1. Articles from Dae Yu Kim

    1-25 of 25
    1. Comparison of light absorption levels with different skin phantoms and the Monte Carlo simulation using Fourier-domain optical coherence tomography

      Comparison of light absorption levels with different skin phantoms and the Monte Carlo simulation using Fourier-domain optical coherence tomography

      Dermatologic patients have various skin characteristics such as skin tone and pigmentation color. However most studies on laser ablation and treatment only considered laser operating conditions like wavelength, output power and pulse duration. The laser ablation arises from photothermal effect by photon energy absorption. Chromophores like melanin exist as the absorber in the skin. In this study, we painted color to mimic chromophores on in-vivo and in-vitro skin models to demonstrate influence on the laser ablation by skin color. Water-based pens were used to paint color. Cross sectional images of the laser ablation were acquired by Fourier-domain optical coherence tomography ...

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      Mentions: Dae Yu Kim
    2. Phase-Variance Optical Coherence Tomographic Angiography Imaging of Choroidal Perfusion Changes Associated With Acute Posterior Multifocal Placoid Pigment Epitheliopathy

      Phase-Variance Optical Coherence Tomographic Angiography Imaging of Choroidal Perfusion Changes Associated With Acute Posterior Multifocal Placoid Pigment Epitheliopathy

      This case report uses phase-variance optical coherence tomographic angiography to demonstrate transient inner choroidal flow changes associated with acute posterior multifocal placoid pigment epitheliopathy. Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) is characterized by bilateral multiple placoid white-gray lesions of the posterior pole at the level of the retinal pigment epithelium (RPE) and/or choriocapillaris, which self-resolve with recovery of vision. 1 , 2 The etiology is unknown, but APMPPE has been associated with viral prodromes and vasculitis. The placoid lesions are thought to represent focal RPE inflammation or choriocapillaris ischemia based on fluorescein angiogram findings of early hypofluorescence and late ...

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    3. Enhanced Tissue Ablation Efficiency with a Mid-Infrared Nonlinear Frequency Conversion Laser System and Tissue Interaction Monitoring Using Optical Coherence Tomography

      Enhanced Tissue Ablation Efficiency with a Mid-Infrared Nonlinear Frequency Conversion Laser System and Tissue Interaction Monitoring Using Optical Coherence Tomography

      We report development of optical parametric oscillator (OPO)-based mid-infrared laser system that utilizes a periodically poled nonlinear crystal pumped by a near-infrared (NIR) laser. We obtained a mid-infrared average output of 8 W at an injection current of 20 A from a quasi-phase-matched OPO using an external cavity configuration. Laser tissue ablation efficiency is substantially affected by several parameters, including an optical fluence rate, wavelength of the laser source, and the optical properties of target tissue. Dimensions of wavelength and radiant exposure dependent tissue ablation are quantified using Fourier domain optical coherence tomography and the ablation efficiency was compared ...

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      Mentions: Dae Yu Kim
    4. Development of 2-micron nonlinear frequency conversion laser system and tissue interaction monitoring using optical coherence tomography

      Development of 2-micron nonlinear frequency conversion laser system and tissue interaction monitoring using optical coherence tomography

      We report on development of optical parametric oscillator (OPO) based mid-infrared laser system, which utilizes periodically poled nonlinear crystal that was pumped by near-infrared (NIR) laser. We have obtained 8 W of mid-infrared average output at the injection current of 20A from a quasi-phase-matched OPO using external cavity configuration. The laser tissue ablation efficiency was investigated which is substantially affected by several parameters such as, optical fluence rate, wavelength of the laser source and the optical properties of target tissue. Wavelength and radiant exposure dependent tissue ablation dimension were quantified by using SD-OCT (spectral domain optical coherence tomography) and the ...

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      Mentions: Dae Yu Kim
    5. Detection of PED vascularization using phase-variance OCT angiography

      Detection of PED vascularization using phase-variance OCT angiography

      Purpose: To demonstrate the use of phase-variance optical coherence tomography (PV-OCT) angiography for detection of pigment epithelial detachment (PED) vascularization in age-related macular degeneration (AMD). Patients and methods: Patients with PEDs and exudative AMD were evaluated by the Retina Services at the University of California, Davis, and the University of California, San Francisco. Each subject underwent fluorescein angiography and structural optical coherence tomography (OCT). Phase-variance OCT analysis was used to create angiographic images of the retinal and choroidal vasculature. PV-OCT-generated B-scans were superimposed on structural OCT B-scans to allow easy identification of perfused vascular structures. Results: Three patients with vascularized ...

