Optical coherence tomography-based micro-particle image velocimetry

ABSTRACTAimThis review aims to critically analyze the current literature on the relationship of optical coherence tomography (OCT) measures to cognition and dementia.BackgroundOptical coherence tomography, a noninvasive method of imaging neuroretinal layers, and OCT angiography, a highly precise method of examining retinal vasculature, have widely been used to aid in the diagnosis and monitoring of a variety of ocular diseases. There is now an increasing body of evidence relating the structural and microvascular changes of the retina to cognitive impairment.Review resultsIn general, several studies have found decreased retinal nerve fiber layer (RNFL) thickness in Alzheimer’s disease (AD) and mild cognitive impairment (MCI) and an association between RNFL thickness and continuous measures of cognitive ability, though findings were inconsistent across studies. In many studies, associations were found for specific regions of the RNFL but not with overall thickness. Studies linking OCT measures to non-Alzheimer’s dementia were lacking, and limited work has been done on persons with past cognitive decline but who remain cognitively normal (the ideal stage at which to target treatment). Common limitations of prior studies include a failure to account for intraocular pressure (IOP) and axial length.ConclusionCurrent research suggests a potential association between retinal findings observed on OCT and cognitive impairment. Methodologically robust research accounting for important covariates and looking at changes in OCT and/ or cognition is needed to better characterize the association between OCT and cognitive ability.Clinical significanceFurther research is warranted to determine whether OCT findings can help identify the etiology of cognitive decline and/or serve as objective markers of AD. If this is the case, OCT may also help identify the presence of disease processes in cognitively normal individuals.How to cite this article: Lee MJ, Abraham AG, Swenor BK, Sharrett AR, Ramulu PY. Application of Optical Coherence Tomography in the Detection and Classification of Cognitive Decline. J Curr Glaucoma Pract 2018;12(1):10-18.

We report a novel application of optical coherence tomography (OCT), to monitor post-laser irradiation collagen injury in skin model. An artificial skin model (RAFT) which closely approximates human skin, was irradiated with a Perovskite laser (λ = 1341 nm). We investigated dynamic changes in a RAFT after laser irradiation through OCT and compared the results to those of histology. OCT images clearly delineated areas of post-irradiation collagen injury and allowed non-invasive monitoring of the wound healing process. Histology was correlated well with OCT images. OCT has advantages because it is non-invasive and allows serial monitoring at the same site over time. Our study showed that OCT may be a useful tool for determination of optimal parameters for non-ablative laser skin rejuvenation (NALSR) using different devices.

We report the application of Optical Coherence Tomography (OCT) to various types of human cases of otitis media (OM). Whereas conventional diagnostic modalities for OM, including standard and pneumatic otoscopy, are limited to visualizing the surface information of the tympanic membrane (TM), OCT is able to effectively reveal the depth-resolved microstructural below the TM with a very high spatial resolution. With the potential advantage of using OCT for diagnosing different types of OM, we examined in-vivo the use of 840 nm wavelength, and OCT spectral domain OCT (SDOCT) techniques, in several human cases including normal ears, and ears with adhesive and effusion types of OM. Peculiar positions were identified in two-dimensional OCT images of abnormal TMs compared to images of a normal TM. Analysis of A-scan (axial depth-scans) data from these positions could successfully identify unique patterns for different constituents within effusions. These OCT images may not only be used for constructing a database for the diagnosis and classification of OM, but they may also demonstrate the feasibility and advantages for upgrading the current otoscopy techniques.

Objective To investigate the feasibility of using optical coherence tomography （OCT）in thy-roid surgery .Methods Surgical specimen including parathyroid gland , lymph nodes , adipose tissue and thyroid tissue from patients receiving thyroid surgery in Tianjin Medical University Cancer Institute and Hospital were col -lected.OCT images were collected and the results were compared with the routine examination .Results Para-thyroid glands , lymph nodes , adipose tissue , and thyroid tissue can be obtained high-resolution OCT images .Dif-ferent tissues and metastatic lymph node can be clearly distinguished .OCT imaging took about 1 minute and fro-zen examination cost about 25 minutes.Conclusions OCT is a time-saving, non-invasive and cross-sectional imaging technique .It can obtain clear structural images of the internal microstructure of bio-tissues.OCT technol-ogy used in thyroid surgery including parathyroid identification and determination of lymph node metastasis is fea -sible. Key words: Parathyroid; Optical coherence tomography; Lymph node

