1. Articles from Sina Farsiu

    1-24 of 78 1 2 3 4 »
    1. Optical coherence refraction tomography

      Optical coherence refraction tomography

      Optical coherence tomography (OCT) is a cross-sectional, micrometre-scale imaging modality with widespread clinical application. Typical OCT systems sacrifice lateral resolution to achieve long depths of focus for bulk tissue imaging, and therefore tend to have better axial than lateral resolution. Such anisotropic resolution can obscure fine ultrastructural features. Furthermore, conventional OCT suffers from refraction-induced image distortions. Here, we introduce optical coherence refraction tomography (OCRT), which extends the superior axial resolution to the lateral dimension, synthesizing undistorted cross-sectional image reconstructions from multiple conventional images acquired with angular diversity. In correcting refraction-induced distortions to register the OCT images, OCRT also achieves spatially ...

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    2. Postdoctoral Associate Position at Duke Vision and Image Processing Laboratory

      Postdoctoral Associate Position at Duke Vision and Image Processing Laboratory

      Immediate opening at Duke University Biomedical Engineering Department for a postdoc interested in interdisciplinary applications of image analysis and computer vision with emphasis on optical coherence tomography image analysis. Postdoc will be supervised by Prof. Sina Farsiu ( http://people.duke.edu/~sf59/ ). The candidate must have a demonstrated strong background in image processing as evidenced by publication of papers in high-impact peer-reviewed journals. Programming skill in MATLAB/Python is required. PhD in EE, BME, or CS. Prior experience in ophthalmic sciences, optical coherence tomography, adaptive optics is a plus but not necessary. Projects can be chosen based on the interests ...

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    3. Deep longitudinal transfer learning-based automatic segmentation of photoreceptor ellipsoid zone defects on optical coherence tomography images of macular telangiectasia type 2

      Deep longitudinal transfer learning-based automatic segmentation of photoreceptor ellipsoid zone defects on optical coherence tomography images of macular telangiectasia type 2

      Photoreceptor ellipsoid zone (EZ) defects visible on optical coherence tomography (OCT) are important imaging biomarkers for the onset and progression of macular diseases. As such, accurate quantification of EZ defects is paramount to monitor disease progression and treatment efficacy over time. We developed and trained a novel deep learning-based method called Deep OCT Atrophy Detection (DOCTAD) to automatically segment EZ defect areas by classifying 3-dimensional A-scan clusters as normal or defective. Furthermore, we introduce a longitudinal transfer learning paradigm in which the algorithm learns from segmentation errors on images obtained at one time point to segment subsequent images with higher ...

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    4. Comparison of chorioretinal layers in rhesus macaques using spectral-domain optical coherence tomography and high-resolution histological sections

      Comparison of chorioretinal layers in rhesus macaques using spectral-domain optical coherence tomography and high-resolution histological sections

      Nonhuman primates are important preclinical models of retinal diseases because they uniquely possess a macula similar to humans. Ocular imaging technologies such as spectral-domain optical coherence tomography (SD-OCT) allow noninvasive, in vivo measurements of chorioretinal layers with near-histological resolution. However, the boundaries are based on differences in reflectivity, and detailed correlations with histological tissue layers have not been explored in rhesus macaques, which are widely used for biomedical research. Here, we compare the macular anatomy and thickness measurements of chorioretinal layers in rhesus macaque eyes using SD-OCT and high-resolution histological sections. Images were obtained from methylmethacrylate-embedded histological sections of 6 ...

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    5. Statistical Models of Signal and Noise and Fundamental Limits of Segmentation Accuracy in Retinal Optical Coherence Tomography

      Statistical Models of Signal and Noise and Fundamental Limits of Segmentation Accuracy in Retinal Optical Coherence Tomography

      Optical coherence tomography (OCT) has revolutionized diagnosis and prognosis of ophthalmic diseases by visualization and measurement of retinal layers. To speed up quantitative analysis of disease biomarkers, an increasing number of automatic segmentation algorithms have been proposed to estimate the boundary locations of retinal layers. While the performance of these algorithms has significantly improved in recent years, a critical question to ask is how far we are from a theoretical limit to OCT segmentation performance. In this paper, we present the Cramèr-Rao lower bounds (CRLBs) for the problem of OCT layer segmentation. In deriving the CRLBs, we address the ...

