1. Articles from Valentin M. Gelikonov

    1-21 of 21
    1. Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability

      Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability

      Recently proposed in vivo label-free optical coherence angiography techniques based on phase and amplitude speckle variability often require additional signal pre- and post processing operations to enhance vessel-contrast. We observe here 1) contrast enhancement by optimizing the signal normalization/weighing before processing; 2) algorithm based on Kasai estimator for phase compensation between processed A-scans to reduce masking role of motion artifacts; and 3) image projection through the imaging depth for en face plotting. We demonstrate the efficiency of proposed additional algorithms as for the microcirculation imaging of hamsters cheek in vivo as for the preliminary microcirculation imaging of patients after ...

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    2. Multi-modal optical imaging characterization of atherosclerotic plaques

      Multi-modal optical imaging characterization of atherosclerotic plaques

      We combined cross-polarization optical coherence tomography (CP OCT) and non-linear microscopy based on second harmonic generation (SHG) and two-photon-excited fluorescence (2PEF) to assess collagen and elastin fibers and other vascular structures in the development of atherosclerosis, including identification of vulnerable plaques, which remains an important clinical problem and imaging application. CP OCT's ability to visualize tissue birefringence and cross-scattering adds new information about the microstructure and composition of the plaque. However its interpretation can be ambiguous, because backscattering contrast may have a similar appearance to the birefringence related fringes. Our results represent a step towards minimally invasive characterization and ...

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    3. Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography

      Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography

      Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle “blinking” and ...

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    4. Scan-pattern and signal processing for microvasculature visualization with complex SD-OCT: tissue-motion artifacts robustness and decorrelation time - blood vessel characteristics

      Scan-pattern and signal processing for microvasculature visualization with complex SD-OCT: tissue-motion artifacts robustness and decorrelation time - blood vessel characteristics

      We propose a modification of OCT scanning pattern and corresponding signal processing for 3D visualizing blood microcirculation from complex-signal B-scans. We describe the scanning pattern modifications that increase the methods’ robustness to bulk tissue motion artifacts, with speed up to several cm/s. Based on these modifications, OCT-based angiography becomes more realistic under practical measurement conditions. For these scan patterns, we apply novel signal processing to separate the blood vessels with different decorrelation times, by varying of effective temporal diversity of processed signals. 

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    5. Hybrid M-mode-like OCT imaging of 3D microvasculature in vivo using reference-free processing of complex-valued B-scans

      Hybrid M-mode-like OCT imaging of 3D  microvasculature in vivo using reference-free  processing of complex-valued B-scans

      We propose a novel OCT-based method for visualizing microvasculature in 3D using reference-free processing of individual complex-valued B-scans with highly overlapped A-scans. In the lateral direction of such a B-scan, the amplitude and phase of speckles corresponding to vessel regions exhibit faster variability, and thus can be detected without comparison with other B-scans recorded in the same plane. This method combines elements of several existing OCT angiographic approaches, and exhibits: (i) enhanced robustness with respect to bulk tissue motion with frequencies up to tens of Hz; (ii) resolution of microcirculation images equal to that of structural images and (iii) possibility ...

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    6. Combining the correlation-stability approach to OCT elastography with the speckle-variance evaluation for quantifying the stiffness differences

      Combining the correlation-stability approach to OCT elastography with the speckle-variance evaluation for quantifying the stiffness differences

      We discuss an advanced variant of the correlation-stability (CS) approach to OCT elastography that is capable of quantifying the stiffness differences. The modified variant is based on natural combination of CS approach with the speckle-variance (SV) approach. It allows one to determine the strain dependence of the normalized speckle intensity variance function for two compared subsets taken from the OCT images corresponding to the initial and deformed states of the tissue. In previous studies we considered the basic dependence of the normalized speckle intensity variance function on the tissue strain under the assumption that the influence of translational displacements can ...

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    7. Towards free-hand implementation of OCT elastography: displacement-based approaches versus correlation-stability ones

      Towards free-hand implementation of OCT elastography: displacement-based approaches versus correlation-stability ones

      In this report, we present a comparative discussion of a recently proposed method of elastographic mapping based on comparison of correlation stability (CS) of different parts of sequentially obtained OCT images of the strained tissue and more conventional correlation approaches to elastographic mapping based on the initial reconstruction of the displacement field. The performed study is based on numerical simulations of speckle patterns generated by reproducing main features of image formation in real OCT scanners. Distortions of such speckle patterns caused by either translational motion of the studied sample or its straining are also incorporated in the developed simulation method ...

