[Rtk-users] The result got from ADMMTV from shapp-logan generated from RTK

[Simon Rit]

Hi,
It looks to me that you haven't converged. I'm not the specialist of this
algorithm and the specialist won't be near a computer in the coming weeks
but when I try with more iterations in the data attachment term:
  rtkadmmtotalvariation -p . -r proj.mha -o admmtv.mha -g geo.xml
--spacing 1 --dimension 128 --alpha 1 --beta 1000 -n 10
it's more satisfactory. There are rings at the top and the bottom of the
cone-beam which should be reduced with more TV (greater alpha, see doc here
<http://www.openrtk.org/Doxygen/classrtk_1_1ADMMTotalVariationConeBeamReconstructionFilter.html>)
or with a finer spacing (see this publication
<http://dx.doi.org/10.1088/0031-9155/49/1/010>).
Simon

On Thu, Jul 30, 2015 at 2:16 PM, Guangming Zang <guangming.zang at kaust.edu.sa
> wrote:

> Hi Simon and Chao,
>
> i am currently do some comparisons between different reconstruction
> methods for Shapp-Logan dataset.
>
> the commands are:
>
> rtksimulatedgeometry -n 360 --arc -360 -o
> geo.xml   --sdd=955.4050067  --sid=500.0
>
> rtkprojectshepploganphantom -g geo.xml --phantomscale 64 -o proj.mha
> --dimension 512,512
>
>
>
> when using FDK or SART algorithm from RTK, I can got pretty good results
> indeed(to see clearly, set contrast as [0.95,1.13], i.e., windows as 0.09
> and levels as 1.04 for all results got). When running ADMMTV command below,
> though the geometry is as same as SART and FDK, the result got from ADMM
> looks weird.(pls see attached central slice of ground truth and ADMM, same
> contrast with other algorithm)
>
> rtkadmmtotalvariation -p . -r proj.mha  -g geo.xml -o
> SL_ADMM_0.001_0.01.mha     --dimension 128,128,128 --spacing 1,1,1    -n 2
> --CGiter 3 --origin -64,-64,-64 --alpha 0.001 --beta 0.01 --time 1
>
>  [image: 内嵌图片 1][image: 内嵌图片 2]
>
> Is it because the CG algorithm used by ADMM, or parameters setting issues
> here?? if it is parameters setting problem , would you help me and give a
> nice values for alpha and bate used here?
>
> BTW, I had tried the –alpha from [0.001,1] and –bate[0.01,10] already
> (including default value)
>
> Thanks and regards
>
> Guangming
>
>
> ​​
> *Guangming Zang (Alex)*
> *King Abdullah University of Science and Technology(KAUST)*
> *University of Chinese Academy of Sciences(UCAS)*
>
> ​
>
>
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