Differential diagnosis of otitis media with effusion using label-free Raman spectroscopy: A pilot study

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.

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.

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.

Multimodal Handheld Probe for Characterizing Otitis Media - Integrating Raman Spectroscopy and Optical Coherence Tomography

Otitis media (OM) is a common disease of the middle ear, affecting 80% of children before the age of three. The otoscope, a simple illuminated magnifier, is the standard clinical diagnostic tool to observe the middle ear. However, it has limited contrast to detect signs of infection, such as clearly identifying and characterizing middle ear fluid or biofilms that accumulate within the middle ear. Likewise, invasive sampling of every subject is not clinically indicated nor practical. Thus, collecting accurate noninvasive diagnostic factors is vital for clinicians to deliver a precise diagnosis and effective treatment regimen. To address this need, a combined benchtop Raman spectroscopy (RS) and optical coherence tomography (OCT) system was developed. Together, RS-OCT can non-invasively interrogate the structural and biochemical signatures of the middle ear under normal and infected conditions.In this paper, in vivo RS scans from pediatric clinical human subjects presenting with OM were evaluated in parallel with RS-OCT data of physiologically relevant in vitro ear models. Component-level characterization of a healthy tympanic membrane and malleus bone, as well as OM-related middle ear fluid, identified the optimal position within the ear for RS-OCT data collection. To address the design challenges in developing a system specific to clinical use, a prototype non-contact multimodal handheld probe was built and successfully tested in vitro. Design criteria have been developed to successfully address imaging constraints imposed by physiological characteristics of the ear and optical safety limits. Here, we present the pathway for translation of RS-OCT for non-invasive detection of OM.

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.

Advancing Raman spectroscopy from research to clinic: Translational potential and challenges

Raman spectroscopy has emerged as a non-invasive and versatile diagnostic technique due to its ability to provide molecule-specific information with ultrahigh sensitivity at near-physiological conditions. Despite exhibiting substantial potential, its translation from optical bench to clinical settings has been impacted by associated limitations. This perspective discusses recent clinical and biomedical applications of Raman spectroscopy and technological advancements that provide valuable insights and encouragement for resolving some of the most challenging hurdles.

Cigarette smoke-induced changes in the murine vocal folds: a Raman spectroscopic observation

Raman spectroscopic methods are being projected as novel tools to study the early invisible molecular level changes in a label-free manner. In the present study, we have used Raman spectroscopy to explore the earliest biochemical changes in murine vocal folds in response to time-bound cigarette smoke exposure. Mice were exposed to cigarette smoke for 2 or 4-weeks through a customized smoke inhalation system. The larynx was collected and initial evaluations using standard methods of analysis such as histopathology and immunofluorescence was performed. Concurrent unstained sections were used for Raman imaging. Two common pathological features of vocal fold disorders including alterations in collagen content and epithelial hypercellularity, or hyperplasia, were observed. The mean spectra, principal component analysis, and Raman mapping also revealed differences in the collagen content and hypercellularity in the smoke exposed tissues. The differences in 2-week exposed tissues were found to be more prominent as compared to 4-week. This was attributed to adaptive responses and the already reported biphasic effects, which suggest that collagen synthesis is significantly reduced at higher cigarette smoke concentrations. Overall findings of the study are supportive of the prospective application of Raman imaging in monitoring changes due to cigarette smoke in the vocal folds.

Towards an Interpretable Classifier for Characterization of Endoscopic Mayo Scores in Ulcerative Colitis Using Raman Spectroscopy