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    6. Characterization of Long Working Distance Optical Coherence Tomography for Imaging of Pediatric Retinal Pathology

      Characterization of Long Working Distance Optical Coherence Tomography for Imaging of Pediatric Retinal Pathology

      Purpose : We determined the feasibility of fovea and optic nerve head imaging with a long working distance (LWD) swept source optical coherence tomography (OCT) prototype in adults, teenagers, and young children. Methods : A prototype swept source OCT system with a LWD (defined as distance from the last optical element of the imaging system to the eye) of 350 mm with custom fixation targets was developed to facilitate imaging of children. Imaging was performed in 49 participants from three age groups: 26 adults, 16 children 13 to 18 years old (teenagers), and seven children under 6 years old (young children) under ...

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    7. Macular fluid reduces reproducibility of choroidal thickness measurements on enhanced depth optical coherence tomography

      Macular fluid reduces reproducibility of choroidal thickness measurements on enhanced depth optical coherence tomography

      Purpose To determine if different types of retinal fluid in the central macula affect the reproducibility of choroidal thickness (CT) measurements on enhanced depth imaging optical coherence tomography (EDI-OCT) Design retrospective, reliability analysis Methods EDI-OCT images were obtained and the choroidal-scleral junction was analyzed through semi-automated segmentation. CT was measured at the fovea and averaged across the central 3 mm horizontal segment. Demographic data, central macular thickness and type of fluid present were recorded. Intragrader and intergrader repeatability were assessed using the intraclass correlation coefficient (ICC) and coefficient of repeatability (CR). Results Of 124 eyes analyzed, 60 (48.4%) had ...

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    8. Correlation Between Macular Integrity Assessment and Optical Coherence Tomography Imaging of Ellipsoid Zone in Macular Telangiectasia Type 2

      Correlation Between Macular Integrity Assessment and Optical Coherence Tomography Imaging of Ellipsoid Zone in Macular Telangiectasia Type 2

      Purpose : To correlate ellipsoid zone (EZ) defects on spectral-domain optical coherence tomography (SD-OCT) with retinal sensitivity loss on macular integrity assessment (MAIA) microperimetry in macular telangiectasia type 2 (MacTel). Methods : Macular SD-OCT volumes and microperimetry maps were obtained during the international, multicenter, randomized phase 2 trial of ciliary neurotrophic factor for type 2 MacTel on two visits within 5 days of one another. Software was developed to register SD-OCT to MAIA scanning laser ophthalmoscopy images and to overlay EZ defect areas on the microperimetry maps generated from microperimetry sensitivity values at specific points and from interpolated sensitivity values. A total ...

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    9. Retinal imaging in human autopsy eyes using a custom optical coherence tomography periscope

      Retinal imaging in human autopsy eyes using a custom optical coherence tomography periscope

      Age-related macular degeneration (AMD) is a major cause of vision loss in the elderly. To better study the pathobiology of AMD, postmortem eyes offer an excellent opportunity to correlate optical coherence tomography (OCT) imaging characteristics with histopathology. However, postmortem eyes from autopsy present challenges to standard OCT imaging including opaque anterior segment structures and standard of care autopsy processing resulting in oblique views to the macula. To overcome these challenges, we report a custom periscope attached by a standard mount to an OCT sample arm and demonstrate high quality macular OCT acquisitions in autopsy-processed eyes.

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    10. Optical Coherence Tomography Predictors of Risk for Progression to Non-Neovascular Atrophic Age-Related Macular Degeneration

      Optical Coherence Tomography Predictors of Risk for Progression to Non-Neovascular Atrophic Age-Related Macular Degeneration

      Purpose Appearance of geographic atrophy (GA) on color photography (CP) is preceded by specific features on spectral-domain optical coherence tomography (SD OCT). We aimed to build SD OCT–based risk assessment models for 5-year new onset of GA and central GA on CP. Design Prospective, longitudinal study. Participants Age-Related Eye Disease Study 2 Ancillary SD OCT study participants with age-related macular degeneration (AMD) with bilateral large drusen or noncentral GA and at least 1 eye without advanced disease (n = 317). Methods For 1 eye per participant, qualitative and quantitative SD OCT variables were derived from standardized grading and semiautomated segmentation ...

