Simbios Talk by Sunil Puria, Stanford University, November 29, 2005

Title: Integrating Middle-ear Imaging, Physiology, and Biomechanics

Our overall goal is to understand the relationship between human middle ear morphometry, tailored to individual ears, and the biomechanical processes that lead to physiological responses for normal and pathological conditions. The rational behind this effort is that a lack of knowledge about the relationship between middle ear structures and sound transmission has resulted in unsatisfactory and variable success of middle ear repairs. Our approach is to deconstruct the middle ear into three sub systems that are each characterized through a combination of morphological and physiological measurements as well as three-dimensional mathematical analyses. The sub systems are mathematically reconstructed for comprehensive analyses representing the intact middle ear. The sub systems are: (1) the tympanic membrane coupled to the ear canal, (2) the isolated malleus-incus complex, and (3) the isolated stapes footplate. For each sub system and for the intact middle ear, high resolution microCT images are used to image individual temporal bone ears. The microCT images are segmented and combined to obtain three-dimensional volume reconstructions of the ear canal, eardrum, ossicles, ligaments and tendons, which are further analyzed to obtain the desired morphometry. Biomechanical parameters of the sub models are determined from dynamical measurements. To characterize the tympanic membrane, a computational model was developed incorporating anatomical features of the eardrum, including its angular placement in the ear canal, conical shape and its highly organized circumferential and radial collagen fiber layers. To characterize the malleus-incus complex, isolated by dissecting the eardrum and the stapes from the temporal bone, three-dimensional velocity at several points are measured and an elastic model developed. Measurements of forward and reverse acoustic measurements, before the de-construction, used to test the validity of the analyses developed will be described. The studies provide a foundation for the structural basis for middle ear sound transmission and will have applications in many areas of hearing health care including surgical reconstruction as well as evaluation and development of new passive and active prostheses.