[Insight-users] More than one seed point in itk::FastMarchingImageFilter

[Guido H. Jajamovich]

Hi Francesco,

I would recommend changing the id of the second seed; that is,
seeds->Initialize();
seeds->InsertElement( 0, node1 );
seeds->InsertElement( 1, node2 );    // instead of:
seeds->InsertElement( 0, node2 );

It looks like you were replacing node1 with node2.
Sincerely,
Guido


On Tue, Jun 12, 2012 at 6:00 AM, Mr Francesco Grussu
<francesco.grussu at eecs.qmul.ac.uk> wrote:
> Dear all,
> I am trying to modify the FastMarchingImageFilter.cxx from the ITK Guide
> in order to use more than one seed point with a Fast Marching segmentation
> filter from itk::FastMarchingImageFilter .
>
> I suppose that I have to pass these seed points as Node containers
> (FastMarchingFilterType::NodeContainer) but I cannot understand how to do
> it exactly. Should I call the InsertElement() method of the
> FastMarchingFilterType::NodeContainer object (via a its smart pointer)
> more than once? To use more than one seed point, I thought to write
> something like that:
>
> ******************
>
>  typedef FastMarchingFilterType::NodeContainer           NodeContainer;
>  NodeContainer::Pointer seeds = NodeContainer::New();
>
>  InternalImageType::IndexType  seedPosition1;
>  seedPosition1[0] = SEED1X; // a macro previously defined
>  seedPosition1[1] = SEED1Y; // a macro previously defined
>
>  InternalImageType::IndexType  seedPosition2;
>  seedPosition2[0] = SEED2X; // a macro previously defined
>  seedPosition2[1] = SEED2Y; // a macro previously defined
>
>  const double seedValue = 0.0;
>
>  typedef FastMarchingFilterType::NodeType                NodeType;
>
>  NodeType node1;
>  node1.SetValue( seedValue );
>  node1.SetIndex( seedPosition1 );
>
>  NodeType node2;
>  node2.SetValue( seedValue );
>  node2.SetIndex( seedPosition2 );
>
>  seeds->Initialize();
>  seeds->InsertElement( 0, node1 );
>  seeds->InsertElement( 0, node2 );
>
> ******************
>
> However, the segmentation I get is the same as if I had used just the
> second seed point (with node2). node1 seems to be completely ignored by
> the Fast Marching Filter.
> Do you have any suggestions?
>
> Thanks a lot,
> regards
>
> --Francesco
>
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