1. Articles from Wang-Yuhl Oh

    1-24 of 27 1 2 »
    1. 9.4 MHz A-line rate optical coherence tomography at 1300 nm using a wavelength-swept laser based on stretched-pulse active mode-locking

      9.4 MHz A-line rate optical coherence tomography at 1300 nm using a wavelength-swept laser based on stretched-pulse active mode-locking

      In optical coherence tomography (OCT), high-speed systems based at 1300 nm are among the most broadly used. Here, we present 9.4 MHz A-line rate OCT system at 1300 nm. A wavelength-swept laser based on stretched-pulse active mode locking (SPML) provides a continuous and linear-in-wavenumber sweep from 1240 nm to 1340 nm, and the OCT system using this light source provides a sensitivity of 98 dB and a single-sided 6-dB roll-off depth of 2.5 mm. We present new capabilities of the 9.4 MHz SPML-OCT system in three microscopy applications. First, we demonstrate high quality OCTA imaging at a ...

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    2. Retinal Blood Vessel Caliber Estimation for Optical Coherence Tomography Angiography Images Based on 3D Superellipsoid Modeling

      Retinal Blood Vessel Caliber Estimation for Optical Coherence Tomography Angiography Images Based on 3D Superellipsoid Modeling

      Changes of retinal blood vessel calibers may reflect various retinal diseases and even several non-retinal diseases. We propose a new method to estimate retinal vessel calibers from 3D optical coherence tomography angiography (OCTA) images based on 3D modeling using superellipsoids. Taking advantage of 3D visualization of the retinal tissue microstructures in vivo provided by OCTA, our method can detect retinal blood vessels precisely, estimate their calibers reliably, and show the relative flow speed visually.

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    3. Tie2 activation promotes choriocapillary regeneration for alleviating neovascular age-related macular degeneration

      Tie2 activation promotes choriocapillary regeneration for alleviating neovascular age-related macular degeneration

      Choriocapillary loss is a major cause of neovascular age-related macular degeneration (NV-AMD). Although vascular endothelial growth factor (VEGF) blockade for NV-AMD has shown beneficial outcomes, unmet medical needs for patients refractory or tachyphylactic to anti-VEGF therapy exist. In addition, the treatment could exacerbate choriocapillary rarefaction, necessitating advanced treatment for fundamental recovery from NV-AMD. In this study, Tie2 activation by angiopoietin-2–binding and Tie2-activating antibody (ABTAA) presents a therapeutic strategy for NV-AMD. Conditional Tie2 deletion impeded choriocapillary maintenance, rendering eyes susceptible to NV-AMD development. Moreover, in a NV-AMD mouse model, ABTAA not only suppressed choroidal neovascularization (CNV) and vascular leakage but ...

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    4. Comprehensive intravascular imaging of atherosclerotic plaque in vivo using optical coherence tomography and fluorescence lifetime imaging

      Comprehensive intravascular imaging of atherosclerotic plaque in vivo using optical coherence tomography and fluorescence lifetime imaging

      Comprehensive imaging of both the structural and biochemical characteristics of atherosclerotic plaque is essential for the diagnosis and study of coronary artery disease because both a plaque’s morphology and its biochemical composition affect the level of risk it poses. Optical coherence tomography (OCT) and fluorescence lifetime imaging (FLIm) are promising optical imaging methods for characterizing coronary artery plaques morphologically and biochemically, respectively. In this study, we present a hybrid intravascular imaging device, including a custom-built OCT/FLIm system, a hybrid optical rotary joint, and an imaging catheter, to visualize the structure and biochemical composition of the plaque in an ...

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    5. Wide dynamic range high-speed three-dimensional quantitative OCT angiography with a hybrid-beam scan

      Wide dynamic range high-speed three-dimensional quantitative OCT angiography with a hybrid-beam scan

      We demonstrate a novel hybrid-beam scanning-based quantitative optical coherence tomography angiography (OCTA) that provides high-speed wide dynamic range blood flow speed imaging. The hybrid-beam scanning scheme enables multiple OCTA image acquisitions with a wide range of multiple time intervals simultaneously providing wide dynamic range blood flow speed imaging independent of the blood vessel orientation, which was quantified over a speed range of 0.6 ∼ 104    mm / s 0.6∼104  mm/s through the blood flow phantom experiments. A fully automated high-speed hybrid-beam scanning-based quantitative OCTA system demonstrates visualization of blood flow speeds in various vessels from the main arteries ...

