Noninvasive depth-resolved optical measurements of the tympanic membrane and middle ear for differentiating otitis media

Label-Free Optical Technologies for Middle-Ear Diseases

Medical applications of optical technology have increased tremendously in recent decades. Label-free techniques have the unique advantage of investigating biological samples in vivo without introducing exogenous agents. This is especially beneficial for a rapid clinical translation as it reduces the need for toxicity studies and regulatory approval for exogenous labels. Emerging applications have utilized label-free optical technology for screening, diagnosis, and surgical guidance. Advancements in detection technology and rapid improvements in artificial intelligence have expedited the clinical implementation of some optical technologies. Among numerous biomedical application areas, middle-ear disease is a unique space where label-free technology has great potential. The middle ear has a unique anatomical location that can be accessed through a dark channel, the external auditory canal; it can be sampled through a tympanic membrane of approximately 100 microns in thickness. The tympanic membrane is the only membrane in the body that is surrounded by air on both sides, under normal conditions. Despite these favorable characteristics, current examination modalities for middle-ear space utilize century-old technology such as white-light otoscopy. This paper reviews existing label-free imaging technologies and their current progress in visualizing middle-ear diseases. We discuss potential opportunities, barriers, and practical considerations when transitioning label-free technology to clinical applications.

Non-rigid point cloud registration for middle ear diagnostics with endoscopic optical coherence tomography

PURPOSE

Middle ear infection is the most prevalent inflammatory disease, especially among the pediatric population. Current diagnostic methods are subjective and depend on visual cues from an otoscope, which is limited for otologists to identify pathology. To address this shortcoming, endoscopic optical coherence tomography (OCT) provides both morphological and functional in vivo measurements of the middle ear. However, due to the shadow of prior structures, interpretation of OCT images is challenging and time-consuming. To facilitate fast diagnosis and measurement, improvement in the readability of OCT data is achieved by merging morphological knowledge from ex vivo middle ear models with OCT volumetric data, so that OCT applications can be further promoted in daily clinical settings.

METHODS

We propose C2P-Net: a two-staged non-rigid registration pipeline for complete to partial point clouds, which are sampled from ex vivo and in vivo OCT models, respectively. To overcome the lack of labeled training data, a fast and effective generation pipeline in Blender3D is designed to simulate middle ear shapes and extract in vivo noisy and partial point clouds.

RESULTS

We evaluate the performance of C2P-Net through experiments on both synthetic and real OCT datasets. The results demonstrate that C2P-Net is generalized to unseen middle ear point clouds and capable of handling realistic noise and incompleteness in synthetic and real OCT data.

CONCLUSIONS

In this work, we aim to enable diagnosis of middle ear structures with the assistance of OCT images. We propose C2P-Net: a two-staged non-rigid registration pipeline for point clouds to support the interpretation of in vivo noisy and partial OCT images for the first time. Code is available at: https://gitlab.com/nct_tso_public/c2p-net.

Texture-based speciation of otitis media-related bacterial biofilms from optical coherence tomography images using supervised classification

Otitis media (OM) is primarily a bacterial middle-ear infection prevalent among children worldwide. In recurrent and/or chronic OM cases, antibiotic-resistant bacterial biofilms can develop in the middle ear. A biofilm related to OM typically contains one or multiple bacterial strains, the most common include Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, and Staphylococcus aureus. Optical coherence tomography (OCT) has been used clinically to visualize the presence of bacterial biofilms in the middle ear. This study used OCT to compare microstructural image texture features from primary bacterial biofilms in vitro and in vivo. The proposed method applied supervised machine-learning-based frameworks (SVM, random forest (RF), and XGBoost) to classify and speciate multiclass bacterial biofilms from the texture features extracted from OCT B-Scan images obtained from in vitro cultures and from clinically-obtained in vivo images from human subjects. Our findings show that optimized SVM-RBF and XGBoost classifiers can help distinguish bacterial biofilms by incorporating clinical knowledge into classification decisions. Furthermore, both classifiers achieved more than 95% of AUC (area under receiver operating curve), detecting each biofilm class. These results demonstrate the potential for differentiating OM-causing bacterial biofilms through texture analysis of OCT images and a machine-learning framework, which could provide additional clinically relevant data during real-time in vivo characterization of ear infections.

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.

Quantitative transmastoid ultrasound for detecting middle ear effusion in pediatric patients

BACKGROUND AND OBJECTIVE

Ultrasound has emerged as a promising modality for detecting middle ear effusion (MEE) in pediatric patients. Among different ultrasound techniques, ultrasound mastoid measurement was proposed to allow noninvasive detection of MEE by estimating the Nakagami parameters of backscattered signals to describe the echo amplitude distribution. This study further developed the multiregional-weighted Nakagami parameter (MNP) of the mastoid as a new ultrasound signature for assessing effusion severity and fluid properties in pediatric patients with MEE.

METHODS

A total of 197 pediatric patients (n = 133 for the training group; n = 64 for the testing group) underwent multiregional backscattering measurements of the mastoid for estimating MNP values. MEE, the severity of effusion (mild to moderate vs. severe), and the fluid properties (serous and mucous) were confirmed through otoscopy, tympanometry, and grommet surgery and were compared with the ultrasound findings. The diagnostic performance was evaluated using the area under the receiver operating characteristic curve (AUROC).

RESULTS

The training dataset revealed significant differences in MNPs between the control and MEE groups, between mild to moderate and severe MEE, and between serous and mucous effusion were observed (p < 0.05). As with the conventional Nakagami parameter, the MNP could be used to detect MEE (AUROC: 0.87; sensitivity: 90.16%; specificity: 75.35%). The MNP could further identify effusion severity (AUROC: 0.88; sensitivity: 73.33%; specificity: 86.87%) and revealed the possibility of characterizing fluid properties (AUROC: 0.68; sensitivity: 62.50%; specificity: 70.00%). The testing results demonstrated that the MNP method enabled MEE detection (AUROC = 0.88, accuracy = 88.28%, sensitivity = 92.59%, specificity = 84.21%), was effective in assessing MEE severity (AUROC = 0.83, accuracy = 77.78%, sensitivity = 66.67%, specificity = 83.33%), and showed potential for characterizing fluid properties of effusion (AUROC = 0.70, accuracy = 72.22%, sensitivity = 62.50%, specificity = 80.00%).

CONCLUSIONS

Transmastoid ultrasound combined with the MNP not only leverages the strengths of the conventional Nakagami parameter for MEE diagnosis but also provides a means to assess MEE severity and effusion properties in pediatric patients, thereby offering a comprehensive approach to noninvasive MEE evaluation.

Finite-Element Modelling Based on Optical Coherence Tomography and Corresponding X-ray MicroCT Data for Three Human Middle Ears

PURPOSE

Optical coherence tomography (OCT) is an emerging imaging modality which is non-invasive, can be employed in vivo, and can record both anatomy and vibrations. The purpose here is to explore the application of finite-element (FE) modelling to OCT data.

METHODS

We recorded vibrations for three human cadaver middle ears using OCT. We also have X-ray microCT images from the same ears. Three FE models were built based on geometries obtained from the microCT images. The material properties and boundary conditions of the models were obtained from previously reported studies.

