1. Articles from Ruikang K. Wang

    1-24 of 262 1 2 3 4 ... 9 10 11 »
    1. Relative retinal flow velocity detection using optical coherence tomography angiography imaging

      Relative retinal flow velocity detection using optical coherence tomography angiography imaging

      Optical coherence tomography angiography (OCTA) imaging is a valuable tool for the visualization of retinal vasculature at an unprecedented level of details. However, due to relatively long time-interval between repeated scans in the conventional OCTA scanning protocol, the OCTA flow signal suffers from low dynamic range and loss of velocity-intensity correlation. The ability to distinguish fast and slow flow in the retina may provide a powerful tool for the assessment of early-stage retinal diseases such as vein occlusion. Here, we report a method to detect relative flow velocity in human retina using a 67.5 kHz spectral-domain OCTA device. By ...

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    2. Polarization sensitive optical coherence tomography for imaging microvascular information within living tissue without polarization-induced artifacts

      Polarization sensitive optical coherence tomography for imaging microvascular information within living tissue without polarization-induced artifacts

      When imaging birefringent samples using optical coherence tomography angiography (OCTA), the phase retardation may appear opposite to the phase change due to the blood flow in the orthogonal signals, for which a cancellation effect can occur when deriving OCTA signals. This effect can diminish the ability of OCTA to detect vascular information, leading to an erroneous interpretation of the final OCTA images. To mitigate this issue, we demonstrate polarization-sensitive optical coherence tomography (PS-OCT) to image microvascular information within a living sample without polarization induced artifacts. The system is furnished with a swept source OCT (SS-OCT) that incorporates two imaging modes ...

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    3. Handheld swept-source optical coherence tomography guided by smartphone-enabled wide-field autofluorescence photography for imaging facial sebaceous glands

      Handheld swept-source optical coherence tomography guided by smartphone-enabled wide-field autofluorescence photography for imaging facial sebaceous glands

      We report a method to image facial sebaceous glands (SGs) using smartphone-enabled wide-field autofluorescence photography (AFP) and handheld swept-source optical coherence tomography (SS-OCT). Smartphone-enabled AFP provides a 2D wide-field fluorescence image that is used both as a functional mapping of the sebum and a positioning guidance for OCT imaging of the SG. Following the guidance, handheld SS-OCT conducts the volume scan to investigate depth-resolved conditions of the SG in the selected regions of interest. We show the results from smartphone-enabled AFP and handheld SS-OCT to demonstrate the ability of our method to image facial SGs, potentially useful for the assessment ...

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    4. Macular microvascular parameters in the ganglion cell-inner plexiform layer derived by optical coherence tomography angiography: Vascular structure-central visual function analysis

      Macular microvascular parameters in the ganglion cell-inner plexiform layer derived by optical coherence tomography angiography: Vascular structure-central visual function analysis

      Purpose To investigate the relationships between global and sectoral macular vascular microcirculation parameters in the ganglion cell-inner plexiform layer (GCIPL) assessed by optical coherence tomography angiography (OCTA), and global and sectoral visual field (VF) central mean sensitivity (CMS) assessed by standard automated perimetry. Methods Fifty-four eyes with open angle glaucoma were scanned using a swept-source OCTA (Plex Elite 9000, Zeiss, Dublin, CA) and macular vascular microcirculation was measured by calculating the overall flux and vessel area density (VAD) over the entire 6mm x 6mm area, excluding large retinal vessels. Central 10-degree VF CMS was calculated based on 24–2 VF ...

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    5. Optical microangiography reveals temporal and depth-resolved hemodynamic change in mouse barrel cortex during whisker stimulation

      Optical microangiography reveals temporal and depth-resolved hemodynamic change in mouse barrel cortex during whisker stimulation

      Significance: Cerebral blood flow (CBF) regulation at neurovascular coupling (NVC) plays an important role in normal brain functioning to support oxygen delivery to activating neurons. Therefore, studying the mechanisms of CBF adjustment is crucial for the improved understanding of brain activity. Aim: We investigated the temporal profile of hemodynamic signal change in mouse cortex caused by neural activation and its variation over cortical depth. Approach: Following the cranial window surgery, intrinsic optical signal imaging (IOSI) was used to spatially locate the activated region in mouse cortex during whisker stimulation. Optical microangiography (OMAG), the functional extension of optical coherence tomography, was ...