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    6. Feature Of The Week 02/01/2015: Progress on Developing Adaptive Optics OCT for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts (with Audio Narration)

      Feature Of The Week 02/01/2015: Progress on Developing Adaptive Optics OCT for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts (with Audio Narration)

      Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image, complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking ...

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    7. Progress on Developing Adaptive Optics-Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      Progress on Developing Adaptive Optics-Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image , complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking ...

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    8. In vivo imaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1-μm swept-source optical coherence tomography

      In vivo imaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1-μm swept-source optical coherence tomography

      We present a noninvasive phase-variance (pv)–based motion contrast method for depth-resolved imaging of the human chorioretinal complex microcirculation with a newly developed phase-stabilized high speed (100-kHz A-scans/s) 1 - μ m swept-source optical coherence tomography (SSOCT) system. Compared to our previous spectral-domain (spectrometer based) pv-spectral domain OCT (SDOCT) system, this system has the advantages of higher sensitivity, reduced fringe wash-out for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization ...

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    9. Improved in vivo imaging of human blood circulation in the chorioretinal complex using phase variance method with new phase stabilized 1 μm swept-source optical coherence tomography (pv-SSOCT)

      Improved in vivo imaging of human blood circulation in the chorioretinal complex using phase variance method with new phase stabilized 1 μm swept-source optical coherence tomography (pv-SSOCT)

      We demonstrate the feasibility of our newly developed phase stabilized high-speed (100 kHz A-scans/s) 1 μm sweptsource optical coherence tomography (SSOCT) system with the phase-variance based motion contrast method for visualization of human chorioretinal complex microcirculation. Compared to our previously reported spectral domain (spectrometer based) phase-variance (pv)-SDOCT system it has advantages of higher sensitivity, reduced fringe washout for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization method ...

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    10. Progress on Developing Adaptive Optics–Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      Progress on Developing Adaptive Optics–Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image, complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking ...

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    11. Phase-Variance Optical Coherence Tomography: A New Technique for Noninvasive Angiography

      Phase-Variance Optical Coherence Tomography: A New Technique for Noninvasive Angiography

      Purpose Phase-variance optical coherence tomography (PV-OCT) provides volumetric imaging of the retinal vasculature without the need for intravenous injection of a fluorophore. We compare images from PV-OCT and fluorescein angiography (FA) for normal individuals and patients with age-related macular degeneration (AMD) and diabetic retinopathy. Design This is an evaluation of a diagnostic technology. Participants Four patients underwent comparative retinovascular imaging using FA and PV-OCT. Imaging was performed on 1 normal individual, 1 patient with dry AMD, 1 patient with exudative AMD, and 1 patient with nonproliferative diabetic retinopathy. Methods Fluorescein angiography imaging was performed using a Topcon Corp (Tokyo, Japan ...

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    12. Optical imaging of the chorioretinal vasculature in the living human eye

      Optical imaging of the chorioretinal vasculature in the living human eye

      Detailed visualization of microvascular changes in the human retina is clinically limited by the capabilities of angiography imaging, a 2D fundus photograph that requires an intravenous injection of fluorescent dye. Whereas current angiography methods enable visualization of some retinal capillary detail, they do not adequately reveal the choriocapillaris or other microvascular features beneath the retina. We have developed a noninvasive microvascular imaging technique called phase-variance optical coherence tomography (pvOCT), which identifies vasculature three dimensionally through analysis of data acquired with OCT systems. The pvOCT imaging method is not only capable of generating capillary perfusion maps for the retina, but it ...

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    13. Staging of Macular Telangiectasia: Power-Doppler Optical Coherence Tomography and Macular Pigment Optical Density

      Staging of Macular Telangiectasia: Power-Doppler Optical Coherence Tomography and Macular Pigment Optical Density

      Purpose: Two methods were used to study the stages of macular telangiectasia (MacTel): Power-Doppler optical coherence tomography (PD-OCT) which allows imaging of retinal circulation in three-dimensions, and macular pigment optical density (MPOD) which quantifies the distribution of macular carotenoids. Methods: Among 49 patients with MacTel identified, 12 eyes (6 patients) with MacTel and 7 age-matched control eyes (7 patients) were imaged with a custom-built Fourier-domain OCT instrument to acquire PD-OCT images. MPOD was measured using heterochromatic flicker photometry in 10 eyes (5 patients) with MacTel and compared to 44 age-matched control eyes (44 patients). Clinical staging of MacTel was based ...

