[Insight-users] Curvature term in ShapeDetectionLevelSetImageFilter

[Luis Ibanez]

Hi Nils,

In order to prevents leaks the ratio between the
propagation scaling and the curvature scaling
has to be modified.

You may want to try reducing the propagation scaling
factor as you increase the curvature scaling.

The drawback in doing this is that if your initial
level set is far from the actuar borders of the
tubular structure that you want to segment, a low
propagation scaling may be insufficient for bringing
the level set to the expected edge.

Note however that this balance of the scalings can
only reduce the leaks, but will not prevent them from
appening. As long as there is an open gap in the
feature image, the level set will leak, it is just
a matter of how many iterations it will take for it
to leak.

You may want to rework the feature image in order
to make darker the edges. This can be done by reducing
the "beta" parameter of the Sigmoid, and by using
a smaller number (in absolute value) for the "alpha"
parameter of the sigmoid.  The feature image should
look almost as a binary imaga of the expected segmentation.
(With almost black in the edges and almost white in
the internal region to be segmented).
(I'm assuming that you are using a sigmoid filter for
preparing the feature image to be passed to the
ShapeDetection filter...   is that the case ? )

You may want to experiment also with letting the filter
run for less iterations.

--

Please let us know if you continue experiencing problems.

In that case it may be desirable to figure out a better
way to initialize the filter for performing your segmentation.


Regards,


    Luis



---------------------
Nils Hanssen wrote:
> Hi,
>  
> I want to segment a tubular object with the ShapeDetectionLSIF. The 
> initial level-set is the "axis" of the tubular object.
> To prevent the contour from leaking through gaps in the edge-map, I set 
> the curvature-weighting with values between 0.02 and 5.
> The size of the gaps is approx. 3% of the perimeter of the contour, but 
> I was not able to stop the leaking.
>  
> What do I have to tune to achieve a significant smoothing?
>  
>  
> Regards,
> Nils
>  
>  
>  
>