1. 1-24 of 303 1 2 3 4 ... 11 12 13 »
    1. Flexible needle with integrated optical coherence tomography probe for imaging during transbronchial tissue aspiration

      Flexible needle with integrated optical coherence tomography probe for imaging during transbronchial tissue aspiration

      Transbronchial needle aspiration (TBNA) of small lesions or lymph nodes in the lung may result in nondiagnostic tissue samples. We demonstrate the integration of an optical coherence tomography (OCT) probe into a 19-gauge flexible needle for lung tissue aspiration. This probe allows simultaneous visualization and aspiration of the tissue. By eliminating the need for insertion and withdrawal of a separate imaging probe, this integrated design minimizes the risk of dislodging the needle from the lesion prior to aspiration and may facilitate more accurate placement of the needle. Results from in situ imaging in a sheep lung show clear distinction between ...

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    2. Phase and amplitude correction in polygon tunable laser-based optical coherence tomography

      Phase and amplitude correction in polygon tunable laser-based optical coherence tomography

      Phase instability is a serious problem in swept-source optical coherence tomography (OCT) with polygon tunable lasers; however, these devices have additional issues. We found that polygon tunable lasers also have fluctuations in output power and sweep range: the former creates artifacts that may impair the recognition of sample information, and the latter reduces the interference signal utilization during phase correction. We demonstrate a method that uses the calibration signal to quantify these problems and improve system stability and image quality. The proposed amplitude correction and phase correction methods are used to eliminate vertical artifacts and improve the resolution of OCT ...

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    3. Tissue characterization with depth-resolved attenuation coefficient and backscatter term in intravascular optical coherence tomography images

      Tissue characterization with depth-resolved attenuation coefficient and backscatter term in intravascular optical coherence tomography images

      An important application of intravascular optical coherence tomography (IVOCT) for atherosclerotic tissue analysis is using it to estimate attenuation and backscatter coefficients. This work aims at exploring the potential of the attenuation coefficient, a proposed backscatter term, and image intensities in distinguishing different atherosclerotic tissue types with a robust implementation of depth-resolved (DR) approach. Therefore, the DR model is introduced to estimate the attenuation coefficient and further extended to estimate the backscatter-related term in IVOCT images, such that values can be estimated per pixel without predefining any delineation for the estimation. In order to exclude noisy regions with a weak ...

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    4. Evaluating biomechanical properties of murine embryos using Brillouin microscopy and optical coherence tomography

      Evaluating biomechanical properties of murine embryos using Brillouin microscopy and optical coherence tomography

      Embryogenesis is regulated by numerous changes in mechanical properties of the cellular microenvironment. Thus, studying embryonic mechanophysiology can provide a more thorough perspective of embryonic development, potentially improving early detection of congenital abnormalities as well as evaluating and developing therapeutic interventions. A number of methods and techniques have been used to study cellular biomechanical properties during embryogenesis. While some of these techniques are invasive or involve the use of external agents, others are compromised in terms of spatial and temporal resolutions. We propose the use of Brillouin microscopy in combination with optical coherence tomography (OCT) to measure stiffness as well ...

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    5. Simultaneous en-face imaging of multiple layers with multiple reference optical coherence tomography

      Simultaneous en-face imaging of multiple layers with multiple reference optical coherence tomography

      A technique based on multiple reference optical coherence tomography (MR-OCT) is proposed for simultaneous imaging at multiple depths. The technique has been validated by imaging a reference sample and a fingerprint in-vivo. The principle of scanning multiple selected layers is shown by imaging a partial fingerprint with 200×200×200 voxels of 3×3×0.5  mm size and obtaining an arbitrary amount of layers merely by digital processing. The spacing among the layers can be adjusted arbitrarily, and the SNR roll-off is shown for three different spacings. At a mirror scan frequency of 1 kHz and an A-line rate ...

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    6. Application of a long-range swept source optical coherence tomography-based scheme for dimensional characterization of multilayer transparent objects

      Application of a long-range swept source optical coherence tomography-based scheme for dimensional characterization of multilayer transparent objects

      This work presents the use of a recently developed interferometric system based on the swept source optical coherence tomography (SS-OCT) technique, which allows the characterization of transparent and semitransparent multilayer systems employing a tunable fiber-optic laser with a coherence length suitable for achieving long-deep range imaging (<10  cm). The inclusion of fiber Bragg gratings in the system allows it to perform a self-calibration in each sweep of the light source. Measurements carried out on cuvettes, ampoules, small bottles, and glass containers used in the pharmaceutical industry are presented. The thicknesses of the walls and the distance between them were determined ...

