1. 1-24 of 300 1 2 3 4 ... 11 12 13 »
    1. Polarization-Sensitive Optical Coherence Tomography for Brain Tumor Characterization

      Polarization-Sensitive Optical Coherence Tomography for Brain Tumor Characterization

      Complete removal of brain tumor is of the most interest to a surgeon because the resection area directly relates to recurrence rate. Although there are many biomedical imaging modalities applied to locate the positions of tumors, they lack the spatial resolution to precisely delineate the boundary between brain tumor and normal brain tissues and are also inconvenient to be used intraoperatively. This study aims to examine the feasibility of the label-free, polarization-sensitive optical coherence tomography (PS-OCT) for distinguishing brain tumors from normal brain tissues. Ex vivo samples were obtained from two patients with grade II and II-III glioma; healthy porcine ...

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    2. Non-ionized, High-resolution Measurement of Internal and Marginal Discrepancies of Dental Prosthesis Using Optical Coherence Tomography

      Non-ionized, High-resolution Measurement of Internal and Marginal Discrepancies of Dental Prosthesis Using Optical Coherence Tomography

      An internal and marginal fit between prosthesis and abutment are important factors of the durability of dental prosthesis. In this study we have proposed the use of swept-source optical coherence tomography (SS-OCT) as a novel application for non-ionized and high-resolution measurements of internal and marginal discrepancies at anatomically critical four points, such as occlusal, angle, axial, and margin during prosthesis attachment. A tooth model was fabricated by 3D printing technique and the dental prosthesis was designed using dental CAD software. The cross-sectional images along with intensity peak profile analysis of the sample were acquired using OCT system for measurements of ...

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    3. Estimation of refractive index for biological tissue using micro-optical coherence tomography

      Estimation of refractive index for biological tissue using micro-optical coherence tomography

      The refractive index of biological tissue is required for investigating the tissue's optical properties. Efforts have been made to characterize refractive indices of biological tissues at a single wavelength, but it is more convenient to know the Cauchy's coefficients, which provide refractive index over a wide range of wavelengths. We demonstrate a method to noninvasively provide the Cauchy's dispersion coefficients of biological tissues using micro-optical coherence tomography. Using short-frequency Fourier transforms, the relative optical thickness of the sample in the wavelength range of the broadband source was obtained from interferograms. The coefficients of Cauchy's equation were ...

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    4. Large axial range frequency-domain optical low coherence interferometry

      Large axial range frequency-domain optical low coherence interferometry

      In this paper, we propose a new experimental setup to extend the measurement range of frequency-domain low coherence interferometry (FD-LCI) from 3 mm to 2 cm. The FD-LCI can be extended to the technique of frequency domain optical coherence tomography (FD-OCT) by performing additional lateral scanning. This new and simple arrangement just attaches an extra interferometer before the spectrometer in a typical FD-LCI setup. With this configuration, it is possible to overcome the limitation of the dynamic range of the conventional technique. This allows us to measure the optical path difference of the sample of interest, which is outside the ...

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    5. A Mechanical Approach for Smooth Surface Fitting to Delineate Vessel Walls in Optical Coherence Tomography Images

      A Mechanical Approach for Smooth Surface Fitting to Delineate Vessel Walls in Optical Coherence Tomography Images

      Automated analysis of vascular imaging techniques is limited by the inability to precisely determine arterial borders. Intravascular optical coherence tomography (OCT) offers unprecedented detail of artery wall structure and composition, but does not provide consistent visibility of the outer border of the vessel due to limited penetration depth. Existing interpolation and surface fitting methods prove insufficient to accurately fill the gaps between the irregularly-spaced and sometimes unreliably-identified visible segments of the vessel outer border. This paper describes an intuitive, efficient, and flexible new method of three-dimensional surface fitting and smoothing suitable for this task. An anisotropic linear-elastic mesh is fit ...

