Extraction of the First-Arriving-Signal and Fundamental Flexural Guided Wave Using a Radon Transform Based Approach Applied to Ultrasonic Characterization of Cortical Bone

Ultrasonic guided waves have been used for characterizing cortical bone. However, multimode ultrasound signals bring difficulty in signal processing, making it challenging to extract the first arriving signals (FAS) and the individual mode components for cortical bone characterization. To overcome such a limitation, a feasibility study of cortical bone evaluation utilizing the Radon transform based signal extraction method is introduced in this paper. Forward and inverse Radon transform pair is applied to increase the signal-to-noise ratio of the ultrasonic signals collected from a bovine bone plate. Based on the known velocity ranges, the regions of interest in the intercept-slowness domain are extracted to obtain the FAS and the fundamental flexural guided wave (A0 mode) signals. Compared to the true geometric and elastic parameters, the proposed method enables to retrieve the cortical thickness, longitudinal and transverse velocities, which suggests a potential application of bone characterization.