1. All Articles

    25-48 of 15471 « 1 2 3 4 5 ... 643 644 645 »
    1. Automated 3D segmentation of multiple surfaces with a shared hole: segmentation of the neural canal opening in SD-OCT volumes

      Automated 3D segmentation of multiple surfaces with a shared hole: segmentation of the neural canal opening in SD-OCT volumes

      The need to segment multiple interacting surfaces is a common problem in medical imaging and it is often assumed that such surfaces are continuous within the confines of the region of interest. However, in some application areas, the surfaces of interest may contain a shared hole in which the surfaces no longer exist and the exact location of the hole boundary is not known a priori . The boundary of the neural canal opening seen in spectral-domain optical coherence tomography volumes is an example of a “hole” embedded with multiple surrounding surfaces. Segmentation approaches that rely on finding the surfaces alone ...

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    2. Speckle Reduction in Optical Coherence Tomography by Image Registration and Matrix Completion

      Speckle Reduction in Optical Coherence Tomography by Image Registration and Matrix Completion

      Speckle noise is problematic in optical coherence tomography (OCT). With the fast scan rate, swept source OCT scans the same position in the retina for multiple times rapidly and computes an average image from the multiple scans for speckle reduction. However, the eye movement poses some challenges. In this paper, we propose a new method for speckle reduction from multiply-scanned OCT slices. The proposed method applies a preliminary speckle reduction on the OCT slices and then registers them using a global alignment followed by a local alignment based on fast iterative diamond search. After that, low rank matrix completion using ...

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    3. Optical coherence tomography and 3-dimensional confocal structured imaging system–guided femtosecond laser capsulotomy versus manual continuous curvilinear capsulorhexis

      Optical coherence tomography and 3-dimensional confocal structured imaging system–guided femtosecond laser capsulotomy versus manual continuous curvilinear capsulorhexis

      Purpose To compare the features of capsulotomy obtained during femtosecond laser–assisted cataract surgery with those of continuous curvilinear capsulorhexis (CCC) obtained using a standard manual technique. Setting Ophthalmology Clinic, Department of Medicine and Science of Ageing, University G. D'Annunzio Chieti-Pescara, Chieti, Italy. Design Prospective randomized clinical study. Methods Candidates for cataract extraction were randomized into 1 of 3 groups as follows: Lensx femtosecond laser–assisted cataract surgery capsulotomy (laser group 1), Lensar femtosecond laser–assisted cataract surgery capsulotomy (laser group 2), and manual CCC (manual group). Results Each group comprised 30 eyes (30 patients). The capsulotomies in laser ...

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    4. Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

      Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

      Phase-sensitive optical coherence tomography (PhOCT) offers exquisite sensitivity to mechanical vibration in biological tissues. There is growing interest in using PhOCT for imaging the nanometer scale vibrations of the ear in animal models of hearing disorders. Swept-source-based systems offer fast acquisition speeds, suppression of common mode noise via balanced detection, and good signal roll-off. However, achieving high phase stability is difficult due to nonlinear laser sweeps and trigger jitter in a typical swept laser source. Here, we report on the initial application of a Vernier-tuned distributed Bragg reflector (VT-DBR) swept laser as the source for a fiber-based PhOCT system. The ...

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    5. Optical Coherence Tomography Guided Percutaneous Coronary Intervention With Stent Implantation

      Optical Coherence Tomography Guided Percutaneous Coronary Intervention With Stent Implantation

      Coronary artery disease is one of the most prevalent diseases in the western countries. A waxy substance called plaque can build up inside the coronary arteries. Over time, plaque can harden or rupture, and cause narrowing (stenosis) of the arteries and reduce the flow of oxygen-rich blood to the heart. The standard treatment of symptomatic coronary stenosis is percutaneous coronary intervention (PCI) with balloon dilation followed by stent implantation. A stent is a small metallic grid that stabilizes the coronary vessel wall after the balloon dilation. Currently, drug-eluting stents (DES) are the most widely used stent types. DESs consist of ...

