Optical techniques for real-time morphology measurement of the tympanic membrane
28 May 2015
UAntwerp, Campus Middelheim, A.143 - Middelheimlaan 1 - 2020 Antwerp
Sam Van der Jeught
Joris Dirckx - Jan Sijbers
PhD defence Sam Van der Jeught - Faculty of Science, Department of Physics
The eardrum or tympanic membrane is the first component in the complicated mechanical system of the middle ear. To fully understand the functioning of the human hearing organ, and to optimize ossicular prostheses and middle ear implants, highly realistic computer models of the middle ear system are being developed. As an input for such models, accurate geometric data of the eardrum are needed, and one important missing piece of data is the thickness distribution of the membrane.
On the other hand, the outcome of computer models of the middle ear needs to be validated with experimental measurements. The ear transports sound energy whilst dealing with large quasi-static pressure variations. Therefore, models need to be validated in this low-frequency high-pressure regime, especially since these large displacements form a particular problem in middle ear prosthesis design.
Much research on in-vitro samples has already been performed in this area, but until now a technique to measure full-field deformation of human eardrum has been missing. In addition to the gathering of data as input to middle ear models, in-vivo measurement of three-dimensional eardrum deformation opens the possibility for new diagnostic techniques, allowing the detection of weak spots in the eardrum before they manifest into chronic middle ear disease and the evaluation of middle ear pressure regulation by quantifying eardrum displacement.
The thesis starts out with a contribution to the generation of modelling data. Optical coherence tomography is used to generate full-field thickness maps of the eardrum, and for this purpose a very fast technique for distortion artifact correction is presented. Next, a new method is proposed to measure eardrum deformation in-vivo and in real-time by combining structured light profilometry with the stereoscopic design configuration of an ENT operation microscope.
Parallel programming techniques are developed to perform shape and deformation measurement in real-time, including and a new high-speed phase unwrapping algorithm. Finally, a method for real-time correction of geometric lens distortion artifacts is presented, opening the possibility for future implementation of the fast profilometry method in surgical endoscopes.