1. All Articles

    25-48 of 22710 « 1 2 3 4 5 ... 945 946 947 »
    1. Postdoctoral Research Fellowship in Biomedical Optics at CNRS/Strasbourg University

      Postdoctoral Research Fellowship in Biomedical Optics at CNRS/Strasbourg University

      Applicants are invited to apply for a postdoctoral researcher position in optical imaging systems for biomedical applications. The project involves the development of the novel catheter-based OCT imaging system to enhance the robotized interventional endoscope for diagnosing and treatment of diseases in the digestive system. The successful candidate will work with the research group supported by the ATIP-Avenir grant awarded by the French National Center for Scientific Research (CNRS) and the French National Institute of Health and Medical Research (INSERM). The group is focused on highly interdisciplinary projects that bridge photonics and robotics to improve performance of microscopic imaging modalities ...

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    2. Glaucoma Diagnostic Capabilities of Foveal Avascular Zone Parameters Using Optical Coherence Tomography Angiography According to Visual Field Defect Location

      Glaucoma Diagnostic Capabilities of Foveal Avascular Zone Parameters Using Optical Coherence Tomography Angiography According to Visual Field Defect Location

      Purpose: To assess the diagnostic ability of foveal avascular zone (FAZ) parameters to discriminate glaucomatous eyes with visual field defects (VFDs) in different locations (central vs. peripheral) from normal eyes. Patients and Methods: Totally, 125 participants were separated into three groups: normal (n=45), glaucoma with peripheral VFD (PVFD, n=45), and glaucoma with central VFD (CVFD, n=35). The FAZ area, perimeter, and circularity and parafoveal vessel density were calculated from optical coherence tomography angiography images. The diagnostic ability of the FAZ parameters and other structural parameters was determined according to glaucomatous VFD location. Associations between the FAZ parameters ...

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    3. OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN GEOGRAPHIC ATROPHY

      OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN GEOGRAPHIC ATROPHY

      Purpose: To analyze choriocapillaris (CC) vessel density (VD) around geographic atrophy (GA) secondary to non-neovascular dry age-related macular degeneration using optical coherence tomography angiography. Methods: We compared CC VD surrounding GA margin (500 [mu]m radius) with control CC (outside GA margin) in a consecutive series of GA patients presenting between August 2016 and February 2017 at the Medical Retina and Imaging Unit of University Vita-Salute, IRCCS Ospedale San Raffaele in Milan. Images were obtained through thresholding and binarization. We also compared the CC VD in a sample area of 500 [mu]m x 500 [mu]m surrounding GA margin ...

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    4. Effect of tissue frozen on quantitative optical properties using optical coherence tomography

      Effect of tissue frozen on quantitative optical properties using optical coherence tomography

      The purpose is to demonstrate the optical charactering concerning nasopharyngeal tissue of pig by fresh sections and frozen correlating sections with optical coherence tomography (OCT). After being imaged on a fresh specimen, samples are then stored in low temperature refrigerators ( − 80 ° C −80°C ) for one year for the second OCT measurement. The OCT structure of the epithelium, lamina propria, and the basement membrane are still resolvable; the median scattering coefficients and anisotropy factors fitting from OCT images based on the multiple scattering effects for epithelium are 27.6    mm − 1 27.6  mm−1 [interquartile range (IQR) 23.6 ...

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    5. NASA Technical Reports Server (NTRS) - Integration of Optical Coherence Tomography Scan Patterns to Augment Clinical Data Suite

      NASA Technical Reports Server (NTRS) - Integration of Optical Coherence Tomography Scan Patterns to Augment Clinical Data Suite

      Vision changes identified in long duration spaceflight astronauts has led Space Medicine at NASA to adopt a more comprehensive clinical monitoring protocol. Optical Coherence Tomography (OCT) was recently implemented at NASA, including on board the International Space Station in 2013. NASA is collaborating with Heidelberg Engineering to increase the fidelity of the current OCT data set by integrating the traditional circumpapillary OCT image with radial and horizontal block images at the optic nerve head. The retinal nerve fiber layer was segmented by two experienced individuals. Intra-rater (N=4 subjects and 70 images) and inter-rater (N=4 subjects and 221 images ...

