1. 1-24 of 252 1 2 3 4 ... 9 10 11 »
    1. Sensitivity enhancement for low coherence interferometry

      Sensitivity enhancement for low coherence interferometry

      In this letter, a sensitivity improvement for systems combining low coherence interferometry (LCI) and microwave photonics (MWP) is demonstrated. This improvement is due to the introduction of a different modulation format and an exhaustive control of the optical source profile compared to previous MWP-LCI schemes. Our proposal allows to retrieve the visibility of low-coherence interferograms through the analysis of the interference pattern using a dispersive element. We demonstrate that the use of a phase modulator offers better stability and lower insertion loss since a bias point configuration is not needed compared to the intensity modulators typically used in these schemes ...

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    2. Automatic Identification of Weave Patterns of Checked and Colored Fabrics Using Optical Coherence Tomography

      Automatic Identification of Weave Patterns of Checked and Colored Fabrics Using Optical Coherence Tomography

      Identifying the weave pattern of fabrics can be done manually or automatically. Carrying out the weave recognition automatically will reduce the procedure time and error rates since automatic systems can perform successive measurements at high speeds and with great repeatability and quality. Woven fabric repeat identification systems that are automatic, usually work by employing complex algorithms and techniques. It is known that these automatic techniques struggle when trying to identify highly complex patterns, composing of a combination of different structures, figures, and colors. For example, image processing algorithms are known to make errors when dealing with checked and colored fabrics ...

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    3. Predicting Macular Edema Recurrence from Spatio-Temporal Signatures in Optical Coherence Tomography Images

      Predicting Macular Edema Recurrence from Spatio-Temporal Signatures in Optical Coherence Tomography Images

      Prediction of treatment responses from available data is key to optimizing personalized treatment. Retinal diseases are treated over long periods and patients’ response patterns differ substantially, ranging from a complete response to a recurrence of the disease and need for re-treatment at different intervals. Linking observable variables in high-dimensional observations to outcome is challenging. In this paper, we present and evaluate two different data-driven machine learning approaches operating in a high-dimensional feature space: sparse logistic regression and random forests-based extra trees (ET). Both identify spatio-temporal signatures based on retinal thickness features measured in longitudinal spectral-domain optical coherence tomography (OCT) imaging ...

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    4. Segmentation and Quantification for Angle-Closure Glaucoma Assessment in Anterior Segment OCT

      Segmentation and Quantification for Angle-Closure Glaucoma Assessment in Anterior Segment OCT

      Angle-closure glaucoma is a major cause of irreversible visual impairment and can be identified by measuring the anterior chamber angle (ACA) of the eye. The ACA can be viewed clearly through anterior segment optical coherence tomography (AS-OCT), but the imaging characteristics and the shapes and locations of major ocular structures can vary significantly among different AS-OCT modalities, thus complicating image analysis. To address this problem, we propose a data-driven approach for automatic AS-OCT structure segmentation, measurement, and screening. Our technique first estimates initial markers in the eye through label transfer from a hand-labeled exemplar data set, whose images are collected ...

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    5. Optimization of the Source Power Usage in Spectral Domain Optical Coherence Tomography

      Optimization of the Source Power Usage in Spectral Domain  Optical Coherence Tomography

      Source power consumption and system sensitivity of a spectrometer based optical coherence tomography (SD-OCT) system are investigated. Our study shows that the performance of SD-OCT system can be classified into two categories based on the beam splitting ratio R between the sample and reference rams in the Michelson interferometer. For the classic SD-OCT configuration, R is less than 1.0, and improvement of sample light collection efficiency through reducing R will increase the cost of OCT source power. We find that through combining the detection and source arms of a Michelson interferometer together with a fiber optic circulator and choosing ...

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    6. Size-Dependent Multiple-Scattering Effects of Mesoporous TiO2 Beads Distinguished by Optical Coherence Tomography

      Size-Dependent Multiple-Scattering Effects of Mesoporous TiO2 Beads Distinguished by Optical Coherence Tomography

      In this study, we propose a new analysis method using optical coherence tomography to further use the diffusive reflectance measurement to quantify the contribution of the size dependent multiple scattering effects of mesoporous TiO2 beads. The diffusive reflectance results from the complex interactions between light and the scattering particles, and influences the slopes of the associated depth dependent A-scan profiles, which can be fitted based on the extended Huygens-Fresnel model to quantify the contribution ratio of the multiple-scattering effects to the single scattering effects. The mesoporous TiO2 beads with average diameter of 300 nm show higher contribution percentage of multiple ...

