1. Articles from Pavel A. Shilyagin

    1-12 of 12
    1. Cross-polarization optical coherence tomography for brain tumor imaging

      Cross-polarization optical coherence tomography for brain tumor imaging

      This paper considers valuable visual assessment criteria for distinguishing between tumorous and non-tumorous tissues, intraoperatively, using cross-polarization OCT (CP OCT) – OCT with a functional extension, that enables detection of the polarization properties of the tissues in addition to their conventional light scattering. Materials and methods. The study was performed on 176 ex vivo human specimens obtained from 30 glioma patients. To measure the degree to which the typical parameters of CP OCT images can be matched to the actual histology, 100 images of tumors and white matter were selected for visual analysis to be undertaken by three “single-blinded” investigators. An ...

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    2. Digital refocusing in optical coherence tomography using finite impulse response filters

      Digital refocusing in optical coherence tomography using finite impulse response filters

      A finite impulse response filter, which shifts the focal plane in optical coherence tomography (OCT) images, is proposed. Since several OCT images with the focal plane in various positions can be fused into one image with increased lateral resolution, such a filter facilitates the creation of an OCT system with numerically increased lateral resolution, operating in real-time, i.e. showing one OCT B-scan with increased lateral resolution while collecting data for the next B-scan. Since the proposed real-time resolution enhancement method is phase-sensitive, the method for estimating and compensating phase shifts between consecutive B-scans during data acquisition is also discussed.

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    3. Medium chromatic dispersion calculation and correction in spectral-domain optical coherence tomography

      Medium chromatic dispersion calculation and correction in spectral-domain optical coherence tomography

      A method for determining and correcting distortions in spectral-domain optical coherence tomography images caused by medium dispersion was developed. The method is based on analysis of the phase distribution of the interference signal recorded by an optical coherence tomography device using an iterative approach to find and compensate for the effect of a medium’s chromatic dispersion on point-spread function broadening in optical coherence tomography. This enables compensation of the impact of medium dispersion to an accuracy of a fraction of a radian (units of percent) while avoiding additional measurements and solution of the optimization problem. The robustness of the ...

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    4. Correction of aberrations in digital holography using the phase gradient autofocus technique

      Correction of aberrations in digital holography using the phase gradient autofocus technique

      We propose a method for correcting aberrations in digital holography based on the principles of computational adaptive optics using the phase gradient autofocus technique that demands no reference measurements. The method requires a priori information on the relative positions of the elements of the optical setup. It is applicable for sufficiently smooth optical aberrations. This technique does not impose any restrictions on the magnitude of the scattered optical field phase distortions caused by the object structure. The efficacy of the proposed method is demonstrated through numerical simulation and experimental verification.

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    5. Noniterative method of reconstruction optical coherence tomography images with improved lateralresolution in semitransparent media

      Noniterative method of reconstruction optical coherence tomography images with improved lateralresolution in semitransparent media

      A method of OCT imaging with a resolution throughout the investigated volume equal to the resolution in the best-focused region is described. It is based on summation of three-dimensional scattered field distributions at the wavelengths determined by OCT source spectral decomposition. A method of finding parameters needed for algorithmic realization of the summation is also proposed. The proposed approaches are tested on several model media, including biological ones.

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    6. Feature Of The Week 4/1/12: Russian Institute of Applied Physics Investigates Digital Refocusing in Optical Coherence Tomography Systems

      Feature Of The Week 4/1/12: Russian Institute of Applied Physics Investigates Digital Refocusing in Optical Coherence Tomography Systems

      Over the past few years using electronic post optical detection processing to create a synthetic receiver field-of-view has become a very promising technique for offering improved performance in biomedical optical imaging systems. Various approaches around this basic theme have been used in OCT and non-OCT systems such as synthetic aperture radar, digital holography, and other microscopy techniques.  The approach not only allows for improving the classic depth-of-focus vs lateral resolution tradeoff in OCT systems but offers other promising performance enhancement such as eliminating the need for deformable mirrors in adaptive optics ophthalmic imaging and application benefits in other fields such ...

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    7. 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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    8. 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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    9. Blind deconvolution algorithm for restoration OCT images with diffraction limited resolution

      Blind deconvolution algorithm for restoration OCT images with diffraction limited resolution
      In this paper we describe an algorithm which is able to compensate an unknown defocus. This algorithm has been applied to recovering defocused en-face Optical Coherence Tomography images. Lateral resolution about 5 um has been achieved at distance from focal plane about 10 Rayleigh lengths.. Both numerical simulations and experiment have been performed to demonstrate the ability of the method.
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    10. 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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    11. Cross-polarization optical coherence tomography for early bladder-cancer detection: statistical study

      Cross-polarization optical coherence tomography for early bladder-cancer detection: statistical study
      The capabilities of cross-polarization optical coherence tomography (CP OCT) for early bladder-cancer detection are assessed in statistical study and compared with the traditional OCT. Unlike the traditional OCT that demonstrates images only in copolarization, CP OCT acquires images in cross-polarization and copolarization simultaneously. 116 patients with localized flat suspicious lesions in the bladder were enrolled, 360 CP OCT images were obtained and analyzed. CP OCT demonstrated sensitivity 93.7% (vs. 81.2%, <0.0001), specificity 84% (vs. 70.0%, <0.001) and accuracy 85.3% (vs. 71.5%, <0.001) in detecting flat malignant bladder lesions, which is significantly better ...
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    12. 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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    1-12 of 12
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    1. (12 articles) Institute of Applied Physics
    2. (12 articles) Grigory V. Gelikonov
    3. (12 articles) Pavel A. Shilyagin
    4. (11 articles) Valentin M. Gelikonov
    5. (5 articles) Dmitry A. Terpelov
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    7. (3 articles) Natalia D. Gladkova
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    Coherent noise compensation improvement in spectral-domain optical coherence tomography Cross-polarization optical coherence tomography for early bladder-cancer detection: statistical study Feature Of The Week 3/13/11: Russian Scientists Investigate Cross Polarization OCT for Early Bladder Cancer Detection Blind deconvolution algorithm for restoration OCT images with diffraction limited resolution Single-shot full complex spectrum spectrometer-based OCT with a single-line photodiode array Digital refocusing in optical coherence tomography Feature Of The Week 4/1/12: Russian Institute of Applied Physics Investigates Digital Refocusing in Optical Coherence Tomography Systems Noniterative method of reconstruction optical coherence tomography images with improved lateralresolution in semitransparent media Correction of aberrations in digital holography using the phase gradient autofocus technique Medium chromatic dispersion calculation and correction in spectral-domain optical coherence tomography Remote scanning for ultra-large field of view in wide-field microscopy and full-field OCT Inadequate Intimal Angiogenesis as a Source of Coronary Plaque Instability