1. All Articles

    25-48 of 21422 « 1 2 3 4 5 ... 891 892 893 »
    1. Paclitaxel crystals on the surface of a bioresorbable vascular scaffold visualized by optical coherence tomography after drug-eluting balloon angioplasty

      Paclitaxel crystals on the surface of a bioresorbable vascular scaffold visualized by optical coherence tomography after drug-eluting balloon angioplasty

      A 79-year-old male with history of coronary artery disease with percutaneous revascularization of medium left anterior descending artery with a bare metal stent 2.5 × 23 mm presented with unstable angina. A significant in-stent restenosis (ISR) was observed ( Panel A ), and treated by means of an in-stent bioresorbable vascular scaffold (BVS) (absorb 2.5 × 28 mm) with excellent angiographic result. Six months later, the patient presented again with unstable angina and significant restenosis intra-scaffold was observed. Optical coherence tomography (OCT) of the BVS was performed showing significant neointimal proliferation ( Panel B ). Firstly, an angioplasty with a cutting balloon 2.75 ...

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    2. EuroIntervention Intravascular ultrasound and optical coherence tomography images for direct right coronary artery injury after tricuspid valve annuloplasty

      EuroIntervention Intravascular ultrasound and optical coherence tomography images for direct right coronary artery injury after tricuspid valve annuloplasty

      A 76-year-old female was admitted with dyspnoea and leg oedema. Echocardiography showed severe mitral and tricuspid valve regurgitation with marked right ventricular (RV) dilatation, and coronary angiography showed intact left and right coronary arteries (RCA) (Online Figure 1) . She was diagnosed with heart failure due to combined valvular disease and underwent tricuspid valve (the Kay bicuspidisation technique without ring) and mitral valve annuloplasty. After the operation, she suffered from myocardial infarction with ST-segment elevation in the inferior leads. Coronary angiography showed a total occlusion (arrow) at the middle portion of the RCA (Panel A, Moving image 1) . After passing a ...

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    3. Phase-noise analysis of swept-source optical coherence tomography systems

      Phase-noise analysis of swept-source optical coherence tomography systems

      We propose a new model to characterize the phase noise in swept-source optical coherence tomography (SS-OCT). The new model explicitly incorporates scanning variability, timing jitter, and sample location in addition to intensity noise (shot noise). The model was analyzed and validated by using both Monte Carlo methods and experiments. We suggest that the proposed model can be used as a guideline for future SS-OCT experimental designs.

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    4. Handheld optical coherence tomography angiography

      Handheld optical coherence tomography angiography

      We developed a handheld optical coherence tomography angiography (OCTA) system using a 100-kHz swept-source laser. The handheld probe weighs 0.4 kg and measures 20.6 × 12.8 × 4.6 cm 3 . The system has dedicated features for handheld operation. The probe is equipped with a mini iris camera for easy alignment. Real-time display of the en face OCT and cross-sectional OCT images in the system allows accurately locating the imaging target. Fast automatic focusing was achieved by an electrically tunable lens controlled by a golden-section search algorithm. An extended axial imaging range of 6 mm allows easy alignment. A ...

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    5. Optical Coherence Tomography (OCT) for the conservation and interpretation of vitreous materials in museums collections with the British Museum & Nottingham Trent University

      Optical Coherence Tomography (OCT) for the conservation and interpretation of vitreous materials in museums collections with the British Museum & Nottingham Trent University

      AHRC Collaborative Doctoral Partnership Research Studentship 2017 Nottingham Trent University, School of Science & Technology, and the British Museum, Department of Scientific Research Optical Coherence Tomography (OCT) for the conservation and interpretation of vitreous materials in museums collections Applications are invited for an AHRC Collaborative Doctoral Partnership PhD studentship, to be undertaken at Nottingham Trent University (School of Science & Technology) and the British Museum (Department of Scientific Research). The studentship is for a three-year (full-time) project entitled ‘Optical Coherence Tomography (OCT) for the conservation and interpretation of vitreous materials in museums collections’, to commence on 1 October 2017. The student will ...

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    6. I can’t always play it safe with my patients. That’s why I cautiously innovate

      I can’t always play it safe with my patients. That’s why I cautiously innovate

      A s a profession, doctors are determined and cautious. We are determined to do our best and provide the best care for our patients. But we can be quite cautious about trying out new treatments or technologies to help provide that “best care.” Some hesitation makes sense. Countless treatments that sounded promising at the time fell by the wayside because they didn’t measure up — or caused harm. One example: Fifty years ago, dermatologists often used radiation to treat acne. It seemed to work, but researchers later learned that it increased the risk for thyroid, skin, and other cancers. Yet ...

