Feature Of The Week 6/17/12: Middle Ear Vibrometry of Human Cadaver Temporal Bone with Spectral Domain Phase-Sensitive Optical Coherence Tomography
Hearing loss is the most frequent sensory deficit in the human population, affecting more than 250 million people in the world. The National Center for Health Statistics estimates that 37 million adults (17%) in the United States have hearing difficulty. Analysis of a large database of audiometric records from the University of Minnesota reveals that 39% of patients diagnosed with hearing loss have conductive hearing loss (CHL) either alone (15%) or in combination with SNHL (24%).
There are several contemporary audiological tests that are commonly used to diagnose middle ear function for CHL. However, these contemporary tests of middle ear function do not provide the vibration of the ossicles behind an intact tympanic membrane (TM). For example, audiometry can identify an air-bone gap in hearing thresholds, the hallmark of CHL, but not the cause of the hearing loss. Tympanometry can measure the compliance of the whole eardrum and middle ear complex but does not provide specific information about the ossicular chain. A normal tympanogram does not rule out an ossicular problem, and an abnormal tympanogram does not rule it in. Laser-Doppler vibrometry (LDV) has been widely used to investigate middle ear function in animals and human temporal bones with the sound-induced motion of the TM. Although the direct measurement of TM mobility can be measured with LDV, and it seems to be a natural tool for investigating CHL, but it can’t provide direct vibration measurement of the ossicular chain through the intact TM. Moreover, it is not clear that this technology would be successful in identifying the causes of CHL when the eardrum or the ossicular chain has been altered, such as in patients who have had surgeries for chronic otitis media or cholesteatoma.
Although the feasibility of OCT has been demonstrated to image the morphology of human middle ear and TM, the use of optical coherence tomography (OCT) for middle vibrometry in humans has not previously been reported. In this study, we report a novel application of spectral domain phase-sensitive optical coherence tomography (SD PS-OCT) to measure vibrations of middle ear (ME) structures such as the TM and ossicular chain with high sensitivity though the intact TM. The technique is based on SD PS-OCT to produce a depth resolved vibration map by using Fourier transform (FT) analysis of the measured phase changes in the spectral interferograms induced by the acoustic stimulation of ME structures. In this study, we present, as an initial demonstration, the application of SD PS-OCT to 2-D cross-sectional vibration imaging of normal and abnormal human cadaver temporal bone.
For more information see recent Article. Courtesy of Hrebesh Subhash from the Oregon Health & Science University.