6533b7d3fe1ef96bd1260bfe

RESEARCH PRODUCT

Obstructing propagation of interfering modes improves detection of guided waves in coated bone models

subject

description

Interference due to wave propagation in soft tissue that covers the bone is a major challenge to in vivo assessment of the fundamental flexural guided wave (FFGW) in bone. To improve signal-to-interference ratio (SIR) we propose to obstruct the propagation of interfering modes by locally deforming the coating by external mechanical compression. This approach was modeled by 2D finite-element transient domain (FEMTD) simulations in a fluid-coated (7 mm) solid plate (3 mm). The fluid layer mimics the soft tissue that covers the bone. A single emitter or a 6-element phased array excited ultrasound pulses at 50 kHz on the surface of the coating, and a receiver array was placed on the surface, 20–50 mm apart from the last emitter. Localized deformation of the coating was modeled by a sine-shaped notch (7 mm half-width and 0–7 mm depth), centered between the emitting and receiving array. The deformation of the coating increased the SIR of FFGW by 20.3 ± 2.3 dB. A 50% deformation of the coating thickness was effective and only a small improvement in SIR was achieved by further compression. Combining a 50% deformation of the soft coating with phased excitation resulted in a 31.4 ± 2.6 dB SIR gain, and revealed a distinct FFGW wave packet. It was impossible to distinguish FFGW from the interference by a conventional measurement. These results thus suggest that obstructing the propagation of interfering modes may improve the detection of FFGW in in vivo measurements.