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    6. Semi-automated registration and segmentation for gingival tissue volume measurement on 3D OCT images

      Semi-automated registration and segmentation for gingival tissue volume measurement on 3D OCT images

      The change in gingival tissue volume may be used to indicate changes in gingival inflammation, which may be useful for the clinical assessment of gingival health. Properly quantifying gingival tissue volume requires a robust technique for accurate registration and segmentation of longitudinally captured 3-dimensional (3D) images. In this paper, a semi-automated registration and segmentation method for micrometer resolution measurement of gingival-tissue volume is proposed for 3D optical coherence tomography (OCT) imaging. For quantification, relative changes in gingiva tissue volume are measured based on changes in the gingiva surface height using the tooth surface as a reference. This report conducted repeatability ...

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    7. Automated vessel diameter quantification and vessel tracing for OCT angiography

      Automated vessel diameter quantification and vessel tracing for OCT angiography

      Optical coherence tomography angiography (OCTA) is capable of non‐invasively imaging the vascular networks within circulatory tissue beds in vivo. Following improvements in OCTA image quality, it is now possible to extract vascular parameters from imaging data to potentially facilitate the diagnosis and treatment of human disease. In this paper, we present a method for automated mapping of vessel diameter down to the individual capillary level, through gradient‐guided minimum radial distance (MRD). During validation using well‐characterized microfluidic flow phantoms, this method demonstrated superior consistency and a nearly threefold decrease in error when compared to currently accepted techniques. In ...

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    8. OCT Angiography to Predict Geographic Atrophy Progression using Choriocapillaris Flow Void as a Biomarker

      OCT Angiography to Predict Geographic Atrophy Progression using Choriocapillaris Flow Void as a Biomarker

      Purpose : To investigate the relationship between choriocapillaris (CC) flow void (FV) percentage and geographic atrophy (GA) growth rate, and study how variations in FV percentage surrounding GA predict regional GA growth. Methods : This prospective, longitudinal study enrolled subjects with GA secondary to nonexudative age-related macular degeneration. Optical coherence tomography angiography imaged the CC and FV percentage was evaluated using a validated algorithm. GA growth rate was measured as the difference in the square root of GA area divided by the months between baseline and follow-up imaging. Results : Twelve eyes from 7 subjects with a mean age of 80 ± 5 years ...

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    9. Quantifying Subclinical and Longitudinal Microvascular Changes Following Episcleral Plaque Brachytherapy Using Spectral Domain–Optical Coherence Tomography Angiography

      Quantifying Subclinical and Longitudinal Microvascular Changes Following Episcleral Plaque Brachytherapy Using Spectral Domain–Optical Coherence Tomography Angiography

      Purpose: This work assesses longitudinal microvascular changes in eyes treated with iodine-125 episcleral plaque brachytherapy (EPB). Methods: High-resolution optical coherence tomography angiograms (OCTAs) of the central 3 × 3-mm macula were obtained from iodine-125 EPB–treated and untreated fellow eyes of 61 patients. Previously validated semiautomated algorithms quantified capillary density (vessel skeleton density [VSD]) and caliber (vessel diameter index). Nonperfusion was also quantified as flow impairment region (FIR). Examinations from treated and fellow eyes obtained before treatment and at 6-month, 1-year, and 2-year intervals were compared using generalized estimating equation linear models. Dosimetry maps evaluated spatial correlation between radiation dose and ...