Ulcerative colitis (UC) is one of the main types of chronic inflammatory diseases that affect the bowel, but its pathogenesis is yet to be completely defined. Assessing the disease activity of UC is vital for developing a personalized treatment. Conventionally, the assessment of UC is performed by colonoscopy and histopathology. However, conventional methods fail to retain biomolecular information associated to the severity of UC and are solely based on morphological characteristics of the inflamed colon. Furthermore, assessing endoscopic disease severity is limited by the requirement for experienced human reviewers. Therefore, this work presents a nondestructive biospectroscopic technique, for example, Raman spectroscopy, for assessing endoscopic disease severity according to the four-level Mayo subscore. This contribution utilizes multidimensional Raman spectroscopic data to generate a predictive model for identifying colonic inflammation. The predictive modeling of the Raman spectroscopic data is performed using a one-dimensional deep convolutional neural network (1D-CNN). The classification results of 1D-CNN achieved a mean sensitivity of 78% and a mean specificity of 93% for the four Mayo endoscopic scores. Furthermore, the results of the 1D-CNN are interpreted by a first-order Taylor expansion, which extracts the Raman bands important for classification. Additionally, a regression model of the 1D-CNN model is constructed to study the extent of misclassification and border-line patients. The overall results of Raman spectroscopy with 1D-CNN as a classification and regression model show a good performance, and such a method can serve as a complementary method for UC analysis.

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.

Rapid, quantitative determination of aggregation and particle formation for antibody drug conjugate therapeutics with label-free Raman spectroscopy

Lot release and stability testing of biologics are essential parts of the quality control strategy for ensuring therapeutic material dosed to patients is safe and efficacious, and consistent with previous clinical and toxicological experience. Characterization of protein aggregation is of particular significance, as aggregates may lose the intrinsic pharmaceutical properties as well as engage with the immune system instigating undesirable downstream immunogenicity. While important, real-time identification and quantification of subvisible particles in the monoclonal antibody (mAb) drug products remains inaccessible with existing techniques due to limitations in measurement time, sensitivity or experimental conditions. Here, owing to its exquisite molecular specificity, non-perturbative nature and lack of sample preparation requirements, we propose label-free Raman spectroscopy in conjunction with multivariate analysis as a solution to this unmet need. By leveraging subtle, but consistent, differences in vibrational modes of the biologics, we have developed a support vector machine-based regression model that provides fast, accurate prediction for a wide range of protein aggregations. Moreover, in blinded experiments, the model shows the ability to precisely differentiate between aggregation levels in mAb like product samples pre- and post-isothermal incubation, where an increase in aggregate levels was experimentally determined. In addition to offering fresh insights into mAb like product-specific aggregation mechanisms that can improve engineering of new protein therapeutics, our results highlight the potential of Raman spectroscopy as an in-line analytical tool for monitoring protein particle formation.

Identification of early inflammatory changes in the tympanic membrane with Raman spectroscopy

The tympanic membrane (TM) is a dynamic structure that separates the middle ear from the external auditory canal. It is also integral for the transmission of sound waves. In this study, we demonstrate the feasibility of using Raman spectroscopy to identify early chemical changes resulting from inflammation in the TM that can serve as an indicator of acute otitis media. Bacterial lipopolysaccharide (LPS) was injected trans-tympanicaly in a murine model. Presence of inflammatory response was assessed with binocular microscopy, confirmed with histopathology and immunofluorescence staining. Successful discrimination suggesting spectral differences among the control and LPS treated groups was achieved using principal component analysis. Raman imaging revealed major differences in collagen distribution and nucleic acid content. Image segmentation analysis on the trichrome stained tissue sections was performed to corroborate the Raman spectra. The spectral co-localization study suggests changes in the expression of collagen IV specific signals in LPS treated samples. The overall findings of the study support prospective application of RS in the diagnosis and therapeutic monitoring of otitis media.

Integration of diffraction phase microscopy and Raman imaging for label-free morpho-molecular assessment of live cells

Label-free quantitative imaging is highly desirable for studying live cells by extracting pathophysiological information without perturbing cell functions. Here, we demonstrate a novel label-free multimodal optical imaging system with the capability of providing comprehensive morphological and molecular attributes of live cells. Our morpho-molecular microscopy (3M) system draws on the combined strength of quantitative phase microscopy (QPM) and Raman microscopy to probe the morphological features and molecular fingerprinting characteristics of each cell under observation. While the commonr-path geometry of our QPM system allows for highly sensitive phase measurement, the Raman microscopy is equipped with dual excitation wavelengths and utilizes the same detection and dispersion system, making it a distinctive multi-wavelength system with a small footprint. We demonstrate the applicability of the 3M system by investigating nucleated and nonnucleated cells. This integrated label-free platform has a promising potential in preclinical research, as well as in clinical diagnosis in the near future.