1. All Articles

    25-48 of 15839 « 1 2 3 4 5 ... 658 659 660 »
    1. Two-dimensional micro-displacement measurement for laser coagulation using optical coherence tomography

      Two-dimensional micro-displacement measurement for laser coagulation using optical coherence tomography

      To improve the reproducibility of photocoagulation, the ability to quantitatively monitor the thermal change of laser-irradiated retinal tissue is required. Recently, optical coherence tomography has enabled non-invasive and non-contact monitoring of the tissue structural changes during laser irradiation. To further improve the capability of this technique, a method is proposed to measure tissue displacement by simultaneously using Doppler phase shifts and correlation coefficients. The theoretical approach for this method is described, and its performance is experimentally confirmed and evaluated. Finally, lateral and axial displacements in the laser-irradiated retinal tissues of an enucleated porcine eye are observed. The proposed method is ...

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    2. Postdoctoral research fellowships and studentship (optical coherence tomography) at Nanyang Technological University

      Postdoctoral research fellowships and studentship (optical coherence tomography) at Nanyang Technological University

      One PhD fellowship and 2 research staff position are available in the area of optical imaging at the Nanyang Technological University in the School of Electrical and Electronic Engineering. Successful candidates will join leading efforts in the development and application of new optical imaging techniques such as next-generation optical coherence tomography (OCT) imaging, endoscopic microscopy, and application of the new techniques in the research areas such as early cancer diagnosis. Liu group is supported by more than US$7M research funding in three main research directions: subcellular resolution transendoscopic OCT, submicrometer resolution ophthalmic OCT, and OCT nano-imaging. Requirements for graduate ...

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    3. The Effect of Systemic Tamsulosin Hydrochloride on Choroidal Thickness Measured by Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography

      The Effect of Systemic Tamsulosin Hydrochloride on Choroidal Thickness Measured by Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography

      Background : To evaluate the effects of selective α 1A -adrenoceptor antagonist tamsulosin hydrochloride on choroidal thickness using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT). Methods : This is a prospective observational study including 29 eyes of 29 patients with newly diagnosed benign prostatic hyperplasia. Choroidal thickness and retrobulbar ocular blood flow measurements were performed at baseline and after 3 months of treatment. Results were analyzed by the masked observer. Results : The mean subfoveal choroidal thickness (275.8–291.9 µm) and thicknesses 750 µm nasal (257.9–270.4 µm) and 750 µm temporal (262.4–277.0 µm) to the ...

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    4. Optical coherence tomography measurements of biological fluid flows with picolitre spatial localization

      Optical coherence tomography measurements of biological fluid flows with picolitre spatial localization

      Interest in studying the human and animal microcirculation has burgeoned in recent years. In part this has been driven by recent advances in volumetric microscopy modalities, which allow the study of the 3-D morphology of the microcirculation without the limitations of 2-D intra-vital microscopy. In this paper we highlight the power of optical coherence tomography (OCT) to image the normal and pathological microcirculation with picolitre voxel sizes. Both Doppler and speckle-variance methods are employed to characterize complex rheological flows both in-vitro and in-vivo. GPU accelerated image registration methods are demonstrated in order to mitigate problems of bulk tissue motion in ...

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    5. Ultrawide-field parallel spectral domain optical coherence tomography for nondestructive inspection of glass

      Ultrawide-field parallel spectral domain optical coherence tomography for nondestructive inspection of glass

      Aiming at the requirements of real-time inspection in material industry, an ultrawide-field parallel SD-OCT system capable of visualizing cross-sectional image of internal structures by a single shot of a 2-D CMOS camera is developed. To achieve ultrawide-field parallel detection, one meniscus lens with negative dioptric is introduced as an additional relay lens and imaging optics including sample arm, relay lenses and spectrometer are optimized as a whole for desirable imaging quality. The developed system has an ultrawide-field of 35 mm and an axial range of 8 mm in air. The maximum on-axis sensitivity and the axial resolution are experimentally determined ...

