[vtkusers] grid data

[John Hunter]

I am working on an application to identify electrode locations from CT
data.  The user identifies the bright spots in the CT slices using
vtkImagePlaneWidgets.  The electrodes are placed on the surface of the
brain during surgery and are on a rubber sheet that curves around the
surface of the brain.  The electrodes are arranged on the sheet in an
MxN lattice, though the sheet itself is curved.  I would like to store
the data in the appropriate vtk data structure (vtkRectilinearGrid?)
but am not sure what is most suited for my task.  

I have the XYZ coords of each electrodes obtained from the CT data,
and now must assign points to the right data structure, to facilitate
tasks like getting the nearest neighbors of a given electrode,
defining a normal vector to the grid at a given electrode in such a
way that all the normals of all the electrodes point (loosely) the
same direction, ie, all point into the brain or all point away.

Advice or examples welcome,
John Hunter