RESULTS

Tympanic-membrane (TM) vibration patterns were computed for the three models and compared with the patterns measured using OCT. Frequency responses were also computed for all three models for several locations in the middle ear and compared with the OCT displacements and with the literature. The three models were compared with each other in terms of geometry and function. Parameter sensitivity analyses were done and the results were compared among the models and with the literature. The simulated TM displacement patterns are qualitatively similar to the OCT results. The simulated displacements are closer to the OCT results for 500 Hz and 1 kHz but the differences are greater at 2 kHz.

CONCLUSION

This study provides an initial look at the combined use of OCT measurements and FE modelling based on subject-specific anatomy. The geometries and parameters of the existing FE models could be modified for individual patients in the future to help identify abnormalities in the middle ear.

In Vivo Optical Characterization of Middle Ear Effusions and Biofilms During Otitis Media

Otitis media (OM), a common ear infection, is characterized by the presence of an accumulated middle ear effusion (MEE) in a normally air-filled middle ear cavity. While assessing the MEE plays a critical role in the overall management of OM, identifying and examining the MEE is challenging with the current diagnostic tools since the MEE is located behind the semi-opaque eardrum. The objective of this cross-sectional, observational study is to non-invasively visualize and characterize MEEs and bacterial biofilms in the middle ear. A portable, handheld, otoscope-integrated optical coherence tomography (OCT) system combined with novel analytical methods has been developed. In vivo middle ear OCT images were acquired from 53 pediatric subjects (average age of 3.9 years; all awake during OCT imaging) diagnosed with OM and undergoing a surgical procedure (ear tube surgery) to aspirate the MEE and aerate the middle ear. In vivo middle ear OCT acquired prior to the surgery was compared with OCT of the freshly extracted MEEs, clinical diagnosis, and post-operative evaluations. Among the subjects who were identified with the presence of MEEs, 89.6% showed the presence of the TM-adherent biofilm in in vivo OCT. This study provides an atlas of middle ear OCT images exhibiting a range of depth-resolved MEE features, which can only be visualized and assessed non-invasively through OCT. Quantitative metrics of OCT images acquired prior to the surgery were statistically correlated with surgical evaluations of MEEs. Measurements of MEE characteristics will provide new readily available information that can lead to improved diagnosis and management strategies for the highly prevalent OM in children.

Otoendoscopy in the era of narrow-band imaging: a pictorial review

PURPOSE

Otoendoscopy represents the initial non-invasive diagnostic cornerstone for external and middle ear disorders. Recently, new techniques of enhanced imaging such as narrow-band imaging (NBI) have been introduced but their role as a potential aid in otological practice remains unproven. In this pictorial review, we want to present the potential application of this endoscopic method, highlight its limitations, and give some hints regarding its future implementation.

METHODS

Representative cases of external and/or middle ear pathologies were selected to illustrate the role of NBI in this regard.

RESULTS

NBI may represent a useful aid in the otological work-up, in the differential diagnosis of ear tumor-like masses, and, possibly, in the prognosis of tympanic perforations. For other ear disorders, instead, this technique does not seem to add anything to the standard clinical practice.

CONCLUSIONS

NBI might prove useful in the assessment of selected external and middle ear disorders but its role must be prospectively validated.

Evaluation of the Impact of Optical Coherence Tomography on Pediatrician Otologic Examination Judgment

Accurate diagnosis of otitis media is imperative to judicious antibiotic prescription. Visualization of the tympanic membrane and accurate identification of middle ear effusion with standard otoscopy is inherently challenging in pediatrics, especially in the youngest children who are most at risk for otitis media. With the average diagnostic accuracy among primary care physicians of 50% and accurate identification of normal tympanic membrane versus acute otitis media versus otitis media with effusion ranging from 30% to 84% among pediatricians, there is great opportunity for diagnostic improvement and decreasing unnecessary antibiotic use. In a 96-pediatrician-blinded otoscopy diagnosis quiz, addition of optical coherence tomography, a novel depth-imaging technology, resulted in a 32% improvement in fluid identification, and 21% increase in diagnostic accuracy. This study suggests that the clinical use of this technology promises to improve diagnostic accuracy and antibiotic stewardship in pediatrics.

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.

Differentiation of otitis media-causing bacteria and biofilms via Raman spectroscopy and optical coherence tomography

In the management of otitis media (OM), identification of causative bacterial pathogens and knowledge of their biofilm formation can provide more targeted treatment approaches. Current clinical diagnostic methods rely on the visualization of the tympanic membrane and lack real-time assessment of the causative pathogen(s) and the nature of any biofilm that may reside behind the membrane and within the middle ear cavity. In recent years, optical coherence tomography (OCT) has been demonstrated as an improved in vivo diagnostic tool for visualization and morphological characterization of OM biofilms and middle ear effusions; but lacks specificity about the causative bacterial species. This study proposes the combination of OCT and Raman spectroscopy (RS) to examine differences in the refractive index, optical attenuation, and biochemical composition of Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, and Pseudomonas aeruginosa; four of the leading otopathogens in OM. This combination provides a dual optical approach for identifying and differentiating OM-causing bacterial species under three different in vitro growth environments (i.e., agar-grown colonies, planktonic cells from liquid cultures, and biofilms). This study showed that RS was able to identify key biochemical variations to differentiate all four OM-causing bacteria. Additionally, biochemical spectral changes (RS) and differences in the mean attenuation coefficient (OCT) were able to distinguish the growth environment for each bacterial species.

Automated classification of otitis media with OCT: augmenting pediatric image datasets with gold-standard animal model data

Otitis media (OM) is an extremely common disease that affects children worldwide. Optical coherence tomography (OCT) has emerged as a noninvasive diagnostic tool for OM, which can detect the presence and quantify the properties of middle ear fluid and biofilms. Here, the use of OCT data from the chinchilla, the gold-standard OM model for the human disease, is used to supplement a human image database to produce diagnostically relevant conclusions in a machine learning model. Statistical analysis shows the datatypes are compatible, with a blended-species model reaching ∼95% accuracy and F1 score, maintaining performance while additional human data is collected.

Ex vivo transtympanic permeation of the liposome encapsulated S. pneumoniae endolysin MSlys

An increase in bacterial resistance to systemic antibiotics has sparked interest into alternative antimicrobial compounds as well as methods for effective local, non-invasive drug delivery. Topical treatments, however, may be hindered by the presence of biological barriers, such as the tympanic membrane in the case of otitis media. Herein, the transtympanic permeation ability of liposomes loaded with the pneumococcal endolysin MSlys and of free MSlys was evaluated ex vivo. MSlys loaded in PEGylated liposomes showed an increased permeation across human tympanic membranes, as compared to its free form, being able to reduce the pneumococcal cell load after 2 h of permeation. However, antipneumococcal activity was no longer detected after 4 h of permeation and hydrolysis of the endolysin was observed after an extended incubation time (≥48 h). This work provides a first assessment of a successful, non-invasive delivery method for endolysins across an intact tympanic membrane. Findings have implications for non-systemic, local treatment of otitis media.

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.

