Experimental identification of high order Lamb waves and estimation of the mechanical properties of a dry human skull

• Published in: Ultrasonics 2021-05, Vol.113, p.106343-106343, Article 106343
• Main Authors: Mazzotti, Matteo, Sugino, Christopher, Kohtanen, Eetu, Erturk, Alper, Ruzzene, Massimo
• Format: Article
• Language: English
• Subjects: Biomechanical Phenomena; Cranial Lamb waves; Dispersion; Finite Element Analysis; Human skull; Humans; In Vitro Techniques; Male; Orthotropicity; Parametric identification; Semi-analytical finite element method; Skull - physiology; Ultrasonics - methods
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2020.106343

[Display omitted] •Lamb waves are experimentally investigated and characterized in a dry human skull.•High order Lamb wave modes are observed in a parietal region below 800 kHz.•The diploë supports modes with multiple through-thickness wavelengths.•The cortical bone behaves as a transversely isotropic material. We experimentally investigate and characterize high order Lamb wave modes in a dry human skull. Specifically, we show that the diploë supports distinct wave modes in the sub-1.0 MHz frequency regime, and we employ these modes for the estimation of equivalent mechanical properties of cortical and trabecular bones. These modes are efficiently generated in a parietal region by direct contact excitation with a wedge beam transducer, and are recorded via infrared laser vibrometry. Frequency/wavenumber data are estimated using a matrix pencil method applied to wavefield measurements recorded on the outer cortical surface. The semi-analytical finite element model of an equivalent three-layered plate provides the platform for the identification of wave modes based on their through-the-thickness profiles, and supports the estimation of equivalent mechanical properties in conjunction with an optimization algorithm developed for this purpose. The results presented herein illustrate how high order Lamb waves can be used to gain understanding of the wave properties of a human skull and to estimate the orthotropic and equivalent isotropic mechanical properties of cortical and trabecular bones.