Hi,
yes, it is indeed an interior- / region of interest problem in the sense that we only are interested in the fully illuminated centre region. I have previously had success in getting good reconstructions from interior data using variational formulation with tailored penalty term. However, this is implemented in Matlab and the aim is to use your implementation to get a C++ implementation of this method. But for now, I am just figuring how to do a simple reconstruction to get a grasp on the library. Best regards, Jacob ________________________________ Fra: simon....@gmail.com <simon....@gmail.com> på vegne af Simon Rit <simon....@creatis.insa-lyon.fr> Sendt: 16. maj 2017 16:59:12 Til: Jacob Frøsig Cc: rtk-us...@openrtk.org Emne: Re: [Rtk-users] Reconstructing from fan-beam projections Hi, If this is true, then the sinogram indicates that you are dealing with an interior problem since you have high line integrals at the border (see enclosed profile). Is that indeed the case? If yes, that's a difficult problem... Simon On Tue, May 16, 2017 at 3:16 PM, Jacob Frøsig <j...@force.dk<mailto:j...@force.dk>> wrote: Hi, The attached sinogram consist of line integral values, i.e., sinogram(i,j) = -ln[ I(i,j)/I_0(i) ] where I and I_0 are the measured intensities with and without an object, respectively. Since we are measuring with a line detector, the “zero” (I_0) is in this case just an array. j is the index for the projections, i.e., j ∈ {1,2,…,360} since we take one projection for each whole angle. I hope this explains the sinogram and again; thank you for your time! Best regards, Jacob From: simon....@gmail.com<mailto:simon....@gmail.com> [mailto:simon....@gmail.com<mailto:simon....@gmail.com>] On Behalf Of Simon Rit Sent: 16. maj 2017 14:54 To: Jacob Frøsig <j...@force.dk<mailto:j...@force.dk>> Cc: rtk-us...@openrtk.org<mailto:rtk-us...@openrtk.org> Subject: Re: [Rtk-users] Reconstructing from fan-beam projections Hi Jacob, Thanks for the image of the sinogram. I don't understand this sinogram. Do you know how to convert each pixel value to a line integral? I.e., if it's x-ray imaging, do you have an image without object? Thanks, Simon On Tue, May 16, 2017 at 2:24 PM, Jacob Frøsig <j...@force.dk<mailto:j...@force.dk>> wrote: Hi again, and thank you for the example! I have some trouble getting a proper reconstruction. If you have the time, any help would be appreciated. Attached is my fan-beam sinogram as a .tif file. Here, projections are taken for 360 degrees and the detector has 507 pixels. I believe the issue lies in setting the geometry and maybe the spacing between the pixels. The measurement geometry is as follows Source to centre: 590 mm Source to detector: 1000 mm Detector length: 411mm Best regards, Jacob From: Rtk-users [mailto:rtk-users-boun...@public.kitware.com<mailto:rtk-users-boun...@public.kitware.com>] On Behalf Of Simon Rit Sent: 15. maj 2017 17:32 To: rtk-us...@openrtk.org<mailto:rtk-us...@openrtk.org> Subject: Re: [Rtk-users] Reconstructing from fan-beam projections Hi, I have added an example here: http://wiki.openrtk.org/index.php/FanBeam The values in the first and the third rows are not used, as illustrated in this example. We add them to do a 2D interpolation but we do this 2D interpolation exactly on the second row so that's not a problem. Note that it's a bit more tricky for iterative recon but we also have a solution for this if you need it. Best regards, Simon On Mon, May 15, 2017 at 4:31 PM, Jacob Frøsig <j...@force.dk<mailto:j...@force.dk>> wrote: Hi again, Thank you for the quick answer! An example would be great, thanks. I have one concern about copying the fan-beam data: Then we would have 2D projections for which each column is the same fan-beam projection. By this, values of the same row are equal even though the cone-beam geometry indicates the outer columns correspond to intensities of rays with longer travel time through the object and hence should have attenuated more. Is this neglectable? Again, thanks! Best regards, Jacob From: simon....@gmail.com<mailto:simon....@gmail.com> [mailto:simon....@gmail.com<mailto:simon....@gmail.com>] On Behalf Of Simon Rit Sent: 15. maj 2017 16:05 To: louie L <ghos...@hotmail.com<mailto:ghos...@hotmail.com>> Cc: Jacob Frøsig <j...@force.dk<mailto:j...@force.dk>>; rtk-users@public.kitware.com<mailto:rtk-users@public.kitware.com> Subject: Re: [Rtk-users] Reconstructing from fan-beam projections Hi, I agree. What I do is do a 3 slice sinogram from the fan-beam projections by copying the same data in each slice but reconstruct one 2D slice. If you need an example, I can quickly demonstrate this in a short Python script. Simon On Mon, May 15, 2017 at 4:01 PM, louie L <ghos...@hotmail.com<mailto:ghos...@hotmail.com>> wrote: Hi, I think you can carefully pad zeros to your projections. Reconstruct as if it is a 3d object. Take the middle slice as your fanbeam result. Let me know if it helps. Best regards, Louie Sent from my iOS Am 15.05.2017 um 15:55 schrieb Jacob Frøsig <j...@force.dk<mailto:j...@force.dk>>: Dear Rtk-users I was wandering if Rtk includes an implementation of a reconstruction method to reconstruct a 2D representation of an object given fan-beam projections. Or, if anyone has experience using e.g. FDKConeBeamReconstructionFilter on projections from line-detectors (fan-beam instead of cone-beam). I hope you guys can help. Yours sincerely Jacob Frøsig Project Manager Sensor Innovation FORCE Technology Park Allé 345 2605 Brøndby Denmark Phone: +45 43 25 00 00<tel:+45%2043%2025%2000%2000> Direct: +45 43 25 16 43<tel:+45%2043%2025%2016%2043> Skype for Business: j...@forcetechnology.com<mailto:j...@forcetechnology.com> Fax: +45 43 25 00 10<tel:+45%2043%2025%2000%2010> e-mail: j...@force.dk<mailto:j...@force.dk> www: forcetechnology.com<https://forcetechnology.com?utm_source=mail-signature&utm_medium=email&utm_campaign=EmployeeBranding> ************************************************************************* This email and any files transmitted with it may contain confidential information intended for the addressee(s) only. The information is not to be surrendered or copied to unauthorised persons. If you have received this communication in error, please notify us immediately by email at: i...@forcetechnology.com<mailto:i...@forcetechnology.com> ************************************************************************* _______________________________________________ Rtk-users mailing list Rtk-users@public.kitware.com<mailto:Rtk-users@public.kitware.com> http://public.kitware.com/mailman/listinfo/rtk-users _______________________________________________ Rtk-users mailing list Rtk-users@public.kitware.com<mailto:Rtk-users@public.kitware.com> http://public.kitware.com/mailman/listinfo/rtk-users
_______________________________________________ Rtk-users mailing list Rtk-users@public.kitware.com http://public.kitware.com/mailman/listinfo/rtk-users
