title: 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 degrees 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 degrees C. Both these parameters increase at an average rate of 0.026 degrees C and 1.5 m/s/degrees C, respectively, as the temperature is raised from 20 to 37 degrees 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.
mesh_terms: D001823:Body Composition; D002784:Cholesterol / Q000032:analysis; D006801:Humans; D008055:Lipids / Q000032:analysis*; D008099:Liver / Q000032:analysis*; D010743:Phospholipids / Q000032:analysis; D013696:Temperature; D014280:Triglycerides / Q000032:analysis; D014465:Ultrasonics; D014867:Water / Q000032:analysis*
chemical_list: D008055:Lipids; D010743:Phospholipids; D014280:Triglycerides; D014867:Water; D002784:Cholesterol