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    6. Multispectral analog-mean-delay fluorescence lifetime imaging combined with optical coherence tomography

      Multispectral analog-mean-delay fluorescence lifetime imaging combined with optical coherence tomography

      The pathophysiological progression of chronic diseases, including atherosclerosis and cancer, is closely related to compositional changes in biological tissues containing endogenous fluorophores such as collagen, elastin, and NADH, which exhibit strong autofluorescence under ultraviolet excitation. Fluorescence lifetime imaging (FLIm) provides robust detection of the compositional changes by measuring fluorescence lifetime, which is an inherent property of a fluorophore. In this paper, we present a dual-modality system combining a multispectral analog-mean-delay (AMD) FLIm and a high-speed swept-source optical coherence tomography (OCT) to simultaneously visualize the cross-sectional morphology and biochemical compositional information of a biological tissue. Experiments using standard fluorescent solutions showed ...

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    7. Comparison of Accuracy of One Use Methods for Calculating Fractional Flow Reserve by Intravascular Optical Coherence Tomography to That Determined by the Pressure-Wire Method

      Comparison of Accuracy of One Use Methods for Calculating Fractional Flow Reserve by Intravascular Optical Coherence Tomography to That Determined by the Pressure-Wire Method

      While identification of hemodynamic significance of coronary lesions becomes important for revascularization strategy, the potential role of three-dimensional high-resolution intracoronary Optical coherence tomography (OCT) for predicting functional significance of coronary lesions remains unclear. We assessed the diagnostic performance of two computational approaches for deriving fractional flow reserve (FFR) from intravascular OCT images. We developed two methods to derive FFR from volumetric OCT images by applying analytical fluid dynamics (FFR-OCTAFD) and computational fluid dynamics (FFR-OCTCFD). Among 217 eligible patients between 2011 and 2014, total 104 patients were included for data analysis (9 for derivation, 95 for validation). Luminal geometries from three-dimensional ...

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    8. Intravascular optical coherence tomography [Invited]

      Intravascular optical coherence tomography [Invited]

      Shortly after the first demonstration of optical coherence tomography for imaging the microstructure of the human eye, work began on developing systems and catheters suitable for intravascular imaging in order to diagnose and investigate atherosclerosis and potentially to monitor therapy. This review covers the driving considerations of the clinical application and its constraints, the major engineering milestones that enabled the current, high-performance commercial imaging systems, the key studies that laid the groundwork for image interpretation, and the clinical research that traces intravascular optical coherence tomography (OCT) from early human pilot studies to current clinical trials.

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    9. Single cardiac cycle three-dimensional intracoronary optical coherence tomography

      Single cardiac cycle three-dimensional intracoronary optical coherence tomography

      While high-speed intracoronary optical coherence tomography (OCT) provides three-dimensional (3D) visualization of coronary arteries in vivo , imaging speeds remain insufficient to avoid motion artifacts induced by heartbeat, limiting the clinical utility of OCT. In this paper, we demonstrate development of a high-speed intracoronary OCT system (frame rate: 500 frames/s, pullback speed: 100 mm/s) along with prospective electrocardiogram (ECG) triggering technology, which enabled volumetric imaging of long coronary segments within a single cardiac cycle (70 mm pullback in 0.7 s) with minimal cardiac motion artifact. This technology permitted detailed visualization of 3D architecture of the coronary arterial wall ...

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    10. Imaging Laser-Induced Choroidal Neovascularization in the Rodent Retina Using Optical Coherence Tomography Angiography

      Imaging Laser-Induced Choroidal Neovascularization in the Rodent Retina Using Optical Coherence Tomography Angiography

      Purpose : The purpose of this study was to evaluate the performance of optical coherence tomography angiography (OCTA) in visualizing laser-induced choroidal neovascularization (CNV) in the rodent retina. Methods : Choroidal neovascularization was induced via laser photocoagulation in 2 male Brown Norway rats and 2 male C57BL/6 mice. For qualitative comparison, the animals were imaged in vivo with OCTA, indocyanine green angiography (ICGA), and fluorescein angiography (FA), and ex vivo with immunofluorescence confocal microscopy, 14 days post laser photocoagulation without anti-vascular endothelial growth factor (anti-VEGF) intervention. For longitudinal quantitative analysis, CNV was induced in 6 additional male C57BL/6 mice. Three ...

