[Insight-users] Using deformation fields when testing registration quality?

[Karthik Krishnan]

You could also try metrics to compare deformation fields.

McCane, B., Novins, K., Crannitch, D. and Galvin, B., On Benchmarking
Optical Flow, Computer Vision and Image Understanding, 84(1), pp
126-143, 2001

See Section 5 titled Error Metrics in [1]. It provides 2 metrics to
compare deformation fields. It also surveys other metrics used to
compare deformation fields in literature and illustrates their
shortcomings.

Their methods are openly available at
http://sourceforge.net/projects/of-eval/files/ .

Motes : if you port them to ITK, and contribute it to IJ, I'd he happy
to include them in the toolkit.

Thanks
--
karthik

On Mon, Oct 26, 2009 at 1:32 PM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> Hi Motes,
>
> I would suggest that you subtract the Known deformation field
> from the deformation field that results from the registration. This
> will give you a "residual" deformation field. Then you could
> compute the Average Magnitude of all the vectors in these
> residual deformation field.
>
> It may also be worth to report the "largest magnitude" of that
> residual deformation field.
>
> For subtracting two deformation fields, the itkSubtractImageFilter
> should do the trick (although I have not tried this filter with images
> of vectors).
>
> The computation of the average and maximum magnitude may
> require you to write a customized while-loop with Iterators.
>
> It should take about 30~40   lines of code....  :-)
>
>
> Please let us know if you find any problem,
>
>
>     Thanks
>
>
>         Luis
>
>
> -----------------------------------------------------------------------------------------
> On Mon, Oct 26, 2009 at 12:11 PM, motes motes <mort.motes at gmail.com> wrote:
>> I would like to measure the quality of my modfied BSplineDeformable
>> transform. I have used one of the ITK examples to create a known
>> deformation of the fixed image that I use as the moving image.
>>
>> But how do I use this known deformation in the quality measure? Since
>> the deformation field is applied to the fixed image and the result is
>> the moving image I don't see what benefit it does when measuring the
>> quality of the registration?
>>
>> How are deformation fields used in this context?
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