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Finite element simulation of ultrasound propagation in bone for quantitative ultrasound toward the diagnosis of osteoporosis

Osteoporosis is a serious bone disease which leads to the increased risk of bone fractures. For prevention and therapy, early detection of osteoporosis is critical. In general, for diagnosis of osteoporosis, dual-energy X-ray absoptiometry (DXA) or densitometry is most commonly used. However DXA exhibits some disadvantages such as ionizing radiation, relatively expensive cost, and limited information on mineralization and geometry of the bone. As an alternative method of DXA, quantitative ultrasound (QUS) is being investigated. In contrast to DXA, QUS is non-ionizing and relatively inexpensive. It can also provide some bone-related parameters (e.g., quantitative measurements including speed of sound and frequency-dependent attenuation). However the estimation of these parameters is difficult and few analytical solutions exist due to the complex behavior of ultrasound propagation in bone. As an alternative to the analytical methods, in most attempts, finite difference time domain (FDTD) method is used for simulation of ultrasound propagation in bone with a limited capability of modeling complex geometries of the bone. Finite element method (FEM) is a better solution since it can handle the complex geometry, but has been rarely applied due to its computational complexity. In this work, we propose an approach of FEM-based simulation of ultrasound propagation in bone. To validate our approach, we have tested simulated and real bone models from micro-CT using the index of speed-of-sound. Our results achieve an average of 97.54% in the computational accuracy.