1. Articles from V. M. Gelikonov

    1-23 of 23
    1. Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography

      Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography

      We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in optical coherence tomography. The method is based on the analysis of phase shifts of the neighboring scans, which are due to microscale displacements, and further compensation for these displacements by using phasefrequency correction in the spectral domain. Unlike the known correlation methods, the proposed method does not distort the represented shape of the object surface. Its operability is demonstrated in model experiments in the cases of harmonic and random types of the motion of the scattering ...

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    2. Improving the Transverse Resolution of Optical Coherence Tomography with a Finite Impulse Response Filter and a Series of Numerically Refocused Images

      Improving the Transverse Resolution of Optical Coherence Tomography with a Finite Impulse Response Filter and a Series of Numerically Refocused Images

      Among the numerous methods for improving the informative value of the optical coherence tomography (OCT), a special place is taken by the methods for increasing the spatial resolution of the resulting images. Increasing the resolution allows one to identify more clinically significant structures in OCT images and thus improve the diagnostic value of OCT. Since the transverse resolution of OCT images is determined by the physical principles different from those for the longitudinal resolution, the ways of their improvement are also different. The aim of the study is to develop a method for increasing the transverse resolution of OCT by ...

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    3. Measurement and Compensation for the Amplitude and Phase Spectral Distortions of an Interference Signal in Optical Coherence Tomography for the Relative Optical-Spectrum Width Exceeding 10%

      Measurement and Compensation for the Amplitude and Phase Spectral Distortions of an Interference Signal in Optical Coherence Tomography for the Relative Optical-Spectrum Width Exceeding 10%

      We describe a universal method of compensating for the arbitrary dispersion in the spectral and time domain optical coherence tomography systems. In combination with the amplitude method of correcting the optical-spectrum irregularities, this approach allows one to obtain the spectrally determined resolution if the instrument function is close to the Gaussian one. The efficiency of the method is demonstrated in the time and spectral domain optical coherence tomographies with the fully fiber-type optical systems for the relative optical-spectrum width exceeding 10%.

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    4. Time domain optical coherence tomography is a useful tool for diagnosing otitis media with effusion

      Time domain optical coherence tomography is a useful tool for diagnosing otitis media with effusion

      The usability of time-domain optical coherence tomography equipped with a flexible endoscopic probe for detecting effusion in the tympanic cavity is shown in the clinical environment. The possibility of assessing the dynamic properties of effusion, particularly its contained scatterers' mobility, is shown in real clinical cases. A method of comparative assessment of scatterers' mobility is proposed.

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    5. Cross-Polarization Optical Coherence Tomography with Active Maintenance of the Circular Polarization of a Sounding Wave in a Common Path System

      Cross-Polarization Optical Coherence Tomography with Active Maintenance of the Circular Polarization of a Sounding Wave in a Common Path System

      We consider a cross-polarization optical coherence tomography system with a common path for the sounding and reference waves and active maintenance of the circular polarization of a sounding wave. The system is based on the formation of birefringent characteristics of the total optical path, which are equivalent to a quarter-wave plate with a 45° orientation of its optical axes with respect to the linearly polarized reference wave. Conditions under which any light-polarization state can be obtained using a two-element phase controller are obtained. The dependence of the local cross-scattering coefficient of light in a model medium and biological tissue on ...

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    6. Equidistant Recording of the Spectral Components in Ultra-Wideband Spectral-Domain Optical Coherence Tomography

      Equidistant Recording of the Spectral Components in Ultra-Wideband Spectral-Domain Optical Coherence Tomography

      We develop an effective method for reducing nonequidistance when recording the spectral components of an interference signal in ultra-wideband spectral-domain optical coherence tomography. For this purpose, a corrector consisting of two identical prisms is used in a diffraction-grating spectrometer. The corrector rotation with respect to the diffraction-grating plane and a variation in the angle between the corrector elements allow one to adjust the equidistant spatial distribution of the spectral components in the photoreceiver array. It is shown experimentally that the developed method substitutes digital correction and leads to a significant reduction of the computational load in the optical coherence tomography ...

