1. 1-24 of 501 1 2 3 4 ... 19 20 21 »
    1. Grading severity in retinitis pigmentosa using clinical assessment, visual acuity, perimetry and optical coherence tomography

      Grading severity in retinitis pigmentosa using clinical assessment, visual acuity, perimetry and optical coherence tomography

      To develop a grading system for retinitis pigmentosa (RP), providing clinicians with a simple, objective measure of disease severity. An observational case series of 14 patients with RP. Disease severity was assessed using four criteria; clinical appearance, visual acuity (best corrected LogMAR, BCVA), perimetry (mean deviation, MD) and Fourier-domain optical coherence tomography (outer retinal thickness, ORT at the fovea). Each criterion was scored on a severity scale from 0 (mild disease) to 4 (severe disease), giving an overall score out of 16. The mean BCVA was 0.37 LogMAR (range 0.02 to PL), mean MD was -25.35 dB ...

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    2. All-fiber spectral-domain optical coherence tomography with high resolution by using a PCF-based broadband coupler and a k-domain linearization method

      All-fiber spectral-domain optical coherence tomography with high resolution by using a PCF-based broadband coupler and a k-domain linearization method

      We demonstrate spectral-domain optical coherence tomography (SD-OCT) with high axial resolution and high image acquisition speed, which is realized by using a broadband coupler based on a photonic crystal fiber (PCF). The PCF-based coupler with broad bandwidth was fabricated by using a fused biconical tapered (FBT) method, and the axial resolution of the SD-OCT was improved to be 2 µm. The image acquisition speed of the SD-OCT was estimated to be 500 Hz. A k-domain linearization method was exploited to compensate for the mismatched spectral information between the wave-number and the pixel position at the CCD, which was induced by ...

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    3. Optical Coherence Tomography for Brain Imaging

      Optical Coherence Tomography for Brain Imaging

      Recently, there has been growing interest in using OCT for brain imaging. A feasibility study of OCT for guiding deep brain probes has found that OCT can differentiate the white matter and gray matter because the white matter tends to have a higher peak reflectivity and steeper attenuation rate compared to gray matter. In vivo 3D visualization of the layered organization of a rat olfactory bulb with OCT has been demonstrated. OCT has been used for single myelin fiber imaging in living rodents without labeling. The refractive index in the rat somatosensory cortex has also been measured with OCT. In ...

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    4. Influence of scanning density on macular choroidal volume measurement using spectral-domain optical coherence tomography

      Influence of scanning density on macular choroidal volume measurement using spectral-domain optical coherence tomography

      Background To evaluate the impact of scanning density on macular choroidal volume measurement using spectral-domain optical coherence tomography (SD-OCT). Methods Thirty eyes of normal subjects underwent consecutive raster choroidal scanning protocols using SD-OCT in enhanced-depth imaging mode. Manual choroidal segmentation was performed using the built-in automated retinal segmentation software to obtain five analyses with different inter-scan distances, including inter-scan distances of 30 μm, 60 μm, 120 μm, 240 μm, and 480 μm. The built-in software of the device automatically generated the choroidal thickness and volume map in the similar manner as for the retinal volume map, using the standardized Early ...

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    5. Numerical study on spectral domain optical coherence tomography spectral calibration and re-sampling importance

      Numerical study on spectral domain optical coherence tomography spectral calibration and re-sampling importance

      Abstract  A spectral calibration technique, a data processing method and the importance of calibration and re-sampling methods for the spectral domain optical coherence tomography system were numerically studied, targeted to optical coherence tomography (OCT) signal processing implementation under graphics processing unit (GPU) architecture. Accurately, assigning the wavelength to each pixel of the detector is of paramount importance to obtain high quality images and increase signal to noise ratio (SNR). High quality imaging can be achieved by proper calibration methods, here performed by phase calibration and interpolation. SNR was assessed employing two approaches, single spectrum moving window averaging and consecutive spectra ...

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    6. Application of optical coherence tomography to detect Cucumber green mottle mosaic virus (CGMMV) infected cucumber seed

      Application of optical coherence tomography to detect Cucumber green mottle mosaic virus (CGMMV) infected cucumber seed

      Abstract  In this study, we distinguished Cucumber green mottle mosaic virus (CGMMV) infected seeds from healthy seeds using optical coherence tomography (OCT). Two dimensional OCT images and stereo micrographs revealed that the infected seeds had narrow gap between the seed coat and endosperm that were not present in the healthy seeds. Three dimensional OCT images confirmed that the narrow gaps were present in the inner structure of overall the infected seeds. A-scan analysis was also performed to calculate the distance from the seed coat to the endosperm. The results revealed a difference in the width of the gap of about ...