New Approaches and Technologies to Improve Accuracy of Acute Otitis Media Diagnosis

Several studies have shown that in recent years incidence of acute otitis media (AOM) has declined worldwide. However, related medical, social, and economic problems for patients, their families, and society remain very high. Better knowledge of potential risk factors for AOM development and more effective preventive interventions, particularly in AOM-prone children, can further reduce disease incidence. However, a more accurate AOM diagnosis seems essential to achieve this goal. Diagnostic uncertainty is common, and to avoid risks related to a disease caused mainly by bacteria, several children without AOM are treated with antibiotics and followed as true AOM cases. The main objective of this manuscript is to discuss the most common difficulties that presently limit accurate AOM diagnosis and the new approaches and technologies that have been proposed to improve disease detection. We showed that misdiagnosis can be dangerous or lead to relevant therapeutic mistakes. The need to improve AOM diagnosis has allowed the identification of a long list of technologies to visualize and evaluate the tympanic membrane and to assess middle-ear effusion. Most of the new instruments, including light field otoscopy, optical coherence tomography, low-coherence interferometry, and Raman spectroscopy, are far from being introduced in clinical practice. Video-otoscopy can be effective, especially when it is used in association with telemedicine, parents' cooperation, and artificial intelligence. Introduction of otologic telemedicine and use of artificial intelligence among pediatricians and ENT specialists must be strongly promoted in order to reduce mistakes in AOM diagnosis.

Enhanced medical diagnosis for dOCTors: a perspective of optical coherence tomography

SIGNIFICANCE

After three decades, more than 75,000 publications, tens of companies being involved in its commercialization, and a global market perspective of about USD 1.5 billion in 2023, optical coherence tomography (OCT) has become one of the fastest successfully translated imaging techniques with substantial clinical and economic impacts and acceptance.

AIM

Our perspective focuses on disruptive forward-looking innovations and key technologies to further boost OCT performance and therefore enable significantly enhanced medical diagnosis.

APPROACH

A comprehensive review of state-of-the-art accomplishments in OCT has been performed.

RESULTS

The most disruptive future OCT innovations include imaging resolution and speed (single-beam raster scanning versus parallelization) improvement, new implementations for dual modality or even multimodality systems, and using endogenous or exogenous contrast in these hybrid OCT systems targeting molecular and metabolic imaging. Aside from OCT angiography, no other functional or contrast enhancing OCT extension has accomplished comparable clinical and commercial impacts. Some more recently developed extensions, e.g., optical coherence elastography, dynamic contrast OCT, optoretinography, and artificial intelligence enhanced OCT are also considered with high potential for the future. In addition, OCT miniaturization for portable, compact, handheld, and/or cost-effective capsule-based OCT applications, home-OCT, and self-OCT systems based on micro-optic assemblies or photonic integrated circuits will revolutionize new applications and availability in the near future. Finally, clinical translation of OCT including medical device regulatory challenges will continue to be absolutely essential.

CONCLUSIONS

With its exquisite non-invasive, micrometer resolution depth sectioning capability, OCT has especially revolutionized ophthalmic diagnosis and hence is the fastest adopted imaging technology in the history of ophthalmology. Nonetheless, OCT has not been completely exploited and has substantial growth potential-in academics as well as in industry. This applies not only to the ophthalmic application field, but also especially to the original motivation of OCT to enable optical biopsy, i.e., the in situ imaging of tissue microstructure with a resolution approaching that of histology but without the need for tissue excision.

Pharmacokinetics of Single Dose Lidocaine and Epinephrine Following Iontophoresis of the Tympanic Membrane in a Double-Blinded Randomized Trial

OBJECTIVE

To evaluate local and systemic safety of bilateral iontophoretic administration of lidocaine with epinephrine or lidocaine alone to the tympanic membrane (TM).

STUDY DESIGN

A randomized, double-blind, two-arm study was conducted at a single center. Healthy adults were randomized to bilateral iontophoretic treatment with 2% lidocaine, 1:100,000 epinephrine, or 2% lidocaine (control). Otoscopy, cranial nerve examination, tympanometry, and audiometry safety evaluations were conducted before and 3-days post-procedure. Systemic safety was evaluated via analysis of vital signs taken before and up to 120 minutes post-iontophoresis, and blood samples collected before and up to 230 minutes post-iontophoresis.

RESULTS

Twenty-five subjects were treated with bilateral iontophoresis of either lidocaine and epinephrine (n = 15 subjects) or lidocaine alone (n = 10). Mean plasma epinephrine concentrations for both groups remained within the normal range for endogenous epinephrine. Mean plasma concentrations of lidocaine were not statistically different between groups, ranging from 0.245 to 2.28 ng/ml after administration of lidocaine with epinephrine (immediate post-iontophoresis to 230 min post-iontophoresis), compared with 1.35 to 2.14 ng/ml after administration of lidocaine alone. The presence of epinephrine slowed the systemic absorption of lidocaine. Lidocaine levels (Cmax 2.24 ng/ml) were approximately 2000-fold lower than the threshold for minor lidocaine toxicity. No device-, procedure- or drug-related adverse events were reported.

CONCLUSION

The local and systemic safety of bilateral iontophoretic delivery of 2% lidocaine, 1:100,000 epinephrine to the TM was demonstrated by low plasma levels of drug and absence of both serious and non-serious device-, procedure-, or drug-related adverse events.

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.

Assessing the Effect of Middle Ear Effusions on Wideband Acoustic Immittance Using Optical Coherence Tomography

Wideband acoustic immittance (WAI) noninvasively assesses middle ear function by measuring the sound conduction over a range of audible frequencies. Although several studies have shown the potential of WAI for detecting the presence of middle ear effusions (MEEs), determining the effects of MEE type and amount on WAI in vivo has been challenging due to the anatomical location of middle ear cavity. The purpose of this study is to correlate WAI measurements with physical characteristics of the middle ear and MEEs determined by optical coherence tomography (OCT), a noninvasive optical imaging technique.

A review of low-cost and portable optical coherence tomography

Optical coherence tomography (OCT) is a powerful optical imaging technique capable of visualizing the internal structure of biological tissues at near cellular resolution. For years, OCT has been regarded as the standard of care in ophthalmology, acting as an invaluable tool for the assessment of retinal pathology. However, the costly nature of most current commercial OCT systems has limited its general accessibility, especially in low-resource environments. It is therefore timely to review the development of low-cost OCT systems as a route for applying this technology to population-scale disease screening. Low-cost, portable and easy to use OCT systems will be essential to facilitate widespread use at point of care settings while ensuring that they offer the necessary imaging performances needed for clinical detection of retinal pathology. The development of low-cost OCT also offers the potential to enable application in fields outside ophthalmology by lowering the barrier to entry. In this paper, we review the current development and applications of low-cost, portable and handheld OCT in both translational and research settings. Design and cost-reduction techniques are described for general low-cost OCT systems, including considerations regarding spectrometer-based detection, scanning optics, system control, signal processing, and the role of 3D printing technology. Lastly, a review of clinical applications enabled by low-cost OCT is presented, along with a detailed discussion of current limitations and outlook.

Inactivation and sensitization of Pseudomonas aeruginosa by microplasma jet array for treating otitis media

Otitis media (OM), known as a middle ear infection, is the leading cause of antibiotic prescriptions for children. With wide-spread use of antibiotics in OM, resistance to antibiotics continues to decrease the efficacy of the treatment. Furthermore, as the presence of a middle ear biofilm has contributed to this reduced susceptibility to antimicrobials, effective interventions are necessary. A miniaturized 3D-printed microplasma jet array has been developed to inactivate Pseudomonas aeruginosa, a common bacterial strain associated with OM. The experiments demonstrate the disruption of planktonic and biofilm P. aeruginosa by long-lived molecular species generated by microplasma, as well as the synergy of combining microplasma treatment with antibiotic therapy. In addition, a middle ear phantom model was developed with an excised rat eardrum to investigate the antimicrobial effects of microplasma on bacteria located behind the eardrum, as in a patient-relevant setup. These results suggest the potential for microplasma as a new treatment paradigm for OM.