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    6. Comparison of event-based analysis of glaucoma progression assessed subjectively on visual fields and retinal nerve fibre layer attenuation measured by optical coherence tomography

      Comparison of event-based analysis of glaucoma progression assessed subjectively on visual fields and retinal nerve fibre layer attenuation measured by optical coherence tomography

      The purpose is to study the ability of an event-based analysis of retinal nerve fibre layer (RNFL) attenuation measured by Stratus ® optical coherence tomography (OCT) and to detect progression across the spectrum of glaucoma. Adult glaucoma suspects, ocular hypertensives and glaucoma patients who had undergone baseline RNFL thickness measurement on Stratus OCT and reliable automated visual field examination by Humphrey’s visual field analyser prior to March 2007 and had 5-year follow-up data were recruited. Progression on OCT was defined by two criteria: decrease in average RNFL thickness from baseline by at least 10 and 20 µ. Visual field progression was ...

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    7. Optical coherence tomography for retinal imaging in multiple sclerosis

      Optical coherence tomography for retinal imaging in multiple sclerosis

      Visual disturbances caused by inflammatory and demyelinating processes of the visual system, mainly in the optic nerve, are a common symptom in multiple sclerosis (MS). Optical coherence tomography (OCT) is a tool that is increasingly used for quantifying retinal damage in MS and other neurologic diseases. Based on spectral interferometry, it uses low-coherent infrared light to generate high-resolution spatial images of the retina. The retinal nerve fiber layer (RNFL) consists of unmyelinated axons that form the optic nerve, and thus represents a part of the central nervous system. OCT allows for noninvasive measurements of RNFL thickness in micrometer resolution. With ...

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    8. Predicting Visual Outcomes for Macula-Off Rhegmatogenous Retinal Detachment with Optical Coherence Tomography

      Predicting Visual Outcomes for Macula-Off Rhegmatogenous Retinal Detachment with Optical Coherence Tomography

      Purpose. We evaluated the ability of novel optical coherence tomography (OCT) parameters to predict postoperative best-corrected visual acuity (BCVA) in macula-off rhegmatogenous retinal detachment (RRD) eyes. Methods. We reviewed the medical records of 56 consecutive eyes with macula-off RRD. Clinical findings were analyzed including the relationship between preoperative OCT findings and 6-month postoperative BCVA. Results. Six-month postoperative BCVA was significantly correlated with preoperative findings including retinal height at the fovea, total and inner layer cross-sectional macular area within 2 mm of the fovea, and preoperative BCVA ( , and , resp.). Multiple regression analysis revealed that the duration of macular detachment and total ...

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    9. Three-dimensional optic nerve head images using optical coherence tomography with a broad bandwidth, femtosecond, and mode-locked laser

      Three-dimensional optic nerve head images using optical coherence tomography with a broad bandwidth, femtosecond, and mode-locked laser

      Purpose The aim of this study was to demonstrate the fine laminar structure of the optic nerve head (ONH), in vivo, using a broad wavelength, ultra-high resolution, and optically coherent tomography (OCT) system. Methods This high-resolution OCT system, based on a 200 nm bandwidth spectrometer and an 8 femtosecond ultra-short, mode-locked, coherent laser light source, enabled in vivo cross-sectional ONH imaging with 2.0 μm axial resolution. A total of 300 optic disc B-scans, which consisted of 300 × 2048 pixels, were obtained in 10 μm steps. Three-dimensional images were rendered from these images to obtain n face images of the ...

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    10. Optical Coherence Tomography Assessment of Late Intra-Scaffold Dissection - A New Challenge of Bioresorbable Scaffolds

      Optical Coherence Tomography Assessment of Late Intra-Scaffold Dissection - A New Challenge of Bioresorbable Scaffolds

      A 48-year-old man was admitted because of a non–ST-segment elevation myocardial infarction. Fifteen months previously, he had received a 3.0 × 28-mm bioresorbable vascular scaffold (BVS) (Absorb, Abbott Vascular, Santa Clara, California) in the mid-left anterior descending coronary artery for stable angina. Coronary angiography showed a focal in-scaffold restenosis (Figure 1 ). Optical coherence tomography (OCT) (Ilumien, St. Jude Medical, Saint Paul, Minnesota) revealed a heterogeneous pattern consisting of neointimal hyperplasia (Figure 1 ), mural white thrombus (Figure 1 ), and lipidic plaque with attenuation (Figure 1 ). OCT after pre-dilation with a 2.0 × 15-mm semicompliant balloon showed outer migration of scaffold ...

