wrong (two ribbons and some vertical lines).

I may be able to share some data later.

Best regards,
Christian

________________________________
Von: Simon Rit <simon.rit at creatis.insa-lyon.fr>
Gesendet: Donnerstag, 30. Mai 2024 08:48
An: Christian Riesch <christian.riesch at live.com>
Cc: rtk-users at openrtk.org <rtk-users at openrtk.org>
Betreff: Re: [Rtk-users] Reconstruction geometry

Hi,
I can see two problems:
- you need to indicate the short scan to rtksimulatedgeometry, e.g. --arc 273 or, if the angle convention is opposite in your system, --arc -273. You may have to tune the --first_angle option to position the volume as you wish but that should not prevent accurate reconstruction.
- you need to center your projections, i.e., add the option --neworigin=-153.5985,-153.2025,0 to rtkfdk, computed with -0.5*(3104-1)*0.099 and -0.5*(3096-1)*0.099.
Don't hesitate to share a dataset if that does not help.
Good luck!
Simon


On Thu, May 30, 2024 at 6:58 AM Christian Riesch <christian.riesch at live.com<mailto:christian.riesch at live.com>> wrote:

Hello,



I'm currently trying to use RTK for a reconstruction from a stack of images that resulted from a 90° scan, but struggling to get the parameters right.

On the other hand, I was able to get what looks like a faithful reconstruction using the Astra toolbox and the script from https://tomroelandts.com/articles/astra-toolbox-tutorial-reconstruction-from-projection-images-part-1



I have these parameters from the X-ray device that captured the images (size 3104x3096):

            "fod_mm": 75.46, (focus to object distance)

            "odd_mm": 407.07, (object to detector distance)

            "pixel_size_mm": 0.099,

            "start_arc_deg": 45.0,

            "stop_arc_deg": -45.0

(There is also "detector_offset_mm": 9.8, which I have ignored so far with both Astra and RTK.)



So I have tried to create a geometry using

.\rtksimulatedgeometry.exe -o"geo.xml" -n91 -f45 -a90 --sdd=482.53 --sid=75.46

where sdd = fod_mm + odd_mm and sid = fod_mm,

and a reconstruction with

.\rtkfdk.exe -p"images" -r".*tif" -g"geo.xml" -o"out.tif" --dimension=512,512,200 --newspacing=0.099



However, out.tif contains mostly zeros and a weird ribbon-like shape in the center. So I think my geometry is wrong, but I don't know how to fix it.



For comparison, here are the input parameters for the Astra script:

distance_source_origin = 75.46  # [mm]

distance_origin_detector = 407.07  # [mm]

detector_pixel_size = 0.099 # [mm]

num_projections = 91

start_angle_deg = 45

stop_angle_deg = 135



Any pointers would be appreciated.



Best regards,

Christian Riesch



_______________________________________________
Rtk-users mailing list
rtk-users at openrtk.org<mailto:rtk-users at openrtk.org>
https://www.creatis.insa-lyon.fr/mailman/listinfo/rtk-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.creatis.insa-lyon.fr/pipermail/rtk-users/attachments/20240531/4e665f01/attachment.htm>