[Insight-users] GeodesicActiveContours still an unsolved problem

[Luis Ibanez]

Hi Ella,

The Fast Marching Filter takes two inputs.

                A) A list of set points

and

                B)  A speed image


The input (A) is required, while the input (B) is optional.


When (B) is not provided, the FastMarching filter assumes
that the a uniform speed field is to be used, and therefore
it computes the equivalent of a distance map to the set of
seed points.


What you need to pass as input to the GeodesicActiveContour
filter is a level set image.  Such input can be generated by the
FastMarching filter, among many other methods.  If you choose
to use the FastMarching filter to generate the input of the
GeodesicActiveContour you should make sure that the zero
set of the output in the FastMarching filter is close enough
to the shape that you are trying to segment.

One way to verify this is by thresholding the output of the
FastMarching and visualizing it with your favorite viewer
program.


     Luis


------------------------------------------
On Mon, Feb 14, 2011 at 8:33 AM, Ella Maria Kadas <ella_kadas at yahoo.com>wrote:

> I still don't really understand what does FastMarchingFilter get as input.
> I tried the FastMarchingFilter example from ITK/Segmentation and i don't see
> how providing only the output of the Sigmoid Filter and seed points i only
> get a black image.
> I tried to use the SignedDanielssonDistanceFilter and the Image that i get
> from it looks pretty good. so i used
>
>
>
>         smoothing->SetInput([itkImage itkImporter]->GetOutput() );
>
> gradientMagnitude->SetInput( smoothing->GetOutput() );
>
> sigmoid->SetInput( gradientMagnitude->GetOutput() );
>
>  geodesicActiveContour->SetInput( distanceMap->GetOutput() );
>
> geodesicActiveContour->SetFeatureImage( sigmoid->GetOutput() );
>
>  thresholder->SetInput( geodesicActiveContour->GetOutput() );
>
> and update the threshold.
>
> But the result is still a black image. Any ideea what am i still doing so
> wrong.
>
> Thanks in advance,
>
>    Ella
>
>
>
>
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