1. Articles from Kirill V. Larin

    1-24 of 137 1 2 3 4 5 6 »
    1. Heartbeat optical coherence elastography: corneal biomechanics in vivo

      Heartbeat optical coherence elastography: corneal biomechanics in vivo

      Significance: Mechanical assessment of the cornea can provide important structural and functional information regarding its health. Current clinically available tools are limited in their efficacy at measuring corneal mechanical properties. Elastography allows for the direct estimation of mechanical properties of tissues in vivo but is generally performed using external excitation force. Aim: To show that heartbeat optical coherence elastography (Hb-OCE) can be used to assess the mechanical properties of the cornea in vivo. Approach: Hb-OCE was utilized to detect Hb-induced deformations in the rabbit cornea in vivo without the need for external excitation. Furthermore, we demonstrate how this technique can ...

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    2. In Vivo Human Corneal Shear-wave Optical Coherence Elastography

      In Vivo Human Corneal Shear-wave Optical Coherence Elastography

      SIGNIFICANCE A novel imaging technology, dynamic optical coherence elastography (OCE), was adapted for clinical noninvasive measurements of corneal biomechanics. PURPOSE Determining corneal biomechanical properties is a long-standing challenge. Elasticity imaging methods have recently been developed and applied for clinical evaluation of soft tissues in cancer detection, atherosclerotic plaque evaluation, surgical guidance, and more. Here, we describe the use of dynamic OCE to characterize mechanical wave propagation in the human cornea in vivo , thus providing a method for clinical determination of corneal biomechanical properties. METHODS High-resolution phase-sensitive optical coherence tomography imaging was combined with microliter air-pulse tissue stimulation to perform dynamic ...

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    3. Confocal air-coupled ultrasonic optical coherence elastography probe for quantitative biomechanics

      Confocal air-coupled ultrasonic optical coherence elastography probe for quantitative biomechanics

      We present an air-coupled ultrasonic radiation force probe co-focused with a phase-sensitive optical coherence tomography (OCT) system for quantitative wave-based elastography. A custom-made 1 MHz spherically focused piezoelectric transducer with a concentric 10 mm wide circular opening allowed for confocal micro-excitation of waves and phase-sensitive OCT imaging.

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    4. Dynamic Optical Coherence Elastography of the Anterior Eye: Understanding the Biomechanics of the Limbus

      Dynamic Optical Coherence Elastography of the Anterior Eye: Understanding the Biomechanics of the Limbus

      Purpose : Currently, the biomechanical properties of the corneo-scleral limbus when the eye-globe deforms are largely unknown. The purpose of this study is to evaluate changes in elasticity of the cornea, sclera, and limbus when subjected to different intraocular pressures (IOP) using wave-based optical coherence elastography (OCE). Special attention was given to the elasticity changes of the limbal region with respect to the elasticity variations in the neighboring corneal and scleral regions. Methods : Continuous harmonic elastic waves (800 Hz) were mechanically induced in the sclera near the corneo-sclera limbus of in situ porcine eye-globes ( n = 8). Wave propagation was imaged using ...

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    5. Optical coherence tomography angiography to evaluate murine fetal brain vasculature changes caused by prenatal exposure to nicotine

      Optical coherence tomography angiography to evaluate murine fetal brain vasculature changes caused by prenatal exposure to nicotine

      Maternal smoking causes several defects ranging from intrauterine growth restriction to sudden infant death syndrome and spontaneous abortion. While several studies have documented the effects of prenatal nicotine exposure in development and behavior, acute vasculature changes in the fetal brain due to prenatal nicotine exposure have not been evaluated yet. This study uses correlation mapping optical coherence angiography to evaluate changes in fetal brain vasculature flow caused by maternal exposure to nicotine during the second trimester-equivalent of gestation in a mouse model. The effects of two different doses of nicotine were evaluated. Results showed a decrease in the vasculature for ...

