1. Articles from Miao Zhang

    1-24 of 30 1 2 »
    1. Systems and methods to remove shadowgraphic flow projections on OCT angiography

      Systems and methods to remove shadowgraphic flow projections on OCT angiography

      Methods and systems for suppressing shadowgraphic flow projection artifacts in OCT angiography images of a sample are disclosed. In one example approach, normalized OCT angiography data is analyzed at the level of individual A-scans to classify signals as either flow or projection artifact. This classification information is then used to suppress projection artifacts in the three dimensional OCT angiography dataset.

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    2. Three-dimensional Reconstruction of Optical Coherence Tomography Images of Esophagus

      Three-dimensional Reconstruction of Optical Coherence Tomography Images of Esophagus

      The combination of optical coherence tomography (OCT) and endoscope can take images of the body tissues for clinical diagnosis. OCT images are difficult to photograph with regular imaging devices, such as the esophagus and gastrointestinal tract. Three-dimensional reconstruction of the two-dimensional sequence images can help the doctor understand the clinical situation of the body tissue, therefore improve the accuracy of diagnosis. In this paper, Ray Casting method is used to reconstruct three-dimensional image of OCT cross-section images of guinea pig esophagus. Preprocessing including image segmentation, coordinate transformation, angle correction is used to achieve a better result in three-dimensional reconstruction. The ...

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    3. Automated quantification of nonperfusion in the retina using optical coherence tomography angiography

      Automated quantification of nonperfusion in the retina using optical coherence tomography angiography

      Disclosed are methods and systems for measuring areas of nonperfusion in the retina using OCT imaging. The disclosed methods and systems allow for the automated segmentation and quantification of avascular areas of the retina utilizing information obtained from both structural OCT and OCT angiography (OCTA) data. The disclosed methods include filtering approaches which enhance vessel structure while suppressing noise, dynamic thresholding approaches to mitigate the detrimental effects of within-scan variability and low scan quality, and distance transform-based approaches to improve detection of ischemic regions. When combined with methods such as projection-resolved OCTA, the sensitivity to detect nonperfusion within different plexuses ...

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    4. Improve depth of field of optical coherence tomography using finite energy Airy beam

      Improve depth of field of optical coherence tomography using finite energy Airy beam

      We report a technique to break the depth of field (DOF) limit in optical coherence tomography (OCT) using a finite energy Airy beam. The Airy beam is generated using a phase mask in a Fourier transform schematic and provides the DOF improvement due to its low diffraction. We compare Airy beam OCT with conventional Gaussian beam OCT using lateral resolution and sensitivity. Experimental data from the polystyrene beads in water as well as lemon tissue confirm the extension of DOF up to 10 mm in Airy beam OCT, while the DOF of Gaussian beam OCT is less than 3.0 ...

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    5. 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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    6. Systems and methods for retinal layer segmentation in OCT imaging and OCT angiography

      Systems and methods for retinal layer segmentation in OCT imaging and OCT angiography

      Disclosed herein are methods and systems for segmenting, visualizing, and quantifying the layered structure of retina in optical coherence tomography datasets. The disclosed methods have particular application to OCT angiography data, where specific retina layers have distinct vascular structures and characteristics that can be altered in various pathological conditions of the eye.

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    7. Three Dimensional Full-Range Dual-Band Fourier Domain Optical Coherence Tomography Accelerated by Graphic Processing Unit

      Three Dimensional Full-Range Dual-Band Fourier Domain Optical Coherence Tomography Accelerated by Graphic Processing Unit

      The authors present a graphic processing unit (GPU) accelerated three-dimensional (3D) full-range dual-band Fourier domain optical coherence tomography (FD-OCT) using a LabVIEW GPU program with GPU-adaptable algorithms. GPU can dramatically reduce the image processing time, but programing on GPU is more complex than that on central processing unit (CPU). This work implements GPU computing interfaced with LabVIEW, using a LabVIEW GPU analysis toolkit, which significantly reduces the programing complexity. The selected algorithms are suitable for GPU computing in multi-band FD-OCT. The developed system overcomes the problem of long image processing time relative to data acquisition time in CPU. A 65 ...

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    8. Automated segmentation of retinal layer boundaries and capillary plexuses in wide-field optical coherence tomographic angiography

      Automated segmentation of retinal layer boundaries and capillary plexuses in wide-field optical coherence tomographic angiography

      Advances in the retinal layer segmentation of structural optical coherence tomography (OCT) images have allowed the separation of capillary plexuses in OCT angiography (OCTA). With the increased scanning speeds of OCT devices and wider field images (≥10 mm on fast-axis), greater retinal curvature and anatomic variations have introduced new challenges. In this study, we developed a novel automated method to segment seven retinal layer boundaries and two retinal plexuses in wide-field OCTA images. The algorithm was initialized by a series of points forming a guidance point array that estimates the location of retinal layer boundaries. A guided bidirectional graph search ...

