[Insight-users] input for levelset segmentation algorithms

[Luis Ibanez]

HI Kai,

A simper way to do it is to smooth the binary image
using a Gaussian smoothing filter, and then rescale
the intensities to be between -0.5 and +0.5.

You can do this with the filters:

SmoothingRecursiveGaussianImageFilter
http://www.itk.org/Insight/Doxygen/html/classitk_1_1SmoothingRecursiveGaussianImageFilter.html

and

RescaleIntensityImageFilter
http://www.itk.org/Insight/Doxygen/html/classitk_1_1RescaleIntensityImageFilter.html


Note that the level set does not have to be a distance
funcion from your contour. Smoothing with a large Gaussian
of large sigma may be good enough.

Note that Sigma in the filter above is expressed in physical
units (e.g. millimeteres) and not in pixels.

You will find descriptions of both filters in the SoftwareGuide


       http://www.itk.org/ItkSoftwareGuide.pdf




Regards,


   Luis



------------------
Kai Li wrote:
> After browsing the ITK classes, it seems that a possible method could be:
> 1) first extract the contour of the binary image,
> 2) feed the contour as input to the DanielssonDistanceMapImageFilter
> 3) Flip the sign of the distances of the pixels within the contour,
>    ending up with the input initial level set to the level set algorithms.
> Not sure if there is a more direct or better way to archieve this...
> 
> Kai
> 
> On Thu, 22 Jul 2004, Kai Li wrote:
> 
> 
>>Hi,
>>  I'm considering to use one of the Levelset segmentation algorithms, say
>>ShapeDetectionLevelSetImageFilter. As the documentation of ITK says,  one
>>of the inputs for algorithm is the initial level set: "The initial level
>>set is a real image which contains the initial contour/surface as the zero
>>level set. For example, a signed distance function from the initial
>>contour/surface is typically used..." My question is how to convert a
>>binary image, which is generated by a preprocessing method, to the
>>such initial level set in ITK.
>>
>>Any help is highly appreciated!
>>
>>Kai
>>_______________________________________________
>>Insight-users mailing list
>>Insight-users at itk.org
>>http://www.itk.org/mailman/listinfo/insight-users
>>
> 
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