In vivo microstructural investigation of the human tympanic membrane by endoscopic polarization-sensitive optical coherence tomography

Abstract

. Significance Endoscopic optical coherence tomography (OCT) is of growing interest for in vivo diagnostics of the tympanic membrane (TM) and the middle ear but generally lacks a tissue-specific contrast. Aim To assess the collagen fiber layer within the in vivo TM, an endoscopic imaging method utilizing the polarization changes induced by the birefringent connective tissue was developed. Approach An endoscopic swept-source OCT setup was redesigned and extended by a polarization-diverse balanced detection unit. Polarization-sensitive OCT (PS-OCT) data were visualized by a differential Stokes-based processing and the derived local retardation. The left and right ears of a healthy volunteer were examined. Results Distinct retardation signals in the annulus region of the TM and near the umbo revealed the layered structure of the TM. Due to the TM’s conical shape and orientation in the ear canal, high incident angles onto the TM’s surface, and low thicknesses compared to the axial resolution limit of the system, other regions of the TM were more difficult to evaluate. Conclusions The use of endoscopic PS-OCT is feasible to differentiate birefringent and nonbirefringent tissue of the human TM in vivo . Further investigations on healthy as well as pathologically altered TMs are required to validate the diagnostic potential of this technique.

Depolarization for the assessment of caries in polarized light microscopy

“…Multiple intraoral OCT scanners on a prototype level have been presented that are applicable for the inspection of the occlusal surface [13,14]. As we have also shown that PS-OCT, e.g., by using a rigid endoscopic setup [15] is in vivo, these results support the way towards an in vivo caries diagnostics based on 3D depolarization imaging.…”

Morphologic analysis of the human tympanic membrane by polarization-sensitive OCT and polarized light microscopy

“…We have recently demonstrated that endoscopic PS-OCT enables the in vivo assessment of the human TM's connective tissue layer based on the retardation contrast. 4 However, we were not able to visualize those collagenrelated signals in all regions of the TM, which is partially explained by the measurement geometry when examining the healthy eardrum through the ear canal. Here, we investigate the existence and accessibility of collagen fibers across the entire TM by PS-OCT of an ex vivo temporal bone specimen and refer it to polarized light microscopic (PLM) images of thin sections, which were excised from the same specimen.…”

In Vivo Thickness of the Healthy Tympanic Membrane Determined by Optical Coherence Tomography

“…In combination with sound excitation, it is possible to detect vibrations of the ossicles (31) and to evaluate the coupling of middle ear prostheses after a middle ear reconstruction (32). Furthermore, an integration of polarization-sensitive OCT can enable the detection and thickness measurement of the distinct layers of the TM (22).…”

“…Although the distorted data are useful to determine the incident angle between beam and surface (see Fig. 4 by Steuer et al [22] for a visualization of the distorted and the corrected data), further calibrations are necessary for an accurate transformation from the spherical coordinate system of the fan-shaped measurement to the final Cartesian representation. Therefore, a 3D-printed calibration target with a plane millimeter grid was measured at the defined working distance of 10 mm.…”