1. Articles from larry kagemann

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    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. Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography

      Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography

      Purpose To predict the development of glaucomatous visual field (VF) defects using Fourier-domain optical coherence tomography (FD-OCT) measurements at baseline visit. Design Multi-center longitudinal observational study. Glaucoma suspects and pre-perimetric glaucoma participants in the Advanced Imaging for Glaucoma Study. Methods The optic disc, the peripapillary retinal nerve fiber layer (NFL), and macular ganglion cell complex (GCC) were imaged with FD-OCT VF was assessed every 6 months. Conversion to perimetric glaucoma was defined by VF pattern standard deviation (PSD) or glaucoma hemifield test (GHT) outside normal limits on 3 consecutive tests. Hazard ratios were calculated with the Cox proportional hazard model ...

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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. Repeatability of in vivo 3D lamina cribrosa microarchitecture using adaptive optics spectral domain optical coherence tomography

      Repeatability of in vivo 3D lamina cribrosa microarchitecture using adaptive optics spectral domain optical coherence tomography

      We demonstrate the repeatability of lamina cribrosa (LC) microarchitecture for in vivo 3D optical coherence tomography (OCT) scans of healthy, glaucoma suspects, and glaucomatous eyes. Eyes underwent two scans using a prototype adaptive optics spectral domain OCT (AO-SDOCT) device from which LC microarchitecture was semi-automatically segmented. LC segmentations were used to quantify pore and beam structure through several global microarchitecture parameters. Repeatability of LC microarchitecture was assessed qualitatively and quantitatively by calculating parameter imprecision. For all but one parameters (pore volume) measurement imprecision was <4.7% of the mean value, indicating good measurement reproducibility. Imprecision ranged between 27.3% and ...

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    8. 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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    9. Characterisation of Schlemm's canal cross-sectional area

      Characterisation of Schlemm's canal cross-sectional area

      Purpose To compare three methods of Schlemm's canal (SC) cross-sectional area (CSA) measurement. Methods Ten eyes (10 healthy volunteers) were imaged three times using spectral-domain optical coherence tomography (Cirrus HD-OCT, Zeiss, Dublin, California, USA). Aqueous outflow vascular structures and SC collector channel ostia were used as landmarks to identify a reference location within the limbus. SC CSA was assessed within a 1 mm segment (±15 frames of the reference, 31 frames in all) by three techniques. (1) Using a random number table, SC CSA in five random frames from the set of 31 surrounding the reference were measured and ...

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    10. 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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    11. 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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    12. Automated lamina cribrosa microstructural segmentation in optical coherence tomography scans of healthy and glaucomatous eyes

      Automated lamina cribrosa microstructural segmentation in optical coherence tomography scans of healthy and glaucomatous eyes

      We demonstrate an automated segmentation method for in-vivo 3D optical coherence tomography (OCT) imaging of the lamina cribrosa (LC). Manual segmentations of coronal slices of the LC were used as a gold standard in parameter selection and evaluation of the automated technique. The method was validated using two prototype OCT devices; each had a subject cohort including both healthy and glaucomatous eyes. Automated segmentation of in-vivo 3D LC OCT microstructure performed comparably to manual segmentation and is useful for investigative research and in clinical quantification of the LC.

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    13. 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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    14. 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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    15. 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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    16. 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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    17. 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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    18. 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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    19. Alignment of 3-D Optical Coherence Tomography Scans to Correct Eye Movement Using a Particle Filtering

      Alignment of 3-D Optical Coherence Tomography Scans to Correct Eye Movement Using a Particle Filtering

      Eye movement artifacts occurring during 3-D optical coherence tomography (OCT) scanning is a well-recognized problem that may adversely affect image analysis and interpretation. A particle filtering algorithm is presented in this paper to correct motion in a 3-D dataset by considering eye movement as a target tracking problem in a dynamic system. The proposed particle filtering algorithm is an independent 3-D alignment approach, which does not rely on any reference image. 3-D OCT data is considered as a dynamic system, while the location of each A-scan is represented by the state space. A particle set is used to approximate the ...

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    20. Volumetric quantification of in vitro sonothrombolysis with microbubbles using high-resolution optical coherence tomography

      Volumetric quantification of in vitro sonothrombolysis with microbubbles using high-resolution optical coherence tomography

      Several in vitro and in vivo studies have established accelerated thrombolysis using ultrasound (US) induced microbubble (MB) cavitation. However, the mechanisms underlying MB mediated sonothrombolysis are still not completely elucidated. We performed three-dimensional (3-D) volumetric optical coherence tomography (OCT) imaging before and after the application of contrast US to thrombus. The most dramatic reduction in clot volume was observed with US + MB + recombinant tissue plasminogen activator (rt-PA). Thrombus surface erosion in this group on the side of the thrombus exposed to MB and ultrasound was evident on the OCT images. This technique may assist in clarifying the mechanisms underlying sonothrombolysis ...

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    21. 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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    22. Morphometric Analysis of Aqueous Humor Outflow Structures with Spectral Domain Optical Coherence Tomography

      Morphometric Analysis of Aqueous Humor Outflow Structures with Spectral Domain Optical Coherence Tomography

      Purpose: To describe morphometric details of the human aqueous humor (AH) outflow microvasculature visualized with 360 degree virtual castings during active AH outflow in cadaver eyes and comparing these structures with corrosion casting studies. Methods: The conventional AH outflow pathways of donor eyes (N=7) and eyes in vivo (N=3) were imaged with spectral-domain optical coherence tomography (SD-OCT) and wide-bandwidth super luminescent diode array during active AH outflow. Digital image contrast was adjusted to isolate AH microvasculature and images were viewed in a 3D viewer. Additional eyes (N=3) were perfused with mock AH containing fluorescent tracer microspheres to ...

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    23. Optical Coherence Tomography as a Rapid, Accurate, Noncontact Method of Visualizing the Palisades of Vogt

      Optical Coherence Tomography as a Rapid, Accurate, Noncontact Method of Visualizing the Palisades of Vogt

      Purpose. This study explored the efficacy of optical coherence tomography (OCT) as a high-resolution, noncontact method for imaging the palisades of Vogt by correlating OCT and confocal microscopy images. Methods. Human limbal rims were acquired and imaged with OCT and confocal microscopy. The area of the epithelial basement membrane in each of these sets was digitally reconstructed, and the models were compared. Results. OCT identified the palisades within the limbus and exhibited excellent structural correlation with immunostained tissue imaged by confocal microscopy. Conclusions. OCT successfully identified the limbal palisades of Vogt that constitute the corneal epithelial stem cell niche. These ...

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    24. Optical Coherence Tomography: Recent Developments on Structural and Functional Imaging - Call For Papers

      Optical Coherence Tomography: Recent Developments on Structural and Functional Imaging - Call For Papers

      Optical coherence tomography (OCT) provides in vivo cross-sectional and coronal imaging of the ocular fundus and anterior segment. Since its introduction in 1991, OCT evolved not only in its technical basis, from time domain to spectral domain, but also in the field of application, from structure to function. Increased resolution and scanning speed allow OCT to deliver high-quality structural information in a few seconds from the start of the acquisition to the final volumetric scan displayed on a computer screen. OCT provides both qualitative information, such as structural changes during followup, and quantitative parameters, such as the full thickness of ...

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