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    14. Visualization of human retinal and choroidal vascular networks with phase-variance optical coherence tomography

      Visualization of human retinal and choroidal vascular networks with phase-variance optical coherence tomography

      We present in vivo noninvasive retinal and choroidal perfusion maps with phase-variance optical coherence tomography (pvOCT). We acquired a pvOCT volumetric data set of a normal subject and visualized blood circulation in the retina and the choroid. En face projection views of the retina as well as the choroid were generated from a manually segmented volumetric data set. In addition, the processed pvOCT images were compared to current standard imaging modalities used for retinal and choroidal vasculature visualization in clinical settings, including fluorescein angiography (FA) and indocyanine green angiography (ICGA).

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    15. Complex conjugate artifact-free adaptive optics optical coherence tomography of in vivo human optic nerve head

      Complex conjugate artifact-free adaptive optics optical coherence tomography of in vivo human optic nerve head

      We acquired in vivo images of the human optic nerve head (ONH) using an adaptive optics—optical coherence tomography (AO-OCT) system. In order to improve imaging of the lamina cribrosa in the ONH with high lateral resolution and sensitivity, we implemented a complex conjugate artifact-free Fourier domain OCT (Fd-OCT) acquisition scheme with a reference arm-based phase shifting method. This allowed positioning of the lamina cribrosa structures near the zero path length difference where AO-OCT imaging achieves highest sensitivity. Implementation of our complex conjugate artifact removal (CCR) method required constant phase shifts between consecutive axial scans (A-scans), generated by continuous beam ...

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    16. In-vivo imaging of inner retinal cellular morphology with adaptive optics-optical coherence tomography: challenges and possible solutions

      In-vivo imaging of inner retinal cellular morphology with adaptive optics-optical coherence tomography: challenges and possible solutions

      Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the outer layers of the human retina. Despite the significant progress in imaging cone and rod photoreceptor mosaics, visualization of cellular structures in the inner retina has been achieved only with extrinsic contrast agents that have not been approved for use with humans. In this paper we describe the main limiting factors in visualizing inner retinal cells and the ...

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    17. Visualization of human retinal capillary networks: a comparison of intensity, speckle-variance and phase-variance optical coherence tomography

      Visualization of human retinal capillary networks: a comparison of intensity, speckle-variance and phase-variance optical coherence tomography

      We evaluate methods to visualize human retinal micro-circulation in vivo by standard intensity-based optical coherence tomography (OCT), speckle-variance optical coherence tomography (svOCT), and phase-variance optical coherence tomography (pvOCT). En face projection views created from the same volumetric data set of the human retina using all three data processing methods are created and compared. Additionally we used support vector machine (SVM) based semi-automatic segmentation to generate en face projection views of individual retinal layers. The layers include: first, the whole inner retina (from the nerve fiber layer to the outer nuclear layer), and second, from the ganglion cell layer to the ...

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    18. Noninvasive Imaging of the Foveal Avascular Zone with High-Speed, Phase-Variance Optical Coherence Tomography

      Noninvasive Imaging of the Foveal Avascular Zone with High-Speed, Phase-Variance Optical Coherence Tomography

      Purpose. To demonstrate the application of phase-variance optical coherence tomography (pvOCT) for contrast agent–free in vivo imaging of volumetric retinal microcirculation in the human foveal region and for extraction of foveal avascular zone dimensions. Methods. A custom-built, high-speed Fourier-domain OCT retinal imaging system was used to image retinas of two healthy subjects and eight diabetic patients. Through the acquisition of multiple B-scans for each scan location, phase differences between consecutive scans were extracted and used for phase-variance contrast, identifying motion signals from within blood vessels and capillaries. The en face projection view of the inner retinal layers segmented out ...

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    19. Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging

      Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging
      , , , , , , We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was ... [Biomed. Opt. Express 2, 1674-1686 (2011)]
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    20. In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography

      In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography
      We present in vivo volumetric images of human retinal micro-circulation using Fourier-domain optical coherence tomography (Fd-OCT) with the phase-variance based motion contrast method. Currently fundus fluorescein angiography (FA) is the standard technique in clinical settings for visualizing blood circulation of the retina. High contrast imaging of retinal vasculature is achieved by injection of a fluorescein dye into the systemic circulation. We previously reported phase-variance optical coherence tomography (pvOCT) as an alternative and non-invasive technique to image human retinal capillaries. In contrast to FA, pvOCT allows not only noninvasive visualization of a two-dimensional retinal perfusion map but also volumetric morphology of ...
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    21. AO-OCT with reference arm phase shifting for complex conjugate artifact-free imaging of in vivo retinal structures

      AO-OCT with reference arm phase shifting for complex conjugate artifact-free imaging of in vivo retinal structures

      We summarize the performance of an AO-OCT system with reference arm phase shifting for complex conjugate artifactfree imaging of in vivo retinal structures. As a complex conjugate artifact removal (CCR) method we used a previously reported technique requiring constant phase shifts between consecutive A-scans. In our system these shifts were generated by continuous beam path-length changes from offsetting the pivot point of the scanning mirror placed in the system reference arm. In order to reconstruct the complex spectral fringe pattern we used Fourier transformation along the transverse axis and a filtering algorithm. The suppression ratio of mirror complex artifact images ...

