[Insight-users] Explaining Vesselness getting Eigen Vectors

[Kishore Mosaliganti]

Hi all,

The code in Insight/Examples/Filtering/VesselnessMeasureImageFilter.cxx
is not included in the local CMakeLists.txt document for compilation.
Any reason for that?

Thanks,
Kishore

On Tue, Oct 6, 2009 at 2:38 PM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> Hi Kevin,
>
> Yes,
> use Open Source Software like OpenOffice for your presentation.
> Way to go !!!
>
>
>
> About the eigenvectors, you already listed the available options:
>
> Note however that in the case:
>
> A)  itkEigenAnalysis2DImageFilter, once you get the principal
>      eigenvector, the second one is orthogonal to it.  Therefore
>      you could simply plot the principal one...  and if you really
>      want to show the other you can display:
>
>                        (  Vx, Vy  )  = principal,  and
>                        ( -Vy,  Vx )  = secondary one
>
>
> B)  itkSymmetricEigenAnalysisImageFilter could be easily copy-pasted
>     and modified, in order to build a filter that computes the eigenvectors,
>     instead of the eigenvalues.
>
> C) This is as hard as running the EigenAnalysis class in an ImageIterator
>      loop and storing the output in a Vector image.
>
>
> BTW: Please note that it is quite straight forward to plot this using
>      Paraview:    www.paraview.org
>
>      Ploting vector fields with paraview is discussed in the
>      ITK Software Guide
>
>             http://www.itk.org/ItkSoftwareGuide.pdf
>
>
>
>  Good luck with your presentation,
>
>
>      Luis
>
>
> -----------------------------------------------------------------------------
> On Mon, Oct 5, 2009 at 2:14 PM, Kevin H. Hobbs <hobbsk at ohiou.edu> wrote:
>> I need to explain the vesselness filter to my bosses ( OOImpress
>> presentation Friday ).
>>
>> The documentation for itkHessian3DToVesselnessMeasureImageFilter and the
>> reference
>> http://www.spl.harvard.edu/pages/spl-pre2007/pages/papers/yoshi really
>> only refer to the properties of the eigenvalues for various shapes.
>>
>> We are left without an intuitive understanding of what the Eigen values
>> and vectors mean.
>>
>> To help us understand what the Eigenvalues are I made a little 2D
>> doodle, ran it through itkHessianRecursiveGaussianImageFilter and
>> itkSymmetricEigenAnalysisImageFilter so that I could have slides of the
>> lesser and greater eigenvalues.
>>
>> These are great! It's obvious from these images that the lesser
>> eigenvalue has minima along the center of the big bright squiggly line
>> in my doodle, and the greater eigenvalue has maxima along all of the
>> edges.
>>
>> I think the last thing I need to give everybody an intuitive sense of
>> what Eigen analysis does, is to get and plot both eigenvectors.
>>
>> As far as I can tell from the Doxygen, there is no filter that can give
>> me both eigenvectors. itkEigenAnalysis2DImageFilter will give me only
>> the vector for the larger eigenvalue and
>> itkSymmetricEigenAnalysisImageFilter gives only the eigenvalues. Is that
>> correct?
>>
>> Would it be easier to just iterate over the hessian image and call
>> itk::SymmetricEigenAnalysis::ComputeEigenValuesAndVectors over and over
>> printing x,y,ev11,ev12,ev21,ev22 for plotting with octave's quiver, or
>> adapt itkSymmetricEigenAnalysisImageFilter to produce an image (or
>> images) of the eigenvectors?
>>
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