1. 73-96 of 492 « 1 2 3 4 5 6 7 ... 19 20 21 »
    1. Optical coherence tomography retinal image reconstruction via nonlocal weighted sparse representation

      Optical coherence tomography retinal image reconstruction via nonlocal weighted sparse representation

      We present a nonlocal weighted sparse representation (NWSR) method for reconstruction of retinal optical coherence tomography (OCT) images. To reconstruct a high signal-to-noise ratio and high-resolution OCT images, utilization of efficient denoising and interpolation algorithms are necessary, especially when the original data were subsampled during acquisition. However, the OCT images suffer from the presence of a high level of noise, which makes the estimation of sparse representations a difficult task. Thus, the proposed NWSR method merges sparse representations of multiple similar noisy and denoised patches to better estimate a sparse representation for each patch. First, the sparse representation of each ...

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    2. In vivo high-resolution cortical imaging with extended-focus optical coherence microscopy in the visible-NIR wavelength range

      In vivo high-resolution cortical imaging with extended-focus optical coherence microscopy in the visible-NIR wavelength range

      Visible light optical coherence tomography has shown great interest in recent years for spectroscopic and high-resolution retinal and cerebral imaging. Here, we present an extended-focus optical coherence microscopy system operating from the visible to the near-infrared wavelength range for high axial and lateral resolution imaging of cortical structures in vivo . The system exploits an ultrabroad illumination spectrum centered in the visible wavelength range (λ c   =  650  nm, Δλ  ∼  250  nm) offering a submicron axial resolution (∼0.85  μm in water) and an extended-focus configuration providing a high lateral resolution of ∼1.4  μm maintained over ∼150  μm in depth in water. The ...

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    3. Automatic diagnosis of abnormal macula in retinal optical coherence tomography images using wavelet-based convolutional neural network features and random forests classifier

      Automatic diagnosis of abnormal macula in retinal optical coherence tomography images using wavelet-based convolutional neural network features and random forests classifier

      The present research intends to propose a fully automatic algorithm for the classification of three-dimensional (3-D) optical coherence tomography (OCT) scans of patients suffering from abnormal macula from normal candidates. The method proposed does not require any denoising, segmentation, retinal alignment processes to assess the intraretinal layers, as well as abnormalities or lesion structures. To classify abnormal cases from the control group, a two-stage scheme was utilized, which consists of automatic subsystems for adaptive feature learning and diagnostic scoring. In the first stage, a wavelet-based convolutional neural network (CNN) model was introduced and exploited to generate B-scan representative CNN codes ...

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    4. Classification of optical coherence tomography images for diagnosing different ocular diseases

      Classification of optical coherence tomography images for diagnosing different ocular diseases

      Optical Coherence tomography (OCT) images provide several indicators, e.g., the shape and the thickness of different retinal layers, which can be used for various clinical and non-clinical purposes. We propose an automated classification method to identify different ocular diseases, based on the local binary pattern features. The database consists of normal and diseased human eye SD-OCT images. We use a multiphase approach for building our classifier, including preprocessing, Meta learning, and active learning. Pre-processing is applied to the data to handle missing features from images and replace them with the mean or median of the corresponding feature. All the ...

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    5. Polymeric endovascular strut and lumen detection algorithm for intracoronary optical coherence tomography images

      Polymeric endovascular strut and lumen detection algorithm for intracoronary optical coherence tomography images

      Polymeric endovascular implants are the next step in minimally invasive vascular interventions. As an alternative to traditional metallic drug-eluting stents, these often-erodible scaffolds present opportunities and challenges for patients and clinicians. Theoretically, as they resorb and are absorbed over time, they obviate the long-term complications of permanent implants, but in the short-term visualization and therefore positioning is problematic. Polymeric scaffolds can only be fully imaged using optical coherence tomography (OCT) imaging—they are relatively invisible via angiography—and segmentation of polymeric struts in OCT images is performed manually, a laborious and intractable procedure for large datasets. Traditional lumen detection methods ...

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    6. Investigation of the effect of directional (off-axis) illumination on the reflectivity of retina layers in mice using swept-source optical coherence tomography

      Investigation of the effect of directional (off-axis) illumination on the reflectivity of retina layers in mice using swept-source optical coherence tomography

      Changes in visibility of the Henle fiber layer and photoreceptor bands of the human retina with illumination directionality have been reported in OCT clinical imaging. These are a direct consequence of the changes in back scattering due to fibrous tissue orientation and to waveguiding properties of the photoreceptors respectively. Here we report the preliminary results of a study on the effects of retinal images acquired with OCT of illumination directionality in the mouse retina. The quantitative assessment of the reflectivity of retinal layers of a BALB/c and WT pigmented mice was performed in-vivo using a swept-source optical coherence tomography ...