Summary form only given. Dental restoration interfaces can present failures, known as marginal microleakage. These failures are extremely difficult to diagnose and can develop into recurrent caries if left untreated. The most common tool used for diagnostic imaging in dentistry, X-ray, is not able to visualize micrometric structures. Evaluation of dental restoration in a non-invasive way is a very desirable tool for clinical practice. We present an in vivo study applying Optical Coherence Tomography (OCT) to detect failures at the enamel-dental restoration interface in a clinical setting. OCT is a relatively new but well established imaging technique for diagnosis, that can produce two- or three- dimensional images of bio-tissues with a few mum spatial resolution. We have previously demonstrated the application of OCT for in vitro analysis of dental restoration of enamel. In this work, we report in vivo application of OCT to assess dental restorations. After approval from the Ethical Committee on Human Research at the Universidade Federal de Pernambuco, thirty patients with resin based composite restorations performed in anterior teeth during the period between 2000 and 2007 were selected for examination. These patients, both male and female, between the ages of 18 and 45, were clinically evaluated, and OCT was performed. The results were analyzed with respect to the integrity and marginal adaptation of the restoration. Images were obtained using OCT operating in the spectral domain, with a 840 nm superluminescent diode lightsource (spectral width of 50 nm, fiber output power 25mW and a measured spatial resolution of 10 mum). The image acquisition time was less than one second. The left hand side shows the gingiva, and the right hand side, the enamel. The region within the circle clearly shows the fail in the resin dental composite restoration. Using appropriate software, the lesioned region can be located exactly and a new restoration procedure can be carried out. In summary, we have shown that OCT is more than adequate in clinical practice to assess dental restorations.

Optical coherence tomography (OCT) offers a noninvasive method for the diagnosis of retinopathy. The OCT machine can capture retinal crosssectional images from which the retinal thickness can be calculated. Although OCT is widely used in clinical practice, its application in basic research is not as prevalent, especially in small animals such as mice. Because of the small size of their eyeballs, it is challenging to conduct fundus imaging examinations in mice. Therefore, a specialized retinal imaging system is required to accommodate OCT imaging on small animals. This article demonstrates a small-animal-specific system for OCT examination procedures and a detailed method for image analysis. The results of retinal OCT examination of very-low-density lipoprotein receptor (Vldlr) knockout mice and C57BL/6J mice are presented. The OCT images of C57BL/6J mice showed retinal layers, while those of Vldlr knockout mice showed subretinal neovascularization and retinal thinning. In summary, OCT examination could facilitate the noninvasive detection and measurement of retinopathy in mouse models.

Optical coherence tomography (OCT) is a nondestructive imaging modality with the potential to make quantitative spatial measurements. OCT's noncontact nature, sensitivity to small refractive index mismatches, and micron-scale resolution make it attractive for contact lens metrology, specifically, measuring prism. Prism is defined as the maximum difference in thickness of the contact lens, measured over a full 360 deg of rotation, at a fixed distance from the contact lens edge. We develop and test a novel algorithm that automatically analyzes OCT images and calculates prism. Images are obtained using a Thorlabs OCT930SR OCT system. The OCT probe is fastened to an automated rotation stage that rotates 360 deg in small increments (typically 10 deg) to acquire OCT images of the edge of the contact lens around the entire circumference. The images are 1.6 mm in optical depth (512 pixels) and 2 mm wide (1000 pixels). Several sets of images are successfully analyzed. The prism measured for a toric lens is 42 microm, which is in line with design parameters. Thickness measurements are repeatable with a standard deviation of 0.5 microm and maximum range of 1.8 microm over ten image sets. This work demonstrates the possibility of using OCT to perform nondestructive contact lens metrology.