Handheld Briefcase Optical Coherence Tomography with Real-Time Machine Learning Classifier for Middle Ear Infections

A middle ear infection is a prevalent inflammatory disease most common in the pediatric population, and its financial burden remains substantial. Current diagnostic methods are highly subjective, relying on visual cues gathered by an otoscope. To address this shortcoming, optical coherence tomography (OCT) has been integrated into a handheld imaging probe. This system can non-invasively and quantitatively assess middle ear effusions and identify the presence of bacterial biofilms in the middle ear cavity during ear infections. Furthermore, the complete OCT system is housed in a standard briefcase to maximize its portability as a diagnostic device. Nonetheless, interpreting OCT images of the middle ear more often requires expertise in OCT as well as middle ear infections, making it difficult for an untrained user to operate the system as an accurate stand-alone diagnostic tool in clinical settings. Here, we present a briefcase OCT system implemented with a real-time machine learning platform for middle ear infections. A random forest-based classifier can categorize images based on the presence of middle ear effusions and biofilms. This study demonstrates that our briefcase OCT system coupled with machine learning can provide user-invariant classification results of middle ear conditions, which may greatly improve the utility of this technology for the diagnosis and management of middle ear infections.

In vivo dynamic characterization of the human tympanic membrane using pneumatic optical coherence tomography

Decreased mobility of the human eardrum, the tympanic membrane (TM), is an essential indicator of a prevalent middle ear infection. The current diagnostic method to assess TM mobility is via pneumatic otoscopy, which provides subjective and qualitative information of subtle motion. In this study, a handheld spectral-domain pneumatic optical coherence tomography system was developed to simultaneously measure the displacement of the TM, air pressure inputs applied to a sealed ear canal, and to perform digital pneumatic otoscopy. A novel approach based on quantitative parameters is presented to characterize spatial and temporal variations of the dynamic TM motion. Furthermore, the TM motions of normal middle ears are compared with those of ears with middle ear infections. The capability of noninvasively measuring the rapid motion of the TM is beneficial to understand the complex dynamics of the human TM, and can ultimately lead to improved diagnosis and management of middle ear infections.

Longitudinal optical coherence tomography to visualize the in vivo response of middle ear biofilms to antibiotic therapy

Studying the impact of antibiotic treatment on otitis media (OM), the leading cause of primary care office visits during childhood, is critical to develop appropriate treatment strategies. Tracking dynamic middle ear conditions during antibiotic treatment is not readily applicable in patients, due to the limited diagnostic techniques available to detect the smaller amount and variation of middle ear effusion (MEE) and middle ear bacterial biofilm, responsible for chronic and recurrent OM. To overcome these challenges, a handheld optical coherence tomography (OCT) system has been developed to monitor in vivo response of biofilms and MEEs in the OM-induced chinchilla model, the standard model for human OM. As a result, the formation of MEE as well as biofilm adherent to the tympanic membrane (TM) was longitudinally assessed as OM developed. Various types of MEEs and biofilms in the chinchilla model were identified, which showed comparable features as those in humans. Furthermore, the effect of antibiotics on the biofilm as well as the amount and type of MEEs was investigated with low-dose and high-dose treatment (ceftriaxone). The capability of OCT to non-invasively track and examine middle ear conditions is highly beneficial for therapeutic OM studies and will lead to improved management of OM in patients.

Handheld optical coherence tomography for clinical assessment of dental plaque and gingiva

SIGNIFICANCE

Optical coherence tomography (OCT) offers high spatial resolution and contrast for imaging intraoral structures, yet few studies have investigated its clinical feasibility for dental plaque and gingiva imaging in vivo. Furthermore, the accessibility is often limited to anterior teeth due to bulky imaging systems and probes.

AIM

A custom-designed, handheld probe-based, spectral-domain OCT system with an interchangeable attachment was developed to assess dental plaque and gingival health in a clinical setting.

APPROACH

Healthy volunteers and subjects with gingivitis and sufficient plaque were recruited. The handheld OCT system was operated by trained dental hygienists to acquire images of dental plaque and gingiva at various locations and after one-week use of oral hygiene products.

RESULTS

The handheld OCT can access premolars, first molars, and lingual sides of teeth to visualize the plaque distribution. OCT intensity-based texture analysis revealed lower intensity from selected sites in subjects with gingivitis. The distribution of the dental plaque after one-week use of the oral hygiene products was compared, showing the capability of OCT as a longitudinal tracking tool.

CONCLUSIONS

OCT has a strong potential to display and assess dental plaque and gingiva in a clinical setting. Meanwhile, technological challenges remain to perform systematic longitudinal tracking and comparative analyses.

A bench-top model of middle ear effusion diagnosed with optical tympanometry

OBJECTIVES

To assess the validity of a bench-top model of an optical tympanometry device to diagnose in vitro model of middle ear effusion (MEE).

METHODS AND MATERIALS

We illuminated an in vitro model of ear canal and tympanic membrane with broadband light and relayed remitted light to a spectrometer system. We then used our proprietary algorithm to extract spectral features that, together with our logistic regression classifiers, led us to calculate a set of simplified indices related to different middle ear states. Our model included a glass vial covered with a porcine submucosa (representing the tympanic membrane) and filled with air, water, or milk solution (representing different MEE), and a set of cover-glass slips filled with either blood (representing erythema) or cerumen. By interchanging fluid types and cover-glass slips, we made measurements on combinations corresponding to normal healthy ear and purulent or serous MEE.

RESULTS

Each simulated condition had a distinct spectral profile, which was then employed by our algorithm to discriminate clean and cerumen-covered purulent and serous MEE. Two logistic purulent and serous MEE classifiers correctly classified all in vitro middle ear states with 100% accuracy assessed by leave-one-out and k-fold cross validation.

CONCLUSIONS

This proof-of-concept in vitro study addressed an unmet need by introducing a device that easily and accurately can assess middle ear effusion. Future in vivo studies aimed at collecting data from clinical settings are warranted to further elucidate the validity of the technology in diagnosing pediatric acute otitis media.

Optical Identification of Middle Ear Infection

Ear infection is one of the most commonly occurring inflammation diseases in the world, especially for children. Almost every child encounters at least one episode of ear infection before he/she reaches the age of seven. The typical treatment currently followed by physicians is visual inspection and antibiotic prescription. In most cases, a lack of improper treatment results in severe bacterial infection. Therefore, it is necessary to design and explore advanced practices for effective diagnosis. In this review paper, we present the various types of ear infection and the related pathogens responsible for middle ear infection. We outline the conventional techniques along with clinical trials using those techniques to detect ear infections. Further, we highlight the need for emerging techniques to reduce ear infection complications. Finally, we emphasize the utility of Raman spectroscopy as a prospective non-invasive technique for the identification of middle ear infection.

Role of Biofilms in Post-Tympanostomy Tube Otorrhea

OBJECTIVE

Nearly half of children who undergo tympanostomy tube (TT) insertion may experience otorrhea following surgery. We sought to review the evidence for the role of bacterial biofilms in post-tympanostomy tube otorrhea (PTTO) and the accumulated experience regarding the preventive measures for biofilm formation/adhesion on TTs.