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    7. Adaptive optics with combined optical coherence tomography and scanning laser ophthalmoscopy for in vivo mouse retina imaging

      Adaptive optics with combined optical coherence tomography and scanning laser ophthalmoscopy for in vivo mouse retina imaging

      Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are two state-of-the-art imaging technologies commonly used to study retina. Adaptive Optics (AO) methodologies enable high-fidelity correction of ocular aberrations, resulting in improved resolution and sensitivity for both SLO and OCT systems. Here we present work integrating OCT into a previously described mouse retinal AO-SLO system, allowing simultaneous reflectance and fluorescence imaging. The new system allows simultaneous data acquisition of AO-SLO and AO-OCT, facilitating registration and comparison of data from both modalities. The system has data acquisition speed of 200 kHz A-scans/pixel, and high volumetric resolution.

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    8. White matter atrophy in spinocerebellar ataxia type 1 mouse models revealed by serial optical coherence scanner

      White matter atrophy in spinocerebellar ataxia type 1 mouse models revealed by serial optical coherence scanner

      Spinocerebellar ataxia type 1 (SCA1) is a fatal inherited neurodegenerative disease. Post-mortem studies showed neurodegeneration involving white matter components in the cerebral lobes, the cerebellar peduncles and the more distal cranial nerves in human patients. However, the progression of SCA1 in the brain remains unclear. We present the study of white matter atrophy of SCA1 mouse models using serial optical coherence scanner (SOCS). SOCS consists of a polarization sensitive optical coherence tomography and a tissue slicer (vibratome) with associated controls for serial imaging. The optical system has 5.5 µm axial resolution and utilizes a scan lens or a water-immersion ...

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    9. Optical coherence tomography (OCT) imaging of dynamic airway behavior in an asthma model

      Optical coherence tomography (OCT) imaging of dynamic airway behavior in an asthma model

      To better understand bronchoconstriction in asthma, it is critical to dynamically visualize airway behavior in vivo. However, currently available imaging techniques do not have sufficient temporal and spatial resolution to investigate airway dynamics. We propose to use endobronchial Optical Coherence Tomography (OCT) to provide real-time cross-sectional images of airway dynamics with a high spatial resolution. Our aim was to study the structure and function of spatially distinct airways during tidal breathing (TB), breath-holds (BH) at end inspiration, and in a response to single deep inspiration (DI) and multiple DI (MDI) in a preclinical sheep asthma model. Anesthetized and mechanically ventilated ...

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    10. Visualizing cellular markers of sensorineural hearing loss in the murine cochlea using micro-optical coherence tomography

      Visualizing cellular markers of sensorineural hearing loss in the murine cochlea using micro-optical coherence tomography

      Although sensorineural hearing loss (SNHL) affects 600 million people globally and its prevalence is increasing, therapies remain limited. Advances in therapy development for SNHL are slow because we do not possess a method for visualizing the cochlea’s interior in living humans and relating visualized pathology to a patient’s hearing ability. To this end, we are investigating the ability of micro-optical coherence tomography (µOCT), a low-coherence interferometric imaging technique that requires no contrast agent and improves upon standard OCT in resolution and depth of focus, to visualize the micron-sized cellular structures in the cochlea. We recently demonstrated µOCT’s ...

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    11. Contrast enhancement of pump-probe optical coherence tomography (PP-OCT) based molecular imaging using methylene blue loaded PLGA particles

      Contrast enhancement of pump-probe optical coherence tomography (PP-OCT) based molecular imaging using methylene blue loaded PLGA particles

      Atherosclerosis, a condition in which plaque accumulates on the inner wall of arteries, is often recognized as a precursor to cardiovascular diseases (CVDs), the most common causes of death in the US. Optical Coherence Tomography (OCT) is an intravascular optical diagnosis tool, which can be used to obtain high resolution morphological images of atherosclerotic plaque. However, atherosclerotic plaque components, such as macrophages, can be misclassified due to their signal similarities to fibrin accumulations, cholesterol crystals and microcalcifications. To overcome these challenges, we develop a biocompatible contrast agent to enhance molecular imaging of a Pump-Probe OCT (PPOCT) system. Methylene blue (MB ...

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    12. Optical coherence tomography angiography based biomarkers to assess the safety of peripheral nerve electrostimulation

      Optical coherence tomography angiography based biomarkers to assess the safety of peripheral nerve electrostimulation

      Peripheral nerves connect and relay information between the central nervous system and its target organs. Small arteries traverse the epineurium and are responsible for supplying blood to the axons and cells within the nerves. Constriction or damage to these vessels can reduce perfusion leading to ischemic insults. Peripheral nerve electrostimulation has been approved for the treatment of epilepsy, depression and migraines, and is also being studied for the treatment of rheumatoid arthritis, Crohn’s disease, polycystic ovary syndrome, and type II diabetes. While the safety and efficacy of currently approved medical devices is well established, next generation devices may require ...

