1. Articles from G. V. Gelikonov

    1-26 of 26
    1. Application of Phase Correction for Compensation of Motion Artifacts in Spectral-Domain Optical Coherence Tomography

      Application of Phase Correction for Compensation of Motion Artifacts in Spectral-Domain Optical Coherence Tomography

      The application of computational methods to correct distortions in spectral-domain optical coherence tomography due to fast probe movements relative to a studied object is described. This technique is intended for use in endoscopy or in the study of external biological tissues using a handheld probe. The effectiveness of the method was confirmed experimentally.

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    2. Optical coherence angiography for pre-treatment assessment and treatment monitoring following photodynamic therapy: a basal cell carcinoma patient study

      Optical coherence angiography for pre-treatment assessment and treatment monitoring following photodynamic therapy: a basal cell carcinoma patient study

      Microvascular networks of human basal cell carcinomas (BCC) and surrounding skin were assessed with optical coherence angiography (OCA) in conjunction with photodynamic therapy (PDT). OCA images were collected and analyzed in 31 lesions pre-treatment, and immediately/24 hours/3–12 months post-treatment. Pre-treatment OCA enabled differentiation between prevalent subtypes of BCC (nodular and superficial) and nodular-with-necrotic-core BCC subtypes with a diagnostic accuracy of 78%; this can facilitate more accurate biopsy reducing sampling error and better therapy regimen selection. Post-treatment OCA images at 24 hours were 98% predictive of eventual outcome. Additional findings highlight the importance of pre-treatment necrotic core, vascular ...

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    3. Elimination of Artifacts Caused by the Nonidentity of Parallel Signal-Reception Channels in Spectral Domain Optical Coherence Tomography

      Elimination of Artifacts Caused by the Nonidentity of Parallel Signal-Reception Channels in Spectral Domain Optical Coherence Tomography

      We study the causes of artifact appearance in the images obtained by the method of spectral domain optical coherence tomography with parallel reception of the optical-spectrum components, which are manifested in repetition and overlay of the structural elements of the images of the studied medium with a shift in depth. It is shown that nonidentity of the transfer characteristics of the channels of the multichannel photoreceiving elements is one of the sources of such artifacts. A numerical method for eliminating such artifacts is proposed and experimentally verified. This method is based on using the models whose parameters are estimated by ...

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    4. 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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    5. 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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    6. Semi-analytical full-wave model for simulations of scans in optical coherence tomography with accounting for beam focusing and the motion of scatterers

      Semi-analytical full-wave model for simulations of scans in optical coherence tomography with accounting for beam focusing and the motion of scatterers

      A full-wave model for simulating images in spectral-domain optical coherence tomography (OCT) with rigorous accounting for the beam-focusing effects is developed. Due to the analytical description of beam focusing, the model is computationally rather efficient. It also uses a rigorous numerical summation of the contributions of the localized sub-resolution scatterers, accounting for variations in the phase-amplitude parameters of the incident and backscattered optical waves, with a subsequent integration of the latter over the objective aperture. In the limit of a weakly focused beam, the developed model has allowed for the validatation of the earlier proposed simplified model with a constant-radius ...

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    7. 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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    8. 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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    9. 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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    10. 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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    11. Quantitative Cross-Polarization Optical Coherence Tomography Detection of Infiltrative Tumor Margin in a Rat Glioma Model: a Pilot Study

      Quantitative Cross-Polarization Optical Coherence Tomography Detection of Infiltrative Tumor Margin in a Rat Glioma Model: a Pilot Study

      Determining boundaries of infiltrative glial tumors remains a challenging problem in neurooncology. Optical coherence tomography (OCT) with cross-polarization (CP) visualization is a promising technique as a surgical guidance tool. However, the outcome of the procedures performed under OCT guidance strongly depends on the surgeon’s qualification. Thus, a quantitative method for assessing resection margins with OCT is required. The aim of this study was to develop a robust quantitative approach for CP OCT data to differentiate tumorous from non-tumorous tissues in a rat glioma model. Materials and Methods. The study was carried out on the rats’ brains (n=6) with ...

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    12. In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography

      In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography

      Mucositis is the limiting toxicity of radio(chemo)therapy of head and neck cancer. Diagnostics, prophylaxis and correction of this condition demand new accurate and objective approaches. Here we report on an in vivo longitudinal monitoring of the oral mucosa dynamics in 25 patients during the course of radiotherapy of oropharyngeal and nasopharyngeal cancer using multifunctional optical coherence tomography (OCT). A spectral domain OCT system with a specially-designed oral imaging probe was used. Microvasculature visualization was based on temporal speckle variations of the full complex signal evaluated by high-pass filtering of 3D data along the slow scan axis. Angiographic image ...

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    13. 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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    14. The Development of the Methodology of Monitoring Experimental Tumors Using Multimodal Optical Coherence Tomography: the Choice of an Optimal Tumor Model

      The Development of the Methodology of Monitoring Experimental Tumors Using Multimodal Optical Coherence Tomography: the Choice of an Optimal Tumor Model

      The objective of the research was to study the features of transplantation, growth and visualization of experimental tumors of animals, using multi-functional optical coherence tomography (OCT) to develop the methodology of evaluation of individual tumor response to anti-cancer therapy. Materials and Methods. The research was carried out using an experimental high-speed spectral-domain multimodal OCT system developed at the Institute of Applied Physics of the Russian Academy of Sciences (Russia). The technical characteristics of the system are the following: speed of information acquisition, 20,000 А-scans per second; 1.3 μm wavelength; frame size, approximately 4×2 mm; lateral resolution, 25 ...

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    15. 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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    16. 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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    17. 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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    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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    23. 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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    24. 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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    25. 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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    26. 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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    1-26 of 26
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    1. (26 articles) Grigory V. Gelikonov
    2. (24 articles) Institute of Applied Physics
    3. (22 articles) Valentin M. Gelikonov
    4. (16 articles) Pavel A. Shilyagin
    5. (13 articles) Dmitry A. Terpelov
    6. (7 articles) Nizhny Novgorod State Medical Academy
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    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 Digital refocusing for transverse resolution improvement in optical coherence tomography Recent Trends in Multimodal Optical Coherence Tomography. II. The Correlation-Stability Approach in OCT Elastography and Methods for Visualization of Microcirculation The Development of the Methodology of Monitoring Experimental Tumors Using Multimodal Optical Coherence Tomography: the Choice of an Optimal Tumor Model In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography Optical coherence tomography features of neovascularization in proliferative diabetic retinopathy: a systematic review Retinal microvascular metrics in untreated essential hypertensives using optical coherence tomography angiography Optical coherence tomography angiography findings of fellow eye of proliferative macular telangiectasia type 2: Long term study Reorganization of the perifoveal microvasculature after macular hole closure assessed via optical coherence tomography angiography Optical coherence tomography angiography (OCTA) findings in Serpiginous Choroiditis