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    6. Non-destructive identification of weld-boundary and porosity formation during laser transmission welding by using optical coherence tomography

      Non-destructive identification of weld-boundary and porosity formation during laser transmission welding by using optical coherence tomography

      Laser transmission welding offers significant benefits over conventional welding techniques enabling single-stage rapid plastic joining. The quality of laser transmission welded products are commonly assessed by measuring the weld penetration depth, hardened weld boundary, and inspecting the formation of porosity. However, existing methods of verification are inevitably accompanied by destruction of the specimen. Thus, non-destructive quality assessment methods for laser transmission welding have gained attention recently. Here, we demonstrated an extended industrial application of 860 nm wavelength based spectral domain optical coherence tomography for the non-destructive inspection of the aforementioned quality parameters of laser transmission welded industrial plastic materials, i ...

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    7. Simultaneous Estimation of Corneal Topography, Pachymetry, and Curvature

      Simultaneous Estimation of Corneal Topography, Pachymetry, and Curvature

      dentification of objective criteria to correctly diagnose ectatic diseases of the cornea or to detect early stages of corneal ectasia is of great interest in ophthalmology and optometry. Metrics for diagnosis typically employed are curvature maps (axial/sagittal, tangential); elevation map of the anterior surface of the cornea with respect to a reference sphere; and pachymetry (thickness) map of the cornea. We present evidence that currently used curvature maps do not represent the actual curvatures (principal or mean) in a human cornea. A novel contribution of this paper is the computation of the true mean curvature over every point of ...

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    8. Imaging cellular structures of atherosclerotic coronary arteries using circumferentially scanning micro-optical coherence tomography fiber probe ex vivo

      Imaging cellular structures of atherosclerotic coronary arteries using circumferentially scanning micro-optical coherence tomography fiber probe ex vivo

      Development and progression of coronary atherosclerotic lesions is mediated by a number of cellular components, which are not readily visualized using the current clinical investigation tools. Visualizing these cellular components in situ and in vivo may allow early detection of the vulnerable plaques, with implications for coronary artery disease (CAD) therapy and for the prevention of acute myocardial infarction (AMI). In this study, we have developed a fiber-optic micro-optical coherence tomography (µOCT) probe for intravascular use. We conducted ex vivo imaging experiments in normal swine aorta and human atherosclerotic coronary arteries, and demonstrate that the fiber-probe based µOCT could delineate ...

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    9. Geometric Validation of Continuous, Finely-Sampled 3D Reconstructions from aOCT and CT in Upper Airway Models

      Geometric Validation of Continuous, Finely-Sampled 3D Reconstructions from aOCT and CT in Upper Airway Models

      Identification and treatment of obstructive airway disorders (OADs) is greatly aided by imaging of the geometry of the airway lumen. Anatomical optical coherence tomography (aOCT) is a promising high-speed and minimally-invasive endoscopic imaging modality for providing micrometer-resolution scans of the upper airway. Resistance to airflow in OADs is directly caused by reduction in luminal cross-sectional area (CSA). It is hypothesized that aOCT can produce airway CSA measurements as accurate as that from computed tomography (CT). Scans of machine hollowed cylindrical tubes were used to develop methods for segmentation and measurement of airway lumen in CT and aOCT. Simulated scans of ...

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    10. Quantitative evaluation of skin surface roughness using optical coherence tomography in vivo

      Quantitative evaluation of skin surface roughness using optical coherence tomography in vivo

      The quantitative monitoring of skin topography is important in the field of cosmetics and dermatology. The most widespread method for determining skin roughness in vivo is to use skin microrelief, PRIMOS device, which allows a noninvasive, fast and direct measurement of the skin surface. However, it has drawbacks, such as the interference of backscattering from volumetric skin and motion artifacts. In this study, we demonstrate the potential of OCT for providing reliable and quantitative skin surface roughness. In order to evaluate the performance of OCT for skin surface analysis, different types of skin phantoms were fabricated and measured. We utilized ...