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    6. Radial artery neointimal hyperplasia after transradial PCI—Serial optical coherence tomography volumetric study

      Radial artery neointimal hyperplasia after transradial PCI—Serial optical coherence tomography volumetric study

      Aims Transradial catheterization (TRC) is a dominant access site for coronary catheterization and percutaneous coronary interventions (PCI) in many centers. Previous studies reported higher intimal thickness of the radial artery (RA) wall in patients with a previous history of TRC. In this investigation the aim was to assess the intimal changes of RA using the optical coherence tomography (OCT) intravascular imaging in a serial manner. Methods and results 100 patients with the diagnosis of non-ST-elevation myocardial infarction (nSTEMI) treated by PCI were enrolled (6 patients were excluded from this analysis because of occluded RA at follow-up [2 patients] and insufficient ...

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    7. Frequency-constrained robust principal component analysis: a sparse representation approach to segmentation of dynamic features in optical coherence tomography imaging

      Frequency-constrained robust principal component analysis: a sparse representation approach to segmentation of dynamic features in optical coherence tomography imaging

      Sparse representation theory is an exciting area of research with recent applications in medical imaging and detection, segmentation, and quantitative analysis of biological processes. We present a variant on the robust-principal component analysis (RPCA) algorithm, called frequency constrained RPCA (FC-RPCA), for selectively segmenting dynamic phenomena that exhibit spectra within a user-defined range of frequencies. The algorithm lacks subjective parameter tuning and demonstrates robust segmentation in datasets containing multiple motion sources and high amplitude noise. When tested on 17 ex-vivo , time lapse optical coherence tomography (OCT) B-scans of human ciliated epithelium, segmentation accuracies ranged between 91–99% and consistently out-performed traditional ...

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    8. Measurement of Optic Disc Cup Surface Depth Using Cirrus HD-OCT

      Measurement of Optic Disc Cup Surface Depth Using Cirrus HD-OCT

      Purpose: To introduce the measurement method of optic disc cup surface depth using spectral-domain optical coherence tomography (SD-OCT) and then evaluate the rates of cup surface depression at three different stages of glaucoma. Methods: We retrospectively identified 52 eyes with preperimetric glaucoma, 56 with mild-or-moderate glaucoma and 50 with severe glaucoma and followed them for at least 48 months. Eyes were imaged using SD-OCT (Cirrus(TM) HD-OCT) at 12-month intervals. The mean cup surface depth was calculated using the following formula: Cup volume/(Disc area x Average cup-to-disc ratio2) - 200 [mu]m. Results: The rates of mean cup surface depression ...

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    9. Ocular coherence tomography image data of the retinal laminar structure in a mouse model of oxygen-induced retinopathy

      Ocular coherence tomography image data of the retinal laminar structure in a mouse model of oxygen-induced retinopathy

      The data presented in this article are related to the research paper entitled “Norrin treatment improves ganglion cell survival in an oxygen-induced model of retinal ischemia” (Dailey et al., 2017) [1] This article describes treatment with the human Norrin protein, an atypical Wnt-protein, to improve the survival of retinal ganglion cells in a murine model of Oxygen-Induced Retinopathy (OIR). That study utilized Optical coherence tomography (OCT) to visualize retinal layers at high resolution in vivo , and to quantify changes to nerve fiber layer thickness. Organization of the laminar structure of other retinal layers in this model in vivo , were not ...

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    10. Improving lateral resolution and image quality of optical coherence tomography by the multi-frame superresolution technique for 3D tissue imaging

      Improving lateral resolution and image quality of optical coherence tomography by the multi-frame superresolution technique for 3D tissue imaging

      The multi-frame superresolution technique is introduced to significantly improve the lateral resolution and image quality of spectral domain optical coherence tomography (SD-OCT). Using several sets of low resolution C-scan 3D images with lateral sub-spot-spacing shifts on different sets, the multi-frame superresolution processing of these sets at each depth layer reconstructs a higher resolution and quality lateral image. Layer by layer processing yields an overall high lateral resolution and quality 3D image. In theory, the superresolution processing including deconvolution can solve the diffraction limit, lateral scan density and background noise problems together. In experiment, the improved lateral resolution by ~3 times ...

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    11. Swept-source optical coherence tomography angiography in serpiginous choroiditis

      Swept-source optical coherence tomography angiography in serpiginous choroiditis

      ackground/Aims To analyse choroidal vascular density of affected and non-affected areas in active and inactive serpiginouschoroiditis (SC) by means of optical coherence tomography angiography (OCT-A). Methods In this cross-sectional and observational study, 22 eyes of 11 patients diagnosed with SC were included. All patients underwent blue-light fundus autofluorescence (spectralis Heidelberg retinalangiography+OCT) and swept-source OCT-A (AngioPlex Elite 9000 SS-OCT, Carl Zeiss Meditech) to analyse qualitative features and choroidal vessel density of areas considered affected, and the inner and the outer border of the lesions. Unaffected areas of otherwise healthy retina have also been studied. Results All inactive inflammatory lesions ...