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    11. Optical coherence tomography and visual evoked potentials combined use as monitoring tools in Multiple Sclerosis patients

      Optical coherence tomography and visual evoked potentials combined use as monitoring tools in Multiple Sclerosis patients

      In Multiple Sclerosis-MS, optical coherence tomography-OCT is used to measure retinal nerve fiber layer-RNFL thickness as a marker of axonal loss and visual evoked potentials-VEPs as an indicator of demyelination. However, no clear indications are available on their combined use in MS monitoring. 80 MS patients underwent neurological and neurophysiological evaluation with OCT and VEPs, with routine clinical and MRI monitoring for a mean period of 1 year. Additional OCT-VEPs follow-up was obtained in 50 patients. Comparing eyes with and without previous ON, VEP latency and RNFL thickness were respectively significantly higher (131.2 ms Vs 118.8 ms, p ...

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    12. Spectral-Domain Optical Coherence Tomography in Hydroxychloroquine Retinopathy

      Spectral-Domain Optical Coherence Tomography in Hydroxychloroquine Retinopathy

      In 2011, revised guidelines for screening chloroquine and hydroxychloroquine (HCQ) retinopathy recommended spectral-domain optical coherence tomography (SD OCT), fundus autofluorescence, or multifocal electroretinogram in addition to ophthalmologic examination and 10-2 perimetry. 1 To date, the qualitative features of SD OCT in chloroquine and HCQ retinopathy have been reported in <60 patients, most of whom had established retinopathy. Also, thinning of parafoveal retina has been documented, 2,3 occurring even when cross-sectional scans are equivocal.

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    13. Postdoctoral Research Fellowships (Optical Coherence Tomography) Wellman Center for Photomedicine Massachusetts General Hospital

      Postdoctoral Research Fellowships (Optical Coherence Tomography) Wellman Center for Photomedicine Massachusetts General Hospital

      A Postdoctoral research fellowship in the area of optical coherence tomography (OCT) is available in the Tearney Lab at the Massachusetts General Hospital (MGH) in the Wellman Center for Photomedicine. This appointment will be made at the rank of postdoctoral fellow at Harvard Medical School. MGH’s role as a leading teaching affiliate of Harvard Medical School and close ties to Harvard University and MIT provide an outstanding environment for developing and translating new OCT technologies with applications in basic and clinical research. The fellowship will focus on the development and clinical application of advanced OCT imaging devices, including endoscopic ...

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    14. Infraredx Announces Research Collaboration with Massachusetts General Hospital to Explore New Generation of Cardiovascular Imaging Devices

      Infraredx Announces Research Collaboration with Massachusetts General Hospital to Explore New Generation of Cardiovascular Imaging Devices

      Infraredx, Inc., a cardiovascular imaging company pioneering the personalized diagnosis of coronary artery disease, today announced a collaboration with Massachusetts General Hospital (MGH) and leading coronary imaging researcher, Gary Tearney, M.D., Ph.D., professor of pathology at Harvard Medical School, Mike and Sue Hazard Family MGH Research Scholar, and founder of the Tearney Lab at the Wellman Center for Photomedicine at MGH. Dr. Tearney is best known for pioneering research efforts developing Optical Coherence Tomography (OCT), an imaging technology that uses light-scattering to image coronary arteries. Infraredx and Dr. Tearney first collaborated over a decade ago on the development ...

