[Insight-users] Question on image to image metric implementations

[Markus Weigert]

Hi Luis,

thanks for your reply, but at what I was really targeting with my question 
is
the following (more theoretical):
One could consider the transformation field (in any dimension, say 3D) 
between two images
in terms of a  generic transform and thus optimize the metric between the 
two images by
purely optimizing the deformation field entries (starting with all 
deformation values set to 0).
Here, one may use LBFGSB optimizer or any optimizer from the toolkit to 
optimize the metric
with respect to all the deformation vectors entries.
In this case, the metric class would need a deformation field to be plugged 
in and need to return
the metric value and derivatives with respect to the deformation field 
entries.
Of course, the parameter spaces with which one had to deal in this case may 
reach up to hundreds
of millions of unknowns to be optimized for large 3D datasets (at highest 
resolution).
Also, one could use all kinds of regularisation on the calculated 
deformation field by "simply"
optimizing a cost function taking metric and  regularisation term (elastic, 
fluid, whatever) into account.
Do you think that this naive approach would be feasable using standard 
optimization routines like LBFGSB
as it is implemented in the toolkit or is it just not feasable?

Kind regards,
Markus



----- Original Message ----- 
From: "Luis Ibanez" <luis.ibanez at kitware.com>
To: "Markus Weigert" <m.weigert at fz-juelich.de>
Cc: <insight-users at itk.org>
Sent: Tuesday, September 26, 2006 12:52 AM
Subject: Re: [Insight-users] Question on image to image metric 
implementations


>
> Hi Markus,
>
> Please read the ITK Software Guide
>
>  http://www.itk.org/ItkSoftwareGuide.pdf
>
> in particular the Image Registration Chapter,
> and the section on "Deformable Registration".
>
> You can use a BSplineDeformableTransform as the
> spatial transformation in the Image Registration
> Framework.  From the resulting BSpline you can
> obtain a deformation fields.
>
> You will find coding examples in that chapter,
> and the source code of the example is available
> at
>
>
>     Insight/Examples/Registration
>
>
> You may also be interested in the Demons registration
> filter and the FEMRegistrationFilter.
>
>
> Regards,
>
>
>
>    Luis
>
>
>
> ========================
> Markus Weigert wrote:
>> Hi all,
>>  when using the ImageToImage metrics (for example
>> itk::MutualInformationImageToImageMetric), one needs to provide
>> a spatial transformation, which is used by the metric (for example to 
>> compute derivatives).
>> My question is what about using a deformation field (WarpImageFilter) as 
>> "transformation",
>> what may also be seen as the more general approach???
>> One could consider the deformation field as a transformation as well 
>> (with much more parameters, of course)
>> and calculate derivatives with respect to the deformation values (to 
>> control for example some registration process).
>> Is the framework open for this and how expensive would it be to implement 
>> such an approach (not only complexity
>> of calculation but also effort of implementation)?
>>  Thanks for any suggestions,
>> 
>> arkus  ------------------------------------------------------------------------
>>
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>