METHODS

English literature search for relevant MeSH keywords was conducted in the following databases: MEDLINE (via PubMed), Ovid Medline, Google Scholar, and Clinical Evidence (BMJ Publishing) between January 1, 1995, and December 31, 2019. Subsequently, articles were reviewed and included if biofilm was evident in PTTO.

RESULTS

There is an increased evidence supporting the role of biofilms in PTTO. Studies on TT design and material suggest that nitinol and/or silicone TTs had a lower risk for PTTO and that biofilms appeared in specific areas, such as the perpendicular junction of the T-tubes and the round rims of the Paparella-type tubes. Biofilm-component DNAB-II protein family was present in half of children with PTTO, and targeting this protein may lead to biofilm collapse and serve as a potential strategy for PTTO treatment. Novel approaches for the prevention of biofilm-associated PTTO include changing the inherent tube composition; tube coating with antibiotics, polymers, plant extracts, or other biofilm-resistant materials; impregnation with antimicrobial compounds; and surface alterations by ion-bombardment or surface ionization, which are still under laboratory investigation.

CONCLUSIONS

Currently, there is no type of TT on which bacteria will not adhere. The challenges of treating PTTO indicate the need for further research in optimization of TT design, composition, and coating.

Panel 1: Biotechnology, biomedical engineering and new models of otitis media

OBJECTIVE

To summarize recently published key articles on the topics of biomedical engineering, biotechnology and new models in relation to otitis media (OM).

DATA SOURCES

Electronic databases: PubMed, Ovid Medline, Cochrane Library and Clinical Evidence (BMJ Publishing).

REVIEW METHODS

Articles on biomedical engineering, biotechnology, material science, mechanical and animal models in OM published between May 2015 and May 2019 were identified and subjected to review. A total of 132 articles were ultimately included.

RESULTS

New imaging technologies for the tympanic membrane (TM) and the middle ear cavity are being developed to assess TM thickness, identify biofilms and differentiate types of middle ear effusions. Artificial intelligence (AI) has been applied to train software programs to diagnose OM with a high degree of certainty. Genetically modified mice models for OM have further investigated what predisposes some individuals to OM and consequent hearing loss. New vaccine candidates protecting against major otopathogens are being explored and developed, especially combined vaccines, targeting more than one pathogen. Transcutaneous vaccination against non-typeable Haemophilus influenzae has been successfully tried in a chinchilla model. In terms of treatment, novel technologies for trans-tympanic drug delivery are entering the clinical domain. Various growth factors and grafting materials aimed at improving healing of TM perforations show promising results in animal models.

CONCLUSION

New technologies and AI applications to improve the diagnosis of OM have shown promise in pre-clinical models and are gradually entering the clinical domain. So are novel vaccines and drug delivery approaches that may allow local treatment of OM.

IMPLICATIONS FOR PRACTICE

New diagnostic methods, potential vaccine candidates and the novel trans-tympanic drug delivery show promising results, but are not yet adapted to clinical use.

Functional assessment of moisture influenced cadaveric tympanic membrane using phase shift-resolved optical Doppler vibrography

An elevated relative moisture in the external ear canal and middle ear cavity may predispose to chronic otorrhea and related infections along with abnormal tympanic membrane (TM) vibration patterns. Therefore, phase shift-resolved optical Doppler vibrography (ODV) was used for vibration assessments of moisture influenced cadaveric TM. ODV was applied to generate time resolved cross-sectional and volumetric vibrographs of a cadaveric TM, driven acoustically at several frequencies. In order to analyze the effect of moisture on TM, homogenous moisture conditions were provided by soaking the cadaveric TM specimens in 1× phosphate buffer saline with a pH of 7.4. The TM specimen was exposed to a rapidly switchable frequency generator during the ODV image acquisition. The experiment was conducted for 3 hours and the cadaveric TM was exposed to each frequency with an interval of 30 minutes. Acquired phase shift-resolved ODV assessments revealed a depth dependent vibration tendency between the applied frequencies, along with a decline in the moisture level of the cadaveric TM specimen. Thus, the ODV method can aid our understanding of sound conduction in the middle ear, thus supporting the diagnosis of TM diseases.

Otitis Media Middle Ear Effusion Identification and Characterization Using an Optical Coherence Tomography Otoscope

OBJECTIVE

To determine the feasibility of detecting and differentiating middle ear effusions (MEEs) using an optical coherence tomography (OCT) otoscope.

STUDY DESIGN

Cross-sectional study.

SETTING

US tertiary care children's hospital.

SUBJECTS AND METHODS

Seventy pediatric patients undergoing tympanostomy tube placement were preoperatively imaged using an OCT otoscope. A blinded reader quiz was conducted using 24 readers from 4 groups of tiered medical expertise. The primary outcome assessed was reader ability to detect presence/absence of MEE. A secondary outcome assessed was reader ability to differentiate serous vs nonserous MEE.

RESULTS

OCT image data sets were analyzed from 45 of 70 total subjects. Blinded reader analysis of an OCT data subset for detection of MEE resulted in 90.6% accuracy, 90.9% sensitivity, 90.2% specificity, and intra/interreader agreement of 92.9% and 87.1%, respectively. Differentiating MEE type, reader identification of nonserous MEE had 70.8% accuracy, 53.6% sensitivity, 80.1% specificity, and intra/interreader agreement of 82.9% and 75.1%, respectively. Multivariate analysis revealed that age was the strongest predictor of OCT quality. The mean age of subjects with quality OCT was 5.01 years (n = 45), compared to 2.54 years (n = 25) in the remaining subjects imaged (P = .0028). The ability to capture quality images improved over time, from 50% to 69.4% over the study period.

CONCLUSION

OCT otoscopy shows promise for facilitating accurate MEE detection. The imageability with the prototype device was affected by age, with older children being easier to image, similar to current ear diagnostic technologies.

[Overview of modern methods for the diagnosis of exudative otitis media]

Modern methods for diagnosis of exudative otitis media (EOM) have great potential, however, the problem of diagnosis of EOM is still relevant. The article describes the methods of modern diagnostics that are widely used in the daily practice of an otolaryngologist. The basic principles, advantages and disadvantages of generally accepted diagnostic methods for EOM are presented. The method of optical coherence tomography (OCT) is described as a method of studying biological tissues, which is used in many fields of medicine. Information is provided on the possibilities of OCT in the diagnosis of diseases of the ENT organs and, in particular, of the middle ear. The results of studies of the tympanic cavity structures in various inflammatory conditions, the possibilities of intrasurgery use of OCT, as well as the possibilities and perspectives of introducing OCT into the practice of an otorhinolaryngologist in the diagnosis of exudative otitis media are described.

Extratympanic Observation of Middle and Inner Ear Structures in Rodents Using Optical Coherence Tomography

Objectives

This study aimed to investigate whether optical coherence tomography (OCT) provides useful information about the microstructures of the middle and inner ear via extratympanic approach and thereby could be utilized as an alternative diagnostic technology in ear imaging.

Methods

Five rats and mice were included, and the swept-source OCT system was applied to confirm the extent of visibility of the middle and inner ear and measure the length or thickness of the microstructures in the ear. The cochlea was subsequently dissected following OCT and histologically evaluated to compare with the OCT images.