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    15. Automatic segmentation of microcystic macular edema in OCT

      Automatic segmentation of microcystic macular edema in OCT

      Microcystic macular edema (MME) manifests as small, hyporeflective cystic areas within the retina. For reasons that are still largely unknown, a small proportion of patients with multiple sclerosis (MS) develop MME—predominantly in the inner nuclear layer. These cystoid spaces, denoted pseudocysts, can be imaged using optical coherence tomography (OCT) where they appear as small, discrete, low intensity areas with high contrast to the surrounding tissue. The ability to automatically segment these pseudocysts would enable a more detailed study of MME than has been previously possible. Although larger pseudocysts often appear quite clearly in the OCT images, the multi-frame averaging ...

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    16. Effect of optical clearing agents on optical coherence tomography images of cervical epithelium

      Effect of optical clearing agents on optical coherence tomography images of cervical epithelium

      Optical coherence tomography (OCT) can be used as an adjunct to colposcopy in order to detect precancerous and cancerous cervical lesions. Optical clearing agents (OCAs) temporarily reduce the optical scattering of biological tissues. The purpose of this study was to investigate their influence on OCT imaging. OCT images were taken from unsuspicious and suspicious areas of fresh conization specimens immediately after resection and 5, 10, and 20 min after application of dimethyl sulfoxide ( DMSO ) or polyethylene glycol (PEG). Corresponding histologies were obtained from all sites. The images taken 5, 10, and 20 min after application of OCA were compared to ...

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    17. Feature of The Week 12/14/14: Penetrate Deeper Using Extended Source OCT

      Feature of The Week 12/14/14: Penetrate Deeper Using Extended Source OCT

      We have developed an extended source optical coherence tomography (SEES-OCT) technique in an attempt to improve signal strength for ophthalmic imaging. A line illumination with a visual angle of 7.9 mrad is produced by introducing a dispersive element in the infinity space of the sample arm. The maximum permissible exposure (MPE) of such an extended source is 3.1 times larger than that of a “standard” point source OCT, which corresponds to sensitivity improvement of 5 dB. The advantage of SEES-OCT in providing superior penetration depth over a point source system is demonstrated using swine eye tissues ex vivo ...

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    18. DETECTION OF SUBSURFACE DAMAGE IN OPTICAL TRANSPARENT MATERIALSS USING SHORT COHERENCE TOMOGRAPHY

      DETECTION OF SUBSURFACE DAMAGE IN OPTICAL TRANSPARENT MATERIALSS USING SHORT COHERENCE TOMOGRAPHY

      This paper describes the use of short coherence interferometry for the detection of subsurface damage (SSD) in optical transparent materials. The method is based on an interferometer using a light source with a short coherence length. A time domain (TD) and a frequency domain (FD) approach are explained. The OCT method allows a nondestructive measurement of the SSD compared to the state of the art SSD metrology, where the sample is destroyed. Compared to previous results [Ser10] a frequency domain (FD) setup is build up which allows SSD measurements under production environment conditions. The results of the FD set are ...

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    19. Effects of Misalignments in the Retinal Nerve Fiber Layer Thickness Measurements with Spectral Domain Optical Coherence Tomography

      Effects of Misalignments in the Retinal Nerve Fiber Layer Thickness Measurements with Spectral Domain Optical Coherence Tomography

      Purpose . To investigate misalignments (MAs) on retinal nerve fiber layer thickness (RNFLT) measurements obtained with SD-OCT. Methods . This was a retrospective, observational, cross-sectional study. Twenty-seven healthy and 29 glaucomatous eyes of 56 individuals with one normal exam and another showing MA were included. MAs were defined as an improper alignment of vertical vessels in the en face image. MAs were classified in complete MA (CMA) and partial MA (PMA), according to their site: 1 (superior, outside the measurement ring (MR)), 2 (superior, within MR), 3 (inferior, within MR), and 4 (inferior, outside MR). We compared RNFLT measurements of aligned versus ...