PurposeThis study aims to investigate the applicability of lower lid margin thickness (LLMT) measurements in adults with and without meibomian gland dysfunction (MGD) by optical coherence tomography (OCT) and keratograph.MethodsThis is a cross-sectional, observational study. A hundred and eight volunteers aged 20 to 79, including 68 MGD patients and 40 normal subjects, were recruited. Using OCT and keratograph to measure the LLMT from the posterior lash line to anterior edge or outer edge of the tear meniscus was separately performed two times by the same person.ResultsThe mean age of normal and MGD subjects was 50.5 ± 14.2 years and 55.8 ± 15.5 years, respectively. The LLMT with OCT and keratograph in MGD patients was significantly greater than that in normal subjects (1.06 ± 0.27 and 1.03 ± 0.25 mm vs. 0.90 ± 0.20 and 0.86 ± 0.16 mm, respectively). In both normal and MGD subjects, the tear meniscus height and LLMT with OCT were both greater than that with keratograph (P < 0.05), and intraclass correlation coefficient (ICC) demonstrated a good agreement in the LLMT measurements between two devices (ICC = 0.83 and 0.79, respectively). Additionally, the LLMT in MGD patients was appeared to be positively correlated with meiboscore (rs = 0.37, P = 0.002).ConclusionsThe OCT and keratograph were two reliable tools in the LLMT measurements, which may have potential applications for diagnosis and evaluation of MGD. Furthermore, we found that the LLMT measured by OCT was greater than that measured by keratograph.

This chapter targets application of Optical Coherence Tomography (OCT) for evaluation of retinal neurodegenerative changes in Parkinson Disease (PD) and three related disorders: Multisystem Atrophy (MSA), Lewy Body Disease (LBD), and Alzheimer’s disease (AD). In the early stages some of their phenomenology overlaps and they are difficult to differentiate from PD with simple instrumental diagnostic tools or by evaluation of clinical characteristics. All four neurodegenerative diseases (NDD) have hallmark proteinopathies, involving both the brain and the retina. This chapter reviews research which points to using OCT as a simple, inexpensive and easily available tool, in the diagnosis of PD. The data of some studies also suggest the possibility of using OCT in the differential diagnosis of PD, AD, LBD and MSA. OCT is promising as a non-invasive, quick and easily available tool for NDD differential diagnosis and disease monitoring and evaluation of response to treatment.

Takayasu’s arteritis (TA) is large vessel vasculitis affecting the aorta and its major branches. The annual incidence of systemic vasculitis approaches 40 per million adults worldwide. TA can result in myocardial infarction (MI), and this should therefore be differentiated from arteriosclerotic lesions. Optical coherence tomography (OCT) is increasingly used to assess coronary stent implantation and vessel healing following stent implantation. So far, the use of OCT with Takayasu’s disease has been described only once, and it was used for a left anterior descending coronary artery lesion. This is the first case report of the use of OCT with a TA patient providing peripheral arteritis. A 27-year-old woman with psoriasis and celiac disease was admitted to our hospital with typical chest pain. In the first electrocardiogram, ST-elevation in a VR lead and ST-depressions in the other leads were revealed. The patient reported night sweats and muscle weakness in the arms. Physical examination revealed blood pressure at 90/60 mm Hg and 80/50 mm Hg in the right and left arm, respectively. Pulse at both radial arteries was barely palpable. Murmurs above both subclavian arteries and both carotid arteries were heard with auscultation. Echocardiography revealed mild hypokinesis at the apex and septum segments. Serum troponin I and creatine kinase isoenzyme MB activity was elevated significantly to MI. Coronary angiography showed a 90% focal stenosis in the ostium of the left main coronary artery (LMCA) (Fig. 1A). Ticagrelor and acetylsalicylic acid were administered immediately. Afterwards the lesion was predilated with balloons and then a 4.0 × 8 mm drug eluting stent with everolimus was deployed with a good final result. Contrasted computed tomography (CT) of the aorta and its main branches revealed vessel wall thickening, together with left carotid and subclavian arteries stenosis. Corticosteroid and cyclophosphamide therapy was added to the treatment. After 3 months, the patient underwent angiography to check the stent in the LMCA and also a control angiography and OCT of both subclavian and axillary arteries. These revealed persistent stenosis in both subclavian and right axillary arteries (Fig. 1B, C) and no restenosis in LMCA. OCT revealed intima–media thickness up to 0.75 mm over long distance without atheromatous plaque (Fig. 2). Due to lack of a proper drug-eluting balloon (DEB) for the patient the procedure was postponed. After a few weeks information was received that the patient had died due to massive MI whilst in her home city. Histological lesions in large vessel arteritis involve all layers of the arterial wall: intimal hyperplasia, medial degeneration, adventitial fibrosis, and mononuclear cellular infiltration lead to lack of a clear intima–media border. TA is an inflammatory disease, so anti-inflammatory drugs can reduce the lesions. Therefore, in peripheral arteries, the deployment of a DEB rather than stent implantation should be considered. When a culprit lesion involves the LMCA treatment with only a DEB is not acceptable. Our report provides essential knowledge concerning how an artery can look in large vessel arteritis as opposed to arteriosclerosis. The images can provide rare but important knowledge concerning peripheral and coronary diseases.

