Optical coherence elastography for shear wave characterization under temporal undersampling

We present an optical coherence elastography approach for Rayleigh surface wave measurement with a MHz swept-source optical coherence tomography (OCT) system, enabling high-frequency wave characterization under temporal undersampling. Mechanically induced waves in a tissue-mimicking phantom were captured below the conventional temporal Nyquist sampling condition, while wave propagation was recovered from the spatial structure of the measured displacement field and analyzed using spatial Fourier-domain processing. With 6 μm lateral sampling and 0.4 ms frame intervals (2.44 kHz B-scan rate), at a representative depth of 0.5 mm, the measured mean Rayleigh-wave speed was 13.61 m/s, with a frame-to-frame standard deviation of 0.73 m/s across 1000 frames. The results were compared with a second wave speed estimation method based on phase-gradient analysis and further validated using laser Doppler vibrometry (LDV), showing agreement in estimated wave speeds between OCT and LDV within 7.75%.