Biphasic models of soft tissues for ultrasound applications

A theoretical model for describing ultrasound propagation in soft tissue modeled as a solid-fluid aggregate is described. The biphasic theory developed by Mow and coworkers can explain correctly the flow and deformation of soft hydrated tissues under a variety of conditions. It is shown here that the biphasic theory can be derived from Biot's theory of porous elastic materials saturated with fluid when both phases the solid phase and fluid phase are considered intrinsically incompressible. The biphasic theory is then extended to include ultrasound propagation. This extension follows very closely Biot's work. The proposed model, if confirmed experimentally, could be a powerful phenomenological tool to plan and interpret data of ultrasound propagation in soft tissues.