基于宽带相干信号子空间方法的超声导波长骨评价

Evaluation of long bone with ultrasound guided waves using wideband coherent signal subspace method

超声导波对长骨的生物力学特性敏感,已经广泛应用于长骨的健康评价。由于骨骼的高衰减特性,准确估计长骨中宽带相干导波信号的频散模式,进而准确反演长骨材料特征参数,是骨超声领域的一个研究热点和难点。本文提出了一种基于宽带相干信号子空间的导波波数估计方法,高精度提取导波频散模式;在此基础上,应用具有全局优化特性的蚁群算法从导波模式中估计长骨材料参数,成功实现了对长骨状况的定量评价。仿真和离体实验(2块仿真样本和2块离体牛骨)共同验证了方法的有效性,实验频散与参考频散之间的相对误差分别为3.52%,3.83%,3.35%,4.51%;对于离体牛骨,皮质骨厚度、纵波速度、横波速度估计值与参考值之间的平均相对误差分别为3.10%,0.11%,0.03%。综上,本文提出的方法为定量超声长骨评价提供了新的借鉴,也可应用于其他固体波导频散的高精度提取和结构健康表征。

Ultrasound guided waves are sensitive to the biomechanical properties of long bones,and have been widely used in the health evaluation of long bones.Due to the high attenuation characteristics of bones,accurate estimation of the dispersion pattern of broadband coherent guided wave signals in long bones,and then accurate inversion of the material characteristic parameters of long bones,is a research hotspot and difficulty in the field of bone ultrasound.In this paper,a guided wave number estimation method based on the subspace of broadband coherent signal is proposed to extract the guided wave dispersion pattern with high accuracy;on this basis,an ant colony algorithm with global optimization is applied to estimate the material parameters of the long bone from the guided wave pattern,and the quantitative evaluation of the condition of the long bone is successfully realized.Simulation and ex vivo experiments(2 simulated samples and 2 ex vivo bovine bones)jointly verified the validity of the method,and the relative errors between the experimental dispersion and the reference dispersion were 3.52%,3.83%,3.35%,and 4.51%,respectively;for the ex vivo bovine bones,the average relative errors between the estimated values of the cortical bone thickness,longitudinal wave velocity,and transverse wave velocity and the reference values were 3.10%,0.11%,and 0.03%.In conclusion,the method proposed in this paper provides a new reference for quantitative ultrasonic long bone evaluation,and can also be applied to other solid waveguide dispersion extraction and structural health characterization with high accuracy.