Functional optical coherence tomography for imaging middle ear dynamics

No currently available clinical technique is capable of visualizing and quantifying the structure and function of the middle ear. Various pathologies directly impede the conduction of sound-induced vibrations through the human middle ear, and thereby produce a `conductive' hearing loss. Direct clinical assessment of sound conduction by middle ear structures has been limited to measurements of the average sound-induced vibration of the eardrum or the motion of single locations on the drum. In contrast, the optical coherence tomography (OCT) technology we introduce allows direct observation of the structure and sound-induced motions of a large fraction of the eardrum surface as well the ossicles within the ear. We use OCT to take three-dimensional volumetric snapshots of the moving eardrum and the ossicular chain behind the eardrum in a cadaveric chinchilla with which can generate 3D amplitude and phase maps. Our functional OCT technique can accurately image middle ear structures with a resolution of 10-20 microns and measure ossicular movements with sub-nanometer scale resolution with a temporal resolution of 50 microseconds.