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    7. Polymeric nanoparticles as OCT contrast agents

      Polymeric nanoparticles as OCT contrast agents

      In this study, the optical properties of two nano-sized polymer colloids in optical coherence tomography (OCT) were compared in vitro with respect to their potential use as contrast agents. We used two types of particles: compact hydrophobic spherical polystyrene (PS) particles and soft water-swollen nanogel (NG) particles both with grafted hydrophilic shell, both prepared at two different sizes (PS at 300 and 150 nm, NG at 300 and 200 nm). The OCT backscattering signals of the particles in a vessel-mimicking highly scattering agar/TiO 2 phantom were compared on either number of particles or weight percent. Larger particles and higher ...

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    8. In-vivo investigation of laser-induced choroidal neovascularization in rat using spectral-domain optical coherence tomography (SD-OCT)

      In-vivo investigation of laser-induced choroidal neovascularization in rat using spectral-domain optical coherence tomography (SD-OCT)

      Purpose This study investigated the in-vivo formation process of laser-induced choroidal neovascularization (CNV) in rat using high-resolution spectral-domain optical coherence tomography (SD-OCT), and compared the results to histological methods. Methods Brown Norway rats ( n = 60, 6–8 weeks of age) received 532-nm diode laser photocoagulation. SD-OCT and fluorescein angiography (FA) were performed in vivo 2, 5, 7, 14, and 21 days post-laser application. Haematoxylin and eosin (H&E) staining and immunohistochemistry for CD31, phosphorylated vascular endothelial factor receptor 2 (pVEGFR2) were conducted at each time point to observe the CNV in vitro. Choroidal flatmount preparations were observed using a confocal ...

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    9. Glaucoma diagnosis optic disc analysis comparing Cirrus spectral domain optical coherence tomography and Heidelberg retina tomograph II

      Glaucoma diagnosis optic disc analysis comparing Cirrus spectral domain optical coherence tomography and Heidelberg retina tomograph II

      Purpose To evaluate the diagnostic ability of optic nerve head parameters, measured by Cirrus spectral domain optical coherence tomography (SD OCT) and Heidelberg retina tomograph II (HRT II) to detect concomitant glaucoma. Methods Cirrus OCT and HRT examinations of 62 eyes of 62 patients (32 with no perimetric glaucoma and 30 with concomitant perimetric glaucoma) evaluated between August 2010 and December 2010 were retrospectively analyzed and compared with regard to the optic disc morphometric parameter, disc area, rim area, cup-to-disc ratio (CDR), and cup volume. Receiver operating characteristic curves were constructed for the parameters and areas under the curves (AUCs ...

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    10. In vivo comparison of arterial lumen dimensions assessed by co-registered three-dimensional (3D) quantitative coronary angiography, intravascular ultrasound and optical coherence tomography

      In vivo comparison of arterial lumen dimensions assessed by co-registered three-dimensional (3D) quantitative coronary angiography, intravascular ultrasound and optical coherence tomography

      This study sought to compare lumen dimensions as assessed by 3D quantitative coronary angiography (QCA) and by intravascular ultrasound (IVUS) or optical coherence tomography (OCT), and to assess the association of the discrepancy with vessel curvature. Coronary lumen dimensions often show discrepancies when assessed by X-ray angiography and by IVUS or OCT. One source of error concerns a possible mismatch in the selection of corresponding regions for the comparison. Therefore, we developed a novel, real-time co-registration approach to guarantee the point-to-point correspondence between the X-ray, IVUS and OCT images. A total of 74 patients with indication for cardiac catheterization were ...