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    11. Characterization of lipid-rich plaques using spectroscopic optical coherence tomography

      Characterization of lipid-rich plaques using spectroscopic optical coherence tomography

      Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the internal structures of walls of coronary arteries in vivo . However, accurate characterization of atherosclerotic plaques with gray-scale IV-OCT images is often limited by various intrinsic artifacts. In this study, we present an algorithm for characterizing lipid-rich plaques with a spectroscopic OCT technique based on a Gaussian center of mass (GCOM) metric. The GCOM metric, which reflects the absorbance properties of lipids, was validated using a lipid phantom. In addition, the proposed characterization method was successfully demonstrated in vivo using an atherosclerotic rabbit model and was found ...

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    12. Intracoronary dual-modal optical coherence tomography-near-infrared fluorescence structural–molecular imaging with a clinical dose of indocyanine green for the assessment of high-risk plaques and stent-associated inflammation in a beating coronary artery

      Intracoronary dual-modal optical coherence tomography-near-infrared fluorescence structural–molecular imaging with a clinical dose of indocyanine green for the assessment of high-risk plaques and stent-associated inflammation in a beating coronary artery

      Aims Inflammation plays essential role in development of plaque disruption and coronary stent-associated complications. This study aimed to examine whether intracoronary dual-modal optical coherence tomography (OCT)-near-infrared fluorescence (NIRF) structural–molecular imaging with indocyanine green (ICG) can estimate inflammation in swine coronary artery. Methods and results After administration of clinically approved NIRF-enhancing ICG (2.0 mg/kg) or saline, rapid coronary imaging (20 mm/s pullback speed) using a fully integrated OCT-NIRF catheter was safely performed in 12 atheromatous Yucatan minipigs and in 7 drug-eluting stent (DES)-implanted Yorkshire pigs. Stronger NIRF activity was identified in OCT-proven high-risk plaque compared ...

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    13. GPU-Accelerated Framework for Intracoronary Optical Coherence Tomography Imaging at the Push of a Button

      GPU-Accelerated Framework for Intracoronary Optical Coherence Tomography Imaging at the Push of a Button

      Frequency domain optical coherence tomography (FD-OCT) has become one of the important clinical tools for intracoronary imaging to diagnose and monitor coronary artery disease, which has been one of the leading causes of death. To help more accurate diagnosis and monitoring of the disease, many researchers have recently worked on visualization of various coronary microscopic features including stent struts by constructing three-dimensional (3D) volumetric rendering from series of cross-sectional intracoronary FD-OCT images. In this paper, we present the first, to our knowledge, "push-of-a-button" graphics processing unit (GPU)-accelerated framework for intracoronary OCT imaging. Our framework visualizes 3D microstructures of the ...

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    14. Multi-functional angiographic OFDI using frequency-multiplexed dual-beam illumination

      Multi-functional angiographic OFDI using frequency-multiplexed dual-beam illumination

      Detection of blood flow inside the tissue sample can be achieved by measuring the local change of complex signal over time in angiographic optical coherence tomography (OCT). In conventional angiographic OCT, the transverse displacement of the imaging beam during the time interval between a pair of OCT signal measurements must be significantly reduced to minimize the noise due to the beam scanning-induced phase decorrelation at the expense of the imaging speed. Recent introduction of dual-beam scan method either using polarization encoding or two identical imaging systems in spectral-domain (SD) OCT scheme shows potential for high-sensitivity vasculature imaging without suffering from ...

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    15. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging

      All-fiber wavelength swept ring laser based on  Fabry-Perot filter for optical frequency domain  imaging

      Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral ...