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    13. Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy

      Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy

      Tethered capsule endomicroscopy (TCE) is a new method for performing comprehensive microstructural OCT imaging of gastrointestinal (GI) tract in unsedated patients in a well-tolerated and cost-effective manner. These features of TCE bestow it with significant potential to improve the screening, surveillance and management of various upper gastrointestinal diseases. To achieve clinical adoption of this imaging technique, it is important to validate it with co-registered histology, the current diagnostic gold standard. One such method for co-registering OCT images with histology is laser cautery marking, previously demonstrated using a balloon-centering OCT catheter that operates in conjunction with sedated endoscopy. With laser marking ...

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    14. Using optical coherence tomography to detect disturbances in coronary microvascular in a model of fetal alcohol syndrome

      Using optical coherence tomography to detect disturbances in coronary microvascular in a model of fetal alcohol syndrome

      Congenital coronary anomalies can result in severe consequences such as arrhythmias and sudden death. However, the etiology of abnormal embryonic coronary microvasculature development is understudied. Using a novel contrast-agent-based optical coherence tomography (OCT) technique, scatter labeled imaging of microvasculature in excised tissue (SLIME), we compared diseased and normal embryonic quail coronary microvasculature in 3D. Congenital heart defects associated with fetal alcohol syndrome (FAS) were induced in a quail model by injecting 40 uL of 50% ethanol solution into eggs during gastrulation. These and saline-injected quail eggs were incubated until stage 36. SLIME contrast agent was perfused through the aortas of ...

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    15. Contrast enhancement of microscopic birefringent crystals using polarization sensitive micro-optical coherence tomography

      Contrast enhancement of microscopic birefringent crystals using polarization sensitive micro-optical coherence tomography

      Background: Birefringent crystals such as cholesterol and monosodium urate have recently been identified as possible pharmacologic targets for the treatment of coronary artery disease. The size of these crystals can be very small (on the order of 1 µm), making them difficult to identify. To image these microscopic crystals and enhance contrast, we modified existing micro optical coherence tomography system so that it was capable of obtaining polarization-sensitive images (PS-µOCT). A spectrometer-based PS-µOCT system was developed using a 270 nm wide broadband light source centered at 765 nm. Light was polarized using a polarizer and coupled to a ...

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    16. A study of the effects of supine position and fluid intake on normal airway geometry using anatomical optical coherence tomography

      A study of the effects of supine position and fluid intake on normal airway geometry using anatomical optical coherence tomography

      Airway inhalation injuries are present in up to a third of all major burns patients and are the leading cause of mortality among this population. Understanding the mechanism of injury could minimise oedema (swelling) and airway damage. In this study, we present an anatomical OCT (aOCT) imaging system, based on a 1300-nm wavelength, high-speed, long-range MEMS-VCSEL swept laser source, for real-time volumetric imaging and assessment of inhalation injuries in airways up to 3 cm in diameter. A custom fibre-optic probe with GRIN lens and micro prism is inserted though the nasal passage. Airway cross-sectional images acquired are used to assess ...

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    17. All-optical intravascular probe for dual-mode photoacoustic imaging and optical coherence tomography

      All-optical intravascular probe for dual-mode photoacoustic imaging and optical coherence tomography

      Intravascular (IV) imaging in percutaneous coronary interventions can be invaluable to treat coronary artery disease, to facilitate decision making and to guide stent placement. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) are both established IV imaging modalities. However, achieving contrast for specific structures such as lipid plaques can be challenging; with OCT, visualisation is typically limited to tissue depths less than 2 mm. Photoacoustic (PA) imaging provides contrast that is complementary to those of IVUS and OCT, and with previous demonstrations, visualisation of lipid plaques at depths greater than 4 mm has been achieved. In this study, we developed ...

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    18. Heterogeneity study of the human cervix between the internal os and the external os using optical coherence tomography

      Heterogeneity study of the human cervix between the internal os and the external os using optical coherence tomography

      The regional heterogeneity study of cervical ultrastructure is critical to understand the cervical functions like cervical softening and dilation. To better understand why the internal os initiates the premature remodeling, we present the heterogeneity study of collagen fiber network, tissue optical property, and mechanical property between the internal os and external os using optical coherence tomography (OCT) and indentation test. Pregnant (n=1) and non-pregnant patients (n=8) were consented after hysterectomy based on approved Institutional Review Board. Cervical axial slices from internal os and external os were imaged with OCT. The tissue ultrastructure was characterized by collagen fiber dispersion ...

