1. 1-24 of 283 1 2 3 4 ... 10 11 12 »
    1. 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 ...

      Read Full Article
    2. 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 ...

      Read Full Article
    3. 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 ...

      Read Full Article
    4. 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 ...

      Read Full Article
    5. 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 ...

      Read Full Article
    6. 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 ...

      Read Full Article
    7. 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 ...

      Read Full Article
    8. 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 ...

      Read Full Article
    9. Optimized Optical Coherence Tomography Imaging With Hough Transform-Based Fixed-Pattern Noise Reduction

      Optimized Optical Coherence Tomography Imaging With Hough Transform-Based Fixed-Pattern Noise Reduction

      Fixed-pattern noise seriously affects the clinical application of optical coherence tomography (OCT), especially, in the imaging of tumorous tissue. We propose a Hough transform-based fixed-pattern noise reduction (HTFPNR) method to reduce the fixed-pattern noise for optimizing imaging of tumorous tissue with OCT system. Using by the HTFPNR method, we detect and map the outline of fixed-pattern noise in the OCT images, and finally efficiently reduce the fixed-pattern noise by the longitudinal and horizontal intelligent processing procedure. We adopt the image-to-noise ratio with full information (INRfi) and the noise reduction ratio (NRR) to evaluate the outcome of fixed-pattern noise reduction ratio ...

      Read Full Article
    10. Optimized Automated Segmentation and 3D Reconstruction Using Intracoronary Optical Coherence Tomography

      Optimized Automated Segmentation and 3D Reconstruction Using Intracoronary Optical Coherence Tomography

      Real time segmentation and three-dimensional (3D) reconstruction of the coronary arteries is challenging and limited by the increased computational time of the developed computer-aided methods. We present a novel and time-efficient method for intracoronary lumen detection which produces 3D coronary arteries using Optical Coherence Tomographic (OCT) images. OCT images are acquired for multiple patients and longitudinal cross-section (LOCS) images are reconstructed using different acquisition angles. The lumen contours for each LOCS image are extracted and translated to 2D cross-sectional images. Using two angiographic projections the centerline of the coronary vessel is reconstructed in 3D and the detected 2D contours are ...

      Read Full Article
    11. Common-path Optical Coherence Tomography using Bessel Beam from Negative Axicon Optical Fiber Tip

      Common-path Optical Coherence Tomography using Bessel Beam from Negative Axicon Optical Fiber Tip

      In this work a deep-seated negative axicon fiber tip (DSNA-FT) generating Bessel-Gauss beam is proposed as an optical probe for common-path optical coherence tomography (CPOCT) imaging. The axicon at the optical fiber tip is fabricated by etching the tip of a selective optical fiber in hydrofluoric acid under the influence of capillary action. The non-diffracting type quasi Bessel beam from the DSNA-FT having a long depth of field, ~0.7 mm, is used for CPOCT imaging of different type of samples i.e. sticky tape, fish scale, and rice grain. The CPOCT with unique and simple optical fiber probe has ...

      Read Full Article
    12. Use of Optical Clearing Agents for Imaging Root Surfaces With Optical Coherence Tomography

      Use of Optical Clearing Agents for Imaging Root Surfaces With Optical Coherence Tomography

      The diagnosis of root caries and root fractures is of increasing importance due to our aging population. The objective of this study is to show that optical clearing agents can be used to increase the visibility of subsurface structures in tooth roots to aid in the diagnosis of root caries depth and extension and to differentiate from subsurface defects. Previous studies have shown that high refractive index fluids can increase the depth penetration of optical coherence tomography (OCT) for imaging caries lesions on tooth enamel. Extracted teeth with suspected root caries were imaged with (OCT) with and without the addition ...

      Read Full Article
    13. Real-time digital signal processing-based optical coherence tomography and Doppler optical coherence tomography

      Real-time digital signal processing-based optical coherence tomography and Doppler optical coherence tomography

      We present the development and use of a real-time digital signal processing (DSP)-based optical coherence tomography (OCT) and Doppler OCT system. Images of microstructure and transient fluid-flow profiles are acquired using the DSP architecture for real-time processing of computationally intensive calculations. This acquisition system is readily configurable for a wide range of real-time signal processing and image processing applications in OCT.