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    6. Heartbeat OCE: corneal biomechanical response to simulated heartbeat pulsation measured by optical coherence elastography

      Heartbeat OCE: corneal biomechanical response to simulated heartbeat pulsation measured by optical coherence elastography

      Significance: It is generally agreed that the corneal mechanical properties are strongly linked to many eye diseases and could be used to assess disease progression and response to therapies. Elastography is the most notable method of assessing corneal mechanical properties, but it generally requires some type of external excitation to induce a measurable displacement in the tissue. Aim: We present Heartbeat Optical Coherence Elastography (Hb-OCE), a truly passive method that can measure the elasticity of the cornea based on intrinsic corneal displacements induced by the heartbeat. Approach: Hb-OCE measurements were performed in untreated and UV-A/riboflavin cross-linked porcine corneas ex ...

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    7. Clinical Corneal Optical Coherence Elastography Measurement Precision: Effect of Heartbeat and Respiration

      Clinical Corneal Optical Coherence Elastography Measurement Precision: Effect of Heartbeat and Respiration

      Purpose : Normal physiological movements (e.g., respiration and heartbeat) induce eye motions during clinical measurements of human corneal biomechanical properties using optical coherence elastography (OCE). We quantified the effects of respiratory and cardiac-induced eye motions on clinical corneal OCE measurement precision and repeatability. Methods : Corneal OCE was performed using low-force, micro-air-pulse tissue stimulation and high-resolution phase-sensitive optical coherence tomography (OCT) imaging. Axial surface displacements of the corneal apex were measured (M-mode) at a 70-kHz sampling rate and three different stimulation pressures (20–60 Pa). Simultaneously, the axial corneal position was tracked with structural OCT imaging, while the heartrate and respiration ...

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    8. Multimodal quantitative optical elastography of the crystalline lens with optical coherence elastography and Brillouin microscopy

      Multimodal quantitative optical elastography of the crystalline lens with optical coherence elastography and Brillouin microscopy

      Assessing the biomechanical properties of the crystalline lens can provide crucial information for diagnosing disease and guiding precision therapeutic interventions. Existing noninvasive methods have been limited to global measurements. Here, we demonstrate the quantitative assessment of the elasticity of crystalline lens with a multimodal optical elastography technique, which combines dynamic wave-based optical coherence elastography (OCE) and Brillouin microscopy to overcome the drawbacks of individual modalities. OCE can provide direct measurements of tissue elasticity rapidly and quantitatively, but it is a challenge to image transparent samples such as the lens because this technique relies on backscattered light. On the other hand ...

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    9. Laser-induced elastic wave classification: thermoelastic versus ablative regimes for all-optical elastography applications

      Laser-induced elastic wave classification: thermoelastic versus ablative regimes for all-optical elastography applications

      Significance : Shear wave optical coherence elastography is an emerging technique for characterizing tissue biomechanics that relies on the generation of elastic waves to obtain the mechanical contrast. Various techniques, such as contact, acoustic, and pneumatic methods, have been used to induce elastic waves. However, the lack of higher-frequency components within the elastic wave restricts their use in thin samples. The methods also require moving parts and/or tubing, which therefore limits the extent to which they can be miniaturized. Aim : To overcome these limitations, we propose an all-optical approach using photothermal excitation. Depending on the absorption coefficient of the sample ...

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    10. Recent progress in optical probing and manipulation of tissue: introduction

      Recent progress in optical probing and manipulation of tissue: introduction

      This feature issue of Biomedical Optics Express represents a cross-section of the most recent work in tissue optics, including exciting developments in tissue optical clearing, deep tissue imaging, optical elastography, nanophotonics in tissue, and therapeutic applications of light, amongst others. A collection of 33 papers provides a comprehensive overview of current research in tissue optics, much of it inspired and informed by the pioneering work of Prof. Valery Tuchin. The issue contains three invited manuscripts and several mini-reviews that we hope will benefit researchers in this exciting area.

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    11. Assessing the Acute Effects of Prenatal Synthetic Cannabinoid Exposure on Murine Fetal Brain Vasculature Using Optical Coherence Tomography

      Assessing the Acute Effects of Prenatal Synthetic Cannabinoid Exposure on Murine Fetal Brain Vasculature Using Optical Coherence Tomography

      Marijuana is one of the most commonly abused substances during pregnancy. Synthetic cannabinoids (SCBs) are a group of heterogeneous compounds that are 40‐ to 600‐fold more potent than ∆ 9 ‐tetrahydrocannabinol , the major psychoactive component of marijuana. With SCBs being legally available for purchase and the prevalence of unplanned pregnancies, the possibility of prenatal exposure to SCBs is high. However, the effects of prenatal SCB exposure on embryonic brain development are not well understood. In this study, we use complex correlation mapping optical coherence angiography to evaluate changes in murine fetal brain vasculature in utero , minutes after maternal exposure to ...

