1. 1-24 of 262 1 2 3 4 ... 9 10 11 »
    1. Effects of Methotrexate in a Rabbit Model of In-Stent Neoatherosclerosis: An Optical Coherence Tomography Study

      Effects of Methotrexate in a Rabbit Model of In-Stent Neoatherosclerosis: An Optical Coherence Tomography Study

      This study used optical coherence tomography (OCT) to investigate the effects of systemic methotrexate, in combination with a drug-eluting stent, on in-stent neoatherosclerosis in a rabbit model. Sirolimus-eluting stents were surgically implanted in the right common carotid arteries of 200 male New Zealand White rabbits; the animals received a high-fat diet, beginning one week before stent implantation. Each animal was randomly assigned to 1 of 4 groups, receiving intravenous injections of either methotrexate (0.4 mg/kg) or placebo weekly for 4 or 12 weeks. Stented arterial segments were harvested after stenting for 4 or 12 weeks, and processed for ...

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    2. Automated Internal Classification of Beadless Chinese ZhuJi Fleshwater Pearls based on Optical Coherence Tomography Images

      Automated Internal Classification of Beadless Chinese ZhuJi Fleshwater Pearls based on Optical Coherence Tomography Images

      Optical coherence tomography (OCT) has been applied to inspect the internal defect of beadless Chinese ZhuJi fleshwater pearls. A novel fully automated algorithm is proposed to classify between normal and defective sub-layer in nacre layer. Our algorithm utilizes the graph segmentation approach to estimate the up and down boundaries of defect sub-layers from flattened and cropped image, and also proposes the strategy for edge and weight construction in segmentation process. The vertical gradients of boundary pixels are used to make grading decision. The algorithm is tested by typical pearl samples, and achieves 100% classification accuracy. The experiment result shows the ...

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    3. Micro-optical coherence tomography of the mammalian cochlea

      Micro-optical coherence tomography of the mammalian cochlea

      The mammalian cochlea has historically resisted attempts at high-resolution, non-invasive imaging due to its small size, complex three-dimensional structure, and embedded location within the temporal bone. As a result, little is known about the relationship between an individual’s cochlear pathology and hearing function, and otologists must rely on physiological testing and imaging methods that offer limited resolution to obtain information about the inner ear prior to performing surgery. Micro-optical coherence tomography (μOCT) is a non-invasive, low-coherence interferometric imaging technique capable of resolving cellular-level anatomic structures. To determine whether μOCT is capable of resolving mammalian intracochlear anatomy, fixed guinea pig ...

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    4. Real-time Functional Analysis of Inertial Microfluidic Devices via Spectral Domain Optical Coherence Tomography

      Real-time Functional Analysis of Inertial Microfluidic Devices via Spectral Domain Optical Coherence Tomography

      We report the application of spectral-domain optical coherence tomography (SD-OCT) technology that enables real-time functional analysis of sorting microparticles and cells in an inertial microfluidic device. We demonstrated high-speed, high-resolution acquisition of cross-sectional images at a frame rate of 350 Hz, with a lateral resolution of 3 μm and an axial resolution of 1 μm within the microfluidic channel filled with water. We analyzed the temporal sequence of cross-sectional SD-OCT images to determine the position and diameter of microspheres in a spiral microfluidic channel under various flow rates. We used microspheres with known diameters to validate the sub-micrometer precision of ...

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      Mentions: Ji Yi Hao F. Zhang
    5. Multiscale dispersion-state characterization of nanocomposites using optical coherence tomography

      Multiscale dispersion-state characterization of nanocomposites using optical coherence tomography

      Nanocomposite materials represent a success story of nanotechnology. However, development of nanomaterial fabrication still suffers from the lack of adequate analysis tools. In particular, achieving and maintaining well-dispersed particle distributions is a key challenge, both in material development and industrial production. Conventional methods like optical or electron microscopy need laborious, costly sample preparation and do not permit fast extraction of nanoscale structural information from statistically relevant sample volumes. Here we show that optical coherence tomography (OCT) represents a versatile tool for nanomaterial characterization, both in a laboratory and in a production environment. The technique does not require sample preparation and ...

