Obtained Optical Coherence Tomography Images Research Articles

Morphologic and Functional Changes of Macula and Optic Nerve Head in Adult Kidney Transplant Recipient

To assess macular and optic nerve head characteristics in patients after kidney transplantation using noninvasive optical coherence tomography (OCT) imaging. The study had a prospective character and was performed during period from November 2019 to November 2020 at the University Clinical Center Tuzla, Tuzla, Bosnia and Herzegovina, and included 59 patients with renal graft who underwent OCT. The obtained OCT images, pathologic changes on the fundus, including macula and optic nerve, were analyzed by reviewing nonparametric measures such as scanning laser ophthalmoscope, B-scan, 3D display, as well as parametric measurements such as central macular thickness, optic nerve head excavation, and retinal nerve thickness fiber (RNFL). There is a statistically significant difference in RNFL values (P=0.031) and cup to disc (P=0.002) ratio in relation to duration of graft. The highest average values of RNFL was in patients with creatinine clearance <30 mL/min, while average cup to disc ratio was lowest in patients with creatinine clearance >60 mL/min. Optic nerve head edema was bilateral in 9 and unilateral in 5 patients. Fundus examination also revealed changes on posterior segment, including retinal detachment (1 patient), bilateral macular edema (9 patients), unilateral macular edema (3 patients), central serous chorioretinopathy (2 patients), and macular pseudo hole (3 patients). Different retinal pathology is present in high incidence in patients secondary to renal transplant. Immunosuppressive therapy, older age, and comorbidities are the usual causes of these changes.

Automated combination of optical coherence tomography images and fundus images

We discuss approaches to combining multimodal multidimensional images, namely, three-dimensional optical coherence tomography (OCT) data and two-dimensional color images of the fundus. Registration of these two modalities can help to adjust the position of the obtained OCT images on the retina. Some existing approaches to matching fundus images are based on finding key points that are considered invariant to affine transformations and are common to the two images. However, errors in the identification of such points can lead to registration errors. There are also methods for iterative adjustment of conversion parameters, but they are based on some manual settings. In this paper, we propose a method based on a full or partial search of possible combinations of the OCT image transformation to find the best approximation of the true transformation. The best approximation is determined using a measure of comparison of preprocessed image pixels. Further, the obtained transformations are compared with the available true transformations to assess the quality of the algorithm. The structure of the work includes: pre-processing of OCT and fundus images with the extraction of blood vessels, random search or grid search over possible transformation parameters (shift, rotation and scaling), and evaluation of the quality of the algorithm.

Convolutional neural network-based automatic detection of follicle cells in ovarian tissue using optical coherence tomography

To preserve the fertility of young female cancer patients, ovarian tissue cryopreservation and transplantation have been investigated as next-generation reproductive medical technologies. Non-invasive visualization of follicles in ovarian tissue and cryopreservation of higher density tissue is essential for effective transplantation. We proposed the use of optical coherence tomography (OCT) that can noninvasively visualize the internal structure of the ovarian tissue. However, a method for quantifying cell density has not yet been established because of the lack of available techniques to visualize follicles noninvasively. We proposed the use of a convolutional neural network (CNN) to extract small features from medical images as an image analysis method to automatically detect follicles from the obtained OCT images. First, we collected a total of 13 ovarian tissues from four-day-old mice and acquired OCT images using a full-field-type OCT. Then, the acquired images were analyzed using three detection methods: filter processing, filter processing combined with the CNN, and only CNN. Finally, to verify the detection accuracy of each method, the detection rate and precision were calculated by taking the doctor’s detection as the correct result. The results showed that the detection method only using CNN achieved a detection rate of 0.81 and precision of 0.67; this indicated that follicles could be effectively detected using our proposed method. Furthermore, it is quantitatively evident that the density of follicles from the surface layer to the deep region differs depending on the tissue. In the future, these results could be used to detect follicles in tissues of different maturation stages and quantify follicles three-dimensionally, further accelerating next-generation reproductive medicine.

