Modeling of Ultrasonic Wave Propagation Path through Cancellous Bone and Quantitative Estimation of Bone Density and Bone Quality

Abstract

Osteoporosis is a disease characterized by decreasing bone density, and is assessed by the bone mass density of cancellous bone. An X-ray method is widely used for noninvasive measurement of bone mass density [mg/cm3]. An ultrasonic method has the potential to evaluate the elastic properties, however measured ultrasonic parameters are the slope of frequency dependent attenuation (BUA [dB/MHz]) and the speed of sound (SOS [m/s]), not the bone mass density [mg/cm3]. In previous study, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. In this study, the propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated. A novel ultrasonic bone densitometry, prototype LD-100, have been developed. The bone density [mg/cm3] and the bone elasticity [GPa] are evaluated by ultrasonic parameters based on the fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path.