Laser Doppler velocimeter measurement of acoustically and magnetically driven middle ear ossicles
Faculty of Sciences. Physics
OPTICAL MEASUREMENT TECHNIQUES FOR STRUCTURES & SYSTEMS2 (OPTIMESS2012)
5th International Conference on Optical Measurement Techniques for, Structures and Systems2 (OPTIMESS), APR 04-05, 2012, Antwerp, BELGIUM
, p. 311-317
University of Antwerp
Chronic inflammation of the middle ear is a common disease in which, amongst other structural changes, the mobility of the middle ear ossicles may be reduced. This causes hearing impairment. In an advanced stage of disease the surgeon can manually assess that an ossicle is fully fixated and then replace it with prosthesis in order to regain hearing with a known chance of success. However, in a less advanced case with only partial fixation it may be difficult to judge the degree of hearing impairment, and therefore difficult to decide the best choice of treatment. Vibration of the ossicles can be measured using a laser heterodyne vibrometer, but in order to expose the vibrating bones for access by the vibrometer beam the eardrum needs to be removed. Once the eardrum is lifted it obviously cannot deliver acoustic input energy to the ear. We therefore devised a new technique in which motion of the eardrum is first measured using acoustic input. Next, the eardrum is removed and a tiny magnet is attached to the manubrium ( the part of the first auditory ossicle, which is normally attached to the eardrum). An electromagnetic excitation coil is then used to make the magnet vibrate, and the input signal is adjusted so that the manubrium vibrates in the same way as before, as measured with the vibrometer. In this way the ossicular chain receives the same input as in acoustic stimulation. The vibrometer can then be used to measure the vibration response at several different positions along the ossicular chain, and this response used to compare diseased and normal ears. In the current paper we will explain the method and first results obtained on temporal bones with artificially fixated ossicles.