1. Articles from richard a. bilonick

    1-24 of 27 1 2 »
    1. Signal Normalization Reduces Image Appearance Disparity Among Multiple Optical Coherence Tomography Devices

      Signal Normalization Reduces Image Appearance Disparity Among Multiple Optical Coherence Tomography Devices

      Purpose : To assess the effect of the previously reported optical coherence tomography (OCT) signal normalization method on reducing the discrepancies in image appearance among spectral-domain OCT (SD-OCT) devices. Methods : Healthy eyes and eyes with various retinal pathologies were scanned at the macular region using similar volumetric scan patterns with at least two out of three SD-OCT devices at the same visit (Cirrus HD-OCT, Zeiss, Dublin, CA; RTVue, Optovue, Fremont, CA; and Spectralis, Heidelberg Engineering, Heidelberg, Germany). All the images were processed with the signal normalization. A set of images formed a questionnaire with 24 pairs of cross-sectional images from each ...

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    2. Virtual Averaging Making Nonframe-Averaged Optical Coherence Tomography Images Comparable to Frame-Averaged Images

      Virtual Averaging Making Nonframe-Averaged Optical Coherence Tomography Images Comparable to Frame-Averaged Images

      Purpose : Developing a novel image enhancement method so that nonframe-averaged optical coherence tomography (OCT) images become comparable to active eye-tracking frame-averaged OCT images. Methods : Twenty-one eyes of 21 healthy volunteers were scanned with noneye-tracking nonframe-averaged OCT device and active eye-tracking frame-averaged OCT device. Virtual averaging was applied to nonframe-averaged images with voxel resampling and adding amplitude deviation with 15-time repetitions. Signal-to-noise (SNR), contrast-to-noise ratios (CNR), and the distance between the end of visible nasal retinal nerve fiber layer (RNFL) and the foveola were assessed to evaluate the image enhancement effect and retinal layer visibility. Retinal thicknesses before and after processing ...

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    3. In Vivo Evaluation of White Matter Integrity and Anterograde Transport in Visual System After Excitotoxic Retinal Injury With Multimodal MRI and OCT

      In Vivo Evaluation of White Matter Integrity and Anterograde Transport in Visual System After Excitotoxic Retinal Injury With Multimodal MRI and OCT

      Purpose. Excitotoxicity has been linked to the pathogenesis of ocular diseases and injuries and may involve early degeneration of both anterior and posterior visual pathways. However, their spatiotemporal relationships remain unclear. We hypothesized that the effects of excitotoxic retinal injury (ERI) on the visual system can be revealed in vivo by diffusion tensor magnetic resonance imagining (DTI), manganese-enhanced magnetic resonance imagining (MRI), and optical coherence tomography (OCT). Methods. Diffusion tensor MRI was performed at 9.4 Tesla to monitor white matter integrity changes after unilateral N-methyl-D-aspartate (NMDA)-induced ERI in six Sprague-Dawley rats and six C57BL/6J mice. Additionally, four ...

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    4. Histogram Matching Extends Acceptable Signal Strength Range on Optical Coherence Tomography Images

      Histogram Matching Extends Acceptable Signal Strength Range on Optical Coherence Tomography Images

      Purpose. We minimized the influence of image quality variability, as measured by signal strength (SS), on optical coherence tomography (OCT) thickness measurements using the histogram matching (HM) method. Methods. We scanned 12 eyes from 12 healthy subjects with the Cirrus HD-OCT device to obtain a series of OCT images with a wide range of SS (maximal range, 1–10) at the same visit. For each eye, the histogram of an image with the highest SS (best image quality) was set as the reference. We applied HM to the images with lower SS by shaping the input histogram into the reference ...

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    5. In Vivo Three-Dimensional Characterization of the Healthy Human Lamina Cribrosa with Adaptive Optics Spectral-Domain Optical Coherence Tomography

      In Vivo Three-Dimensional Characterization of the Healthy Human Lamina Cribrosa with Adaptive Optics Spectral-Domain Optical Coherence Tomography

      Purpose: To characterize the in vivo 3D lamina cribrosa (LC) microarchitecture of healthy eyes using adaptive optics spectral-domain optical coherence tomography (AO-SDOCT). Methods: One randomly selected eye from each of 18 healthy subjects was scanned with Cirrus HD-OCT and AO-SDOCT centered on the optic nerve head. LC microarchitecture, imaged by the later device, was semi-automatically segmented and quantified for connective tissue volume fraction (CTVF), beam thickness, pore diameter, pore area and pore aspect ratio. The LC was assessed in central and peripheral regions of equal areas, quadrants and with depth. A linear mixed-effects model weighted by the fraction of visible ...