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    6. Assessment of choroidal thickness before and after steep Trendelenburg position using swept-source optical coherence tomography

      Assessment of choroidal thickness before and after steep Trendelenburg position using swept-source optical coherence tomography

      Background To evaluate changes in choroidal thickness before and after steep Trendelenburg position (STP, 40° head-down) using automated segmentation software to analyse swept-source optical coherence tomography (SS-OCT) data. Methods The eyes of 20 healthy volunteers underwent a three-dimensional wide scanning protocol with SS-OCT (Topcon, Tokyo, Japan) at baseline, immediately after STP was initiated, and 5, 10 and 15 min after STP; blood pressure and heart rate were measured concurrently. The predictive mean difference was calculated using a generalised linear mixed model that adjusted for potential confounders. Results Mean choroidal thickness significantly and transiently increased immediately (268.18±9.24 μm ...

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    7. Assessment of laser induction of Bruch's membrane disruption in monkey by spectral-domain optical coherence tomography

      Assessment of laser induction of Bruch's membrane disruption in monkey by spectral-domain optical coherence tomography

      Purpose Laser-induced choroidal neovascularisation is a widely used model for age-related macular degeneration. The success rates of induction have been relatively low in large animals such as monkeys. Our study aimed to investigate the laser-induced damages to the Bruch's membrane of monkeys using the spectral-domain optical coherence tomography (OCT). Methods Laser photocoagulation was performed in the posterior and peripheral fundus of a rhesus monkey using a 532 nm laser. The lesions were examined by fundus photography and spectral-domain OCT immediately after the procedure. Fluorescein angiography was performed after 3 and 4 weeks in the animal to assess the development ...

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    8. Optical Coherence Tomography for the Monitoring of Neovascular Age-Related Macular Degeneration

      Optical Coherence Tomography for the Monitoring of Neovascular Age-Related Macular Degeneration

      Topic To compare the accuracy of optical coherence tomography (OCT) with alternative tests for monitoring neovascular age-related macular degeneration (nAMD) and detecting disease activity among eyes previously treated for this condition. Clinical Relevance Traditionally, fundus fluorescein angiography (FFA) has been considered the reference standard to detect nAMD activity, but FFA is costly and invasive. Replacement of FFA by OCT can be justified if there is a substantial agreement between tests. Methods Systematic review and meta-analysis. The index test was OCT. The comparator tests were visual acuity, clinical evaluation (slit lamp), Amsler chart, color fundus photographs, infrared reflectance, red-free images and ...

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    9. Aqueous reaction quantification after phacoemulsification: Fourier-domain optical coherence tomography versus slitlamp biomicroscopy

      Aqueous reaction quantification after phacoemulsification: Fourier-domain optical coherence tomography versus slitlamp biomicroscopy

      Purpose To compare anterior chamber cell detection after phacoemulsification between Fourier-domain optical coherence tomography (OCT) and slitlamp biomicroscopy. Design Observational prospective comparative case series. Setting Dr. Agarwal's Eye Hospital and Eye Research Centre, Chennai, India. Methods Eyes with preoperative nuclear opalescence (NO) grades 1 to 3 that had phacoemulsification with posterior chamber intraocular lens implantation were included. Slitlamp biomicroscopy and Fourier-domain OCT (Cirrus HD) of the anterior chamber were performed 1 day postoperatively. The results were evaluated, and a correlation analysis between the results and preoperative NO, effective phacoemulsification time (EPT), postoperative central corneal thickness (CCT), and intraocular pressure ...

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      Mentions: Amar Agarwal
    10. Correlation of corneal thickness and volume with intraoperative phacoemulsification parameters using Scheimpflug imaging and optical coherence tomography

      Correlation of corneal thickness and volume with intraoperative phacoemulsification parameters using Scheimpflug imaging and optical coherence tomography

      Purpose To evaluate post-phacoemulsification corneal edema using central corneal thickness (CCT) and central corneal volume (CCV) derived from Scheimpflug imaging, optical coherence tomography (OCT), and ultrasound (US) pachymetry and to correlate CCV with phacoemulsification parameters. Setting Department of Ophthalmology, Boston Medical Center, Boston, Massachusetts, USA. Design Prospective case study. Methods Scheimpflug imaging (Pentacam HR), OCT (Cirrus HD-OCT), and US pachymetry (Pachmate) were used to measure the CCT, CCV, and phacoemulsification parameters after uneventful phacoemulsification over a 1-month follow-up. Results In the 16 eyes assessed, the Scheimpflug CCT was less than the US CCT preoperatively ( P =.01) and 1 week postoperatively ...