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    7. Fully-Automated Segmentation of Fluid/Cyst Regions in Optical Coherence Tomography Images with Diabetic Macular Edema using Neutrosophic Sets and Graph Algorithm

      Fully-Automated Segmentation of Fluid/Cyst Regions in Optical Coherence Tomography Images with Diabetic Macular Edema using Neutrosophic Sets and Graph Algorithm

      This paper presents a fully-automated algorithm to segment fluid-associated (fluid-filled) and cyst regions in optical coherence tomography (OCT) retina images of the subjects with diabetic macular edema (DME). 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 ...

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    8. High Resolution Optical Frequency Domain Reflectometry for Analyzing Intra-Chip Reflections

      High Resolution Optical Frequency Domain Reflectometry for Analyzing Intra-Chip Reflections

      We present a method for high-resolution optical frequency domain reflectometry by de-embedding group-velocity dispersion in the device under test. The method is shown to provide an accurate estimation of the wavelength-dependent group refractive index, and provides a spatial resolution of 5.3 ± 1.7µm for intra-chip reflections. We applied this method to characterize localized reflections from a number of waveguide crossings. The minimum distance of 30µm between two crossings could easily be resolved. The reflection of waveguide crossings was analyzed to be (2.5 ± 1.2) · 10−6.

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    9. Monitoring skin trauma healing in mice using second-harmonic generation combined with optical coherence tomography

      Monitoring skin trauma healing in mice using second-harmonic generation combined with optical coherence tomography

      Convenient methods for rapidly evaluating wound healing could help clinicians to select effective treatment measures for patients within an appropriate time frame. In this study, we explored the use of second-harmonic generation (SHG) combined with optical coherence tomography (OCT) to monitor the healing state of wounds, including the macromorphology and optical signal characteristics of regenerated tissue. Wounds were imaged and monitored using OCT and SHG on healing days 3, 5, 7, 14, 21 and 28. The accumulation and maturation of newly formed collagen during the healing process was detected using SHG in real time. Additionally, changes in the OCT signal ...

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    10. Automatic identification of side branch and main vascular measurements in intravascular optical coherence tomography images

      Automatic identification of side branch and main vascular measurements in intravascular optical coherence tomography images

      Automatic identification of side branch and main vascular measurements in IVOCT images take critical roles in pre-interventional decision making for coronary artery disease treatment. Very little works have been presented on these tasks. In this paper, we proposed a novel side branch identification algorithm which utilizes a newly defined global curvature feature to identify the ostium of side branch. Based on identification results, the main vascular can be segmented automatically for measurements. In the measurement of main vascular, the diameter of maximum inscribed circle of main vascular is proposed for the first time, which could be helpful in stent size ...

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    11. High Throughput Photonic Time Stretch Optical Coherence Tomography with Data Compression

      High Throughput Photonic Time Stretch Optical Coherence Tomography with Data Compression

      Photonic time stretch enables real time high throughput optical coherence tomography (OCT), but with massive data volume being a real challenge. In this paper, data compression in high throughput optical time stretch OCT has been explored and experimentally demonstrated. This is made possible by exploiting spectral sparsity of encoded optical pulse spectrum based on compressive sensing (CS) approach. Both randomization and integration have been implemented in the optical domain avoiding electronic bottleneck. Data compression ratio of 66% has been achieved in high throughput OCT measurements with 1.51 MHz axial scan rate using greatly reduced data sampling rate of 50 ...

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    12. Automatic Identification of Pathology-Distorted Retinal Layer Boundaries Using SD-OCT Imaging

      Automatic Identification of Pathology-Distorted Retinal Layer Boundaries Using SD-OCT Imaging

      Objective: We propose an effective automatic method for identification of four retinal layer boundaries from the spectral domain optical coherence tomography images in the presence and absence of pathologies and morphological changes due to disease. Methods: The approach first finds an approximate location of three reference layers and then uses these to bound the search space for the actual layers, which is achieved by modeling the problem as a graph and applying Dijkstra's shortest path algorithm. The edge weight between nodes is determined using pixel distance, slope similarity to a reference, and nonassociativity of the layers, which is designed ...

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    13. Joint Segmentation of Retinal Layers and Focal Lesions in 3-D OCT Data of Topologically Disrupted Retinas

      Joint Segmentation of Retinal Layers and Focal Lesions in 3-D OCT Data of Topologically Disrupted Retinas

      Accurate quantification of retinal structures in 3-D optical coherence tomography data of eyes with pathologies provides clinically relevant information. We present an approach to jointly segment retinal layers and lesions in eyes with topology-disrupting retinal diseases by a loosely coupled level set framework. In the new approach, lesions are modeled as an additional space-variant layer delineated by auxiliary interfaces. Furthermore, the segmentation of interfaces is steered by local differences in the signal between adjacent retinal layers, thereby allowing the approach to handle local intensity variations. The accuracy of the proposed method of both layer and lesion segmentation has been evaluated ...

