Optical coherence tomography for the diagnosis and evaluation of human otitis media

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.

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.

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.

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.

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.

Investigations on the potential of optical coherence tomography as an imaging tool for eustachian tube

The purpose of this study was to explore the feasibility of eustachian tube optical coherence tomography (ET-OCT) for imaging the pharyngeal region of the eustachian tube (ET). Ten subjects with ear complaints underwent ET-OCT guided by nasal endoscopy, and ET-OCT examination was performed on both sides of each subject's ETs. The process and resulting images were analysed. Ten subjects ranging from 21 to 73 years old (45 ± 14.77) were enrolled in this study. Eighteen ET-OCT imaging examinations were completed. The mean duration of each examination was 2.80 ± 1.62 min (ranging from 2 to 7 min). There were no adverse events or complications. In some subjects, the ET-OCT images clearly presented the microstructures of the ET wall, including the lumen, mucosa, submucosa, cartilage and plica. However, in some subjects, it showed different characteristics, such as an unclear hierarchy and secretions in the lumen. ET-OCT may help to distinguish the structural composition of the ET and elucidate related pathophysiological mechanisms. It is a valuable imaging tool suited for the ET, with potential diagnostic value in determining the morphology of the lumen, intraluminal mucosa and submucosal tissue in the pharyngeal region of the ET.

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.

Advances in Optical Detection of Human-Associated Pathogenic Bacteria

Bacterial infection is a global burden that results in numerous hospital visits and deaths annually. The rise of multi-drug resistant bacteria has dramatically increased this burden. Therefore, there is a clinical need to detect and identify bacteria rapidly and accurately in their native state or a culture-free environment. Current diagnostic techniques lack speed and effectiveness in detecting bacteria that are culture-negative, as well as options for in vivo detection. The optical detection of bacteria offers the potential to overcome these obstacles by providing various platforms that can detect bacteria rapidly, with minimum sample preparation, and, in some cases, culture-free directly from patient fluids or even in vivo. These modalities include infrared, Raman, and fluorescence spectroscopy, along with optical coherence tomography, interference, polarization, and laser speckle. However, these techniques are not without their own set of limitations. This review summarizes the strengths and weaknesses of utilizing each of these optical tools for rapid bacteria detection and identification.

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.

A Tanshinone IIA loaded hybrid nanocomposite with enhanced therapeutic effect for otitis media

Otitis media, commonly known as middle ear inflammation, is among one of the most common maladies and results in significant morbidity such as loss of hearing. In view of the bacteria invasion such as Staphylococcus aureus causes the majority forms of otitis media, drug treatment generally uses antibacterial by topical or systematic approach. However, the effectiveness of antibacterial is diminishing because of the rapid emergence of antibiotic-resistant bacterial strains. Here, we designed and fabricated a silver nanoparticle (AgNPs)-based multicomponent hybrid nanocomposite termed as TSIIA @ CS/Lys @ AgNPs, which was comprised of a AgNPs core, a chitosan (CS) or lysozyme (Lys) middle layer, and a Tanshinone IIA (TSIIA) inclusion outlayer. Coating of CS or Lys to AgNPs through electrostatic interaction probably produced a core-shell nanocomplex resembling the endocarp of walnut. This design could reduce the dosage of AgNPs while maintaining antibacterial activity possibly due to the favorable interactions between nanocomplex and bacteria. The deposition of Chinese herb active component TSIIA by inclusion complexation formed the out layer of hybrid nanocomposite towards an improved antibacterial performance, which showed a therapeutic effect against acute otitis media of guinea pig comparable to the clinical commercial-used ofloxacin administrated by injection. The hybrid nanocomposite, when dispersed in poly (lactic-co-glycolic acid)/N-methyl-2-pyrrolidone (PLGA/NMP) solution as an in-situ organogel, not only maintained the therapeutic effectiveness, but also possessed the advantage of lower injection frequency compared with solution formulation. In addition, no obvious toxicity to the basilar membrane and epithelia tissue was observed after the healthy guinea pigs were treated with hybrid nanocomposite or organogel. This study provides a promising strategy to develop hybrid nanocomposite with enhanced antibacterial efficacy and also opens a new way for the establishment of efficient therapeutic systems with reduced administration frequency as substitute of antibiotics to treat otitis media.

[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.

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.

Revealing the morphology and function of the cochlea and middle ear with optical coherence tomography

Optical coherence tomography (OCT) has revolutionized physiological studies of the hearing organ, the vibration and morphology of which can now be measured without opening the surrounding bone. In this review, we provide an overview of OCT as used in the otological research, describing advances and different techniques in vibrometry, angiography, and structural imaging.

