1. Articles from Simon S. Gao

    1-24 of 31 1 2 »
    1. Correlation of Outer Retinal Degeneration and Choriocapillaris Loss in Stargardt Disease Using En Face Optical Coherence Tomography and Optical Coherence Tomography Angiography

      Correlation of Outer Retinal Degeneration and Choriocapillaris Loss in Stargardt Disease Using En Face Optical Coherence Tomography and Optical Coherence Tomography Angiography

      Purpose This study measured and correlated degeneration of the junction between the inner and outer segments (IS/OS), the retinal pigment epithelium (RPE), and the choriocapillaris (CC) in Stargardt disease (STGD). Design Prospective cross-sectional study. Methods This study was conducted at the Casey Eye Institute. A total of 23 patients with STGD were enrolled and underwent optical coherence tomography angiography (OCTA). Scans were centered on the fovea. OCT slab projections and en face boundary maps were used to create masks to measure total IS/OS loss or RPE atrophy as well as regions of isolated IS/OS loss, isolated RPE ...

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    2. Signal strength reduction effects in optical coherence tomographic angiography

      Signal strength reduction effects in optical coherence tomographic angiography

      Objective To elucidate the relationship between vessel density (VD) measurements and signal strength in optical coherence tomography angiography (OCTA). Design Cross-sectional study. Subjects: Healthy volunteers. Methods OCTA images obtained from healthy volunteers were analyzed to demonstrate the relationship between signal strength index (SSI) and VD. Experiments were performed to determine the effects of signal strength reduction on VD measurements on the Optovue/AngioVue and Cirrus/AngioPlex OCTA systems. Signal strength reduction was generated by either neutral density filters (NDF) or defocus. Main Outcome Measures Regression analysis of signal strength effects on VD. Results VD decreased linearly with signal strength with ...

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    3. Projection-Resolved Optical Coherence Tomography Angiography of Macular Retinal Circulation in Glaucoma

      Projection-Resolved Optical Coherence Tomography Angiography of Macular Retinal Circulation in Glaucoma

      Purpose To detect macular perfusion defects in glaucoma using projection-resolved optical coherence tomography (OCT) angiography. Design Prospective observation study. Participants A total of 30 perimetric glaucoma and 30 age-matched normal participants were included. Methods One eye of each participant was imaged using 6 × 6–mm macular OCT angiography (OCTA) scan pattern by 70-kHz 840-nm spectral-domain OCT. Flow signal was calculated by the split-spectrum amplitude-decorrelation angiography algorithm. A projection-resolved OCTA (PR-OCTA) algorithm was used to remove flow projection artifacts. Four en face OCTA slabs were analyzed: the superficial vascular complex (SVC), intermediate capillary plexus (ICP), deep capillary plexus (DCP), and all-plexus ...

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    4. Automated boundary detection of the optic disc and layer segmentation of the peripapillary retina in volumetric structural and angiographic optical coherence tomography

      Automated boundary detection of the optic disc and layer segmentation of the peripapillary retina in volumetric structural and angiographic optical coherence tomography

      To improve optic disc boundary detection and peripapillary retinal layer segmentation, we propose an automated approach for structural and angiographic optical coherence tomography. The algorithm was performed on radial cross-sectional B-scans. The disc boundary was detected by searching for the position of Bruch’s membrane opening, and retinal layer boundaries were detected using a dynamic programming-based graph search algorithm on each B-scan without the disc region. A comparison of the disc boundary using our method with that determined by manual delineation showed good accuracy, with an average Dice similarity coefficient ≥0.90 in healthy eyes and eyes with diabetic retinopathy ...