      Read Full Article
    14. Viscosity monitoring during hemodiluted blood coagulation using optical coherence elastography

      Viscosity monitoring during hemodiluted blood coagulation using optical coherence elastography

      Rapid and accurate clot diagnostic systems are needed for the assessment of hemodiluted blood coagulation. We develop a real-time optical coherence elastography (OCE) system, which measures the attenuation coefficient of a compressional wave induced by a piezoelectric transducer (PZT) in a drop of blood using optical coherence tomography (OCT), for the determination of viscous properties during the dynamic whole blood coagulation process. Changes in the viscous properties increase the attenuation coefficient of the sample. Consequently, dynamic blood coagulation status can be monitored by relating changes of the attenuation coefficient to clinically relevant coagulation metrics, including the initial coagulation time and ...

      Read Full Article
    15. A New Framework for the Integrative Analytics of Intravascular Ultrasound and Optical Coherence Tomography Images

      A New Framework for the Integrative Analytics of Intravascular Ultrasound and Optical Coherence Tomography Images

      The integrative analysis of multimodal medical images plays an important role in the diagnosis of coronary artery disease by providing additional comprehensive information that cannot be found in an individual source image. Intravascular Ultrasound (IVUS) and Optical Coherence Tomography (IV-OCT) are two imaging modalities that have been widely used in the medical practice for the assessment of arterial health and the detection of vascular lumen lesions. IV-OCT has a high resolution and poor penetration, while IVUS has a low resolution and high detection depth. This paper proposes a new approach for the fusion of intravascular ultrasound and optical coherence tomography ...

      Read Full Article
    16. Evaluating micro-optical coherence tomography (μOCT) as a feasible imaging tool for pancreatic disease diagnosis

      Evaluating micro-optical coherence tomography (μOCT) as a feasible imaging tool for pancreatic disease diagnosis

      Pancreatic cancer is one of the leading causes of cancer mortality worldwide due to the lack of reliable tools for early diagnosis of this cancer. In this study, we evaluated the feasibility of micro-optical coherence tomography (μOCT) as an imaging tool for the diagnosis of pancreatic cancers. Specifically, we constructed a μOCT device that achieves a resolution of ∼1.67 μm and 1.79 μm in axial and lateral directions, respectively, and acquires three-dimensional μOCT images of mouse, rat and human pancreatic specimens ex vivo. We compared the results of μOCT with those of the corresponding histology. In μOCT images ...

      Read Full Article
    17. Fully Automated Segmentation of Fluid/Cyst Regions in Optical Coherence Tomography Images With Diabetic Macular Edema Using Neutrosophic Sets and Graph Algorithms

      Fully Automated Segmentation of Fluid/Cyst Regions in Optical Coherence Tomography Images With Diabetic Macular Edema Using Neutrosophic Sets and Graph Algorithms

      This paper presents a fully automated algorithm to segment fluid-associated (fluid-filled) and cyst regions in optical coherence tomography (OCT) retina images of subjects with diabetic macular edema. The OCT image is segmented using a novel neutrosophic transformation and a graph-based shortest path method. In neutrosophic domain, an image g is transformed into three sets: T (true), I (indeterminate) that represents noise, and F (false). This paper makes four key contributions. First, a new method is introduced to compute the indeterminacy set I , and a new λ -correction operation is introduced to compute the set T in neutrosophic domain. Second, a graph ...

      Read Full Article
    18. Magnetomotive Displacement of the Tympanic Membrane using Magnetic Nanoparticles: Toward Enhancement of Sound Perception

      Magnetomotive Displacement of the Tympanic Membrane using Magnetic Nanoparticles: Toward Enhancement of Sound Perception

      Objective: A novel hearing-aid scheme using magnetomotive nanoparticles (MNPs) as transducers in the tympanic membrane (TM) is proposed, aiming to noninvasively and directly induce a modulated vibration on the TM. Methods: In this feasibility study, iron-oxide (Fe<sub>3</sub>O<sub>4</sub>) nanoparticles were applied on ex vivo rat TM tissues and allowed to diffuse over ~2 hr. Subsequently, magnetic force was exerted on the MNP-laden TM via a programmable electromagnetic solenoid to induce the magnetomotion. Optical coherence tomography (OCT), along with its phase-sensitive measurement capabilities, was utilized to visualize and quantify the nanometer-scale vibrations generated on the ...

      Read Full Article
    19. Macular OCT Classification Using a Multi-Scale Convolutional Neural Network Ensemble

      Macular OCT Classification Using a Multi-Scale Convolutional Neural Network Ensemble

      Computer-aided diagnosis (CAD) of retinal pathologies is a current active area in medical image analysis. Due to the increasing use of retinal optical coherence tomography (OCT) imaging technique, a CAD system in retinal OCT is essential to assist ophthalmologist in the early detection of ocular diseases and treatment monitoring. This paper presents a novel CAD system based on a multi-scale convolutional mixture of expert (MCME) ensemble model to identify normal retina, and two common types of macular pathologies, namely, dry age-related macular degeneration, and diabetic macular edema. The proposed MCME modular model is a data-driven neural structure, which employs a ...