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    11. Unrestricted utilization of frequency domain optical coherence tomography in coronary interventions

      Unrestricted utilization of frequency domain optical coherence tomography in coronary interventions

      Frequency domain optical coherence tomography (FD-OCT) has shown promise to evaluate coronary devices in clinical trials, however, little is known about its application in clinical practice. This prospective, single center initiative planned for 100 % FD-OCT utilization in all patients undergoing coronary interventions during a 60-day period. Operators pre-specified the planned intervention based on angiography alone. FD-OCT success was defined as acquisition of good quality images enabling adequate quantification of vessel dimensions and lesion/percutaneous coronary intervention (PCI) assessment. Impact on management occurred when angiography-based planning was altered based on FD-OCT data. There were 297 FD-OCT acquisitions performed in 155 vessels ...

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    12. Correlation between multifocal pattern electroretinography and Fourier-domain OCT in eyes with temporal hemianopia from chiasmal compression

      Correlation between multifocal pattern electroretinography and Fourier-domain OCT in eyes with temporal hemianopia from chiasmal compression

      Purpose To evaluate the correlation between multifocal pattern electroretinography (mfPERG) and Fourier-domain optical coherence tomography (FD-OCT) with regard to macular and retinal nerve fiber layer (RNFL) thickness in eyes with temporal hemianopia from chiasmal compression. Methods Twenty-five eyes from 25 patients with permanent temporal visual field defects from chiasmal compression and 25 healthy eyes were submitted to mfPERG using a stimulus pattern of 19 rectangles, standard automated perimetry and FD-OCT measurements. The mfPERG response was determined for groups of three rectangles for the nasal and temporal hemifields and for each quadrant. Macular thickness measurements were registered according to an overlaid ...

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    13. Assessment of Corneal Deformation Using Optical Coherence Tomography and Digital Volume Correlation

      Assessment of Corneal Deformation Using Optical Coherence Tomography and Digital Volume Correlation

      In order to study the mechanical behavior of the vertebrate eye cornea under intraocular pressure, digital volume correlation (DVC) has been carried out on a series of volume images generated through swept source optical coherence tomography (SSOCT). Phantom and porcine cornea samples under posterior inflation conditions were considered. The effect of noise and reconstruction uncertainties were evaluated through correlation of two repeated reconstructed volumes without loading. The strain resolutions of the DVC were obtained after calculating their mean and standard deviation values. Then, several reconstructed volumes were recorded one after the other, introducing a rigid body translation of 10 μm ...

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    14. Biomedical Optical Imaging Technologies Design and Applications (Book)

      Biomedical Optical Imaging Technologies Design and Applications (Book)

      Biomedical optics is a rapidly growing area of research that has passed the “tipping point” for technology transfer, with significant momentum toward commercialization. Designing an imaging technique to meet the specific application requirements is one of the keys in the development and commercialization of new imaging technologies. It requires a solid understanding of imaging technologies and special requirements for imaging applications; it also encompasses the selection of optical configurations, light sources, optical components, detectors, illumination and imaging system designs, and testing. This book will provide an introduction to principles, designs, and applications of a number of imaging technologies, including spectroscopy ...

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    15. Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure

      Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure

      Purpose To evaluate the inter- and intra-observer agreement of measurement of the iris–trabecular contact (ITC) index, a measure of the degree of angle closure, using swept source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan). Methods One randomly selected eye of 60 subjects was imaged under dark room conditions. The SSOCT 3-dimensional angle scan simultaneously obtains 128 radial scans of the anterior chamber for the entire circumference of the angle. Post-imaging analysis estimated the ITC index using in-built software. For intra-observer agreement for image grading, one examiner performed the grading twice in a masked fashion and random ...

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    16. Pathology Hinting as the Combination of Automatic Segmentation with a Statistical Shape Model

      Pathology Hinting as the Combination of Automatic Segmentation with a Statistical Shape Model

      With improvements in acquisition speed and quality, the amount of medical image data to be screened by clinicians is starting to become challenging in the daily clinical practice. To quickly visualize and find abnormalities in medical images, we propose a new method combining segmentation algorithms with statistical shape models. A statistical shape model built from a healthy population will have a close fit in healthy regions. The model will however not fit to morphological abnormalities often present in the areas of pathologies. Using the residual fitting error of the statistical shape model, pathologies can be visualized very quickly. This idea ...