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      Mentions: Orit Markowitz
    7. Monitoring retinoschisis and non-acute retinal detachment by optical coherence tomography: morphologic aspects and clinical impact

      Monitoring retinoschisis and non-acute retinal detachment by optical coherence tomography: morphologic aspects and clinical impact

      Purpose To differentiate retinoschisis (RS) from non-acute retinal detachment (naRD) in clinical routine using optical coherence tomography (OCT), describe unique morphological OCT characteristics and monitor disease progression. Methods This prospective, observational study included 64 eyes of 44 patients with either RS or naRD. Patients were examined clinically and using Heidelberg Spectralis OCT ® , Topcon DRI OCT ® and Cirrus HRA-OCT ® over 2 years with follow-up at 1, 3, 6, 12 and 24 months. Main outcomes were typical morphologic findings of RS and naRD described in OCT. Progression was monitored using Spectralis OCT ® follow-up mapping and an eye-tracking method. Results Forty-seven eyes were ...

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    8. Measuring device and glucose concentration measurement method of the measuring device

      Measuring device and glucose concentration measurement method of the measuring device

      The inventive concept relates to a measuring device. The measuring device irradiates a first beam including a polarization component and a second beam which is a wavelength swept laser having a coherence length previously set and can measure a glucose concentration of an aqueous humor by measuring an optical path length and the rotation amount of a polarization plane respectively from a first output beam and a second output beam being output from an eye.

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    9. System and method for autofocusing of an imaging system

      System and method for autofocusing of an imaging system

      Methods and systems for autofocusing of an imaging system are presented. Provided is an imaging system and an optical interferometry system for generating one or more images corresponding to a target region in a subject. The method provides calibration information that identifies a focal position of the optical interferometry system corresponding to a determined focal position of the imaging system. A subsequent focal position of the imaging system is determined for generating a desired image corresponding to at least one of another target region in the subject and another position of the target region relative to the imaging system based ...

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    10. Reconstruction of optical coherent tomography (OCT) images of morphological features

      Imaging devices and processing techniques based on imaging information along the depth direction in an optical coherent tomography (OCT) image are disclosed to enhance observed morphological features. The methods and systems obtain different OCT images of the target object under different reference path lengths, process the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images, and processing the derivative to extract improved image information of the target object. The derivatives may be in a form related to a gradient value of the normalized OCT image intensity, or an ...

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    11. Intraoperative optical coherence tomography for soft tissue sarcoma differentiation and margin identification

      Intraoperative optical coherence tomography for soft tissue sarcoma differentiation and margin identification

      Background and Objective Sarcomas are rare but highly aggressive tumors, and local recurrence after surgical excision can occur in up to 50% cases. Therefore, there is a strong clinical need for accurate tissue differentiation and margin assessment to reduce incomplete resection and local recurrence. The purpose of this study was to investigate the use of optical coherence tomography (OCT) and a novel image texture-based processing algorithm to differentiate sarcoma from muscle and adipose tissue. Study Design and Methods In this study, tumor margin delineation in 19 feline and canine veterinary patients was achieved with intraoperative OCT to help validate tumor ...

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    12. Chronic total occlusion is associated with a higher incidence of malapposition and uncovered stent struts: OCT findings at 6 months following DES implantation

      Chronic total occlusion is associated with a higher incidence of malapposition and uncovered stent struts: OCT findings at 6 months following DES implantation

      Objectives To compare stent coverage and malapposition in patients with chronic total occlusion (CTO) lesions and non-CTO lesions (including lipid-rich plaque [LRP] and non-lipid-rich plaque [non-LRP]) after drug-eluting stent (DES) implantation by optical coherence tomography (OCT). Background Different initial lesion characteristics may be related to heterogeneous vessel responses after DES implantation. However, the vessel response in patients with CTO and non-CTO lesions after stenting is unclear. Methods We retrospectively enrolled 64 patients with 68 target lesions. All of the patients underwent OCT imaging immediate after stenting and 6 months after stenting. LRP was defined as the plaque with lipid content ...

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    13. Optical Coherence Tomography Angiography of Conjunctival Racemose Hemangioma

      Optical Coherence Tomography Angiography of Conjunctival Racemose Hemangioma

      A 29-year-old man observed a red spot on his left eye. By slit-lamp biomicroscopy, the base of the lesion measured 1.5 mm and was located at the inferonasal limbus (Fig 1A). Anterior segment fluorescein angiography (FA) (Fig 1B) and optical coherence tomography angiography (OCTA) (Fig 1C; Optovue Inc, Fremont, CA) showed a vascular mass compatible with racemose hemangioma. The hemangioma and related vessels were better depicted on noninvasive OCTA compared with FA.

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    14. In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors

      In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors

      The light responses of rod and cone photoreceptors have been studied electrophysiologically for decades, largely with ex vivo approaches that disrupt the photoreceptors’ subretinal microenvironment. Here we report the use of optical coherence tomography (OCT) to measure light-driven signals of rod photoreceptors in vivo. Visible light stimulation over a 200-fold intensity range caused correlated rod outer segment (OS) elongation and increased light scattering in wild-type mice, but not in mice lacking the rod G-protein alpha subunit, transducin (Gα t ), revealing these responses to be triggered by phototransduction. For stimuli that photoactivated one rhodopsin per Gα t the rod OS swelling ...

