Frequency-response analysis complements quantitative wave-speed assessment in optical coherence elastography

Wave-propagation optical coherence elastography (OCE) quantifies tissue mechanics, but its spatial specificity can decrease when the measurement scale (e.g., wavelength and spatial fitting range) approaches the size of tissue heterogeneities. Using dual-channel air-pulse OCE, we synchronously record excitation pressure and microscale displacement to derive input-normalized frequency-response functions (FRFs), dominant response frequencies, effective damping-ratio estimates, and spatial forced-response maps alongside group velocity. In agar phantoms and ex vivo porcine corneas, dominant response frequencies increased and effective damping-ratio estimates decreased with group velocity. In a silicone-inclusion phantom, the dominant-response FRF-magnitude map showed more pronounced inclusion contrast than the local group-velocity map. In a muscle-rotation experiment, group velocity followed fiber orientation, whereas selected off-resonant response maps revealed directional patterns not apparent in peak-derived parameters. Thus, spatial FRF-magnitude mapping complements quantitative wave-speed assessment with frequency-dependent spatial contrast.