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    17. Compensating Motion Artifacts of 3D in vivo SD-OCT Scans

      Compensating Motion Artifacts of 3D in vivo SD-OCT Scans

      We propose a probabilistic approach for compensating motion artifacts in 3D in vivo SD-OCT (spectral-domain optical coherence tomography) tomographs. Subject movement causing axial image shifting is a major problem for in vivo imaging. Our technique is applied to analyze the tissue at percutaneous implants recorded with SD-OCT in 3D. The key challenge is to distinguish between motion and the natural 3D spatial structure of the scanned subject. To achieve this, the motion estimation problem is formulated as a conditional random field (CRF). For efficient inference, the CRF is approximated by a Gaussian Markov random field. The method is verified on ...

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    18. Inter-observer agreement for spectral- and time-domain optical coherence tomography image grading: a prospective study

      Inter-observer agreement for spectral- and time-domain optical coherence tomography image grading: a prospective study

      Abstract  The purpose of this study was to compare inter-observer agreement of Stratus™ OCT versus Spectralis™ OCT image grading in patients with neovascular age-related macular degeneration (AMD). Thirty eyes with neovascular AMD were examined with Stratus™ OCT and Spectralis™ OCT. Four different scan protocols were used for imaging. Three observers graded the images for the presence of various pathologies. Inter-observer agreement between OCT models was assessed by calculating intra-class correlation coefficients (ICC). In Stratus™ OCT highest interobserver agreement was found for subretinal fluid (ICC: 0.79), and in Spectralis™ OCT for intraretinal cysts (IRC) (ICC: 0.93). Spectralis™ OCT showed ...

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    19. Quantitative optical coherence tomography of fluid-filled oral mucosal lesions

      Quantitative optical coherence tomography of fluid-filled oral mucosal lesions

      The decision of selecting the most representative site for the biopsy of fluid-filled lesions can be difficult. This may be attributed to the poor delineation of the correct lesional site by clinical observation alone. In this study, optical coherence tomography is used to quantify the contrast between solid- and fluid-filled lesions by measuring the light intensity change at the tissue–fluid interface (intensity drop). This parameter was measured from sequential axial scans (n ≈ 106 per sample) of 3D optical coherence tomography (OCT) datasets from control tissues (n = 14) and fluid-filled lesions (n = 7) and displayed as a 2D-scaled intensity drop ...

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    20. Plasma treatment as a method for functionalising and improving dispersion of carbon nanotubes in epoxy resins

      Plasma treatment as a method for functionalising and improving dispersion of carbon nanotubes in epoxy resins

      This study reports on the results of plasma-treated carbon nanotubes (CNTs) in the presence of oxygen and ammonia which can be scaled up for relatively large quantities of nanomaterials. The plasma treatment has been shown to change the surface chemistry and energy as well as the morphology of the carbon nanotubes. X-ray photoelectron spectroscopy analysis shows increases in oxygen and nitrogen groups on the oxygen- and ammonia-treated CNTs, respectively. Titration of the enhanced oxygen plasma-treated CNTs reveals an increased presence of carboxylic acid groups at 2.97 wt% whilst bulk density decreases from 151 kg/m3 for untreated carbon nanotubes ...

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    21. Mapping the Histology of the Human Tympanic Membrane by Spatial Domain Optical Coherence Tomography

      Mapping the Histology of the Human Tympanic Membrane by Spatial Domain Optical Coherence Tomography

      The tympanic membrane is one of the major structures of the ear that aids in the hearing process, giving humans one of the five major senses. It is hypothesized that sound induced displacements of the membrane, which allow humans to hear, are directly related to the membrane’s medial layer which is comprised of a network of collagen fibers. Limitations in available medical imaging techniques have thus far inhibited the further study of these fibers. In this paper we detail an imaging system that we developed with the capability to quantitatively and noninvasively image the internal structures of biological tissues ...

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    22. Overestimation of subfoveal choroidal thickness by measurement based on horizontally compressed optical coherence tomography images

      Overestimation of subfoveal choroidal thickness by measurement based on horizontally compressed optical coherence tomography images

      Abstract Purpose  To measure the difference in subfoveal choroidal thickness between 1:1 pixel (horizontally compressed) images and 1:1 micron images in age-related macular degeneration. Methods  This study included 122 eyes from 122 patients diagnosed with age-related macular degeneration. Choroidal thickness was measured using enhanced-depth imaging optical coherence tomography. The measurement line was drawn as a perpendicular line between Bruch’s membrane and the chorio-scleral interface. The thickness was compared between measurements based on a 1:1 pixel image and a 1:1 micron image. Eyes with a straight vertical measurement line and oblique measurement line were classified into ...

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