[vtkusers] fitting curve to points

[dean.inglis at on.aibn.com]

I have extracted the center path from a binarized image of
the cross section of a leg bone using 

                             -> vtkImageGradient  \  
vtkImageEuclideanDistance ->|                      |-> vtkImageNonMaximumSuppression
                             -> vtkImageMagnitude /


then extracted the points with 

vtkImageNonMaximumSuppression -> vtkThresholdPoints

I would like to fit a closed polyline to the points,
but the points from vtkThresholdPoints are not in a
spatially sequential order.  Any ideas how to do this?

Dean