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    10. Validation of a Compensation Strategy used to Detect Choriocapillaris Flow Deficits Under Drusen with Swept Source OCT Angiography

      Validation of a Compensation Strategy used to Detect Choriocapillaris Flow Deficits Under Drusen with Swept Source OCT Angiography

      Purpose A compensation strategy that was developed to measure the choriocapillaris (CC) flow deficits (FDs) under drusen was tested in eyes with large drusen from age-related macular degeneration (AMD) before and after the drusen spontaneously resolved without evidence of disease progression. Design Prospective, observational consecutive case series. Methods Patients with AMD were enrolled in a prospective SS-OCT imaging study (PLEX® Elite 9000, Carl Zeiss Meditec). Consecutive eyes with large drusen were followed, and eyes that underwent spontaneous collapse of drusen without evidence of disease progression were identified retrospectively. The drusen-resolved regions were manually outlined. CC FDs were measured using a ...

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    11. Quantitative Analysis of the Choriocapillaris in Uveitis Using en face Swept Source Optical Coherence Tomography Angiography

      Quantitative Analysis of the Choriocapillaris in Uveitis Using en face Swept Source Optical Coherence Tomography Angiography

      Purpose To perform a quantitative analysis of choriocapillaris (CC) flow deficits (FDs) in patients with uveitis. Design Retrospective cross-sectional study Methods Swept-source optical coherence tomography based angiography (SS-OCTA) macular volume scans (3x3 mm and 6x6 mm) were obtained using the PLEX® Elite 9000: En face CC images were generated and analyzed using an automated flow deficit identification algorithm. Three quantitative metrics were determined for each eye: FD number (FDN), mean FD size (MFDS), and FD density (FDD). Quantitative metrics were compared between uveitis and control eyes. The uveitis cohort was further subdivided by the presence or absence of choroidal involvement ...

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    12. Mean-Subtraction Method for De-shadowing of Tail Artifacts in Cerebral OCTA Images: A Proof of Concept

      Mean-Subtraction Method for De-shadowing of Tail Artifacts in Cerebral OCTA Images: A Proof of Concept

      When imaging brain vasculature with optical coherence tomography angiography (OCTA), volumetric analysis of cortical vascular networks in OCTA datasets is frequently challenging due to the presence of artifacts, which appear as multiple-scattering tails beneath superficial large vessels in OCTA images. These tails shadow underlying small vessels, making the assessment of vascular morphology in the deep cortex difficult. In this work, we introduce an image processing technique based on mean subtraction of the depth profile that can effectively reduce these tails to better reveal small hidden vessels compared to the current tail removal approach. With the improved vascular image quality, we ...

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    13. Optical coherence tomography for the investigation of skin adaptation to mechanical stress

      Optical coherence tomography for the investigation of skin adaptation to mechanical stress

      Background Skin breakdown due to limb‐socket interface stress is a significant problem for lower limb prosthesis users. While it is known that skin can adapt to stress to become more resistant to breakdown, little is understood about skin adaptation and few methods exist to noninvasively investigate it. In this study, we present novel, noninvasive imaging methods using Optical Coherence Tomography (OCT) to assess key features of the cutaneous microvasculature that may be involved in skin adaptation. Materials and Methods Eight able‐bodied participants wore a modified below‐knee prosthetic socket for two weeks to stress the skin of their ...

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    14. Non‐invasive multimodal imaging by integrating optical coherence tomography with autofluorescence imaging for dental applications

      Non‐invasive multimodal imaging by integrating optical coherence tomography with autofluorescence imaging for dental applications

      We report the development of an integrated multi‐functional imaging system capable of providing anatomical (optical coherence tomography, OCT), functional (OCT angiography, OCTA) and molecular imaging (light‐induced autofluorescence, LIAF) for in vivo dental applications. Blue excitation light (405 nm) was used for LIAF imaging, while the OCT was powered by a 1310 nm swept laser source. A red‐green‐blue (RGB) digital camera, with a 450 nm cut‐on broad‐band optical filter, was used for LIAF detection. The exciting light source and camera were integrated directly with the OCT scanning probe. The integrated system used two non‐invasive ...

