Optical Coherence Tomography of the Head and Neck
Number: 0928
Table Of Contents
PolicyApplicable CPT / HCPCS / ICD-10 Codes
Background
References
Policy
Scope of Policy
This Clinical Policy Bulletin addresses optical coherence tomography of the head and neck.
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Experimental, Investigational, and Unproven
Aetna considers the following procedures experimental, investigational, or unproven because the effectiveness of these approaches has not been established:
- Annual optical coherence tomography (OCT) for the follow-up of thyroid ophthalmopathy after orbital decompression
- Dynamic OCT for evaluation of actinic keratosis
- Endoscopic OCT for evaluation of tympanoplasty
- Intra-operative wide-field OCT for analysis of deep margins in head and neck surgery
- OCT angiography (OCTA) for the detection of subclinical features of low perfusion in individuals with giant cell arteritis without a manifest ocular involvement
- OCTA for detection of thyroid-associated ophthalmopathy
- OCT for assessment and management of the middle ear
- OCT for diagnosis of oral cancerous lesion
- OCT for evaluation of voice disorders
- OCT otoscope (e.g., OtoSight Middle Ear Scope and TOMi Scope) for imaging of tympanic membrane and middle ear pathology.
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Related Policies
- CPB 0344 - Optic Nerve and Retinal Imaging Methods - for OCT for retinal disorders
- CPB 0749 - Anterior Segment Scanning Computerized Ophthalmic Diagnostic Imaging
- CPB 0829 - Intra-vascular Optical Coherence Tomography
- CPB 0886 - Optical Coherence Tomography and Microelastography for Solid Tumors and Other Selected Indications
Background
Optical coherence tomography (OCT) is a non-invasive, non-contrast imaging technology which uses near-infrared light to produce high-resolution cross-sectional images. OCT was developed as a technique enabling high-resolution, real-time and in-situ imaging of tissue microstructure without the need for tissue excision and processing (Popescu, 2011). OCT technology is now emerging as a diagnostic tool for imaging the auditory system. Analogous to ultrasound by measuring the intensity of infrared light rather than acoustical waves, it is suggested that OCT could be a useful tool to see through the tympanic membrane into the middle ear without requiring surgical manipulation, and to help diagnose diseases associated with the tympanic membrane and middle ear (Cho et al, 2015; Pitris et al, 2001).
Monroy et al (2017) conducted a prospective observational case series in which optical coherence tomography (OCT) tracking was used to observe 25 pediatric patients diagnosed with chronic or recurrent otitis media perioperatively. Patients were followed before and throughout their treatment. Following OCT imaging, patient records were observed for an additional 6 months in follow-up. At each time-point (pre-operative, intra-operative, post-operative), the tympanic membrane (at the light reflex region) and directly adjacent middle-ear cavity were observed in vivo with a handheld OCT probe and portable system. Imaging results were compared with clinical outcomes to correlate the clearance of symptoms in relation to changes in the image-based features of infection. OCT images of most all participants showed the presence of additional infection-related biofilm structures during their initial consultation visit and similarly for patients imaged intraoperatively before myringotomy. Patients with no recurrence of infectious symptoms had no additional structures visible in OCT images during the postoperative visit. OCT image findings suggest surgical intervention consisting of myringotomy and tympanostomy tube placement provides a means to clear the middle ear of infection-related components, including middle-ear fluid and biofilms. Furthermore, the authors concluded that OCT was demonstrated as a rapid diagnostic tool to prospectively monitor patients in both outpatient and surgical settings.
Park et al (2017) conducted a prospective study to examine the tympanic membranes (TMs) of 120 patients with middle ear conditions using a handheld optical coherence tomography-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. 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. The authors concluded that their findings suggest that the handheld OCT device would be another useful application.
Cho et al (2015) report on the application of optical coherence tomography (OCT) for the diagnosis and evaluation of otitis media (OM). They evaluated 39 patients who were diagnosed with OM via standard oto-endoscopic examination and audiological tests between July and October 2012. Six volunteers with normal tympanic membrane (TM) on oto-endoscopy were also included, with OCT images used as a control. Of the 39 patients, OCT images were acquired from 16 patients (41.0 %). The most common cause of failure to acquire an image was a narrow or curved external auditory canal (n = 5). Other causes were the presence of obstacles, such as profuse otorrhea (n = 3), cholesteatoma material (n = 4), and cerumen (n = 7), and poor compliance (n = 4). OCT could not be obtained for the three patients with chronic OM with cholesteatomas. Despite the benefits such as non-invasiveness, lack of radiation, high resolution and ability to use outpatient, the authors report some limitations, such as, difficulty securing a light pathway for the OCT device, and the diagnostic efficiency of oto-endoscopy. The authors concluded that their evaluation suggests that a handheld OCT otoscope can be applied clinically to otology, and that OCT has the potential to facilitate diagnosis of OM; however, further clinical trials are needed.
MacDougall et al (2015) state that optical coherence tomography (OCT) for imaging the middle ear can present some challenges for real-time clinical use. Although OCT is noninvasive, the challenges included the need to work at a low numerical aperture, the deleterious effects of trans-tympanic imaging on image quality at the ossicles, sensitivity requirements for clinical fidelity of images at real-time rates, and the high dynamic-range requirements of the ear. (Abstract only)
Nguyen et al (2013) investigated the acoustic effects of bacterial biofilms, confirmed using optical coherence tomography (OCT), in adult ears. Biofilms have been linked to chronic otitis media (OM) and OM with effusion in the middle ear. Non-invasive OCT images were collected to visualize the 2D cross-sectional structure of the middle ear, verifying the presence of a biofilm behind the TM of 5 ears. Wideband measurements of acoustic reflectance and impedance (0.2 to 6 [kHz]) were used to study the acoustic properties of ears with confirmed bacterial biofilms. Compared to known acoustic properties of normal middle ears, each of the ears with a bacterial biofilm had an elevated power reflectance in the 1 to 3 [kHz] range, corresponding to an abnormally small resistance. The authors note that their preliminary study indicates that acoustic reflectance and impedance measurements may have utility for assessment of the presence and acoustic impact of biofilms in the middle ear; however, future study of a wide range of OM-related conditions, with definitive biofilm and non-biofilm classifications, is needed.
UpToDate reviews on “Evaluation and management of middle ear trauma” (Evans and Handler, 2017), “Acute otitis media in adults” (Limb et al., 2017), “Acute otitis media in children: Diagnosis” (Wald, 2017), and “Eustachian tube dysfunction” (Poe and Hanna, 2016) do not mention use of optical coherence tomography for diagnosis or management.
In a prospective, case-series study, Monroy and colleagues (2018) characterized OM-associated structures affixed to the mucosal surface of the tympanic membrane (TM) in-vivo and in surgically recovered in-vitro samples. A total of 40 pediatric subjects scheduled for tympanostomy tube placement surgery were imaged intra-operatively under general anesthesia. Post-myringotomy, a portable 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 re-imaged 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 (FISH)-tagged samples and polymerase chain reaction (PCR) provided microbiological characterization and verification of biofilm activity; 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; 34 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. The authors concluded that PCR and CLSM analysis of FISH-stained samples validated the presence of active bacteria that have formed into a middle ear biofilm that extended across the mucosal layer of the TM. Moreover, these researchers stated that in the future, OCT could be used to rapidly and quantitatively assess for the presence of a middle ear biofilm without invasive sampling, as in the primary care office. This capability allows for the longitudinal tracking of middle ear biofilms, specifically their formation and resolution at different stages of OM and when exposed to existing or newly developed pharmacologic or surgical treatment strategies. The OCT system provided an imaging depth up to approximately 2 mm into tissue, even semi-transparent or highly scattering tissues such as the TM. This capability allowed cross-sectional depth-resolved visualization and quantification of the TM and any adjacent structure in the middle ear cavity (MEC). Since the middle ear mucosa (MEM) is known to support biofilms, these researchers are developing a swept-source OCT system to provide visualization of deeper structures within the MEC, up to a centimeter or more, including the ossicles and the MEM.
