Alright, I will give it a try. Thank you for your guidance! Le ven. 11 déc. 2020 à 11:44, Simon Rit <simon....@creatis.insa-lyon.fr> a écrit :
> 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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