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    5. Automated detection of dilated capillaries on optical coherence tomography angiography

      Automated detection of dilated capillaries on optical coherence tomography angiography

      Automated detection and grading of angiographic high-risk features in diabetic retinopathy can potentially enhance screening and clinical care. We have previously identified capillary dilation in angiograms of the deep plexus in optical coherence tomography angiography as a feature associated with severe diabetic retinopathy. In this study, we present an automated algorithm that uses hybrid contrast to distinguish angiograms with dilated capillaries from healthy controls and then applies saliency measurement to map the extent of the dilated capillary networks. The proposed algorithm agreed well with human grading.

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    6. Choriocapillaris evaluation in choroideremia using optical coherence tomography angiography

      Choriocapillaris evaluation in choroideremia using optical coherence tomography angiography

      The choriocapillaris plays an important role in supporting the metabolic demands of the retina. Studies of the choriocapillaris in disease states with optical coherence tomography angiography (OCTA) have proven insightful. However, image artifacts complicate the identification and quantification of the choriocapillaris in degenerative diseases such as choroideremia. Here, we demonstrate a supervised machine learning approach to detect intact choriocapillaris based on training with results from an expert grader. We trained a random forest classifier to evaluate en face structural OCT and OCTA information along with spatial image features. Evaluation of the trained classifier using previously unseen data showed good agreement ...

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    7. Optical coherence tomographic angiography of choroidal neovascularization ill-defined with fluorescein angiography

      Optical coherence tomographic angiography of choroidal neovascularization ill-defined with fluorescein angiography

      Purpose To evaluate the morphological structure of ill-defined choroidal neovascularisation (CNV) with traditional fluorescein angiography (FA) compared with optical coherence tomographic angiography (OCTA). Methods A retrospective case series study of 11 eyes with ill-defined CNV on FA was performed. Eyes were scanned with commercially available spectral-domain optical coherence tomography (OCT) (70 000 A-scans/s). The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to distinguish blood flow from static tissue. En face OCT angiograms were compared with FA. Results Eleven cases of ill-defined CNV on FA were identified from 10 study participants. Mean age of the participants was 74.5±6 ...

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    8. Evaluation of artifact reduction in optical coherence tomography angiography with real-time tracking and motion correction technology

      Evaluation of artifact reduction in optical coherence tomography angiography with real-time tracking and motion correction technology

      Artifacts introduced by eye motion in optical coherence tomography angiography (OCTA) affect the interpretation of images and the quantification of parameters with clinical value. Eradication of such artifacts in OCTA remains a technical challenge. We developed an algorithm that recognizes five different types of motion artifacts and used it to evaluate the performance of three motion removal technologies. On en face maximum projection of flow images, the summed flow signal in each row and column and the correlation between neighboring rows and columns were calculated. Bright line artifacts were recognized by large summed flow signal. Drifts, distorted lines, and stretch ...

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    9. Compensation for Reflectance Variation in Vessel Density Quantification by Optical Coherence Tomography Angiography

      Compensation for Reflectance Variation in Vessel Density Quantification by Optical Coherence Tomography Angiography

      Purpose : To compensate for reflectance variation when quantifying vessel density by optical coherence tomography angiography (OCTA). Methods : Healthy participants received 6×6-mm macular and 4.5×4.5-mm optic nerve head (ONH) angiography scans on a 70-kHz spectral-domain optical coherence tomography system. The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to compute the OCTA signal. Mean reflectance projection and maximum decorrelation projection were used to create en face OCT and OCTA images. Background OCTA noise in static tissue was evaluated in the foveal avascular zone (FAZ). Vessel density was calculated from en face retinal OCTA that was binarized according to ...

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    10. Calibration of optical coherence tomography angiography with a microfluidic chip

      Calibration of optical coherence tomography angiography with a microfluidic chip

      A microfluidic chip with microchannels ranging from 8 to 96    μ m 96  μm was used to mimic blood vessels down to the capillary level. Blood flow within the microfluidic channels was analyzed with split-spectrum amplitude-decorrelation angiography (SSADA)-based optical coherence tomography (OCT) angiography. It was found that the SSADA decorrelation value was related to both blood flow speed and channel width. SSADA could differentiate nonflowing blood inside the microfluidic channels from static paper. The SSADA decorrelation value was approximately linear with blood flow velocity up to a threshold V sat Vsat of 5.83 ± 1.33    mm / s 5.83 ...

