1. All Articles

    25-48 of 15455 « 1 2 3 4 5 ... 642 643 644 »
    1. Noise characterization of broadband fiber Cherenkov radiation as a visible-wavelength source for optical coherence tomography and two-photon fluorescence microscopy

      Noise characterization of broadband fiber Cherenkov radiation as a visible-wavelength source for optical coherence tomography and two-photon fluorescence microscopy

      Optical sources in the visible region immediately adjacent to the near-infrared biological optical window are preferred in imaging techniques such as spectroscopic optical coherence tomography of endogenous absorptive molecules and two-photon fluorescence microscopy of intrinsic fluorophores. However, existing sources based on fiber supercontinuum generation are known to have high relative intensity noise and low spectral coherence, which may degrade imaging performance. Here we compare the optical noise and pulse compressibility of three high-power fiber Cherenkov radiation sources developed recently, and evaluate their potential to replace the existing supercontinuum sources in these imaging techniques.

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    2. Optical Coherence Tomography Assessment of Angle Anatomy Changes After Trabeculectomy in Primary Angle-Closure Glaucoma

      Optical Coherence Tomography Assessment of Angle Anatomy Changes After Trabeculectomy in Primary Angle-Closure Glaucoma

      Purpose: Using anterior chamber optical coherence tomography to evaluate changes in angle anatomy in patients with primary angle-closure glaucoma (PACG) before and after trabeculectomy. Methods: This is a prospective observational study in 38 eyes of 38 patients with PACG, who underwent trabeculectomy. We used customized software to analyze optical coherence tomography images (Visante) of all participants before and after the surgical treatment. Multivariate linear regression analysis was performed for predictors of percentage change in mean angle parameters, including scleral spur angle, angle opening distance, angle recess area, and trabecular-iris surface area. The main outcome measures were changes in angle parameters ...

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    3. OCT-Derived Comparison of Corneal Thickness Distribution and Asymmetry Differences Between Normal and Keratoconic Eyes

      OCT-Derived Comparison of Corneal Thickness Distribution and Asymmetry Differences Between Normal and Keratoconic Eyes

      Purpose: The aim of this study was to investigate the corneal thickness asymmetry indices in a large pool of patients with keratoconus derived using anterior segment optical coherence tomography (AS-OCT) in comparison with established Scheimpflug imaging-derived keratoconus classification indices. Methods: Six specific indices were comparatively investigated in this study encompassing 2 groups: keratoconic group A (175 eyes) and age- and gender-matched control group B (175 eyes). AS-OCT was used for corneal focal thinning and irregularity indices, namely the superior nasal minus inferior temporal (SN-IT), superior minus inferior (S-I), minimum minus median (Min-Med) focal thinning, and thickness range, defined as the ...

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    4. Supercontinuum optimization for dual-soliton based light sources using genetic algorithms in a grid platform

      Supercontinuum optimization for dual-soliton based light sources using genetic algorithms in a grid platform

      We present a numerical strategy to design fiber based dual pulse light sources exhibiting two predefined spectral peaks in the anomalous group velocity dispersion regime. The frequency conversion is based on the soliton fission and soliton self-frequency shift occurring during supercontinuum generation. The optimization process is carried out by a genetic algorithm that provides the optimum input pulse parameters: wavelength, temporal width and peak power. This algorithm is implemented in a Grid platform in order to take advantage of distributed computing. These results are useful for optical coherence tomography applications where bell-shaped pulses located in the second near-infrared window are ...

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    5. Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions

      Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions

      Background Optical coherence tomography (OCT) is a minimally invasive imaging technique, which utilizes the spatial and temporal coherence properties of optical waves backscattered from biological material. Recent advances in tunable lasers and infrared camera technologies have enabled an increase in the OCT imaging speed by a factor of more than 100, which is important for retinal imaging where we wish to study fast physiological processes in the biological tissue. However, the high scanning rate causes proportional decrease of the detector exposure time, resulting in a reduction of the system signal-to-noise ratio (SNR). One approach to improving the image quality of ...

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    6. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

      Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

      A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique ...

