Effect of cortical bone layer on piezoelectric signal generated in cancellous bone by ultrasound irradiation

The piezoelectric signals generated in cancellous bone by ultrasound irradiation were numerically simulated. To investigate the effect of cortical bone surrounding cancellous bone, the cancellous bone models attaching the cortical bone layers with various thicknesses were used. The piezoelectric signal waveforms in cancellous plus cortical bones were observed with the ultrasound signal waveforms through the bones. When the ultrasound wave was irradiated parallel to the major trabecular orientation, "fast and slow waves" could be observed in the ultrasound signals. The piezoelectric signals could be also divided into two waves. The former wave amplitude randomly varied with the cortical bone thickness, which could depend on the phase difference between the piezoelectric signals generated in cancellous and cortical bones. The later wave amplitude decreased, which could depend on the slow wave. As the cortical bone thickness increased, the piezoelectric effect in cortical bone became more dominant.