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    11. Evaluating Polypoidal Choroidal Vasculopathy With Optical Coherence Tomography Angiography

      Evaluating Polypoidal Choroidal Vasculopathy With Optical Coherence Tomography Angiography

      Purpose : We observed and analyzed the morphologic characteristics of polypoidal lesions and abnormal branching vascular network (BVN) in patients with polypoidal choroidal vasculopathy (PCV) by optical coherence tomography angiography (OCTA). Methods : A retrospective observational case series was done of patients with PCV. All patients were scanned with a 70-kHz spectral-domain OCT system using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm to distinguish blood flow from static tissue. The OCTA images of these patients were compared to those from indocyanine green angiography (ICGA). Semiautomated segmentation was used to further analyze the polypoidal lesion and the BVN. Results : We studied 13 eyes of ...

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    12. Quantification of choroidal neovascularization vessel length using optical coherence tomography angiography

      Quantification of choroidal neovascularization vessel length using optical coherence tomography angiography

      Quantification of choroidal neovascularization (CNV) as visualized by optical coherence tomography angiography (OCTA) may have importance clinically when diagnosing or tracking disease. Here, we present an automated algorithm to quantify the vessel skeleton of CNV as vessel length. Initial segmentation of the CNV on en face angiograms was achieved using saliency-based detection and thresholding. A level set method was then used to refine vessel edges. Finally, a skeleton algorithm was applied to identify vessel centerlines. The algorithm was tested on nine OCTA scans from participants with CNV and comparisons of the algorithm’s output to manual delineation showed good agreement

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    13. Optical Coherence Tomography Angiography

      Optical Coherence Tomography Angiography

      Optical coherence tomography angiography (OCTA) is a noninvasive approach that can visualize blood vessels down to the capillary level. With the advent of high-speed OCT and efficient algorithms, practical OCTA of ocular circulation is now available to ophthalmologists. Clinical investigations that used OCTA have increased exponentially in the past few years. This review will cover the history of OCTA and survey its most important clinical applications. The salient problems in the interpretation and analysis of OCTA are described, and recent advances are highlighted.

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    14. OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF CHOROIDAL NEOVASCULARIZATION IN FOUR INHERITED RETINAL DYSTROPHIES

      OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF CHOROIDAL NEOVASCULARIZATION IN FOUR INHERITED RETINAL DYSTROPHIES

      Purpose: To demonstrate the clinical utility of optical coherence tomography (OCT) angiography (OCT-A) in inherited retinal dystrophies complicated by choroidal neovascularization (CNV). Methods: Optical coherence tomography angiography and structural OCT were performed using a 70-kHz spectral domain OCT system using the split-spectrum amplitude-decorrelation angiography algorithm. Semiautomated image processing software was used to segment and measure the CNV. Results: Four participants were enrolled to study the following inherited retinal dystrophies complicated by CNV: choroideremia, EFEMP1-related retinopathy, Best vitelliform dystrophy, and adult-onset vitelliform dystrophy. Interpretation of fluorescein angiography was difficult because of abnormal retinal architecture but suggested the presence of CNV. Structural ...

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    15. Optical Coherence Tomography Angiography in Choroideremia: Correlating Choriocapillaris Loss With Overlying Degeneration

      Optical Coherence Tomography Angiography in Choroideremia: Correlating Choriocapillaris Loss With Overlying Degeneration

      Importance Novel therapies for choroideremia, an X-linked recessive chorioretinal degeneration, demand a better understanding of the primary site(s) of cellular degeneration. Optical coherence tomography angiography allows for choriocapillaris (CC) imaging. We compared the extent of structural alterations of the CC, retinal pigment epithelium, and photoreceptors with multimodal imaging. Observations In a clinical case series conducted from September 15, 2014, through February 5, 2015, 14 eyes of 7 male patients with choroideremia (median age, 34 years [interquartile range, 15-46 years]; age range, 13-48 years), 4 eyes of 2 women with choroideremia carrier state (both in mid-50s), and 6 eyes of ...