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    7. A data-acquisition and control system for spectral-domain optical coherence tomography with a speed of 91 912 A-scans/s based on a USB 3.0 interface

      A data-acquisition and control system for spectral-domain optical coherence tomography with a speed of 91 912 A-scans/s based on a USB 3.0 interface

      We describe a system of optical spectrum registration at the output of an interferometer with controlled phase shifts for an experimental device intended for visualizing the internal structure of an optically turbid specimen, using the method of spectral domain optical coherence tomography. A device for spectral domain optical coherence tomography based on a common-path optical scheme with a USB 3.0 interface for inputting data into a computer has been developed. An imaging speed of 91 912 A-scans/s has been attained. At the achieved speed, a series of live experiments were carried out to visualize the internal structure of ...

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    8. Recent Trends in Multimodal Optical Coherence Tomography. II. The Correlation-Stability Approach in OCT Elastography and Methods for Visualization of Microcirculation

      Recent Trends in Multimodal Optical Coherence Tomography. II. The Correlation-Stability Approach in OCT Elastography and Methods for Visualization of Microcirculation

      The second part of this paper continues the discussion of possibilities for combining functionally different types of biomedical characterization of tissues using optical coherence tomography (OCT). In the first part, polarization-sensitive imaging and conventional approaches to elastographic mapping in OCT were considered. Here, we consider an unconventional approach to elastographic mapping based on the analysis of variability of OCT images of the deformed tissue, omitting the stage of the displacement-field reconstruction. We also discuss methods for quantification of blood flow and visualization of microvasculature, some of which have much in common with the elastographic approach based on the analysis of ...

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    9. Improvement of lateral resolution of spectral domain optical coherence tomography images inout-of-focus regions with holographic data processing techniques

      Improvement of lateral resolution of spectral domain optical coherence tomography images inout-of-focus regions with holographic data processing techniques

      An analogy between spectral-domain optical coherence tomography (SD OCT) data and broadband digital holography data is considered. Based on this analogy, a method for processing SD OCT data, which makes it possible to construct images with a lateral resolution in the whole investigated volume equal to the resolution in the in-focus region, is developed. Several issues concerning practical application of the proposed method are discussed.

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    10. A model for simulating speckle-pattern evolution based on close to reality procedures used inspectral-domain OCT

      A model for simulating speckle-pattern evolution based on close to reality procedures used inspectral-domain OCT

      A robust model for simulating speckle-pattern evolution in optical coherence tomography (OCT) depending on the OCT system parameters and tissue deformation is reported. The model is based on the application of close to reality procedures used in spectral-domain OCT scanners. It naturally generates images reproducing properties of real images in spectral-domain OCT, including the pixelized structure and finite depth of unambiguous imaging, influence of the optical spectrum shape, dependence on the optical wave frequency and coherence length, influence of the tissue straining, etc. Good agreement with generally accepted speckle features and properties of real OCT images is demonstrated.

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    11. Achromatic registration of quadrature components of the optical spectrum in spectral domain opticalcoherence tomography

      Achromatic registration of quadrature components of the optical spectrum in spectral domain opticalcoherence tomography

      We have thoroughly investigated the method of simultaneous reception of spectral components with the achromatised quadrature phase shift between two portions of a reference wave, designed for the effective suppression of the 'mirror' artefact in the resulting image obtained by means of spectral domain optical coherence tomography (SD OCT). We have developed and experimentally tested a phase-shifting element consisting of a beam divider, which splits the reference optical beam into the two beams, and of delay lines being individual for each beam, which create a mutual phase difference of π/2 in the double pass of the reference beam. The phase ...

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    12. A correlation-stability approach to elasticity mapping in optical coherence tomography

      A correlation-stability approach to elasticity mapping in optical coherence tomography

      A variant of compressional optical coherence elastography for mapping of the relative stiffness of biological tissues is reported. Unlike conventionally discussed displacement-based (DB) elastography, in which the decrease in the cross-correlation between subsequently obtained images is a negative factor causing errors in the mapping displacement and strain fields, we propose to intentionally use the difference in the correlation stability (CS) for deformed-tissue regions with different stiffnesses. We compare the parameter ranges (in terms of noise-to-signal ratio and strain) in which the conventional DB and CS approaches are operable. It is shown that the CS approach has advantages such as a ...

