Thanks for the suggestions, Simon and Cyril! I have been carefully looking though the geometry and from what I understand of the transformations matrices, the geometry looks correct/(as expected).
HOWEVER: I found out that the reason for the Hnd to behave differently were because had used half-fan scans (full-arc). When I used a full-fan (half-arc) scan of Hnd projections the same artifacts occurs! Are there other (built-in) means of improving half-arc scans, than the parker short scan filter? Parker short scan does a decent job, but the result is still far from the quality of the Varian software reconstruction at least for the CatPhan. Best regards Andreas __________________________________ Andreas Gravgaard Andersen Department of Oncology, Aarhus University Hospital Nørrebrogade 44, 8000, Aarhus C Mail: [email protected] Cell: +45 3165 8140 2016-09-14 9:10 GMT+02:00 Cyril Mory <[email protected]>: > One suggestion since it works with the Hnd projections: > You can run rtkprojections twice (with the Hnd projections, then with Xim > projections) and output two projection stack files and two geometry files, > then compare the projection stack files by subtracting one to the other > (with SimpleRTK or clitk) and the geometry files with diff. If they are > identical, then I do not see any reason why the reconstructions should be > different, so my guess is that you will find differences. > > > On 09/13/2016 10:18 PM, Simon Rit wrote: > >> Hi, >> I have almost never worked with Varian data but it looks like a >> geometry problem. Maybe the problem comes from a bad ordering of the >> projections which results in assigning a bad geometry to each >> projection. How did you name your projections? Maybe check that the >> order matches that of the RTK geometry file. Otherwise, there might be >> an issue in the creation of the geometry file itself. >> All this sounds good, happy bug hunt and don't hesitate to share your >> code when you feel it's ready. >> Simon >> >> On Tue, Sep 13, 2016 at 7:06 PM, Andreas Gravgaard Andersen >> <[email protected]> wrote: >> >>> Dear RTK experts, >>> >>> I am reconstructing Varian ProBeam projections of the Xim image format. I >>> have written the reader myself - very similar to the Hnd one already >>> available with RTK. >>> Links to my fork: [XimReader, XMLReader, GeometryReader] >>> >>> The reader apparently works (Images and angles displays as expected in >>> UI), >>> however when reconstructing with a regular FDK I get a reconstructed >>> image >>> that is smeared out around the high and low density areas [see attached >>> image] >>> >>> I'm using half arc, full fan images with no bow-tie filter from Scripps >>> (~520 projections). Fixed detector and source (offset=0) with SID=2m, >>> SDD=3m. >>> >>> For the Hnd projections the reconstruction works perfectly (Same >>> algorithm). >>> The reconstruction of the Xim projections performed on Varian software >>> works >>> perfectly. >>> >>> Without the Parker Short Scan Filter the first and last projections >>> creates >>> streaks across the reconstruction as if they were way too bright. >>> If the first few projections are excluded, the following projection will >>> act >>> the same way. >>> >>> The projections are corrected for beam hardening and all the projections >>> have the expected attenuation. >>> No "smearing" filters (like median) is used, and iterative reconstruction >>> makes the same artifacts. >>> >>> Setting the value of the first and last projection to zero has the same >>> effect as excluding. Changing the ramp filter only changes noise, not the >>> artifacts. >>> >>> Have any of you had a similar problem? Am I missing something? >>> Any suggestions are welcome I'm running out of ideas. >>> >>> Best regards >>> Andreas >>> >>> __________________________________ >>> >>> Andreas Gravgaard Andersen >>> >>> Department of Oncology, >>> >>> Aarhus University Hospital >>> >>> Nørrebrogade 44, >>> >>> 8000, Aarhus C >>> >>> Mail: [email protected] >>> >>> Cell: +45 3165 8140 >>> >>> >>> _______________________________________________ >>> Rtk-users mailing list >>> [email protected] >>> http://public.kitware.com/mailman/listinfo/rtk-users >>> >>> _______________________________________________ >> Rtk-users mailing list >> [email protected] >> http://public.kitware.com/mailman/listinfo/rtk-users >> >> >
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