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    6. Reproducibility of In-Vivo OCT Measured Three-Dimensional Human Lamina Cribrosa Microarchitecture

      Reproducibility of In-Vivo OCT Measured Three-Dimensional Human Lamina Cribrosa Microarchitecture

      Purpose To determine the reproducibility of automated segmentation of the three-dimensional (3D) lamina cribrosa (LC) microarchitecture scanned in-vivo using optical coherence tomography (OCT). Methods Thirty-nine eyes (8 healthy, 19 glaucoma suspects and 12 glaucoma) from 49 subjects were scanned twice using swept-source (SS−) OCT in a 3.5×3.5×3.64 mm (400×400×896 pixels) volume centered on the optic nerve head, with the focus readjusted after each scan. The LC was automatically segmented and analyzed for microarchitectural parameters, including pore diameter, pore diameter standard deviation (SD), pore aspect ratio, pore area, beam thickness, beam thickness SD, and ...

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    7. Gold nanorods as a contrast agent for Doppler optical coherence tomography

      Gold nanorods as a contrast agent for Doppler optical coherence tomography

      PURPOSE: To investigate gold nanorods (GNRs) as a contrast agent to enhance Doppler optical coherence tomography (OCT) imaging of the intrascleral aqueous humor outflow. METHODS: A serial dilution of GNRs was scanned with a spectral-domain OCT device (Bioptigen, Durham, NC) to visualize Doppler signal. Doppler measurements using GNRs were validated using a controlled flow system. To demonstrate an application of GNR enhanced Doppler, porcine eyes were perfused at constant pressure with mock aqueous alone or 1.0×1012 GNR/mL mixed with mock aqueous. Twelve Doppler and volumetric SD-OCT scans were obtained from the limbus in a radial fashion incremented ...

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    8. In Vivo Lamina Cribrosa Micro-Architecture in Healthy and Glaucomatous Eyes as Assessed by Optical Coherence Tomography

      In Vivo Lamina Cribrosa Micro-Architecture in Healthy and Glaucomatous Eyes as Assessed by Optical Coherence Tomography

      Purpose. The lamina cribrosa (LC) is a prime location of glaucomatous damage. The purpose of this study was to compare LC 3-dimensional micro-architecture between healthy and glaucomatous eyes in vivo by using optical coherence tomography (OCT). Methods. Sixty-eight eyes (19 healthy and 49 glaucomatous) from 47 subjects were scanned in a 3.5 × 3.5 × 3.64-mm volume (400 × 400 × 896 pixels) at the optic nerve head by using swept-source OCT. The LC micro-architecture parameters were measured on the visible LC by an automated segmentation algorithm. The LC parameters were compared to diagnosis and visual field mean deviation (VF MD ...

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    9. In-Vivo Lamina Cribrosa Microarchitecture in Healthy and Glaucomatous Eyes as Assessed by Optical Coherence Tomography

      In-Vivo Lamina Cribrosa Microarchitecture in Healthy and Glaucomatous Eyes as Assessed by Optical Coherence Tomography

      Purpose: Lamina cribrosa (LC) is a leading location of glaucomatous damage. The purpose of this study is to compare LC 3-dimensional microarchitecture between healthy and glaucomatous eyes in-vivo using optical coherence tomography (OCT). Methods: Sixty-eight eyes (19 healthy and 49 glaucomatous) from 47 subjects were scanned in a 3.5x3.5x3.64mm volume (400x400x896 pixels) at the optic nerve head using swept-source OCT. The LC microarchitecture parameters were measured on the visible LC by an automated segmentation algorithm. The LC parameters were compared to diagnosis and visual field mean deviation (MD) using a linear mixed effects model accounting for age ...

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    10. Signal Normalization Reduces Systematic Measurement Differences Between Spectral Domain Optical Coherence Tomography Devices

      Signal Normalization Reduces Systematic Measurement Differences Between Spectral Domain Optical Coherence Tomography Devices

      Purpose: To test the effect of a novel signal normalization method for reducing systematic optical coherence tomography (OCT) measurement differences among multiple spectral-domain (SD-) OCT devices. Methods: One hundred and nine eyes from 59 subjects were scanned with two SD-OCT devices (Cirrus and RTVue) at the same visit. OCT image data were normalized to match their signal characteristics between the devices. To compensate signal strength differences, a custom high dynamic range (HDR) processing was also applied only to images with substantially lower signal strength. Global mean peripapillary RNFL thicknesses were then measured automatically from all images using custom segmentation software ...

