Site-Specific Diagnostic Evaluation of Hard Biological Tissues Using Solitary Waves

We perform site-specific diagnostic evaluation of hard biological tissues via highly nonlinear solitary waves. Solitary waves are compact-supported tunable pulses with extremely high energy density, which can be efficiently formed in a chain of ordered granular particles defined as 1D granular crystals. We transmit a single pulse of solitary waves into specific areas of artificial biological systems via direct mechanical contact with a granular crystal sensor. We then record the solitary waves backscattered from a targeted bone area to assess its mechanical stiffness. By taking advantage of the coupling between nonlinear granular media and biological systems, we demonstrate that reflected solitary waves are highly sensitive to site-specific mechanical properties of hard biological tissues. The efficacy of the diagnostic approach is investigated by comparing the stiffness measurements with nominal elastic moduli of polyurethane foams that mimic osteoporotic bone. We also perform numerical investigations via a discrete element (DE) model, simulating propagation and attenuation of solitary waves at the interfaces. The site-specific evaluation technique via solitary waves has the potential for clinical applications, such as assisting appropriate intraoperative decision during joint replacement or spinal surgery for better surgical outcome.