[Insight-users] active contour level set segmentation

[Alexandre GOUAILLARD]

hi amy,

weclome to ITK.

yes, this is the correct list to ask questions about code in review.

I forwarded your comment from the IJ to kishore (mosaliganti) who is
the main developer of the level set code yesterday, and you should get
an answer soon.

regards,

alex.

On Tue, Dec 22, 2009 at 1:08 PM, Amy C <mathematical.coffee at gmail.com> wrote:
> Hello,
> Is this the right list to send questions about code in Review? I'm sorry if
> it isn't. Question is aimed towards anyone familiar with this particular
> submission.
>
> I've been looking at the Active Contours Without Edges code (level set
> segmentation) in publication 323 of the insight journal which is currently
> in the 'Review' folder of the itk code. However I'm looking at the
> (20-Dec-09) CVS version since the version linked to by insight-journal.org
> is old and has a couple of errors that have since been fixed.
>
> I wanted to know about AtanRegularizedHeavisideStepFunction ( H_eps(x) = 1/2
> + 1/pi * atan(x/eps) ), the header file evaluates the derivative as
>    1/pi*1/(1+x^2/eps^2),
> but I think it should be
>   1/(pi*eps) * 1/(1+x^2/eps^2).
> Is this correct?
>
> Also, could anyone tell me if the VolumeRegularizationTerm comes from a
> particular paper or something?
> (RegionBasedLevelSetFunction->ComputeVolumeRegularizationTerm()). The
> doxygen does say what it is (in the PDE), but I wondered what it
> corresponded to in the energy functional. (It looks like it encourages the
> volume of the level set to be a particular value. The original papers use
> positive inside/negative outside for level sets which is opposite to the
> common convention. I just want to verify the PDE for myself by deriving it
> from the functional, so that I can stop being confused about the flipped
> positive and negative signs in the code :p). And this term is multiplied by
> a factor of 2 in the PDE (as well as the user-supplied weight) which seems
> strange, since most squared terms in a functional would have a factor of .5
> to counteract this.
>
> Cheers,
> Amy
>
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