The authors stated that this study had several limitations. First, there was no control group. No TM mucosa samples were collected for analysis from healthy pediatric subjects undergoing non-OM-related surgeries. However, it was previously demonstrated that normal ears have no biofilms on the MEM. Other studies similarly reported that normal ears lack biofilm-related structures, as shown in a rat model with a combination of OCT and histology and in normal adult and pediatric ears with OCT. Second, prior to sample collection, the MEC was not aspirated to remove any effusion, and samples were not washed before being placed in fixative. Given the numerous FISH processing steps, it was unlikely that an effusion had any significant effect on these results. Moreover, positive CLSM images were evaluated by consistent and repeated fluorescent signal embedded within the biofilm matrix, not from the exterior of the structure. Aspiration of any middle ear effusion (MEE) before imaging and sampling may also inadvertently remove biofilm material and confound sample collection. Third, it was possible that some samples, once divided for PCR and FISH/CLSM, did not have active bacterial populations. However, it was likely that in other samples, the amount of genetic material for analysis was simply limited. Some recovered samples were small (approximately 1 mm3), and no additional culturing to expand bacterial concentration was performed. While FISH results were able to identify single bacteria, PCR requires a minimum amount of genetic material, which may explain why some samples had no identifiable bacteria. Furthermore, this study analyzed the 3 most common bacterial species known to cause OM, although many other bacterial strains have been identified. Thus, these factors may explain why some samples did not confirm the hypothesis with combined PCR and CLSM/FISH imaging results. However, when sufficient genetic material was present for 1 or both techniques, the resulting measurements were not degraded by the heterogeneous composition of these samples, which can include white and red blood cells, MEE fluid, other bacteria, and cell and biofilm fragments.
Tan and associates (2018) evaluated the recent developments in OCT for TM and middle ear imaging and identified what further development is needed for the technology to be integrated into common clinical use. Data sources included PubMed, Embase, Google Scholar, Scopus, and Web of Science. 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". These investigators stated that conventional imaging techniques cannot adequately resolve the microscale features of TM and middle ear, sometimes necessitating diagnostic exploratory surgery in challenging otologic pathology. As a high-resolution non-invasive imaging technique, OCT offers promise as a diagnostic aid for otologic conditions, such as OM, cholesteatoma, and conductive hearing loss. Using OCT vibrometry to image the nanoscale vibrations of the TM and middle ear 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. These researchers stated that 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 (CT) and magnetic resonance imaging (MRI). While such technology has been available for OCT, its translation requires focused development through a close collaboration between engineers and clinicians.
Jeon and co-workers (2019) noted that Doppler OCT (DOCT) is useful for both, the spatially resolved measurement of the TM oscillation and high-resolution imaging. These investigators demonstrated a new technique capable of providing real-time two-dimensional (2D) Doppler OCT image of rapidly oscillatory latex mini-drum and in-vivo rat TM and ossicles. Using DOCT system, the oscillation of sample was measured at frequency range of 1- to 4-kHz at an output of 15 W. After the sensitivity of the DOCT system was verified using a latex mini-drum consisting of a 100 μm-thick latex membrane, changes in displacement of the umbo and contacted area between TM and malleus in normal and pathologic conditions were measured. The oscillation cycles of the mini-drum for stimulus frequencies were 1.006 kHz for 1-kHz, 2.012 kHz for 2-kHz, and 3.912 kHz for 4-kHz, which meant that the oscillation cycle of the mini-drum became short in proportional to the frequency of stimuli. The oscillation cycles of umbo area and the junction area in normal TM for frequencies of the stimuli showed similar integer ratio with the data of latex mini-drum for stimuli less than 4-kHz. In the case of MEM condition, the Doppler signal showed a tendency of attenuation in all frequencies, which was prominent at 1-kHz and 2-kHz. The TM vibration under sound stimulation with frequencies from 1-kHz to 4-kHz in normal and pathologic conditions was demonstrated using signal demodulation method in in-vivo condition. The OCT technology could be helpful for functional and structural assessment as an optional modality. This preliminary study used a signal de-modulation method to demonstrate TM vibration under sound stimulation at frequencies of 1-, 2-, and 4-kHz in a normal ear and an ear under simulated pathological condition in-vivo and implemented three-dimensional (3D) reconstruction of the TM vibration under sound stimulation. The difference between the oscillation pattern at low-frequency and high-frequency was identified, but further study is needed to validate this method and its results. These researchers stated that they will conduct detailed studies on abnormal models and further animal and human experiments.
Monroy and colleagues (2019) stated that the diagnosis and treatment of OM 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, 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. These investigators presented a flexible and comprehensive framework that automatically extracts features from OCT images, classifies data, and presents clinically relevant results in a user-friendly platform suitable for point-of-care (POC) 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 MEM. Predicted future performance of this classification platform returned promising results (90 %+ accuracy) in various initial tests. The authors stated that 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.
These researchers stated that “Currently, there is no accepted method to identify the presence of middle ear biofilms (MEBs), although it is likely that biofilms increase the opacity of the TM during infection. In this study, the development of the “Normal”, “Biofilm”, and “Fluid and Biofilm” states was made possible by observing the image-based features in OCT data in this and past studies. It was observed that subjects with more severe cases of OM have MEF in addition to an accompanying MEB. This raises additional questions about the pathogenesis of MEB during OM; questions that are beyond the scope of this present study. OCT, however, could be one tool that provides a quantitative identification of biofilms and fluid, and in addition, provide further characterization of the purulence or scattering of the fluid. In this and prior studies, it is common to identify a biofilm layer and middle ear fluid in subjects with more severe cases of OM. As infections progress, any MEF becomes more purulent and optically scattering, depending on the duration of the infection. This is likely due to increasing amounts of immune cell activity and biofilm dispersal within the MEC. Clinicians do not currently diagnose or treat middle ear biofilms as there is no accepted diagnostic tool, nor established or tested/verified treatment regimen. With these limitations in mind, this platform may offer the immediate potential to identify the presence of MEF and MEB, as well as enable new and expanded capabilities in the future. The use of machine learning (ML) analysis to classify OCT images from subjects with OM can provide a means to automatically classify data and provide a probable diagnostic outcome. When an image is successfully collected, a combined OCT + ML platform could ensure the user would have a minimum baseline skill for detecting diagnostic markers for OM. In its current form, this platform is intended to supplement the assessment of the numerous quantitative details within the data and apparent in tissue, and integrate statistical measures to help guide decision making. In turn, with an accurate diagnosis, it may then be possible to provide the most appropriate and effective treatment for the current state of infection. This platform is not intended to replace clinical expertise, but offers the potential for further research and clinical investigations before being validated as an approved technology for clinical decision making”.
Oh and colleagues (2020) examined if OCT provides useful information regarding the micro-structures of the middle and inner ear via the extra-tympanic approach and thereby could be utilized as an alternative diagnostic technology in ear imaging. A total of 5 rats and mice were included, and the swept-source OCT system was used 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. 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. The authors concluded that OCT has been shown a promising technology to evaluate real-time middle and inner ear microstructures non-invasively with a high-resolution in the animal model; thus, OCT could be used to provide additional diagnostic information regarding the diseases of the middle and inner ear.
In a cross-sectional study, Preciado and co-workers (2020) examined the feasibility of detecting and differentiating middle ear effusions (MEEs) using an OCT otoscope. A total of 70 pediatric patients undergoing tympanostomy tube placement were pre-operatively imaged using an OCT otoscope. A blinded reader quiz was conducted using 24 readers from 4 groups of tiered medical expertise. The primary outcome was reader ability to detect presence/absence of MEE; a secondary outcome was reader ability to differentiate serous versus non-serous MEE. 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-/inter-reader agreement of 92.9 % and 87.1 %, respectively. Differentiating MEE type, reader identification of non-serous MEE had 70.8 % accuracy, 53.6 % sensitivity, 80.1 % specificity, and intra-/inter-reader agreement of 82.9 % and 75.1 %, respectively. Multi-variate 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 = 0.0028). The ability to capture quality images improved over time, from 50 % to 69.4 % over the study period. The authors concluded that OCT otoscopy showed 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.
Prasad and colleagues (2020) summarized the literature regarding clinical and pre-clinical imaging techniques used for optical identification of middle ear infections. Clinical methods of examining infections using a conventional otoscope, tympanometry, and OCT were discussed along with their advantages and limitations. The list of clinical trial further presented the current medical devices used to diagnose middle ear infections. Furthermore, novel pre-clinical approaches and information on non-invasive Raman spectroscopy techniques for the detection of middle ear infection were presented to provide an outline of the current literature and to create a guideline for future progress. The authors concluded that although these non-invasive techniques are promising, future work should be directed to conducting clinical trials for these emerging imaging techniques to combat the suspected inefficiency in the current otologic diagnosis and help with the accurate treatment of middle ear infection decision-making.
