[Insight-users] Curvature in Level Set

[Karl Krissian]

Hello,

I don't think there is any problem in the curvature computation.
If I understand well, the experiment you are doing is almost equivalent
to computing the curvature on a binary image of a circle,
which cannot lead to good results at small scales.

In practice, if you increase the curvature weight, your statistics
will get much better, because level set result will be smoother.

Regards,


Sah Rayman wrote:

>I found some "wierd behavior" of the curvature
>calculated in SegmentationLevelSetFunction. 
>
>While I expect the curvature to be 0.0125 everywhere, 
>the actual curvature has a mean of 0.0137 (which is
>good), but a s.t.d of 0.4. In another words, when the
>tangent circle is actually of radius 80, the
>calculation tells me the radius is 2 or 1 at some edge
>points, and even concave in some other points.
>
>Is it true that there are errors in curvature
>calculation in the range of my discription? Or, there
>must be something wrong in my application?
>
>======================================
>Here is what I do in the test.
>
>Full image is 256x256, ground truth is a circle whose
>radius is 80 pixels, initial is a 60-pixel-radius
>circle with a same center.
>
>I disabled advection, curvature term, and there are
>only speed term. Speed is +1 inside my ground truth,
>and -1 otherwise. In fact, curvature weight is 1e-6 to
>enable the curvature calculation.
>
>After 180 iterations, I observe the output of
>ComputeMeanCurvature() for one iteration, and take
>statistics.
>
>The output segmentation matches well with my ground
>truth.
>======================================
>
>
>
>
>
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-- 
Karl Krissian, PhD
Instructor in Radiology, Harvard Medical School
Laboratory of Mathematics in Imaging, Brigham and Women's Hospital
Tel:617-525-6232, Fax:617-525-6220