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    7. Applicability of quantitative optical imaging techniques for intraoperative perfusion diagnostics: a comparison of laser speckle contrast imaging, sidestream dark-field microscopy, and optical coherence tomography

      Applicability of quantitative optical imaging techniques for intraoperative perfusion diagnostics: a comparison of laser speckle contrast imaging, sidestream dark-field microscopy, and optical coherence tomography

      . Patient morbidity and mortality due to hemodynamic complications are a major problem in surgery. Optical techniques can image blood flow in real-time and high-resolution, thereby enabling perfusion monitoring intraoperatively. We tested the feasibility and validity of laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), and sidestream dark-field microscopy (SDF) for perfusion diagnostics in a phantom model using whole blood. Microvessels with diameters of 50, 100, and 400 μm were constructed in a scattering phantom. Perfusion was simulated by pumping heparinized human whole blood at five velocities (0 to 20 mm∕s). Vessel diameter and blood flow velocity were assessed ...

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    8. Reform and practice of optical coherence tomography (OCT) system-driven teaching for optoelectronic instrument principle and design

      Reform and practice of optical coherence tomography (OCT) system-driven teaching for optoelectronic instrument principle and design

      Optoelectronic instrument principle and design includes the optical, mechanical, electrical and count modules for one system. We change traditional mode of customary specialty course design for only taking the cell design ability into account. Optical coherence tomography (OCT) can provide high-resolution 3D imaging system and wide application for tissue in vivo. In this work, we carry out OCT system– driven teaching into execution in the course design teaching, and decompose OCT system into four modules for teaching progress. The reform is not only cultivating student design ability based on OCT system exploitation, improving the engineering ability, but also help scientific ...

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    9. Feasibility and methodology of optical coherence tomography imaging of human intracranial aneurysms: ex vivo pilot study

      Feasibility and methodology of optical coherence tomography imaging of human intracranial aneurysms: ex vivo pilot study

      Rupture of intracranial aneurysm is a common cause of subarachnoid hemorrhage. An aneurysm may undergo microscopic morphological changes or remodeling of the vessel wall prior to rupture, which could potentially be imaged. In this study we present methods of tissue sample preparation of intracranial aneurysms and correlation between optical coherence tomography imaging and routine histology. OCT has a potential future in the assessment of microscopic features of aneurysms, which may correlate to the risk of rupture.

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    10. 4D imaging of embryonic chick hearts by streak-mode Fourier domain optical coherence tomography

      4D imaging of embryonic chick hearts by streak-mode Fourier domain optical coherence tomography

      Recently, we developed the streak-mode Fourier domain optical coherence tomography (OCT) technique in which an area-scan camera is used in a streak-mode to record the OCT spectrum. Here we report the application of this technique to in ovo imaging HH18 embryonic chick hearts with an ultrahigh speed of 1,016,000 axial scans per second. The high-scan rate enables the acquisition of high temporal resolution 2D datasets (1,000 frames per second or 1 ms between frames) and 3D datasets (10 volumes per second), without use of prospective or retrospective gating technique. This marks the first time that the embryonic ...

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    11. Simultaneous depth-resolved imaging of sub-nanometer scale ossicular vibrations and morphological features of the human-cadaver middle ear with spectral-domain phase-sensitive optical coherence tomography

      Simultaneous depth-resolved imaging of sub-nanometer scale ossicular vibrations and morphological features of the human-cadaver middle ear with spectral-domain phase-sensitive optical coherence tomography

      We describe a novel method for the detection of the tiny motions of the middle ear (ME) ossicles and their morphological features with a spectral-domain phase sensitive optical coherence tomography (PS-OCT). Laser Doppler Vibrometry (LDV) and its variations are the most extensively used methods for studding the vibrational modes of the ME. However, most techniques are limited to single point analysis methods, and do not have the ability to provide depth resolved simultaneous imaging of multiple points on the ossicles especially with the intact eardrum. Consequently, the methods have the limited ability to provide relative vibration information at these points ...

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    12. Quantitative comparison of hardware architectures for high-speed processing in optical coherence tomography

      Quantitative comparison of hardware architectures for high-speed processing in optical coherence tomography

      Several factors are spurring the development of hardware and software to accomplish high-speed processing for Optical Coherence Tomography (OCT). The two most prevalent architectures incorporate either an FPGA or a GPU. While GPUs have faster clock-speed the fact an FPGA can be pipelined makes a direct comparison based simply on system specifications difficult. We have undertaken an effort to make a direct comparison on the same host and consider the total time from digitization to rendering of the image. In addition to making quantitative comparisons between the two architectures we hope to derive useful benchmarks that will inform the design ...

