1. Articles from Deepa Kasaragod

    1-20 of 20
    1. Machine-learning based segmentation of the optic nerve head using multi-contrast Jones matrix optical coherence tomography with semi-automatic training dataset generation

      Machine-learning based segmentation of the optic nerve head using multi-contrast Jones matrix optical coherence tomography with semi-automatic training dataset generation

      A pixel-by-pixel tissue classification framework using multiple contrasts obtained by Jones matrix optical coherence tomography (JM-OCT) is demonstrated. The JM-OCT is an extension of OCT that provides OCT, OCT angiography, birefringence tomography, degree-of-polarization uniformity tomography, and attenuation coefficient tomography, simultaneously. The classification framework consists of feature engineering, k -means clustering that generates a training dataset, training of a tissue classifier using the generated training dataset, and tissue classification by the trained classifier. The feature engineering process generates synthetic features from the primary optical contrasts obtained by JM-OCT. The tissue classification is performed in the feature space of the engineered features ...

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    2. Comparison of intensity, phase retardation, and local birefringence images for filtering blebs using polarization-sensitive optical coherence tomography

      Comparison of intensity, phase retardation, and local birefringence images for filtering blebs using polarization-sensitive optical coherence tomography

      Polarization-sensitive optical coherence tomography (PS-OCT) allows the recording of depth-resolved polarimetric measurements. It has been reported that phase retardation and local birefringence images can noninvasively detect fibrotic area in blebs after glaucoma surgery. Evaluation of scar fibrosis in blebs is important not only for predicting bleb function, but also for planning revision trabeculectomy. Herein, we characterize the intensity, phase retardation, and local birefringence images of blebs using PS-OCT. A total of 85 blebs from 85 patients who had undergone trabeculectomy were examined. Both phase retardation and local birefringence images detected fibrotic changes in blebs after glaucoma surgery. Phase retardation images ...

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    3. Simultaneous tissue birefringence and deformation measurement by polarization sensitive optical coherence elastography with active compression

      Simultaneous tissue birefringence and deformation measurement by polarization sensitive optical coherence elastography with active compression

      Polarization sensitive optical coherence tomography (PS-OCT) measures tissue birefringence, while optical coherence elastography (OCE) reveals the mechanical property of the tissue. Since both birefringence and mechanical properties are associated with tissue microstructures such as collagen, simultaneous PS-OCT and OCE measurement will provide useful insight for the tissue microstructures. In this paper, we present a combined PS-OCT and OCE technique. The PS-OCT is based on Jones matrix OCT theory. It measures a tomography of Jones matrix. Birefringence tomography is then deduced from the Jones matrix. The OCE is obtained with active tissue compression. The tissue compression was performed by a ring ...

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    4. Generation and optimization of superpixels as image processing kernels for Jones matrix optical coherence tomography

      Generation and optimization of superpixels as image processing kernels for Jones matrix optical coherence tomography

      Jones matrix-based polarization sensitive optical coherence tomography (JM-OCT) simultaneously measures optical intensity, birefringence, degree of polarization uniformity, and OCT angiography. The statistics of the optical features in a local region, such as the local mean of the OCT intensity, are frequently used for image processing and the quantitative analysis of JM-OCT. Conventionally, local statistics have been computed with fixed-size rectangular kernels. However, this results in a trade-off between image sharpness and statistical accuracy. We introduce a superpixel method to JM-OCT for generating the flexible kernels of local statistics. A superpixel is a cluster of image pixels that is formed by ...

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    5. Birefringence and vascular imaging of in vivo human skin by Jones-matrix optical coherence tomography

      Birefringence and vascular imaging of in vivo human skin by Jones-matrix optical coherence tomography

      A customized 1310-nm Jones-matrix optical coherence tomography (JM-OCT) for dermatological investigation was constructed and used for in vivo normal human skin tissue imaging. This system can simultaneously measure the threedimensional depth-resolved local birefringence, complex-correlation based OCT angiography (OCT-A), degree-ofpolarization- uniformity (DOPU) and scattering OCT intensity. By obtaining these optical properties of tissue, the morphology, vasculature, and collagen content of skin can be deduced and visualized. Structures in the deep layers of the epithelium were observed with depth-resolved local birefringence and polarization uniformity images. These results suggest high diagnostic and investigative potential of JM-OCT for dermatology.