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.

Intraluminal three-dimensional optical coherence tomography - a tool for imaging of the Eustachian tube?

OBJECTIVES

The cause of Eustachian tube dysfunction often remains unclear. Therefore, this study aimed to examine the feasibility and possible diagnostic use of optical coherence tomography in the Eustachian tube ex vivo.

METHODS

Two female blackface sheep cadaver heads were examined bilaterally. Three conditions of the Eustachian tube were investigated: closed (resting position), actively opened and stented. The findings were compared (and correlated) with segmented histological cross-sections.

RESULTS

Intraluminal placement of the Eustachian tube with the optical coherence tomography catheter was performed without difficulty. Regarding the limited infiltration depth of optical coherence tomography, tissues can be differentiated. The localisation of the stent was accurate as was the lumen.

CONCLUSION

The application of optical coherence tomography in the Eustachian tube under these experimental conditions is considered to be a feasible, rapid and non-invasive diagnostic method, with possible diagnostic value for determining the luminal shape and superficial lining tissue of the Eustachian tube.

Observations of in vivo laser tissue ablation in animal models with different chromophores on the skin and modulating duration per laser exposure

Characteristics such as skin tone and pigmentation color vary among patients, but most researches on laser irradiation in laser ablation have revolved around minimizing damage to reduce pain. Chromophores are the most important factors in photon energy absorption, a key principle of laser ablation. We investigated the influences on ablation depth by different chromophores on the target and modulating duration per laser exposure using an Nd:YVO4 nanosecond 532-nm laser. We used a Fourier-domain optical coherence tomography (Fd-OCT) system combined with a 532-nm Nd:YVO4 laser to observe the ablation process. In addition, an external customized shutter and water-based color pens (red, green, blue, black) were used to determine the effects of modulating the duration per laser exposure and coloring chromophores on porcine skin and hairless mouse models. Experiments with modulating duration per laser exposure demonstrated that shorter duration generated shallower craters than longer one. Painted experimental group showed damaged region as craters in the experiments with coloring various chromophores. In this research, we investigated the effects of modulating duration per laser exposure and different chromophores on the target. Coloring chromophores with water-based dyes using pens increased tissue damage without dyeing cells or tissue.

Clinical Utility of Intraoperative Tympanomastoidectomy Assessment Using a Surgical Microscope Integrated with an Optical Coherence Tomography

Significant technical and optical advances are required for intraoperative optical coherence tomography (OCT) to be utilized during otological surgeries. Integrating OCT with surgical microscopy makes it possible to evaluate soft tissue in real-time and at a high resolution. Herein, we describe an augmented-reality, intraoperative OCT/microscope system with an extended working distance of 280 mm, providing more space for surgical manipulation than conventional techniques. We initially performed ex vivo experiments to evaluate system performance. In addition, we validated the system by performing preliminary clinical assessments of tympanomastoidectomy outcomes in six patients with chronic otitis media. The system evaluated residual inflammation in the region-of-interest of the mastoid bone. Most importantly, the system intraoperatively revealed the connection between the graft and the remnant tympanic membrane. The extended working distance allows otological surgeons to evaluate the status of both the mastoid bone and tympanic membrane during manipulation, affording full intraoperative imaging.

Multiple Wavelength Optical Coherence Tomography Assessments for Enhanced Ex Vivo Intra-Cochlear Microstructural Visualization

The precise identification of intra-cochlear microstructures is an essential otorhinolaryngological requirement to diagnose the progression of cochlea related diseases. Thus, we demonstrated an experimental procedure to investigate the most optimal wavelength range, which can enhance the visualization of ex vivo intra-cochlear microstructures using multiple wavelengths (i.e., 860 nm, 1060 nm, and 1300 nm) based optical coherence tomography (OCT) systems. The high-resolution tomograms, volumetric, and quantitative evaluations obtained from Basilar membrane, organ of Corti, and scala vestibule regions revealed complementary comparisons between the aforementioned three distinct wavelengths based OCT systems. Compared to 860 nm and 1300 nm wavelengths, 1060 nm wavelength OCT was discovered to be an appropriate wavelength range verifying the simultaneously obtainable high-resolution and reasonable depth range visualization of intra-cochlear microstructures. Therefore, the implementation of 1060 nm OCT can minimize the necessity of two distinct OCT systems. Moreover, the results suggest that the performed qualitative and quantitative analysis procedure can be used as a powerful tool to explore further anatomical structures of the cochlea for future studies in otorhinolaryngology.