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    12. Optical coherence elastography of cold cataract in porcine lens

      Optical coherence elastography of cold cataract in porcine lens

      Cataract is one of the most prevalent causes of blindness around the world. Understanding the mechanisms of cataract development and progression is important for clinical diagnosis and treatment. Cold cataract has proven to be a robust model for cataract formation that can be easily controlled in the laboratory. There is evidence that the biomechanical properties of the lens can be significantly changed by cataract. Therefore, early detection of cataract, as well as evaluation of therapies, could be guided by characterization of lenticular biomechanical properties. In this work, we utilized optical coherence elastography (OCE) to monitor the changes in biomechanical properties ...

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    13. Assessing the biomechanical properties of the porcine crystalline lens as a function of intraocular pressure with optical coherence elastography

      Assessing the biomechanical properties of the porcine crystalline lens as a function of intraocular pressure with optical coherence elastography

      In this study, we investigated the relationship between the biomechanical properties of the crystalline lens and intraocular pressure (IOP) using a confocal acoustic radiation force (ARF) and phase-sensitive optical coherence elastography (OCE) system. ARF induced a small displacement at the apex of porcine lenses in situ at various artificially controlled IOPs. Maximum displacement, relaxation rate, and Young’s modulus were utilized to assess the stiffness of the crystalline lens. The results showed that the stiffness of the crystalline increased as IOP increased, but the lens stiffening was not as significant as the stiffening of other ocular tissues such as the ...

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    14. Integrated optical coherence tomography and multielement ultrasound transducer probe for shear wave elasticity imaging of moving tissues

      Integrated optical coherence tomography and multielement ultrasound transducer probe for shear wave elasticity imaging of moving tissues

      Accurate measurements of microelastic properties of soft tissues in-vivo using optical coherence elastography can be affected by motion artifacts caused by cardiac and respiratory cycles. This problem can be overcome using a multielement ultrasound transducer probe where each ultrasound transducer is capable of generating acoustic radiation force (ARF) and, therefore, creating shear waves in tissue. These shear waves, produced during the phase of cardiac and respiratory cycles when tissues are effectively stationary, are detected at the same observation point using phase-sensitive optical coherence tomography (psOCT). Given the known distance between the ultrasound transducers, the speed of shear wave propagation can ...

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    15. Modified wavelength scanning interferometry for simultaneous tomography and topography of the cornea with Fourier domain optical coherence tomography

      Modified wavelength scanning interferometry for simultaneous tomography and topography of the cornea with Fourier domain optical coherence tomography

      Visual acuity is dependent on corneal shape and size. A minor variation in surface geometry can cause a deformation of corneal geometry, which affects its optical performance. In this work we demonstrate an algorithm for the simultaneous measurement of corneal tomography and topography with a traditional point-scanning Fourier domain optical coherence tomography (FD-OCT) system. A modified wavelength scanning interferometry (mWSI) algorithm enabled topographical evaluation of the surface with nanometer-scale resolution, which is superior to the micrometer-scale resolution of traditional OCT structural imaging. We validated the technique with an optically flat mirror, standard roughness gauges, and atomic force microscopy (AFM). The ...

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    16. Quantifying the effects of hydration on corneal stiffness with noncontact optical coherence elastography

      Quantifying the effects of hydration on corneal stiffness with noncontact optical coherence elastography

      Purpose To quantify the effects of the hydration state on the Young's modulus of the cornea . Setting Biomedical Optics Laboratory, University of Houston, Houston, Texas, USA. Design Experimental study. Methods Noncontact, dynamic optical coherence elastography (OCE) measurements were taken of in situ rabbit corneas in the whole eye–globe configuration (n = 10) and at an artificially controlled intraocular pressure of 15 mm Hg. Baseline OCE measurements were taken by topically hydrating the corneas with saline for 1 hour. The corneas were then dehydrated topically with a 20% dextran solution for another hour, and the OCE measurements were repeated. A ...

