[Rtk-users] SIRT Reconstruction

[Lotte Schyns]

Thanks! I will try both the SIRT with 100 iterations and the conjugate 
gradient method. What exactly are the weights (input 2) and input 
support mask in rtkConjugateGradientConeBeamReconstructionFilter?

On 18-07-17 11:31, Cyril Mory wrote:
> Hi Lotte,
>
> I had a very quick look at what you are doing. It looks fine to me, 
> you just need to perform way more iterations in the SIRT case. 100 
> would be a good start. SIRT is more stable than SART when there are 
> inconsistencies in the projection data, but converges slowly.
>
> An alternative to SIRT, which minimizes the same cost function with a 
> faster algorithm, is the conjugate gradient algorithm. You should 
> obtain nice results with something like 30-40 iterations (look for 
> rtk::ConjugateGradientConeBeamReconstructionFilter if you want to give 
> it a try).
>
> Best regards,
> Cyril
>
>
> On 18/07/2017 11:17, Lotte Schyns wrote:
>> Hello,
>>
>> We are having problems with the SIRT reconstructions. They seem very
>> strange and blurry. However, other reconstructions (SART, FDK,
>> iterativeFDK) look perfect. I uploaded an example of a SART and a SIRT
>> reconstruction (same parameters) to
>> https://www.dropbox.com/sh/7a4bkyjg43zjmy7/AAAp4tJrk9HedMEEuIKsGYDSa?dl=0. 
>>
>> I also uploaded a minimalistic version of the code that I used (the
>> paths in CMakeLists.txt probably need to be adapted to your system). You
>> can alternate between SART and SIRT by changing line 143. The raw data
>> is also available on dropbox. I didn't use
>> rtkXRadRawToAttenuationImageFilter, because our projections are already
>> corrected for the dark field and flood field, so
>> (signal-dark)/(flood-dark). I just take the natural logarithm and
>> multiply by -1. Do you know what could be the problem with the SIRT
>> reconstructions? Are we using wrong parameters? Thanks for your time.
>>
>> Lotte
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>