Ultrasonic backscatter signals from the cancellous bone can be used to diagnose osteoporosis effectively due to its ability to provide the information of bone microstructure. Mean trabecular bone spacing （MTBS） is one of the important parameters for characteriza- tion of bone microstructure. This paper proposed a MTBS estimating method based on the fundamental frequency estimation, which was applied to backscatter signals from simulations, and in vitro bovine trabeculae. The estimated MTBS were compared with those of simplified inverse filter tracking （SIFT） algorithm and autoregressive （AR） cepstrum method. The results demonstrated that the proposed method is very robust for the MTBS estimation with more precise estimates and smaller estimated variance in the presence of a small signal-to-noise ratio （SNR）, and a large scattering strength ratio of diffuse scatterers to regular ones.
Assessment of fractured long bone using ultrasonic guided wave（GW） has gained considerable attention.This paper focuses on using the hybrid boundary element method （HBEM） to analyze the propagation characteristics of ultrasonic GW in fractured long bones. The reflection coefficients（RC） and transmission coefficients（TC） for different depth-to-width ratio（d/w） cracks were numerically calculated and analyzed.It has been shown that the primary output modes,which include the transmission and reflection modes,are the same as the incidence modes.For some cracks,different TC curves always got the local maxima in adjacent frequencies.For different d/w cracks,most of the TC curves had local maxima which are not overlapped.These simulation results are helpful to optimize the modes and frequencies of the incidence GWs for quantitatively evaluating the bone quality and providing the numeral results of the cracks in long cortical bones.
The ultrasonic signals in long bones contain multiple guided modes which are mutual superposed.The velocities of guided waves in long bones are very sensitive to cortical thickness （CTh）.In this paper,Hilbert-Huang transform（HHT） was proposed to analyze multi-mode guided waves,which can decompose superposed waves into many independent modes.Then the group velocity of each mode was obtained at corresponding frequency,which was compared with the results of short time Fourier transform（STFT）.The CTh was also obtained by comparing with the theoretical calculation.The results showed that the experimental determined thickness was in agreement with the actual CTh,indicating that measuring the velocity of the guided mode can be used to estimate the CTh.The HHT is an effective method to identify multimode guided waves.
