Mechanical Characterization of Cranial Sutures Using Guided Ultrasonic Waves

The work focuses on the non-invasive mechanical characterization of the coronal suture of a dry human skull using cranial Lamb waves. Specifically, the suture is idealized as an elastic interface formed by a set of distributed compression and shear coefficients. These are estimated from an optimization problem that leverages the transmission coefficients of the fundamental symmetric and antisymmetric Lamb modes. The transmission coefficients are measured experimentally in the 90-110 kHz range using infrared laser vibrometry, and computed numerically by means of a semi-analytical finite element model of the cranial bone generated from CT images. The obtained results indicate that the equivalent elastic shear coefficients are typically larger than the compression ones, resulting in better transmissibility of shear-like modes. The obtained results demonstrate that cranial guided waves can be used to define simple constitutive laws for cranial sutures, which enable the study of the energy transmission across the cranial vault and the construction of high-fidelity models of the human skull.