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    16. Automated Quantification of Capillary Nonperfusion Using Optical Coherence Tomography Angiography in Diabetic Retinopathy

      Automated Quantification of Capillary Nonperfusion Using Optical Coherence Tomography Angiography in Diabetic Retinopathy

      Importance Macular ischemia is a key feature of diabetic retinopathy (DR). Quantification of macular ischemia has potential as a biomarker for DR. Objective To assess the feasibility of automated quantification of capillary nonperfusion as a potential sign of macular ischemia using optical coherence tomography (OCT) angiography. Design, Setting, and Participants An observational study conducted in a tertiary, subspecialty, academic practice evaluated macular nonperfusion with 6 × 6-mm OCT angiography obtained with commercially available 70-kHz OCT and fluorescein angiography (FA). The study was conducted from January 22 to September 18, 2014. Data analysis was performed from October 1, 2014, to April 7 ...

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    17. Advanced image processing for optical coherence tomographic angiography of macular diseases

      Advanced image processing for optical coherence tomographic angiography of macular diseases

      This article provides an overview of advanced image processing for three dimensional (3D) optical coherence tomographic (OCT) angiography of macular diseases, including age-related macular degeneration (AMD) and diabetic retinopathy (DR). A fast automated retinal layers segmentation algorithm using directional graph search was introduced to separates 3D flow data into different layers in the presence of pathologies. Intelligent manual correction methods are also systematically addressed which can be done rapidly on a single frame and then automatically propagated to full 3D volume with accuracy better than 1 pixel. Methods to visualize and analyze the abnormalities including retinal and choroidal neovascularization, retinal ...

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    18. DETECTION OF NONEXUDATIVE CHOROIDAL NEOVASCULARIZATION IN AGE-RELATED MACULAR DEGENERATION WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

      DETECTION OF NONEXUDATIVE CHOROIDAL NEOVASCULARIZATION IN AGE-RELATED MACULAR DEGENERATION WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

      Purpose: To evaluate eyes with age-related macular degeneration and high-risk characteristics for choroidal neovascularization (CNV) with optical coherence tomographic (OCT) angiography to determine whether earlier detection of CNV is possible. Methods: Eyes with drusen, pigmentary changes, and with CNV in the fellow eye were scanned with a 70-kHz spectral domain OCT system (Optovue RTVue-XR Avanti). The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to distinguish blood flow from static tissue. Two masked graders reviewed scans for CNV, defined as flow in the outer retinal/sub-RPE slab. Choroidal neovascularization flow area repeatability and between-grader reproducibility were calculated. Results: Of 32 eyes ...

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    19. Optimization of the split-spectrum amplitude-decorrelation angiography algorithm on a spectral optical coherence tomography system

      Optimization of the split-spectrum amplitude-decorrelation angiography algorithm on a spectral optical coherence tomography system

      The split-spectrum amplitude-decorrelation angiography algorithm was optimized on a spectral optical coherence tomography system using a flow phantom. The number of times the spectrum was split and the bandwidth of each split were adjusted to maximize the flow phantom decorrelation signal-to-noise ratio. The improvement in flow detection was then demonstrated with en face retinal angiograms. The optimized algorithm increased the detectable retinal microvascular flow and decreased the variability of the quantified vessel density in OCT retinal angiograms of healthy human subjects

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    20. OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FEATURES OF DIABETIC RETINOPATHY

      OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FEATURES OF DIABETIC RETINOPATHY

      Purpose: To describe the optical coherence tomography angiography features of diabetic retinopathy. Methods: Using a 70 kHz optical coherence tomography and the split-spectrum amplitude decorrelation angiography algorithm, 6 mm x 6 mm 3-dimensional angiograms of the macula of 4 patients with diabetic retinopathy were obtained and compared with fluorescein angiography for features cataloged by the Early Treatment of Diabetic Retinopathy Study. Results: Optical coherence tomography angiography detected enlargement and distortion of the foveal avascular zone, retinal capillary dropout, and pruning of arteriolar branches. Areas of capillary loss obscured by fluorescein leakage on fluorescein angiography were more clearly defined on optical ...

