1. All Articles

    25-48 of 21169 « 1 2 3 4 5 ... 880 881 882 »
    1. Dependence on fiber Fabry-Pérot tunable filter characteristics in an all-fiber swept-wavelength laser for use in an optical coherence tomography system

      Dependence on fiber Fabry-Pérot tunable filter characteristics in an all-fiber swept-wavelength laser for use in an optical coherence tomography system

      Optical coherence tomography (OCT) has become a useful and common diagnostic tool within the field of ophthalmology. Although presently a commercial technology, research continues in improving image quality and applying the imaging method to other tissue types. Swept-wavelength lasers based upon fiber ring cavities containing fiber Fabry-P´erot tunable filters (FFP-TF), as an intracavity element, provide swept-source optical coherence tomography (SS-OCT) systems with a robust and scalable platform. The FFP-TF can be fabricated within a large range of operating wavelengths, free spectral ranges (FSR), and finesses. To date, FFP-TFs have been fabricated at operating wavelengths from 400 nm to 2 ...

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      Mentions: Micron Optics
    2. Scattering angle resolved optical coherence tomography for in vivo murine retinal imaging

      Scattering angle resolved optical coherence tomography for in vivo murine retinal imaging

      Optical coherence tomography (OCT) retinal imaging contributes to understanding central nervous system (CNS) diseases because the eye is an anatomical “window to the brain” with direct optical access to nonmylenated retinal ganglion cells. However, many CNS diseases are associated with neuronal changes beyond the resolution of standard OCT retinal imaging systems. Though studies have shown the utility of scattering angle resolved (SAR) OCT for particle sizing and detecting disease states ex vivo, a compact SAR-OCT system for in vivo rodent retinal imaging has not previously been reported. We report a fiber-based SAR-OCT system (swept source at 1310 nm ± 65 nm ...

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    3. Choroidal Blood Flow Visualization In High Myopia Using A Projection Artifact Method In Optical Coherence Tomography Angiography

      Choroidal Blood Flow Visualization In High Myopia Using A Projection Artifact Method In Optical Coherence Tomography Angiography

      Purpose: To visualize choroidal blood flow in larger vessels in highly myopic eyes using a phenomenon of the projection artifact to in the sclera using optical coherence tomography angiography. Methods: The retrospective study included 92 eyes (54 patients) with greater than 8 diopters of myopia. All eyes were examined using optical coherence tomography angiography (RTVue XR Avanti; Optovue Inc, Fremont, CA). The blood flow in choroidal vessels was evaluated by attempting to directly segment the choroid and also by placing the segmentation layer behind the choroid, within the sclera. Subfoveal choroidal thickness was also measured at the same time. The ...

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    4. En Face OCT Analysis to Assess the Spectrum of Perivenular Ischemia and Paracentral Acute Middle Maculopathy in Retinal Vein Occlusion

      En Face OCT Analysis to Assess the Spectrum of Perivenular Ischemia and Paracentral Acute Middle Maculopathy in Retinal Vein Occlusion

      Purpose To assess the spectrum of perivenular ischemia in eyes with retinal vascular obstruction (typically central or hemicentral retinal vein obstruction) using en face optical coherence tomography (OCT). Design Retrospective observational case series. Methods Eyes with recent retinal vascular occlusion illustrating paracentral acute middle maculopathy (PAMM) in a perivenular fern-like pattern with en face OCT were evaluated in this study. Multimodal retinal imaging including en face OCT segmentation of the inner nuclear layer was performed in all patients. Color fundus photography and fluorescein angiography (FA) images were used to create a vascular overlay of the retinal veins versus the retinal ...

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    5. Evaluation of Optical Coherence Tomography to Detect Elevated Intracranial Pressure in Children

      Evaluation of Optical Coherence Tomography to Detect Elevated Intracranial Pressure in Children

      Importance Detecting elevated intracranial pressure in children with subacute conditions, such as craniosynostosis or tumor, may enable timely intervention and prevent neurocognitive impairment, but conventional techniques are invasive and often equivocal. Elevated intracranial pressure leads to structural changes in the peripapillary retina. Spectral-domain (SD) optical coherence tomography (OCT) can noninvasively quantify retinal layers to a micron-level resolution. Objective To evaluate whether retinal measurements from OCT can serve as an effective surrogate for invasive intracranial pressure measurement. Design, Setting, and Participants This cross-sectional study included patients undergoing procedures at the Children’s Hospital of Philadelphia from September 2014 to June 2015 ...

