1. 1-24 of 183 1 2 3 4 5 6 7 8 »
    1. On the possibility of producing true real-time retinal cross-sectional images using a graphics processing unit enhanced master-slave optical coherence tomography system

      On the possibility of producing true real-time retinal cross-sectional images using a graphics processing unit enhanced master-slave optical coherence tomography system

      In a previous report, we demonstrated master-slave optical coherence tomography (MS-OCT), an OCT method that does not need resampling of data and can be used to deliver en face images from several depths simultaneously. In a separate report, we have also demonstrated MS-OCT’s capability of producing cross-sectional images of a quality similar to those provided by the traditional Fourier domain (FD) OCT technique, but at a much slower rate. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real time ...

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    2. Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography

      Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography

      Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle “blinking” and ...

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    3. Microscope-integrated optical coherence tomography for image-aided positioning of glaucoma surgery

      Microscope-integrated optical coherence tomography for image-aided positioning of glaucoma surgery

      Most glaucoma surgeries involve creating new aqueous outflow pathways with the use of a small surgical instrument. This article reported a microscope-integrated, real-time, high-speed, swept-source optical coherence tomography system (SS-OCT) with a 1310-nm light source for glaucoma surgery. A special mechanism was designed to produce an adjustable system suitable for use in surgery. A two-graphic processing unit architecture was used to speed up the data processing and real-time volumetric rendering. The position of the surgical instrument can be monitored and measured using the microscope and a grid-inserted image of the SS-OCT. Finally, experiments were simulated to assess the effectiveness of ...

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    4. Wide-field imaging of retinal vasculature using optical coherence tomography-based microangiography provided by motion tracking.

      Wide-field imaging of retinal vasculature using optical coherence tomography-based microangiography provided by motion tracking.

      Optical coherence tomography (OCT)-based optical microangiography (OMAG) is a high-resolution, noninvasive imaging technique capable of providing three-dimensional in vivo blood flow visualization within microcirculatory tissue beds in the eye. Although the technique has demonstrated early clinical utility by imaging diseased eyes, its limited field of view (FOV) and the sensitivity to eye motion remain the two biggest challenges for the widespread clinical use of the technology. Here, we report the results of retinal OMAG imaging obtained from a Zeiss Cirrus 5000 spectral domain OCT system with motion tracking capability achieved by a line scan ophthalmoscope (LSO). The tracking LSO ...

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    5. En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

      En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

      An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans ( 2 × 2     mm ) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The ...

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    6. Optical coherence tomography system requirements for clinical diagnostic middle ear imaging

      Optical coherence tomography system requirements for clinical diagnostic middle ear imaging

      Noninvasive middle ear imaging using optical coherence tomography (OCT) presents some unique challenges for real-time, clinical use in humans. We present results from a two-dimensional/three-dimensional OCT system built to assess the imaging requirements of clinical middle ear imaging, and the technical challenges associated with them. These include the need to work at a low numerical aperture, the deleterious effects of transtympanic imaging on image quality at the ossicles, sensitivity requirements for clinical fidelity of images at real-time rates, and the high dynamic-range requirements of the ear. We validated the system by imaging cadaveric specimens with simulated disorders to show ...

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    7. Multimodal noncontact photoacoustic and optical coherence tomography imaging using wavelength-division multiplexing

      Multimodal noncontact photoacoustic and optical coherence tomography imaging using wavelength-division multiplexing

      We present multimodal noncontact photoacoustic (PA) and optical coherence tomography (OCT) imaging. PA signals are acquired remotely on the surface of a specimen with a Mach-Zehnder interferometer. The interferometer is realized in a fiber-optic network using a fiber laser at 1550 nm as the source. In the same fiber-optic network, a spectral-domain OCT system is implemented. The OCT system utilizes a supercontinuum light source at 1310 nm and a spectrometer with an InGaAs line array detector. Light from the fiber laser and the OCT source is multiplexed into one fiber using a wavelength-division multiplexer; the same objective is used for ...

