@ARTICLE\{IMM2001-0254,
    author       = "P. R. Andresen and M. Nielsen",
    title        = "Non-rigid registration by geometry-constrained diffusion",
    year         = "2001",
    pages        = "81-88",
    journal      = "Medical Image Analysis",
    volume       = "5",
    editor       = "",
    number       = "2",
    publisher    = "",
    url          = "http://www.imm.dtu.dk/~pra/MedIA/",
    abstract     = "Assume that only partial knowledge about a non-rigid registration is
  given: certain points, curves, or surfaces in one {3D} image are known
  to map to certain points, curves, or surfaces in another {3D} image.
  In trying to identify the non-rigid
  registration field, we face a
  generalized aperture problem since along
  the curves and surfaces, \{\$\backslash\$em point\} correspondences are not given.
  We will advocate the viewpoint that the aperture and the {3D} 
  interpolation problem may be solved \{\$\backslash\$em simultaneously\} by finding
  the \{\$\backslash\$em simplest\} displacement field. This is obtained by a
  geometry-constrained diffusion, which in a precise sense yields the
  simplest displacement field. The point registration obtained may be
  used for segmentation, growth modeling, shape analysis, or kinematic
  interpolation.  The algorithm applies to geometrical objects of any
  dimensionality.  We may thus keep any number of fiducial points,
  curves, and/or surfaces fixed while finding the simplest
  registration. Examples of inferred point correspondences in a
  synthetic example and a longitudinal growth study of the
  human mandible are given."
}