[Insight-users] Re : active contour, snake, deformable model and level set segmentation ???

[Luis Ibanez]

Hi Juliette,


I'm not sure what you mean by:


   "Level set (purely level set without active contour)
    based segmentation?"


The level set abstraction is implemented in such a way that at
every pixel ITK solves an increment of a partial differential
equation.


The surface of the object happens to be defined at the loci
where the level set image has zero values.




In practice, the distinction between a LevelSet and an Active
Contours (or Snakes) is mostly of importance for those researchers
who need to complete their annual quota of published papers and
therefore are forced to be inventing "new" things every time, even
when they are reincarnations of older ideas.


In essence, the difference between LevelSets and Active contours
is one of software implementation.


If you need to solve a real and practical problem, we could
advice you on what ITK methods to use.


If you are in need of a flashy name for a segmentation method
then...  there is a lot out there to choose from.   :-)


    Regards,


       Luis


----------------------
Juliette Deniau wrote:
> Hi Luis,
> 
> A one more question to clear completely my understanding.
> 
> You said that “The Level Set implementations of deformable models have all
> the "LevelSet" string as part of their name” . Does this means that 
> there is no
> 
> level set (purely level set without active contour) based segmentation?
> Thank you for your time
> 
> Juliette 
> 
>  
> 
> 
> ------------------------------------------------------------------------
> *De :* Luis Ibanez <luis.ibanez at kitware.com>
> *À :* Juliette Deniau <juliette.deniau at yahoo.fr>
> *Cc :* insight-users at itk.org
> *Envoyé le :* Mardi, 2 Décembre 2008, 21h04mn 06s
> *Objet :* Re: [Insight-users] active contour, snake, deformable model 
> and level set segmentation ???
> 
> 
> Hi Juliette,
> 
> 
> Your observations are correct.
> 
> If you are looking for a mesh-based implementation of a deformable 
> model, then you should look at
> http://www.itk.org/Insight/Doxygen/html/classitk_1_1DeformableSimplexMesh3DBalloonForceFilter.html
> 
> 
> and its example application in
> 
>     InsightApplications/DeformableModelSimplexMesh
> 
> 
> This is closer to what is known as "Snakes" in the medical field.
> 
> The Level Set implementations of deformable models have all
> the "LevelSet" string as part of their name.
> 
> 
> They will be:
> 
> 
> $ find . -name "*LevelSetImageFilter.h"
> ./itkAnisotropicFourthOrderLevelSetImageFilter..h
> ./itkCannySegmentationLevelSetImageFilter.h
> ./itkCurvesLevelSetImageFilter.h
> ./itkGeodesicActiveContourLevelSetImageFilter.h
> ./itkGeodesicActiveContourShapePriorLevelSetImageFilter.h
> ./itkIsotropicFourthOrderLevelSetImageFilter.h
> ./itkLaplacianSegmentationLevelSetImageFilter.h
> ./itkNarrowBandCurvesLevelSetImageFilter.h
> ./itkNarrowBandLevelSetImageFilter.h
> ./itkNarrowBandThresholdSegmentationLevelSetImageFilter.h
> ./itkSegmentationLevelSetImageFilter.h
> ./itkShapeDetectionLevelSetImageFilter.h
> ./itkShapePriorSegmentationLevelSetImageFilter.h
> ./itkThresholdSegmentationLevelSetImageFilter.h
> ./itkUnsharpMaskLevelSetImageFilter.h
> ./itkVectorThresholdSegmentationLevelSetImageFilter.h
> 
> 
> 
> Please let us know if you have further questions,
> 
> 
>     Thanks
> 
> 
>       Luis
> 
> 
> 
> ------------------------
> Juliette Deniau wrote:
>  > Hi All,
>  >
>  > I’m confused about what type of segmentation methods are within itk, 
> in particular the ones related to active contour and level set?
>  >
>  > In my understanding, active contour is the same as a deformable model 
> and the same as a snake. The levelset segmentation is another type (use 
> a PDE to evolve the curve).
>  >
>  > In itk there are some active contours implemented with the level set 
> framework like the CurvesLevelSetImageFilter, I’m alright?
>  >
>  > Can any one tell me what are the segmentation filters which are 
> purely active contour (snake) and those which use level set to evolve 
> the curve? 
>  > Sorry if my question is too stupid!
>  >
>  > Thanks a lot
>  >
>  > Juliette
>  >
>  >
>  >
>  > ------------------------------------------------------------------------
>  >
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