1. All Articles

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    1. Direct inverse linearization of piezoelectric actuator’s initial loading curve and its applications in full-field optical coherence tomography (FF-OCT)

      Direct inverse linearization of piezoelectric actuator’s initial loading curve and its applications in full-field optical coherence tomography (FF-OCT)

      Abstract Piezoelectric actuator (PEA) has become popular in spectroscopic optical coherence tomography (SOCT) as it can provide depth dependent spectra with sub‐nanometer positioning resolution. However, the inherent hysteresis of the PEA introduces unwanted distortions to the obtained spectra and image. OCT imaging can be completed during the first forward motion of the PEA, i.e., the initial loading curve (ILC). Therefore, this paper proposes a feedforward hysteresis compensation method for the linearization of the ILC, aiming at improving the spectroscopic and imaging accuracy of OCT without any feedback on the PEA’s displacement or feedback controllers. A polynomial operator ...

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      Mentions: Sheng-Lung Huang
    2. Peripapillary Retinal and Choroidal Perfusion in Nonarteritic Ischemic Optic Neuropathy Using Optical Coherence Tomography Angiography

      Peripapillary Retinal and Choroidal Perfusion in Nonarteritic Ischemic Optic Neuropathy Using Optical Coherence Tomography Angiography

      SIGNIFICANCE Nonarteritic ischemic optic neuropathy (NAION) has been linked with vascular insufficiency, although the pathophysiology remains elusive. Optical coherence tomography angiography (OCTA) is a promising technology that noninvasively evaluates optic disc perfusion and that may help to characterize peripapillary vascular changes in NAION. PURPOSE This study aimed to evaluate peripapillary vascularity in NAION eyes and to compare it with fellow unaffected eyes and healthy control eyes using OCTA. METHODS In this cross-sectional study, OCTA of the optic nerve head was obtained in 10 nonacute unilateral NAION and 12 healthy age-matched controls using ZEISS Angioplex. Quantitative analysis of peripapillary retinal and ...

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    3. Reliability of foveal avascular zone measurements in eyes with retinal vein occlusion using optical coherence tomography angiography

      Reliability of foveal avascular zone measurements in eyes with retinal vein occlusion using optical coherence tomography angiography

      Background To evaluate the reliability of foveal avascular zone (FAZ) area measurements using optical coherence tomography angiography (OCTA) in eyes with retinal vein occlusion (RVO). Methods Twenty-five OCTA exams of patients with RVO were evaluated retrospectively. Three examiners performed manual measurements of the FAZ, and interrater and intrarater reliability were obtained. Results The intraclass correlation coefficient (ICC) for interrater reliability for individual measurements was 0.62 (moderate) with a 95% confidence interval (CI) of 0.40 to 0.79 (p < 0.001). The ICC (95% CI) for intrarater reliability was 0.92 (0.82 to 0.96) for rater A ...

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    4. SD-OCT parameters and visual field defect in chiasmal compression and the diagnostic value of neural network model

      SD-OCT parameters and visual field defect in chiasmal compression and the diagnostic value of neural network model

      Purpose: To evaluate the peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) measurements using spectral domain optical coherence tomography (SD-OCT) in patients with chiasmal compression and analyze the diagnostic value of a neural network model. Methods: Forty-seven patients with chiasmal compressive disorder were recruited and divided into two groups depending on the visual field defect (perimetric; group 1 and preperimetric; group 2). Fifty-seven normal subjects were also recruited (group 3). Peripapillary RNFL and macular GCIPL were analyzed in each group. A multilayer perceptron was trained using a training dataset and derived a neural network model ...

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    5. Visualization of deep choroidal vasculatures and measurement of choroidal vascular density: a swept-source optical coherence tomography angiography approach

      Visualization of deep choroidal vasculatures and measurement of choroidal vascular density: a swept-source optical coherence tomography angiography approach

      Background To investigate swept-source optical coherence tomography angiography (SS-OCTA) for deep choroid visualization and choroidal vascular density (CVD) measurement. Methods Healthy subjects and central serous chorioretinopathy (CSC) patients were recruited for macular SS-OCTA scans. We evaluated OCTA images at various depths to determine an optimal depth for visualizing choroidal vasculatures. We measured CVD with binarized OCTA images at the optimal depth. In healthy subjects, CVD was studied for its correlation with age, axial length (AL), and subfoveal choroidal thickness (SCT). In CSC eyes, CVD was compared with matched controls. Results Ninety-one healthy eyes and 22 CSC eyes were included. SS-OCTA ...

