1. Articles from I. A. Vitkin

    1-7 of 7
    1. 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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    2. Alternative Contrast Mechanism in Optical Coherence Tomography: Temporal Speckle Synchronization Effects

      Alternative Contrast Mechanism in Optical Coherence Tomography: Temporal Speckle Synchronization Effects

      We propose an alternative optical coherence tomography (OCT) contrast mechanism based on analysis of speckle temporal synchronization using B-mode OCT structural images. We show that the changes in synchronized speckle intensities with time may be used to distinguish between different tissue types, thus providing a novel and potentially useful contrast for OCT imaging. The developed methodology is tested in scattering flow phantoms, and in vivo on cervical cancer tumour grown within a mouse dorsal skin window chamber model. Derived speckle synchronization metric is compared with autocorrelation function analysis to demonstrate its different nature. The phantom and pre-clinical in vivo results ...

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    3. 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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    4. 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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    5. Imaging of electro-kinetic properties of tissue using the amplitude and the phase of optical coherence tomography

      Imaging of electro-kinetic properties of tissue using the amplitude and the phase of optical coherence tomography

      The electric field induced optical changes (EIOC) measured by the optical coherence tomography (OCT) reflect the local electro-kinetic properties of the tissue. In this study we developed a method to use the phase of the complex OCT images to map EIOC in tissue samples. Switching the polarity of the electric field induced significant reversible changes in the phase of the complex OCT images. Since the resulting phase was degraded by the noise an advanced signal processing algorithm was developed to obtain the EIOC images. The developed algorithm made it possible to get structural phase images from a standard commercial OCT ...

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    6. Quantification of glucose levels in flowing blood using M-mode swept source optical coherence tomography

      Quantification of glucose levels in flowing blood using M-mode swept source optical coherence tomography

      Abstract  The increase of glucose levels in blood changes the viscosity of flowing fluids and shape of the erythrocytes. Both of these can affect the details of light scattering as can be quantified via decorrelation times measured by optical coherence tomography (OCT). The relative contributions of these competing effects have been studied by examining the motion dynamics of deformable asymmetrical (red blood cells, RBCs with ∼7 μm diameter and ∼2 μm thickness) and non deformable symmetrical (polystyrene microspheres, PSM with 1.4 μm diameter) flowing scattering particles. The fluid flow under the action of gravity was modulated by changing the ...

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    7. Can temporal analysis of optical coherence tomography statistics report on dextrorotatory-glucose levels in blood?

      Can temporal analysis of optical coherence tomography statistics report on dextrorotatory-glucose levels in blood?
      We report the use of optical coherence tomography (OCT) for measuring dextrorotatory-glucose (D-glucose) in liquid phantoms and in drawn blood based on temporal dynamics of light scattering. The presence of D-glucose alters the medium viscosity, thus affecting the Brownian motion of the scatterers (polystyrene microspheres (PMS) in phantoms, red blood cells (RBCs) in blood) as measured by OCT. To quantify the effect, the signal autocorrelation functions were measured from M-mode OCT data and exponentially fit to obtain the decorrelation times. These were then related to translational (and rotational, in case of asymmetric scatterers) diffusion coefficients which enabled the determination of ...
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    1-7 of 7
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    1. (7 articles) University of Toronto
    2. (7 articles) I. Alex Vitkin
    3. (3 articles) Ryerson University
    4. (3 articles) Grigory V. Gelikonov
    5. (2 articles) Institute of Applied Physics
    6. (2 articles) Nizhny Novgorod State Medical Academy
    7. (2 articles) Valentin M. Gelikonov
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    Can temporal analysis of optical coherence tomography statistics report on dextrorotatory-glucose levels in blood? Quantification of glucose levels in flowing blood using M-mode swept source optical coherence tomography Imaging of electro-kinetic properties of tissue using the amplitude and the phase of optical coherence tomography Recent Trends in Multimodal Optical Coherence Tomography. II. The Correlation-Stability Approach in OCT Elastography and Methods for Visualization of Microcirculation Quantitative Cross-Polarization Optical Coherence Tomography Detection of Infiltrative Tumor Margin in a Rat Glioma Model: a Pilot Study Alternative Contrast Mechanism in Optical Coherence Tomography: Temporal Speckle Synchronization Effects Cross-Polarization Optical Coherence Tomography with Active Maintenance of the Circular Polarization of a Sounding Wave in a Common Path System 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