Guo Xiasheng, Zhang Dong, Yang Di, Gong Xiufen, Wu Junru
Institute of Acoustics, Key Laboratory of Modern Acoustics (Nanjing University), Ministry of Education, Nanjing University, Nanjing 210093, China.
J Acoust Soc Am. 2008 Jun;123(6):4047-50. doi: 10.1121/1.2904929.
Protopappas et al. performed finite element (FE) studies on the propagation of guided ultrasound waves in intact and healing long bones, and found that the dispersion of guided modes was significantly influenced by the irregularity and anisotropy of the bone. A time-frequency (t-f) method was applied to the obtained signals and several wave modes were identified. However, this technique was unable to quantify their observations and provide monitoring capabilities. One possible reason of this shortcoming may come from the inherent disadvantage of the t-f method. The objective of this comment is to demonstrate that it is necessary to combine other techniques with FE simulations for the extraction of significant quantitative ultrasonic features. Individual guided modes in an isotropic pipe have been theoretically examined using the normal mode expansion (NME) method, and many modes that are missed by the t-f analysis have been identified. It is concluded that in order to extract quantitative ultrasonic features, FE simulations should be supplemented by other techniques such as the NME.
普罗托帕帕斯等人对完整和正在愈合的长骨中导波的传播进行了有限元（FE）研究，发现导模的色散受骨骼的不规则性和各向异性的显著影响。将时频（t-f）方法应用于所获得的信号，并识别出几种波模。然而，该技术无法对其观测结果进行量化并提供监测能力。这一缺点的一个可能原因可能来自于t-f方法的固有缺陷。本评论的目的是证明有必要将其他技术与有限元模拟相结合，以提取重要的定量超声特征。使用简正模展开（NME）方法从理论上研究了各向同性管道中的各个导模，并识别出了许多被t-f分析遗漏的模式。得出的结论是，为了提取定量超声特征，有限元模拟应辅以诸如NME等其他技术。