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    7. CHOROIDAL THICKNESS MEASURED WITH SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY BEFORE AND AFTER VITRECTOMY WITH INTERNAL LIMITING MEMBRANE PEELING FOR IDIOPATHIC EPIRETINAL MEMBRANES

      CHOROIDAL THICKNESS MEASURED WITH SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY BEFORE AND AFTER VITRECTOMY WITH INTERNAL LIMITING MEMBRANE PEELING FOR IDIOPATHIC EPIRETINAL MEMBRANES

      Purpose: In eyes with epiretinal membranes (ERMs), retinal arteries become dilated and tortuous. This may correlate with the hemodynamics of the affected areas and possibly with choroidal thickness. The aim of this study was to estimate choroidal thickness before and after vitrectomy for idiopathic ERM in the operated eye and in the unaffected fellow eye. Methods: A prospective study of 21 patients with idiopathic ERMs. We obtained swept source optical coherence tomography images that simultaneously evaluated the vitreous, retina, and choroid. We performed choroidal thickness measurements before pars plana vitrectomy with ERM removal and internal limiting membrane peeling. We took ...

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    8. A comprehensive model for correcting RNFL readings of varying signal strengths in CIRRUS Optical Coherence Tomography (OCT)

      A comprehensive model for correcting RNFL readings of varying signal strengths in CIRRUS Optical Coherence Tomography (OCT)

      Purpose. Develop a model for the CIRRUSTM HD-OCT that allows for the comparison of retinal nerve fiber layer (RNFL) thickness measurements with dissimilar signal strengths (SS) and accounts for test-re-test variability. Methods. RNFLs were obtained in normals using the CIRRUSTM optic disc cube 200x200 protocol during a single encounter. Five RNFL scans were obtained with a SS of 9-10. Diffusion lens filters were used to degrade SS to obtain five scans at each SS group of 7-8, 5-6, and 3-4. The relationship between average RNFL thickness and SS was established and an equation was developed to allow for adjustment of ...

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    9. Evaluating Dissociated Optic Nerve Fiber Layer Appearance Using En Face Layer Imaging Produced by Optical Coherence Tomography

      Evaluating Dissociated Optic Nerve Fiber Layer Appearance Using En Face Layer Imaging Produced by Optical Coherence Tomography

      Purpose: To investigate the incidence of and risk factors for a dissociated optic nerve fiber layer (DONFL) appearance after pars plana vitrectomy (PPV). Methods: We retrospectively reviewed 189 eyes that underwent PPV with internal limiting membrane removal and judged the presence/absence of an apparent DONFL based on en face layer images produced by spectral-domain optical coherence tomography (SD-OCT). Results: An apparent DONFL was observed in 47 (24.9%) eyes. The incidence of an apparent DONFL was significantly higher in the macular hole (MH) group (76.5%) than in the non-MH group (epiretinal membrane, diabetic macular edema, retinal vein occlusion ...

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    10. The cellular origins of the outer retinal bands in optical coherence tomography images

      The cellular origins of the outer retinal bands in optical coherence tomography images

      Purpose: To test the recently proposed hypothesis that the second OCT outer retinal band originates from the inner segment ellipsoid, by measuring: 1) thickness of this band within single cones, and 2) its respective distance from the external limiting membrane and outer segment tips. Methods: Adaptive optics OCT images were obtained from four normal subjects. Images were obtained at foveal (2∘) and perifoveal (5∘) locations. Cones (n = 9593) were identified and segmented in three dimensions using custom software. Features corresponding to bands 1, 2, and 3 were automatically identified. Thickness of band 2 was assessed in each cell by fitting ...

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    11. Endoscopic Eradication Therapy for Barrett's Esophagus

      Endoscopic Eradication Therapy for Barrett's Esophagus

      B arrett’s esophagus (BE) is the precursor lesion to esophageal adenocarcinoma, which in an invasive stage causes significant morbidity and mortality. Surgery was the mainstay of treatment for patients with high-grade dysplasia (HGD) and adenocarcinoma associated with BE. However, surgery in itself carries substantial morbidity. There has been tremendous progress in the minimally invasive treatment of BE in the past decade. The premise to be aggressive in treating dysplastic BE and early-stage adenocarcinoma is to prevent progression to an advanced-stage cancer. Most interventional endoscopists are comfortable treating dysplasia and intramucosal esophageal cancer, although recently there have been emerging data ...