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    6. Change of Optical Intensity during Healing Process of Corneal Wound on Anterior Segment Optical Coherence Tomography

      Change of Optical Intensity during Healing Process of Corneal Wound on Anterior Segment Optical Coherence Tomography

      The purpose of this study is to investigate the process of corneal wound healing after penetrating injury with the change in optical intensity on anterior segment optical coherence tomography (AS-OCT) and to investigate factors associated with severity of corneal scar. Forty-seven eyes from 47 patients with repaired corneal laceration were included. AS-OCT was performed on 1day, 1week, 1, 3 and 6 months after primary repair. Internal aberrations of wound edges were observed on AS-OCT images. Parameters including height of steps, width of gaps, maximal corneal thickness, area and optical intensity of corneal wound/scar were measured. The relationship between the ...

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      Mentions: Haoyu Chen
    7. Live volumetric (4D) visualization and guidance of in vivo human ophthalmic surgery with intraoperative optical coherence tomography

      Live volumetric (4D) visualization and guidance of in vivo human ophthalmic surgery with intraoperative optical coherence tomography

      Minimally-invasive microsurgery has resulted in improved outcomes for patients. However, operating through a microscope limits depth perception and fixes the visual perspective, which result in a steep learning curve to achieve microsurgical proficiency. We introduce a surgical imaging system employing four-dimensional (live volumetric imaging through time) microscope-integrated optical coherence tomography (4D MIOCT) capable of imaging at up to 10 volumes per second to visualize human microsurgery. A custom stereoscopic heads-up display provides real-time interactive volumetric feedback to the surgeon. We report that 4D MIOCT enhanced suturing accuracy and control of instrument positioning in mock surgical trials involving 17 ophthalmic surgeons ...

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    8. Optical coherence microscopy in 1700 nm spectral band for high-resolution label-free deep-tissue imaging

      Optical coherence microscopy in 1700 nm spectral band for high-resolution label-free deep-tissue imaging

      Optical coherence microscopy (OCM) is a label-free, high-resolution, three-dimensional (3D) imaging technique based on optical coherence tomography (OCT) and confocal microscopy. Here, we report that the 1700-nm spectral band has the great potential to improve the imaging depth in high-resolution OCM imaging of animal tissues. Recent studies to improve the imaging depth in OCT revealed that the 1700-nm spectral band is a promising choice for imaging turbid scattering tissues due to the low attenuation of light in the wavelength region. In this study, we developed high-resolution OCM by using a high-power supercontinuum source in the 1700-nm spectral band, and compared ...

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    9. Optical coherence tomography characteristics of different types of big bubbles seen in deep anterior lamellar keratoplasty by the big bubble technique

      Optical coherence tomography characteristics of different types of big bubbles seen in deep anterior lamellar keratoplasty by the big bubble technique

      Purpose To define optical coherence tomography (OCT) characteristics of type-1, type-2, and mixed big bubbles (BB) seen in deep anterior lamellar keratoplasty. Methods Human sclero-corneal discs were obtained from UK (30) and Canada (16) eye banks. Air was injected into corneal stroma until a BB formed. UK samples were fixed in formalin before scanning with Fourier-domain (FD-OCT). One pair of each type of BB was scanned fresh. All BB obtained from Canada were scanned fresh with time-domain (TD-OCT). For each OCT machine used, type-1 BB from which Descemets membrane (DM) was partially peeled, were also scanned. The morphological characteristics of ...

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    10. Post-Mortem Corneal Thickness Measurements with a Portable Optical Coherence Tomography System: a Reliability Study

      Post-Mortem Corneal Thickness Measurements with a Portable Optical Coherence Tomography System: a Reliability Study

      The purpose of this study was to determine the repeatability and reproducibility of post-mortem central corneal thickness (CCT) measurements by using a real-time, portable optical coherence tomography (OCT) system on an animal model, and to prospectively evaluate the time-course of post-mortem changes in CCT. Forty-six ocular globes of sheep ( Ovis aries ) were analyzed with a portable spectral-domain OCT device by two operators at different postmortem intervals (PMIs) as follows: immediately (i.e. within 10 minutes), at the 30 th minute, at the 1 st , 6 th , 12 th , 24 th and 48 th hour, and later (up to the 96 ...