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    8. Measuring skin aging using optical coherence tomography in vivo: a validation study

      Measuring skin aging using optical coherence tomography in vivo: a validation study

      Dermal and epidermal structures in human skin change during intrinsic and extrinsic aging. Epidermal thickness is one of the most often reported parameters for the assessment of skin aging in cross-sectional images captured by optical coherence tomography (OCT). We aimed to identify further parameters for the noninvasive measurement of skin aging of sun-exposed and sun-protected areas utilizing OCT. Based on a literature review, seven parameters were inductively developed. Three independent raters assessed these parameters using four-point scales on images of female subjects of two age groups. All items could be detected and quantified in our sample. Interrater agreement ranged between ...

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    9. Effects of titanium dioxide nanoparticles coupled with diode laser on optical properties of in vitro normal and cancerous human lung tissues studied with optical coherence tomography and diffuse reflectance spectra

      Effects of titanium dioxide nanoparticles coupled with diode laser on optical properties of in vitro normal and cancerous human lung tissues studied with optical coherence tomography and diffuse reflectance spectra

      The objective is to investigate the effects of two different sized (60 and 100 nm) titanium dioxide ( TiO 2 ) nanoparticles (NPs) penetration and accumulation in in vitro human normal lung (NL) tissue, lung squamous cell carcinoma (LSCC) tissue, and 650-nm diode laser-pretreated tissue on their optical properties studied with optical coherence tomography monitoring and diffuse reflectance (DR) spectra measurement. As with TiO 2 NPs penetrating into the tissues, the intensities of DR of the samples increase, and then the enhancements of DR and the attenuation coefficients of the tissues were quantitatively calculated. The results suggest that 650-nm diode laser pretreatment ...

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    10. In vivo optical microscopy of peripheral nerve myelination with polarization sensitive-optical coherence tomography

      In vivo optical microscopy of peripheral nerve myelination with polarization sensitive-optical coherence tomography

      Assessing nerve integrity and myelination after injury is necessary to provide insight for treatment strategies aimed at restoring neuromuscular function. Currently, this is largely done with electrical analysis, which lacks direct quantitative information. In vivo optical imaging with sufficient imaging depth and resolution could be used to assess the nerve microarchitecture. In this study, we examine the use of polarization sensitive-optical coherence tomography (PS-OCT) to quantitatively assess the sciatic nerve microenvironment through measurements of birefringence after applying a nerve crush injury in a rat model. Initial loss of function and subsequent recovery were demonstrated by calculating the sciatic function index ...

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    11. Usage of polarization-sensitive optical coherence tomography for investigation of collagen cross-linking

      Usage of polarization-sensitive optical coherence tomography for investigation of collagen cross-linking

      To investigate morphological alternation in corneal stroma induced by collagen cross-linking (CXL) treatment, polarization-sensitive optical coherence tomography (PS-OCT) capable of providing scattering, phase retardation, and degree of polarization uniformity (DOPU) images were employed on fresh bovine cornea. Significant corneal thickness reduction was observed after the CXL procedure, and its variation was quantitatively analyzed. From the scattering contrast, a hyperscattering region was observed in the anterior of the cornea immediately after the CXL procedure and its range increased with time. Within the scattering region, a slow increase was observed in the phase retardation image, and a discriminable characteristic was found in ...

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    12. Imaging of nanoparticle-labeled stem cells using magnetomotive optical coherence tomography, laser speckle reflectometry, and light microscopy

      Imaging of nanoparticle-labeled stem cells using magnetomotive optical coherence tomography, laser speckle reflectometry, and light microscopy

      Cell transplantation and stem cell therapy are promising approaches for regenerative medicine and are of interest to researchers and clinicians worldwide. However, currently, no imaging technique that allows three-dimensional in vivo inspection of therapeutically administered cells in host tissues is available. Therefore, we investigate magnetomotive optical coherence tomography (MM-OCT) of cells labeled with magnetic particles as a potential noninvasive cell tracking method. We develop magnetomotive imaging of mesenchymal stem cells for future cell therapy monitoring. Cells were labeled with fluorescent iron oxide nanoparticles, embedded in tissue-mimicking agar scaffolds, and imaged using a microscope setup with an integrated MM-OCT probe. Magnetic ...

