Hi, Thank you both for your answer. I managed to have a good reconstruction with 200° since my cone angle is about 20°. I didn't mention in my original email that I was already using Parker weightings, but as you mentioned I needed higher angles. Thank you for your help. As a more general question, the machine I am using to acquire data can only rotate 180° around the patient but is still able to reconstruct (I don't have access to the projections, it generates a 3d volume as output). Are you aware of any algorithm that would be able to do so?
Clément Le ven. 11 déc. 2020 à 10:03, Simon Rit <[email protected]> a écrit : > Hi Clément, > To complement Gabriele's response and explains what goes on. FDK requires > a 360° acquisition. RTK will calculate the angular gap between the current > projection and the two neighbors. With your configuration, two projections > take an angular weight (the delta when discretising the backprojection > integral) of about 90°. > You can do a short scan with Parker weightings but, as stated by Gabriele, > that necessitates at least 180° + the cone angle. > Simon > > On Fri, Dec 11, 2020 at 9:23 AM <[email protected]> > wrote: > >> Hi Clément, >> >> It seems likely that your geometry is not 180+fan-angle complete and >> therefore cannot lead to a proper reconstruction. From your attached >> geometry, you sweep from 0 to 178° (180-increment). >> >> My suggestion would be to try some intermediate angles, so to recreate a >> complete ShortScan. I suggest you to try at least a 200/220 ° arc to check >> on your simulation pipeline. >> >> I hope this is helpful, >> Gabriele >> >> >> >> *Da:* Rtk-users <[email protected]> *Per conto di *Clément >> Mirabel >> *Inviato:* venerdì 11 dicembre 2020 09:11 >> *A:* [email protected] >> *Oggetto:* [Rtk-users] Trying to reconstruct with a 180 degrees circular >> projection geometry >> >> >> >> Hi, >> >> >> >> I have been trying to set the geometry in >> ThreeDCircularProjectionGeometry with values between 0 and 180 degrees, to >> reproduce the motion of some acquisition systems, but reconstruction is far >> from the expected result when the gantry angle does not reach max value of >> (360-increment). (Attached is the geometry file generated) >> >> My workflow is the following : >> >> - Apply JosephForwardProjectionImageFilter on a 3D Volume >> - Try to reconstruct using FDKConeBeamReconstructionFilter >> >> Although, the result from JosephForwardProjectionImageFilter describes a >> 180 degrees rotation, the output of the reconstruction seems to display >> rays from opposite direction but not from rotated directions >> >> >> >> Here is a view of what is supposed to be an axial slice: >> >> >> >> Thanks for your help! >> >> >> >> Clément >> >> >> _______________________________________________ >> Rtk-users mailing list >> [email protected] >> https://public.kitware.com/mailman/listinfo/rtk-users >> >
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