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    21. Automated choroidal neovascularization detection algorithm for optical coherence tomography angiography

      Automated choroidal neovascularization detection algorithm for optical coherence tomography angiography

      Optical coherence tomography angiography has recently been used to visualize choroidal neovascularization (CNV) in participants with age-related macular degeneration. Identification and quantification of CNV area is important clinically for disease assessment. An automated algorithm for CNV area detection is presented in this article. It relies on denoising and a saliency detection model to overcome issues such as projection artifacts and the heterogeneity of CNV. Qualitative and quantitative evaluations were performed on scans of 7 participants. Results from the algorithm agreed well with manual delineation of CNV area.

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    22. En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

      En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

      An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans ( 2 × 2     mm ) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The ...

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    23. Optical Coherence Tomography Angiography of Peripapillary Retinal Blood Flow Response to Hyperoxia

      Optical Coherence Tomography Angiography of Peripapillary Retinal Blood Flow Response to Hyperoxia

      Purpose. To measure the change in peripapillary retinal blood flow in response to hyperoxia by using optical coherence tomography (OCT) angiography. Methods. One eye of each healthy human participants (six) was scanned with a commercial high-speed (70 kHz) spectral OCT. Scans were captured twice after 10-minute exposures to normal breathing (baseline) and hyperoxia. Blood flow was detected by the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Peripapillary retinal blood flow index and vessel density were calculated from en face maximum projections of the retinal layers. The experiment was performed on 2 separate days for each participant. Coefficient of variation (CV) was used ...

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    24. Quantitative optical coherence tomography angiography of vascular abnormalities in the living human eye

      Quantitative optical coherence tomography angiography of vascular abnormalities in the living human eye

      Retinal vascular diseases are important causes of vision loss. A detailed evaluation of the vascular abnormalities facilitates diagnosis and treatment in these diseases. Optical coherence tomography (OCT) angiography using the highly efficient split-spectrum amplitude decorrelation angiography algorithm offers an alternative to conventional dye-based retinal angiography. OCT angiography has several advantages, including 3D visualization of retinal and choroidal circulations (including the choriocapillaris) and avoidance of dye injection-related complications. Results from six illustrative cases are reported. In diabetic retinopathy, OCT angiography can detect neovascularization and quantify ischemia. In age-related macular degeneration, choroidal neovascularization can be observed without the obscuration of details caused ...

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    1-24 of 31 1 2 »
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    Quantitative imaging of cochlear soft tissues in wild-type and hearing-impaired transgenic mice by spectral domain optical coherence tomography Biophysical Mechanisms Underlying Hearing Loss Associated with a Shortened Tectorial Membrane Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography Methodology for assessment of structural vibrations by spectral domain optical coherence tomography In vivo vibrometry inside the apex of the mouse cochlea using spectral domain optical coherence tomography Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography Quantitative optical coherence tomography angiography of vascular abnormalities in the living human eye Automated choroidal neovascularization detection algorithm for optical coherence tomography angiography OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FEATURES OF DIABETIC RETINOPATHY Automated Quantification of Capillary Nonperfusion Using Optical Coherence Tomography Angiography in Diabetic Retinopathy Cooperative low-rank models for removing stripe noise from OCTA images MS-CAM: Multi-Scale Class Activation Maps for Weakly-supervised Segmentation of Geographic Atrophy Lesions in SD-OCT Images