Optical coherence tomography guided carotid artery stent procedure: technique and potential applications

To (1) present a guide on how to perform optical coherence tomography (OCT) in carotid artery stenting (CAS), to (2) highlight several instructive cases illustrating OCT-guidance as an interventional strategy, and to (3) present the largest case-series of OCT-guided CAS performed in North America, demonstrating its feasibility as an imaging modality in this setting. OCT is an intravascular imaging method that captures images with an axial resolution 10 times higher than intravascular ultrasound. OCT has proven to be a useful modality in coronary angiography and may have similar applications in evaluating carotid atherosclerotic disease. We compared our experience in CAS utilizing OCT (40 patients) versus that of CAS without OCT guidance (52 patients). No strokes or deaths occurred in either group postprocedurally or at 12 months. Fluoroscopy time was reduced in the OCT arm (14 ± 1 vs. 16 ± 1 min). Postprocedural creatinine levels were identical (1 ± 0 mg/dl, P = 0.96). Procedure time (96 ± 8 vs. 80 ± 3 min, P = 0.06) and contrast use (94 ± 4 vs. 83 ± 4 ml, P = 0.05) was slightly elevated in the OCT arm. We established a standardized protocol to consistently obtain OCT images that helped guide interventional decision-making during CAS. OCT imaging in the carotids requires a higher contrast load and prolongs procedure time. However, it can be performed without significant increases in fluoroscopy time or negatively affecting renal function. There were no negative safety signals in this pilot study.

Monte Carlo simulation of optical coherence tomography signal of the skin nevus

Monte Carlo (MC) numerical simulation of light propagation in living tissue is widely used for characterization of optical coherence tomography (OCT) signals. Using MC simulation we obtained OCT images of skin with dysplastic nevus. Two various positions of skin nevus in depth were considered. Comparing these OCT simulation results with image of skin without nevus, we showed that OCT medical approach allows to detect dysplastic nevus at different stages of its life.

Bruch's Membrane Opening Minimum Rim Width and Retinal Nerve Fiber Layer Thickness in a Normal White Population: A Multicenter Study

Conventional optic disc margin-based neuroretinal rim measurements lack a solid anatomic and geometrical basis. An optical coherence tomography (OCT) index, Bruch's membrane opening minimum rim width (BMO-MRW), addresses these deficiencies and has higher diagnostic accuracy for glaucoma. We characterized BMO-MRW and peripapillary retinal nerve fiber layer thickness (RNFLT) in a normal population. Multicenter cross-sectional study. Normal white subjects. An approximately equal number of subjects in each decade group (20-90 years of age) was enrolled in 5 centers. Subjects had normal ocular and visual field examination results. We obtained OCT images of the optic nerve head (24 radial scans) and peripapillary retina (1 circular scan). The angle between the fovea and BMO center (FoBMO angle), relative to the horizontal axis of the image frame, was first determined and all scans were acquired and analyzed relative to this eye-specific FoBMO axis. Variation in BMO-MRW and RNFLT was analyzed with respect to age, sector, and BMO shape. Age-related decline and between-subject variability in BMO-MRW and RNFLT. There were 246 eyes of 246 subjects with a median age of 52.9 years (range, 19.8-87.3 years). The median FoBMO angle was -6.7° (range, 2.5° to -17.5°). The BMO was predominantly vertically oval with a median area of 1.74 mm(2) (range, 1.05-3.40 mm(2)). Neither FoBMO angle nor BMO area was associated with age or axial length. Both global mean BMO-MRW and RNFLT declined with age at a rate of -1.34 μm/year and -0.21 μm/year, equivalent to 4.0% and 2.1% loss per decade of life, respectively. Sectorially, the most rapid decrease occurred inferiorly and the least temporally; however, the age association was always stronger with BMO-MRW than with RNFLT. There was a modest relationship between mean global BMO-MRW and RNFLT (r = 0.35), whereas sectorially the relationship ranged from moderate (r = 0.45, inferotemporal) to nonexistent (r = 0.01, temporal). There was significant age-related loss of BMO-MRW in healthy subjects and notable differences between BMO-MRW and RNFLT in their relationship with age and between each other. Adjusting BMO-MRW and RNFLT for age and sector is important in ensuring optimal diagnostics for glaucoma.