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    22. Visualization of human retinal micro-capillaries with phase contrast high-speed optical coherence tomography

      Visualization of human retinal micro-capillaries with phase contrast high-speed optical coherence tomography

      We present high-speed Fourier-domain optical coherence tomography (Fd-OCT) with the phase variance based motion contrast method for visualizing retinal micro-circulation in vivo. This technique allows non-invasive visualization of a two-dimensional retinal perfusion map and concurrent volumetric morphology of retinal microvasculature with high sensitivity. The high-speed acquisition rate at 125kHz A-scans enables reduction of motion artifacts with increased scanning area if compared to previously reported results. Several scanning schemes with different sampling densities and scanning areas are evaluated to find optimal parameters for in vivo imaging. In order to evaluate this technique, we compare OCT micro-capillary imaging using the phase variance ...

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    23. Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography

      Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography
      Single spectrometer-based complex conjugate artifact removal methods are evaluated for in vivo imaging with complementary metal-oxide semiconductor line scan camera based high-speed Fourier-domain optical coherence tomography (FD–OCT) at 100,000 axial scans per second. Performance of three different phase-shifting methods with the same OCT engine is evaluated using modified data acquisition schemes, depending on the requirements of each phase-shifting technique. The suppression ratio of complex conjugate artifact images using a paperboard is assessed for all tested methods. Several other characteristics, including a list of additional hardware requirements (beyond standard FD-OCT components) and data acquisition schemes for each of the ...
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    24. Retinal imaging with a combined adaptive optics/optical coherence tomography and adaptive optics/scanning laser ophthalmoscopy system

      Retinal imaging with a combined adaptive optics/optical coherence tomography and adaptive optics/scanning laser ophthalmoscopy system
      We describe results of retinal imaging with a novel instrument that combines adaptive optics - Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO). One of the benefits of combining Fd-OCT with SLO includes automatic co-registration between the two imaging modalities and the potential for correcting lateral and transversal eye motion resulting in motion artifact-free volumetric retinal imaging. Additionally this allows for direct comparison between retinal structures that can be imaged with both modalities (e.g., photoreceptor mosaics or microvasculature maps). This dual imaging modality could provide insight into some retinal properties that could not be accessed ...
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    25. Evaluation of complex conjugate artifact removal methods used in spectrometer-based Fourier-domain optical coherence tomography systems - a comparative study

      Evaluation of complex conjugate artifact removal methods used in spectrometer-based Fourier-domain optical coherence tomography systems - a comparative study
      We evaluated several, previously published, complex conjugate artifact removal methods and algorithms that have been proposed for Fourier domain optical coherence tomography (Fd-OCT). To ensure comparable conditions, only one OCT system was used, but with modified data acquisition schemes, depending on the requirements of each method/algorithm. This limited our evaluation to single spectrometer based Fd-OCT approaches. The suppression ratio of complex conjugate artifact images using a paperboard is assessed for all tested methods. Several other metrics are also used for comparison, including a list of additional hardware requirements (beyond standard Fd-OCT components) and data acquisition schemes. Finally, in vivo ...
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    1. (25 articles) Dae Yu Kim
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    Evaluation of complex conjugate artifact removal methods used in spectrometer-based Fourier-domain optical coherence tomography systems - a comparative study Retinal imaging with a combined adaptive optics/optical coherence tomography and adaptive optics/scanning laser ophthalmoscopy system Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography Visualization of human retinal micro-capillaries with phase contrast high-speed optical coherence tomography In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging Visualization of human retinal capillary networks: a comparison of intensity, speckle-variance and phase-variance optical coherence tomography Optical imaging of the chorioretinal vasculature in the living human eye Phase-Variance Optical Coherence Tomography: A New Technique for Noninvasive Angiography Feature Of The Week 02/01/2015: Progress on Developing Adaptive Optics OCT for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts (with Audio Narration) Measurement of the Shrinkage of Natural and Simulated Lesions on Root Surfaces using CP-OCT Optic-Net: A Novel Convolutional Neural Network for Diagnosis of Retinal Diseases from Optical Tomography Images