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

[Guangming Zang]

Hi simon,
i see, thanks for the help and explanation. after following your advice, it
works fine now.
Regards
Guangming

*Guangming Zang (Alex)*
*King Abdullah University of Science and Technology(KAUST)*
*University of Chinese Academy of Sciences(UCAS)*




2015-07-31 8:55 GMT+03:00 Simon Rit <simon.rit at creatis.insa-lyon.fr>:

> 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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