Byun and colleagues (2021) noted that imaging the Eustachian tube is challenging because of its complex anatomy and limited accessibility. These researchers fabricated a fiber-based OCT catheter and examined its potential for evaluating the Eustachian tube anatomy. A customized OCT system and an imaging catheter, termed the Eustachian OCT, were developed for visualizing the Eustachian tube. Three male swine cadaver heads were used to study OCT image acquisition and for subsequent histologic correlation. The imaging catheter was introduced via the nasopharyngeal opening and reached toward the middle ear. The OCT images were acquired from the superior to the nasopharyngeal opening before and after Eustachian tube balloon dilatation. The histological anatomy of the Eustachian tube was compared with corresponding OCT images. The new, Eustachian OCT catheter was successfully inserted in the tubal lumen without damage. Cross-sectional images of the tube were successfully obtained, and the margins of the anatomical structures including cartilage, mucosa lining, and fat could be successfully delineated. After balloon dilatation, the expansion of the cross-sectional area (CSA) could be identified from the OCT images. The authors concluded that the use of the OCT technique to evaluate the Eustachian tube anatomy was shown to be feasible, and the fabricated OCT image catheter was determined to be suitable for Eustachian tube assessment. These researchers expect the fabrication of the Eustachian OCT catheter to be an initial step in the clinical application of OCT in Eustachian tube assessment.
Won and associates (2021) stated that 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, OCT has been integrated into a hand-held imaging probe. This system can non-invasively and quantitatively evaluate 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. These researchers presented a briefcase OCT system implemented with a real-time machine learning (ML) 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 demonstrated that the briefcase OCT system coupled with machine learning could provide user-invariant classification results of middle ear conditions, which may greatly improve the use of this technology for the diagnosis and management of middle ear infections.
The authors stated that this study had several drawbacks. In general, the processing power and memory of the laptop were limiting factors in the speed of OCT processing and display, as well as for the ML classifier. Note that all the hardware and optical components used in the system were off-the-shelf products. Implementing graphic processing units (GPUs) will further accelerate the speed of the system. With emerging technologies and products in compact OCT waveguides that integrate a light source and detector, the size of the system can be further reduced in the future. As the briefcase system did not use a lateral scanning element to generate B-mode images of the middle ear, the measurements can be affected by the spatial locations of the focused beam on the tympanic membrane (TM). Implementing a compact lateral scanning mechanism using a microelectromechanical systems (MEMS)-based mirror can reliably provide lateral information, which would aid in minimizing the spatial dependence of the measurements. This may further improve the usability and system performance. In the future, with a larger database and an improved model, hyperparameter tuning will be carried out to compare different ML models. This model has been internally validated and examined using the leave-one-out cross-validation method. External validation was limited due to the small size of the dataset. With the increasing number of ear OCT images and datasets in the future, the model will be further improved by external validation using a held-out, independent dataset. The spatial dependence of measurements from the TM can also be overcome with an improved ML classifier (e.g., the dataset of OCT images containing different regions on the TM can be obtained and trained in the ML classifier). OCT images with various image artifacts (mirror artifacts, flipped image and strong reflections) can also be collected and included in the training dataset. This would exclude the measurements with artifacts and could potentially guide the users to avoid these artifacts during imaging. It was also observed that the novice users heavily relied on the surface images of the TM to guide and focus the laser beam during the imaging. In the future, a CCD camera with a higher resolution, a larger field-of-view and a greater depth-of-focus to capture the entire TM will be helpful for users without prior knowledge of OCT. The surface images of the TM were not included in the classifier, as the properties of the CCD images (i.e., lighting, field-of-view, depth-of-focus and resolution) from the briefcase system were different from the trained otoscopy images in the previously developed classifier. With greater computing power in the future, providing the surface images of the TM to the classifier may enhance the classification accuracy. Finally, having rigid time constraints to image patients’ ears in a busy clinical environment may have resulted in suboptimal image quality in some cases. While trained users without prior experience of OCT and otoscopy attempted to image the subjects diagnosed with OM, not all users were successful to acquire reliable datasets because of the given time constraints. Allowing for a longer imaging time window with more training and practice will improve image quality. A larger number of subjects diagnosed with OM are needed in future clinical studies to better characterize the clinical significance and accuracy of the system. Furthermore, this study only recruited adult subjects because participants needed to be tolerant to allow 3 different users to image their ears. A future study will include pediatric subjects as well and examine differences that may emerge in this patient population. Lastly, more researchers are needed to correlate and examine the dataset, ground truth, and the label, to determine the diagnostic importance of AI-assisted OCT otoscopy in clinical practice.
Lui et al (2021) described an OCT and vibrometry system designed for portable hand-held usage in the otology clinic on awake patients. The system provides clinically relevant POC morphological imaging with 14 to 44 µm resolution and functional vibratory measures with sub-nanometer sensitivity. These researchers examined various new approaches for extracting functional information including a multi-tone stimulus, a continuous chirp stimulus, and alternating air and bone stimulus. They also examined the vibratory response over an area of the TM and generated TM thickness maps. The authors concluded that these findings suggested that the system could provide real-time in-vivo imaging and vibrometry of the ear and could prove useful for investigating otologic pathology in the clinic setting. Moreover, these investigators stated that the clinical utility of this device will require validation in large patient populations; and follow-up studies are needed to demonstrate the effectiveness of OCT in the clinic to detect and diagnose middle ear pathology.
Golabbakhsh et al (2023) noted that OCT is an emerging imaging modality that is non-invasive, can be used in-vivo, and can record both anatomy and vibrations. These researchers examined the use of finite-element (FE) modeling to OCT data. They recorded vibrations for 3 human cadaver MEs using OCT. These researchers also had X-ray micro-CT images from the same ears. A total of 3 FE models were built based on geometries obtained from the micro-CT images. The material properties and boundary conditions of the models were obtained from previously reported studies. TM vibration patterns were computed for the 3 models and compared with the patterns measured using OCT. Frequency responses were also computed for all 3 models for several locations in the ME and compared with the OCT displacements and with the literature. The 3 models were compared with each other in terms of geometry and function. Parameter sensitivity analyses were performed, and the results were compared among the models and with the literature. The simulated TM displacement patterns were qualitatively similar to the OCT results. The simulated displacements were closer to the OCT results for 500-Hz and 1-kHz; however, the differences were greater at 2-kHz. The authors concluded that the findings of this study provided an initial look at the combined use of OCT measurements and FE modeling based on subject-specific anatomy. The geometries and parameters of the existing FE models could be modified for individual patients in the future to aid in identifying abnormalities in the ME.
Meenderink et al (2023) stated that current clinical tests for ME injuries and related conductive hearing loss (CHL) are lengthy and costly, lacking the ability to non-invasively examine both structure and function in real time. Optical coherence tomography provides both; however, its use in the audiological setting is currently limited. These researchers adapted and employed a commercial spectral-domain OCT (SD-OCT) to examine anatomy and sound-evoked vibrations of the TM and ossicles in the human ME. SD-OCT was used to capture high-resolution 3D ME images and measure sound-induced vibrations of the TM and ossicles in fresh human temporal bones. 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 evaluate CHL. The authors adapted a commercial SD-OCT to visualize the anatomy and function of the human ME. These researchers stated that OCT has the potential to revolutionize POC evaluation of ME disruptions that result in CHL, which are otherwise indistinguishable via otoscopy.
Endoscopic OCT for the Evaluation of Tympanoplasty Outcome
Morgenstern and associates (2020) noted that after tympanoplasty, it is often challenging to differentiate between different causes of a remaining air bone gap (ABG); OCT offers a new approach for combined morphologic and functional measurements of the tympanic membrane and adjacent parts of the middle ear. It provides diagnostic information in patients with a reduced sound transfer after middle ear surgery. In this single-case study, a patient with history of tympanoplasty and a persistent ABG was examined with endoscopic OCT prior to revision surgery. The oscillation behavior and the thickness of the reconstructed tympanic membrane was determined. The oscillation amplitudes of the inserted prosthesis were compared to a finite element model simulation and to the clinical findings and the audiometric data of the patient. OCT measurements showed a reduced oscillation amplitude of the prosthesis while revealing an aerated middle ear and good coupling of the prosthesis. Transfer loss measured by OCT showed a similar progression as the ABG measured by pure-tone audiometry with a mean divergence of 4.45 dB. The authors concluded that endoscopic OCT is a promising tool for the evaluation of tympanoplasty outcome; it supports established otologic diagnostics and could aid in differentiating between different causes of conductional hearing loss.