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    11. Individual A-scan Signal Normalization Between Two Spectral Domain Optical Coherence Tomography Devices

      Individual A-scan Signal Normalization Between Two Spectral Domain Optical Coherence Tomography Devices

      Purpose: To develop a method to normalize optical coherence tomography (OCT) signal profiles from two spectral-domain (SD-) OCT devices so that the comparability between devices increases. Methods: Twenty-one eyes from 14 healthy and 7 glaucoma subjects were scanned with two SD-OCT devices on the same day with equivalent cube scan patterns centered on the fovea (Cirrus HD-OCT, Carl Zeiss Meditec, Dublin, CA; and RTVue, Optovue, Fremont, CA). Foveola positions were manually selected and used as the center for registration of the corresponding images. A-scan signals were sampled 1.8 mm from the foveola in the temporal, superior, nasal and inferior ...

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    12. Three-Dimensional Spectral-Domain Optical Coherence Tomography Data Analysis for Glaucoma Detection

      Three-Dimensional Spectral-Domain Optical Coherence Tomography Data Analysis for Glaucoma Detection

      Purpose To develop a new three-dimensional (3D) spectral-domain optical coherence tomography (SD-OCT) data analysis method using a machine learning technique based on variable-size super pixel segmentation that efficiently utilizes full 3D dataset to improve the discrimination between early glaucomatous and healthy eyes. Methods 192 eyes of 96 subjects (44 healthy, 59 glaucoma suspect and 89 glaucomatous eyes) were scanned with SD-OCT. Each SD-OCT cube dataset was first converted into 2D feature map based on retinal nerve fiber layer (RNFL) segmentation and then divided into various number of super pixels. Unlike the conventional super pixel having a fixed number of points ...

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    13. High Dynamic Range (HDR) Imaging Concept Based Signal Enhancement Method Reduced the Optical Coherence Tomography (OCT) Measurement Variability

      High Dynamic Range (HDR) Imaging Concept Based Signal Enhancement Method Reduced the Optical Coherence Tomography (OCT) Measurement Variability

      Purpose: To develop and test a novel signal enhancement method for optical coherence tomography (OCT) images based on the high dynamic range (HDR) processing concept. Methods: Three virtual channels, which represent low, medium, and high signal components, were produced for each OCT signal dataset. The dynamic range of each signal component was normalized to the full gray scale range. Finally, the three components were recombined into one image using various weights. Fourteen eyes of 14 healthy volunteers were scanned multiple times using time-domain (TD-) OCT before and while preventing blinking in order to produce a wide variety of signal strength ...

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    14. Inflammatory response to intravitreal injection of gold nanorods

      Inflammatory response to intravitreal injection of gold nanorods

      Aim To evaluate the utility of gold nanorods (AuNRs) as a contrast agent for ocular optical coherence tomography (OCT). Methods Mice were intravitreally injected with sterile AuNRs coated with either poly(strenesulfate) (PSS-AuNRs) or anti-CD90.2 antibodies (Ab-AuNRs), and imaged using OCT. After 24 h, eyes were processed for transmission electron microscopy or rendered into single cell suspensions for flow cytometric analysis to determine absolute numbers of CD45 + leukocytes and subsets (T cells, myeloid cells, macrophages, neutrophils). Generalised estimation equations were used to compare cell counts between groups. Results PSS-AuNRs and Ab-AuNRs were visualised in the vitreous 30 min and ...

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    15. Glaucoma discrimination of segmented cirrus spectral domain optical coherence tomography (SD-OCT) macular scans

      Glaucoma discrimination of segmented cirrus spectral domain optical coherence tomography (SD-OCT) macular scans

      Aims To evaluate the glaucoma discriminating ability of macular retinal layers as measured by spectral domain optical coherence tomography (SD-OCT). Methods Healthy, glaucoma suspect and glaucomatous subjects had a comprehensive ocular examination, visual field testing and SD-OCT imaging (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, California, USA) in the macular and optic nerve head regions. OCT macular scans were segmented into macular nerve fibre layer (mNFL), ganglion cell layer with inner plexiform layer (GCIP), ganglion cell complex (GCC) (composed of mNFL and GCIP), outer retinal complex and total retina. Glaucoma discriminating ability was assessed using the area under the receiver operator ...

