MR image coding using content-based mesh and context

Existing schemes for 3-D magnetic resonance (MR) images, such as block matching method and uniform mesh-based scheme, are inadequate to model the motion field of MR sequence because deformation within a mesh element may not all be similar. We propose a scheme consisting of (a) content-based mesh generation using optic flow between two consecutive images (b) forward motion tracking (c) motion compensation using affine transformation and (d) context-based modeling. We also propose a simple scheme to overcome aperture problem at edges where an accurate estimation of motion vectors is not possible. By using context-based modeling, motion compensation yields a better estimate of the next frame and hence a lower entropy of the residue. The obtained average compression ratio of 4.3 is better than the values of 4, achieved by CALIC, and 3, by the existing uniform mesh-based interframe coding scheme.