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    12. Advanced Colonoscopic Imaging: Do New Technologies Improve Adenoma Detection?

      Advanced Colonoscopic Imaging: Do New Technologies Improve Adenoma Detection?

      C olorectal cancer (CRC) is the second leading cause of cancer-related mortality in the Western world. 1 Screening colonoscopy and polypectomy have become widely accepted as the most effective available methods for early detection and prevention of CRC and have shown a reduction in mortality in the screened population. 2 However, colonoscopy remains imperfect and several studies have raised concerns about the miss rate of adenomatous polyps during screening. The overall miss rate is approximately 20%, and ranges from 6% for large (10 mm) adenomas to 26% for diminutive (<5 mm) lesions. 3 Missing these adenomas is one of the ...

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    13. Abbott Expands Cataract Surgery Product Portfolio through U.S. Distribution Agreement with Carl Zeiss Meditec

      Abbott Expands Cataract Surgery Product Portfolio through U.S. Distribution Agreement with Carl Zeiss Meditec

      Abbott and Carl Zeiss Meditec announced today that they have entered into a nonexclusive commercial collaboration in the United States. Under this agreement, Abbott will offer each company’s suite of cataract surgery products when developing clinical and contracting solutions with customers in the United States. This comprehensive offering, including synergistic diagnostics, visualization systems, lens extraction systems, and intraocular lenses, provides surgeons with access to a complete cataract surgery portfolio to assist them in maximizing visual outcomes and streamlining patient flow. "Together with surgeons, Abbott is committed to delivering unsurpassed visual outcomes to patients," said Murthy Simhambhatla, Ph.D., senior ...

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    14. Automated Three-Dimensional Image Segmentation of Retinal OCT Images (Thesis)

      Automated Three-Dimensional Image Segmentation of Retinal OCT Images (Thesis)

      Optical coherence tomography (OCT) has become an essential tool in ophthalmology. The macular OCT images are three dimensional, high resolution and cross-sectional image of macula, which provides detailed structural information of various macular layers. Moreover macular OCT imaging is non-contact, noninvasive and real-time. OCT images can be obtained quickly and multiple times, this allows easy diagnosis and treatment progress monitoring. With advances in technology acquired dataset size is also increasing, which makes it impractical to manually segment macular layers in clinical environment. Thus need of fast and accurate segmentation algorithm is ever increasing. In this thesis two segmentation algorithms have ...

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    15. The Role of Multimodality Imaging Approach in Diagnosis and Stratification of Aborted Sudden Cardiac Death

      The Role of Multimodality Imaging Approach in Diagnosis and Stratification of Aborted Sudden Cardiac Death

      A 34-year-old man was admitted after an episode of aborted SCD. The initial investigation including electrocardiogram, chest X-ray, transthoracic echocardiogram and biomarkers were normal. Although coronary angiography showed non-severe stenosis, optical coherence tomography revealed severe obstruction in the artery with a layered appearance of the vessel wall; it was consistent with the presence of mural thrombus.

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    16. Progress of Intravascular Optical Coherence Tomography Image Technology and Vascular Three-Dimensional Reconstruction

      Progress of Intravascular Optical Coherence Tomography Image Technology and Vascular Three-Dimensional Reconstruction

      Intravascular optical coherence tomography (IV-OCT) is a new intervention imaging technology for the diagnosis of coronary heart disease. Because of its high-resolution and non-invasive characteristics, it is widely used in clinical medicine. It has a revolutionary impact on coronary artery disease diagnosis, prognosis and treatment decisions. This paper studied this hot topic, gave the basic concepts of intravascular OCT image sequences. In accordance with current development studies, the key technology for three-dimensional reconstruction of the coronary vascular system is proposed and analyzed. On this basis, we proposed future research directions on IV-OCT vascular three-dimensional reconstruction, including clinical trial frequency domain ...

