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RefMoB, a Reflectivity Feature Model-Based Automated Method for Measuring Four Outer Retinal Hyperreflective Bands in Optical Coherence Tomography
摘要： PURPOSE. To validate a model-driven method (RefMoB) of automatically describing the four outer retinal hyperreflective bands revealed by spectral-domain optical coherence tomography (SDOCT), for comparison with histology of normal macula; to report thickness and position of bands, particularly band 2 (ellipsoid zone [EZ], commonly called IS/OS). METHODS. Foveal and superior perifoveal scans of seven SDOCT volumes of five individuals aged 28 to 69 years with healthy maculas were used (seven eyes for validation, five eyes for measurement). RefMoB determines band thickness and position by a multistage procedure that models reflectivities as a summation of Gaussians. Band thickness and positions were compared with those obtained by manual evaluators for the same scans, and compared with an independent published histological dataset. RESULTS. Agreement among manual evaluators was moderate. Relative to manual evaluation, RefMoB reported reduced thickness and vertical shifts in band positions in a band-specific manner for both simulated and empirical data. In foveal and perifoveal scans, band 1 was thick relative to the anatomical external limiting membrane, band 2 aligned with the outer one-third of the anatomical IS ellipsoid, and band 3 (IZ, interdigitation of retinal pigment epithelium and photoreceptors) was cleanly delineated. CONCLUSIONS. RefMoB is suitable for automatic description of the location and thickness of the four outer retinal hyperreflective bands. Initial results suggest that band 2 aligns with the outer ellipsoid, thus supporting its recent designation as EZ. Automated and objective delineation of band 3 will help investigations of structural biomarkers of dark-adaptation changes in aging.
关键词： age-related macular degeneration,retina,ellipsoid,segmentation,optical coherence tomography,photoreceptors,interdigitation,reflectivity,retinal pigment epithelium
更新于2025-09-23 15:23:52
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Retinal photoreceptor apoptosis is associated with impaired serum ionized calcium homeostasis in diabetic retinopathy: An in-vivo analysis
摘要： Purpose: The aim of this work was to study the association of serum ionized calcium with retinal photoreceptor apoptosis on spectral domain optical coherence tomography (SD-OCT) in diabetic retinopathy (DR). Methods: Sixty consecutive cases with Type 2 diabetes mellitus were categorized into three groups: no diabetic retinopathy; non-proliferative DR; proliferative DR. The eye with more severe form of the disease was considered. Twenty healthy controls were also included. Best corrected visual acuity (BCVA) was measured on logMAR scale. Retinal photoreceptor apoptosis was defined as disruption of retinal photoreceptor ellipsoid zone (EZ). Ellipsoid zone disruption was assessed using SD-OCT. Serum levels of total and ionized calcium were measured using standard protocol. Results: EZ disruption was found to be positively associated with serum total calcium and ionized calcium. Also, EZ disruption was found to be positively associated with logMAR BCVA. Conclusion: Increased serum ionized calcium induces retinal photoreceptor apoptosis resulting in increased EZ disruption in DR.
关键词： Ionized calcium,Retinal photoreceptor apoptosis,Diabetic retinopathy,Autophagy,Ellipsoid zone,Spectral-domain optical coherence tomography
更新于2025-09-23 15:23:52
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Algorithms for 3D Particles Characterization Using X-Ray Microtomography in Proppant Crush Test
摘要： We present image processing algorithms for a new technique of ceramic proppant crush resistance characterization. To obtain the images of the proppant material before and after the test we used X-ray microtomography. We propose a watershed-based unsupervised algorithm for segmentation of proppant particles, as well as a set of parameters for the characterization of 3D particle size, shape, and porosity. An effective approach based on central geometric moments is described. The approach is used for calculation of particles’ form factor, compactness, equivalent ellipsoid axes lengths, and lengths of projections to these axes. Obtained grain size distribution and crush resistance ?t the results of conventional test measured by sieves. However, our technique has a remarkable advantage over traditional laboratory method since it allows to trace the destruction at the level of individual particles and their fragments; it grants to analyze morphological features of ?nes. We also provide an example describing how the approach can be used for veri?cation of statistical hypotheses about the correlation between particles’ parameters and their crushing under load.
关键词： shape factor,axes of equivalent ellipsoid,geometric moments,watershed,invariants,matching of particles,unsupervised segmentation,compactness,porosity
更新于2025-09-23 15:21:21
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Disorganization of Retinal Inner Layers and Ellipsoid Zone Disruption Predict Visual Outcomes in Central Retinal Vein Occlusion
摘要： To assess the associations and predictive value of spectral-domain (SD) OCT inner and outer retinal structural parameters and visual acuity (VA) outcomes in macular edema (ME) secondary to central retinal vein occlusion (CRVO).
