1. Kostadinka K. Bizheva

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    1. Mentioned In 58 Articles

    2. 250 kHz, 1.5 µm resolution SD-OCT for in-vivo cellular imaging of the human cornea

      250 kHz, 1.5 µm resolution SD-OCT for in-vivo cellular imaging of the human cornea
      We present the first spectral domain optical coherence tomography (SD-OCT) system that combines an isotropic imaging resolution of ~1.5 m in biological tissue with a 250 kHz image acquisition rate, for in vivo non-contact, volumetric imaging of the cellular structure of the human cornea. OCT images of the healthy human cornea acquired with this system reveal the cellular structure of the corneal epithelium, cellular debris and mucin clusters in ...
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    3. Comparative Study of Optical Coherence Tomography Angiography and Phase-Resolved Doppler Optical Coherence Tomography for Measurement of Retinal Blood Vessels Caliber

      Comparative Study of Optical Coherence Tomography Angiography and Phase-Resolved Doppler Optical Coherence Tomography for Measurement of Retinal Blood Vessels Caliber
      Purpose : To compare the accuracy of Doppler optical coherence tomography (DOCT) and OCT angiography (OCTA) for measuring retinal blood vessel caliber at different flow rates. Methods : A research-grade 1060-nm OCT system with 3.5-m axial resolution in retinal tissue and 92,000 A scan/s image acquisition rate was used in this study. DOCT and OCTA measurements were acquired both from a flow phantom and in vivo from retinal blood ...
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    4. Dense concentric circle scanning protocol for measuring pulsatile retinal blood flow in rats with Doppler optical coherence tomography

      Dense concentric circle scanning protocol for measuring pulsatile retinal blood flow in rats with Doppler optical coherence tomography
      The variability in the spatial orientation of retinal blood vessels near the optic nerve head (ONH) results in imprecision of the measured Doppler angle and therefore the pulsatile blood flow (BF), when those parameters are evaluated using Doppler OCT imaging protocols based on dual-concentric circular scans. Here, we utilized a dense concentric circle scanning protocol and evaluated its precision for measuring pulsatile retinal BF in rats for different numbers of ...
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    5. In-vivo imaging of the palisades of Vogt and the limbal crypts with sub-micrometer axial resolution optical coherence tomography

      In-vivo imaging of the palisades of Vogt and the limbal crypts with sub-micrometer axial resolution optical coherence tomography
      A research-grade OCT system was used to image in-vivo and without contact with the tissue, the cellular structure and microvasculature of the healthy human corneo-scleral limbus. The OCT system provided 0.95 m axial and 4 m (2 m) lateral resolution in biological tissue depending on the magnification of the imaging objective. Cross-sectional OCT images acquired tangentially from the inferior limbus showed reflective, loop-like features that correspond to the fibrous ...
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    6. Relationship between vessel diameter and depth measurements within the limbus using ultra-high resolution optical coherence tomography

      Relationship between vessel diameter and depth measurements within the limbus using ultra-high resolution optical coherence tomography
      To establish a relationship between the diameter and depth position of vessels in the superior and inferior corneo-scleral limbus using ultra-high resolution optical coherence tomography (UHR-OCT). Methods Volumetric OCT images of the superior and inferior limbus were acquired from 14 healthy subjects with a research-grade UHR-OCT system. Differences in vessel diameter and depth between superior and inferior limbus were analyzed using repeated measured ANOVA in SPSS and R. Results The ...
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    7. Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas

      Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas
      Corneal degenerative conditions such as keratoconus (KC) cause progressive damage to the anterior corneal tissue and eventually severely compromise visual acuity. The ability to visualize corneal tissue damage in-vivo at cellular or sub-cellular level at different stages of development of KC and other corneal diseases, can aid the early diagnostics as well as the development of more effective treatment approaches for various corneal pathologies, including keratoconus. Here, we present the ...
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    8. 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 ...
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    9. In Vivo Imaging and Morphometry of the Human Pre-Descemet's Layer and Endothelium With Ultrahigh-Resolution Optical Coherence Tomography

      In Vivo Imaging and Morphometry of the Human Pre-Descemet's Layer and Endothelium With Ultrahigh-Resolution Optical Coherence Tomography
      Purpose : To visualize in vivo and quantify the thickness of the posterior corneal layers: the acellular pre-Descemet's layer (PDL), Descemet's membrane (DM), and endothelium (END) in healthy subjects, using ultrahigh-resolution optical coherence tomography (UHR-OCT). Methods : A research-grade, 800-nm UHR-OCT system with 0.95-m axial resolution in corneal tissue was used to image in vivo the posterior cornea in healthy subjects. The system offers approximately 98 dB sensitivity for ...
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    10. Quantitative assessment of oral microstructural and microvascular changes in late oral radiation toxicity, using noninvasive in-vivo optical coherence tomography

      Quantitative assessment of oral microstructural and microvascular changes in late oral radiation toxicity, using noninvasive in-vivo optical coherence tomography
      Background and objectives: About half of the head and neck cancer patients treated with radiotherapy suffer from late radiation effects months to years after the treatment. The most common diagnosis and monitoring methods for such oral toxicities are based on surface examination of the oral tissue, which is subjective. Therefore, subsurface imaging and image quantification tools can be highly useful for monitoring these late effects as these approaches are more ...
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    11. Depth Compensated Spectral Domain Optical Coherence Tomography via Digital Compensation

      Depth Compensated Spectral Domain Optical Coherence Tomography via Digital Compensation
      Spectral Domain Optical Coherence Tomography (SD-OCT) is a well-known imaging modality which allows for \textit{in-vivo} visualization of the morphology of different biological tissues at cellular level resolutions. The overall SD-OCT imaging quality in terms of axial resolution and Signal-to-Noise Ratio (SNR) degrades with imaging depth, while the lateral resolution degrades with distance from the focal plane. This image quality degradation is due both to the design of the SD-OCT ...
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    12. Lateral resolution enhancement via imbricated spectral domain optical coherence tomography in a maximum-a-posterior reconstruction framework

      Lateral resolution enhancement via imbricated spectral domain optical coherence tomography in a maximum-a-posterior reconstruction framework
      The lateral resolution of a Spectral Domain Optical Coherence Tomography (SD-OCT) image is limited by the focusing properties of the OCT imaging probe optics, the wavelength range which SD-OCT system operates at, spherical and chromatic aberrations induced by the imaging optics, the optical properties of the imaged object, and in the special case of in-vivo retinal imaging by the optics of the eye. This limitation often results in challenges with ...
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    13. Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions

      Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions
      Background Optical coherence tomography (OCT) is a minimally invasive imaging technique, which utilizes the spatial and temporal coherence properties of optical waves backscattered from biological material. Recent advances in tunable lasers and infrared camera technologies have enabled an increase in the OCT imaging speed by a factor of more than 100, which is important for retinal imaging where we wish to study fast physiological processes in the biological tissue. However ...
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  2. About Kostadinka K. Bizheva

    Kostadinka K. Bizheva

    Kostadinka K. Bizheva is an Assistant Professor in the Department of Physics and Astronomy at the University of Waterloo in Ontario Canada.  Research Interests: biomedical optics, optical coherence tomography, tissue optics, optical spectroscopy, confocal and fluorescence microscopy, ultrafast optics.