1. Articles from Deepa K. Kasaragod

    1-12 of 12
    1. Experimental validation of an extended Jones matrix calculus model to study the 3D structural orientation of the collagen fibers in articular cartilage using polarization-sensitive optical coherence tomography

      Experimental validation of an extended Jones matrix calculus model to study the 3D structural orientation of the collagen fibers in articular cartilage using polarization-sensitive optical coherence tomography

      We report results to verify a theoretical framework to analyze the 3D depth-wise structural organization of collagen fibers in articular cartilage using polarization-sensitive optical coherence tomography. Apparent birefringence data obtained from multi-angle measurements using a time domain polarization-sensitive optical coherence tomography system has been compared with simulated data based on the extended Jones matrix calculus. Experimental data has been shown to agree with the lamellar model previously proposed for the cartilage microstructure based on scanning electron microscopy data. This tool could have potential application in mapping the collagen structural orientation information of cartilage non-invasively during arthroscopy.

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    2. Polarization-sensitive optical coherence tomography using continuous polarization modulation with arbitrary phase modulation amplitude

      Polarization-sensitive optical coherence tomography using continuous polarization modulation with arbitrary phase modulation amplitude

      We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated ...

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    3. Optical coherence tomography based angle-resolved backscattering studies on bovine tendon and cartilage

      Optical coherence tomography based angle-resolved backscattering studies on bovine tendon and cartilage

      The difference in the genetic make up of the constituent molecules in collagen fibers in tendon and articular cartilage is what makes them mechanically and functionally different. A comparative study carried out on the differences in the angle-resolved back-scattering properties obtained from optical coherence tomography based studies on the two different types of scatterers: collagen I and collagen II fibers in bovine tendon and bovine articular cartilage sample, respectively, is reported here. Tendon sample shows greater anisotropy in the angle-resolved scattering profile compared to that obtained from articular cartilage sample. Rayleigh-Gans scattering approximation is used to provide the qualitative support ...

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    4. Polarization-sensitive optical coherence tomography measurements with different phase modulation amplitude when using continuous polarization modulation

      Polarization-sensitive optical coherence tomography measurements with different phase modulation amplitude when using continuous polarization modulation

      We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated ...

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    5. Comparative study of the angle-resolved backscattering properties of collagen fibers in bovine tendon and cartilage

      Comparative study of the angle-resolved backscattering properties of collagen fibers in bovine tendon and cartilage

      In a biological tissue, light scattering is based on the size and type of scatterers seen as refractive index variations that describe the optical properties shown. In this paper, we have implemented the variable incidence angle technique of multiple angle of illumination experiment on tendon and cartilage samples whose dominant constituents are genetically different types of collagen fibers, type I and type II, respectively. It is found that tendon displays a much greater angular anisotropy in its optical backscattering coefficient than the healthy cartilage. We propose that this is due to a more uniform distribution of fine fibrils than is ...

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    6. Method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

      Method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

      We present a phase fluctuation calibration method for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method uses a low-voltage broadband polarization modulator driven by a synchronized sinusoidal burst waveform rather than an asynchronous waveform, together with the removal of the global phases of the measured Jones matrices by the use of matrix normalization. This makes it possible to average the measured Jones matrices to remove the artifact due to the speckle noise of the signal in the sample without introducing auxiliary optical components into the sample arm. This method was validated on measurements of an equine ...

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    7. A method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

      A method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

      A phase fluctuation calibration method is presented for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method consists of the generation of a continuous triggered tone-burst waveform rather than an asynchronous waveform by use of a function generator and the removal of the global phases of the measured Jones matrices by use of matrix normalization. This could remove the use of auxiliary optical components for the phase fluctuation compensation in the system, which reduces the system complexity. Phase fluctuation calibration is necessary to obtain the reference Jones matrix by averaging the measured Jones matrices at sample surfaces ...