Optical Coherence Tomography for Evaluation of Voice Disorders
Benboujja and Hartnick (2021) stated that identifying distinct normal extracellular matrix (ECM) features from pathology is of the upmost clinical importance for laryngeal diagnostics and therapy. Despite remarkable histological contributions, the understanding of the vocal fold (VF) physiology remains murky. The emerging field of non-invasive 3D optical imaging may be well-suited to unravel the complexity of the VF microanatomy. These researchers characterized the entire VF ECM in length and depth with optical imaging. A quantitative morphometric evaluation of the human VF lamina propria using two-photon excitation fluorescence (TPEF), second harmonic generation (SHG), and OCT was examined. Fibrillar morphological features, such as fiber diameter, orientation, anisotropy, waviness and 2nd-order statistics features were evaluated and compared according to their spatial distribution. The evidence acquired in this study suggested that the VF ECM is not a strict discrete 3-layer structure as traditionally described but instead a continuous assembly of different fibrillar arrangement anchored by predominant collagen transitions zones. These investigators demonstrated that the ECM composition was distinct and markedly thinned in the anterior 1/3 of itself, which may play a role in the development of some laryngeal diseases. These researchers further examined and extracted the relationship between OCT and multi-photon imaging, promoting correspondences that could lead to accurate 3D mapping of the VF architecture in real-time during phono-surgeries. As miniaturization of optical probes is consistently improving, a clinical translation of OCT imaging and multi-photon imaging, with valuable qualitative and quantitative features, may have significant implications for treating voice disorders. Moreover, these researchers stated that further investigations are needed, such as performing real-time imaging while applying a deformation on the laryngeal structure, mimicking stress involved during phonation.
The authors stated that this study had several drawbacks. First, the number of specimens in this study was limited and did not highlight differences between age and gender, as previously reported by histological studies. Although OCT acquisitions were carried out on intact dissected larynges, multi-photon imaging acquisitions were acquired on cross-sections, subject to dehydration and fixation artifacts that inevitably affected the morphological and mechanical features of the VF. A possible solution would be to image the VF without sectioning; however, this would limit the penetration depth to 250 to 400 μm, but should still be sufficient to access the superficial lamina propria and perhaps the superior transition of the vocal ligament. Furthermore, this study did not differentiate between collagen fiber types (type I and III to VI) present in the lamina propria, which may be helpful to expose lesions and/or post-scar formation. Ongoing investigations are examining extracting collagen fiber types via a susceptibility tensor analysis with a polarization-resolved SHG microscope, and combining outcomes to a birefringence analysis using polarization-sensitive OCT. These investigators anticipated that the spatial arrangement of entangled collagen fibers will generate a different gradient of birefringence. The system sensitivity in OCT (roll-off effect) is an important factor in estimating the attenuation coefficients. The system used in this study (VCSEL) has a long coherence length and can maintain its sensitivity at greater than 100 dB over a large imaging depth. Considering that the imaging window was within 2 mm, the effect of roll-off was negligible. However, as previously reported, a calibration tool would be a valuable adjunct to improve data analysis and longitudinal or multi-center comparison. The authors stated that despite the small sample size, it was apparent that predicting surgical outcomes and optimizing voice therapy is contingent on a proper evaluation of the microscopic LP features. It would be interesting to combine relevant pixel-based, A-Line-based, and layer-based features with a machine learning classifier for automatic recognition of the LP regions. This study reported the 1st quantitative assessment of the entire vocal fold ECM using multi-photon and OCT. They stated that future biomechanical investigations may take advantage of those parameters to characterize and quantify the impact of stain-stiffness experiments on collagen fibers at global and local levels in real-time. Furthermore, as pathophysiology plays a role in the re-modeling of the lamina propria, those quantitative values and features may help understand the etiology of some benign and malignant lesions.
Diagnosis of Oral Cancerous Lesion
Gambino et al (2023) noted that several investigators described the use of OCT to detect the structural changes of the epithelia involved by the oral potentially malignant disorders (OPMDs). In a case-series study, these researchers provided a suggestion for interpretation of OCT images from different OPMDs, compared to OCT images of healthy tissues. A total of 11 OPMDs patients was recruited and analyzed with OCT. The images obtained were then compared with an OCT repertoire image. In this study, the reflectance degree was considered, together with the analysis of the increased/decreased thicknesses of the various layers: Keratin layer (KL), epithelial layer (EP), lamina propria (LP), basal membrane (BM) assessment, for each lesion, was carried out. OCT measurements of KL, EP and LP layers, together with BM assessing, should aid physicians in recognizing and describing different oral lesions, relating them to the corresponding oral pathology. The authors concluded that further investigations using larger samples are needed to validate the precise values of the thicknesses of different epithelial layers during OCT evaluation to obtain more significant results with reference to the specific sites of the various districts of the oral mucosa.
AngioPlex Optical Coherence Tomography Angiography (OCTA) for Evaluation of Diabetic Non-Proliferative Retinopathy and Hypertensive Retinopathy
Johannesen et al (2019) employed OCT angiography (OCTA) to examine foveal microvascular changes in diabetes by comparing the area of foveal avascular zone (FAZ) in healthy controls and patients with diabetes with no diabetic retinopathy (NDR) as well as different stages of diabetic retinopathy (DR). These researchers carried out a systematic literature search based on the population, intervention, comparison and outcome (PICO) strategy by 2 independent reviewers. The search was performed in PubMed, Embase and Cochrane Library, including keywords “diabetes mellitus”, “DR” and “OCTA”. Of 358 studies initially identified, 215 studies were screened after duplicate removal. Of these, these investigators included 12 (9 cross-sectional and 3 retrospective) studies in this review. With the data at hand, it was not possible to perform a meta-analysis. The selected studies included patients with NDR (n = 8), non-proliferative diabetic retinopathy (NPDR, n = 8) and proliferative diabetic retinopathy (PDR, n = 6). Several of the studies provided information for more than 1 diabetic group. In general, there was a trend towards a larger area of FAZ in patients with diabetes. As compared to healthy controls, this was reported in patients with NDR (5 of 8 studies), NPDR (7 of 8 studies) and PDR (6 of 6 studies). The authors concluded that OCTA was non-invasively able to identify foveal capillary non-perfusion as an early event in DR. In some studies, this has even been identified in patients without clinically identifiable microvascular lesions. Moreover, these researchers stated that longitudinal studies are needed to examine if OCTA-findings are able to predict long-term structural and functional outcome.
Akil et al (2019) stated that OCTA is a non-invasive method that enables visualization of blood flow within retinal vessels down to the size of capillaries by detecting motion contrast from moving blood cells. OCTA provides a safe procedure to assess retinal microvasculature with higher contrast and resolution than conventional fluorescence angiography (FA). The different capillary plexuses are displayed separately; and their perfusion density can be quantified. Imaging capabilities such as these have led to an emerging field of clinical application for OCTA in vascular diseases such as DR. Evaluation of parameters such as para-foveal capillary perfusion density could be a biomarker for disease diagnosis and progression. Typical microvascular changes in DR such as capillary non-perfusion, micro-aneurysms, intra-retinal microvascular abnormalities, and neovascularization can be reliably detected in OCT angiograms, characterized in detail and attributed to the different capillary plexuses. Monitoring of these lesions in-vivo gives potential novel insight into the pathophysiology in DR. The authors summarized the potential applications/utility of OCTA in DR reported in the literature.
Vaz-Pereira et al (2020) noted that DR is a leading cause of blindness due to diabetic macular edema (DME) or complications of proliferative DR (PDR); OCT is a non-invasive imaging technique well-established for DME but less used to assess neovascularization in PDR. Developments in OCT imaging and the introduction of OCTA have shown significant potential in PDR.
