Motion Estimation in X-Ray Image Sequences with Bi-Distributed Transparency

This paper is concerned with motion estimation in transparent X-ray image sequences. Most of these medical images can be divided into areas containing at most two moving transparent layers. We will call it bi-distributed transparency. The first contribution of this paper is a motion estimation framework for the two-layer transparency case, able to handle noisy and low-contrasted X-ray image sequences. It involves three steps: block-matching, affine fit and gradient-based parametric estimation. This estimation scheme is then extended to the bi-distributed transparency case. The second step is now formulated as a joint motion segmentation-estimation problem solved by the iterative minimization of a MRF-based energy function. This framework has been applied to synthetic and real image sequences with quite satisfactory results.