Evaluation of the nonlinear modulus in renal transplant patients using progressive and regressive compression and shear wave measurements

End-stage renal disease (ESRD) is an irreversible deterioration in the renal function in which the body loses its ability to maintain the fluid and metabolic balance. Transplantation is the treatment of choice for patients with ESRD. After transplantation, biopsies are performed to monitor the function of the kidney transplant over time. Due to the invasive nature of biopsies, we are investigating the potential of noninvasive shear wave based methods such as acoustoelasticity (AE) to estimate the nonlinear mechanical properties of tissues. Using AE by compressing a medium and measuring the shear wave speed at different compression levels, we can estimate the third order nonlinear coefficient, A. The goal of this study was to evaluate the feasibility of performing AE using two directions of compression and to evaluate the potential of A as an indicator of the presence of renal fibrosis in the transplanted kidney.