1. Articles from Ivan Popov

    1-7 of 7
    1. Impact of velocity gradient in Poiseuille flow on the statistics of coherent radiation scattered by flowing Brownian particles in optical coherence tomography

      Impact of velocity gradient in Poiseuille flow on the statistics of coherent radiation scattered by flowing Brownian particles in optical coherence tomography

      A closed-form expression is obtained for the temporal correlation function of the scattered radiation detected in optical coherence tomography (OCT), taking into account the flow velocity gradient across the OCT detection volume in the suspension of flowing Brownian particles. The analytical approach we use includes both the laser beam and wavefront curvature radii changing over the depth. Also, we compare our results with a previously obtained theoretical model, partially an empirical approach. Our findings suggest the importance of the flow velocity gradient for accurate measurements of flow velocity vector, particle diffusivity, shear-induced diffusion, and potentially other OCT applications.

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    2. K-distribution three-dimensional mapping of biological tissues in optical coherence tomography

      K-distribution three-dimensional mapping of biological tissues in optical coherence tomography

      Probability density function (PDF) analysis with K-distribution model of optical coherence tomography (OCT) intensity signals has previously yielded a good representation of the average number of scatterers in a coherence volume for microspheres-in-water systems, and has shown initial promise for biological tissue characterization. In this work, we extend these previous findings, based on single point M-mode or 2D slice analysis, to full 3D imaging maps of the shape parameter α of the K-distribution PDF. After selecting a suitably-sized 3D evaluation window, and verifying methodology in phantoms the resultant parametric α images obtained in different animal tissues (rat liver and brain) show new ...

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    3. Statistical properties of dynamic speckles from flowing Brownian scatterers in the vicinity of the image plane in optical coherence tomography

      Statistical properties of dynamic speckles from flowing Brownian scatterers in the vicinity of the image plane in optical coherence tomography

      A closed-form analytical expression is obtained for the spatio-temporal correlation function of the scattered radiation detected in fiber-based optical coherence tomography (OCT), assuming a clean optical system arrangement in the OCT sample arm. It is shown that the transverse flow component causes purely translational speckle motion with the predicted speckle velocity 2x higher than the velocity of the flowing particles as would be observed in the image plane under incoherent illumination. It is also shown that both speckle velocity and speckle radius do not depend on the position of the scattering volume relative to the focal plane, hence the derived ...

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    4. Analysis of scattering statistics and governing distribution functions in optical coherence tomography

      Analysis of scattering statistics and governing distribution functions in optical coherence tomography

      The probability density function (PDF) of light scattering intensity can be used to characterize the scattering medium. We have recently shown that in optical coherence tomography (OCT), a PDF formalism can be sensitive to the number of scatterers in the probed scattering volume and can be represented by the K-distribution, a functional descriptor for non-Gaussian scattering statistics. Expanding on this initial finding, here we examine polystyrene microsphere phantoms with different sphere sizes and concentrations, and also human skin and fingernail in vivo . It is demonstrated that the K-distribution offers an accurate representation for the measured OCT PDFs. The behavior of ...

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    5. Probability density function formalism for optical coherence tomography signal analysis

      Probability density function formalism for optical coherence tomography signal analysis

      The distribution of backscattered intensities as described by the probability density function (PDF) of tissue-scattered light contains information that may be useful for tissue assessment and diagnosis, including characterization of its pathology. In this Letter, we examine the PDF description of the light scattering statistics in a well characterized tissue-like particulate medium using optical coherence tomography (OCT). It is shown that for low scatterer density, the governing statistics depart considerably from a Gaussian description and follow the K distribution for both OCT amplitude and intensity. The PDF formalism is shown to be independent of the scatterer flow conditions; this is ...

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    6. Dynamic light scattering by flowing Brownian particles measured with optical coherence tomography: impact of the optical system

      Dynamic light scattering by flowing Brownian particles measured with optical coherence tomography: impact of the optical system

      The study of flowing Brownian particles finds numerous biomedical applications, ranging from blood flow analysis to diffusion research. A mathematical model for the correlation function of laser radiation scattered by flowing Brownian particles measured with fiber-based optical coherence tomography (OCT), which accounts for the effects of sample arm optics, is presented. It is shown that the parameters of an OCT optical system of any complexity can be taken into account by using the ABCD ray tracing matrix approach. Specifically, the impact of any optical system can be characterized by the changes in the effective beam radius, which replaces the Gaussian ...

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    7. Dynamic light scattering arising from flowing Brownian particles: analytical model in optical coherence tomography conditions

      Dynamic light scattering arising from flowing Brownian particles: analytical model in optical coherence tomography conditions

      The statistical model of scattered by flowing Brownian particles coherent radiation is suggested. The model includes the random Doppler shifts caused by particle Brownian motion and the speckle fluctuations caused primarily by the flow motion of particles. Analytical expressions are obtained for the correlation function, power spectrum, and spectral width of scattered radiation in the imaging geometry typically used in optical coherence tomography (OCT). It is shown that the spectral density has the Voigt shape, a well-known spectral profile from atomic and molecular spectroscopy. The approach enables the choice of the experimental regimes for the measurement of Brownian particle motion ...

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    1-7 of 7
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    Dynamic light scattering arising from flowing Brownian particles: analytical model in optical coherence tomography conditions Dynamic light scattering by flowing Brownian particles measured with optical coherence tomography: impact of the optical system Probability density function formalism for optical coherence tomography signal analysis Analysis of scattering statistics and governing distribution functions in optical coherence tomography Statistical properties of dynamic speckles from flowing Brownian scatterers in the vicinity of the image plane in optical coherence tomography K-distribution three-dimensional mapping of biological tissues in optical coherence tomography Impact of velocity gradient in Poiseuille flow on the statistics of coherent radiation scattered by flowing Brownian particles in optical coherence tomography Conavi Medical and Japan Lifeline Announce MHLW Approval of Novasight Hybrid Intravascular Imaging System for Japanese Market Capsule Endomicroscopy for Visualization of the Small Intestine in EED Population in Pakistan Three-dimensional detection and quantification of defects in SiC by optical coherence tomography University of Illinois at Chicago Receives NIH Grant for Functional Tomography of Neurovascular Coupling Interactions in Healthy and Diseased Retinas Dyad Medical Receives NIH Grant for Software For OCT Analysis of Vascular Stents