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    6. Model-to-Data Approach for Deep Learning in Optical Coherence Tomography Intraretinal Fluid Segmentation

      Model-to-Data Approach for Deep Learning in Optical Coherence Tomography Intraretinal Fluid Segmentation

      Importance Amid an explosion of interest in deep learning in medicine, including within ophthalmology, concerns regarding data privacy, security, and sharing are of increasing importance. A model-to-data approach, in which the model itself is transferred rather than data, can circumvent many of these challenges but has not been previously demonstrated in ophthalmology. Objective To determine whether a model-to-data deep learning approach (ie, validation of the algorithm without any data transfer) can be applied in ophthalmology. Design, Setting, and Participants This single-center cross-sectional study included patients with active exudative age-related macular degeneration undergoing optical coherence tomography (OCT) at the New England ...

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    7. Validation and application of OCT tissue attenuation index for the detection of neointimal foam cells

      Validation and application of OCT tissue attenuation index for the detection of neointimal foam cells

      Neointimal infiltration with foamy macrophages is recognized as an early and important sign of de-novo atherosclerosis after stent implantation (neoatherosclerosis). Recent histopathological studies have proven that automated quantification of signal attenuation using intravascular optical coherence tomography (OCT) imaging allows for sensitive identification of macrophages in native atherosclerotic disease. Whether this is true for neointimal foam cells in the setting of neoatherosclerosis remains unknown. Autopsy samples of stented coronary arteries (n = 13 cases) were evaluated by histology and OCT. After co-registration with histology, the attenuation rate of emitted laser light was measured in regions with and without neointimal foamy macrophages relative ...

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    8. Live mechanistic assessment of localized cardiac pumping in mammalian tubular embryonic heart

      Live mechanistic assessment of localized cardiac pumping in mammalian tubular embryonic heart

      Significance: Understanding how the valveless embryonic heart pumps blood is essential to elucidate biomechanical cues regulating cardiogenesis, which is important for the advancement of congenital heart defects research. However, methods capable of embryonic cardiac pumping analysis remain limited, and assessing this highly dynamic process in mammalian embryos is challenging. New approaches are critically needed to address this hurdle. Aim: We report an imaging-based approach for functional assessment of localized pumping dynamics in the early tubular embryonic mouse heart. Approach: Four-dimensional optical coherence tomography was used to obtain structural and Doppler hemodynamic imaging of the beating heart in live mouse embryos ...

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    9. Cooperative low-rank models for removing stripe noise from OCTA images

      Cooperative low-rank models for removing stripe noise from OCTA images

      Optical coherence tomography angiography (OCTA) is an emerging non-invasive imaging technique for imaging the microvasculature of the eye based on phase variance or amplitude decorrelation derived from repeated OCT images of the same tissue area. Stripe noise occurs during the OCTA acquisition process due to the involuntary movement of the eye. To remove the stripe noise (or 'destriping') effectively, we propose two novel image decomposition models to simultaneously destripe all the OCTA images of the same eye in a cooperative way: cooperative uniformity destriping (CUD) and cooperative similarity destriping (CSD) model. Both the models consider stripe noise by low-rank constraint ...

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    10. MS-CAM: Multi-Scale Class Activation Maps for Weakly-supervised Segmentation of Geographic Atrophy Lesions in SD-OCT Images

      MS-CAM: Multi-Scale Class Activation Maps for Weakly-supervised Segmentation of Geographic Atrophy Lesions in SD-OCT Images

      As one of the most critical characteristics in advanced stage of non-exudative Age-related Macular Degeneration (AMD), Geographic Atrophy (GA) is one of the significant causes of sustained visual acuity loss. Automatic localization of retinal regions affected by GA is a fundamental step for clinical diagnosis. In this paper, we present a novel weakly supervised model for GA segmentation in Spectral-Domain Optical Coherence Tomography (SD-OCT) images. A novel Multi-Scale Class Activation Map (MS-CAM) is proposed to highlight the discriminatory significance regions in localization and detail descriptions. To extract available multi-scale features, we design a Scaling and UpSampling (SUS) module to balance ...

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    11. Attention-guided 3D-CNN Framework for Glaucoma Detection and Structural-Functional Association using Volumetric Images

      Attention-guided 3D-CNN Framework for Glaucoma Detection and Structural-Functional Association using Volumetric Images

      The direct analysis of 3D Optical Coherence Tomography (OCT) volumes enables deep learning models (DL) to learn spatial structural information and discover new bio-markers that are relevant to glaucoma. Downsampling 3D input volumes is the state-of-art solution to accommodate for the limited number of training volumes as well as the available computing resources. However, this limits the network's ability to learn from small retinal structures in OCT volumes. In this paper, our goal is to improve the performance by providing guidance to DL model during training in order to learn from finer ocular structures in 3D OCT volumes. Therefore ...