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    13. Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

      Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

      We present an ultrahigh-speed optical coherence tomography (OCT) based on an all-optical swept-source with an A-scan rate of 40 MHz. The inertia-free swept-source, which has its output power of 41.2 mW and tuning range of 40 nm and high scan linearity in wavenumber with Pearson’s correlation coefficients r of 0.9996, consists of a supercontinuum laser, an optical band-pass filter, a linearly chirped fiber Bragg grating, an erbium-doped fiber amplifier, and two buffer stages. With sensitivity of 87 dB, high-speed OCT imaging of biological tissue in vivo is also demonstrated.

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    14. Speckle reduction in optical coherence tomography by two-step image registration

      Speckle reduction in optical coherence tomography by two-step image registration

      The image quality of optical coherence tomography can be severely influenced by speckle noise (i.e., signal-degrading speckle). Averaging multiple B-scans can effectively suppress speckle noise. Because of sample motion, images subject to averaging must be aligned exactly. We propose a two-step image registration scheme that combines global and local registrations for speckle reduction by the averaging of multiple B-scans. The method begins with a global registration to compensate for overall motion, which is estimated based on the rigid transformation model involving translation and rotation. Then each A-scan is aligned by cross-correlation using a graph-based algorithm, followed by a pixel ...

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    15. Evaluation of the usefulness of three-dimensional optical coherence tomography in a guinea pig model of endolymphatic hydrops induced by surgical obliteration of the endolymphatic duct

      Evaluation of the usefulness of three-dimensional optical coherence tomography in a guinea pig model of endolymphatic hydrops induced by surgical obliteration of the endolymphatic duct

      Optical coherence tomography (OCT) has advanced significantly over the past two decades and is currently used extensively to monitor the internal structures of organs, particularly in ophthalmology and dermatology. We used ethylenediamine tetra-acetic acid (EDTA) to decalcify the bony walls of the cochlea and investigated the inner structures by deep penetration of light into the cochlear tissue using OCT on a guinea pig model of endolymphatic hydrops (EH), induced by surgical obliteration of the endolymphatic duct. The structural and functional changes associated with EH were identified using OCT and auditory brainstem response tests, respectively. We also evaluated structural alterations in ...

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    16. Quantitative optical coherence tomography imaging of intermediate flow defect phenotypes in ciliary physiology and pathophysiology

      Quantitative optical coherence tomography imaging of intermediate flow defect phenotypes in ciliary physiology and pathophysiology

      Cilia-driven fluid flow is a critical yet poorly understood aspect of pulmonary physiology. Here, we demonstrate that optical coherence tomography-based particle tracking velocimetry can be used to quantify subtle variability in cilia-driven flow performance in Xenopus , an important animal model of ciliary biology. Changes in flow performance were quantified in the setting of normal development, as well as in response to three types of perturbations: mechanical (increased fluid viscosity), pharmacological (disrupted serotonin signaling), and genetic (diminished ciliary motor protein expression). Of note, we demonstrate decreased flow secondary to gene knockdown of kif3a , a protein involved in ciliogenesis, as well as ...

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    17. Multiframe denoising of high-speed optical coherence tomography data using interframe and intraframe priors

      Multiframe denoising of high-speed optical coherence tomography data using interframe and intraframe priors

      Optical coherence tomography (OCT) is an important interferometric diagnostic technique, which provides cross-sectional views of biological tissues’ subsurface microstructures. However, the imaging quality of high-speed OCT is limited by the large speckle noise. To address this problem, we propose a multiframe algorithmic method to denoise OCT volume. Mathematically, we build an optimization model which forces the temporally registered frames to be low-rank and the gradient in each frame to be sparse, under the constraints from logarithmic image formation and nonuniform noise variance. In addition, a convex optimization algorithm based on the augmented Lagrangian method is derived to solve the above ...

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    18. One specific velocity color mapping using optical coherence tomography

      One specific velocity color mapping using optical coherence tomography

      Depth resolved coherence gating along with Doppler shift detection of the carrier frequency is used for one predetermined velocity mapping in different flows. Bidirectional rapid scanning optical delay of optical coherence tomography system is applied in the reference arm. Tilted capillary entry is used as a hydrodynamic phantom to model a sign-variable flow with complex geometry. Structural and one specific velocity images are obtained from the scanning interferometer signal processing in the frequency domain using analog and digital filtering. A standard structural image is decomposed into three parts: stationary object, and positive and negative velocity distributions. The latter two show ...