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    11. A miniature endoscopic optical coherence tomography probe based on C-lens

      A miniature endoscopic optical coherence tomography probe based on C-lens

      We present a novel miniature endoscopic OCT probe based on an electrothermal microelectromechanical (MEMS) mirror and a C-lens. The MEMS mirror has a relatively large mirror plate of 0.5 mm×0.5 mm on a small chip size of 1.5 mm×1.3 mm, leading to the outer diameter of the endoscopic probe down to only 2.5 mm so that the probe is capable of being inserted through the biopsy channel of a conventional endoscope. A long focal length of 12 mm is achieved by properly designing the C-lens. Compared to commonly used GRIN lenses, C-lenses have ...

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    12. A Fully Automated 3D In-vivo Delineation and Shape Parameterization of the Human Lamina Cribrosa in Optical Coherence Tomography

      A Fully Automated 3D In-vivo Delineation and Shape Parameterization of the Human Lamina Cribrosa in Optical Coherence Tomography

      Objective: A fully automated method for delineation of the lamina cribrosa in optical coherence tomography (OCT) is proposed. It assesses the 3D shape of the lamina cribrosa in-vivo, based on a series of OCT B-scans. Methods: The algorithm has several image processing steps and it is based on active contour detection performed along three orthogonal directions of the B-scan data cuboid. Further, the delineated 3D lamina cribrosa shape is parameterized with a fourth-order polynomial of two variables, P[x, y] using the least-squares method. Data sets from a total of 255 subjects from three groups were analyzed: 92 primary open ...

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    13. Decreasing the Size of a Spectral Domain Optical Coherence Tomography System with Cascaded Arrayed Waveguide Gratings in a Photonic Integrated Circuit

      Decreasing the Size of a Spectral Domain Optical Coherence Tomography System with Cascaded Arrayed Waveguide Gratings in a Photonic Integrated Circuit

      This paper describes a proof-of-concept of a miniaturized spectral-domain optical coherence tomography system, based on photonic integrated circuit (PIC) technology. The integrated optics 512-channel spectrometer consists of cascaded arrayed waveguide gratings (AWG) with the output waveguides directly attached to a CCD detector. The spectrometer has a center wavelength of 850 nm and a spectral sampling interval of 0.22 nm. The PIC has a footprint of 2.0x2.7 cm2. The wavelength response of the cascaded AWG spectrometer is calibrated with a tunable laser. Free space OCT measurements are done with a mirror as sample. The signal-to-noise ratio is ~77 ...

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    14. Optical Coherence Tomography as an Oral Cancer Screening Adjunct in a Low Resource Settings

      Optical Coherence Tomography as an Oral Cancer Screening Adjunct in a Low Resource Settings

      Oral cancer is the sixth most common cancer worldwide, predominantly seen in low and middle-income countries (LMIC). Two thirds of all cases are detected at a late stage when prognosis and treatment outcomes are poor. Oral lesions are commonly detected by visual inspection, followed by invasive surgical biopsy and time consuming histopathological analysis. Optical Coherence Tomography (OCT), a minimally invasive tomographic imaging technology, can be used to non-invasively identify premalignant or malignant change in the oral mucosa. In this study, a mobile OCT imaging system was designed, constructed and tested for its performance as a point-of-care oral diagnostic device. Twenty ...

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    15. Establishment of an Automated Algorithm Utilizing Optical Coherence Tomography and Micro-Computed Tomography Imaging to Reconstruct the 3D Deformed Stent Geometry

      Establishment of an Automated Algorithm Utilizing Optical Coherence Tomography and Micro-Computed Tomography Imaging to Reconstruct the 3D Deformed Stent Geometry

      Percutaneous coronary intervention (PCI) is the prevalent treatment for coronary artery disease, with hundreds of thousands of stents implanted annually. Computational studies have demonstrated the role of biomechanics in the failure of vascular stents, but clinical studies is this area are limited by a lack of understanding of the deployed stent geometry, which is required to accurately model and predict the stent induced in vivo biomechanical environment. Herein, we present an automated method to reconstruct the 3D deployed stent configuration through the fusion of optical coherence tomography (OCT) and micro-computed tomography (μCT) imaging data. In an experimental setup, OCT and ...