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    17. Effects of Thickness on Corneal Biomechanical Properties Using Optical Coherence Elastography

      Effects of Thickness on Corneal Biomechanical Properties Using Optical Coherence Elastography

      SIGNIFICANCE Measured corneal biomechanical properties are driven by intraocular pressure, tissue thickness, and inherent material properties. We demonstrate tissue thickness as an important factor in the measurement of corneal biomechanics that can confound short-term effects due to UV riboflavin cross-linking (CXL) treatment. PURPOSE We isolate the effects of tissue thickness on the measured corneal biomechanical properties using optical coherence elastography by experimentally altering the tissue hydration state and stiffness. METHODS Dynamic optical coherence elastography was performed using phase-sensitive optical coherence tomography imaging to quantify the tissue deformation dynamics resulting from a spatially discrete, low-force air pulse (150-μm spot size ...

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    18. Quantifying changes in lens biomechanical properties due to cold cataract with optical coherence elastography

      Quantifying changes in lens biomechanical properties due to cold cataract with optical coherence elastography

      Cataract is the most prevalent cause of visual impairment worldwide. Cataracts can be formed due to trauma, radiation, drug abuse, or low temperatures. Thus, early detection of cataract can be immensely helpful for preserving visual acuity by ensuring that the appropriate therapeutic procedures are performed at earlier stages of disease onset and progression. In this work, we utilized a phase-sensitive optical coherence elastography (OCE) system to quantify changes in biomechanical properties of porcine lenses in vitro with induced cold cataracts. The results show significant increase in lens Young’s modulus due to formation of the cold cataract (from ~ 35 kPa ...

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    19. Biomechanical assessment of myocardial infarction using optical coherence elastography

      Biomechanical assessment of myocardial infarction using optical coherence elastography

      Myocardial infarction (MI) leads to cardiomyocyte loss, impaired cardiac function, and heart failure. Molecular genetic analyses of myocardium in mouse models of ischemic heart disease have provided great insight into the mechanisms of heart regeneration, which is promising for novel therapies after MI. Although biomechanical factors are considered an important aspect in cardiomyocyte proliferation, there are limited methods for mechanical assessment of the heart in the mouse MI model. This prevents further understanding the role of tissue biomechanics in cardiac regeneration. Here we report optical coherence elastography (OCE) of the mouse heart after MI. Surgical ligation of the left anterior ...

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    20. Evaluating the Effects of Maternal Alcohol Consumption on Murine Fetal Brain Vasculature Using Optical Coherence Tomography

      Evaluating the Effects of Maternal Alcohol Consumption on Murine Fetal Brain Vasculature Using Optical Coherence Tomography

      Prenatal alcohol exposure (PAE) can result in a range of anomalies including brain and behavioral dysfunctions, collectively termed fetal alcohol spectrum disorder (FASD). PAE during the 1 st and 2 nd trimester is common, and research in animal models has documented significant neural developmental deficits associated with PAE during this period. However, little is known about the immediate effects of PAE on fetal brain vasculature. In this study, we used in utero speckle variance optical coherence tomography (SVOCT), a high spatial- and temporal–resolution imaging modality, to evaluate dynamic changes in micro-vasculature of the 2 nd trimester-equivalent murine fetal brain ...

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    21. Common-path phase-sensitive optical coherence tomography provides enhanced phase stability and detection sensitivity for dynamic elastography

      Common-path phase-sensitive optical coherence tomography provides enhanced phase stability and detection sensitivity for dynamic elastography

      Phase-sensitive optical coherence elastography (PhS-OCE) is an emerging optical technique to quantify soft-tissue biomechanical properties. We implemented a common-path OCT design to enhance displacement sensitivity and optical phase stability for dynamic elastography imaging. The background phase stability was greater in common-path PhS-OCE (0.24 ± 0.07nm) than conventional PhS-OCE (1.60 ± 0.11μm). The coefficient of variation for surface displacement measurements using conventional PhS-OCE averaged 11% versus 2% for common-path PhS-OCE. Young’s modulus estimates showed good precision (95% CIs) for tissue phantoms: 24.96 ± 2.18kPa (1% agar), 49.69 ± 4.87kPa (1.5% agar), and 116.08 ...

