Hi Christian, Thanks for the share. It was not clear to me that you had a 90° scan sorry. FDK is not appropriate for such a 90° scan, it's meant for a full 360° scan. rtkfdk tries to apply a short scan but Parker weighting is for 180°+fan-angle. So I'm not sure what to expect from FDK with such a scan. The projections that you shared are 512x511, can you please clarify the pixel size? I would try iterative reconstruction with such a scan. Cheers, Simon
On Fri, May 31, 2024 at 12:25 PM Christian Riesch <christian.rie...@live.com> wrote: > 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....@creatis.insa-lyon.fr> > *Gesendet:* Donnerstag, 30. Mai 2024 08:48 > *An:* Christian Riesch <christian.rie...@live.com> > *Cc:* rtk-us...@openrtk.org <rtk-us...@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.rie...@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-us...@openrtk.org > https://www.creatis.insa-lyon.fr/mailman/listinfo/rtk-users > >
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