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    6. Three-dimensional multi-contrast imaging of in vivo human skin by Jones matrix optical coherence tomography

      Three-dimensional multi-contrast imaging of in vivo human skin by Jones matrix optical coherence tomography

      A custom made dermatological Jones matrix optical coherence tomography (JM-OCT) is presented. It uses a passive-polarization-delay component based swept-source JM-OCT configuration, but is specially designed for in vivo human skin measurement. The center wavelength of its probe beam is 1310 nm and the A-line rate is 49.6 kHz. The JM-OCT is capable of simultaneously providing birefringence (local retardation) tomography, degree-of-polarization-uniformity tomography, complex-correlation-based optical coherence angiography, and conventional scattering OCT. To evaluate the performance of this JM-OCT, we measured in vivo human skin at several locations. Using the four kinds of OCT contrasts, the morphological characteristics and optical properties of ...

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    7. Noise stochastic corrected maximum a posteriori estimator for birefringence imaging using polarization-sensitive optical coherence tomography

      Noise stochastic corrected maximum a posteriori estimator for birefringence imaging using polarization-sensitive optical coherence tomography

      This paper presents a noise-stochastic corrected maximum a posteriori estimator for birefringence imaging using Jones matrix optical coherence tomography. The estimator described in this paper is based on the relationship between probability distribution functions of the measured birefringence and the effective signal to noise ratio (ESNR) as well as the true birefringence and the true ESNR. The Monte Carlo method is used to numerically describe this relationship and adaptive 2D kernel density estimation provides the likelihood for a posteriori estimation of the true birefringence. Improved estimation is shown for the new estimator with stochastic model of ESNR in comparison to ...

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    8. Quantitative Evaluation of Phase Retardation in Filtering Blebs Using Polarization-Sensitive Optical Coherence Tomography

      Quantitative Evaluation of Phase Retardation in Filtering Blebs Using Polarization-Sensitive Optical Coherence Tomography

      Purpose : Polarization-sensitive optical coherence tomography (PS-OCT) can detect and evaluate scar fibrosis of the filtering blebs after glaucoma surgery. Although the change in phase retardation reportedly reflects bleb function, quantitative assessment of phase retardation in ocular tissues has not been conducted. We aimed to establish quantitative methods to investigate changes in phase retardation in the blebs after surgery using PS-OCT. Methods : Twenty-two blebs of 22 patients who had undergone glaucoma filtration surgery were consecutively examined for 4 months. Phase retardation was measured by PS-OCT and quantitatively analyzed to evaluate its relationship with bleb function based on intraocular pressure and medication ...

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    9. Objective Evaluation of Functionality of Filtering Bleb Based on Polarization-Sensitive Optical Coherence Tomography

      Objective Evaluation of Functionality of Filtering Bleb Based on Polarization-Sensitive Optical Coherence Tomography

      Purpose : The fibrosis score is a new diagnostic score that we have developed to evaluate the function of bleb structures after glaucoma filtration surgery using polarization-sensitive optical coherence tomography (PS-OCT). This study aims to assess the efficacy of the fibrosis score in discriminating nonfunctional from the functional blebs. Methods : A total of 20 patients who had undergone glaucoma filtration surgery were imaged at different time periods after surgery using PS-OCT. Birefringence tomography of blebs was obtained from PS-OCT, and the fibrosis score was computed for each patient. The fibrosis score is defined as the area of occupation of high birefringence ...

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    10. Three-dimensional multifunctional optical coherence tomography for skin imaging

      Three-dimensional multifunctional optical coherence tomography for skin imaging

      Optical coherence tomography (OCT) visualizes cross-sectional microstructures of biological tissues. Recent developments of multifunctional OCT (MF-OCT) provides multiple optical contrasts which can reveal currently unknown tissue properties. In this contribution we demonstrate multifunctional OCT specially designed for dermatological investigation. And by utilizing it to measure four different body parts of in vivo human skin, three-dimensional scattering OCT, OCT angiography, polarization uniformity tomography, and local birefringence tomography images were obtained by a single scan. They respectively contrast the structure and morphology, vasculature, melanin content and collagen traits of the tissue.

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    11. Birefringence imaging of posterior eye by multi-functional Jones matrix optical coherence tomography

      Birefringence imaging of posterior eye by multi-functional Jones matrix optical coherence tomography

      A clinical grade prototype of posterior multifunctional Jones matrix optical coherence tomography (JM-OCT) is presented. This JM-OCT visualized depth-localized birefringence in addition to conventional cumulative phase retardation imaging through local Jones matrix analysis. In addition, it simultaneously provides a sensitivity enhanced scattering OCT, a quantitative polarization uniformity contrast, and OCT-based angiography. The probe beam is at 1- μ m wavelength band. The measurement speed and the depth-resolution were 100,000 A-lines/s, and 6.6 μ m in tissue, respectively. Normal and pathologic eyes are examined and several clinical features are revealed, which includes high birefringence in the choroid and lamina cribrosa ...

