You can check https://doi.org/10.1088/0031-9155/47/14/311 which is not implemented in RTK (yet). But only one half of the field-of-view can be reconstructed exactly if you rate 180°. For the rest, there will be missing data. With RTK, iterative reconstruction should achieve a decent result but will necessarily be limited by the missing data. I recommend the conjugate gradient algorithm which will require adjusting the regularization parameter Gamma and the number of iterations.
On Fri, Dec 11, 2020 at 11:26 AM Clément Mirabel <clement.mira...@gmail.com> wrote: > 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 <simon....@creatis.insa-lyon.fr> > 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 <gabriele.belotti.berg...@gmail.com> >> 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 <rtk-users-boun...@public.kitware.com> *Per conto di >>> *Clément >>> Mirabel >>> *Inviato:* venerdì 11 dicembre 2020 09:11 >>> *A:* rtk-users@public.kitware.com >>> *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 >>> Rtk-users@public.kitware.com >>> https://public.kitware.com/mailman/listinfo/rtk-users >>> >>
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