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    20. Optical Coherence Tomography in Patients with Chiari I Malformation

      Optical Coherence Tomography in Patients with Chiari I Malformation

      Background/Aims . To evaluate optic nerve head with spectral domain optical coherence tomography (OCT) in patients with Chiari I malformation (CMI) compared to healthy controls. Methods . Cross-sectional study. OCT of the optic nerve head of 22 patients with CMI and 22 healthy controls was quantitatively analyzed. The healthy controls were matched for age and sex with the study population. Mean retinal nerve fiber layer (RNFL) thickness was calculated for both eyes; the mean thickness value was also registered for each quadrant and for each subfield of the four quadrants. Results . CMI patients showed a reduction of the RNFL thickness in ...

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    21. Three-Dimensional Vascular Imaging of Proliferative Diabetic Retinopathy by Doppler Optical Coherence Tomography

      Three-Dimensional Vascular Imaging of Proliferative Diabetic Retinopathy by Doppler Optical Coherence Tomography

      Purpose To evaluate the three-dimensional architecture of neovascularization in proliferative diabetic retinopathy using Doppler optical coherence tomography (OCT). Design Prospective, nonrandomized clinical trial. Methods Seventeen eyes of 14 patients with proliferative diabetic retinopathy were prospectively studied. Prototype Doppler OCT was used to evaluate the three-dimensional vascular architecture at vitreoretinal adhesions. Results Proliferative membranes were detected in all eyes with proliferative diabetic retinopathy by standard OCT images. Doppler OCT images detected blood flow by neovascularization of the disc in 12 eyes and neovascularization elsewhere in 11 eyes. Doppler OCT images showed the three-dimensional extent of new vessels at various stages of ...

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    22. Feasibility of Optical Coronary Tomography in Quantitative Measurement of Coronary Arteries With Lipid-Rich Plaque

      Feasibility of Optical Coronary Tomography in Quantitative Measurement of Coronary Arteries With Lipid-Rich Plaque

      Background: The aim of the present study was to evaluate the feasibility of optical coherence tomography (OCT) for measurement of vessel area in coronary arteries with lipid-rich plaque as compared with intravascular ultrasound (IVUS). Methods and Results: We investigated 80 coronary artery segments with lipid-rich plaque on OCT and non-attenuated plaque on IVUS. According to the lipid arc on OCT, the plaques were classified into 4 groups: group 1, lipid arc ≤90°; group 2, 90°<lipid arc≤180°; group 3, 180°<lipid arc≤270°; group 4, lipid arc >270°. Vessel circular arcs that could not be identified due to OCT ...

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    23. Retinal Nerve Fiber Layer Defect Volume Deviation Analysis Using Spectral Domain Optical Coherence Tomography

      Retinal Nerve Fiber Layer Defect Volume Deviation Analysis Using Spectral Domain Optical Coherence Tomography

      Purpose: To report the retinal nerve fiber layer (RNFL) defect volume deviation according to structural RNFL loss in RNFL thickness maps Methods: RNFL defect is defined in RNFL thickness maps by the degree of RNFL loss. A 20% to 70% degree of RNFL loss was set with a 1% interval as the reference level for determining the boundary of RNFL defects. Each individual RNFL thickness map was compared to a normative database map and the region below the reference level was identified as an RNFL defect. The RNFL defect volume was calculated by summing the volumes of each pixel inside ...

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    24. Patient Characteristics Associated with Artifacts in Spectralis Optical Coherence Tomography Imaging of the Retinal Nerve Fiber Layer in Glaucoma

      Patient Characteristics Associated with Artifacts in Spectralis Optical Coherence Tomography Imaging of the Retinal Nerve Fiber Layer in Glaucoma

      Purpose To determine patient factors and eye conditions associated with artifacts in Spectralis optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) scans. Design Retrospective cross-sectional study. Methods The prevalence of twelve artifact types were described in this review of 2313 eye scans from 1188 patients who underwent a complete eye exam with Spectralis OCT scanning during the period of September 2009 to July 2013. Generalized estimating equations model was utilized to analyze associations between increased artifact prevalence and 10 patient characteristics, which included age, sex, race, visual acuity, refractive error, astigmatism, cataract status, glaucoma staging, visual field reliability, and ...

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