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    11. Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

      Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

      Recent developments in optical coherence tomography (OCT) systems for the cornea have limited resolution or acquisition speed. In this study we aim to evaluate the use of a ‘micro-OCT’ (μOCT ~1 μm axial resolution) compared to existing imaging modalities using animal models of corneal endothelial disease. We used established cryoinjury and bullous keratopathy models in Sprague Dawley rats comparing ex vivo μOCT imaging in normal and diseased eyes to (1) histology; (2) in vivo confocal microscopy (IVCM); and (3) scanning electron microscopy (SEM). Qualitative and quantitative comparisons amongst imaging modalities were performed using mean endothelial cell circularity [(4π × Area)/Perimeter ...

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    12. Spectral-domain optical coherence tomography findings of the macula in 500 consecutive patients with uveitis

      Spectral-domain optical coherence tomography findings of the macula in 500 consecutive patients with uveitis

      Purpose To analyze the macular structure in a large series of consecutive patients with different types of uveitis using spectral-domain optical coherence tomography (SD-OCT). Patients and methods Five hundred eyes of 500 consecutive patients with anterior, intermediate, posterior, and panuveitis underwent standardized macular examination using SD-OCT. Central retinal thickness (CRT), macular volume (MV), and presence of cystoid macular edema (CME), diffuse macular edema (DME), serous retinal detachment (SRD), epiretinal membrane with (ERM + ) and without (ERM−) retinal surface wrinkling were determined. Results The anatomic location of inflammation affected significantly CRT and MV (P<0.001, respectively), with the highest values in ...

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    13. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

      In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

      Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to ...

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    14. Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

      Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

      Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex ...

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    15. Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography

      Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography

      The decorrelation signals in optical coherence tomography angiography (OCTA) are derived from the flow of erythrocytes and concomitantly delineate the retinal vasculature. We compared the structural and functional characteristics of vascular lesions visualized in fluorescein angiography (FA), OCTA, and en-face OCT images in 53 eyes (28 patients) with diabetic retinopathy (DR). The foveal avascular zone (FAZ) areas in OCTA images in the superficial layer almost corresponded to those in FA images. The FAZ areas in the en-face OCT images in the superficial layer were smaller than those in the FA images and correlated with each other, which agreed with the ...

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    16. Choroidal changes observed with enhanced depth imaging optical coherence tomography in patients with mild Graves orbitopathy

      Choroidal changes observed with enhanced depth imaging optical coherence tomography in patients with mild Graves orbitopathy

      Purpose To evaluate the choroidal thickness in patients with Graves orbitopathy (GO) using enhanced depth imaging-optical coherence tomography (EDI-OCT). Methods Thirty-one patients with GO were evaluated prospectively. All subjects underwent ophthalmologic examination including best-corrected visual acuity, intraocular pressure measurement, biomicroscopic, and fundus examination. Choroidal thickness was measured at the central fovea. In addition, visual evoked potential measurement and visual field evaluation were performed. Results The mean choroidal thickness was 377.8±7.4   μ in the GO group, and 334±13.7   μ in the control group. (P = 0.004). There was a strong correlation between the choridal thickness and the clinical ...

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    17. Lens-based wavefront sensorless adaptive optics swept source OCT

      Lens-based wavefront sensorless adaptive optics swept source OCT

      Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high ...

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    18. Myopic Macular Retinoschisis in Teenagers: Clinical Characteristics and Spectral Domain Optical Coherence Tomography Findings

      Myopic Macular Retinoschisis in Teenagers: Clinical Characteristics and Spectral Domain Optical Coherence Tomography Findings

      To investigate the morphological characteristics of myopic macular retinoschisis (MRS) in teenagers with high myopia, six male (9 eyes) and 3 female (4 eyes) teenagers with typical MRS identified from chart review were evaluated. All cases underwent complete ophthalmic examinations including best corrected visual acuity (BCVA), indirect ophthalmoscopy, colour fundus photography, B-type ultrasonography, axial length measurement, and spectral-domain optical coherence tomography (SD-OCT). The average age was 17.8 ± 1.5 years, average refractive error was −17.04 ± 3.04D, average BCVA was 0.43 ± 0.61, and average axial length was 30.42 ± 1.71 mm. Myopic macular degenerative changes ...

