Proposal to Improve Kinematic Estimation Algorithm of Knee Prosthesis

Abstract

We will propose two innovative techniques for estimating 3D motion of the knee prosthesis from its 2D perspective projections such as X-ray images. One of our proposing techniques is a two-step estimation algorithm and the other is a way to solve overlapping problem. In our two-step estimation algorithm, the first step estimation was done, in the same way as Banks and Hodge's on the assumption of orthogonal projection. Then, the second step estimation was succeeded based upon the perspective projection to accomplish more accurate estimation. The other is a novel method to solve such a problem as our algorithm did not function when the silhouettes of tibio and femoral components overlapped with each other. Here the estimation was processed in two steps in associate with the above-mentioned two-step estimation. First, the missing part of silhouette contour due to overlap was interpolated using free-formed curvatures. In the next step, a clipping window was set in the projective coordinate so as to separate the overlapped silhouette. Simulation results demonstrated that our two-step estimation algorithm improved accuracies much, and also sufficient accuracies could be assured even for the overlapped silhouettes; equivalent to those without overlap.

Using Bezier curves in medical applications

“…In many applications of medical physics, biomedical engineering, and Computer Aided Design (CAD), an object is often known by a sequence of 2D cross sections (slices) (cf. [9], [8], [6], [13]; see also the references cited in each of these earlier works). These slices can be obtained using several imaging techniques such as Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Single Photon Emission Tomography (SPECT), and Positron Emission Tomography (PET).…”