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

Otitis media with effusion (OME) is an important and common condition affecting hearing in pediatric patients characterized by the presence of fluid in the middle ear space. The fluid is normally described as serous or mucoid based on differences in the fluid viscosity. The differential diagnosis of two OMEs, namely serous and mucoid is of significant clinical value because while the former is self-limiting, surgical procedure is commonly required for the latter. However, accurate identification of fluid types remains a challenging target unattainable with current clinical modalities due to unavailability of nonperturbative molecular tools. Here, we report an emerging spectroscopy approach featuring Raman scattering and multivariate analysis of spectral patterns to discern serous and mucoid fluids, obtained from pediatric patients undergoing myringotomy and tube placement, by providing information of differentially expressed molecules with high specificity. We demonstrate the feasibility of Raman spectroscopy-based approach to categorize middle ear effusion based on the characteristic spectral markers, notably of mucin, with classification accuracy of 91% and 93% for serous and mucoid, respectively. Our findings pave the way for further development of such a tool for fully noninvasive application that will lead to objective and accurate diagnosis thereby reducing unnecessary visits and surgical procedures.

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.

In Vivo Non-Destructive Monitoring of Capsicum Annuum Seed Growth with Diverse NaCl Concentrations Using Optical Detection Technique

We demonstrate that optical coherence tomography (OCT) is a plausible optical tool for in vivo detection of plant seeds and its morphological changes during growth. To investigate the direct impact of salt stress on seed germination, the experiment was conducted using Capsicum annuum seeds that were treated with different molar concentrations of NaCl. To determine the optimal concentration for the seed growth, the seeds were monitored for nine consecutive days. In vivo two-dimensional OCT images of the treated seeds were obtained and compared with the images of seeds that were grown using sterile distilled water. The obtained results confirm the feasibility of using OCT for the proposed application. Normalized depth profile analysis was utilized to support the conclusions.

Non-Destructive Analysis of the Internal Anatomical Structures of Mosquito Specimens Using Optical Coherence Tomography

The study of mosquitoes and analysis of their behavior are of crucial importance in the on-going efforts to control the alarming increase in mosquito-borne diseases. Furthermore, a non-destructive and real-time imaging technique to study the anatomical features of mosquito specimens can greatly aid the study of mosquitoes. In this study, we demonstrate the three-dimensional imaging capabilities of optical coherence tomography (OCT) for structural analysis of Anopheles sinensis mosquitoes. The anatomical features of An. sinensis head, thorax, and abdominal regions, along with the morphology of internal structures, such as foregut, midgut, and hindgut, were studied using OCT imaging. Two-dimensional and three-dimensional OCT images, used in conjunction with histological images, proved useful for anatomical analysis of mosquito specimens. By presenting this work as an initial study, we demonstrate the applicability of OCT for future mosquito-related entomological research, and also in identifying changes in mosquito anatomical structure.

Anti-confocal assessment of middle ear inflammation

To improve the diagnostic prediction of recurrence of otitis media with effusion after surgery, an anti-confocal system combined with spectroscopic measurements is proposed to reject unwanted signals from the eardrum and assess the blood content. The anti-confocal system was experimentally evaluated on both optical middle ear phantom and human skin. Results showed effective rejection of signals from the eardrum using a central stop replacing the confocal pinhole, while still detecting signals from the middle ear mucosa. The system is sensitive to changes in blood content, but scattering and absorption characteristics of the eardrum can distort the measurement. Confocal detection of eardrum properties was shown to be a promising approach to correct measurements.

Fast Industrial Inspection of Optical Thin Film Using Optical Coherence Tomography

An application of spectral domain optical coherence tomography (SD-OCT) was demonstrated for a fast industrial inspection of an optical thin film panel. An optical thin film sample similar to a liquid crystal display (LCD) panel was examined. Two identical SD-OCT systems were utilized for parallel scanning of a complete sample in half time. Dual OCT inspection heads were utilized for transverse (fast) scanning, while a stable linear motorized translational stage was used for lateral (slow) scanning. The cross-sectional and volumetric images of an optical thin film sample were acquired to detect the defects in glass and other layers that are difficult to observe using visual inspection methods. The rapid inspection enabled by this setup led to the early detection of product defects on the manufacturing line, resulting in a significant improvement in the quality assurance of industrial products.