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    6. Use of optical coherence topography for objective assessment of fundus torsion

      Use of optical coherence topography for objective assessment of fundus torsion

      Objective assessment of fundus torsion is currently performed with indirect ophthalmoscopy or fundus photography. Using the infrared image of the macular scan of the optical coherence tomography one can assess the presence and amount of fundus torsion. In addition, the line scan through the fovea can be used as a reference to confirm the position of the foveal pit in relation to the optic nerve head. Two cases are used to demonstrate how to assess fundus torsion with the use of the optical coherence tomography.

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    7. Regarding optical coherence tomography grading of ischemia in central retinal venous occlusion

      Regarding optical coherence tomography grading of ischemia in central retinal venous occlusion

      The author read with interest the article by Browning et al. 1 The author humbly wants to discuss a few facts. 1. The article 1 discusses grading of retinal ischemia based on optical coherence tomography features in central retinal venous occlusion. As coexisting central retinal arterial occlusion or cilioretinal arterial occlusion may also cause inner retinal hyper-reflectivity, exclusion of such cases is an important consideration before implicating central retinal venous occlusion for the ischemia. Extensive intraretinal hemorrhages are other important hindrances to the evaluation of the perfusion status of the retina using both fluorescein angiogram and optical coherence tomography. 2 ...

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    8. Lateral resolution improvement of oversampled OCT images using Capon estimation of weighted subvolume contribution

      Lateral resolution improvement of oversampled OCT images using Capon estimation of weighted subvolume contribution

      A novel technique for lateral resolution improvement in optical coherence tomography (OCT) is presented. The proposed method is based on lateral oversampling of the image. The locations and weights of multiple high spatial resolution sub-volumes are calculated using a Capon estimator assuming each contributes a weighted portion to the detected signal. This technique is independent of the delivery optics and the depth of field. Experimental results demonstrate that it is possible to achieve ~4x lateral resolution improvement which can be diagnostically valuable, especially in cases where the delivery optics are constrained to low numerical aperture (NA).

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    9. Ultrahigh-resolution OCT imaging of the human cornea

      Ultrahigh-resolution OCT imaging of the human cornea

      We present imaging of corneal pathologies using optical coherence tomography (OCT) with high resolution. To this end, an ultrahigh-resolution spectral domain OCT (UHR-OCT) system based on a broad bandwidth Ti:sapphire laser is employed. With a central wavelength of 800 nm, the imaging device allows to acquire OCT data at the central, paracentral and peripheral cornea as well as the limbal region with 1.2 µm x 20 µm (axial x lateral) resolution at a rate of 140 000 A-scans/s. Structures of the anterior segment of the eye, not accessible with commercial OCT systems, are visualized. These include corneal ...

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    10. Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas

      Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas

      Corneal degenerative conditions such as keratoconus (KC) cause progressive damage to the anterior corneal tissue and eventually severely compromise visual acuity. The ability to visualize corneal tissue damage in-vivo at cellular or sub-cellular level at different stages of development of KC and other corneal diseases, can aid the early diagnostics as well as the development of more effective treatment approaches for various corneal pathologies, including keratoconus. Here, we present the optical design of an optical coherence tomography system that can achieve 0.95 µm axial resolution in biological tissue and provide test results for the system’s spatial resolution and ...

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    11. Structural and functional human retinal imaging with a fiber-based visible light OCT ophthalmoscope

      Structural and functional human retinal imaging with a fiber-based visible light OCT ophthalmoscope

      The design of a multi-functional fiber-based Optical Coherence Tomography (OCT) system for human retinal imaging with < 2 micron axial resolution in tissue is described. A detailed noise characterization of two supercontinuum light sources with different pulse repetition rates is presented. The higher repetition rate and lower noise source is found to enable a sensitivity of 96 dB with 0.15 mW light power at the cornea and a 98 microsecond exposure time. Using a broadband (560 ± 50 nm), 90/10, fused single-mode fiber coupler designed for visible wavelengths, the sample arm is integrated into an ophthalmoscope platform, similar to current ...

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    12. Correlation of the derivative as a robust estimator of scatterer size in optical coherence tomography (OCT)

      Correlation of the derivative as a robust estimator of scatterer size in optical coherence tomography (OCT)

      The size-dependent spectral variations, predicted by Mie theory, have already been considered as a contrast enhancement mechanism in optical coherence tomography. In this work, a new spectroscopic metric, the bandwidth of the correlation of the derivative, was developed for estimating scatterer size which is more robust and accurate compared to existing methods. Its feasibility was demonstrated using phantoms containing polystyrene microspheres as well as images of normal and cancerous human colon. The results are very promising, suggesting that the proposed metric could be utilized for measuring nuclear size distribution, a diagnostically valuable marker, in human tissues.