In an observational, cohort, cross-sectional study, Yang et al (2020) examined microvascular abnormalities in diabetic patients without conventional clinical signs of DR. The study group included randomly chosen participants of a community-based cohort with diabetes type 2 without DR, and the control group consisted of non-diabetic individuals from a population-based study. All participants underwent OCTA. Upon OCTA, 118 (40.4 %) eyes of the study group (n = 292 eyes) showed microvascular abnormalities including FAZ erosion (95 (32.5 %) eyes), non-perfusion areas in the superficial and deep retinal layers (39 (13.4 %) eyes and 19 (6.5 %) eyes, respectively), and micro-aneurysms in the superficial and deep retinal layers (22 (7.5 %) eyes and 31 (10.6 %) eyes, respectively). None of these abnormalities was detected in the control group (n = 80). The study group showed a lower vessel density in the superficial retinal vascular layer in all regions except for the foveal region (p < 0.001), and higher vessel density in the para-foveal region in the deep retinal vascular layer (p = 0.01). Higher diabetes prevalence was associated with lower superficial retinal vascular density (p = 0.005) in multi-variable analysis. A lower radial peripapillary capillary flow density was correlated (regression coefficient r, 0.62) with higher fasting blood concentration of glucose (p < 0.001) in multi-variable analysis. The authors concluded that OCTA revealed microvascular abnormalities in 40 % of eyes of diabetic patients without ophthalmoscopically detectable diabetic fundus changes in a community-based population. These researchers stated that the early stage of DR may be re-defined upon OCTA.
Li et al (2021) noted that DR is the most common microvascular complication of diabetes; however, early changes in retinal micro-vessels are difficult to detect clinically, and a patient's vision may have begun to deteriorate by the time a problem is identified; OCTA is an innovative tool for observing capillaries in-vivo. In a retrospective, observational, cross-sectional study, these researchers analyzed retinal vessel density and thickness changes in patients with diabetes. Between August 2018 and February 2019, these investigators collected OCTA data from healthy subjects and diabetics from the First Affiliated Hospital of Harbin Medical University. They analyzed the retinal vessel density and thickness changes of the participants. A total of 97 diabetic patients with diabetes at different severity stages of DR and 85 controls were involved in this study. Diabetic patients exhibited significantly lower retinal VD (particularly in the deep vascular complexes), thickening of the neurosensory retina, and thinning of the retinal pigment epithelium compared with controls. In the control group, non-DR group and mild DR group, superficial VD was significantly correlated with retinal thickness (r = 0.3886, p < 0.0001; r = 0.3276, p = 0.0019; r = 0.4614, p = 0.0024, respectively). The authors concluded that patients with diabetes exhibit ischemia of the retinal capillaries and morphologic changes in-vivo before vision loss; thus, OCTA may be useful as a quantitative method for the early detection of DR.
Furthermore, an UpToDate review on “Diabetic retinopathy: Classification and clinical features” (D'Amico and Shah, 2023) does not mention OCT angiography as a management option.
Annual OCT for the Follow-Up of Thyroid Ophthalmopathy After Orbital Decompression
In an observational, cross-sectional, controlled study, Forte et al (2010) examined retinal nerve fiber layer (RNFL) thickness in eyes with Graves' orbitopathy (GO), in eyes with ocular hypertension (OHT) and in a control group of healthy eyes. These investigators evaluated all patients with primary open-angle glaucoma (POAG) and all patients with GO and intra-ocular pressure (IOP) of greater than 23 mm Hg in primary position examined from March 2006 to June 2007. A total of 40 apparently healthy patients (80 eyes) were enrolled as a control group. Complete ophthalmic evaluation, visual field (VF) examination with the Humphrey Visual Field Analyzer and RNFL thickness measurement with optic nerve tracking OCT (ONT-OCT) were performed. Among 116 eyes with POAG [58 patients, 32 men, 26 women, mean age of 62 (46 to 71) years], RNFL was reduced in 87 eyes (75 %, p = 0.05) when compared with the control group, and a good correlation was found between RNFL thickness and VF abnormalities (Spearman's rho 0.822; p = 0.001). Among 60 eyes [30 patients, 12 men, 18 women, mean age of 56 (50 to 69) years] with GO and OHT, non-glaucomatous diffuse abnormalities of the VF were detected in 44 eyes (73.3 %, p = 0.03), while RNFL thinning was present in 14 eyes (9 patients, 23.3 %, p = 0.03). No correlation was found between RNFL thickness and VF abnormalities (Spearman's rho 0.365; p = 0.02). No significant differences in RNFL pattern were present between the group with GO, OHT and RNFL thinning and the group with POAG. The authors concluded that in patients with GO and OHT, evaluation of RNFL thickness with ONT-OCT may represent an objective diagnostic technique for detecting optic neuropathy.
Park et al (2016) examined the influence of optic nerve compression (ONC) on the peripapillary RNFL thickness in eyes with acute and chronic dysthyroid optic neuropathy (DON). Patients with DON and healthy control subjects underwent peripapillary OCT scanning with the Cirrus HD-OCT. Patients were classified as acute (within 6 months from the onset of DON) versus chronic (6 months or more from the onset of DON) DON. The thickness of peripapillary RNFL was compared between eyes with acute and chronic DON and control eyes. Baseline factors associated with visual acuity (VA) at the last visit were also analyzed. The mean temporal peripapillary RNFL thickness was thinnest in chronic DON at 66 ± 12 μm compared to 76 ± 8 μm in eyes with acute DON and 73 ± 12 μm in control eyes (p = 0.014). In a multi-variable analysis, patients with greater inferior peripapillary RNFL thickness and younger age tended to have better VA at the last visit (p = 0.034, odds ratio [OR] = 1.038 and p = 0.007, OR = 0.912, respectively). The authors concluded that these findings revealed a notable difference in temporal peripapillary RNFL thickness in eyes with chronic DON compared to eyes with acute DON and control eyes. They also found a significant association between inferior peripapillary RNFL thickness and VA at the last visit. Thicker inferior peripapillary RNFL thickness was associated with better visual outcome. These researchers stated that further studies with large sample sizes using a prospective design should more clearly reveal the time aspect of the association between the onset of DON and the changes in peripapillary RNFL, and their clinical significance.
In an observational, cross-sectional study, De-Pablo-Gomez-de-Liano et al (2019) evaluated the correlation between OCT and MRI measurements of extra-ocular rectus muscle thickness in patients with Graves' ophthalmopathy. This trial was carried out in 62 eyes of 31 patients with Graves' ophthalmopathy. The disease phase was inactive in 20 patients and active in the remaining 11. The OCT measurements obtained included medial rectus thickness at 7.2 and 9.2 mm from the limbus and lateral rectus thickness at 8.5 mm from the limbus. MRI measurements were maximum transversal diameter (T-MRI), cranio-caudal diameter (CC-MRI), and muscle area (A-MRI). For the whole patient cohort, correlation emerged between the OCT-MR and T-MRI measurements (r = 0.428 to 0.576; p ≤ 0.002), A-MRI (r = 0.562 to 0.674; p < 0.001), and CC-MRI (r = 0.286 to 0.293; p ≤ 0.046). In patients with clinically active Graves' ophthalmopathy, correlations with T-MRI (r = 0.576 to 0.604; p ≤ 0.010) and A-MRI (r = 0.678 to 0.706; p < 0.001) were higher. No correlations were observed between OCT and MRI measurements of lateral rectus thickness (p ≥ 0.177), regardless of disease phase. The authors concluded that the correlations observed suggested that OCT could be a complementary assessment or screening method to detect thickening of the anterior portion of the medial rectus muscle in patients with Graves' ophthalmopathy, which may be especially useful when MRI is not available.
In a prospective, single-center, case-series study, Lewis et al (2019) examined the use of OCT angiography (OCTA) in the evaluation of GO and response to orbital decompression in patients with and without DON. This trial included 12 patients (24 orbits) with GO and ± DON, (6 orbits) who underwent bilateral orbital decompression. All patients underwent pre- and post-operative OCTA of the peripapillary area. Vessel density indices were calculated in a 4.5 mm × 4.5 mm ellipsoid centered on the optic disk using split-spectrum amplitude decorrelation angiography algorithm, producing the vessel density measurements. Mean change in vessel density indices was compared between pre- and post-operative sessions and between patients with and without DON. Patient 1, a 34-year-old man with GO and unilateral DON OD, showed a significant reduction in blood vessel density indices oculus dexter (OD) (DON eye) after decompression while a more modest reduction was found oculus sinister (OS) with the greatest change noted intra-papillary. Patient 2, a 50-year-old man with DON OU, showed worsening neuropathy following decompression OD that was confirmed by angiographic density indices. Patient 3, a 55-year-old woman with DON, showed a reduction in blood vessel density OD and increased density OS. Patients without DON showed overall less impressive changes in indices as compared to those with DON. Using OCTA, response to surgical treatment in GO orbits, more so in orbits with DON, could be demonstrated and quantified using vessel density indices with reproducibility.