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    11. Automatic segmentation of nine retinal layer boundaries in OCT images of non-exudative AMD patients using deep learning and graph search

      Automatic segmentation of nine retinal layer boundaries in OCT images of non-exudative AMD patients using deep learning and graph search

      We present a novel framework combining convolutional neural networks (CNN) and graph search methods (termed as CNN-GS) for the automatic segmentation of nine layer boundaries on retinal optical coherence tomography (OCT) images. CNN-GS first utilizes a CNN to extract features of specific retinal layer boundaries and train a corresponding classifier to delineate a pilot estimate of the eight layers. Next, a graph search method uses the probability maps created from the CNN to find the final boundaries. We validated our proposed method on 60 volumes (2915 B-scans) from 20 human eyes with non-exudative age-related macular degeneration (AMD), which attested to ...

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    12. Enhanced visualization of peripheral retinal vasculature with wavefront sensorless adaptive optics optical coherence tomography angiography in diabetic patients

      Enhanced visualization of peripheral retinal vasculature with wavefront sensorless adaptive optics optical coherence tomography angiography in diabetic patients

      Optical coherence tomography angiography (OCTA) is a promising technique for non-invasive visualization of vessel networks in the human eye. We debut a system capable of acquiring wide field-of-view ( > 70 ° >70° ) OCT angiograms without mosaicking. Additionally, we report on enhancing the visualization of peripheral microvasculature using wavefront sensorless adaptive optics (WSAO). We employed a fast WSAO algorithm that enabled wavefront correction in < 2    s <2  s by iterating the mirror shape at the speed of OCT B-scans rather than volumes. Also, we contrasted ∼ 7 ° ∼7° field-of-view OCTA angiograms acquired in the periphery with and without WSAO correction. On average, WSAO improved ...

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    13. Wide-field retinal optical coherence tomography with wavefront sensorless adaptive optics for enhanced imaging of targeted regions

      Wide-field retinal optical coherence tomography with wavefront sensorless adaptive optics for enhanced imaging of targeted regions

      The peripheral retina of the human eye offers a unique opportunity for assessment and monitoring of ocular diseases. We have developed a novel wide-field (>70°) optical coherence tomography system (WF-OCT) equipped with wavefront sensorless adaptive optics (WSAO) for enhancing the visualization of smaller (<25°) targeted regions in the peripheral retina. We iterated the WSAO algorithm at the speed of individual OCT B-scans (~20 ms) by using raw spectral interferograms to calculate the optimization metric. Our WSAO approach with a 3 mm beam diameter permitted primarily low- but also high- order peripheral wavefront correction in less than 10 seconds. In preliminary ...

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    14. Segmentation guided registration of wide field-of-view retinal optical coherence tomography volumes

      Segmentation guided registration of wide field-of-view retinal optical coherence tomography volumes

      Patient motion artifacts are often visible in densely sampled or large wide field-of-view (FOV) retinal optical coherence tomography (OCT) volumes. A popular strategy for reducing motion artifacts is to capture two orthogonally oriented volumetric scans. However, due to larger volume sizes, longer acquisition times, and corresponding larger motion artifacts, the registration of wide FOV scans remains a challenging problem. In particular, gaps in data acquisition due to eye motion, such as saccades, can be significant and their modeling becomes critical for successful registration. In this article, we develop a complete computational pipeline for the automatic motion correction and accurate registration ...

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    15. Needle Depth and Big-Bubble Success in Deep Anterior Lamellar Keratoplasty: An Ex Vivo Microscope-Integrated OCT Study

      Needle Depth and Big-Bubble Success in Deep Anterior Lamellar Keratoplasty: An Ex Vivo Microscope-Integrated OCT Study

      Purpose: To examine big-bubble (BB) formation success rates in deep anterior lamellar keratoplasty (DALK) at various corneal depths using real-time guidance from swept-source, microscope-integrated optical coherence tomography (SS-MIOCT). Methods: The DALK procedure was performed ex vivo with 34 human donor corneoscleral buttons on pressurized artificial anterior chambers using the BB technique employed by Anwar and Teichmann. We inserted a needle under controlled ex vivo conditions to corneal depths ranging from 40% to ≥90% using real-time guidance from SS-MIOCT and injected air. BB success was then determined for each injection. Results: The average needle depth for successful full BB formation was ...