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    8. Elastographic mapping in optical coherence tomography using an unconventional approach based on correlation stability

      Elastographic mapping in optical coherence tomography using an unconventional approach based on correlation stability

      An approach to elastographic mapping in optical coherence tomography (OCT) using comparison of correlation stability of sequentially obtained intensity OCT images of the studied strained tissue is discussed. The basic idea is that for stiffer regions, the OCT image is distorted to a smaller degree. Consequently, cross-correlation maps obtained with compensation of trivial translational motion of the image parts using a sliding correlation window can represent the spatial distribution of the relative tissue stiffness. An important advantage of the proposed approach is that it allows one to avoid the stage of local-strain reconstruction via error-sensitive numerical differentiation of experimentally determined ...

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    9. Optical coherence tomography device and method having improved boundary control and distortion correction

      Optical coherence tomography device and method having improved boundary control and distortion correction

      Variants of an interferometric device are developed for examining internal structures of objects by means of optical coherence tomography, which allow for controlling a boundary location of the observation range. The device also allows for correcting a distortion of the tomographic image of the object under study, caused by lateral scanning, due to aberrations of the optical path length for the low-coherence optical radiation directed towards the object. Embodiments of the device include either one, or two fiber-optic controlled scanners, which in different combinations perform a function of in-depth scanning of the coherence window of low-coherence optical radiation within the ...

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    10. Single-shot full complex spectrum spectrometer-based OCT with a single-line photodiode array

      Single-shot full complex spectrum spectrometer-based OCT with a single-line photodiode array

      An efficient technique of simultaneous obtaining of quadrature spectral components of interference signal in spectrometer-based OCT using a single-line linear photodiode array is proposed. The components are obtained in air-spaced non-polarization interferometer by partition of reference beam onto two parts and using an achromatic phase shifter. Several setups are described and compared.

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    11. Digital refocusing in optical coherence tomography

      Digital refocusing in optical coherence tomography

      The problem of restoration Optical Coherence Tomography (OCT) images, acquired with tightly focused probing beam, in out-of-focus region for improving lateral resolution of the OCT has been considered. Phase stability issue has been discussed and phase equalization algorithm has been proposed. After phase equalization, the algorithm of digital refocusing, based on some methods from the DH, have been applied to the simulated as well as to experimental OCT data, acquired with tightly focused scanning beam to restore micrometer lateral resolution in the whole investigated volume.

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    12. Feature Of The Week 3/13/11: Russian Scientists Investigate Cross Polarization OCT for Early Bladder Cancer Detection

      Feature Of The Week 3/13/11: Russian Scientists Investigate Cross Polarization OCT for Early Bladder Cancer Detection
      Feature Of The Week 3/13/11: This week OCT News has another exciting “Feature Of The Week” presentation of exciting scientific results on the use of co- and cross-polarization OCT information applied to early bladder cancer detection.  The work is from the prestigious Institute of Applied and Fundamental Medicine at the Nizhny Novgorod State Medical Academy and the Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia.  Please note the authors have some excellent animation techniques so go slowly when viewing the slides so the animation can complete.   Capabilities of Cross Polarization Optical Coherence Tomography ...
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    13. Polarization-sensitive common path optical coherence reflectometry/tomography device

      Polarization-sensitive common path optical coherence reflectometry/tomography device
      Polarization sensitive common path OCT/OCR devices are presented. Optical radiation from a source is converted into two cross-polarized replicas propagating therethrough with a predetermined optical path length difference. The two cross-polarized replicas are then delivered to an associated sample by a delivering device, which is, preferably, an optical fiber probe. A combination optical radiation is produced in at least one secondary interferometer by combining a corresponding portion of an optical radiation returning from the associated sample with a reference optical radiation reflected from a tip of an optical fiber of the optical fiber probe. Subject to a preset optical ...
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    14. Coherent noise compensation improvement in spectral-domain optical coherence tomography

      Coherent noise compensation improvement in spectral-domain optical coherence tomography

      An efficient technique of the coherent noise separation of and compensation for in spectral-domain optical coherence tomography (SD-OCT) is proposed and validated. The coherent noise is separated during one exposure by modulating the relative delay of the signal and reference waves by a certain waveform. It is shown that the influence of internal motions in an object on the coherent noise separation quality can be reduced by increasing of modulation frequency. The technique has been numerically and experimentally validated.