Furthermore, an UpToDate review on “Clinical features and diagnosis of thyroid eye disease” (Davies and Burch, 2023) does not mention OCT as a management option.
Intraoperative Wide-Field OCT for Analysis of Deep Margins in Head and Neck Surgery
Badhey et al (2023) stated that involvement of deep margins represents a significant challenge in the treatment of oropharyngeal cancer, and given practical limitations of frozen-section analysis, a need exists for real-time, non-destructive intra-operative margin analysis. Wide-field optical OCT (WF-OCT) has been studied as a tool for high-resolution adjunct specimen imaging in breast surgery; however, its clinical application in head and neck surgery has not been examined. In a qualitative, non-randomized, single-center, feasibility study, these investigators examined the use of WF-OCT for visualizing microstructures at margins of excised oral and oropharyngeal tissue. They examined the feasibility of the Perimeter Medical Imaging AI Otis WF-OCT device. Included subjects were adults undergoing primary ablative surgery of the oral cavity or oropharynx for squamous cell carcinoma (SCC) in 2018 and 2019. Data were analyzed in October 2019. Patients were treated according to standard surgical care. Freshly resected specimens were imaged with high-resolution WF-OCT before routine pathology. Inter-disciplinary interpretation was carried out to interpret WF-OCT images and compare them with corresponding digitized pathology slides. No clinical decisions were made based on WF-OCT image data. Visual comparisons were carried out between WF-OCT images and hematoxylin and eosin slides. A total of 69 specimens were collected and scanned from 53 patients (mean [SD] age, 59.4 [15.2] years; 35 [72.9 %] men among 48 patients with demographic data) undergoing oral cavity or oropharynx surgery for SCC, including 42 tonsillar tissue, 17 base of the tongue, 4 buccal tissue, 3 mandibular, and 3 other specimens. There were 41 malignant specimens (59.4 %) and 28 benign specimens (40.6 %). In visual comparisons of WF-OCT images and hematoxylin and eosin slides, visual differentiation among mucosa, submucosa, muscle, dysplastic, and benign tissue was possible in real-time using WF-OCT images. Micro-architectural features observed in WF-OCT images could be matched with corresponding features within the permanent histology with fidelity. The authors concluded that this qualitative study found that WF-OCT imaging was feasible for visualizing tissue micro-architecture at the surface of resected tissues and was not associated with changes in specimen integrity or surgical and pathology workflow. These researchers stated that these findings suggested that formal clinical studies examining use of WF-OCT for intra-operative analysis of deep margins in head and neck surgery may be warranted. Moreover, they stated that other potential areas for study include the development of a comprehensive WF-OCT image atlas of benign and abnormal microstructures observed in excised specimens of the oral cavity and oropharynx, evaluation of the use of artificial intelligence (AI) tools currently in development to aid in detection of suspicious regions of interest, and a direct comparison of WF-OCT with frozen section analysis (FSA) or specimen x-ray for intra-operative margin analysis.
The authors stated that this study had several drawbacks. First, it was a device feasibility study with no formal control group and was not designed to make direct comparisons between WF-OCT and other emerging technologies for intra-operative margin assessment, nor was it designed to measure performance. Second, a clinically relevant limitation of OCT in general is that it has a maximum light-penetration depth in biological tissue of 1 to 2 mm. While that depth is generally sufficient for margin assessment in breast oncology, tumors of the oral cavity are typically defined as negative if the margin is clear to a depth of 5 mm or more. At present, OCT is not capable of evaluating tissue micro-architecture at that depth unless multiple scans are acquired from different specimen aspects. This is an area for further study and refinement. Third, as with other methods of margin analysis, artifacts caused by surgical electro-cauterization during trans-oral robotic surgery present a potential technical limitation because they may complicate image interpretation at the deep margin. Ultrasonic or other low-temperature dissection methods may eventually solve the problem of cautery artifacts; however, no such method has yet reached standards of care (SOC). Further investigation is needed to solve the problem of margin destruction during electrosurgical dissection. Fourth, these researchers also identified a work-flow limitation related to standardization of margin orientation and specimen processing. Specifically, these investigators found that specimens were often being serially sectioned along a different axis than the direction of OCT optical slices (e.g., sectioned posterior to anterior, while OCT was scanned inferior to superior). This impaired the ability of pathologists to make direct comparisons between WF-OCT images and corresponding histology in some cases. Simple communication and work-flow alignment were sufficient to remedy the issue and show the adaptability of technology and team. These researchers stated that future studies using this technology should consider this work-flow detail during study design.
Dynamic Optical Coherence Tomography for Evaluation of Actinic Keratosis
Fredman et al (2024) noted that actinic keratosis (AK) classification relies on clinical characteristics limited to the skin's surface. Incorporating sub-surface evaluation may improve the link between clinical classification and the underlying pathology. In an explorative study, these researchers used dynamic OCT (D-OCT) to characterize micro-vessels in AK I to III and photo-damaged (PD) skin; thus, examining its use in enhancing clinical and dermatoscopic AK evaluation. This trial examined AK I to III and PD on face or scalp. AK were graded according to the Olsen scheme before assessment with dermatoscopy and D-OCT. On D-OCT, vessel shapes, pattern, and direction were qualitatively evaluated at pre-defined depths, while density and diameter were quantified. D-OCT's ability to differentiate between AK grades was compared with dermatoscopy. A total of 47 patients with AK I to III (n = 207) and PD (n = 87) were included. Qualitative D-OCT evaluation showed vascular differences between AK grades and PD, especially at a depth of 300 μm. The arrangement of vessel shapes around follicles differentiated AK II from PD (OR = 4.75, p < 0.001). Vessel patterns varied among AK grades and PD, showing structured patterns in AK I and PD, non-specific in AK II (OR = 2.16, p = 0.03) and mottled in AK III (OR = 29.94, p < 0.001). Vessel direction changed in AK II to III, with central vessel accentuation and radiating vessels appearing most frequently in AK III. Quantified vessel density was higher in AK I to II than PD (p ≤ 0.025), whereas diameter remained constant. The authors concluded that through qualitative vessel evaluation as well as quantification of vessel density and diameter, D-OCT enabled in-vivo characterization of micro-vascular differences between AK I and III and PD skin. Both qualitative and quantitative assessments consistently demonstrated increased vascularization and vessel disorganization in AK lesions of higher grades. These investigators stated that the incorporation of D-OCT into the clinical and dermatoscopic evaluation of AK may assist in diagnosis and holds potential to optimize management strategies.
The authors stated that this study used a systematic qualitative image analysis following a terminology consensus; however, the unblinded single-assessor evaluation of vessels remained a key drawback. These researchers considered the limitation acceptable considering the study's explorative aim of determining D-OCT's utility in detecting distinct vascular features in AKs I to III and PD skin. Another drawback was the use of the observer-dependent clinical AK grading. Application of this grading scheme may partly explain why some AK grades showed overlapping features. A more reproducible grading system that also accurately examine underlying histology, would provide a more powerful comparison with D-OCT. Vessel evaluation at D-OCT's maximum penetration depth of 500 μm was excluded from this trial due to projection artefacts and background interference of the D-OCT signal. Although projection artefacts arise at all skin depths, they are most prominent in deeper parts of the skin; therefore, overcoming the limit of projection artefacts is an important subject for future studies. D-OCT combined with dermatoscopy enabled precise differentiation of AK III versus AK I (AUC = 0.908) and II (AUC = 0.833). The qualitative and quantitative evaluation of vessels on D-OCT consistently demonstrated increased vascularization and vessel disorganization in AK lesions of higher grades.