      Read Full Article
    20. Pixel-Reassigned Spectral-Domain Optical Coherence Tomography

      Pixel-Reassigned Spectral-Domain Optical Coherence Tomography

      A novel method of pixel reassignment (PRA) is proposed to achieve transverse superresolution in the confocal microscopy. Inspired by it, for the first time, we report a pixel-reassigned spectral-domain optical coherence tomography (OCT) with ∼ 1.5 times transverse resolution improvement both in numerical simulations and imaging experiments. PRA is implemented by transversely shifting the detection fiber from the on-axis position to five off-axis positions, capturing cross-sectional images at each shifting step of the detection fiber and digitally reassigning them together to give a sharper image with moderately extended depth of focus and enhanced intensity. So, we believe that the PRA ...

      Read Full Article
    21. In Vivo Fascicle Bifurcation Imaging of Rat Sciatic Nerve Using Swept-Source Optical Coherence Tomography

      In Vivo Fascicle Bifurcation Imaging of Rat Sciatic Nerve Using Swept-Source Optical Coherence Tomography

      The sciatic nerve is the longest and widest single nerve in the human body and is responsible for the signal transduction of the entire hind limb region. Its wide nerve dynamic range and size makes it sensitive to injury. The branching and location of the sciatic nerve are important, and unlike histology, optical coherence tomography (OCT) can provide rapid non-destructive cross-sectional images. The sciatic nerves of ten rats were analyzed using swept-source (SS)-OCT. The sufficient depth penetration of the SS-OCT system allowed clear identification of the internal bifurcation point of the external branching and the internal route for the ...

      Read Full Article
    22. Conjugate transformation for dispersion compensation in optical coherence tomography imaging

      Conjugate transformation for dispersion compensation in optical coherence tomography imaging

      In optical coherence tomography (OCT), the sample dispersion tends to increase the signal width and hence lower down the resolution, resulting in serious image quality degradation, especially for imaging over a large depth range or media with large dispersion coefficient. In this letter, instead of the conventional Fourier transformation for dispersion compensation that can compensate the image only ideally at a certain depth, a novel transformation, as called conjugate transformation, is proposed to achieve high resolution at all depth by utilizing the conjugate function of the signal itself as an optimized integral kernel. A large dispersion media of ZnSe is ...

      Read Full Article
    23. Multi-Scale Segmentation and Surface Fitting for Measuring 3-D Macular Holes

      Multi-Scale Segmentation and Surface Fitting for Measuring 3-D Macular Holes

      Macular holes are blinding conditions, where a hole develops in the central part of retina, resulting in reduced central vision. The prognosis and treatment options are related to a number of variables, including the macular hole size and shape. High-resolution spectral domain optical coherence tomography allows precise imaging of the macular hole geometry in three dimensions, but the measurement of these by human observers is time-consuming and prone to high inter- and intra-observer variability, being characteristically measured in 2-D rather than 3-D. We introduce several novel techniques to automatically retrieve accurate 3-D measurements of the macular hole, including: surface area ...

      Read Full Article
    24. Speckle Removal Using Diffusion Potential for Optical Coherence Tomography Images

      Speckle Removal Using Diffusion Potential for Optical Coherence Tomography Images

      We propose a fast and accurate solution to speckle reduction targeted specifically at optical coherence tomography images. The proposed speckle removing filter is designed using a novel potential function based on the gradient of the local variance of intensity. After filtering, the spatially neighboring pixels with close values of intensities converge to uniform gray values while the edges remain intact. This filtering process results in removal of speckle without destroying the edges of the desired object. The proposed filter also prevents the generation of any false edges. Detailed experimental analysis shows at least 1 dB improvement in peak signal-to-noise ratio ...

      Read Full Article
    1-24 of 283 1 2 3 4 ... 10 11 12 »
  1. Categories

    1. Applications:

      Art, Cardiology, Dentistry, Dermatology, Developmental Biology, Gastroenterology, Gynecology, Microscopy, NDE/NDT, Neurology, Oncology, Ophthalmology, Other Non-Medical, Otolaryngology, Pulmonology, Urology
    2. Business News:

      Acquisition, Clinical Trials, Funding, Other Business News, Partnership, Patents
    3. Technology:

      Broadband Sources, Probes, Tunable Sources
    4. Miscellaneous:

      Jobs & Studentships, Student Theses, Textbooks