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    14. Multi-Modality Imaging Enables Detailed Hemodynamic Simulations in Dissecting Aneurysms in Mice

      Multi-Modality Imaging Enables Detailed Hemodynamic Simulations in Dissecting Aneurysms in Mice

      A multi-modality imaging-based modeling approach was used to study complex unsteady hemodynamics and lesion growth in a dissecting abdominal aortic aneurysm model. We combined in vivo ultrasound (geometry and flow) and in vitro optical coherence tomography (OCT) (geometry) to obtain the high resolution needed to construct detailed hemodynamic simulations over large portions of the murine vasculature, which include fine geometric complexities. We illustrate this approach for a spectrum of dissecting abdominal aortic aneurysms induced in male apolipoprotein E-null mice by high-dose angiotensin II infusion. In vivo morphological and hemodynamic data provide information on volumetric lesion growth and changes in blood ...

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    15. Predicting Macular Edema Recurrence from Spatio-Temporal Signatures in Optical Coherence Tomography Image

      Predicting Macular Edema Recurrence from Spatio-Temporal Signatures in Optical Coherence Tomography Image

      Abstract: Prediction of treatment responses from available data is key to optimizing personalized treatment. Retinal diseases are treated over long periods and patients’ response patterns differ substantially, ranging from a complete response to a recurrence of the disease and need for re-treatment at different intervals. Linking observable variables in high-dimensional observations to outcome is challenging. In this paper, we present and evaluate two different data-driven machine learning approaches operating in a high-dimensional feature space: sparse logistic regression and Random Forests based extra trees (ET). Both identify spatio-temporal signatures based on retinal thickness features measured in longitudinal spectral-domain optical coherence tomography ...

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    16. An All-fiber Supercontinuum Source with 30.6 W High Power and Ultra-wide Spectrum Ranging from 385 nm to Beyond 2400 nm

      An All-fiber Supercontinuum Source with 30.6 W High Power and Ultra-wide Spectrum Ranging from 385 nm to Beyond 2400 nm

      An all-fiber high power, blue-enhanced supercontinuum generation in a piece of uniform photonic crystal fiber pumped by a picosecond Yb-doped master oscillator power amplifier (MOPA) is experimentally demonstrated. The MOPA source is seeded by an actively dissipative soliton (DS) mode-locked Yb-doped fiber laser with a fundamental repetition rate of ~15.33 MHz and a large chirp. By introducing giant chirp to the seed pulses and optimizing the pump power in every stage of the MOPA, a SC with 30.6 W output average power and an extremely wide spectrum of 385 nm to beyond 2400 nm is obtained.

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    17. A Feasibility Study of Broadband White Light Emitting Diode (WLED) based Full-Field Optical Coherence Microscopy (FF-OCM) using Derivative-based Algorithm

      A Feasibility Study of Broadband White Light Emitting Diode (WLED) based Full-Field Optical Coherence Microscopy (FF-OCM) using Derivative-based Algorithm

      Developing cost-effective and fast detection methods in full-field optical coherence microscopy (FF-OCM) platform for biological applications is of prime focus today. In this paper, we report a cost-effective Linnik type FF-OCM system with a single broadband white light emitting diode (WLED) (470-850nm, λ0=630nm) light source in conjunction with a derivative-based image reconstruction algorithm. Sequential two-dimensional (2D) multiple phase-shifted interferograms were obtained by moving the sample stage using piezoelectric transducer (PZT) and recorded via a 2D charge complementary oxide semiconductor (CMOS) camera. Subsequently, the en-face sectional images were reconstructed using a derivative-based algorithm. The measured axial and lateral resolutions along ...

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    18. Smoothing Splines on Unit Ball Domains with Application to Corneal Topography

      Smoothing Splines on Unit Ball Domains with Application to Corneal Topography

      Abstract: Optical coherence tomography (OCT) is a non-invasive imaging technique used to study and understand internal structures of biological tissues such as the anterior chamber of the human eye. An interesting problem is the reconstruction of the shape of the biological tissue from OCT images, that is not only a good fit of the data but also respects the smoothness properties observed in the images. A similar problem arises in Magnetic Resonance Imaging (MRI). We cast the problem as a penalized weighted least squares regression with a penalty on the magnitude of the second derivative (Laplacian) of the surface. We ...