Results

The middle ear microstructures such as ossicles, stapedial artery and oval window through the tympanic membrane with the OCT could be confirmed in both rats and mice. It was also possible to obtain the inner ear images such as each compartment of the cochlea in the mice, but the bone covering bulla needed to be removed to visualize the inner ear structures in the rats which had thicker bulla. The bony thickness covering the cochlea could be measured, which showed no significant differences between OCT and histologic image at all turns of cochlea.

Conclusion

OCT has been shown a promising technology to assess real-time middle and inner ear microstructures noninvasively with a high-resolution in the animal model. Therefore, OCT could be utilized to provide additional diagnostic information about the diseases of the middle and inner ear.

Recovery from tympanic membrane perforation: Effects on membrane thickness, auditory thresholds, and middle ear transmission

Sounds delivered to the ear move the tympanic membrane (TM), which drives the middle-ear (ME) ossicles and transfers the acoustic energy to the cochlea. Perforations of the TM result in hearing loss because of less efficient sound conduction through the ME. The patterns of TM motions, and thus ME sound transmission, vary with frequency and depend on many factors, including the TM thickness. In this study, we measured TM thickness, auditory brainstem responses (ABR), and ME transmission immediately following a controlled pars tensa perforation and after 4 weeks of spontaneous recovery in a gerbil model. It is found that after recovery, the hearing thresholds showed a sloping pattern across frequencies: almost back to normal levels at frequencies between 2 and 8 kHz, sloping loss in the low (<2 kHz) and mid-frequency (8-30 kHz) range, and little restoration at frequencies above 30 kHz. This pattern was confirmed by the measured ME pressure gains. The thickness of the healed TM did not return to normal but was 2-3 times thicker over a significant portion of the membrane. The increased thickness was not limited to the perforated area but expanded into intact regions adjacent to the perforation, which led to an increased thickness in general. Combined, these results suggest that TM thickness is an important factor in determining its vibration patterns and efficiency to transfer sounds to the ossicles and thus influencing ME sound transmission, especially for high-frequency sounds. The results provided both structural and functional observations to explain the conductive hearing loss seen in patients with abnormal TMs, e.g., caused by otitis media, spontaneously healed post-perforation, or repaired via tympanoplasty in the clinic.

In vivo detection of endotracheal tube biofilms in intubated critical care patients using catheter-based optical coherence tomography

The formation of biofilms in the endotracheal tubes (ETTs) of intubated patients on mechanical ventilation is associated with a greater risk of ventilator-associated pneumonia and death. New technologies are needed to detect and monitor ETTs in vivo for the presence of these biofilms. Longitudinal OCT imaging was performed in mechanically ventilated subjects at 24-hour intervals until extubation to detect the formation and temporal changes of in vivo ETT biofilms. OCT-derived attenuation coefficient images were used to differentiate between mucus and biofilm. Extubated ETTs were examined with optical and electron microscopy, and all imaging results were correlated with standard-of-care clinical test reports. OCT and attenuation coefficient images from four subjects were positive for ETT biofilms and were negative for two subjects. The processed and stained extubated ETTs and clinical reports confirmed the presence/absence of biofilms in all subjects. Our findings confirm that OCT can detect and differentiate between biofilm-positive and biofilm-negative groups (P < 10-5 ). OCT image-based features may serve as biomarkers for direct in vivo detection of ETT biofilms and help drive investigation of new management strategies to reduce the incidence of VAP.

Automated classification platform for the identification of otitis media using optical coherence tomography

The diagnosis and treatment of otitis media (OM), a common childhood infection, is a significant burden on the healthcare system. Diagnosis relies on observer experience via otoscopy, although for non-specialists or inexperienced users, accurate diagnosis can be difficult. In past studies, optical coherence tomography (OCT) has been used to quantitatively characterize disease states of OM, although with the involvement of experts to interpret and correlate image-based indicators of infection with clinical information. In this paper, a flexible and comprehensive framework is presented that automatically extracts features from OCT images, classifies data, and presents clinically relevant results in a user-friendly platform suitable for point-of-care and primary care settings. This framework was used to test the discrimination between OCT images of normal controls, ears with biofilms, and ears with biofilms and middle ear fluid (effusion). Predicted future performance of this classification platform returned promising results (90%+ accuracy) in various initial tests. With integration into patient healthcare workflow, users of all levels of medical experience may be able to collect OCT data and accurately identify the presence of middle ear fluid and/or biofilms.

Emerging Technologies for the Diagnosis of Otitis Media

OBJECTIVE

To review new experimental techniques for the diagnosis of otitis media (OM).

DATA SOURCES

Literature search in English in the following databases: MEDLINE (via PubMed), Ovid Medline, Google Scholar, and Clinical Evidence (BMJ Publishing) between January 1, 2005, and April 30, 2018. Subsequently, articles were reviewed and included only if relevant.

REVIEW METHODS

MeSH terms: ["diagnosis"] AND [all forms of OM] AND ["human"] AND ["ear"] and ["tympanic membrane"]. The retrieved innovative diagnostic techniques rely on and take advantage of the physical properties of the tympanomastoid cavity components: tympanic membrane (TM) thickness, its translucency and compliance; middle ear fluid characteristics; biofilm presence; increased tissue metabolic activity in OM states; and fluid presence in the mastoid cavity. These parameters are taken into account to establish OM diagnosis objectively. We review spectral gradient acoustic reflectometry, digital otoscopy, TM image analysis, multicolor reflectance imaging, anticonfocal middle ear assessment, optical coherence tomography, quantitative pneumatic otoscopy, transmastoid ultrasound, wideband measurements, TM thickness mapping, shortwave infrared imaging, and wideband acoustic transfer functions.

CONCLUSIONS

New experimental techniques are gradually introduced to overcome the limitations of standard otoscopy. The aforementioned techniques are still under investigation and are pending widespread clinical use. The implementation of these techniques in the market is dependent on their success in clinical trials, as well as on their future cost.

IMPLICATION FOR PRACTICE

New techniques for the diagnosis of OM can objectively evaluate the morphology of the TM, determine the presence of middle ear fluid and evaluate its content, and thus potentially replace standard otoscopy.

Mapping the phase and amplitude of ossicular chain motion using sound-synchronous optical coherence vibrography

The sound-driven vibration of the tympanic membrane and ossicular chain of middle-ear bones is fundamental to hearing. Here we show that optical coherence tomography in phase synchrony with a sound stimulus is well suited for volumetric, vibrational imaging of the ossicles and tympanic membrane. This imaging tool - OCT vibrography - provides intuitive motion pictures of the ossicular chain and how they vary with frequency. Using the chinchilla ear as a model, we investigated the vibrational snapshots and phase delays of the manubrium, incus, and stapes over 100 Hz to 15 kHz. The vibrography images reveal a previously undescribed mode of motion of the chinchilla ossicles at high frequencies.