Optical Coherence Tomography Angiography in Patients with Giant Cell Arteritis, with and without Ocular Involvement
In a pilot study, Vannozzi et al (2024) examined the clinical features and retinal and disk perfusion characteristics by using OCT and OCTA in a subset of giant cell arteritis (GCA) patients who manifested anterior ischemic optic neuropathy (AION), in a subset of GCA patients without ocular involvement, and in a control group composed of healthy controls (HCs). These researchers carried out an observational study on the eyes of GCA patients affected by arteritic AION both in acute and chronic phases, unaffected eyes of AION, eyes of GCA patients without ocular involvement, and in a HC group. All patients underwent a complete ophthalmic examination and an OCT and OCTA of the macula and the disk. The study evaluated 10 eyes of GCA patients with AION (AION group), 8 unaffected eyes of GCA patients with AION in another eye (unaffected eyes of AION group), 16 eyes of GCA patients without ocular involvement (non-ocular group), and 22 eyes of HCs (healthy group). The ganglion cell complex (GCC) superior and inferior thicknesses were significantly lower in the AION group compared to the unaffected eyes of the AION group (p = 0.045 and p = 0.034, respectively). All OCTA vascular density parameters of the optic disk analyzed in this study (optic nerve head (ONH) whole, superior, inferior, radial peri-papillary capillary plexus (RPCP) whole, superior, inferior, lamina cribrosa (LC) whole, superior, inferior) resulted significantly lower in the AION group compared to the unaffected eyes group (p < 0.05 for all the comparisons). The ONH whole and inferior were statistically higher in the HC group in comparison to the group of GCA patients without ocular involvement (p = 0.008 and p = 0.006, respectively). The ONH inferior was also statistically higher in the unaffected eyes of the AION group in comparison to the non-ocular group (p = 0.045). Regarding the OCTA macular vessel density parameters, the superficial capillary plexus (SCP), whole and inner, were statistically lower in the AION group compared with the unaffected eyes of the AION group. The authors found a profound vascular impairment in eyes affected by AION and areas of hypo-perfusion in the eyes of patients with GCA without ocular involvement, good best-corrected visual acuity (BCVA), and no clinically significant features. These investigators hypothesized that these areas of lower vessel density might represent areas of sub-clinical hypo-perfusion that cannot be detected ophthalmoscopically. Moreover, these researchers found perfusion defects in the eyes of patients with GCA without ocular involvement that were clinically unremarkable. They stated that further studies, with more enrolled patients, are needed to examine the role of OCTA in the characterization of vascular impairment in arteritic AION and the detection of subclinical features of low perfusion in GCA patients without a manifest ocular involvement.
The authors stated that this study had several drawbacks. First, the sample size was small, although GCA is a rare condition. Second, these investigators had to consider that GCA patients more frequently display cardiovascular risk factors, such as dyslipidemia and hypertension, than non-vasculitis patients, and this fact may have an impact on the findings of this trial. Third, the inclusion of the same sample of patients with AION both in the acute phase and in the late phase could represent another limitation because, generally, in the acute phase, the ONH is edematous, while in the late phase, it is atrophic. The authors analyzed these data together because it was difficult to make analyses separating the 2 groups due to the small size of the population studied; however, that fact made the structural analysis of RNFL not clinically significant. It can be useful in further studies to analyze the chronic and acute phases of arteritic AION separately, increasing the size of the population. In addition, it could be interesting to analyze the RNFL defects in comparison with the OCTA values, as some authors did, finding a correlation between vessel density impairment and RNFL defects, and further analyze the correlation of the visual field with the OCTA parameters and perimetric alterations. Fourth, these investigators conducted a cross-sectional analysis of perfusion characteristics revealed with OCTA; however, a longitudinal study of patients analyzed in acute phase AION and during a follow-up could be useful to examine the changes in perfusion over time and the role of optic disk perfusion alterations in the pathogenesis of non-acute phase AION.
Optical Coherence Tomography Angiography for Detection of Thyroid-Associated Ophthalmopathy
In a systematic review, Rajabi et al (2024) examined the available evidence for alterations of blood flow, vascular and perfusion densities in the choroid, macula, peri-papillary region, and the area surrounding the optic nerve head (ONH) in patients with thyroid-associated ophthalmopathy (TAO) based on changes of OCTA parameters. These investigators carried out a systematic review of PubMed, Google Scholar, Scopus, WOS, Cochrane, and Embase databases, including quality assessment of published studies, examining the alterations of OCTA parameters in TAO patients. The outcomes of interest comprised changes of perfusion and vascular densities in radial peripapillary capillary (RPC), ONH, superficial and deep retinal layers (SRL and DRL), chorio-capillaris (CC) flow, and the extent of the foveal avascular zone (FAZ). From the total of 1,253 articles obtained from the databases, the pool of papers was narrowed down to studies published until March 20, 2024. A total of 42 studies were taken into consideration, which contained the data regarding the alterations of OCTA parameters including chorio-capillary vascular flow, vascular and perfusion densities of retinal micro-vasculature, SRL, and DRL, changes in macular all grid sessions, changes of foveal, peri-foveal and para-foveal densities, macular whole image vessel density (m-wiVD) and FAZ, in addition to alterations of ONH and RPC whole image vessel densities (onh-wiVD and rpc-wiVD) among TAO patients. The correlation of these parameters with visual field-associated parameters, such as BCVA, visual field mean defect (VF-MD), axial length (AL), P100 amplitude, and latency, was also evaluated among TAO patients. The authors concluded that the use of OCTA has proven helpful in distinguishing active and inactive TAO patients, as well as differentiation of patients with or without DON, indicating the potential promising role of some OCTA measures for early detection of TAO with high sensitivity and specificity in addition to preventing the irreversible outcomes of TAO.
Furthermore, an UpToDate review on “Clinical features and diagnosis of thyroid eye disease” (Davies and Burch, 2024) does not mention OCTA as a management/therapeutic option.
Optical Coherence Tomography Otoscope for Imaging of Tympanic Membrane and Middle Ear Pathology
In a cross-sectional study, Preciado et al (2020) examined the feasibility of detecting and differentiating middle ear effusions (MEEs) using an OCT otoscope. A total of 70 pediatric patients undergoing tympanostomy tube placement were pre-operatively 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 versus non-serous MEE. 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-/inter-reader agreement of 92.9 % and 87.1 %, respectively. Differentiating MEE type, reader identification of non-serous MEE had 70.8 % accuracy, 53.6 % sensitivity, 80.1 % specificity, and intra-/inter-reader agreement of 82.9 % and 75.1 %, respectively. Multi-variate analysis demonstrated 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 = 0.0028). The ability to capture quality images improved over time, from 50 % to 69.4 % over the study period. The authors concluded that OCT otoscopy showed promise in 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. Moreover, these researchers stated that further investigations are needed to compare the accuracy of OCT otoscopy to current clinical diagnostic technologies and determine its generalizability among healthcare providers to improve the accurate detection and differentiation of MEE, to drive appropriate management of acute otitis media (AOM) and otitis media with effusion (OME).
Won et al (2021) stated that middle ear infection is a prevalent inflammatory disease most common in the pediatric population. Current diagnostic methods are highly subjective, relying on visual cues gathered by an otoscope. To address this shortcoming, OCT has been integrated into a hand-held imaging probe. This system can non-invasively and quantitatively evaluate middle ear effusions and identify the presence of bacterial biofilms in the middle ear cavity during ear infections. In addition, 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. These researchers presented a brief-case OCT system implemented with a real-time machine learning (ML) platform for middle ear infections. A random forest-based classifier can categorize images based on the presence of MEE and biofilms. The authors concluded that this study showed that their brief-case OCT system coupled with ML could provide user-invariant classification results of middle ear conditions, which may improve the use of this technology for the diagnosis and management of middle ear infections. Moreover, these researchers stated that more investigations are needed to correlate and evaluate the data-set, ground truth, and the label, to determine the diagnostic importance of AI-assisted OCT otoscopy in clinical practice.