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    15. Diabetic retinopathy and OCT angiography: clinical findings and future perspectives

      Diabetic retinopathy and OCT angiography: clinical findings and future perspectives

      In diabetic retinopathy (DR), macular involvement can present as either macular edema or ischemia. Fluorescein angiography remains the gold standard in the evaluation of retinal vascular perfusion and diagnosis of macular ischemia. However, it is a costly, time-consuming technique, it requires venipuncture, and reports of anaphylaxis and death related to fluorescein injections have been documented, despite their rarity. Optical coherence tomography (OCT) provides a fast and non-invasive method to assess retinal structures at a microscopic level. OCT angiography permits the noninvasive study of retinal and choroid circulation via motion contrast imaging. Split-spectrum amplitude decorrelation angiography combined with OCT angiography has ...

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    16. Image analysis in optical coherence tomography Retinal layer segmentation (Thesis)

      Image analysis in optical coherence tomography Retinal layer segmentation (Thesis)

      How do we explain the world around us? Two wise men started the search for an answer thousands of years ago and became two of the most influential philosophers. Their debate still remains with us today. Plato believed true knowledge comes from the mind, which is rational, and not from the senses, which can be fooled. In contrast, Aristotle believed the senses allow us to learn and interact with the world around us. Despite this ongoing debate, we use our senses to experience the world around us. Of all our senses, the sense of sight contributes the most to our ...

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    17. Improving graph-based OCT segmentation for severe pathology in retinitis pigmentosa patients

      Improving graph-based OCT segmentation for severe pathology in retinitis pigmentosa patients

      Three dimensional segmentation of macular optical coherence tomography (OCT) data of subjects with retinitis pigmentosa (RP) is a challenging problem due to the disappearance of the photoreceptor layers, which causes algorithms developed for segmentation of healthy data to perform poorly on RP patients. In this work, we present enhancements to a previously developed graph-based OCT segmentation pipeline to enable processing of RP data. The algorithm segments eight retinal layers in RP data by relaxing constraints on the thickness and smoothness of each layer learned from healthy data. Following from prior work, a random forest classifier is first trained on the ...

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    18. An automated image processing method for classification of diabetic retinopathy stages from conjunctival microvasculature images

      An automated image processing method for classification of diabetic retinopathy stages from conjunctival microvasculature images

      The conjunctiva is a densely vascularized tissue of the eye that provides an opportunity for imaging of human microcirculation. In the current study, automated fine structure analysis of conjunctival microvasculature images was performed to discriminate stages of diabetic retinopathy (DR). The study population consisted of one group of nondiabetic control subjects (NC) and 3 groups of diabetic subjects, with no clinical DR (NDR), non-proliferative DR (NPDR), or proliferative DR (PDR). Ordinary least square regression and Fisher linear discriminant analyses were performed to automatically discriminate images between group pairs of subjects. Human observers who were masked to the grouping of subjects ...

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      Mentions: Mahnaz Shahidi
    19. Analysis of polygonal scanning heads: from industrial to high-end applications in swept sources for OCT

      Analysis of polygonal scanning heads: from industrial to high-end applications in swept sources for OCT

      An analysis of polygonal mirror (PM) scanning heads has been performed, in order to provide a tool for their optimal design. The theory developed brings under the same umbrella applications that range from industrial dimensional measurements to high-end biomedical imaging, for example for broadband laser sources swept in frequency for Swept Source Optical Coherence Tomography (SS-OCT). The different characteristic parameters of the PM scanning heads were considered in order to achieve a rigorous analysis: number of PM facets, inner radius of the PM, eccentricity of the PM pivot with regard to the incident fixed laser beam, distance from this beam ...

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    20. Collaborative SDOCT segmentation and analysis software

      Collaborative SDOCT segmentation and analysis software

      Spectral domain optical coherence tomography (SDOCT) is routinely used in the management and diagnosis of a variety of ocular diseases. This imaging modality also finds widespread use in research, where quantitative measurements obtained from the images are used to track disease progression. In recent years, the number of available scanners and imaging protocols grown and there is a distinct absence of a unified tool that is capable of visualizing, segmenting, and analyzing the data. This is especially noteworthy in longitudinal studies, where data from older scanners and/or protocols may need to be analyzed. Here, we present a graphical user ...

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    21. Longitudinal analysis of mouse SDOCT volumes

      Longitudinal analysis of mouse SDOCT volumes

      Spectral-domain optical coherence tomography (SDOCT), in addition to its routine clinical use in the diagnosis of ocular diseases, has begun to fund increasing use in animal studies. Animal models are frequently used to study disease mechanisms as well as to test drug efficacy. In particular, SDOCT provides the ability to study animals longitudinally and non-invasively over long periods of time. However, the lack of anatomical landmarks makes the longitudinal scan acquisition prone to inconsistencies in orientation. Here, we propose a method for the automated registration of mouse SDOCT volumes. The method begins by accurately segmenting the blood vessels and the ...

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