关键词： disorganization of retinal inner layers,visual acuity,ellipsoid zone disruption,macular edema,spectral-domain OCT,central retinal vein occlusion
更新于2025-09-23 15:21:01
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En Face Optical Coherence Tomography Imaging Ellipsoid Zone Regeneration in Laser-Induced and Solar Maculopathies
摘要： The purpose of the study was to analyze imaging findings in spectral domain en face optical coherence tomography (SD OCT) in patients with laser‐induced and solar maculopathies focusing on the possible regeneration of the ellipsoid zone. In a retrospective case series of 3 patients (4 eyes) with solar maculopathy and 2 patients (3 eyes) with laser‐induced maculopathy who underwent a comprehensive ocular examination, ellipsoid zone (EZ) was segmented from SD OCT data. Evaluation of EZ in en face OCT revealed a hyporeflective lesion surrounded by a hyperreflective border. The area of EZ alteration was measured manually in en face OCT. All patients showed partial EZ regeneration. Mean EZ alteration decreased from 0.12 mm2 (range: 0.05–0.32) at baseline to 0.07 mm2 (range: 0.01–0.22) at last follow‐up (?? = 0.018, mean follow‐up: 372 days; range: 115–592). Mean best visual acuity (BVA) improved from 20/36 at baseline to 20/30 (?? = 0.018). In conclusion, en face OCT imaging clearly delineated the area of EZ alteration in patients with laser‐induced and solar maculopathies. Follow-up showed significant reformation of the EZ as well as improvement of BVA.
关键词： optical coherence tomography,solar maculopathy,laser-induced maculopathy,ellipsoid zone,regeneration
更新于2025-09-12 10:27:22
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Inner Segment Remodeling and Mitochondrial Translocation in Cone Photoreceptors in Age-Related Macular Degeneration With Outer Retinal Tubulation
摘要： PURPOSE. To quantify impressions of mitochondrial translocation in degenerating cones and to determine the nature of accumulated material in the subretinal space with apparent inner segment (IS)-like features by examining cone IS ultrastructure. METHODS. Human donor eyes with advanced age-related macular degeneration (AMD) were screened for outer retinal tubulation (ORT) in macula-wide, high-resolution digital sections. Degenerating cones inside ORT (ORT cones) and outside ORT (non-ORT cones) from AMD eyes and unaffected cones in age-matched control eyes were imaged using transmission electron microscopy. The distances of mitochondria to the external limiting membrane (ELM), cone IS length, and cone IS width at the ELM were measured. RESULTS. Outer retinal tubulation and non-ORT cones lose outer segments (OS), followed by shortening of IS and mitochondria. In non-ORT cones, IS broaden. Outer retinal tubulation and non-ORT cone IS myoids become undetectable due to mitochondria redistribution toward the nucleus. Some ORT cones were found lacking IS and containing mitochondria in the outer fiber (between soma and ELM). Unlike long, thin IS mitochondria in control cones, ORT and non-ORT IS mitochondria are ovoid or reniform. Shed IS, some containing mitochondria, were found in the subretinal space. CONCLUSIONS. In AMD, macula cones exhibit loss of detectable myoid due to IS shortening in addition to OS loss, as described. Mitochondria shrink and translocate toward the nucleus. As reflectivity sources, translocating mitochondria may be detectable using in vivo imaging to monitor photoreceptor degeneration in retinal disorders. These results improve the knowledge basis for interpreting high-resolution clinical retinal imaging.
关键词： ellipsoid,outer retinal tubulation,age-related macular degeneration,histology,photoreceptors,cones,myoid,transmission electron microscopy,Müller cells
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Sheffield (2018.7.8-2018.7.11)] 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - New Theory for Unmixing ILL-Conditioned Hyperspectral Mixtures
摘要： Hyperspectral unmixing (HU), a blind source separation problem, aims at unambiguiously identifying the spectral signatures of the materials, as well as their abundances, from the measured hyperspectral mixtures. In real hyperspectral scenes, high correlation between the spectral signatures is commonly observed, making HU quite challenging. Although such ill-conditioning is critical for effective HU, it is often ignored in existing HU literature. To the best of our knowledge, existing preconditioning techniques, for reducing the condition number of the signature matrix, were developed based on the pure-pixel assumption, which can, however, be seriously violated in remote sensing. Under a relaxed purity assumption, with respect to the pure-pixel one, this paper proposes novel theory for unmixing ill-conditioned hyperspectral mixtures. Specifically, we exactly identify the John’s ellipsoid (i.e., the maximum ellipsoid inscribed in the convex hull of the hyperspectral data vectors) via split augmented Lagrangian shrinkage algorithm (SALSA), and transform this ellipsoid into an Euclidean ball. This transformation brings the data vectors into a new space wherein the corresponding material signature vectors form a regular simplex, which is a very strong prior information. Based on this prior, we design an HU criterion, and prove its perfect identifiability under a very mild sufficient condition. Then, we demonstrate the feasibility of realizing our criterion via non-convex optimization and guarantee a stationary point solution.