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    12. Machine Learning Techniques for Ophthalmic Data Processing: A Review

      Machine Learning Techniques for Ophthalmic Data Processing: A Review

      Machine learning and especially deep learning techniques are dominating medical image and data analysis. This article reviews machine learning approaches proposed for diagnosing ophthalmic diseases during the last four years. Three diseases are addressed in this survey, namely diabetic retinopathy, age-related macular degeneration, and glaucoma. The review covers over 60 publications and 25 public datasets and challenges related to the detection, grading, and lesion segmentation of the three considered diseases. Each section provides a summary of the public datasets and challenges related to each pathology and the current methods that have been applied to the problem. Furthermore, the recent machine ...

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    13. Dynamic Imaging of Mouse Embryos and Cardiac Development in Static Culture

      Dynamic Imaging of Mouse Embryos and Cardiac Development in Static Culture

      Dynamic imaging is a powerful approach to assess the function of a developing organ system. The heart is a dynamic organ that undergoes quick morphological and mechanical changes through early embryonic development. Defining the embyonic mouse heart's normal function is important for our own understanding of human heart development and will inform us on treatments and prevention of congenital heart defects (CHD). Traditional methods such as ultrasound or fluorescence-based microscopy are suitable for live dynamic imaging, are excellent to visualize structure and connect gene expression to phenotypes, but can be of low quality in resolving fine features and lack ...

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    14. Effects of axial length on retinal nerve fiber layer and macular ganglion cell-inner plexiform layer measured by spectral-domain OCT

      Effects of axial length on retinal nerve fiber layer and macular ganglion cell-inner plexiform layer measured by spectral-domain OCT

      Purpose: To evaluate the influence of ocular axial length on circumpapillary retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness in healthy eyes after correcting for ocular magnification effect. Methods: In this cross-sectional study, we evaluated 120 eyes from 60 volunteer participants (myopes, emmetropes, and hyperopes). The thickness of the circumpapillary retinal nerve fiber layer and ganglion cell-inner plexiform layer were measured using the spectral optical coherence tomography (OCT)-Cirrus HD-OCT and correlated with ocular axial length. Adjustment for ocular magnification was performed by applying Littmann’s formula. Results: Before the adjustment for ocular magnification, age-adjusted mixed models analysis ...

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    15. Role of Microscope-Intraoperative Optical Coherence Tomography in paediatric keratoplasty: A comparative Study

      Role of Microscope-Intraoperative Optical Coherence Tomography in paediatric keratoplasty: A comparative Study

      Purpose To evaluate role of Microscope-Integrated Intraoperative Optical Coherence Tomography (i-OCT) in paediatric keratoplasty. Design Combined prospective and retrospective, comparative, interventional study Setting Dr Rajendra Prasad Centre for Ophthalmic Sciences, India Methods Seventy-five children aged ≤16 years planned for keratoplasty were divided into two groups and compared for intraoperative course and postoperative outcome. In Group-1 (prospective group, n=56), pre-operative anterior segment visualization was performed clinically, with ultrasound biomicroscopy (UBM) and i-OCT and keratoplasty was commenced under i-OCT microscope. In Group-2 (retrospective group, n=19), conventional microscope was employed during keratoplasty. Results In Group-1, i-OCT, UBM and clinical examination detected ...

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    16. Innovative method offers a new way of studying developmental cardiac biomechanics, live in 4-D

      Innovative method offers a new way of studying developmental cardiac biomechanics, live in 4-D

      How a valveless embryonic heart tube pumps blood is a long-standing scientific mystery. Thanks to innovations in light-based technology, fresh insights are now available into the biomechanics of mammalian cardiogenesis—and in particular, the pumping dynamics of the mammalian tubular embryonic heart.

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    17. Plaque mOrphology iMpact on Side Branch Occlusion at oPtical Coherence Tomography Evaluation in Percutaneous Coronary Interventions

      Plaque mOrphology iMpact on Side Branch Occlusion at oPtical Coherence Tomography Evaluation in Percutaneous Coronary Interventions

      Despite recent advances in interventional cardiology, bifurcation coronary artery stenoses (which account for 15-20% of all coronary lesions treated by PCI), remain a challenge for PCI operators with higher rates of failure, in-stent restenosis, stent thrombosis, and recurrent clinical events, when compared to simple non-bifurcation lesions. POMPEI trial is a prospective observational study. We aim to investigate the impact of morphological plaque characteristics assessed by optical coherence tomography (OCT) on the risk of developing side branch occlusion (SBO) in bifurcation PCI. A total of 27 patients undergoing bifurcation PCI will be recruited into the trial. PCI will be performed according ...

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    18. Full-range space-division multiplexing optical coherence tomography angiography

      Full-range space-division multiplexing optical coherence tomography angiography

      Abstract In this study, we demonstrated a full-range space-division multiplexing optical coherence tomography (FR-SDM-OCT) system. Utilizing the galvanometer-based phase modulation full-range technique, the total imaging range of FR-SDM-OCT can be extended to >20 mm in tissue, with a digitizer sampling rate of 500 MS/s and a laser sweeping rate of 100 kHz. Complex conjugate terms were suppressed in FR-SDM-OCT images with a measured rejection ratio of up to ∼46 dB at ∼1.4 mm depth and ∼30 dB at ∼19.4 mm depth. The feasibility of FR-SDM-OCT was validated by imaging Scotch tapes and human fingernails. Furthermore, we demonstrated ...