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    13. Retinal oximetry in humans using visible-light optical coherence tomography [Invited]

      Retinal oximetry in humans using visible-light optical coherence tomography [Invited]

      We measured hemoglobin oxygen saturation (sO 2 ) in the retinal circulation in healthy humans using visible-light optical coherence tomography (vis-OCT). The measurements showed clear oxygenation differences between central retinal arteries and veins close to the optic nerve head. Spatial variations at different vascular branching levels were also revealed. In addition, we presented theoretical and experimental results to establish that noises in OCT intensity followed Rice distribution. We used this knowledge to retrieve unbiased estimation of true OCT intensity to improve the accuracy of vis-OCT oximetry, which had inherently lower signal-to-nose ratio from human eyes due to safety and comfort limitations ...

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    14. Heart structural remodeling in a mouse model of Duchenne cardiomyopathy revealed using optical polarization tractography [Invited]

      Heart structural remodeling in a mouse model of Duchenne cardiomyopathy revealed using optical polarization tractography [Invited]

      We investigated the heart structural remodeling in the mdx4cv mouse model of Duchenne cardiomyopathy using optical polarization tractography. Whole heart tractography was obtained in freshly dissected hearts from six mdx4cv mice. Six hearts from C57BL/6J mice were also imaged as the normal control. The mdx4cv hearts were significantly larger than the control hearts and had significantly higher between–subject variations in myofiber organization. While both strains showed classic cross-helical fiber organization in the left ventricle, the rate of the myocardial fiber orientation change across the heart wall was significantly altered in the right ventricle of the mdx4cv heart.

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    15. OCT intensity and phase fluctuations correlated with activity-dependent neuronal calcium dynamics in the Drosophila CNS [Invited]

      OCT intensity and phase fluctuations correlated with activity-dependent neuronal calcium dynamics in the Drosophila CNS [Invited]

      Phase-resolved OCT and fluorescence microscopy were used simultaneously to examine stereotypic patterns of neural activity in the isolated Drosophila central nervous system. Both imaging modalities were focused on individually identified bursicon neurons known to be involved in a fixed action pattern initiated by ecdysis-triggering hormone. We observed clear correspondence of OCT intensity, phase fluctuations, and activity-dependent calcium-induced fluorescence.

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    16. Review of intraoperative optical coherence tomography: technology and applications [Invited]

      Review of intraoperative optical coherence tomography: technology and applications [Invited]

      During microsurgery, en face imaging of the surgical field through the operating microscope limits the surgeon’s depth perception and visualization of instruments and sub-surface anatomy. Surgical procedures outside microsurgery, such as breast tumor resections, may also benefit from visualization of the sub-surface tissue structures. The widespread clinical adoption of optical coherence tomography (OCT) in ophthalmology and its growing prominence in other fields, such as cancer imaging, has motivated the development of intraoperative OCT for real-time tomographic visualization of surgical interventions. This article reviews key technological developments in intraoperative OCT and their applications in human surgery. We focus on handheld ...

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    17. The ecosystem that powered the translation of OCT from fundamental research to clinical and commercial impact [Invited]

      The ecosystem that powered the translation of OCT from fundamental research to clinical and commercial impact [Invited]

      25 years is a relatively short period of time for a medical technology to become a standard of care impacting the treatment of millions of people every year. Yet 25 years ago there were no OCT companies, no OCT products, no OCT markets, and only one journal article published using the term OCT (optical coherence tomography). OCT has had a tremendous scientific, clinical, and economic impact on society. Today, it is estimated that there are ~30 Million OCT imaging procedures performed worldwide every year and the OCT system market is approaching $1B per year. OCT has helped diagnose patients with ...

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    18. In vivo monitoring laser tissue interaction using high resolution Fourier-domain optical coherence tomography

      In vivo monitoring laser tissue interaction using high resolution Fourier-domain optical coherence tomography

      Laser-induced therapies include laser ablation to remove or cut target tissue by irradiating high-power focused laser beam. These laser treatments are widely used tools for minimally invasive surgery and retinal surgical procedures in clinical settings. In this study, we demonstrate laser tissue interaction images of various sample tissues using high resolution Fourier-domain optical coherence tomography (Fd-OCT). We use a Q-switch diode-pumped Nd:YVO4 nanosecond laser (532nm central wavelength) with a 4W maximum output power at a 20 kHz repetition rate to ablate in vitro and in vivo samples including chicken breast and mouse ear tissues. The Fd-OCT system acquires time-series ...

