Optical Coherence Tomography Doppler Vibrometry Measurement of Stapes Vibration in Patients With Stapes Fixation and Normal Controls

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

OBJECTIVE

Tympanic membrane (TM) thickness is an important parameter for differentiation between a healthy and a pathologic TM. Furthermore, it is needed for modeling the middle ear function. Endoscopic optical coherence tomography (eOCT) provides the opportunity to measure the TM thickness of the entire TM in vivo.

MATERIALS AND METHODS

A total of 27 healthy ears were examined by eOCT. The system uses a light source with a central wavelength of 1,300 nm. The endoscope with an outer diameter of 3.5 mm provides a field of view of 10 mm and a working distance of 10 mm. Thickness measurements were carried out at 8 points on the TM. Additionally, the existing literature was analyzed, and a mean TM thickness value was determined.

RESULTS

The mean thickness of the TM over all measurement points of the pars tensa was 120.2 μm, and the pars flaccida was significantly thicker with a mean thickness of 177.9 μm. Beyond that, there were no significant differences between the single quadrants. The mean TM thickness in the literature was 88.8 μm.

DISCUSSION

EOCT provides the possibility for in vivo thickness determination of the TM. The mean thickness seems to be higher than in the previous studies, which were mostly carried out ex vivo. Our study takes the three-dimensional refraction into account and provides a method for the refraction correction.

Electronic frequency shifting enables long, variable working distance optical coherence tomography

Increased imaging range is of growing interest in many applications of optical coherence tomography to reduce constraints on sample location, size, and topography. The design of optical coherence tomography systems with sufficient imaging range (e.g., 10s of centimeters) is a significant challenge due to the direct link between imaging range and acquisition bandwidth. We have developed a novel and flexible method to extend the imaging range in optical coherence tomography using electronic frequency shifting, enabling imaging in dynamic environments. In our approach, a laser with a quasi-linear sweep is used to limit the interferometric bandwidth, enabling decoupling of imaging range and acquisition bandwidth, while a tunable lens allows dynamic refocusing in the sample arm. Electronic frequency shifting then removes the need for high frequency digitization. This strategy is demonstrated to achieve high contrast morphological imaging over a > 21 cm working distance range, while maintaining high resolution and phase sensitivity. The system design is flexible to the application while requiring only a simple phase correction in post-processing. By implementing this approach in an auto-focusing paradigm, the proposed method demonstrates strong potential for the translation of optical coherence tomography into emerging applications requiring variable and centimeter-scale imaging ranges.

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

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.

Use of simulated data to explore the application of optical coherence tomography for classifying middle-ear pathologies

Optical coherence tomography (OCT) vibrometry is a non-invasive tool for functional imaging of the middle ear. It provides spatially resolved vibrational responses and also anatomical images of the same ear. Our objective here was to explore the potential of OCT vibration measurements at the incus, as well as at the umbo, to distinguish among middle-ear disorders. Our approach was to build finite-element models of normal and pathological ears, generate large amounts of synthetic data, and then classify the simulated data into normal and pathological groups using a decision tree based on features extracted from simulated vibration magnitudes. We could distinguish between normal ears and ears with incudomallear joint (IMJ) disarticulation or stapes fixation, with the sensitivity and specificity both being 1.0; distinguish between stapes fixation and IMJ disarticulation with a sensitivity of 0.900 and a specificity of 0.889; and distinguish ears with ISJ disarticulation from normal ears with a sensitivity of 0.784 and a specificity of 0.872. Less extreme pathologies were also simulated. The results suggest that the vibration measurements within the middle ear that can be provided by OCT (e.g., at the incus) may be very valuable for diagnosis.

Assessment of middle ear structure and function with optical coherence tomography

BACKGROUND

Current clinical tests for middle ear (ME) injuries and related conductive hearing loss (CHL) are lengthy and costly, lacking the ability to noninvasively evaluate both structure and function in real time. Optical coherence tomography (OCT) provides both, but its application to the audiological clinic is currently limited.

OBJECTIVE

Adapt and use a commercial Spectral-Domain OCT (SD-OCT) to evaluate anatomy and sound-evoked vibrations of the tympanic membrane (TM) and ossicles in the human ME.

MATERIALS AND METHODS

SD-OCT was used to capture high-resolution three-dimensional (3D) ME images and measure sound-induced vibrations of the TM and ossicles in fresh human temporal bones.

RESULTS

The 3D images provided thickness maps of the TM. The system was, with some software adaptations, also capable of phase-sensitive vibrometry. Measurements revealed several modes of TM vibration that became more complex with frequency. Vibrations were also measured from the incus, through the TM. This quantified ME sound transmission, which is the essential measure to assess CHL.