Comparative Study of Conventional and Ultrahigh-resolution Optical Coherence Tomography Imaging in Esophageal Neoplasia

Objective To evaluate the application of the spectral domain optical coherence tomography in macular diseases.Methods Retrospective analysis the data of spectral domain optical coherence tomography which from 49 patients with macular diseases whom were received treatment from 13th May 2010 to 13th June 2010 at department of ophthalmology in Guangdong General Hospital.Results The 49 patients' OCT examination images showed characteristic morphological changes in different macular diseases.Conclusions Spectral domain optical coherence tomography is a reliable and noninvasive examination method for the diagnosis of macular disease and for the follow up procedure. Key words: Optical coherence tomography; Spectral domain; Macular

In this paper, we review the current state of technology development and clinical applications of endoscopic optical coherence tomography (OCT). Key design and engineering considerations are discussed for most OCT endoscopes, including side-viewing and forward-viewing probes, along with different scanning mechanisms (proximal-scanning versus distal-scanning). Multi-modal endoscopes that integrate OCT with other imaging modalities are also discussed. The review of clinical applications of endoscopic OCT focuses heavily on diagnosis of diseases and guidance of interventions. Representative applications in several organ systems are presented, such as in the cardiovascular, digestive, respiratory, and reproductive systems. A brief outlook of the field of endoscopic OCT is also discussed.

This review aims to summarize the latest application of optical coherence tomography (OCT) in oral mucosal diseases, promoting an accurate and earlier diagnosis of such disorders, which are difficult to be differentiated. References on the application of OCT in oral mucosal diseases were mainly obtained from PubMed, Embase, Web of Science and Scopus databases, using the keywords: "optical coherence tomography and 'oral mucosa/oral cancers/oral potentially malignant diseases/oral lichen planus/oral leukoplakia/oral erythroplakia/discoid lupus erythematosus/oral autoimmune bullous diseases/oral ulcers/erythema multiforme/oral mucositis'". It is found that OCT is showing a promising application potential in the early detection, diagnosis, differential diagnosis, monitoring of oral cancer and oral dysplastic lesions, as well as the delineation of tumor margins. OCT is also playing an increasingly important role in the diagnosis of oral potentially malignant disorders, oral mucosal bullous diseases, oral ulcerative diseases, erythema multiforme, and the early detection of oral mucositis. Optical coherence tomography, as a novel optical technique featured by real-time, noninvasive, dynamic and high-resolution imaging, is of great use to serve as an adjunct tool for the diagnosis, differential diagnosis, monitoring and therapy evaluation of oral mucosal diseases.

Optical coherence tomography (OCT) is a new non-invasive approach for real-time in vivo tissue characterization. A promising use of OCT can be the assessment of the architecture of lesions with some degree of inhomogeneities, such as vascular lesions. Knowledge of the size and depth of the vascular structures can be useful for the diagnosis and for choosing the best treatment. The purpose of this study was to investigate a series of vascular lesions by means of OCT in order to obtain new insights into the non-invasive, pre-operative analysis of these lesions. Seven vascular lesions were included in the study. Histopathological diagnosis showed two haemangiomas and one haemolymphangioma; the remaining four cases were classified as haemangiomas on the basis of their clinical appearance. In all lesions, OCT analysis was able to visualize different areas of the lesion from the horny layer to the dermis showing a clear image of the vascular proliferation. Specifically, oval to roundish signal-poor areas sharply demarcated by a surrounding signal-rich layer were observed in good correlation with histopathology. The analysis of vascular lesions by OCT provides a new insight into non-invasive diagnosis and can be helpful in the selection of the most appropriate treatment.