An update on optical coherence tomography in dentistry

An update and overview of the use of optical coherence tomography (OCT) in dentistry is described. Specific aspects discussed include the evolution of the technology and the basic process of light beam interference used to obtain OCT images. In addition, aspects of the optical properties of dentine and enamel and the range of current diagnostic applications of OCT in dentistry are reviewed. The technique of optical coherence tomography is considered to be significant since the technology involved allows imaging using light to around 2-3 mm in teeth and can, for example, allow the extent and progression of carious lesions to be determined.

Elastographic mapping in optical coherence tomography using an unconventional approach based on correlation stability

An approach to elastographic mapping in optical coherence tomography (OCT) using comparison of correlation stability of sequentially obtained intensity OCT images of the studied strained tissue is discussed. The basic idea is that for stiffer regions, the OCT image is distorted to a smaller degree. Consequently, cross-correlation maps obtained with compensation of trivial translational motion of the image parts using a sliding correlation window can represent the spatial distribution of the relative tissue stiffness. An important advantage of the proposed approach is that it allows one to avoid the stage of local-strain reconstruction via error-sensitive numerical differentiation of experimentally determined displacements. Another advantage is that the correlation stability (CS) approach intrinsically implies that for deformed softer tissue regions, cross-correlation should already be strongly decreased in contrast to the approaches based on initial reconstruction of displacements. This feature determines a much wider strain range of operability than the proposed approach and is favorable for its free-hand implementation using the OCT probe itself to deform the tissue. The CS approach can be implemented using either the image elements reflecting morphological structure of the tissue or performing the speckle-level cross-correlation. Examples of numerical simulations and experimental demonstrations using both phantom samples and in vivo obtained OCT images are presented.

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We describe the recent use of Optical Coherence Tomography (OCT) for ocular fundus imaging diagnoses. OCT is a device for imaging the ocular fundus which previously could only be obtained non-invasively, as planar, sectional images similar to tissue slices observed under a light microscope. OCT is similar to ultrasonographic devices, except for the fact that low-interference waves at a near-infrared wavelength are used as to image the tissue, instead of ultrasound wave forms. Since its initial development, improvements, from the use of time domain OCT to spectral domain OCT, have now made it possible to obtain images more quickly and at a higher resolution. The latest Spectralis HRA+OCT is able to obtain OCT images, together with ocular fundus angiography images, which represent the standard approach for imaging diagnoses. OCT is useful for ascertaining and diagnosing the pathological conditions of ocular fundus diseases.

Contrasting properties of gold nanoshells and titanium dioxide nanoparticles for optical coherence tomography imaging of skin: Monte Carlo simulations and in vivo study

The effect of silica/gold nanoshells and titanium dioxide nanoparticles on the optical properties of skin is studied. By implementing in vivo measurements and Monte Carlo simulations, we analyze the efficiency of using these nanoparticles as contrasting agents for optical coherence tomography (OCT) imaging of skin. In vivo measurements are performed on pig skin, where nanoparticle suspension drops have been applied. The identification of skin layers is performed by comparison with corresponding histology images. Experimental results exhibit an increase in contrast of the obtained OCT images after a single nanoparticles application. Multiple applications do not lead to increase in the obtained contrast. To interpret the obtained experimental OCT images of skin and understand the mechanisms of contrasting, a set of Monte Carlo calculations is performed. The results of the simulations exhibit good qualitative agreement with the experimental images, and prove that the contrasting originates from the nanoparticles added, while the contrast of inclusion originates from the absence of nanoparticles within it and their presence in the surrounding area.

