Fig. 6.

Deformation fields showing correspondences defined in different ways in a ribbon shaped phantom with no noise. A 2D slice is shown here with the gray levels representing WM (light gray) and GM (gray). Color represents norm of the deformation field which is the estimated thickness. (a) Closest point-based correspondence. Notice that some correspondence lines do not seem to map to GM boundary points since many of them point to boundary locations at a different slice in 3D. (b) Radial direction based correspondence – by construction, deformation norms are tightly clustered around 3 mm –the variation around the theoretical value is only due to discretization. (c) Correspondence based on Diffeomorphic mapping – this captures the visible variation in thickness along the surface.