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    13. Digital refocusing for transverse resolution improvement in optical coherence tomography

      Digital refocusing for transverse resolution improvement in optical coherence tomography

      Based on the fact that spectral domain (SD) optical coherence tomography (OCT) data can be treated as digital holography (DH) data acquired pointwise, we develop a spectral refocusing algorithm and show its ability to shift the focal region of OCT images obtained from SD OCT data acquired with a tightly focused scanning beam. Although refocusing itself depends on the refractive index of the studied media, we propose a procedure capable of restoring images with resolution equal to the resolution in the focal plane in the whole volume even in case of unknown refractive index of the media. As the proposed ...

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    14. Electronic interface systems for goals of spectral domain optical coherence tomography

      Electronic interface systems for goals of spectral domain optical coherence tomography

      A setup for visualizing the internal structure of media, which partially scatter radiation, using the spectral domain optical coherence tomography (OCT) method is described. The special complex of electron interface systems, ensuring the operating speed of the spectral domain OCT system at a level of 10000 A-scans (longitudinal scans along the depth) per second, high dynamic imaging range, and complete suppression of coherent noise peculiar to the spectral method has been designed to eliminate artifacts characteristic of this method.

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    15. Suppression of image autocorrelation artefacts in spectral domain optical coherence tomography and multiwave digital holography

      Suppression of image autocorrelation artefacts in spectral domain optical coherence tomography and multiwave digital holography

      An improved method for suppressing image artefacts in spectral domain optical coherence tomography (SD OCT) and multiwave digital holography, caused by the influence of coherent noise in the course of successive registration of an autocorrelation component and informative signal is reported. The method allows complete suppression of all types of coherent noises, provided that the sample of values used to record the autocorrelation component satisfies the conditions of Kotelnikov's theorem: in SD OCT — for the transverse structure of the studied medium, in multiwave digital holography — for the envelop function of the radiation source frequency tuning spectrum.

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    16. Suppression of image artifacts in the spectral-domain optical coherence tomography

      Suppression of image artifacts in the spectral-domain optical coherence tomography
      In this paper, we review methods for obtaining in vivo optical images of bio-objects with the resolution ranged from several units to tens of micrometers, namely, the methods of spectral-domain optical coherence tomography. We focus on problems that are specific of the spectral-domain optical coherence tomography, namely, the presence of coherent noise and mirror-symmetric phantoms in the image. On the basis of the most important relevant publications, we analyze possibilities of eliminating these drawbacks in modern devices.
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    17. Advantages of cross-polarization endoscopic optical coherence tomography in diagnosis of bladder neoplasia

      Advantages of cross-polarization endoscopic optical coherence tomography in diagnosis of bladder neoplasia
      We consider the cross-polarization OCT (CP OCT) that is focused on comparison of images resulting from cross-polarization and co-polarization scattering simultaneously. This technique provides information about microstructural and biochemical alterations in depolarizing tissue components (collagen). We found that mature type I collagen gives a strong signal in orthogonal polarization. CP OCT images of benign inflammatory processes always feature signal in orthogonal polarization, with layers and borders persisting to be well defined. In the presence of precancerous alterations, signal in orthogonal polarization is available in the image but it is irregular, disappearing in some areas. A CP OCT image of bladder ...
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    18. Coherent noise compensation in Spectral-Domain optical coherence tomography

      Abstract  An efficient technique for the separation of and compensation for coherent noise in spectral optical coherence tomography with parallel spectrum detection is proposed and validated. The coherent noise is separated during one exposure by modulating the mutual delay of the signal and reference waves by a certain law. It is shown that the influence of internal motions in an object on the quality of the coherent noise separation can be reduced by the modulation frequency increasing. The technique has been numerically and experimentally validated with the help of an optical coherence tomography (OCT) setup with a radiation source operating ...