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    16. Three Dimensional Full-Range Dual-Band Fourier Domain Optical Coherence Tomography Accelerated by Graphic Processing Unit

      Three Dimensional Full-Range Dual-Band Fourier Domain Optical Coherence Tomography Accelerated by Graphic Processing Unit

      The authors present a graphic processing unit (GPU) accelerated three-dimensional (3D) full-range dual-band Fourier domain optical coherence tomography (FD-OCT) using a LabVIEW GPU program with GPU-adaptable algorithms. GPU can dramatically reduce the image processing time, but programing on GPU is more complex than that on central processing unit (CPU). This work implements GPU computing interfaced with LabVIEW, using a LabVIEW GPU analysis toolkit, which significantly reduces the programing complexity. The selected algorithms are suitable for GPU computing in multi-band FD-OCT. The developed system overcomes the problem of long image processing time relative to data acquisition time in CPU. A 65 ...

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    17. Monitoring Acute Stroke in Mouse Model Using Laser Speckle Imaging-Guided Visible-Light Optical Coherence Tomography

      Monitoring Acute Stroke in Mouse Model Using Laser Speckle Imaging-Guided Visible-Light Optical Coherence Tomography

      Objective: Monitoring hemodynamic and vascular changes in the acute stages of mouse stroke models is invaluable in studying ischemic stroke pathophysiology. However, there lacks a tool to simultaneously and dynamically investigate these changes. Methods: We integrated laser speckle imaging (LSI) and visible-light optical coherence tomography (Vis-OCT) to reveal dynamic vascular responses in acute stages in the distal middle cerebral artery occlusion (dMCAO) model in rodents. LSI provides full-field, real-time imaging to guide Vis-OCT imaging and monitor the dynamic cerebral blood flow (CBF). Vis-OCT offers depth-resolved angiography and oxygen saturation (sO 2 ) measurements. Results: Our results showed detailed CBF and vasculature ...

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    18. Mapping and Quantitating Penetrating Vessels in Cortical Brain Using Eigen-Decomposition of OCT Signals and Subsequent Principal Component Analysis

      Mapping and Quantitating Penetrating Vessels in Cortical Brain Using Eigen-Decomposition of OCT Signals and Subsequent Principal Component Analysis

      Penetrating vessels bridge the mesh of communicating vessels on the surface of the cortex with the subsurface microvascular beds that feed the underlying neural tissue. Their accurate identification in vivo is important in the investigations of neural degenerative diseases, e.g., Alzheimer's disease and stroke. Here, we propose an efficient method to automatically map cortical penetrating vessels based on an eigen decompensation analysis of the optical coherence tomography (OCT) and OCT angiographic signals. We first project the ensemble of repeated OCT signals into a feature space that represents the power spectral components of eigenvectors through a well-known eigen-decomposition method ...

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    19. Automatically Determining the Confocal Parameters from OCT B-Scans for Quantification of the Attenuation Coefficients

      Automatically Determining the Confocal Parameters from OCT B-Scans for Quantification of the Attenuation Coefficients

      The attenuation coefficient is a relevant biomarker for many diagnostic medical applications. Recently, the Depth- Resolved Confocal (DRC) technique was developed to automatically estimate the attenuation coefficients from Optical Coherence Tomography (OCT) data with pixel-level resolution. However, DRC requires that the confocal function parameters (i.e., focal plane location and apparent Rayleigh range) be known a priori. In this paper we present the autoConfocal algorithm: a simple, automatic method for estimating those parameters directly from OCT imagery when the focal plane is within the sample. We present autoConfocal+DRC results on phantom data, ex-vivo biological tissue data, and in-vivo clinical ...