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    16. Feature Of The Week 8/31/14: Fully Integrated High-speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo using a Clinically-available NIRF Emitting Indocyanine Green to Detect Inflamed Lipid-rich Atheromata in Coronary-sized Vessels

      Feature Of The Week 8/31/14: Fully Integrated High-speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo using a Clinically-available NIRF Emitting Indocyanine Green to Detect Inflamed Lipid-rich Atheromata in Coronary-sized Vessels

      In current study, we fully integrated near-infrared fluorescence (NIRF) molecular imaging into intravascular OCT structural imaging. The OCT/NIRF single catheter imaging clearly demonstrated the microstructure of atheromata and simultaneously identified ICG-enhancing macrophage abundant lipid-rich areas of the plaques. Ex vivo NIRF imaging evidently validated in vivo OCT-NIRF imaging. NIRF signals on ex vivo fluorescence reflectance imaging colocalized well with in vivo NIRF imaging. In vitro ICG cell uptake, correlative fluorescence microscopy, and histopathology corroborated the in vivo imaging findings. Herein, our research team have solved the issues critical for application of this OCT/NIRF imaging technology to clinical practice ...

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    17. Fully Integrated High-Speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo Using a Clinically Available Near-Infrared Fluorescence–Emitting Indocyanine Green to Detect Inflamed Lipid-Rich Atheromata in Coronary-Sized Vessels

      Fully Integrated High-Speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo Using a Clinically Available Near-Infrared Fluorescence–Emitting Indocyanine Green to Detect Inflamed Lipid-Rich Atheromata in Coronary-Sized Vessels

      Background— Lipid-rich inflamed coronary plaques a reprone to rupture. The purpose of this study was to assess lipid-rich inflamed plaques invivo using fully integrated high-speed optical coherence tomography (OCT)/ near-infrared fluorescence (NIRF) molecular imaging with a Food and Drug Administration– a pproved indocyanine green (ICG). Methods a nd Results— A n integrated high-speed intravascular OCT/NIRF imaging c a theter a nd a du a l-mod a l OCT/NIRF system were constructed b a sed on a cl in ic a l OCT pl a tform. For imaging lipid-rich inflamed plaques, the Food and Drug Administration– approved NIRF-emitting ICG ...

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    18. High frame-rate intravascular optical frequency-domain imaging in vivo

      High frame-rate intravascular optical frequency-domain imaging in vivo

      Intravascular optical frequency-domain imaging (OFDI), a second-generation optical coherence tomography (OCT) technology, enables imaging of the three-dimensional (3D) microstructure of the vessel wall following a short and nonocclusive clear liquid flush. Although 3D vascular visualization provides a greater appreciation of the vessel wall and intraluminal structures, a longitudinal imaging pitch that is several times bigger than the optical imaging resolution of the system has limited true high-resolution 3D imaging, mainly due to the slow scanning speed of previous imaging catheters. Here, we demonstrate high frame-rate intravascular OFDI in vivo, acquiring images at a rate of 350 frames per second. A ...

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    19. Spectral binning for mitigation of polarization mode dispersion artifacts in catheter-based optical frequency domain imaging

      Spectral binning for mitigation of polarization mode dispersion artifacts in catheter-based optical frequency domain imaging

      Polarization mode dispersion (PMD) has been recognized as a significant barrier to sensitive and reproducible birefringence measurements with fiber-based, polarization-sensitive optical coherence tomography systems. Here, we present a signal processing strategy that reconstructs the local retardation robustly in the presence of system PMD. The algorithm uses a spectral binning approach to limit the detrimental impact of system PMD and benefits from the final averaging of the PMD-corrected retardation vectors of the spectral bins. The algorithm was validated with numerical simulations and experimental measurements of a rubber phantom. When applied to the imaging of human cadaveric coronary arteries, the algorithm was ...

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    20. Artifacts in polarization-sensitive optical coherence tomography caused by polarization mode dispersion

      Artifacts in polarization-sensitive optical coherence tomography caused by polarization mode dispersion

      Polarization mode dispersion (PMD) severely degrades images of biological tissue measured with polarization-sensitive optical coherence tomography. It adds a bias to the local retardation value that can be spatially confined, resulting in regions of seemingly high sample birefringence that are purely artificial. Here, we demonstrate and analyze this effect, both experimentally and with numerical simulations, and show that artifacts can be avoided by limiting the system PMD to less than the system axial resolution. Even then, spatial averaging over a dimension larger than that characteristic of speckle is required to remove a PMD-induced bias of the local retardation values.