Smartphone Otoscopy Performed by Parents

Introduction: Implementation of pediatric telemedicine has been emphasized. We examined whether parents could perform smartphone otoscopy for the diagnosis of otitis media. Materials and Methods: We included children (6-35 months) attending day care with at least one episode of acute otitis media (AOM) within 90 days of the study entry. The timing for a teaching intervention was randomized. In the immediate teaching group, parents were taught smartphone otoscopy and cerumen was removed at the first visit. The delayed teaching group received the teaching intervention after 1 week's independent use. During the 60 study days, parents performed home examinations. The main outcome, the diagnostic quality of the tympanic membrane videos to determine healthy ear, otitis media with effusion (OME) and AOM diagnoses was measured with a structured video analysis independently by three physicians. Parents' experience was measured with a questionnaire. Results: AOM could be detected or excluded in 87% (609/699) of the videos during acute symptoms. After the teaching intervention, healthy ear, OME, or AOM could be diagnosed in 40% (521/1,293) of the videos. During the first week's intervention, one of the three diagnoses was attained in 33% (50/153) and in 12% (22/179) of the videos in the immediate and delayed teaching group, respectively (p < 0.001). The performance of the smartphone otoscopy examination was easy in 85% (35/41) of families. Discussion: After been taught, parents are able to perform smartphone otoscopy for the remote detection or exclusion of AOM. Conclusions: Future studies should assess the clinical usefulness of parent-performed smartphone otoscopy.

In vivo detection of nanometer-scale structural changes of the human tympanic membrane in otitis media

Otitis media (OM) is a common ear infection and a leading cause of conductive hearing loss in the pediatric population. Current technologies such as otoscopy, pneumatic otoscopy, tympanometry, and acoustic reflectometry are used to diagnose OM, which can reasonably diagnose the infection with a sensitivity and specificity of 50-90% and 60-90%, respectively. However, these techniques provide limited information about the physical architecture of the tympanic membrane (TM), or what may lie behind it. Here, we report the detection of nanometer-scale structural changes of the TM using nano-sensitive optical coherence tomography (nsOCT). In total, an image dataset from 65 pediatric subjects from three different groups (normal, acute OM, and chronic OM) and with longitudinal image-based analysis of ear infections were included in this study. The nsOCT data were correlated with physician diagnosis and with OCT thickness measurements and were found to be in good agreement with these results. We report that nsOCT detects in vivo structural deformations of the TM earlier than OCT alone, and enhances the detection sensitivity of OCT measurements. This unique technique for early detection of nano-scale structural modifications in the TM has the potential to aid in our understanding of microbiological effects, and possibly for early diagnosis and more effective treatment of OM.

Optical Coherence Tomography of the Tympanic Membrane and Middle Ear: A Review

Objective To evaluate the recent developments in optical coherence tomography (OCT) for tympanic membrane (TM) and middle ear (ME) imaging and to identify what further development is required for the technology to be integrated into common clinical use. Data Sources PubMed, Embase, Google Scholar, Scopus, and Web of Science. Review Methods A comprehensive literature search was performed for English language articles published from January 1966 to January 2018 with the keywords "tympanic membrane or middle ear,""optical coherence tomography," and "imaging." Conclusion Conventional imaging techniques cannot adequately resolve the microscale features of TM and ME, sometimes necessitating diagnostic exploratory surgery in challenging otologic pathology. As a high-resolution noninvasive imaging technique, OCT offers promise as a diagnostic aid for otologic conditions, such as otitis media, cholesteatoma, and conductive hearing loss. Using OCT vibrometry to image the nanoscale vibrations of the TM and ME as they conduct acoustic waves may detect the location of ossicular chain dysfunction and differentiate between stapes fixation and incus-stapes discontinuity. The capacity of OCT to image depth and thickness at high resolution allows 3-dimensional volumetric reconstruction of the ME and has potential use for reconstructive tympanoplasty planning and the follow-up of ossicular prostheses. Implications for Practice To achieve common clinical use beyond these initial discoveries, future in vivo imaging devices must feature low-cost probe or endoscopic designs and faster imaging speeds and demonstrate superior diagnostic utility to computed tomography and magnetic resonance imaging. While such technology has been available for OCT, its translation requires focused development through a close collaboration between engineers and clinicians.

Optical assessment of the in vivo tympanic membrane status using a handheld optical coherence tomography-based otoscope

OBJECTIVE

Conventional otoscopes and oto-endoscopes, which are used to examine the tympanic membrane (TM), do not provide tomographic information. Optical coherence tomography (OCT) non-invasively reveals the depth-resolved internal microstructure of the TM with very high spatial resolution. We designed this study to examine the TMs with middle ear diseases using a handheld otoscope employing 860 nm spectral domain (SD)-OCT, combined with video camera and to demonstrate the clinical applicability of this system.

DESIGN

A total of 120 patients with otologic symptoms were enrolled. TM images were obtained using the handheld OCT-based otoscope (860 nm central wave length, 15 μm axial resolution, 15 μm lateral resolution, and 7 mm scanning range using relay lens). Both OCT and oto-endoscope images were compared according to the clinical characteristics such as perforation, retraction, and postoperative healing process.

RESULTS

The objective grade about the thickness of perforation margins and the accurate information about the extent of TM retraction that was not distinguishable by oto-endoscopic exam could be identified using this system. The postoperative healing process of TMs could be also followed using the OCT device.

CONCLUSION

These analyses from the surgeon-oriented perspective suggest another useful application of the handheld OCT device.

Direct Analysis of Pathogenic Structures Affixed to the Tympanic Membrane during Chronic Otitis Media

Objective To characterize otitis media-associated structures affixed to the mucosal surface of the tympanic membrane (TM) in vivo and in surgically recovered in vitro samples. Study Design Prospective case series without comparison. Setting Outpatient surgical care center. Subjects and Methods Forty pediatric subjects scheduled for tympanostomy tube placement surgery were imaged intraoperatively under general anesthesia. Postmyringotomy, a portable optical coherence tomography (OCT) imaging system assessed for the presence of any biofilm affixed to the mucosal surface of the TM. Samples of suspected microbial infection-related structures were collected through the myringotomy incision. The sampled site was subsequently reimaged with OCT to confirm collection from the original image site on the TM. In vitro analysis based on confocal laser scanning microscope (CLSM) images of fluorescence in situ hybridization-tagged samples and polymerase chain reaction (PCR) provided microbiological characterization and verification of biofilm activity. Results OCT imaging was achieved for 38 of 40 subjects (95%). Images from 38 of 38 (100%) of subjects observed with OCT showed the presence of additional microbial infection-related structures. Thirty-four samples were collected from these 38 subjects. CLSM images provided evidence of clustered bacteria in 32 of 33 (97%) of samples. PCR detected the presence of active bacterial DNA signatures in 20 of 31 (65%) of samples. Conclusion PCR and CLSM analysis of fluorescence in situ hybridization-stained samples validates the presence of active bacteria that have formed into a middle ear biofilm that extends across the mucosal layer of the TM. OCT can rapidly and noninvasively identify middle ear biofilms in subjects with severe and persistent cases of otitis media.

Magnetomotive Displacement of the Tympanic Membrane Using Magnetic Nanoparticles: Toward Enhancement of Sound Perception

OBJECTIVE

A novel hearing-aid scheme using magnetomotive nanoparticles (MNPs) as transducers in the tympanic membrane (TM) is proposed, aiming to noninvasively and directly induce a modulated vibration on the TM.

METHODS

In this feasibility study, iron oxide (Fe₃O₄) nanoparticles were applied on ex vivo rat TM tissues and allowed to diffuse over ∼2 h. Subsequently, magnetic force was exerted on the MNP-laden TM via a programmable electromagnetic solenoid to induce the magnetomotion. Optical coherence tomography (OCT), along with its phase-sensitive measurement capabilities, was utilized to visualize and quantify the nanometer-scale vibrations generated on the TM tissues.