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    19. Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis)

      Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis)

      The optic nerve head (ONH), located in the back of the eye, is a critical site in understanding the pathophysiology of glaucoma. However, longitudinal changes of the ONH as disease develops have not been well characterized. Our goal was to develop an improved tool to quantify these changes in an in vivo monkey model of glaucoma. Longitudinal spectral-domain optical coherence tomography (OCT) imaging of the ONH was performed every other week under manometric intraocular pressure (IOP) control (10 mmHg) in a monkey during baseline and after induction of unilateral experimental glaucoma. We developed a computational pipeline that applied digital volume ...

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    20. Optical coherence tomography for characterization of nanocomposite materials (Thesis)

      Optical coherence tomography for characterization of nanocomposite materials (Thesis)

      Nanocomposite materials play an increasingly important role in various application areas, be it in an industrial, medical or everyday environment. The unique properties of nanocomposites go beyond those of conventional composite materials. Because nanoparticles have a high surface-to-volume ratio such as carbon nanotubes, they can reinforce an embedding polymer host matrix mechanically, or they enhance the electrical material conductivity. A major challenge in the development of nanoparticles and nanocomposites is the control of particle size and shape, and of the uniform dispersion of nanoparticles in the host material. Conventional characterization techniques lack either resolution, or can only inspect details of ...

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    21. In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis

      In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis

      Purpose: To describe and analyze the microstructural changes in herpetic stromal keratitis (HSK) observed in vivo by spectral-domain ocular coherence tomography (SD-OCT) at different stages of the disease. Methods: A prospective, cross-sectional, observational, and comparative SD-OCT analysis of corneas with active and inactive keratitis was performed, and the pathologic differences between the necrotizing and non-necrotizing forms of the disease were analyzed. Results: Fifty-three corneas belonging to 43 (81.1%) women and 10 (18.8%) men with a mean age of 41.0 years were included for analysis. Twenty-four (45.3%) eyes had active keratitis, and 29 (54.7%) had inactive ...

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    22. Non-invasive optical screening of Streptococcus Pneumonia based inflammatory changes of the tympanic membrane and mastoid mucosa in guinea pig otitis media using optical coherence tomography

      Non-invasive optical screening of Streptococcus Pneumonia based inflammatory changes of the tympanic membrane and mastoid mucosa in guinea pig otitis media using optical coherence tomography

      Abstract: The accurate screening of otitis media (OM) lies in clarifying the numerous confounding and quantitative factors that are discovered during primary inspections. Increased awareness about bacterial biofilms and inflammation has allowed researchers to develop a better understanding of the bacterial infections that occur in the middle ear. In this study, four live guinea pigs were inoculated with Streptococcus pneumonia to induce OM-related inflammatory changes. Since optical techniques have been effectively used for diagnosis in medicine, low-coherence interferometry-based optical coherence tomography (OCT) was employed for depth-resolved high-resolution data screening. Multiple locations of the tympanic membrane (TM), mastoid mucosa, and round ...

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    23. Visual function tests including the role of optical coherence tomography in neurofibromatosis

      Visual function tests including the role of optical coherence tomography in neurofibromatosis

      Optic pathway glioma (OPG) is a common and significant complication of neurofibromatosis 1 (NF-1) that might lead to vision loss. The main reason to treat OPG is to preserve vision. Tumor location along the visual pathway largely dictates the presenting signs and symptoms. Clinical ophthalmic evaluation is focused on optic nerve functions including evaluation of pupils’ reaction to light, visual acuity, color vision, and visual field, as well as optic nerve appearance. An important relatively new ancillary test is optic coherence tomography (OCT) that measures the volume of retinal nerve fiber layer around the optic nerve and the ganglion cell ...

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    24. Strain and elasticity imaging in compression optical coherence elastography: the two‐decade perspective and recent advances

      Strain and elasticity imaging in compression optical coherence elastography: the two‐decade perspective and recent advances

      Quantitative mapping of deformation and elasticity in optical coherence tomography has attracted much attention of researchers during the last two decades. However, despite intense effort it took ~15 years to demonstrate optical coherence elastography (OCE) as a practically useful technique. Similarly to medical ultrasound, where elastography was first realized using the quasi‐static compression principle and later shear‐wave‐based systems were developed, in OCE these two approaches also developed in parallel. However, although the compression OCE (C‐OCE) was proposed historically earlier in the seminal paper by J.Schmitt in 1998, breakthroughs in quantitative mapping of genuine local strains ...

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