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    16. Segmentation Based Sparse Reconstruction of Optical Coherence Tomography Images

      Segmentation Based Sparse Reconstruction of Optical Coherence Tomography Images

      We demonstrate the usefulness of utilizing a segmentation step for improving the performance of sparsity based image reconstruction algorithms. In specific, we will focus on retinal optical coherence tomography (OCT) reconstruction and propose a novel segmentation based reconstruction framework with sparse representation, termed segmentation based sparse reconstruction (SSR). The SSR method uses automatically segmented retinal layer information to construct layer-specific structural dictionaries. In addition, the SSR method efficiently exploits patch similarities within each segmented layer to enhance the reconstruction performance. Our experimental results on clinical-grade retinal OCT images demonstrate the effectiveness and efficiency of the proposed SSR method for both ...

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    17. Length-adaptive graph search for automatic segmentation of pathological features in optical coherence tomography images

      Length-adaptive graph search for automatic segmentation of pathological features in optical coherence tomography images

      We introduce a metric in graph search and demonstrate its application for segmenting retinal optical coherence tomography (OCT) images of macular pathology. Our proposed “adjusted mean arc length” (AMAL) metric is an adaptation of the lowest mean arc length search technique for automated OCT segmentation. We compare this method to Dijkstra’s shortest path algorithm, which we utilized previously in our popular graph theory and dynamic programming segmentation technique. As an illustrative example, we show that AMAL-based length-adaptive segmentation outperforms the shortest path in delineating the retina/vitreous boundary of patients with full-thickness macular holes when compared with expert manual ...

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    18. Impact of Microscope-Integrated OCT on Ophthalmology Resident Performance of Anterior Segment Surgical Maneuvers in Model Eyes

      Impact of Microscope-Integrated OCT on Ophthalmology Resident Performance of Anterior Segment Surgical Maneuvers in Model Eyes

      Purpose : The integration of swept-source optical coherence tomography (SS-OCT) into the operating microscope enables real-time, tissue-level three-dimensional (3D) imaging to aid in ophthalmic microsurgery. In this prospective randomized controlled study, we evaluated the impact of SS microscope-integrated OCT (MI-OCT) on ophthalmology residents' performance of ophthalmic microsurgical maneuvers. Methods : Fourteen ophthalmology residents from a single institution were stratified by year of training and randomized to perform four anterior segment surgical maneuvers on porcine eyes with (MI-OCT+) or without (MI-OCT−) direct intraoperative OCT guidance. Subsequently, both groups repeated the same maneuvers without MI-OCT feedback to test whether initial MI-OCT experience affected subsequent ...

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    19. Posterior Eye Shape Measurement With Retinal OCT Compared to MRI

      Posterior Eye Shape Measurement With Retinal OCT Compared to MRI

      Purpose : Posterior eye shape assessment by magnetic resonance imaging (MRI) is used to study myopia. We tested the hypothesis that optical coherence tomography (OCT), as an alternative, could measure posterior eye shape similarly to MRI. Methods : Macular spectral-domain OCT and brain MRI images previously acquired as part of the Singapore Epidemiology of Eye Diseases study were analyzed. The right eye in the MRI and OCT images was automatically segmented. Optical coherence tomography segmentations were corrected for optical and display distortions requiring biometry data. The segmentations were fitted to spheres and ellipsoids to obtain the posterior eye radius of curvature ( R ...

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    20. Repeatability of Choroidal Thickness Measurements on Enhanced Depth Imaging OCT using Different Posterior Boundaries

      Repeatability of Choroidal Thickness Measurements on Enhanced Depth Imaging OCT using Different Posterior Boundaries

      Purpose To assess the reliability of manual choroidal thickness measurements by comparing different posterior boundary definitions of the choroidal-scleral junction on enhanced depth imaging optical coherence tomography (EDI-OCT). Design Reliability analysis Methods Two graders marked the choroidal-scleral junction with segmentation software using different posterior boundaries: 1) the outer border of the choroidal vessel lumen, 2) the outer border of the choroid stroma, and 3) the inner border of the sclera, to measure the vascular choroidal thickness (VCT), stromal choroidal thickness (SCT), and total choroidal thickness (TCT), respectively. Measurements were taken at 0.5 mm intervals from 1.5 mm nasal ...