CONCLUSION AND SIGNIFICANCE

We adapted a commercial SD-OCT to visualize the anatomy and function of the human ME. OCT has the potential to revolutionize point-of-care assessment of ME disruptions that lead to CHL which are otherwise indistinguishable via otoscopy.

Geometrically accurate real-time volumetric visualization of the middle ear using optical coherence tomography

We introduce a novel system for geometrically accurate, continuous, live, volumetric middle ear optical coherence tomography imaging over a 10.9mm×30∘×30∘ field of view (FOV) from a handheld imaging probe. The system employs a discretized spiral scanning (DC-SC) pattern to rapidly collect volumetric data and applies real-time scan conversion and lateral angular distortion correction to reduce geometric inaccuracies to below the system's lateral resolution over 92% of the FOV. We validate the geometric accuracy of the resulting images through comparison with co-registered micro-computed tomography (micro-CT) volumes of a phantom target and a cadaveric middle ear. The system's real-time volumetric imaging capabilities are assessed by imaging the ear of a healthy subject while performing dynamic pressurization of the middle ear in a Valsalva maneuver.

Clinical practice guidelines for the diagnosis and management of otitis media with effusion (OME) in children in Japan - 2022 update

This is an update of the 2015 Guidelines developed by the Japan Otological Society and Oto-Rhino-Laryngeal Society of Japan defining otitis media with effusion (OME) in children (younger than 12 years old) and describing the disease rate, diagnosis, and method of examination. Recommended therapies that received consensus from the guideline committee were updated in consideration of current therapies used in Japan and based on available evidence.

METHOD

Regarding the treatment of OME in children, we developed Clinical Questions (CQs) and retrieved documents on each theme, including the definition, disease state, method of diagnosis, and medical treatment. In the previous guidelines, no retrieval expression was used to designate a period of time for literature retrieval. Conversely, a literature search of publications from March 2014 to May 2019 has been added to the JOS 2015 Guidelines. For publication of the CQs, we developed and assigned strengths to recommendations based on the collected evidence.

RESULTS

OME in children was classified into one group lacking the risk of developing chronic or intractable disease and another group at higher risk (e.g., children with Down syndrome, cleft palate), and recommendations for clinical management, including follow-up, is provided. Information regarding management of children with unilateral OME and intractable cases complicated by adhesive otitis media is also provided.

CONCLUSION

In clinical management of OME in children, the Japanese Clinical Practice Guidelines recommends management not only of complications of OME itself, such as effusion in the middle ear and pathologic changes in the tympanic membrane, but also pathologic changes in surrounding organs associated with infectious or inflammatory diseases.

Transtympanic Visualization of Cochlear Implant Placement With Optical Coherence Tomography: A Pilot Study

OBJECTIVE

This study aimed to evaluate the ability of transtympanic middle ear optical coherence tomography (ME-OCT) to assess placement of cochlear implants (CIs) in situ.

PATIENT

A 72-year-old man with bilateral progressive heredodegenerative sensorineural hearing loss due to work-related noise exposure received a CI with a slim modiolar electrode for his right ear 3 months before his scheduled checkup.

INTERVENTION

A custom-built swept source ME-OCT system (λo = 1550 nm, ∆λ = 40 nm) designed for transtympanic middle ear imaging was used to capture a series of two- and three-dimensional images of the patient's CI in situ. Separately, transtympanic OCT two-dimensional video imaging and three-dimensional imaging were used to visualize insertion and removal of a CI with a slim modiolar electrode in a human cadaveric temporal bone through a posterior tympanotomy.

MAIN OUTCOME MEASURE

Images and video were analyzed qualitatively to determine the visibility of implant features under ME-OCT imaging and quantitatively to determine insertion depth of the CI.

RESULTS

After implantation, the CI electrode could be readily visualized in the round window niche under transtympanic ME-OCT in both the patient and the temporal bone. In both cases, characteristic design features of the slim modiolar electrode allowed us to quantify the insertion depth from our images.

CONCLUSIONS

ME-OCT could potentially be used in a clinic as a noninvasive, nonionizing means to confirm implant placement. This study shows that features of the CI electrode visible under ME-OCT can be used to quantify insertion depth in the postoperative ear.

Optical Clearing Agents for Optical Imaging Through Cartilage Tympanoplasties: A Preclinical Feasibility Study

HYPOTHESIS

Optical clearing agents (OCAs) can render cartilage tympanoplasty grafts sufficiently transparent to permit visualization of middle ear structures in an operated ear using optical coherence tomography (OCT) imaging.

METHODS

Pieces of human tragal cartilage were treated with glycerol, a commonly used OCA. A reference reflector was imaged with OCT through the tympanoplasty as it cleared and the optical attenuation of the graft was measured. The reversibility of clearing and the dimensional changes associated with glycerol absorption were also measured. In a separate experiment, a human cadaveric temporal bone was prepared to simulate an ossiculoplasty surgery with cartilage replacement of the tympanic membrane. A partial ossicular replacement prosthesis (PORP) inserted in the ear was imaged with OCT through a 0.4mm cartilage graft optically cleared with glycerol.