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    15. Measurement and visualization of stimulus-evoked tissue dynamics in mouse barrel cortex using phase-sensitive optical coherence tomography

      Measurement and visualization of stimulus-evoked tissue dynamics in mouse barrel cortex using phase-sensitive optical coherence tomography

      We describe a method to measure tissue dynamics in mouse barrel cortex during functional activation via phase-sensitive optical coherence tomography (PhS-OCT). The method measures the phase changes in OCT signals, which are induced by the tissue volume change, upon which to localize the activated tissue region. Phase unwrapping, compensation and normalization are applied to increase the dynamic range of the OCT phase detection. To guide the OCT scanning, intrinsic optical signal imaging (IOSI) system equipped with a green light laser source (532 nm) is integrated with the PhS-OCT system to provide a full field time-lapsed images of the reflectance that ...

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    16. Ultra-Widefield Protocol Enhances Automated Classification of Diabetic Retinopathy Severity with Optical Coherence Tomography Angiography

      Ultra-Widefield Protocol Enhances Automated Classification of Diabetic Retinopathy Severity with Optical Coherence Tomography Angiography

      Purpose To assess the diagnostic utility of retinal nonperfusion to classify eyes based on diabetic retinopathy (DR) severity on optical coherence tomography angiography (OCTA). To determine whether wider field of view (FOV) OCTA protocols enhance the diagnostic utility of retinal nonperfusion in the classification of DR severity. Design Retrospective cross-sectional study Subjects Diabetic patients undergoing ultra-widefield OCTA imaging at one academic retina practice Methods Ultra-widefield OCTA images with 100 degree FOV were obtained from 60 eyes. Eyes were grouped as diabetes without retinopathy (DWR), nonproliferative diabetic retinopathy (NPDR) or proliferative diabetic retinopathy (PDR). The ratio of nonperfusion (RNP) was expressed ...

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    17. Electrically tunable lens integrated with optical coherence tomography angiography for cerebral blood flow imaging in deep cortical layers in mice

      Electrically tunable lens integrated with optical coherence tomography angiography for cerebral blood flow imaging in deep cortical layers in mice

      We report the use of an electrically tunable lens (ETL) in a 1.3 μm spectral-domain optical coherence tomography (SD-OCT) system to overcome the depth of focus (DOF) limitation in conventional OCT systems for OCT angiography (OCTA) in a mouse cerebral cortex. The ETL provides fast and dynamic control of the axial focus of the probe beam along the entire range of the mouse cortex, upon which we performed cerebral blood flow imaging of all cortical layers by stitching the OCTA images automatically captured at six focal depths. Capillary vasculature and axial blood flow velocity were revealed in distinctive cortical ...

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    18. Handheld swept-source optical coherence tomography with angiography in awake premature neonates

      Handheld swept-source optical coherence tomography with angiography in awake premature neonates

      Background: Retinopathy of prematurity (ROP) can lead to retinal detachment and severe vision loss and is a common cause of childhood blindness. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality that can be used to detect potential abnormalities in the microvasculature in this population. The objective of this study is to assess the feasibility of a newly developed handheld swept source OCT (SS-OCT) device to successfully acquire structural vitreoretinal and retinal microvascular images in awake premature infants. Methods: OCT and OCTA images were acquired at the time of routine ROP examinations from awake, unsedated preterm infants in the ...

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    19. Correlations between Different Choriocapillaris Flow Deficit Parameters in Normal Eyes using Swept Source OCT Angiography

      Correlations between Different Choriocapillaris Flow Deficit Parameters in Normal Eyes using Swept Source OCT Angiography

      Purpose Choriocapillaris (CC) imaging of normal eyes with swept-source optical coherence tomography SS-OCTA was performed, and the percentage of CC flow deficits (FD%) and the average area of CC flow deficits (FDa) were compared within given macular regions. Design A prospective, cross-sectional study. Methods Subjects with normal eyes ranging in age from their 20s through their 80s were imaged with SS-OCTA (PLEX Elite 9000, Carl Zeiss Meditec, Dublin, CA) using both 3x3 mm and 6x6 mm macular scan patterns. The CC images were generated using a previously published and validated algorithm. In both 3x3 mm and 6x6 mm scans, the ...