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    21. Postdoctoral Research Fellowship in Clinical Applications of Image Processing at Duke University

      Postdoctoral Research Fellowship in Clinical Applications of Image Processing at Duke University

      Immediate opening at Duke University Biomedical Engineering Department for a Postdoctoral Research Associate interested in interdisciplinary applications of image analysis and computer vision with emphasis on applications in Optical Coherence Tomography (OCT) and adaptive optics (AO) imaging. Postdoc will be supervised by Prof. Sina Farsiu ( http://people.duke.edu/~sf59/ ) in collaboration with Prof. Joseph A. Izatt ( http://bme.duke.edu/faculty/joseph-izatt ) and other senior professors from Duke University School of Medicine. The candidate must have a demonstrated strong background in image processing as evidenced by publication of papers in high-impact peer-reviewed journals. Programming skill in MATLAB is required ...

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    22. Postdoctoral Research Fellowship in ophthalmic adaptive optics optical coherence tomography imaging at Duke University

      Postdoctoral Research Fellowship in ophthalmic adaptive optics optical coherence tomography imaging at Duke University

      Immediate opening at Duke University Biomedical Engineering Department for a Postdoctoral Research Associate interested in development of novel fast and high-resolution ophthalmic adaptive optics (AO) and Optical Coherence Tomography (OCT) imaging systems. Postdoc will be supervised by Prof. Joseph A. Izatt ( http://bme.duke.edu/faculty/joseph-izatt ) in collaboration with Prof. Sina Farsiu ( http://people.duke.edu/~sf59/ ). Multiple previous PhD students and postdocs from this team are now faculty members in top universities around the world. Requirement: PhD in EE, BME, or CS. The candidate must have a demonstrated strong background in optical design and photonics imaging as evidenced ...

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    23. Analyzing spatial correlations in tissue using angle-resolved low coherence interferometry measurements guided by co-located optical coherence tomography

      Analyzing spatial correlations in tissue using angle-resolved low coherence interferometry measurements guided by co-located optical coherence tomography

      Angle-resolved low coherence interferometry (a/LCI) is an optical technique used to measure nuclear morphology in situ . However, a/LCI is not an imaging modality and can produce ambiguous results when the measurements are not properly oriented to the tissue architecture. Here we present a 2D a/LCI system which incorporates optical coherence tomography imaging to guide the measurements. System design and characterization are presented, along with example cases which demonstrate the utility of the combined measurements. In addition, future development and applications of this dual modality approach are discussed.

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    24. Intrasurgical Human Retinal Imaging With Manual Instrument Tracking Using a Microscope-Integrated Spectral-Domain Optical Coherence Tomography Device

      Intrasurgical Human Retinal Imaging With Manual Instrument Tracking Using a Microscope-Integrated Spectral-Domain Optical Coherence Tomography Device

      Purpose: : To characterize the first in-human intraoperative imaging using a custom prototype spectral-domain microscope-integrated optical coherence tomography (MIOCT) device during vitreoretinal surgery with instruments in the eye. Methods: : Under institutional review board approval for a prospective intraoperative study, MIOCT images were obtained at surgical pauses with instruments held static in the vitreous cavity and then concurrently with surgical maneuvers. Postoperatively, MIOCT images obtained at surgical pauses were compared with images obtained with a high-resolution handheld spectral-domain OCT (HHOCT) system with objective endpoints, including acquisition of images acceptable for analysis and identification of predefined macular morphologic or pathologic features. Results: : Human ...

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    1-24 of 78 1 2 3 4 »
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    1. (78 articles) Duke University
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    Automatic segmentation of seven retinal layers in SDOCT images congruent with expert manual segmentation Integration of a Spectral Domain Optical Coherence Tomography System into a Surgical Microscope for Intraoperative Imaging Sparsity based denoising of spectral domain optical coherence tomography images Corneal biometry from volumetric SDOCT and comparison with existing clinical modalities Feature Of The Week 6/24/12: Duke University Researchers Develop Techniques for Denoising OCT Images And Publically Share Their Software Postdoctoral Research Fellowship in ophthalmic adaptive optics optical coherence tomography imaging at Duke University Postdoctoral Research Fellowship in Clinical Applications of Image Processing at Duke University Normative data and minimally detectable change for inner retinal layer thicknesses using a semi-automated OCT image segmentation pipeline Acoustic Radiation Force Optical Coherence Elastography Advances in Optical Coherence Tomography and Confocal Laser Endomicroscopy in Pulmonary Diseases To Evaluate the Effect of Chronic Obstructive Pulmonary Disease on Retinal and Choroidal Thicknesses Measured by Optical Coherence Tomography Neovascularized Best Disease in Child: Contribution of Optical Coherence Tomography Angiography