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    19. Comparative analysis of combined spectral and optical tomography methods for detection of skin and lung cancers

      Comparative analysis of combined spectral and optical tomography methods for detection of skin and lung cancers

      Malignant skin tumors of different types were studied in vivo using optical coherence tomography (OCT), backscattering (BS), and Raman spectroscopy (RS). A multimodal method is proposed for early cancer detection based on complex analysis of OCT images by their relative alteration of scattered-radiation spectral intensities between malignant and healthy tissues. An increase in average accuracy of diagnosis was observed for a variety of cancer types (9% sensitivity, 8% specificity) by a multimodal RS-BS-OCT system in comparison with any of the three methods used separately. The proposed approach equalizes the processing rates for all methods and allows for simultaneous imaging and ...

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      Mentions: Pavel Zakharov
    20. Quantitative assessment of corneal viscoelasticity using optical coherence elastography and a modified Rayleigh–Lamb equation

      Quantitative assessment of corneal viscoelasticity using optical coherence elastography and a modified Rayleigh–Lamb equation

      We demonstrate the use of a modified Rayleigh–Lamb frequency equation in conjunction with noncontact optical coherence elastography to quantify the viscoelastic properties of the cornea. Phase velocities of air-pulse-induced elastic waves were extracted by spectral analysis and used for calculating the Young’s moduli of the samples using the Rayleigh–Lamb frequency equation (RLFE). Validation experiments were performed on 2% agar phantoms ( n = 3 ) and then applied to porcine corneas ( n = 3 ) in situ . The Young’s moduli of the porcine corneas were estimated to be ∼ 60     kPa with a shear viscosity ∼ 0.33     Pa ⋅ s . The results demonstrate ...

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    21. Optical coherence tomography based microangiography for quantitative monitoring of structural and vascular changes in a rat model of acute uveitis in vivo: a preliminary study

      Optical coherence tomography based microangiography for quantitative monitoring of structural and vascular changes in a rat model of acute uveitis in vivo: a preliminary study

      Uveitis models in rodents are important in the investigation of pathogenesis in human uveitis and the development of appropriate therapeutic strategies for treatment. Quantitative monitoring of ocular inflammation in small animal models provides an objective metric to assess uveitis progression and/or therapeutic effects. We present a new application of optical coherence tomography (OCT) and OCT-based microangiography (OMAG) to a rat model of acute anterior uveitis induced by intravitreal injection of a killed mycobacterial extract. OCT/OMAG is used to provide noninvasive three-dimensional imaging of the anterior segment of the eyes prior to injection (baseline) and two days post-injection (peak ...

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    22. Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror

      Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror

      We present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a ...

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    23. Optical coherence tomography guided microinjections in live mouse embryos: high-resolution targeted manipulation for mouse embryonic research

      Optical coherence tomography guided microinjections in live mouse embryos: high-resolution targeted manipulation for mouse embryonic research

      The ability to conduct highly localized delivery of contrast agents, viral vectors, therapeutic or pharmacological agents, and signaling molecules or dyes to live mammalian embryos is greatly desired to enable a variety of studies in the field of developmental biology, such as investigating the molecular regulation of cardiovascular morphogenesis. To meet such a demand, we introduce, for the first time, the concept of employing optical coherence tomography (OCT)-guide microinjections in live mouse embryos, which provides precisely targeted manipulation with spatial resolution at the micrometer scale. The feasibility demonstration is performed with experimental studies on cultured live mouse embryos at ...

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    24. Three-dimensional segmentation and reconstruction of the retinal vasculature from spectral-domain optical coherence tomography

      Three-dimensional segmentation and reconstruction of the retinal vasculature from spectral-domain optical coherence tomography

      We reconstruct the three-dimensional shape and location of the retinal vascular network from commercial spectral-domain (SD) optical coherence tomography (OCT) data. The two-dimensional location of retinal vascular network on the eye fundus is obtained through support vector machines classification of properly defined fundus images from OCT data, taking advantage of the fact that on standard SD-OCT, the incident light beam is absorbed by hemoglobin, creating a shadow on the OCT signal below each perfused vessel. The depth-wise location of the vessel is obtained as the beginning of the shadow. The classification of crossovers and bifurcations within the vascular network is ...

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    1-24 of 183 1 2 3 4 5 6 7 8 »
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