Nonlinear inversion of ultrasonic guided waves for in vivo evaluation of cortical bone properties

Abstract

Ultrasonic guided waves (UGW), which propagate throughout the whole thickness of cortical bone, are attractive in the early diagnosis of osteoporosis. However, it is challenging due to the impact of soft tissue and the inherent difficulties related to the multiparametric inversion of cortical bone quality factors, such as cortical thickness and bulk wave velocities. Therefore, an UGW based multiple-parameter inversion algorithm is developed to predict strength-related factors in this research. In simulation, a free plate (cortical bone) and a bilayer plate (soft tissue and cortical bone) are used to validate the proposed method. The inverted cortical thickness (CTh), longitudinal velocity (V L ) and transverse velocity (V T ) are in accordance with the true value. Then four bovine cortical bone plates are used in the in vitro experiments. Compared with the reference values, the relative errors for cortical thicknesses are 3.96%, 0.83%, 2.87% and 4.25% respectively. In the in vivo measurements, ultrasonic guided waves are collected from ten volunteers’ tibia. The theoretical dispersion curves depicted by the estimated parameters (V T , V L , CTh) match well with the extracted experimental ones. In comparison to the dual-energy x-ray absorptiometry (DXA), the results show that the estimated transverse velocity and cortical thickness are highly sensitive to the osteoporosis. Therefore, these two parameters (CTh and V T ) of long bones have potential to diagnose bone status in clinical applications.

A New Model of Ultrasonic Guided Wave Propagation in Blood Vessels and Its Propagation Characteristics

“…As an indispensable clinical tool, ultrasound examination has the advantages of non-invasion and non-radiation and is widely used in various medical tests [1,2]. In this method, specific kinds of ultrasonic waves are artificially stimulated, and the mechanical properties of human tissues are obtained by analyzing various reflection and transmission phenomena in the human body to assist in medical diagnosis [3,4]. In 1998, Sarvazyan et al [5] first proposed the shear wave elastography (SWE) method, and the echo wave of the shear wave that is induced remotely by the focused ultrasonic beam radiation force is analyzed in detail to obtain the elastic modulus of the internal organs more precisely.…”