Structural dependence of piezoelectric signal in cancellous bone at an ultrasound frequency

Abstract

Experimental observations of piezoelectric signals generated in bovine cancellous bone by an ultrasound wave were performed using two “piezoelectric cells (PE-cells)” of the bone, which could correspond to ultrasound receivers. In the PE-cells, air-saturated cancellous bone specimens with low (0.68 ± 0.02) and high (0.78 ± 0.02) porosities were used. An ultrasound burst wave at 1 MHz was transmitted toward each PE-cell, and the piezoelectric signals generated in the cancellous bone specimens were observed in nine regions of interest (ROIs). The piezoelectric sensitivities were derived with the structural parameters of cancellous bone: porosity, mean intercept lengths (MILs) of the trabecular elements in three orthogonal directions, and MILs of the pore spaces. The piezoelectric sensitivity tended to decrease with porosity. Moreover, the piezoelectric sensitivity in the whole porosity range was moderately correlated with both MILs, but the sensitivities in the low and high porosity ranges were correlated with only MILs of the pore spaces and only MILs of the trabecular elements, respectively. This was considered to be because the types (shapes) of the main trabecular elements in the low and high-porosity cancellous bone specimens were different. Thus, the piezoelectric sensitivity in cancellous bone could be affected by the trabecular structure.