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    13. Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

      Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

      Direct measurement of absolute vibration parameters from different locations within the mammalian organ of Corti is crucial for understanding the hearing mechanics such as how sound propagates through the cochlea and how sound stimulates the vibration of various structures of the cochlea, namely, basilar membrane (BM), recticular lamina, outer hair cells and tectorial membrane (TM). In this study we demonstrate the feasibility a modified phase-sensitive spectral domain optical coherence tomography system to provide subnanometer scale vibration information from multiple angles within the imaging beam. The system has the potential to provide depth resolved absolute vibration measurement of tissue microstructures from ...

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    14. Imaging of photothermal tissue expansion via phase sensitive optical coherence tomography

      Imaging of photothermal tissue expansion via phase sensitive optical coherence tomography

      Phase sensitive OCT enables the measurement of thermal expansion in laser irradiated material at high lateral and temporal resolution. In principle, a calculation of the 3D temperature distribution and its temporal evolution should be possible by evaluating the local expansion. This could be utilized for a non-invasive and very fast temperature measurement, e.g. to realize an online dosimetry for photocoagulation. The possibilities of quantitative investigations at high axial and lateral resolution are demonstrated by imaging the reversible thermal expansion in laser irradiated multilayer silicone phantoms.

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    15. Doppler streak mode Fourier domain optical coherence tomography

      Doppler streak mode Fourier domain optical coherence tomography

      Doppler Fourier domain optical coherence tomography is able to be used for in vivo blood flow measurement. In conventional methods, the highest velocity that can be measured is limited to the range the phase shift between two successively recorded depth profiles at the same probe-beam location, which cannot exceed (-π, π), otherwise phase wrapping will occur. This phase-wrapping limit is determined by the time interval between two consecutive A-scans. We present a novel approach to shorten the time interval between two consecutive A-scans and thus increase the phase-wrapping limit by using an area scan camera to record the interference spectrum ...

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    16. Advances in a fully integrated intravascular OCT-ultrasound system for cardiovascular imaging

      Advances in a fully integrated intravascular OCT-ultrasound system for cardiovascular imaging

      Intracoronary optical coherence tomography (OCT) and intravascular ultrasound (IVUS) are two popular techniques for the detection and determination of atherosclerosis. IVUS allows visualization of plaques while also providing a large penetration depth to determine plaque volume. Intracoronary OCT provides the ability to capture microscopic features associated with high risk plaque. Traditionally to utilize the benefits of both modalities, separate probes and systems had to be used one at a time to image a vessel. We present work required to create a combined OCT IVUS system capable of simultaneous imaging to detect atherosclerotic plaques. A novel integrated probe of size 0 ...

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    17. In vivo intracardiac OCT imaging through percutaneous access: Towards image guided radio-frequency ablation

      In vivo intracardiac OCT imaging through percutaneous access: Towards image guided radio-frequency ablation

      BACKGROUND Complete catheter-tissue contact and permanent tissue destruction are essential for efficient radio-frequency ablation (RFA) during cardiac arrhythmia treatment. Current methods of monitoring lesion formation are indirect and unreliable. We aim to develop optical coherence tomography (OCT) as an imaging guidance for RFA. OBJECTIVES The purpose of this study is to evaluate the feasibility of using OCT catheter to image endocardia wall in active beating hearts through percutaneous access. This is a critical step toward image guided RFA in a clinic setting. METHODS A cone-scanning forward-viewing OCT catheter was advanced into active beating hearts through percutaneous access in four swine ...

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    18. Broadband Fourier domain mode-locked laser for optical coherence tomography at 1060 nm

      Broadband Fourier domain mode-locked laser for optical coherence tomography at 1060 nm

      Optical coherence tomography (OCT) in the 1060nm range is interesting for in vivo imaging of the human posterior eye segment (retina, choroid, sclera) due to low absorption in water and deep penetration into the tissue. Rapidly tunable light sources, such as Fourier domain mode-locked (FDML) lasers, enable acquisition of densely sampled three-dimensional datasets covering a wide field of view. However, semiconductor optical amplifiers (SOAs)-the typical laser gain media for swept sources-for the 1060nm band could until recently only provide relatively low output power and bandwidth. We have implemented an FDML laser using a new SOA featuring broad gain bandwidth ...

