Measurement and use of acoustic nonlinearity and sound speed to estimate composition of excised livers

Abstract The acoustic nonlinearity parameter B A and sound speed c have been determined for excised normal and abnormal human livers at 20–37°C. These values are compared with analytic measurements of fat and water content of tissues. The results show that normal liver containing 71.0% water and 2.9% fat by weight has a B A value of 6.75 and sound speed of 1592 m/s at 37°C. Both these parameters increase at an average rate of 0.026°C and 1.5m/s/°C, respectively, as the temperature is raised from 20 to 37°C. Fatty liver (24% fat by weight) exhibits highest B A (9.12) and lowest c (1522 m/s) of all the livers studied. In contrast to normal livers sound speed in such a liver was found to decrease with temperature. Based on the acoustic and composition measurements, quantitative correlations of B A and c with fat-water composition have been developed. Inversion of these relationships provide a simple method to determine composition of a tissue sample from B A and c measurements.