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    9. Automated Quantification of Nonperfusion Areas in 3 Vascular Plexuses With Optical Coherence Tomography Angiography in Eyes of Patients With Diabetes

      Automated Quantification of Nonperfusion Areas in 3 Vascular Plexuses With Optical Coherence Tomography Angiography in Eyes of Patients With Diabetes

      Importance Diabetic retinopathy (DR) is a leading cause of vision loss that is managed primarily through qualitative clinical examination of the retina. Optical coherence tomography angiography (OCTA) may offer an objective and quantitative method of evaluating DR. Objective To quantify capillary nonperfusion in 3 vascular plexuses in the macula of eyes patients with diabetes of various retinopathy severity using projection-resolved OCTA (PR-OCTA). Design, Setting, and Participants Cross-sectional study at a tertiary academic center comprising 1 eye each from healthy control individuals and patients with diabetes at different severity stages of retinopathy. Data were acquired and analyzed between January 2015 and ...

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    10. Evaluation of Automatically Quantified Foveal Avascular Zone Metrics for Diagnosis of Diabetic Retinopathy Using Optical Coherence Tomography Angiography

      Evaluation of Automatically Quantified Foveal Avascular Zone Metrics for Diagnosis of Diabetic Retinopathy Using Optical Coherence Tomography Angiography

      Purpose : To describe an automated algorithm to quantify the foveal avascular zone (FAZ), using optical coherence tomography angiography (OCTA), and to compare its performance for diagnosis of diabetic retinopathy (DR) and association with best-corrected visual acuity (BCVA) to that of extrafoveal avascular area (EAA). Methods : We obtained 3 × 3-mm macular OCTA scans in diabetic patients with various levels of DR and healthy controls. An algorithm based on a generalized gradient vector flow (GGVF) snake model detected the FAZ, and metrics assessing FAZ size and irregularity were calculated. We compared the automated FAZ segmentation to manual delineation and tested the within-visit ...

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    11. Automated spectroscopic retinal oximetry with visible-light optical coherence tomography

      Automated spectroscopic retinal oximetry with visible-light optical coherence tomography

      Accurate, quantitative assessment of retinal blood oxygen saturation ( sO 2 ) may provide a useful early indicator of pathophysiology in several ocular diseases. Here, with visible-light optical coherence tomography (OCT), we demonstrate an automated spectroscopic retinal oximetry algorithm to measure the sO 2 within the retinal arteries (A- sO 2 ) and veins (V- sO 2 ) in rats by automatically detecting the vascular posterior boundary on cross-sectional structural OCT. The algorithm was validated in vitro with flow phantoms and in vivo in rats by comparing the sO 2 results, respectively, to those obtained using a blood gas analyzer and pulse oximetry. We ...

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    12. Automated detection of photoreceptor disruption in mild diabetic retinopathy on volumetric optical coherence tomography

      Automated detection of photoreceptor disruption in mild diabetic retinopathy on volumetric optical coherence tomography

      Diabetic retinopathy is a pathology where microvascular circulation abnormalities ultimately result in photoreceptor disruption and, consequently, permanent loss of vision. Here, we developed a method that automatically detects photoreceptor disruption in mild diabetic retinopathy by mapping ellipsoid zone reflectance abnormalities from en face optical coherence tomography images. The algorithm uses a fuzzy c-means scheme with a redefined membership function to assign a defect severity level on each pixel and generate a probability map of defect category affiliation. A novel scheme of unsupervised clustering optimization allows accurate detection of the affected area. The achieved accuracy, sensitivity and specificity were about 90 ...

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    13. OCT Angiography Changes in the 3 Parafoveal Retinal Plexuses in Response to Hyperoxia

      OCT Angiography Changes in the 3 Parafoveal Retinal Plexuses in Response to Hyperoxia

      Purpose Use projection-resolved OCT angiography to investigate the autoregulatory response in the 3 parafoveal retinal plexuses under hyperoxia. Design Prospective cohort study. Participants Nine eyes from 9 healthy participants. Methods One eye from each participant was scanned using a commercial spectral-domain OCT system. Two repeated macular scans (3 × 3 mm 2 ) were acquired at baseline and during oxygen breathing. The split-spectrum amplitude-decorrelation algorithm was used to detect blood flow. The projection-resolved algorithm was used to suppress projection artifacts and resolve blood flow in 3 distinct parafoveal plexuses. The Wilcoxon signed-rank test was used to compare baseline and hyperoxic parameters. The ...