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    15. Features of cross-polarization imaging

      Two compact systems for cross-polarization optical coherence tomography (CP-OCT) were developed using polarization-maintaining (PM) and single mode fibers. The systems allow simultaneous investigation of birefringence and depolarization properties of biological samples. Birefringence and degree of d ... [Proc. SPIE 6791, 679106 (2008)] published Mon Jun 9, 2008.
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    16. Method for studying a sample and optical interferometer for doing the same

      The present invention relates to the study of internal structure of objects by optical means. The invention presents a bi-directional sampling optical path for the low coherent optical radiation directed to the sample, i.e. a bi-directional sampling arm, and two unidirectional reference beams directed along a reference path designed as a loop. One of the reference beams propagates clockwise and the other propagates counterclockwise in the reference loop. The beam splitters non-reciprocal or polarization-dependent and by placing polarization-changing elements between the beam splitters and/or into the sampling arm and the reference loop. Thus the developed method and optical ...
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    17. Optical coherence tomography apparatus, optical fiber lateral scanner and a method for studying biological tissues in vivo

      In a method for in vivo diagnostics of a biological tissue covered with epithelium an image of the biological tissue is acquired with the aid of a beam in the visible or near IR range directed towards a biological tissue by visualizing the intensity of optical radiation backscattered by the biological tissue. The basal membrane of said biological tissue, which separates the epithelium from an underlying stroma, is identified in the acquired image and diagnostics is performed on basis of the form of the basal membrane. For diagnostics of biological tissue lining the surface of cavities and internal organs of ...
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    18. Optical coherence tomography apparatus, optical fiber lateral scanner and a method for studying biological tissues in vivo

      The present invention relates to the analysis of the internal structures of objects using optical means. According to the invention there were designed an apparatus suited for optical coherence tomography (OCT), an optical fiber lateral scanner (15), which is a part of said apparatus and is incorporated into an optical fiber probe (8), and a method for studying biological tissue in vivo, which allows for making a diagnostics of the biological tissue under study on basis of the state of the basal membrane (46). The moving part of lateral scanner (15) of sampling arm (4) of interferometer (2) is arranged ...
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    19. Optical coherent tomography apparatus, fiberoptic lateral scanner and method for studying biological tissues in vivo

      The present invention relates to the analysis of the internal structures of objects using optical means. According to the invention there were designed an apparatus suited for optical coherence tomography (OCT), an optical fiber lateral scanner (15), which is a part of said apparatus and is incorporated into an optical fiber probe (8), and a method for studying biological tissue in vivo, which allows for making a diagnostics of the biological tissue under, study on basis of the state of the basal membrane (46). The moving part of lateral scanner (15) of sampling arm (4) of interferometer (2) is arranged ...
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    20. Optical fiber interferometer with PZT scanning of interferometer arm optical length

      The invention is related to technical physics, in particular to devices for investigating the internal structure of objects and can be used in medicine for diagnostics of human organs and systems, in particular for optical coherence tomography and in technical diagnostics, for example technological process control. The invention relates to the creation of an optical-fiber interferometer, which, being used in a device for optical coherence tomography, allows one to investigate media with short time of changing of optical characteristics or its position relative to the optical probe, for example biotissues in vivo. The invention also relates to the creation of ...
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    21. Optical fiber interferometer and piezoelectric modulator

      The invention is related to technical physics, in particular to devices for investigating the internal structure of objects and can be used in medicine for diagnostics of human organs and systems, in particular for optical coherence tomography and in technical diagnostics, for example technological process control. The invention relates to the creation of an optical-fiber interferometer, which, being used in a device for optical coherence tomography, allows one to investigate media with short time of changing of optical characteristics or its position relative to the optical probe, for example biotissues in vivo. The invention also relates to the creation of ...
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    1-21 of 21
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  2. Topics in the News

    1. (21 articles) Valentin M. Gelikonov
    2. (20 articles) Grigory V. Gelikonov
    3. (18 articles) Institute of Applied Physics
    4. (9 articles) Nizhny Novgorod State Medical Academy
    5. (9 articles) Felix I. Feldchtein
    6. (8 articles) Natalia D. Gladkova
    7. (8 articles) Imalux
    8. (5 articles) University of Toronto
    9. (5 articles) Alexander M. Sergeev
    10. (5 articles) I. Alex Vitkin
    11. (1 articles) University of Illinois at Urbana-Champaign
    12. (1 articles) Duke University
    13. (1 articles) Joseph A. Izatt
    14. (1 articles) Stephen A. Boppart
    15. (1 articles) Sina Farsiu
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