Frequency-dependent assessment of eardrum lesions using multisine OCT vibrometry

Optical coherence tomography (OCT) vibrometry is a promising tool for middle-ear mechanics, but single-frequency approaches limit efficiency and diagnostic power. We introduce multisine OCT vibrometry in a rabbit model to capture broadband, frequency-dependent eardrum vibrations acquired in a single OCT volume. Multisine data revealed that control ears had maximal umbo displacement at 1.4 kHz with an amplitude of 86 ± 11 nm (N=5). Proof-of-concept measurements were performed to highlight the diagnostic value of detecting pathology related shifts in umbo displacement using multisines. Local thinning of the eardrum by ablation decreased the frequency of maximal displacement to 1.0 kHz and resulted in an umbo displacement of 84 ± 4 nm. In contrast, perforation of the eardrum caused an overall drop in displacement amplitude across frequencies, with a maximal displacement of 34 ± 3 nm reached at 2 kHz. Additionally, the single multisine OCT volume allowed visualization of the eardrum's displacement across the surface for all multisine tones. Ablation and perforations caused localized changes of the eardrum's displacement at frequencies above 4 kHz. Thus, multisine OCT vibrometry holds promise for improved diagnosis and surgical planning: umbo frequency-displacement curves can distinguish between healthy and pathological ears, while spatial displacement maps reveal lesion-specific displacement patterns at high frequencies.