3D thin-plate spline algorithm?

[Steve Hartmann <slh(at)vuse.vanderbilt.edu>]

I would like to register a 3D image volume to another volume based on a
set of corresponding points in each volume. This would be similar to
IDL's Warp_Tri function, only for 3D images and ideally using a
thin-plate spline interpolation method.

I thought I'd check if anyone had already done this (IDL, C, other)
before I started. Anyone have a 3D TPS algorithm or code available?

Thanks,
Steve Hartmann
Vanderbilt University