Monitoring presbyopia treatment with ultrasonic cavitation using shear wave elastography (SWE): Experiments and simulations

This numerical study aims at evaluating quantitative monitoring of elasticity changes induced by ultrasonic cavitation using shear waves elastography (SWE). SWE is a good method to safely evaluate the lens stiffness. Yet, the absence of backscattered signal inside the lens (regardless of the imaging technique) forbids elastography inside. Experimentally, we, thus, tracked surfaces waves on multiple models (gelatin beads, porcine lens) and evaluated dispersion curves of this waves. Finite difference time domain simulations are performed in order to evaluate elasticity with access to a few surface point, starting with a simple homogeneous inclusion towards complex inclusion closer to the lens configuration. In homogeneous inclusion, we noticed Scholte wave behavior on the dispersion. Complexifying the configuration by adding layers induced a gradient in the dispersion curves, the higher the frequency is the less the surface wave depends on the deepest layers. A similar behavior was observed experimentally: low frequencies with mostly resonances then a plateau matching Scholte wave expectation. Numerical studies indicate that the surface waves is sensitive to the shear elasticity inside the inclusion, yet this behavior is highly frequency dependent. This leads the way to investigate the frequency behavior of guided wave in experiments in lens in our team.