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    19. Multimodal imaging of lung tissue dynamics in mechanically ventilated rats with optical coherence tomography and intravital microscopy

      Multimodal imaging of lung tissue dynamics in mechanically ventilated rats with optical coherence tomography and intravital microscopy

      The understanding of alveolar mechanics is an essential step towards new and more protective ventilation strategies which are of dare need for the treatment of diseases of lung tissue and the airways. Such ailments become a major task for medical care and health care systems in modern industrial countries in the future. Besides the obvious importance as life-saving intervention, the mechanical strain and processes on the level of gas exchange are still insufficiently understood. Therefore, it is of great interest to characterize lung tissue and tissue dynamics during artificial ventilation at the alveolar level. 4D Optical coherence tomography (OCT) in ...

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    20. 4D optical coherence tomography for imaging aortic valve dynamics ex vivo

      4D optical coherence tomography for imaging aortic valve dynamics ex vivo

      The mechanical components of the heart, especially the valves, are enormously stressed during lifetime and undergo different pathophysiological tissue transformations, which affect cardiac output and in consequence living comfort of affected patients. Calcific aortic valve stenosis (AVS) is the most common valve disease in modern industrial countries but the pathogenesis and progression of this disease is still unknown. Therefore, animal models, especially mouse models, are a powerfull tool to investigate this disease in more detail with high resolution imaging techniques like optical coherence tomography and video microscopy. A custom-made pump was used for artificial stimulation of aortic valves ex vivo ...

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    21. Polarization-sensitive optical coherence tomography in the anterior mouse eye

      Polarization-sensitive optical coherence tomography in the anterior mouse eye

      Polarization-sensitive optical coherence tomography (PS-OCT) provides intrinsic contrast related to tissue microstructure. In the past, PS-OCT has been successfully used for imaging the anterior eye of humans in a variety of pathologic conditions. Here, we present PS-OCT imaging of the anterior eye in mice. Spectral domain PS-OCT centered at a wavelength of 840 nm was performed in anaesthetized laboratory mice. Three dimensional data sets were acquired at a 70 kHz A-line rate. PS-OCT images displaying phase retardation, birefringent axis orientation and degree of polarization uniformity (DOPU) were computed. Similar to human anterior segments, depolarization was observed in the corneal stroma ...

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    22. Optical coherence computed tomography for quantitative 3D imaging of adult zebrafish

      Optical coherence computed tomography for quantitative 3D imaging of adult zebrafish

      Optical imaging in turbid media like biological tissue is limited by light scattering. We present optical coherence computed tomography (OCCT) as a novel optical imaging modality for ballistic 3D optical imaging of turbid media. In OCCT, coherence and confocal gated measurements from multiple lateral positions and angles are used to reconstruct quantitative 3D images of the optical attenuation and refractive index with tomographic reconstruction algorithms. OCCT allows for high resolution imaging in turbid media by strong suppression of scattered light using a combination of coherence and confocal gating. The time-of-flight information in the transmission measurements allows for quantitative reconstruction of ...

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    23. Cellular-resolution, extended depth of focus optical coherence tomography catheter toward in vivo cardiovascular imaging

      Cellular-resolution, extended depth of focus optical coherence tomography catheter toward in vivo cardiovascular imaging

      Optical coherence tomography (OCT) has been a useful clinical tool for diagnosing coronary artery disease through a flexible catheter, but its full promise relies on resolving cellular and sub-cellular structures in vivo. Previously, visualizing cellular structures through an imaging catheter is not possible due to limited depth of focus (DOF) of a tightly focused Gaussian beam: typically, a Gaussian beam with 2-3 μm resolution has a DOF within 100 μm, which is not sufficient for in vivo catheter imaging. Therefore, we developed a self-imaging wavefront division optical system that generates a coaxially-focused multimode (CAFM) beam with a DOF that is ...

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    24. In-vivo detection of the skin dermo-epidermal junction by ultrahigh resolution optical coherence tomography

      In-vivo detection of the skin dermo-epidermal junction by ultrahigh resolution optical coherence tomography

      The human skin is comprised by two layers; epidermis and dermis, separated by the dermo-epidermal junction (DEJ). The relevance of depicting DEJ and measurement of the epidermal thickness (ET) is e.g. seen for superficial skin cancers where delineation of DEJ is of prime prognostic importance. Another example is diagnosis of psoriasis where a thickened epidermis and a ridged DEJ is a hallmark. Histopathological examination of biopsied tissue is traditionally performed to trace DEJ and measure ET. An efficient and precise method to locate DEJ and measure ET is optical coherence tomography (OCT) which is an in vivo and non-invasive ...

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    73-96 of 492 « 1 2 3 4 5 6 7 ... 19 20 21 »
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