Optical Coherence Tomography as an Adjunct to White Light Cystoscopy for Intravesical Real-Time Imaging and Staging of Bladder Cancer

Optical coherence tomography (OCT) is a novel, real-time endoscopic imaging modality that permits delineation of microarchitectural features of bladder lesions. It may provide an extension of conventional cystoscopy by allowing noninvasive examination of bladder tissue at microscopic resolution (10 to 20 microm). The purpose of this study was to examine the application of OCT in augmenting the diagnosis and staging of bladder lesions. We conducted a retrospective institutional review board-approved, single-institution, single-user review on the use of OCT as an adjunct to conventional cystoscopy in 32 patients with a history of bladder cancer (24), primary tumor (6), prostate cancer (1), or hematuria (1). We obtained OCT images of suspicious areas before biopsy or resection, interpreted them in real time, and subsequently compared them with pathology results. We obtained 94 images in 32 patients undergoing bladder biopsy or transurethral resection of bladder tumor. Age of the patients ranged from 49 to 84 years (mean, 59 years), with 25 men (78%) and 7 women (22%). We correlated 38 suspicious areas with biopsy findings. OCT imaging correctly identified tumors confined to the mucosa with a sensitivity and specificity of 90% and 89%, respectively. Muscle-invasive tumors were detected in 7 of 7 lesions with 100% sensitivity, 90% specificity, and 92% accuracy. Optical coherence tomography is a rapid, easy-to-use tool that can help differentiate Ta and T1 tumors and identify muscle-invasive bladder tumors. It provides real-time microarchitectural information that can aid in the evaluation of bladder tumors and adjacent and remote urothelium.

Visualization of paper structure by optical coherence tomography: Monte Carlo simulations and experimental study

This paper analyzes the capability of an optical coherence tomography (OCT) setup to visualize paper structure by comparing experimental and Monte Carlo (MC) simulated OCT images. In the experiments, we used an OCT setup at 910 nm with the coherence length of an SLD source of 7.5 µm. Several different refractive index matching agents were applied to paper samples to enhance the visualization of their inner structure. The obtained OCT images show improved contrast in inner structure and enhanced visualization depth. A set of corresponding simulations were then performed using a previously developed MC code. A multilayer paper sheet model with non-planar fiber-air interfaces was developed to characterize the paper samples. MC simulations were carried out to study the effect of the setup parameters on the obtained OCT images. A comparison with the experimental data shows that the developed model provides a satisfactory correspondence between simulated and experimental images.

Use of optical coherence tomography in delineating airways microstructure: comparison of OCT images to histopathological sections

An ideal diagnostic system for the human airways should be able to detect and define early development of premalignant pathological lesions, to facilitate optimal curative treatment and prevent irreversible and/or invasive lung disease. There is great need for exploration of safe, repeatable imaging techniques which can run at real-time and with high spatial resolution. In this study, optical coherence tomography (OCT) was utilized to acquire cross-sectional images of upper and lower airways using fresh pig lung resections as a model system. Obtained OCT images were compared with parallel tissue characterization by conventional histological analysis. Our objective was to determine whether OCT differentiates the composite structural layers and inherent anatomical variations along different airway locations. The data show that OCT can clearly display the multilayered structure of the airways. The subtle architectural differences in three separate anatomical locations including trachea, main bronchus and tertiary bronchus were clearly delineated. Images of the appropriate anatomical profiles, with depth of up to 2 mm and 10 µm spatial resolution were obtained by our current OCT system, which was sufficient for recognition of the epithelium, subepithelial tissues and cartilage. In addition, the relative thickness of individual structural components was accurately reflected and comparable to histological sections. These data support OCT as a highly feasible, optical biopsy tool, which merits further exploration for early diagnosis of human airway epithelial pathology.