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    12. Swept-source optical coherence tomographic findings in eyes with metastatic choroidal tumor

      Swept-source optical coherence tomographic findings in eyes with metastatic choroidal tumor

      Purpose To report the swept-source optical coherence tomographic (OCT) findings in two eyes with choroidal metastases. Observations Two patients with choroidal metastasis were studied. The metastasis was from a breast cancer in Case 1 and from a lung cancer in Case 2. In Case 1, swept-source OCT showed a highly reflective solid tumor with low optical reflective tissues that had replaced the choroidal tissue. Swept-source OCT was able to image the choroidal mass where other fundus imaging methods such as fluorescein angiography did not show the mass. Ophthalmoscopy of Case 2 showed hemorrhages in the inner retina, on the tumor ...

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    13. Macular capillary plexuses after macular hole surgery: an optical coherence tomography angiography study

      Macular capillary plexuses after macular hole surgery: an optical coherence tomography angiography study

      Aims To investigate the structural changes of the superficial capillary plexuses (SCP) and deep capillary plexuses (DCP) using optical coherence tomography (OCT) angiography (OCTA) in patients with idiopathic macular hole (MH) after surgery, determine the factors related to changes of macular capillary plexuses and evaluate its association with postoperative visual outcomes. Methods Thirty-three patients with unilateral MH who were followed for ≥6 months after surgery were included. Ophthalmologic evaluations included best corrected visual acuity (BCVA) and spectral-domain OCT before surgery and 6 months postsurgery. En face OCTA images were obtained for both eyes at 6 months postsurgery, and the postoperative ...

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    14. Pearls and pitfalls of optical coherence tomography angiography in the multimodal evaluation of uveitis

      Pearls and pitfalls of optical coherence tomography angiography in the multimodal evaluation of uveitis

      Background Optical coherence tomography angiography (OCTA) employs a novel imaging algorithm that detects the amplitude or phase decorrelation of blood cell movement. It thus provides a flow map with depth-resolved visualization of the various vascular layers in the posterior pole of the eye including the retina capillary plexus and the choroid. In the past 3 years, the number of research papers on the subject of OCTA in retinal diseases has grown exponentially including important applications in the field of uveitis. While the study of OCTA in uveitic diseases has gained remarkable relevance worldwide, interpretation can be challenging, and many limitations ...

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      Mentions: UCLA Vishali Gupta
    15. En-Face Optical Coherence Tomography of Acute Syphilitic Posterior Placoid Chorioretinopathy

      En-Face Optical Coherence Tomography of Acute Syphilitic Posterior Placoid Chorioretinopathy

      Purpose : To report a unique case series of acute syphilitic posterior placoid chorioretinopathy (ASPPC) correlating en-face optical coherence tomography (OCT) with standard imaging modalities. Methods : In this retrospective case series, multimodal imaging was performed in three ASPPC patients at the time of disease presentation. Results : Clinical and laboratory findings were consistent with the diagnosis of ASPPC. In all the study patients, multiple hyperreflective dot-like lesions distributed in the macular area and observed with en-face OCT at the level of retinal pigment epithelium (RPE) corresponded to the nodular RPE elevations on cross-sectional OCT and to the hyperautofluorescent spots on fundus autofluorescence ...

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    16. Phase and amplitude correction in polygon tunable laser-based optical coherence tomography

      Phase and amplitude correction in polygon tunable laser-based optical coherence tomography

      Phase instability is a serious problem in swept-source optical coherence tomography (OCT) with polygon tunable lasers; however, these devices have additional issues. We found that polygon tunable lasers also have fluctuations in output power and sweep range: the former creates artifacts that may impair the recognition of sample information, and the latter reduces the interference signal utilization during phase correction. We demonstrate a method that uses the calibration signal to quantify these problems and improve system stability and image quality. The proposed amplitude correction and phase correction methods are used to eliminate vertical artifacts and improve the resolution of OCT ...

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    17. Projection-resolved optical coherence tomography angiography exhibiting early flow prior to clinically observed retinal angiomatous proliferation

      Projection-resolved optical coherence tomography angiography exhibiting early flow prior to clinically observed retinal angiomatous proliferation

      Purpose The purpose of this study is to analyze early retinal angiomatous proliferation (RAP) utilizing a novel imaging modality, Projection-Resolved Optical Coherence Tomography Angiography (PR-OCTA). Observations Five months prior to the diagnosis of a RAP lesion, cross-sectional PR-OCTA demonstrated flow in the outer retina contiguous with the deep retinal capillary plexus (DCP) and adjacent to a small pigment epithelial detachment. After development of a clinically visible RAP lesion, cross-sectional PR-OCTA demonstrated the RAP lesion connecting DCP and sub-retinal pigment epithelial neovascularization. Conclusions & Importance This is the first report of PR-OCTA demonstrating abnormal flow in the outer retina prior to the ...