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    19. Longitudinal, label-free, quantitative tracking of cell death and viability in a 3D tumor model with OCT

      Longitudinal, label-free, quantitative tracking of cell death and viability in a 3D tumor model with OCT

      Three-dimensional in vitro tumor models are highly useful tools for studying tumor growth and treatment response of malignancies such as ovarian cancer. Existing viability and treatment assessment assays, however, face shortcomings when applied to these large, complex, and heterogeneous culture systems. Optical coherence tomography (OCT) is a noninvasive, label-free, optical imaging technique that can visualize live cells and tissues over time with subcellular resolution and millimeters of optical penetration depth. Here, we show that OCT is capable of carrying out high-content, longitudinal assays of 3D culture treatment response. We demonstrate the usage and capability of OCT for the dynamic monitoring ...

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    20. Correlation of localized glaucomatous visual field defects and spectral domain optical coherence tomography retinal nerve fiber layer thinning using a modified structure–function map for OCT

      Correlation of localized glaucomatous visual field defects and spectral domain optical coherence tomography retinal nerve fiber layer thinning using a modified structure–function map for OCT

      Purpose To study the correlation between glaucomatous visual field (VF) defects assessed by standard automated perimetry (SAP) and peripapillary retinal nerve fiber layer (RNFL) thinning measured by spectral domain optical coherence tomography (OCT) using a modified OCT-based peripapillary RNFL structure–function map. Patients and methods Perimetric glaucoma patients and age-matched normal control subjects were recruited from a university hospital clinic. All eyes underwent testing with the Spectralis spectral domain OCT and SAP on the same day. An OCT-based correspondence map, which correlated VF areas with peripapillary RNFL sectors was created to evaluate the relationship between glaucomatous RNFL thinning and VF ...

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    21. An Elastic Second Skin

      An Elastic Second Skin

      We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss ...

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    22. Advances of optical coherence tomography in myopia and pathologic myopia

      Advances of optical coherence tomography in myopia and pathologic myopia

      The natural course of high-axial myopia is variable and the development of pathologic myopia is not fully understood. Advancements in optical coherence tomography (OCT) technology have revealed peculiar intraocular structures in highly myopic eyes and unprecedented pathologies that cause visual impairment. New OCT findings include posterior precortical vitreous pocket and precursor stages of posterior vitreous detachment; peripapillary intrachoroidal cavitation; morphological patterns of scleral inner curvature and dome-shaped macula. Swept source OCT is capable of imaging deeper layers in the posterior pole for investigation of optic nerve pits, stretched and thinned lamina cribrosa, elongated dural attachment at posterior scleral canal, and ...

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    23. Optical coherence tomography angiography in paracentral acute middle maculopathy secondary to central retinal vein occlusion

      Optical coherence tomography angiography in paracentral acute middle maculopathy secondary to central retinal vein occlusion

      Purpose To report the clinical course and the optical coherence tomography angiography (OCTA) findings of patients presenting with paracentral acute middle maculopathy (PAMM) and central retinal vein occlusion (CRVO). Methods Retrospective case series. Clincal records and multimodal imaging findings of patients presenting with PAMM and CRVO were reviewed. Results Three eyes of three patients (2 males; mean age: 66 years) were included in the study. Mean follow-up was 9 months and images using OCTA (AngioVue OCT angiography system, Optovue, Inc., Fremont, CA, USA) were available at the last follow-up visit. During follow-up, best corrected visual acuity (BCVA) of case 1 ...

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    24. Quantifying the influence of Bessel beams on image quality in optical coherence tomography

      Quantifying the influence of Bessel beams on image quality in optical coherence tomography

      Light scattered by turbid tissue is known to degrade optical coherence tomography (OCT) image contrast progressively with depth. Bessel beams have been proposed as an alternative to Gaussian beams to image deeper into turbid tissue. However, studies of turbid tissue comparing the image quality for different beam types are lacking. We present such a study, using numerically simulated beams and experimental OCT images formed by Bessel or Gaussian beams illuminating phantoms with optical properties spanning a range typical of soft tissue. We demonstrate that, for a given scattering parameter, the higher the scattering anisotropy the lower the OCT contrast, regardless ...

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    1-24 of 262 1 2 3 4 ... 9 10 11 »
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