The authors stated that this study had several drawbacks. First, the processing power and memory of the laptop were limiting factors in the speed of OCT processing and display, as well as for the ML classifier. It should be noted that all the hardware and optical components used in the system were off-the-shelf products. Implementing graphic processing units (GPUs) will further enhance the speed of the system. With emerging technologies and products in compact OCT wave-guides that integrate a light source and detector, the size of the system can be further reduced in the future. As the brief-case system did not employ a lateral scanning element to generate B-mode images of the middle ear, the measurements can be affected by the spatial locations of the focused beam on the TM. Implementing a compact lateral scanning mechanism using a micro-electro-mechanical systems (MEMS)-based mirror can reliably provide lateral information, which would aid in minimizing the spatial dependence of the measurements. This may further improve the usability and system performance. Second, with a larger data-base and an improved model, hyper-parameter tuning can be carried out to compare different ML models. This model has been internally validated and examined by means of the the leave-one-out cross-validation method. External validation was limited due to the small size of the data-set. With the increasing number of ear OCT images and data-sets in the future, the model could be further improved by external validation using a held-out, independent data-set. Third, the spatial dependence of measurements from the TM could also be overcome with an improved ML classifier. For example, the data-set of OCT images containing different regions on the TM could be obtained and trained in the ML classifier. OCT images with various image artifacts (mirror artifacts, flipped image, and strong reflections) could also be collected and included in the training data-set. This would exclude the measurements with artifacts and could potentially guide the users to avoid these artifacts during imaging. It was also observed that the novice users heavily relied on the surface images of the TM to guide and focus the laser beam during the imaging. In the future, a charge-coupled device (CCD) camera with a higher resolution, a larger field-of-view, and a greater depth-of-focus to capture the entire TM would be helpful for users without prior knowledge of OCT. The surface images of the TM were not included in the classifier, as the properties of the CCD images (i.e., lighting, field-of-view, depth-of-focus and resolution) from the brief-case system were different from the trained otoscopy images in the previously developed classifier. With greater computing power in the future, providing the surface images of the TM to the classifier may enhance the classification accuracy. Fourth, having rigid time constraints to image patients’ ears in a busy clinical environment may have resulted in sub-optimal image quality in some cases. While trained users without prior experience of OCT and otoscopy attempted to image the subjects diagnosed with OM, not all users were successful to acquire reliable data-sets because of the given time constraints. Allowing for a longer imaging time window with more training and practice would improve image quality. A larger number of subjects diagnosed with OM are needed in future investigations to better characterize the clinical significance and accuracy of the system. Fifth, this study only recruited adult subjects because the subjects needed to be tolerant to allow 3 different users to image their ears. A future trial will include pediatric subjects as well and examine differences that may emerge in this patient population.
Porter et al (2022) noted that childhood ear infections are highly prevalent and diagnosed with the otoscope, a simple tool that illuminates and magnifies the eardrum to subjectively evaluate color, translucency and presence of any middle ear fluid; however, this view is often obstructed by cerumen, complicating clinician assessment and appropriate and effective management. An optical OCT-otoscope capable of capturing both depth-resolved OCT images and digital color surface images was employed to compare OCT against otoscopy for imageability and readability despite cerumen obstruction. Image data were collected from 26 human subjects and read by 12 blinded clinicians and 5 blinded OCT experts. An average of 64.6 % of otoscopy views were obstructed. For cases with greater than 75 % otoscopy view obstruction, OCT imageability was 84.6 %, while otoscopy imageability was 37.5 %, excluding complete obstruction cases. The authors concluded that OCT-otoscopy is a promising new technology to improve the ease of practical middle ear assessment despite cerumen or other obstructions, which often render current diagnostic assessments ineffective. Moreover, these researchers stated that further investigations on the clinical use of OCT-otoscopy will expand on the limited number of subjects and the limited number of blinded image readers involved in this preliminary study, compare OCT-otoscopy performance to other commercially available clinical imaging tools (e.g., standard and/or pneumatic otoscopy or tympanometry), and examine OCT-otoscopy ease and speed of use in pediatrics by a variety of clinicians who routinely conduct ear examinations. Finally, the development of assistive image interpretation algorithms to supplement clinician OCT-otoscopy interpretation has the potential to further facilitate the adoption and clinical use of this promising imaging tool.
Teague and Nolan (2023) stated that accurate diagnosis of otitis media is important to judicious antibiotic prescription. Visualization of the tympanic membrane and accurate identification of MEE 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 AOM versus OME ranging from 30 % to 84 % among pediatricians, there is a need for diagnostic improvement and decreasing unnecessary antibiotic use. In a 96-pediatrician-blinded otoscopy diagnosis quiz, addition of OCT, a novel depth-imaging technology, resulted in a 32 % improvement in fluid identification, and 21 % increase in diagnostic accuracy. The authors concluded that the findings of this study supported the promise of OCT‐otoscopy as a more accurate SOC for pediatric patients, improving antibiotic stewardship, eliminating unnecessary referrals, and decreasing healthcare costs associated with OM.
Kim et al (2024) stated that pathologies within the tympanic membrane (TM) and middle ear (ME) can result in hearing loss. Imaging tools available in the hearing clinic for diagnosis and management are limited to visual inspection using the classic otoscope. The otoscopic view is limited to the surface of the TM, especially in diseased ears where the TM is opaque. An integrated OCT otoscope can provide images of the interior of the TM and ME space as well as an otoscope image allowing the clinicians to correlate the standard otoscopic view with OCT; and then use the additional information to improve the diagnostic accuracy and management. These researchers developed an OCT otoscope that can be used in the hearing clinic and showed the system in the hearing clinic, identifying relevant image features of various pathologies not apparent in the standard otoscopic view. These investigators developed a portable OCT otoscope device featuring an improved field of view and form-factor that can be operated solely by the clinician using an integrated foot pedal to control image acquisition. The device was used to image patients at a hearing clinic. The field of view of the imaging system was improved to a 7.4 mm diameter, with lateral and axial resolutions of 38 μm and 33.4 μm, respectively. They developed algorithms to re-sample the images in Cartesian coordinates following collection in spherical polar coordinates and corrected the image aberration. These researchers imaged over 100 patients in the hearing clinic at USC Keck Hospital. They identified some of the pathological features evident in the OCT images and highlighted cases in which the OCT image provided clinically relevant information that was unavailable from traditional otoscopic imaging. The authors concluded that they developed an OCT otoscope that can readily fit into the hearing clinic work-flow and can provide new relevant information for diagnosing and managing TM and ME disease. Well-designed studies are needed to validate these preliminary findings.
Wu et al (2024) reviewed new drugs and devices relevant to otolaryngology approved by the FDA in 2022. These investigators carried out a preliminary screen to identify drugs and devices relevant to otolaryngology. A secondary screen by members of the American Academy of Otolaryngology-Head and Neck Surgery's (AAO-HNS) Medical Devices and Drugs Committee differentiated between minor updates and new approvals. The final list of drugs and devices was sent to members of each sub-specialty for review and analysis. The authors concluded that a total of 1,251 devices and 37 drugs were identified on preliminary screening. Of these, 329 devices and 5 drugs were sent to sub-specialists for further review, from which 37 devices and 2 novel drugs were selected for further analysis. The OtoSight Middle Ear Scope (PhotoniCare) is a video-otoscope that allows for direct visualization of the tympanic membrane with OCT. The technology also allows physicians to view beyond the tympanic membrane to examine middle ear pathology. It employs low‐coherence light to capture 2D and 3D images of the middle ear tissue. The technology enables clinicians to visualize past cerumen, other canal obstructions, and opacified tympanic membranes to guide the clinician in evaluating middle ear disease. The authors concluded that given the recent approval of these devices, further studies are needed to examine long-term impact within the field of otolaryngology.
Liu et al (2024) noted that 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 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. These researchers proposed C2P-Net: a 2-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 was designed to simulate middle ear shapes and extract in-vivo noisy and partial point clouds. These investigators examined the performance of C2P-Net via experiments on both synthetic and real OCT data-sets. The results showed 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. The authors concluded that they aimed to enable diagnosis of middle ear structures with the assistance of OCT images. These researchers proposed C2P-Net, a 2-staged non-rigid registration pipeline, for point clouds to support the interpretation of in-vivo noisy and partial OCT images for the first time.
Furthermore, an UpToDate review on “Otitis media with effusion (serous otitis media) in children: Clinical features and diagnosis” (Marom, 2024) states that “Noninvasive technologies that overcome some of the objective difficulties of standard οtοѕсорy for the diagnosis of ОΜΕ are under investigation. These include use of artificial intelligence algorithms, optical coherence tomography, transmastoid ultrasound, and quantitative tуmраոometry, among others”.
References
The above policy is based on the following references:
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