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    12. Repeatability of Corneal Phase Retardation Measurements by Polarization-Sensitive Optical Coherence Tomography

      Repeatability of Corneal Phase Retardation Measurements by Polarization-Sensitive Optical Coherence Tomography

      Purpose. Polarization-sensitive optical coherence tomography (PS-OCT) can evaluate internal tissue structures of the cornea, such as collagen fibers, by phase retardation measurement. In this study, we assessed the repeatability of corneal phase retardation measurements using anterior segment PS-OCT. Methods. A total of 173 eyes of 173 patients were measured using PS-OCT. In total, 58 eyes of young subjects with normal corneas, 28 eyes of old subjects with normal corneas, 26 eyes with corneal dystrophy or degeneration, 37 eyes with corneal transplantation, and 24 eyes with keratoconus were evaluated. The 3-mm diameter average of en face phase retardation of the posterior ...

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    13. Noninvasive Evaluation of Phase Retardation in Blebs after Glaucoma Surgery Using Anterior Segment Polarization-Sensitive Optical Coherence Tomography

      Noninvasive Evaluation of Phase Retardation in Blebs after Glaucoma Surgery Using Anterior Segment Polarization-Sensitive Optical Coherence Tomography

      Purpose: Evaluation of bleb morphology using anterior segment optical coherence tomography (OCT) can offer important information regarding bleb function after glaucoma surgery. However, analysis of tissue properties, such as scar fibrosis of blebs, is difficult with conventional OCT. The birefringence of the blebs as susceptible measure of fibrosis scar was evaluated using polarization-sensitive OCT (PS-OCT) and its relation with bleb function was assessed. Methods: One hundred and fifty-three blebs of 122 patients that had undergone trabeculectomy or an Ex-Press tube shunt were examined. Also, in 14 blebs of 12 patients, consecutive measurements were performed for 2 months after surgery. The ...

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    14. Bayesian maximum likelihood estimator of phase retardation for quantitative polarization-sensitive optical coherence tomography

      Bayesian maximum likelihood estimator of phase retardation for quantitative polarization-sensitive optical coherence tomography

      This paper presents the theory and numerical implementation of a maximum likelihood estimator for local phase retardation (i.e., birefringence) measured using Jones-matrix-based polarization sensitive optical coherence tomography. Previous studies have shown conventional mean estimations of phase retardation and birefringence are significantly biased in the presence of system noise. Our estimator design is based on a Bayes’ rule that relates the distributions of the measured birefringence under a particular true birefringence and the true birefringence under a particular measured birefringence. We used a Monte-Carlo method to calculate the likelihood function that describes the relationship between the distributions and numerically implement ...

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    15. Feature Of The Week 4/20/14: Conical-Scan Polarization-Sensitive Optical Coherence Tomography (CS-PS-OCT)

      Feature Of The Week 4/20/14: Conical-Scan Polarization-Sensitive Optical Coherence Tomography (CS-PS-OCT)

      We report on a new articular cartilage imaging technique with potential for clinical arthroscopic use, by supplementing the variable-incidence-angle polarization-sensitive optical coherence tomography method (VIA-PS-OCT) previously developed by us with a conical beam scan protocol. In the protocol, the beam is scanned such that the k-vector sweeps out a conical surface whose apex is chosen, for convenience, to lie at the tissue surface. In the implementation reported here we achieve this by mounting the sample on a motorized rotation stage with the sample surface roughly parallel to the stage rotating plane (i.e. normal to the stage rotation axis). The ...

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    16. Conical scan polarization-sensitive optical coherence tomography

      Conical scan polarization-sensitive optical coherence tomography

      We report on a new articular cartilage imaging technique with potential for clinical arthroscopic use, by supplementing the variable-incidence-angle polarization-sensitive optical coherence tomography method previously developed by us with a conical beam scan protocol. The technique is validated on bovine tendon by comparing experimental data with simulated data generated using the extended Jones matrix calculus. A unique capability of this new optical technique is that it can locate the “brushing direction” of collagen fibers in articular cartilage, which is structural information that extends beyond established methods such as split-line photography or birefringent fast-axis measurement in that it is uniquely defined ...

