Sensitivity analysis of leaky Lamb modes to the thickness and material properties of cortical bone with soft tissue: A semi-analytical finite element based simulation study

Inversion of ultrasonic guided waves (UGW) for cortical bone properties is an important topic. The fundamental ultrasonic guided modes (UGM) are consistently observed in long bones in vitro and in vivo. The responses of UGM to the changes of cortical thickness, cortical elastic parameters, and thickness of the overlying soft tissues are not well understood. This study aims to investigate the sensitivity of leaky Lamb modes to the geometry and material characteristics of layered bone model by simulation. The analysis provides opportunity to study the responses of the UGM, to identify the sensitive regimes in the frequency-phase velocity domain, and to quantify the amount of sensitivity of each mode. The study is important as it offers guidance to the parameter inversion process about the optimal selection of UGM and regions of sensitivity for better inversion results.