Measuring Frequency Dependence of Articular Cartilage by Acoustic Vibration

Abstract

Recent years the number of patients that has articular cartilage disease is increasing. So it needs to make noncontact diagnostic method of articular cartilage for early diagnosis. By making clear mechanical properties of articular cartilage, diagnosing osteoarthritis can be expected before articular cartilage is worn away by rubbing. This paper describes the development of a new method for measuring viscoelastic properties of articular cartilage by acoustic excitation in low frequency range. Low frequency of 1～100Hz load is applied to the articular cartilage when human is walking or running. To evaluate articular cartilage’s mechanical function by using non-contact method is socially demanded for minimally invasive diagnosis. In this study articular cartilage’s complex shear modulus is obtained by measuring phase velocity and damping coefficient of surface wave on articular cartilage that is excited by acoustic vibration. In the acoustic excitation system, the vibration is generated by a wide range speaker and the surface wave displacements in two points are measured by two laser displacement sensors simultaneously. The system is constructed and the measurement experiment of articular cartilage is performed. Frequency of input acoustic vibration is 40~90Hz. The result shows steady-state vibration is excited at surface of articular cartilage. Therefore acoustic excitation is able to produce surface wave at arbitrarily frequency of articular cartilage.