[Insight-users] Building shape model to be used with GeodesicActiveCountourShapePriorLevelSetImageFilter

[Luis Ibanez]

Zach, Lino,

The creation of a Signed Distance map has been
logged as a Feature Request for a while.

It entry is Bug #737
http://www.itk.org/Bug/bug.php?op=show&bugid=737&pos=23

You may want to vote for this bug in order to increase
its priority.

The plan so far, is to implement it as you just suggested,
by running the DanielssonDistanceMap filter twice, the
first time on the binary image, and the second time in
the negation of the binary image.

You can also use the ReinitializeLevelSetImageFilter
http://www.itk.org/Insight/Doxygen/html/classitk_1_1ReinitializeLevelSetImageFilter.html#_details
in order to produce a signed distance function.
The DanielssonDistanceMap filter will probably be faster.


   Regards,


      Luis


------------------------------
ramirez at ece.ualberta.ca wrote:

> Hi Zach,
> 
> Thank you for the reply, especially for the part of using the Danielsson
> distance map filter to compute the signed distance from binary images. I
> really didn’t think of that one.
> 
> Thanks again
> 
> Lino
> 
> 
>>Based on Leventon's paper that initially described the shape model
>>level sets (
>>http://www.ai.mit.edu/people/leventon/Research/0006-CVPR/cvpr00.pdf ),
>>and looking at the ITK implementation thereof, this is correct.
>>
>>Note that you need to use the signed level set output -- not binarized
>>inside/outside version or single isocontours from the level sets -- as
>>input to the ImagePCAShapeModelEstimator. As you probably know, and for
>>the benefit of others reading this, the "shape model" training images
>>need to be represented as signed distances from the edge of the shape.
>>Fortunately, this is the stock in trade of level sets, so you can use
>>that output raw.
>>
>>I was looking around for a class in ITK that could compute signed
>>distance maps from a binary image, in case that is all the input one
>>has for training images (e.g. input from a non-level-set segmentation
>>method). I can't find anything explicitly there (is there??) but of
>>course one could create a signed distance image by two applications of
>>the Danielsson Distance Map filter to a binarized inside/outside image
>>and its complement, and subtracting the two.
>>
>>Zach Pincus
>>
>>Department of Biochemistry and Program in Biomedical Informatics
>>Stanford University School of Medicine
>>
>>
>>On Aug 8, 2004, at 1:40 PM, Lino Ramirez wrote:
>>
>>
>>>Dear ITK users,
>>>
>>>I would like to do segmentation of vertebrae in x-ray images using the
>>>GeodesicActiveCountourShapePriorLevelSetImageFilter. I already had a
>>>look at the example available in the CVS repository. However, in the
>>>example, it didn’t explain how to make the models. For what I have
>>>read so far, I guess that the following steps would help me make such
>>>a model.
>>>
>>>1.- Align the training images
>>>2.- Segment each image using a level-set based method
>>>3.- Use the output level set as the inputs for
>>>ImagePCAShapeModelEstimator
>>>
>>>Do these steps make sense? Or is there some other approach or example
>>>I should follow?
>>>
>>>Thank you and have a nice day
>>>
>>>Lino
>>>_______________________________________________
>>>Insight-users mailing list
>>>Insight-users at itk.org
>>>http://www.itk.org/mailman/listinfo/insight-users
>>
> 
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