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    14. 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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    15. Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

      Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

      O ptical coherence tomography angiography (OCTA) is limited by projection artifacts from the superficial blood vessels onto deeper layers. We have recently described projection-resolved (PR) OCTA that solves the ambiguity between in situ flow and flow projection along each axial scan and suppresses the artifact on both en face and cross-sectional angiograms. While this method significantly improved the depth resolution of OCTA, the vascular integrity of the deeper layers was not fully preserved. In this study, we propose a novel reflectance-based projection-resolved (rbPR) OCTA algorithm which uses OCT reflectance to enhance the flow signal and suppress the projection artifacts in ...

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    16. Automated three-dimensional registration and volume rebuilding for wide-field angiographic and structural optical coherence tomography

      Automated three-dimensional registration and volume rebuilding for wide-field angiographic and structural optical coherence tomography

      We propose a three-dimensional (3-D) registration method to correct motion artifacts and construct the volume structure for angiographic and structural optical coherence tomography (OCT). This algorithm is particularly suitable for the nonorthogonal wide-field OCT scan acquired by a ultrahigh-speed swept-source system ( > 200    kHz >200  kHz A-scan rate). First, the transverse motion artifacts are corrected by the between-frame registration based on en face OCT angiography (OCTA). After A-scan transverse translation between B-frames, the axial motions are corrected based on the rebuilt boundary of inner limiting membrane. Finally, a within-frame registration is performed for local optimization based on cross-sectional OCTA. We evaluated ...

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    17. 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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    18. Spatial convolution for mirror image suppression in Fourier domain optical coherence tomography

      Spatial convolution for mirror image suppression in Fourier domain optical coherence tomography

      We developed a spatial convolution approach for mirror image suppression in phase-modulated Fourier domain optical coherence tomography, and demonstrated it in vivo for small animal imaging. Utilizing the correlation among neighboring A-scans, the mirror image suppression process was simplified to a three-parameter convolution. By adjusting the three parameters, we can implement different Fourier domain sideband windows, which is important but complicated in existing approaches. By properly selecting the window size, we validated the spatial convolution approach on both simulated and experimental data, and showed that it is versatile, fast, and effective. The new approach reduced the computational cost by 32 ...

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    19. 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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    20. Visualization of 3 Distinct Retinal Plexuses by Projection-Resolved Optical Coherence Tomography Angiography in Diabetic Retinopathy

      Visualization of 3 Distinct Retinal Plexuses by Projection-Resolved Optical Coherence Tomography Angiography in Diabetic Retinopathy

      Importance Projection artifacts in optical coherence tomography angiography (OCTA) blur the retinal vascular plexuses together and limit visualization of the individual plexuses. Objective To describe projection-resolved (PR) OCTA in eyes with diabetic retinopathy (DR) and healthy eyes. Design, Setting, and Participants In this case-control study, patients with DR and healthy controls were enrolled in this observational study from January 26, 2015, to December 4, 2015, at a tertiary academic center. Spectral-domain, 70-kHz OCT obtained 3 × 3-mm macular scans. The PR algorithm suppressed projection artifacts. A semiautomated segmentation algorithm divided PR-OCTA into superficial, intermediate, and deep retinal plexuses. Two masked graders ...

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    21. Automated Quantification of Nonperfusion in Three Retinal Plexuses Using Projection-Resolved Optical Coherence Tomography Angiography in Diabetic Retinopathy

      Automated Quantification of Nonperfusion in Three Retinal Plexuses Using Projection-Resolved Optical Coherence Tomography Angiography in Diabetic Retinopathy

      Purpose : The purpose of this study was to evaluate an automated algorithm for detecting avascular area (AA) in optical coherence tomography angiograms (OCTAs) separated into three individual plexuses using a projection-resolved technique. Methods : A 3 × 3 mm macular OCTA was obtained in 13 healthy and 13 mild nonproliferative diabetic retinopathy (NPDR) participants. A projection-resolved algorithm segmented OCTA into three vascular plexuses: superficial, intermediate, and deep. An automated algorithm detected AA in each of the three plexuses that were segmented and in the combined inner-retinal angiograms. We assessed the diagnostic accuracy of extrafoveal and total AA using segmented and combined angiograms ...

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    22. 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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    23. 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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    24. 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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