Planar deformable motion estimation incorporating mass conservation and image gradient constancy

The accuracy of optical flow estimation algorithms has been improving steadily by refining the objective function which should be optimized. A novel energy function for computing 2-D optical flow from X-ray CT images is presented. One advantage of the optical flow framework is the possibility to enforce physical constraints on the numerical solutions. The physical constraints which have been included here are: brightness constancy, gradient constancy, continuity equation based on mass conservation, and discontinuity-preserving spatio-temporal smoothness. Both qualitative and quantitative evaluation of the proposed method demonstrates that the method results in significantly better angular errors than previous optical flow techniques for estimation of deformable lung motion. Future research will include extension of the proposed techniques to 3-D.