RESULTS

The magnetomotive displacements induced on the TM were significantly greater than the baseline vibration of the TM without MNPs. In addition to a pure frequency tone, a chirped excitation and the corresponding spectroscopic response were also successfully generated and obtained. Finally, visualization of volumetric TM dynamics was achieved.

CONCLUSION

This study demonstrates the effectiveness of magnetically inducing vibrations on TMs containing iron oxide nanoparticles, manipulating the amplitude and the frequency of the induced TM motions, and the capability of assessing the magnetomotive dynamics via OCT.

SIGNIFICANCE

The results demonstrated here suggest the potential use of this noninvasive magnetomotive approach in future hearing aid applications. OCT can be utilized to investigate the magnetomotive dynamics of the TM, which may either enhance sound perception or magnetically induce the perception of sound without the need for acoustic speech signals.

Pneumatic low-coherence interferometry otoscope to quantify tympanic membrane mobility and middle ear pressure

Pneumatic otoscopy to assess the mobility of the tympanic membrane (TM) is a highly recommended diagnostic method of otitis media (OM), a widespread middle ear infection characterized by the fluid accumulation in the middle ear. Nonetheless, limited depth perception and subjective interpretation of small TM displacements have challenged the appropriate and efficient examination of TM dynamics experienced during OM. In this paper, a pneumatic otoscope integrated with low coherence interferometry (LCI) was adapted with a controlled pressure-generating system to record the pneumatic response of the TM and to estimate middle ear pressure (MEP). Forty-two ears diagnosed as normal (n = 25), with OM (n = 10), or associated with an upper respiratory infection (URI) (n = 7) were imaged with a pneumatic LCI otoscope with an axial, transverse, and temporal resolution of 6 µm, 20 µm, and 1 msec, respectively. The TM displacement under pneumatic pressure transients (a duration of 0.5 sec with an intensity of ± 150 daPa) was measured to compute two metrics (compliance and amplitude ratio). These metrics were correlated with peak acoustic admittance and MEP from tympanometry and statistically compared via Welch's t-test. As a result, the compliance represents pneumatic TM mobility, and the amplitude ratio estimates MEP. The presence of a middle ear effusion (MEE) significantly decreased compliance (p<0.001). The amplitude ratio of the OM group was statistically less than that of the normal group (p<0.01), indicating positive MEP. Unlike tympanometry, pneumatic LCI otoscopy quantifies TM mobility as well as MEP regardless of MEE presence. With combined benefits of pneumatic otoscopy and tympanometry, pneumatic LCI otoscopy may provide new quantitative metrics for understanding TM dynamics and diagnosing OM.

Effects of Negative Middle Ear Pressure on Wideband Acoustic Immittance in Normal-Hearing Adults

OBJECTIVES

Wideband acoustic immittance (WAI) measurements are capable of quantifying middle ear performance over a wide range of frequencies relevant to human hearing. Static pressure in the middle ear cavity affects sound transmission to the cochlea, but few datasets exist to quantify the relationship between middle ear transmission and the static pressure. In this study, WAI measurements of normal ears are analyzed in both negative middle ear pressure (NMEP) and ambient middle ear pressure (AMEP) conditions, with a focus on the effects of NMEP in individual ears.

DESIGN

Eight subjects with normal middle ear function were trained to induce consistent NMEPs, quantified by the tympanic peak pressure (TPP) and WAI. The effects of NMEP on the wideband power absorbance level are analyzed for individual ears. Complex (magnitude and phase) WAI quantities at the tympanic membrane (TM) are studied by removing the delay due to the residual ear canal (REC) volume between the probe tip and the TM. WAI results are then analyzed using a simplified classical model of the middle ear.

RESULTS

For the 8 ears presented here, NMEP has the largest and most significant effect across ears from 0.8 to 1.9 kHz, resulting in reduced power absorbance by the middle ear and cochlea. On average, NMEP causes a decrease in the power absorbance level for low- to mid-frequencies, and a small increase above about 4 kHz. The effects of NMEP on WAI quantities, including the absorbance level and TM impedance, vary considerably across ears. The complex WAI at the TM and fitted model parameters show that NMEP causes a decrease in the aggregate compliance at the TM. Estimated REC delays show little to no dependence on NMEP.

CONCLUSIONS

In agreement with previous results, these data show that the power absorbance level is most sensitive to NMEP around 1 kHz. The REC effect is removed from WAI measurements, allowing for direct estimation of complex WAI at the TM. These estimates show NMEP effects consistent with an increased stiffness in the middle ear, which could originate from the TM, tensor tympani, annular ligament, or other middle ear structures. Model results quantify this nonlinear, stiffness-related change in a systematic way, that is not dependent on averaging WAI results in frequency bands. Given the variability of pressure effects, likely related to intersubject variability at AMEP, TPP is not a strong predictor of change in WAI at the TM. More data and modeling will be needed to better quantify the relationship between NMEP, WAI, and middle ear transmission.

Quantitative Pneumatic Otoscopy Using a Light-Based Ranging Technique

Otitis media is the leading cause of hearing loss in children. It is commonly associated with fluid in the ear, which can result in up to 45 dB of hearing loss for extended periods of time during a child's most important developmental years. Accurate assessment of middle ear effusions is an important part of understanding otitis media. Current technologies used to diagnose otitis media with effusion are pneumatic otoscopy, tympanometry, and acoustic reflectometry. While all of these techniques can reasonably diagnose the presence of an effusion, they provide limited information about the infection present behind the tympanic membrane.We have developed a technique based on low-coherence interferometry-a non-invasive optical ranging technique capable of sensing depth-resolved microscopic scattering features through the eardrum-to quantify eardrum thickness and integrity, as well as detect any effusion, purulence, or biofilm behind the tympanic membrane. In this manuscript, the technique is coupled with a pneumatic otoscope to measure minute deflections of the tympanic membrane from insufflation pressure stimuli. This results in quantitative measurements of tympanic membrane mobility, which may be used to gain a better understanding of the impact of infection on the membrane dynamics. A small pilot study of 15 subjects demonstrates the ability of pneumatic low-coherence interferometry to quantitatively differentiate normal ears from ears with effusions present. Analysis of the strengths and weaknesses of the technique, as well as focus areas of future research, is also discussed.

Panel 8: Report on Recent Advances in Molecular and Cellular Biochemistry

Objectives To update the medical literature on recent cellular and molecular advances in otitis media disease models with a principal focus on developments in the past 5 years. We also aim to explain recent translational advances in cellular and molecular biology that have influenced our understanding and management of otitis media. Data Sources PubMed-indexed peer-reviewed articles. Review Methods A comprehensive review of the literature was conducted with the term otitis media and the following search terms: molecular biology, cell biology, innate immunity, oxidative stress, mucins, molecular diagnostics. Included articles were published in the English language from January 1, 2010, to July 31, 2015. Implications for Practice The molecular understanding of otitis media disease progression has rapidly advanced over the last 5 years. The roles of inflammation, mucins, and cell signaling mechanisms have been elucidated and defined. Advances in the field provide a plethora of opportunities for innovative molecular targeting in the development of novel therapeutic strategies for otitis media.