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    19. Efficient OCT volume reconstruction from slitlamp microscopes

      Efficient OCT volume reconstruction from slitlamp microscopes

      Since its introduction 25 years ago, Optical Coherence Tomography (OCT) has contributed tremendously to diagnostic and monitoring capabilities of pathologies in the field of ophthalmology. Despite rapid progress in hardware and software technology however, the price of OCT devices has remained high, limiting their use in private practice and in screening examinations. In this paper, we present a slitlamp-integrated OCT device, built with off-the-shelf components, which can generate high-quality volumetric images of the posterior eye segment. To do so, we present a novel strategy for 3D image reconstruction in this challenging domain that allows for state-ofthe- art OCT volumes to ...

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    20. Contrast Enhanced Subsurface Fingerprint Detection using High-speed Optical Coherence Tomography

      Contrast Enhanced Subsurface Fingerprint Detection using High-speed Optical Coherence Tomography

      Spectral-domain optical coherence tomography (SDOCT) has been demonstrated to be a viable tool in forensic science for fingerprint detection, yet it still suffers from certain practical issues, e.g., the limited scanning speed and low image contrast. In this letter, we report a high-speed SD-OCT together with an image contrast enhancement mechanism for reliable subsurface fingerprint detection. The constructed SDOCT system achieves a scanning rate up to 60K A-lines/s, and thus, both 3D volumetric images, reaching up to 20mm × 20mm × 1.2mm, and en face internal fingerprint furrow pattern images could be obtained. Based upon the analyses of the ...

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    21. Optical Coherence Tomography for Brain Imaging and Developmental Biology

      Optical Coherence Tomography for Brain Imaging and Developmental Biology

      Optical coherence tomography (OCT) is a promising research tool for brain imaging and developmental biology. Serving as a three-dimensional optical biopsy technique, OCT provides volumetric reconstruction of brain tissues and embryonic structures with micrometer resolution and video rate imaging speed. Functional OCT enables label-free monitoring of hemodynamic and metabolic changes in the brain in vitro and in vivo in animal models. Due to its noninvasiveness nature, OCT enables longitudinal imaging of developing specimens in vivo without potential damage from surgical operation, tissue fixation and processing, and staining with exogenous contrast agents. In this paper, various OCT applications in brain imaging ...

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    22. Performance analysis of a Hybrid fingerprint extracted from optical coherence tomography fingertip scans

      Performance analysis of a Hybrid fingerprint extracted from optical coherence tomography fingertip scans

      The Hybrid fingerprint is a local-quality-specific blend of the surface and internal fingerprints, extracted from optical coherence tomography scans. Owing to its origin, and the manner in which it is obtained, the Hybrid fingerprint is a high-quality and secure fingerprint acquisition solution. This research entails a detailed description of the Hybrid fingerprint, the techniques involved to produce it, and a performance analysis of it. A dataset of 282 fingertip scans was established. Two recognised minutiae extraction and fingerprint matching algorithms were applied to assess the performance of the Hybrid fingerprint. The best equal error rate measured was 1.25%. NIST ...

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      Mentions: Ann Singh
    23. Miniaturization of plastic lens by injection molding for disposable endoscopie optical coherence tomography system

      Miniaturization of plastic lens by injection molding for disposable endoscopie optical coherence tomography system

      Minimally invasive robotic surgery required disposable endoscopie optical coherence tomography (OCT) for high-resolution deep tissue imaging and cross-contamination prevention. Here, we developed a miniaturized plastic lens by injection molding for developing a disposable endoscopie optical coherence tomography system for the first time. Injection molding provided low-cost and high-production rate to produce a disposable plastic lens and enabled the miniaturization of plastic lens. Transmittance and curvature of the plastic lens was measured. The plastic lens was integrated with an endoscopie OCT system, and the images of human-skin and microspheres embedded in agarose gel were captured. We are currently trying to integrate ...

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      Mentions: Ki Hean Kim
    24. Imaging Spinal Structures With Polarization-Sensitive Optical Coherence Tomography

      Imaging Spinal Structures With Polarization-Sensitive Optical Coherence Tomography

      Impact Statement: We investigate polarization-sensitive optical coherence tomography (PS-OCT) to obtain both intensity and polarization contrast images of in vivo and ex vivo spinal structures like subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, dura, and spinal cord in a piglet model. The PS-OCT can provide enhanced contrast characteristic structures compared to the intensity OCT; therefore it has the potential for guidance in spine interventional procedures. Abstract: We investigate polarization-sensitive optical coherence tomography (PS-OCT) to obtain both intensity and polarization contrast images of in vivo and ex vivo spinal structures like subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, dura ...

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    1-24 of 252 1 2 3 4 ... 9 10 11 »
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