Floyd’s contribution to B/A measurement of biological materials

Ultrasound as used for medical diagnosis and high‐intensity therapy is of sufficient amplitude that the effects of nonlinear propagation are important. Critical to modeling and understanding these nonlinear effects is knowledge of the nonlinearity parameter, B/A, for the biological tissues involved. In a series of papers Floyd Dunn and colleagues determined the value of B/A for several biological materials and soft tissues using the thermodynamic and finite amplitude methods. They showed that the B/A value depended directly upon the solute concentration in protein solutions. The value of B/A was around 7 for many soft tissues, including liver, muscle, and brain, but was around 11 for fat. Homogenized liver had a value that was less than that for whole liver, demonstrating an effect of structure. These results provided information regarding the range of B/A for biological materials and its dependence on concentration and structure and suggested the possible use of B/A in tissue characterization.