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    17. Optical Coherence Tomography: A new era in dentistry

      Optical Coherence Tomography: A new era in dentistry

      Dental prostheses are very complex systems, heterogenous in structure, made up from various materials, with different physical properties. They have to satisfy high stress requirements as well as aesthetic challenges. The failures of dental prostheses lead to functional, aesthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. OCT is a tomography imaging technology capable of producing high-resolution cross-sectional images of the internal architecture of materials and tissues. This includes not only the images of normal and abnormal dental hard tissue structures but also teeth after several treatment methods. It can be used for non-invasive investigations for both in-vivo ...

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    18. Optical Coherence Tomography (OCT) – A New Diagnostic Tool in Psychiatry?

      Optical Coherence Tomography (OCT) – A New Diagnostic Tool in Psychiatry?

      Optical coherence tomography (OCT) is a non-invasive, contact-less imaging method which provides an “in vivo” representation of the retina. It allows the quantitative measurement of retinal nerve fibre layer thickness (RNFLT) and macula thickness (MT) and, in addition, is suitable to measure volumes (e. g., macula volume/MV). In the research of neurodegenerative diseases, OCT has been increasingly used and has shown its potential as a possible diagnostic tool over the course of the last few years. In recent years, the hypothesis that mental disorders like schizophrenia or unipolar depressive disorder have a degenerative component was established through a variety ...

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    19. Optical Coherence Tomography (OCT) Findings of Coronary Computed Tomography Angiography (CTA) Detected Vulnerable Plaque

      Optical Coherence Tomography (OCT) Findings of Coronary Computed Tomography Angiography (CTA) Detected Vulnerable Plaque

      Background: Recently, coronary computed tomography angiography (CTA) findings of positive vessel remodeling (PR) and low-attenuation plaque (LAP) have been reported to be associated with the development of acute coronary syndromes (ACS). The aim of this study was to examine the CTA detected vulnerable plaque characteristics by using intracoronary optical coherence tomography (OCT). Method and Result: A total of 16 patients with 16 lesions underwent PCI by using intracoronary OCT, after coronary CTA examination, were enrolled in this study. The CTA detected vulnerable plaque (CT-VP) was defined as LAP (<30 hounsfield unit (HU)) with PR of at least 110%. The lesions ...

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    20. Longitudinal necrotic shafts near TCFAs—A potential novel mechanism for plaque rupture to trigger ACS?

      Longitudinal necrotic shafts near TCFAs—A potential novel mechanism for plaque rupture to trigger ACS?

      It has been questioned for over 15 years why only less than 20% of TCFAs trigger ACS. We illustrate TCFA rupture into adjacent longitudinal necrotic shafts of massive amounts of thrombogenic material into the blood, leading to catastrophic clot formation. This is the potential mechanism for TCFAs triggering ACS. One case presented also illustrates the dangers of stent edges rupturing TCFAs.

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    21. The usefulness of multimodal imaging for differentiating pseudopapilloedema and true swelling of the optic nerve head: a review and case series

      The usefulness of multimodal imaging for differentiating pseudopapilloedema and true swelling of the optic nerve head: a review and case series

      Ophthalmic practitioners have to make a critical differential diagnosis in cases of an elevated optic nerve head. They have to discriminate between pseudopapilloedema (benign elevation of the optic nerve head) and true swelling of the optic nerve head. This decision has significant implications for appropriate patient management. Assessment of the optic disc prior to the advanced imaging techniques that are available today (particularly spectral domain optical coherence tomography and fundus autofluorescence), has mainly used diagnostic tools, such as funduscopy and retinal photography. As these traditional methods rely on the subjective assessment by the clinician, evaluation of the elevated optic nerve ...

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    22. Retinal Vascular Layers Imaged by Fluorescein Angiography and Optical Coherence Tomography Angiography

      Retinal Vascular Layers Imaged by Fluorescein Angiography and Optical Coherence Tomography Angiography

      Importance The retinal vasculature is involved in many ocular diseases that cause visual loss. Although fluorescein angiography is the criterion standard for evaluating the retina vasculature, it has risks of adverse effects and known defects in imaging all the layers of the retinal vasculature. Optical coherence tomography (OCT) angiography can image vessels based on flow characteristics and may provide improved information. Objective To investigate the ability of OCT angiography to image the vascular layers within the retina compared with conventional fluorescein angiography. Design, Setting, and Participants In this study, performed from March 14, 2014, through June 24, 2014, a total ...

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