[Insight-users] FW: Problem with Demons Variant Deformable Registration

[Nithiananthan, Sajendra]

Hi Tom,

When I noticed the differences I wasn't using your supplied command line
program but was creating an instance of your implementation of
itk::FastSymmetricForcesDemonsRegistrationFilter in my own application (I am
reading data in a different format). I change an include and a typedef to
compare different implementations, using their default parameters and the
same sigma for smoothing. 
In ESMDemonsRegistrationFunction the default MaximumUpdateStepLength is 0.5
and default gradient is Symmetric, which is as you recommend. I don't
understand your suggestion for the update-rule parameter, "-a2". Looking at
the command line app, DemonsRegistration.cxx, you need -a1 to create
itk::FastSymmetricForcesDemonsRegistrationFilter, -a2 would create
itk::DiffeomorphicDemonsRegistrationFilter. Wouldn't the former act more
similar to the basic symmetric forces demons implementation? Please correct
me if I am missing something.

As for issues, I did have some difficulties getting the project compiled on
Windows, but eventually I managed. I think most of that was around the use
of Getopt in the command line program. I can't recall if there were any
issues with the registration code itself, if you have tried on Windows you
would know as well as I.

Thank you again,
Sajendra


> -----Original Message-----
> From: tom.vercauteren at gmail.com [mailto:tom.vercauteren at gmail.com]On
> Subject: Re: FW: Problem with Demons Variant Deformable Registration
> 
> 
> Hi Sajendra,
> 
> I am glad to hear that you were able to use my code succesfully.
> 
> As Torsten pointed out, it should indeed be possible to "get the best
> of both worlds". In the code I posted on the Insight Journal, It
> should be possible to use a fast symmetric force that behaves very
> similarly to the basic symmetric forces demons implementation but has
> a reduced computation time.
> 
> The difference you experience might be related to different default
> parameters. More specifically, from the command line program I posted
> you should at least put the following options '-l0.5 -a2 -t0' if you
> want to match the basic symmetric forces demons implementation. Of
> course you also need to use the same sigmas for smoothing.
> 
> Another possible issue might be related to the version of ITK that you
> use. I filed a few bug reports anf forgot when they were fixed:
> http://www.itk.org/Bug/view.php?id=3985
> http://www.itk.org/Bug/view.php?id=3958
> http://www.itk.org/Bug/view.php?id=3973
> http://www.itk.org/Bug/view.php?id=3972
> 
> Let me know if you find other issues.
> 
> Best regards,
> Tom
> 

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