Hi Vincent, There is a problem indeed! It's hard to guess what's the problem from the images you sent. I would check the projections to see what could be wrong. The first thing I would check for example is whether air is really at 0 (as it should be). You can also look at the difference between the forward projections of this first iterate and the measured projections. It's known that SART should be stopped at a few iterations but 1 should not give such a result. You can always check if the conjugate gradient provides a better result, you can add some regularization in it. Good luck solving this! Simon
On Wed, Oct 23, 2019 at 3:03 PM vincent <v...@xris.eu> wrote: > Hi everyone, > > I am trying to reconstruct a volume representing an aluminum casted part > and investigate the differences between FDK and SART. > > Here are the parameters involved: the images are 700*820 pixels and I > have 900 projections. The physical pixel size is 0.28 mm and the sdd > and sid are 558.3 mm and 461.3 mm respectively, which gives me a > magnification factor of 1.2 roughly. I performed one iteration of SART > with CudaRayCast as forward and backward projectors and I wanted to > reconstruct a 700*700*700 volume with a 0.23 mm (= 0.28/1.2) voxel > size. The result is shown on the two pictures attached: > > https://ibb.co/8sLdJxw > https://ibb.co/N3NLg2D > > The result is getting worse as I increase the number of iterations > > I have a hard time understanding where the stripes come from. A > reconstruction with the standard 256*256*256 volume and 1mm spacing > gives a "smoother" result, closer to what FDK gives. I thought it might > be related to the linear system resolution, but unless I am mistaken, I > am trying to solve a system with 700*700*700 unknown with 700*820*900 > equations, which should be ok. > > Furthermore, the reconstruction with FDK at the same "full" resolution > gives satisfactory results. > > Any help/explanation will be greatly appreciated ! > > I thank you very much in advance, > > Vincent > > > > > _______________________________________________ > Rtk-users mailing list > Rtk-users@public.kitware.com > https://public.kitware.com/mailman/listinfo/rtk-users > >
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