[Rtk-users] Reconstruction geometry

[Christian Riesch]

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

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