Cortical Bone Properties Assessment Using Axially Transmitted Low Frequency (< 500 kHz) Ultrasonic Guided waves

The early diagnosis of osteoporosis through bone quality assessment has been extensively studied in the past decade. Research in axial transmission using ultrasonic guided waves has shown the method to be sensitive to intrinsic properties of long cortical bone. The aim of this work is to show the capability of low frequency guided waves to enable the inversion of dispersion curves into bone properties. The proposed model-based inversion scheme relies on dispersion curves simulated using the semi-analytical iso-geometric analysis (SAIGA) method. The numerical model comprised a bone phantom plate with a layer of soft tissue attached to the top surface in accordance with experimental bone phantom plates. A proprietary axial transmission multielement ultrasonic transducer specifically designed to excite ultrasonic guided waves around 500 kHz was used for measurements. Acquired data were processed using the 2D Fast Fourier Transform to extract the dispersion curves. The mechanical properties of the bone phantom plates were obtained by minimizing the difference between the experimental and simulated dispersion curves. The inversion was based on the dispersive properties of ultrasonic guided waves as well as their amplitudes. Results show a difference around 5% between the mechanical properties found with the SAIGA based inversion and pulse-echo measurements performed using bulk waves.