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      Mentions: Dae Yu Kim
    19. Extracting relevant information for cancer diagnosis from dynamic full field OCT through image processing and learning

      Extracting relevant information for cancer diagnosis from dynamic full field OCT through image processing and learning

      For a large number of cancer surgeries, the lack of reliable intraoperative diagnosis leads to reoperations or bad outcomes for the patients. To deliver better diagnosis, we developed Dynamic Full Field OCT (D-FFOCT) as a complement to FFOCT. FFOCT already presents interesting results for cancer diagnosis e.g. Mohs surgery and reaching 96% accuracy on prostate cancer. D-FFOCT accesses the dynamic processes of metabolism and gives new tools to diagnose the state of a tissue at the cellular level to complement FFOCT contrast. We developed a processing framework that intends to maximize the information provided by the FFOCT technology as ...

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    20. RETINAL LAYER SEGMENTATION AFTER SILICONE OIL OR GAS TAMPONADE FOR MACULA-ON RETINAL DETACHMENT USING OPTICAL COHERENCE TOMOGRAPHY

      RETINAL LAYER SEGMENTATION AFTER SILICONE OIL OR GAS TAMPONADE FOR MACULA-ON RETINAL DETACHMENT USING OPTICAL COHERENCE TOMOGRAPHY

      Purpose: To evaluate and compare the effect of silicone oil and gas on the thickness of all retinal layers in eyes with macula-on retinal detachment (RD). Methods: Three hundred and sixty-seven eyes of 367 patients who received silicone oil tamponade and 310 eyes of 310 patients who received gas tamponade for the treatment of rhegmatogenous RD were initially reviewed. Automated retinal segmentation method using Spectralis optical coherence tomography was used for analysis. The primary outcome measure was the change in thickness of each retinal layer in the central 1 mm zone (silicone oil vs. gas tamponade). The secondary outcome measure ...

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    21. Retinal imaging with adaptive optics full-field OCT

      Retinal imaging with adaptive optics full-field OCT

      Adaptive optics full-filed OCT (FFOCT) with a transmissive liquid crystal spatial light modulator (LCSLM) as wavefront corrector is used without strict plane conjugation for low order aberrations corrections. We validated experimentally that FFOCT resolution is independent of aberrations and only reduce the signal level. A signal based sensorless algorithm was thus applied for wavefront distortion compensation. Image quality improvements by the wavefront sensorless control of the LCSLM were evaluated on in vitro samples. By replacing the FFOCT sample arm objective with an artificial eye used to train ophthalmologists, adaptive optics retinal imaging was achieved. In vivo experiments using a liquid ...

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    22. Utility of optical coherence tomography in a case of bilateral congenital macular coloboma

      Utility of optical coherence tomography in a case of bilateral congenital macular coloboma

      Macular coloboma is a congenital defect of the retina and choroid in the macular region. It may appear due to an intrauterine inflammation or a developmental abnormality. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a result of malformation of the renal tubule. Its combination with ocular manifestations may be genetic, specifically in case of claudin‑19 (CLDN‑19) gene mutations. The combination of FHHNC and ocular manifestations is not always present in these patients. Optical coherence tomography (OCT) helps us diagnose this condition by allowing us to evaluate and confirm the absence of retina layers without histological examination. Although ...

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    23. Image-guided feedback for ophthalmic microsurgery using multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

      Image-guided feedback for ophthalmic microsurgery using multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

      Surgical interventions for ocular diseases involve manipulations of semi-transparent structures in the eye, but limited visualization of these tissue layers remains a critical barrier to developing novel surgical techniques and improving clinical outcomes. We addressed limitations in image-guided ophthalmic microsurgery by using microscope-integrated multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (iSS-SESLO-OCT). We previously demonstrated in vivo human ophthalmic imaging using SS-SESLO-OCT, which enabled simultaneous acquisition of en face SESLO images with every OCT cross-section. Here, we integrated our new 400 kHz iSS-SESLO-OCT, which used a buffered Axsun 1060 nm swept-source, with a surgical microscope and ...

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    25-48 of 21169 « 1 2 3 4 5 ... 880 881 882 »
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