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    17. Photothermal detection of the contrast properties of polypyrrole nanoparticles using optical coherence tomography

      Photothermal detection of the contrast properties of polypyrrole nanoparticles using optical coherence tomography

      We report on a photothermal modulation detection scheme developed using a swept source-based optical coherence tomography (OCT) system centred at 1300nm. Photothermal detection is an improved technique for studying the contrast properties of exogenous contrast agents such as highly absorbing polypyrrole (PPy) nanoparticles used for OCT imaging. The swept source based OCT system has a wavelength sweep rate of 10 kHz which is used for the phase modulation detection of various concentrations of PPy nanoparticles. PPy nanoparticles have been recently reported to be a promising candidate for OCT imaging owing to their strong NIR absorption from 700–1300nm. Phase-sensitive detection ...

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    18. Optical measurement of the structure of articular cartilage

      Optical measurement of the structure of articular cartilage

      A new optical technique can non-invasively determine the collagen structure in articular cartilage and could lead to improved understanding of arthritis. Medical conditions such as osteoarthritis are painful, debilitating, and hard to treat because they involve degradation of tissues that have a poor natural repair capacity, such as articular cartilage (which coats the sliding surfaces of articulating joints such as the knee). Cartilage is a material with remarkable mechanical properties that has evolved to tolerate the large shear and compressive stresses that are generated during everyday activities such as standing up and walking. Its mechanical properties arise from the interplay ...

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    19. Feature Of The Week 5/6/12: University of Sheffield investigates models to study the 3D structural orientation of the collagen fibers in articular cartilage using PS-OCT

      Feature Of The Week 5/6/12: University of Sheffield investigates models to study the 3D structural orientation of the collagen fibers in articular cartilage using PS-OCT

      Researchers from the University of Sheffield recently showed the applicability of an extended Jones matrix calculus approach to understand the 3D orientation information of collagen fiber in articular cartilage using multi-angle polarization sensitive optical coherence tomography OCT imaging.  The work could potentially advance the use of OCT imaging in orthopaedics and improve our understanding of the biomechanics and pathological changes occurring in articular cartilage during osteoarthritis.For more information see recent Article. Courtesy Deepa Kasaragod from the University of Sheffield.

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    20. Evaluation of a swept-laser optical coherence tomography light source based on a novel quantum-dot based semiconductor optical amplifier

      Evaluation of a swept-laser optical coherence tomography light source based on a novel quantum-dot based semiconductor optical amplifier

      We describe a simple swept-laser design that characterizes the emission bandwidth, linewidth, spectral shape and output noise. A short cavity Littmann configuration is used in which the semiconductor optical amplifier (SOA) lasing wavelength is tuned by a galvanometer with an 830 grooves per mm diffraction grating. A 3dB coupler extracts light from the cavity formed by the grating and end-mirror and the optical output uses to illuminate a balanced swept source optical coherence tomography (SS-OCT) interferometer incorporating a circulator, 3dB coupler, dispersion compensator and balanced detector. The SOA (SOA-1200-70-PM-20sB, Innolume GmbH) uses a novel III-V semiconductor quantum-dot gain medium. ASE ...

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    1-20 of 20
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    1. (20 articles) Deepa K. Kasaragod
    2. (16 articles) University of Tsukuba
    3. (14 articles) Yoshiaki Yasuno
    4. (9 articles) Shuichi Makita
    5. (6 articles) University of Sheffield
    6. (6 articles) Steven J. Matcher
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    Evaluation of a swept-laser optical coherence tomography light source based on a novel quantum-dot based semiconductor optical amplifier Feature Of The Week 5/6/12: University of Sheffield investigates models to study the 3D structural orientation of the collagen fibers in articular cartilage using PS-OCT Optical measurement of the structure of articular cartilage Photothermal detection of the contrast properties of polypyrrole nanoparticles using optical coherence tomography Conical scan polarization-sensitive optical coherence tomography Feature Of The Week 4/20/14: Conical-Scan Polarization-Sensitive Optical Coherence Tomography (CS-PS-OCT) Bayesian maximum likelihood estimator of phase retardation for quantitative polarization-sensitive optical coherence tomography Noninvasive Evaluation of Phase Retardation in Blebs after Glaucoma Surgery Using Anterior Segment Polarization-Sensitive Optical Coherence Tomography Repeatability of Corneal Phase Retardation Measurements by Polarization-Sensitive Optical Coherence Tomography Birefringence imaging of posterior eye by multi-functional Jones matrix optical coherence tomography AI-Assisted In Situ Detection of Human Glioma Infiltration Using a Novel Computational Method for Optical Coherence Tomography Motorized capsule for shadow-free OCT imaging and synchronous beam control