Full-Field Thickness Distribution of Human Tympanic Membrane Obtained with Optical Coherence Tomography

Abstract

The full-field thickness distribution, three-dimensional surface model and general morphological data of six human tympanic membranes are presented. Crosssectional images were taken perpendicular through the membranes using a high-resolution optical coherence tomography setup. Five normal membranes and one membrane containing a pathological site are included in this study. The thickness varies strongly across each membrane, and a great deal of interspecimen variability can be seen in the measurement results, though all membranes show similar features in their respective relative thickness distributions. Mean thickness values across the pars tensa ranged between 79 and 97 μm; all membranes were thinnest in the central region between umbo and annular ring (50-70 μm), and thickness increased steeply over a small distance to approximately 100-120 μm when moving from the central region either towards the peripheral rim of the pars tensa or towards the manubrium. Furthermore, a local thickening was noticed in the antero-inferior quadrant of the membranes, and a strong linear correlation was observed between inferior-posterior length and mean thickness of the membrane. These features were combined into a single three-dimensional model to form an averaged representation of the human tympanic membrane. 3D reconstruction of the pathological tympanic membrane shows a structural atrophy with retraction pocket in the inferior portion of the pars tensa. The change of form at the pathological site of the membrane corresponds well with the decreased thickness values that can be measured there.

In-plane and out-of-plane motions of the human tympanic membrane

“…Our data and TM preparations are consistent with both of the numerical constraints: The thickness of the human TM varies between 50 and 140 lm (Van der Jeught et al, 2013), and the largest displacements we observe are <3 lm, which leads to a displacement to thickness ratio of <0.06.…”

Investigation of middle ear anatomy and function with combined video otoscopy-phase sensitive OCT

“…The vibration magnitude is obtained in radians (rad) and then is converted to nanometers (nm) by multiplying the magnitude data with λ o /(4nπ), where λ o is the center wavelength of the laser light source and n is the sample refractive index. The refractive index of the tympanic membrane was assumed to be 1.44 [25].…”

“…The goal was to characterize the relationship between the intensity of the excitation signal and the sound pressure level (SPL) generated by the speaker for multiple frequencies. A circular film with a thickness of 0.05 mm and a diameter of 1/2" was prepared to mimic the size of the adult TM, which has a thickness on the order of 0.05 to 0.12 mm and diameter of on the order of 8 to 10 mm [25]. As the surface of the film is covered with the acrylate adhesive, the film was self-adhesively tightened on a half inch-diameter optical mount.…”

Low-cost hand-held probe for depth-resolved low-coherence interferometry

“…6(d) shows the surface image of the TM and the A-line obtained from a point on the TM, marked by a red asterisk in the inset. The thickness of the TM (assuming a refractive index of 1.4 for the TM [17]) was estimated to be 106 µm, which lies in the range of thickness values expected for a healthy TM [17][18][19][20].…”