Hi, You can try any iterative reconstruction, they can also handle short scans. Start with a few iterations of rtksart or rtkconjugategradient. However, the nature of the artifacts indicate more a problem in the geometry in my opinion. I have seen such errors when, for example, rotating in the wrong direction. I can have a look if you share the dataset. Cheers, Simon
On Fri, Sep 16, 2016 at 2:56 PM, Andreas Gravgaard Andersen < [email protected]> wrote: > 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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