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    22. Comparison and combination of rotational imaging optical coherence tomography and selective plane illumination microscopy for embryonic study

      Comparison and combination of rotational imaging optical coherence tomography and selective plane illumination microscopy for embryonic study

      Several optical imaging techniques have been applied for high-resolution embryonic imaging using different contrast mechanisms, each with their own benefits and limitations. In this study, we imaged the same E9.5 mouse embryo with rotational imaging optical coherence tomography (RI-OCT) and selective plane illumination microscopy (SPIM). RI-OCT overcomes optical penetration limits of traditional OCT imaging that prohibit full-body imaging of mouse embryos at later stages by imaging the samples from multiple angles. SPIM enables high-resolution, 3D imaging with less phototoxicity and photobleaching than laser scanning confocal microscopy (LSCM) by illuminating the sample with a focused sheet of light. Side by ...

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    23. Evaluating biomechanical properties of murine embryos using Brillouin microscopy and optical coherence tomography

      Evaluating biomechanical properties of murine embryos using Brillouin microscopy and optical coherence tomography

      Embryogenesis is regulated by numerous changes in mechanical properties of the cellular microenvironment. Thus, studying embryonic mechanophysiology can provide a more thorough perspective of embryonic development, potentially improving early detection of congenital abnormalities as well as evaluating and developing therapeutic interventions. A number of methods and techniques have been used to study cellular biomechanical properties during embryogenesis. While some of these techniques are invasive or involve the use of external agents, others are compromised in terms of spatial and temporal resolutions. We propose the use of Brillouin microscopy in combination with optical coherence tomography (OCT) to measure stiffness as well ...

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    24. Quantifying the effects of UV-A/riboflavin crosslinking on the elastic anisotropy and hysteresis of the porcine cornea by noncontact optical coherence elastography

      Quantifying the effects of UV-A/riboflavin crosslinking on the elastic anisotropy and hysteresis of the porcine cornea by noncontact optical coherence elastography

      The collagen fibril orientation of the cornea can provide critical information about cornea tissue health because diseases such as keratoconus and therapeutic interventions such as UV-A/riboflavin corneal collagen crosslinking (CXL) can alter the ultrastructural arrangement of collagen fibrils. Here, we quantify the elastic anisotropy and hysteresis of in situ porcine corneas as a function of intraocular pressure (IOP) with noncontact optical coherence elastography. Moreover, the effects of UV-A riboflavin corneal collagen crosslinking on the elastic anisotropy and hysteresis were evaluated. The propagation of an air-pulse induced elastic wave was imaged at stepped meridional angles by a home built phasestabilized ...

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    1-24 of 137 1 2 3 4 5 6 »
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    1. (137 articles) Kirill V. Larin
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    Assessing molecular diffusion in tissues using optical coherence tomography Live imaging of blood flow in mammalian embryos using Doppler swept-source optical coherence tomography Hemodynamic measurements from individual blood cells in early mammalian embryos with Doppler swept source OCT Imaging of mouse embryonic eye development using optical coherence tomography Postdoctoral Position in Optical Coherence Tomography / Optical Coherence Elastography at University of Houston EARLY SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY BIOMARKERS TO CONFIRM FELLOW EYE CHANGES IN ASYMMETRIC TYPE-2 MACULAR TELANGIECTASIA Relative Postpartum Retinal Vasoconstriction Detected With Optical Coherence Tomography Angiography 1.1 μm waveband tunable laser using emission-wavelength-controlled InAs quantum dots for swept-source optical coherence tomography applications Retinal nerve fibre layer and peripapillary vascular density by optical coherence tomography angiography in schizophrenia Livelayer: A Semi-Automatic Software Program for Segmentation of Layers and Diabetic Macular Edema in Optical Coherence Tomography Images Long-term progression of myopic maculopathy in degenerative myopia as imaged by SD-OCT and IR imaging Postdoctoral Research Fellowship position  in the Center for Ophthalmic Optics and Lasers, Casey Eye Institute, Oregon Health & Science University