1. 1-24 of 295 1 2 3 4 ... 11 12 13 »
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. 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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    15. 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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    16. 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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    17. Parallel graph search: application to intraretinal layer segmentation of 3-D macular OCT scans

      Parallel graph search: application to intraretinal layer segmentation of 3-D macular OCT scans

      Image segmentation is of paramount importance for quantitative analysis of medical image data. Recently, a 3-D graph search method which can detect globally optimal interacting surfaces with respect to the cost function of volumetric images has been introduced, and its utility demonstrated in several application areas. Although the method provides excellent segmentation accuracy, its limitation is a slow processing speed when many surfaces are simultaneously segmented in large volumetric datasets. Here, we propose a novel method of parallel graph search, which overcomes the limitation and allows the quick detection of multiple surfaces. To demonstrate the obtained performance with respect to ...

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    18. Efficient searching of globally optimal and smooth multisurfaces with shape priors

      Efficient searching of globally optimal and smooth multisurfaces with shape priors

      Despite extensive studies in the past, the problem of segmenting globally optimal multiple surfaces in 3D volumetric images remains challenging in medical imaging. The problem becomes even harder in highly noisy and edge-weak images. In this paper we present a novel and highly efficient graph-theoretical iterative method based on a volumetric graph representation of the 3D image that incorporates curvature and shape prior information. Compared with the graph-based method, applying the shape prior to construct the graph on a specific preferred shape model allows easy incorporation of a wide spectrum of shape prior information. Furthermore, the key insight that computation ...

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    19. Incorporation of texture-based features in optimal graph-theoretic approach with application to the 3D segmentation of intraretinal surfaces in SD-OCT volumes

      Incorporation of texture-based features in optimal graph-theoretic approach with application to the 3D segmentation of intraretinal surfaces in SD-OCT volumes

      While efficient graph-theoretic approaches exist for the optimal (with respect to a cost function) and simultaneous segmentation of multiple surfaces within volumetric medical images, the appropriate design of cost functions remains an important challenge. Previously proposed methods have used simple cost functions or optimized a combination of the same, but little has been done to design cost functions using learned features from a training set, in a less biased fashion. Here, we present a method to design cost functions for the simultaneous segmentation of multiple surfaces using the graph-theoretic approach. Classified texture features were used to create probability maps, which ...

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    20. Image diversity, shape modification with accommodation, dynamical change with accommodation, and age dependence of the ciliary body imaged by optical coherence tomography

      Image diversity, shape modification with accommodation, dynamical change with accommodation, and age dependence of the ciliary body imaged by optical coherence tomography

      For investigation of accommodation and presbyopia, the ciliary body and its dynamics were imaged with Optical Coherence Tomography (OCT) method. We used two OCT systems; a discretely-swept frequency-comb OCT with a center wavelength at 1.6Ɓ and ultra-fast spectral domain OCT with a center wavelength at 1.3μm. Measurements of dynamical modification of the ciliary body were carried out with ranging in age from 22 to 79. The OCT images and movies represent the changes of the ciliary body in the relaxed state and accommodated state. Modification in the ciliary body with accommodation was more evident for the younger subject ...

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    21. Modeling the effect of refraction on OCT imaging of lung tissue: a ray-tracing approach

      Modeling the effect of refraction on OCT imaging of lung tissue: a ray-tracing approach

      Determining the structure of lung tissue is difficult in ex-vivo samples. Optical coherence tomography (OCT) can image alveoli but ignores optical effects that distort the images. For example, light refracts and changes speed at the alveolar air-tissue surface. We employ ray-tracing to model OCT imaging with directional and speed changes included, using spherical shapes in 2D. Results show apparent thickening of inter-aveolar walls and distortion of shape and depth. Our approach suggests a correction algorithm by combining the model with image analysis. Distortion correction will allow inference of tissue mechanical properties and deeper imaging.

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    22. A hard-threshold based sparse inverse imaging algorithm for optical scanning holography reconstruction

      A hard-threshold based sparse inverse imaging algorithm for optical scanning holography reconstruction

      The optical imaging takes advantage of coherent optics and has promoted the development of visualization of biological application. Based on the temporal coherence, optical coherence tomography can deliver three-dimensional optical images with superior resolutions, but the axial and lateral scanning is a time-consuming process. Optical scanning holography (OSH) is a spatial coherence technique which integrates three-dimensional object into a two-dimensional hologram through a two-dimensional optical scanning raster. The advantages of high lateral resolution and fast image acquisition offer it a great potential application in three-dimensional optical imaging, but the prerequisite is the accurate and practical reconstruction algorithm. Conventional method was ...

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    23. Biomechanical properties of soft tissue measurement using optical coherence elastography

      Biomechanical properties of soft tissue measurement using optical coherence elastography

      Optical Coherence Tomography (OCT) provides images at near histological resolution, which allows for the identification of micron sized morphological tissue structures. Optical coherence elastography (OCE) measures tissue displacement and utilizes the high resolution of OCT to generate high-resolution stiffness maps. In this work, we explored the potential of measuring shear wave propagation using OCE. A swept-source OCT system was used in this study. The laser had a center wavelength of 1310 nm and a bandwidth of ~110 nm. The lateral resolution was approximately 13 μm in the samples. Acoustic radiation force was applied to two different phantoms using a 20 ...

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    24. Multimodal imaging of lung tissue using optical coherence tomography and two photon microscopy

      Multimodal imaging of lung tissue using optical coherence tomography and two photon microscopy

      In the context of protective artificial ventilation strategies for patients with severe lung diseases, the contribution of ventilator settings to tissue changes on the alveolar level of the lung is still a question under debate. To understand the impact of respiratory settings as well as the dynamic process of respiration, high-resolution monitoring and visualization of the dynamics of lung alveoli are essential. An instrument allowing 3D imaging of lung tissue as well as imaging of functional constituents, such as elastin fibers, in in situ experimental conditions is presented in this study using a combination of Fourier domain optical coherence tomography ...

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    1-24 of 295 1 2 3 4 ... 11 12 13 »
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