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    21. Feature Of The Week 3/3/13: Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography

      Feature Of The Week 3/3/13: Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography

      We present that a novel wavefront shaping approach improves the penetration depth and sensitivity of optical coherence tomography (OCT) by systematically control multiple light scattering. As well known, the penetration depth of OCT is significantly limited due to multiple light scattering that is resulted from refractive inhomogeneity. Whereas OCT can achieve satisfactory penetration depth in ophthalmology where the tissue structures are relatively transparent (weakly turbid), the limited penetration depth of OCT prevents general applications to other highly turbid opaque tissues such as skin tissue. Conventional approaches to attempt to solve this issue in OCT have revealed challenges in dealing with ...

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    22. Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography

      Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography

      We report on an approach to exploit multiple light scattering by shaping the incident wavefront in optical coherence tomography (OCT). Most of the reflected signal from biological tissue consists of multiply scattered light, which is regarded as noise in OCT. A digital mirror device (DMD) is utilized to shape the incident wavefront such that the maximal energy is focused at a specific depth in a highly scattering sample using a coherence-gated reflectance signal as feedback. The proof-of-concept experiment demonstrates that this approach enhances depth-selective focusing in the presence of optical inhomogeneity, and thus extends the penetration depth in spectral domain-OCT ...

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    23. Numerical compensation of system polarization mode dispersion in polarization-sensitive optical coherence tomography

      Numerical compensation of system polarization mode dispersion in polarization-sensitive optical coherence tomography

      Polarization mode dispersion (PMD), which can be induced by circulators or even moderate lengths of optical fiber, is known to be a dominant source of instrumentation noise in fiber-based PS-OCT systems. In this paper we propose a novel PMD compensation method that measures system PMD using three fixed calibration signals, numerically corrects for these instrument effects and reconstructs an improved sample image. Using a frequency multiplexed PS-OFDI setup, we validate the proposed method by comparing birefringence noise in images of intralipid, muscle, and tendon with and without PMD compensation.

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    24. >400 kHz repetition rate wavelength-swept laser and application to high-speed optical frequency domain imaging

      >400 kHz repetition rate wavelength-swept laser and application to high-speed optical frequency domain imaging
      We demonstrate a high-speed wavelength-swept laser with a tuning range of 104nm (1228–1332nm) and a repetition rate of 403kHz. The design of the laser utilizes a high-finesse polygon-based wavelength-scanning filter and a short-length unidirectional ring resonator. Optical frequency domain imaging of the human skin in vivo is presented using this laser, and the system shows sensitivity of higher than 98dB with single-side ranging depth of 1.7mm over 4dB sensitivity roll-off.
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    1-24 of 27 1 2 »
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    1. (27 articles) Wang Yuhl Oh
    2. (22 articles) Korea Advanced Institute of Science and Technology
    3. (16 articles) Harvard University
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    Performance of reduced bit-depth acquisition for optical frequency domain imaging Progress in Intracoronary Optical Coherence Tomography >400 kHz repetition rate wavelength-swept laser and application to high-speed optical frequency domain imaging Comprehensive esophageal microscopy by using optical frequency–domain imaging (with video) Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography Feature Of The Week 3/3/13: Complex wavefront shaping for optimal depth-selective focusing in optical coherence tomography Artifacts in polarization-sensitive optical coherence tomography caused by polarization mode dispersion Fully Integrated High-Speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo Using a Clinically Available Near-Infrared Fluorescence–Emitting Indocyanine Green to Detect Inflamed Lipid-Rich Atheromata in Coronary-Sized Vessels Feature Of The Week 8/31/14: Fully Integrated High-speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo using a Clinically-available NIRF Emitting Indocyanine Green to Detect Inflamed Lipid-rich Atheromata in Coronary-sized Vessels All-fiber wavelength swept ring laser based on  Fabry-Perot filter for optical frequency domain  imaging Correlation of retinal sensitivity in microperimetry with vascular density in optical coherence tomography angiography in primary open-angle glaucoma Normal Reference Ranges of Optical Coherence Tomography Parameters in Children