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    20. Spatial resolution in dynamic optical coherence elastography

      Spatial resolution in dynamic optical coherence elastography

      Dynamic optical coherence elastography (OCE) tracks elastic wave propagation speed within tissue, enabling quantitative three-dimensional imaging of the elastic modulus. We show that propagating mechanical waves are mode converted at interfaces, creating a finite region on the order of an acoustic wavelength where there is not a simple one-to-one correspondence between wave speed and elastic modulus. Depending on the details of a boundary’s geometry and elasticity contrast, highly complex propagating fields produced near the boundary can substantially affect both the spatial resolution and contrast of the elasticity image. We demonstrate boundary effects on Rayleigh waves incident on a vertical ...

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    21. Two-Year Risk of Exudation in Eyes with Nonexudative Age-Related Macular Degeneration and Subclinical Neovascularization Detected with Swept Source Optical Coherence Tomography Angiography

      Two-Year Risk of Exudation in Eyes with Nonexudative Age-Related Macular Degeneration and Subclinical Neovascularization Detected with Swept Source Optical Coherence Tomography Angiography

      Purpose Swept source optical coherence tomography angiography (SS-OCTA) was used to study the prevalence, incidence, and natural history of subclinical macular neovascularization (MNV) in eyes with unilateral nonexudative age-related macular degeneration. Design Prospective cohort study. Methods Patients were imaged using 3- × 3-mm and 6- × 6-mm SS-OCTA scan patterns. MNV was detected using the outer retina to choriocapillaris en face slab. Prevalence and incidence of subclinical MNV, Kaplan–Meier cumulative estimates for the overall risk of exudation, and the association between neovascular lesion size and the risk of exudation were assessed through 2 years. Results From August 2014 through March 2018 ...

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    22. Systems and methods for in vivo visualization of lymphatic vessels with optical coherence tomography

      Systems and methods for in vivo visualization of lymphatic vessels with optical coherence tomography

      The present technology relates generally to systems and methods for in vivo visualization of lymphatic vessels. A system includes an optical coherence tomography (OCT) device and a computing device coupled to the OCT device configured to cause the OCT device to perform an OCT scan, generate image data in response to the OCT scan, and apply an eigendecomposition filter to the image data to produce processed image data. Alternatively or in addition, the computing device can compensate for scattering attenuation along an optical axis of the OCT scan in the image data set to generate compensated image data, enhance contrast ...

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    23. Quantifying choriocapillaris hypoperfusion in patients with choroidal neovascularization using swept-source OCT angiography

      Quantifying choriocapillaris hypoperfusion in patients with choroidal neovascularization using swept-source OCT angiography

      Purpose: To compare choriocapillaris flow voids (FV) in patients with neovascular age-related macular degeneration (AMD) with age-matched normal controls using swept-source optical coherence tomography angiography (SS-OCTA). Patients and methods: Eleven eyes of 11 subjects with neovascular AMD and 11 eyes of 11 age-similar normal subjects were imaged using SS-OCTA with a 6x6mm scanning pattern. Choriocapillaris FV, defined as a percentage of regions determined to have flow deficits divided by the total scanned region, was measured using a one standard deviation thresholding algorithm developed from a database of age-similar normal subjects. Results: Choriocapillaris FV was more extensive in patients with choroidal ...

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    24. Quantification of choriocapillaris with OCTA: a comparison study

      Quantification of choriocapillaris with OCTA: a comparison study

      Purpose To demonstrate the variation in quantitative choriocapillaris (CC) metrics with various binarization approaches using optical coherence tomography angiography (OCTA). Design Retrospective, observational, cross-sectional case series. Methods 3x3 mm and 6x6 mm macular OCTA scans were obtained from normal eyes and from eyes with drusen secondary to AMD. The CC slab was extracted and the CC flow deficits (FDs) were segmented with two previously published algorithms: fuzzy C-means approach (FCM method) and Phansalkar’s local thresholding (Phansalkar method). Four different values for the radius were used in order to investigate the effect on the FD segmentation when using the Phansalkar ...

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    1. (260 articles) Ruikang K. Wang
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