ADAPTIVE CANCELLATION OF MUSCLE-CONTRACTION INTERFERENCE IN VIBROARTHROGRAPHIC SIGNALS

Vibroarthrography (VAG) is an innovative, objective, non-invasive tech nique for obtaining diagnostic information concerning the articular ca rtilage of a joint. Knee VAG signals can be detected using a contact s ensor over the skin surface of the knee joint during knee movement suc h as flexion and/or extension. These measured signals, however, contai n significant interference caused by muscle contraction that is requir ed for knee movement. Quality improvement of VAG signals is an importa nt subject, and crucial in computer-aided diagnosis of cartilage patho logy. While simple frequency domain high-pass (or band-pass) filtering could be used for minimizing muscle contraction interference (MCI), i t could eliminate possible overlapping spectral components of the VAG signals. In this work, an adaptive MCI cancellation technique is prese nted as an alternative technique for filtering VAG signals. Methods of measuring the VAG and reference signals (MCI) are described, with det ails on MCI identification, characterization, and step size optimizati on for the adaptive filter. The performance of the method is evaluated by simulated signals as well as signals obtained from human subjects under isotonic contraction.