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    18. Utility of optical coherence tomography angiography in detecting glaucomatous damage in a uveitic patient with disc congestion: A case report

      Utility of optical coherence tomography angiography in detecting glaucomatous damage in a uveitic patient with disc congestion: A case report

      Purpose To report a case of uveitic glaucoma with congested optic disc where optical coherence tomography angiography (OCT-A) provided diagnostic utility in assessing glaucomatous damage but optical coherence tomography (OCT) alone had limited utility. Observations We report a case of a 33-year-old Caucasian female referred to the USC Roski Eye Institute for uncontrolled intraocular pressure (IOP) in the left eye. She was managed by an outside provider for 6 months, where her IOP ranged from 28 to 42 mm Hg in the left eye on maximally tolerated medical therapy. Her clinical exam was consistent with Herpes family trabeculitis, optic nerve ...

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    19. Accuracy of a New Swept-Source Optical Coherence Tomography Biometer for IOL Power Calculation and Comparison to IOLMaster

      Accuracy of a New Swept-Source Optical Coherence Tomography Biometer for IOL Power Calculation and Comparison to IOLMaster

      PURPOSE: To investigate the accuracy of the measurements provided by a new optical biometer (OA-2000, Tomey Corporation, Nagoya, Japan) for calculating the intraocular lens (IOL) power and to compare the refractive outcomes to those obtained with the IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany). METHODS: In this interventional multicenter study, consecutive patients having cataract surgery were enrolled. Only the IOL model used in the largest sample of patients was selected and the eyes implanted with that IOL were subsequently analyzed. The OA-2000, an optical biometer based on swept-source optical coherence tomography (SS-OCT), was used to measure axial length and corneal ...

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    20. Parallel optical coherence tomography apparatuses, systems, and related methods

      Parallel optical coherence tomography apparatuses, systems, and related methods

      Abstract Provided is a snapshot spectral domain optical coherence tomographer comprising a light source providing a plurality of beamlets; a beam splitter, splitting the plurality of beamlets into a reference arm and a sample arm; a first optical system that projects the sample arm onto multiple locations of a sample; a second optical system for collection of a plurality of reflected sample beamlets; a third optical system projecting the reference arm to a reflecting surface and receiving a plurality of reflected reference beamlets; a parallel interferometer that provides a plurality of interferograms from each of the plurality of sample beamlets ...

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    21. Systems, methods and apparatuses for real-time anastomosis guidance and surgical evaluation using optical coherence tomography

      Systems, methods and apparatuses for real-time anastomosis guidance and surgical evaluation using optical coherence tomography

      A surgical evaluation and guidance system for use in extravacular evaluation and guidance of fluid vessel surgeries, includes an optical coherence tomography engine; a vessel probe optically coupled to the optical coherence tomography engine; and a signal processing and display system adapted to communicate with the optical coherence tomography engine to receive imaging signals therefrom. An optical coherence tomography vessel probe for use in extravacular evaluation and guidance of fluid vessel surgeries, includes a probe body having a proximal end and a distal end; an optical relay system disposed within the probe body; and a vessel adapter at least one ...

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    22. Swept source OCT system and method with phase-locked detection

      Swept source OCT system and method with phase-locked detection

      A swept source OCT system and related method are disclosed. The system comprises a control device for operating a tunable light source in response to an electronic sweep control signal such that the tunable light source carries out wave length sweeps with a repetition rate f.sub.sweep, which depends on the frequency of the sweep control signal. The system further comprises a detection device for the time-resolved detection of an interference signal from a sample beam and a reference beam with the help of a detection cycle signal. The sweep control signal and the detection cycle signal are phase-locked ...

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    23. Measurement device for a laser processing system and a method for performing position measurements by means of a measurement beam on a workpiece

      Measurement device for a laser processing system and a method for performing position measurements by means of a measurement beam on a workpiece

      The invention relates to a measurement device for a laser processing system, for carrying out position measurements by means of a measurement beam on a workpiece, which is intended for processing by means of a high energy processing beam, which can be moved relative to the workpiece along a predetermined main processing path. The measurement device can be coupled to a processing device and includes an optical coherence tomograph. The measurement device is equipped to shift the measurement beam on the workpiece in the direction of the main processing path in at least one first measurement position and one second ...

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