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    20. Extracting Blood Vessels From Full-Field OCT Data of Human Skin by Short-Time RPCA

      Extracting Blood Vessels From Full-Field OCT Data of Human Skin by Short-Time RPCA

      Recent advances in optical coherence tomography (OCT) lead to the development of OCT angiography to provide additional helpful information for diagnosis of diseases like basal cell carcinoma. In this paper, we investigate how to extract blood vessels of human skin from full-field OCT (FF-OCT) data using the robust principal component analysis (RPCA) technique. Specifically, we propose a short-time RPCA method that divides the FF-OCT data into segments and decomposes each segment into a low-rank structure representing the relatively static tissues of human skin and a sparse matrix representing the blood vessels. The method mitigates the problem associated with the slow-varying ...

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    21. Wavelength Dependence of Ultrahigh-Resolution Optical Coherence Tomography Using Supercontinuum for Biomedical Imaging

      Wavelength Dependence of Ultrahigh-Resolution Optical Coherence Tomography Using Supercontinuum for Biomedical Imaging

      Optical coherence tomography (OCT) is a noninvasive cross-sectional imaging technique with micrometer resolution. The theoretical axial resolution is determined by the center wavelength and bandwidth of the light source, and the wider the bandwidth, the higher the axial resolution. The characteristics of OCT imaging depend on the optical wavelength used. In this paper, we investigated the wavelength dependence of ultrahigh-resolution (UHR) OCT using a supercontinuum for biomedical imaging. Wideband, high-power, low-noise supercontinua (SC) were generated at λ = 0.8, 1.1, 1.3, and 1.7 μ m based on ultrashort pulses and nonlinear fibers. The wavelength dependence of OCT imaging was ...

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    22. Towards Robotic Eye Surgery: Marker-free, Online Hand-eye Calibration using Optical Coherence Tomography Images

      Towards Robotic Eye Surgery: Marker-free, Online Hand-eye Calibration using Optical Coherence Tomography Images

      Ophthalmic microsurgery is known to be a challenging operation, which requires very precise and dexterous manipulation. Image guided robot-assisted surgery (RAS) is a promising solution that brings significant improvements in outcomes and reduces the physical limitations of human surgeons. However, this technology must be further developed before it can be routinely used in clinics. One of the problems is the lack of proper calibration between the robotic manipulator and appropriate imaging device. In this work, we developed a flexible framework for hand-eye calibration of an ophthalmic robot with a microscope-integrated Optical Coherence Tomography (MI-OCT) without any markers. The proposed method ...

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    23. Automated Layer Segmentation of Retinal Optical Coherence Tomography Images Using a Deep Feature Enhanced Structured Random Forests Classifier

      Automated Layer Segmentation of Retinal Optical Coherence Tomography Images Using a Deep Feature Enhanced Structured Random Forests Classifier

      Optical coherence tomography (OCT) is a high-resolution and non-invasive imaging modality that has become one of the most prevalent techniques for ophthalmic diagnosis. Retinal layer segmentation is very crucial for doctors to diagnose and study retinal diseases. However, manual segmentation is often a time-consuming and subjective process. In this work, we propose a new method for automatically segmenting retinal OCT images, which integrates deep features and hand-designed features to train a structured random forests classifier. The deep convolutional features are learned from deep residual network. With the trained classifier, we can get the contour probability graph of each layer, finally ...

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    24. Surrogate-assisted Retinal OCT Image Classification Based on Convolutional Neural Networks

      Surrogate-assisted Retinal OCT Image Classification Based on Convolutional Neural Networks

      Optical Coherence Tomography (OCT) is becoming one of the most important modalities for the noninvasive assessment of retinal eye diseases. As the number of acquired OCT volumes increases, automating the OCT image analysis is becoming increasingly relevant. In this paper, we propose a surrogate-assisted classification method to classify retinal OCT images automatically based on convolutional neural networks (CNNs). Image denoising is first performed to reduce the noise. Thresholding and morphological dilation are applied to extract the masks. The denoised images and the masks are then employed to generate a lot of surrogate images, which are used to train the CNN ...

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    1-24 of 300 1 2 3 4 ... 11 12 13 »
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