关键词： split augmented Lagrangian shrinkage algorithm,Hyperspectral unmixing,pure-pixel assumption,non-convex optimization,John’s ellipsoid
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Selecting Band Subsets from Hyperspectral Image Through a Novel Evolutionary-Based Strategy
摘要： Hyperspectral dimensionality reduction by optimal band selection attracts wide attention recently because a few pivotal and physically meaningful bands can not only represent the whole image cube without losing effectiveness but also mitigate the computational burden. In this paper, we construct an efficient searching strategy based on the clonal selection principle to optimize a geometry-based criterion named maximum ellipsoid volume (MEV). The main contributions are two-fold: 1) a subtle relationship that can accelerate the calculation of the criterion and 2) an evolutionary strategy to relieve the heavy computational burden of obtaining the desired bands from numerous quality candidates. The experimental result on a real hyperspectral data demonstrates that the proposed method is effective.
关键词： maximum ellipsoid volume,Band selection,hyperspectral image,clonal selection principle
更新于2025-09-09 09:28:46
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Weak Echo Detection from Single Photon Lidar Data Using a Rigorous Adaptive Ellipsoid Searching Algorithm
摘要： Single photon lidar (SPL) systems have great potential to be an effective tool for mapping due to their high data collection efficiency. However, the large number of false returns in SPL point clouds represents a huge challenge for the extraction of weak signal targets with low reflectivity or small cross sections. Numerous filtering methods have been proposed that attempt to effectively remove these noise points from the final point cloud model. However, weak signal points have similar characteristics to noise returns, and thus can be incorrectly eliminated as noise points during the filtering process. Herein, a novel voxel-spherical adaptive ellipsoid searching (VSAES) method is proposed, by which weak signal returns can be successfully retained while still removing a majority of the noise points. By employing this voxel-spherical (VS) model, our proposed method can simultaneously process a combined SPL dataset containing multiple flightlines, in which the noise density is unevenly distributed throughout the whole dataset. In addition, an improved adaptive ellipsoid searching (AES) method based on hypothesis testing is able to remove noise points more robustly than the originally described version. The experimental results show that the proposed method retains 89.1% of the weak signal point returns from electric power lines, which is a significant improvement over the performance of either to the original AES method (25.9%) or a histogram filtering based method (13.4%).
关键词： filtering,spherical voxels,single photon lidar,adaptive ellipsoid search
更新于2025-09-04 15:30:14
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An ellipsoid convex enhancement filter for detection of asymptomatic intracranial aneurysm candidates in CAD frameworks
摘要： Various kinds of enhancement filters have been developed in computer-aided diagnostic (CAD) frameworks for asymptomatic intracranial aneurysms in magnetic resonance angiography (MRA). However, many bending or branching portions on vessels are also enhanced by the conventional filters as false positives in 3.0 T MRA, which can visualize smaller vessels compared with 1.5 T MRA. To overcome this problem, this study focused on developing an ellipsoid convex enhancement (ECE) filter, which can selectively enhance aneurysms while reducing false positive contrasts on bending or branching portions on vessels, for detection of asymptomatic intracranial aneurysm candidates in CAD frameworks. The ECE filter was mathematically designed to enhance various convex regions in the intensity space such as convex aneurysms, in which the ratio of the shortest and longest diameters for aneurysms corresponds to the ratio of reciprocals of the square roots of the first and third eigenvalues of a Hessian matrix. The proposed ECE filter was evaluated by measuring an average contrast for false positive models and free-response receiver operating characteristic curves between two simple CAD frameworks using the ECE and conventional filters based on a leave-one-out-by-patient test. MRA images for thirty patients (male: 10, female: 20; age: 48–86 yr, mean: 69.2) with 31 unruptured aneurysms (longest diameter: 2.0–5.5 mm, mean: 3.7 mm) were selected for this study. The average contrast for false positive models was reduced by 51.4% using the ECE filter, compared with the conventional filter for the convex regions with ratios of the shortest and longest diameters less than 0.4. The number of false positives per case was decreased from 41.1 to 22.8 on average at a sensitivity of 87% by using the ECE filter. The ECE filter would be useful for boosting the performance of the CAD framework of asymptomatic intracranial aneurysms by providing higher contrast aneurysms and lower contrast false positives such as bending or branching portions on vessels.
关键词： unruptured intracranial aneurysm,ellipsoid convex enhancement (ECE) filter,magnetic resonance angiography (MRA),computer-aided diagnosis (CAD)
更新于2025-09-04 15:30:14