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    16. Comparison of Retinal Nerve Fiber Layer Thickness Measurement Bias and Imprecision Across Three Spectral-Domain Optical Coherence Tomography Devices

      Comparison of Retinal Nerve Fiber Layer Thickness Measurement Bias and Imprecision Across Three Spectral-Domain Optical Coherence Tomography Devices

      Purpose: To compare retinal nerve fiber layer (RNFL) bias and imprecision amongst three spectral-domain optical coherence tomographs (SD-OCT). Methods: 152 eyes of 83 subjects (96 healthy and 56 glaucomatous eyes) underwent peripapillary RNFL imaging using at least 2 of the following 3 SD-OCT devices on the same day: Cirrus HD-OCT (optic nerve head (ONH) cube 200x200 protocol), RTVue-100 (ONH protocol (12 radial lines and 13 concentric circles), and 3D OCT-1000 (3D Scan 256x256 protocol). Calibration equations, bias and imprecision of RNFL measurements were calculated using structural equation models. Results: The calibration equations for healthy and glaucoma RNFL thickness measurements among ...

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    17. Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error

      Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error
      Purpose Commercial optical coherence tomography (OCT) systems use global signal quality indices to quantify scan quality. Signal quality can vary throughout a scan, contributing to local retinal nerve fibre layer segmentation errors (SegE). The purpose of this study was to develop an automated method, using local scan quality, to predict SegE. Methods Good-quality (global signal strength (SS)≥6; manufacturer specification) peripapillary circular OCT scans (fast retinal nerve fibre layer scan protocol; Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA) were obtained from 6 healthy, 19 glaucoma-suspect and 43 glaucoma subjects. Scans were grouped based on SegE. Quality index (QI) values ...
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    18. Retinal nerve fibre layer and visual function loss in glaucoma: the tipping point

      Retinal nerve fibre layer and visual function loss in glaucoma: the tipping point
      Aims To determine the retinal nerve fibre layer (RNFL) thickness at which visual field (VF) damage becomes detectable and associated with structural loss. Methods In a prospective cross-sectional study, 72 healthy and 40 glaucoma subjects (one eye per subject) recruited from an academic institution had VF examinations and spectral domain optical coherence tomography (SD-OCT) optic disc cube scans (Humphrey field analyser and Cirrus HD-OCT, respectively). Comparison of global mean and sectoral RNFL thicknesses with VF threshold values showed a plateau of threshold values at high RNFL thicknesses and a sharp decrease at lower RNFL thicknesses. A ‘broken stick’ statistical model ...
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    19. Optic Nerve Crushed Mice Followed Longitudinally with Spectral Domain Optical Coherence Tomography

      Optic Nerve Crushed Mice Followed Longitudinally with Spectral Domain Optical Coherence Tomography
      Purpose: To investigate the longitudinal effect of optic nerve crush injury in mice by measuring retinal thickness with spectral-domain optical coherence tomography (SD-OCT). Methods: Optic nerves of one eye from each C57Bl/6 mouse were crushed under direct visualization for 3 seconds, 1 mm posterior to the globe. The optic nerve head (ONH) was imaged with SD-OCT (1.5x1.5x2.0 mm scan; Bioptigen, Durham, NC) prior to the surgical intervention and repeated subsequently for up to 32 days post-injury. A cohort of mice not exposed to the nerve crush procedure served as control. En face SD-OCT images were used ...
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    20. Reproducibility of Spectral-Domain Optical Coherence Tomography Total Retinal Thickness Measurements in Mice

      Reproducibility of Spectral-Domain Optical Coherence Tomography Total Retinal Thickness Measurements in Mice
      Purpose: To test the reproducibility of total retinal thickness (TRT) measurements in mice using spectral-domain optical coherence tomography (SD-OCT). Methods: C57Bl/6 mice were anesthetized and three repeated volumetric images were acquired in both eyes with SD-OCT (250x250x1024 samplings, centered on the optic nerve head (ONH); Bioptigen, Inc, Durham, NC). Mice were repositioned in between each scan. TRT was automatically measured within a sampling band of retinal thickness with radii of 55-70 pixels, centered on the ONH, using custom segmentation software. The first volumetric image acquired in a given eye was used to register the remaining two SD-OCT images by ...
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    21. Identification and Assessment of Schlemm's Canal by Spectral Domain Optical Coherence Tomography

