Multi-Frequency Reverberant Shear Waves for Assessing Tissue Dispersion in Optical Coherence Elastography

Abstract: Optical coherence elastography (OCE) is a powerful non-invasive imaging technique for high-resolution assessment of tissue elasticity and viscoelasticity. Accurate characterization of viscoelastic properties requires estimating shear wave speed (SWS) across multiple frequencies, as dispersion induces frequency-dependent variations in wave speed. This study introduces a novel multi-frequency reverberant OCE (MFR-OCE) approach to enhance viscoelastic tissue characterization by simultaneously capturing shear wave dynamics over multiple frequencies. We present the theoretical framework, experimental setup, and validation of MFR-OCE through simulations and experiments on gelatin phantoms, ex vivo porcine cornea, and ex vivo bovine liver. Simulation results demonstrate that MFR-OCE estimates SWS with errors below 4% relative to ground truth, and phantom experimental results show that MFR-OCE and single-frequency OCE also yield closely matching SWS estimates, with differences below 3%. Furthermore, the frequency-dependent dispersion coefficients extracted from biological tissues and phantoms align with the theoretical viscoelastic power law model. The gelatin phantoms exhibit a low viscoelastic behavior with an exponent of 0.13 for the power law fit of SWS, while the ex vivo porcine cornea demonstrates intermediate viscoelastic behavior, with a power law exponent of 0.33. The liver tissue shows significant frequency dependence, with a power law exponent of 0.51. These findings demonstrate that MFR-OCE enables a more comprehensive understanding of tissue mechanics and holds the potential for improving diagnostic accuracy in clinical applications.