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    19. Feasibiliy of optical detection of soft tissue deformation during needle insertion

      Feasibiliy of optical detection of soft tissue deformation during needle insertion

      Needles provide an effective way to reach lesions in soft tissue and are frequently used for diagnosis and treatment. Examples include biopsies, tumor ablation, and brachytherapy. Yet, precise localization of the needle with respect to the target is complicated by motion and deformation of the tissue during insertion. We have developed a prototypical needle with an embedded optical fiber allowing to obtain optical coherence tomography images of the tissue in front of the needle tip. Using the data and particularly the Doppler information it is possible to estimate the motion of the needle tip with respect to the surrounding soft ...

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    20. Image reconstruction from nonuniformly-spaced samples in Fourier domain optical coherence tomography

      Image reconstruction from nonuniformly-spaced samples in Fourier domain optical coherence tomography

      In this work, we use inverse imaging for object reconstruction from nonuniformly-spaced samples in Fourier domain optical coherence tomography (FD-OCT). We first model the FD-OCT system with a linear system of equations, where the source power spectrum and the nonuniformly-spaced sample positions are represented accurately. Then, we reconstruct the object signal directly from the nonuniformly-spaced wavelength measurements. With the inverse imaging method, we directly estimate the 2D cross-sectional object image instead of a set of independent A-line signals. By using the Total Variation (TV) as a constraint in the optimization process, we reduce the noise in the 2D object estimation ...

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    21. Optical coherence tomography in quantifying the permeation of human plasma lipoproteins in vascular tissues

      Optical coherence tomography in quantifying the permeation of human plasma lipoproteins in vascular tissues

      Atherosclerosis is the most common underlying cause of vascular disease, occurring in multiple arterial beds including the carotid, coronary, and femoral arteries. Atherosclerosis is an inflammatory process occurring in arterial tissue, involving the subintimal accumulation of low-density lipoproteins (LDL). Little is known about the rates at which these accumulations occur. Measurements of the permeability rate of LDL, and other lipoproteins such as high-density lipoprotein (HDL) and very low-density lipoprotein (VLDL), could help gain a better understanding of the mechanisms involved in the development of atherosclerotic lesions. The permeation of VLDL, LDL, HDL, and glucose was monitored and quantified in normal ...

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    22. Methodology for assessment of structural vibrations by spectral domain optical coherence tomography

      Methodology for assessment of structural vibrations by spectral domain optical coherence tomography

      Clinical diagnosis of cochlear dysfunction typically remains incomplete due to a lack of proper diagnostic methods. Medical imaging modalities can only detect gross changes in the cochlea, and non-invasive in vivo cochlear measurements are scarce. As a result, extensive efforts have been made to adapt optical coherence tomography (OCT) techniques to analyze and study the cochlea. Herein, we detail the methods for measuring vibration using OCT. We used spectral domain OCT with ~950 nm as the center wavelength and a bandwidth of ~80 nm. The custom spectrometer used was based on a high speed line scan camera which is capable ...

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    23. Incorporation of physical constraints in optimal surface search for renal cortex segmentation

      Incorporation of physical constraints in optimal surface search for renal cortex segmentation

      In this paper, we propose a novel approach for multiple surfaces segmentation based on the incorporation of physical constraints in optimal surface searching. We apply our new approach to solve the renal cortex segmentation problem, an important but not sufficiently researched issue. In this study, in order to better restrain the intensity proximity of the renal cortex and renal column, we extend the optimal surface search approach to allow for varying sampling distance and physical separation constraints, instead of the traditional fixed sampling distance and numerical separation constraints. The sampling distance of each vertex-column is computed according to the sparsity ...

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    24. Registration of 3D spectral OCT volumes combining ICP with a graph-based approach

      Registration of 3D spectral OCT volumes combining ICP with a graph-based approach

      The introduction of spectral Optical Coherence Tomography (OCT) scanners has enabled acquisition of high resolution, 3D cross-sectional volumetric images of the retina. 3D-OCT is used to detect and manage eye diseases such as glaucoma and age-related macular degeneration. To follow-up patients over time, image registration is a vital tool to enable more precise, quantitative comparison of disease states. In this work we present a 3D registrationmethod based on a two-step approach. In the first step we register both scans in the XY domain using an Iterative Closest Point (ICP) based algorithm. This algorithm is applied to vessel segmentations obtained from ...

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    1-24 of 303 1 2 3 4 ... 11 12 13 »
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