A method for three-dimensional displacement and deformation measurement applied to the statically loaded middle ear ossicles

摘要

The middle ear ossicles transmit sound from eardrum to inner ear under largely varying ambient pressure conditions. To protect the structures within the cochlea from excessive footplate incursions the configuration of the ossicles changes with pressure. Sequences of micro CT-scans were acquired from gerbil temporal bones under static ear canal pressures ranging from -450 to +450 daPa. These image stacks were used to track the 3D motion and deformations of the ossicles as a function of pressure using hyperelastic warping [1]. Using the scans for zero pressure, accurate finite-element reference models were generated for each of the ossicles. With the difference between these template images and the target image data recorded in a deformed configuration as a driving force, the warping algorithm displaced and deformed the finite-element models of the ossicles in order to align the deformed template with the target data. Position changes of the ossicles within the middle ear cavity and deformation of the ossicles and the tympanic membrane were all measured in a same preparation. For each static pressure load a finite-element ossicular chain model is obtained in the run and can be used for further analysis under acoustic stimulation.