[Insight-users] Geodesic active contour shape prior levelset

[Kishore Mosaliganti]

Hi Petin,

I have tried using the ShapePriorLevelSet filter before.

It is true that if you eliminate the registration aspect, then the
final result will be better. This is because of fewer parameters to
estimate for finding the global optimal set. Giving a registration
initialization is a good idea where it is possible.  You can also try
to automate that by specifying different starting orientations and
choosing the most common orientation observed (via voting etc). That
may help reduce the registration burden on the user.

The convergence of the level-set is due to various terms including the
gradient. What you visually see as the object boundary from intensity
may not be the location of the minima in the second gradient etc. The
levelset terms are attracted to a gradient basin. Therefore, you may
be perceiving the difference. The boundary is always going to be
difficult because of the partial voluming effects of neighboring
voxels. I think your result is fairly good from my perspective.

Kishore

On Thu, Sep 16, 2010 at 2:55 AM, petin <petin75 at gmail.com> wrote:
> Dear Itk users,
>
> I'm using  GeodesicActiveContourShapePriorLevelSetFilter image filter to
> segment 2d sagittal
> images of vertebrae from L1 to S1. We created an average shape as described
> within the
> itk programming guide using about 50 images for each vertebrae, so the
> segmented vertebrae
> were registered ,we did the pca and so on....
> After the training set has been created we tried the algorithm on some
> image, the user was
> able to click on the vertebrae and from this seed point the segmentation
> started.  We found that the
> final resul is a lot influenced by the rotation of the object to be
> segmented, than we modified a bit
> our user interface so that the user could specify an initial rotation of the
> vertebrae to be segmented.
> The results we got were quite good, but still there are some cases like
> those attached where the
> final segmentation is not perfectly adherent to the vertebrae border and the
> segmented object
> is not perfectly rotated.
>
> Could you please give me some advice ?
> Any hint would help.
> Kind regards
> -Loris
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