      Identification and Assessment of Schlemm's Canal by Spectral Domain Optical Coherence Tomography
      Purpose: Measurements of human Schlemm's canal (SC) have been limited to histological sections. The purpose of this study was to demonstrate non-invasive measurements of aqueous outflow (AO) structures in the human eye, examining regional variation in cross-sectional SC areas (on/off collector channel (CC) ostia (SC/CC), and nasal/temporal) in the eyes of living humans. Methods: SC was imaged by spectral-domain optical coherence tomography (SD-OCT, Bioptigen Inc, USA) with a 200 nm bandwidth light source (SuperLum LTD., Ireland). Both eyes of 21 healthy subjects and 1 glaucomatous eye of 3 subjects were imaged nasally and temporally. Contrast and ...
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    22. Retinal Nerve Fiber Layer Thickness Measurement Comparability between Time Domain Optical Coherence Tomography (OCT) and Spectral Domain OCT

      Purpose: Time domain optical coherence tomography (TD-OCT) has been used commonly in clinical practice, producing a large inventory of circular scan data for retinal nerve fiber layer (RNFL) assessment. Spectral domain OCT (SD-OCT) produces three dimensional (3D) data volumes. The purpose of this study was to create a robust technique that makes TD-OCT circular scan RNFL thickness measurements comparable with those from 3D SD-OCT volumes. Methods: Eleven eyes of 11 healthy subjects and 7 eyes of 7 glaucoma subjects were enrolled. Each eye was scanned using 1 centered and 8 displaced TD-OCT scanning circles. One 3D SD-OCT cube scan was ...
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    23. Retinal Nerve Fiber Layer Thickness Measurement Reproducibility Improved with Spectral Domain Optical Coherence Tomography

      Background/aims: To investigate retinal nerve fiber layer (RNFL) thickness measurement reproducibility using conventional time-domain optical coherence tomography (TD-OCT) and spectral-domain OCT (SD-OCT), and to evaluate two methods defining the optic nerve head (ONH) centering: centered each time (CET) vs. centered once (CO), in terms of RNFL thickness measurement variability on SD-OCT. Methods: Twenty-seven eyes (14 healthy subjects) had 3 circumpapillary scans with TD-OCT and 3 raster scans (three-dimensional or 3D image data) around ONH with SD-OCT. SD-OCT images were analyzed in two ways: 1) CET: ONH center was defined on each image separately, and 2) CO: ONH center was ...
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    24. Effects of Age on Optical Coherence Tomography Measurements of Healthy Retinal Nerve Fiber Layer, Macula, and Optic Nerve Head

      Purpose: To determine the effects of age on global and sectoral peripapillary retinal nerve fiber layer (RNFL), macular thicknesses, and optic nerve head (ONH) parameters in healthy subjects using optical coherence tomography (OCT). Design: Retrospective, cross-sectional observational study. Participants: A total of 226 eyes from 124 healthy subjects were included. Methods: Healthy subjects were scanned using the Fast RNFL, Fast Macula, and Fast ONH scan patterns on a Stratus OCT (Carl Zeiss Meditec, Dublin, CA). All global and sectoral RNFL and macular parameters and global ONH parameters were modeled in terms of age using linear mixed effects models. Normalized slopes ...
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    1. (27 articles) University of Pittsburgh
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    Identification and Assessment of Schlemm's Canal by Spectral Domain Optical Coherence Tomography Optic Nerve Crushed Mice Followed Longitudinally with Spectral Domain Optical Coherence Tomography Retinal nerve fibre layer and visual function loss in glaucoma: the tipping point Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error Comparison of Retinal Nerve Fiber Layer Thickness Measurement Bias and Imprecision Across Three Spectral-Domain Optical Coherence Tomography Devices Indiana University Receives NIH Grant for Imaging Spatial and Temporal Dynamics of Retinal Ganglion Cells University of Houston Receives NIH Grant for Structural and Molecular Phenotyping of Embryonic Development Through Multi-Modal Optical Imaging. Massachusetts Institute of Technology Receives NIH Grant for Novel Optical Diagnostics with Optical Coherence Tomography Yale University Receives a NIH Grant for Xenopus As A Model System for Hydrocephaly and Ependymal Ciliogenesis University of Minnesota Receives NIH Grant for Optical Imaging of Neural Activity Based on Lorentz Effect Skin Imaging to Inform Laser Treatments Diabetes and Fundus OCT: 1st Edition (Textbook)