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    8. A theoretical framework for the analysis of optical anisotropy in birefringent biological tissues with polarization-sensitive optical coherence tomography

      A theoretical framework for the analysis of optical anisotropy in birefringent biological tissues with polarization-sensitive optical coherence tomography

      Polarization-sensitive optical coherence tomography (PSOCT) has established itself as an important non-invasive optical imaging tool to study the birefringent biological tissues. The complex 3D structure architecture of the collagen fibers in articular cartilage is investigated using a time domain PSOCT (TD-PSOCT) system and the depth-wise cumulative retardance profiles obtained are compared with a three layer cartilage model. The PSOCT result obtained from the variable incidence angle (VIA) experiment of bovine cartilage sample is found to be consistent with the proposed lamellar cartilage model based on scanning electron microscope studies. This shows potential use of PSOCT -VIA technique to obtain depth-wise ...

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    9. Performance comparison between 8- and 14-bit-depth imaging in polarization-sensitive swept-source optical coherence tomography

      Performance comparison between 8- and 14-bit-depth imaging in polarization-sensitive swept-source optical coherence tomography

      Recently the effects of reduced bit-depth acquisition on swept-source optical coherence tomography (SS-OCT) image quality have been evaluated by using simulations and empirical studies, showing that image acquisition at 8-bit depth allows high system sensitivity with only a minimal drop in the signal-to-noise ratio compared to higher bit-depth systems. However, in these studies the 8-bit data is actually 12- or 14-bit ADC data numerically truncated to 8 bits. In practice, a native 8-bit ADC could actually possess a true bit resolution lower than this due to the electronic jitter in the converter etc. We compare true 8- and 14-bit-depth imaging ...

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    10. Optic axis determination by fiber-based polarization-sensitive swept-source optical coherence tomography

      Optic axis determination by fiber-based polarization-sensitive swept-source optical coherence tomography

      We describe a fiber-based variable-incidence-angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3-D optical axis of birefringent biological tissues. Single-plane VIAPS- OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate ...

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    11. Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography

      Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography

      We describe a fibre-based variable-incidence angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3D optical axis of birefringent biological tissues. Single-plane VIA-PS-OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by the VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to ...

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    12. Speckle texture analysis of optical coherence tomography images

      Speckle texture analysis of optical coherence tomography images

      Optical coherence tomography (OCT) is an imaging technique based on the low coherence interferometry, in which signals are obtained based on the coherent addition of the back reflected light from the sample. Applying computational methods and automated algorithms towards the classification of OCT images allows a further step towards enhancing the clinical applications of OCT. One attempt towards classification could be achieved by statistically analyzing the texture of the noisy granular patterns - speckles that make the OCT images. An attempt has been made to quantify the scattering effects based on the speckle texture patterns the scatterers produce. Statistical inference is ...

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    1-12 of 12
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  2. Topics in the News

    1. (12 articles) University of Sheffield
    2. (12 articles) Steven J. Matcher
    3. (12 articles) Deepa K. Kasaragod
    4. (11 articles) Zenghai Lu
    5. (1 articles) University College London
    6. (1 articles) University of North Carolina
    7. (1 articles) Bern University Hospital
    8. (1 articles) Nieves Gonzalo
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    Speckle texture analysis of optical coherence tomography images Optic axis determination by fibre-based polarization-sensitive swept-source optical coherence tomography Performance comparison between 8- and 14-bit-depth imaging in polarization-sensitive swept-source optical coherence tomography Optic axis determination by fiber-based polarization-sensitive swept-source optical coherence tomography A theoretical framework for the analysis of optical anisotropy in birefringent biological tissues with polarization-sensitive optical coherence tomography A method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography Method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography Comparative study of the angle-resolved backscattering properties of collagen fibers in bovine tendon and cartilage Optical coherence tomography based angle-resolved backscattering studies on bovine tendon and cartilage Experimental validation of an extended Jones matrix calculus model to study the 3D structural orientation of the collagen fibers in articular cartilage using polarization-sensitive optical coherence tomography Influence of neoatherosclerosis on prognosis and treatment response in patients with in-stent restenosis Tracking the invasion of breast cancer cells in paper-based 3D cultures by OCT motility analysis