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    11. Feature of the Week 10/19/14: Automated Classification of Optical Coherence Tomography Images for the Diagnosis of Oral Malignancy in the Hamster Cheek Pouch

      Feature of the Week 10/19/14: Automated Classification of Optical Coherence Tomography Images for the Diagnosis of Oral Malignancy in the Hamster Cheek Pouch

      Most studies evaluating the potential of optical coherence tomography (OCT) for the diagnosis of oral cancer are based on visual assessment of OCT B-scans by trained experts. Human interpretation of the large pool of data acquired by modern high-speed OCT systems, however, can be cumbersome and extremely time consuming. Development of image analysis methods for automated and quantitative OCT image analysis could therefore facilitate the evaluation of such a large volume of data. We report automated algorithms for quantifying structural features that are associated with the malignant transformation of the oral epithelium based on image processing of OCT data. The ...

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    12. Fabrication method of ultra-small gradient-index fiber probe

      Fabrication method of ultra-small gradient-index fiber probe

      Fabrication method and device of ultra-small gradient-index (GRIN) fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography (OCT) imaging. The beam-expanding effect of no-core fiber (NCF) and the focusing properties of the GRIN fiber lens were analyzed based on the model of GRIN fiber probe consisting of single-mode fiber (SMF), NCF and GRIN fiber lens. A stereo microscope based system was developed to fabricate the GRIN fiber probe. A fiber fusion splicer and an ultrasonic cleaver were used to weld and cut the fiber respectively. A confocal microscopy was used to measure ...

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    13. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging

      All-fiber wavelength swept ring laser based on  Fabry-Perot filter for optical frequency domain  imaging

      Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral ...

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    14. Comparison of Circulating Dendritic Cells and Monocyte Subsets at Different Stages of Atherosclerosis: insights from optical coherence tomography

      Comparison of Circulating Dendritic Cells and Monocyte Subsets at Different Stages of Atherosclerosis: insights from optical coherence tomography

      Objectives Proinflammatory dendritic cells (DC) and monocytes are critically involved in the proceeding and destabilization of atherosclerosis. Recent studies have reported potential associations of specific patterns of circulating DCs and monocytes with the incidence of coronary artery disease (CAD) and ST-elevation myocardial infarction (STEMI); however, further information of DC and monocyte subsets on plaque morphology and vulnerability is uncertain and required. Methods Forty-seven CAD patients with borderline lesions (stenosis 50%-70%) by coronary angiography (CAG) were enrolled, while 31 subjects free of luminal diameter narrowing ≥ 50% served as controls. Likewise, 35 patients with STEMI were enrolled and confirmed with the ...

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    15. Swept-Source Optical Coherence Tomography Features of Choroidal Nevi

      Swept-Source Optical Coherence Tomography Features of Choroidal Nevi

      Purpose To investigate the morphological characteristics of choroidal nevi using swept-source optical coherence tomography and compare this with enhanced-depth optical coherence tomography. Design Retrospective observational case series Methods One choroidal nevus each from 30 eyes of 30 patients was included and received imaging with swept-source OCT (SS-OCT) and enhanced-depth imaging OCT (EDI-OCT). For SS-OCT, a scan acquisition protocol was utilized involving 12mm horizontal and vertical scans in the posterior fundus. The main outcome measures were morphological features of choroidal nevi obtained with SS-OCT imaging. These features were compared to images obtained with EDI-OCT. A two-tailed Fisher’s exact test was ...

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    16. 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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    17. 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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    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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