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    19. Linear-wavenumber spectrometer for high-speed spectral-domain optical coherence tomography

      An equidistant (in the wavenumber) spectrometer based on a diffraction grating, a compensation prism, and a CCD linear array is developed and implemented for spectral-domain optical coherence tomography. A criterion is introduced for estimating the level of residual nonequidistance. This criterion allows one to determine the threshold compensation level necessary for obtaining the spectrally limited spatial resolution. The method is tested in spectral-domain optical coherent tomography systems at wavelengths of 1270 and 830 nm.
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    20. Cross-polarization endoscopic optical coherence tomography in urology

      Cross-polarization endoscopic optical coherence tomography in urology
      We present results obtained using a two-channel portable device for CP OCT based on the polarization-maintaining fiber. The device is capable of acquiring OCT images of the object in direct and orthogonal polarizations simultaneously. The OCT system has an endoscopic forward-looking probe (2.7 mm in diameter). The CP OCT imaging was done in 64 postoperative specimens, for 30 patients during cystoscopy with suspicion of urothelial neoplasia, and for 11 patients with prostatectomy due to cancer. After surgery in the tissue specimen we immediately introduced surgical suture and investigated a bladder wall by CP OCT. When comparing OCT images and ...
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    21. Optical Coherent Tomography for in vivo Determination of Changes in Hair Cross Section and Diameter during Treatment with Glucocorticosteroids - A Simple Method to Screen for Doping Substances?

      Eighty percent of hair follicles are in the growing phase. They grow approximately 0.3 mm/day. The hair follicles are surrounded by a close network of capillaries, which supplies them with nutrients. It is well known that substances which influence the metabolic processes of humans also influence hair growth. Steroids, which are used for doping in sport, are among these substances. In the present paper, optical coherent tomography is used for the analysis of changes in the hair structure during the application of steroids for the treatment of patients suffering from auto-immune diseases. Significant differences in the hair cross ...

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    22. Optimization of Fizeau-based optical coherence tomography with a reference Michelson interferometer

      Abstract  The method of Fizeau-based optical coherence tomography with a reference Michelson interferometer has been optimized. The real-system noise and dynamic range have been estimated. The time parameters of the system are optimized according to the proposed noise model. A good correspondence between the numerical estimates and experimental data is shown.
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    23. New approach to cross-polarized optical coherence tomography based on orthogonal arbitrarily polarized modes

      New approach to cross-polarized optical coherence tomography based on orthogonal arbitrarily polarized modes
      A novel cross-polarized optical coherence tomography (CP OCT) system is developed, which is based on standard isotropic single-mode fiber. We exploit the property of an arbitrary pair of orthogonal waves propagating in a singlemode fiber to maintain their orthogonality in the absence of anisotropy losses, regardless of the induced phase anisotropy. The well-known isotropic fiber based OCT scheme that commonly comprises an optical probe with a Fizeau interferometer and a compensating Michelson interferometer with Faraday mirrors is modified. We introduce an additional optical element to form the initial radiation into two mutually time-delayed and coherent waves that have strictly orthogonal ...
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    1-23 of 23
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  2. Topics in the News

    1. (23 articles) Valentin M. Gelikonov
    2. (22 articles) Institute of Applied Physics
    3. (19 articles) Grigory V. Gelikonov
    4. (15 articles) Pavel A. Shilyagin
    5. (11 articles) Dmitry A. Terpelov
    6. (6 articles) Nizhny Novgorod State Medical Academy
    7. (2 articles) University of Toronto
    8. (2 articles) Elena V. Zagaynova
    9. (2 articles) Natalia D. Gladkova
    10. (2 articles) Olga S. Streltsova
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    Cross-polarization endoscopic optical coherence tomography in urology Advantages of cross-polarization endoscopic optical coherence tomography in diagnosis of bladder neoplasia Suppression of image artifacts in the spectral-domain optical coherence tomography New approach to cross-polarized optical coherence tomography based on orthogonal arbitrarily polarized modes Suppression of image autocorrelation artefacts in spectral domain optical coherence tomography and multiwave digital holography Electronic interface systems for goals of spectral domain optical coherence tomography Optoretinography: optical measurements of human cone and rod photoreceptor responses to light Nodular skin lesions: correlation of reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) features OCT and Ophthalmology in the Age of Artificial Intelligence, Tuesday Oct 8, 2019 1:00P EDT Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography Pattern electroretinogram changes in patients with primary open-angle glaucoma in correlation with visual field and optical coherence tomography changes Objective evaluation of proliferative diabetic retinopathy using optical coherence tomography