MAIN OUTCOME MEASURE

The optical attenuation of 0.4mm cartilage grafts decreased at 2.3+/-1.1 dB/min following treatment with glycerol, reaching a total decrease in attenuation of 13.6+/-5.9 dB after 7 minutes. The optical and dimensional effects of glycerol absorption were reversable following saline washout. In the temporal bone preparation, treatment of a cartilage graft with glycerol resulted in a 13 dB increase in signal-to-noise ratio and a 13 dB increase in contrast for visualizing the PORP through the graft with OCT.

CONCLUSIONS

Optical clearing agents offer a potential pathway towards optical coherence tomography imaging of the middle ear in post-surgical ears with cartilage grafts.

In vivo functional imaging of the human middle ear with a hand-held optical coherence tomography device

We describe an optical coherence tomography and vibrometry system designed for portable hand-held usage in the otology clinic on awake patients. The system provides clinically relevant point-of-care morphological imaging with 14-44 µm resolution and functional vibratory measures with sub-nanometer sensitivity. We evaluated various new approaches for extracting functional information including a multi-tone stimulus, a continuous chirp stimulus, and alternating air and bone stimulus. We also explored the vibratory response over an area of the tympanic membrane (TM) and generated TM thickness maps. Our results suggest that the system can provide real-time in vivo imaging and vibrometry of the ear and could prove useful for investigating otologic pathology in the clinic setting.

Doppler Optical Coherence Tomography for Otology Applications: From Phantom Simulation to In Vivo Experiment

In otology, visualization and vibratory analysis have been crucial to enhance the success of diagnosis and surgical operation. Optical coherence tomography (OCT) has been employed in otology to obtain morphological structure of tissues non-invasively, owing to the ability of measuring the entire region of tympanic membrane, which compensates the limitations of conventional methods. As a functional extension of OCT, Doppler OCT, which enables the measurement of the motion information with structural data of tissue, has been applied in otology. Over the years, Doppler OCT systems have been evolved in various forms to enhance the measuring sensitivity of phase difference. In this review, we provide representative algorithms of Doppler OCT and various applications in otology from preclinical analysis to clinical experiments and discuss future developments.

Endoscopic Optical Coherence Tomography for Evaluation of Success of Tympanoplasty

OBJECTIVE

After tympanoplasty, it is often challenging to differentiate between different causes of a remaining air bone gap (ABG). Optical coherence tomography (OCT) offers a new approach for combined morphologic and functional measurements of the tympanic membrane and adjacent parts of the middle ear. Thus, it provides valuable diagnostic information in patients with a reduced sound transfer after middle ear surgery.

PATIENT AND INTERVENTION

A patient with history of tympanoplasty and a persistent ABG was investigated with endoscopic OCT before revision surgery.

MAIN OUTCOME MEASURES

The oscillation behavior and the thickness of the reconstructed tympanic membrane was determined. The oscillation amplitudes of the inserted prosthesis were compared to a finite element model simulation and to the clinical findings and the audiometric data of the patient.

RESULTS

OCT measurements showed a reduced oscillation amplitude of the prosthesis while revealing an aerated middle ear and good coupling of the prosthesis. Transfer loss measured by OCT showed a similar progression as the ABG measured by pure-tone audiometry with a mean divergence of 4.45 dB.

CONCLUSION

Endoscopic OCT is a promising tool for the evaluation of tympanoplasty outcome. It supports established otologic diagnostics and can help differentiating between different causes of conductional hearing loss.

Optical coherence tomography: current and future clinical applications in otology

PURPOSE OF REVIEW

This article reviews literature on the use of optical coherence tomography (OCT) in otology and provides the reader with a timely update on its current clinical and research applications. The discussion focuses on the principles of OCT, the use of the technology for the diagnosis of middle ear disease and for the delineation of in-vivo cochlear microarchitecture and function.

RECENT FINDINGS

Recent advances in OCT include the measurement of structural and vibratory properties of the tympanic membrane, ossicles and inner ear in healthy and diseased states. Accurate, noninvasive diagnosis of middle ear disease, such as otosclerosis and acute otitis media using OCT, has been validated in clinical studies, whereas inner ear OCT imaging remains at the preclinical stage. The development of recent microscopic, otoscopic and endoscopic systems to address clinical and research problems is reviewed.

SUMMARY

OCT is a real-time, noninvasive, nonionizing, point-of-care imaging modality capable of imaging ear structures in vivo. Although current clinical systems are mainly focused on middle ear imaging, OCT has also been shown to have the ability to identify inner ear disease, an exciting possibility that will become increasingly relevant with the advent of targeted inner ear therapies.