1. 73-96 of 143 « 1 2 3 4 5 6 »
    1. Theoretical model of volumetric objects imaging in a microscope

      Theoretical model of volumetric objects imaging in a microscope

      Optical microscope is a well known instrument with many applications in biomedical imaging and precise measurements. Nowadays a lot of modalities arose, which utilize combination of a microscope arrangement with other optical techniques, such as holography or low-coherence interferometry. The most important features of these modalities are related to the diffraction or coherence effects due to such combination, rather than to exact ways of lens aberrations correction. Therefore for analysis and understanding of these effects a theoretical model is necessary, which would be rigorous enough to take into account the diffraction and coherence effects and in the same time simple ...

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    2. Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

      Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

      Optical coherence tomography (OCT) is a non-invasive three-dimensional imaging system that is capable of producing high resolution in-vivo images. OCT is approved for use in clinical trials in Japan, USA and Europe. For OCT to be used effectively in a clinical diagnosis, a method of standardisation is required to assess the performance across different systems. This standardisation can be implemented using highly accurate and reproducible artefacts for calibration at both installation and throughout the lifetime of a system. Femtosecond lasers can write highly reproducible and highly localised micro-structured calibration artefacts within a transparent media. We report on the fabrication of ...

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    3. Comparative analysis of optical coherence tomography signal and microhardness for demineralization evaluation of human tooth enamel

      Comparative analysis of optical coherence tomography signal and microhardness for demineralization evaluation of human tooth enamel

      The diagnosis of dental caries at an early stage enables the implementation of conservative treatments based on dental preservation. Several diagnostic methods have been developed, like visual-tactile and radiographic are the most commons but are limited for this application. The Optical Coherence Tomography is a technique that provides information of optical properties of enamel, which may change due to the decay process. The objective of this study was to evaluate the ability of OCT to detect different stages of demineralization of tooth enamel during the development of artificial caries lesions, taking as a reference standard for comparison sectional microhardness testing ...

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    4. Full-range spectral domain optical coherence tomography using fiber-based sample scanner as self-phase shifter

      Full-range spectral domain optical coherence tomography using fiber-based sample scanner as self-phase shifter

      We propose full-range spectral domain optical coherence tomography equipped with a fiber-based sample scanner, which is used for sample scanning and phase shifting for full-range image at the same time. For a fiber-based sample scanner, since the fiber tip oscillates as a free standing cantilever in general, unintentional phase shift occurs inevitably. The unintentional phase shift was used for eliminating the bothersome complex conjugate ghost image of OCT. In addition, fiber was tilted a few degree to give proper phase shift. In this scheme, moreover, image can be obtained without any physical modification of the scanner. To realize this technique ...

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    5. Anti-stokes effect CCD camera and SLD based optical coherence tomography for full-field imaging in the 1550nm region

      Anti-stokes effect CCD camera and SLD based optical coherence tomography for full-field imaging in the 1550nm region

      Full-field Optical coherence tomography is an en-face interferometric imaging technology capable of carrying out high resolution cross-sectional imaging of the internal microstructure of an examined specimen in a non-invasive manner. The presented system is based on competitively priced optical components available at the main optical communications band located in the 1550 nm region. It consists of a superluminescent diode and an anti-stokes imaging device. The single mode fibre coupled SLD was connected to a multi-mode fibre inserted into a mode scrambler to obtain spatially incoherent illumination, suitable for OCT wide-field modality in terms of crosstalk suppression and image enhancement. This ...

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    6. Evaluating elastic properties of heterogeneous soft tissue by surface acoustic waves detected by phase-sensitive optical coherence tomography

      Evaluating elastic properties of heterogeneous soft tissue by surface acoustic waves detected by phase-sensitive optical coherence tomography

      The combined use of surface acoustic wave (SAW) and phase-sensitive optical coherence tomography (PhS-OCT) is useful to evaluate the elasticity of layered biological tissues, such as normal skin. However, the pathological tissue is often originated locally, leading to the alternation of mechanical properties along both axial and lateral directions. We present a feasibility study on whether the SAW technique is sensitive to detect the alternation of mechanical property along the lateral direction within tissue, which is important for clinical utility of this technique to localize diseased tissue. Experiments are carried out on purposely designed tissue phantoms and ex vivo chicken ...

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    7. High resolution biomedical imaging—multimodal ultrasound microscope and combination with optics

      High resolution biomedical imaging—multimodal ultrasound microscope and combination with optics

      High frequency ultrasound imaging has evolved from classical acoustic microscopy to the multimodal ultrasound microscope which is available for quantitative C-mode, surface acoustic impedance mode and 3D-mode imaging. The evolution has realized both quantitative parametric imaging and easier observation. Quantitative C-mode representing two-dimensional distribution of attenuation or sound speed is realized by frequency-domain analysis of a single pulse by a high speed digitizer. Because the square of sound speed is proportional to the tissue elasticity, sound speed imaging provides biomechanical information of the tissues which is especially important in cardiology and orthopedic surgery. The data also help understanding clinical echo ...

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    8. Optimizing magnetomotive contrast of SPIO-labeled platelets for thrombosis imaging in optical coherence tomography

      Optimizing magnetomotive contrast of SPIO-labeled platelets for thrombosis imaging in optical coherence tomography

      External link. Please review our privacy policy . Rehydratable, lyophilized platelets loaded with superparamagnetic iron oxides (SPIOs) has the potential to provide magnetomotive imaging contrast to sites of vascular damage, including thrombosis complicating atherosclerosis and hemorrhage. Magnetomotive optical coherence tomography (MMOCT) contrasts SPIO-platelets based on their nanoscale, magnetically-induced motion. We report improvements in MMOCT imaging contrast and sensitivity by optimizing the magnetic properties and SPIO loading of the platelets. SPIO-platelets have been shown to specifically adhere to sites of vascular damage in porcine arteries ex vivo. This may lead to new methods for detecting internal bleeding and monitoring the formation of ...

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    9. Automated segmentation of intramacular layers in Fourier domain optical coherence tomography structural images from normal subjects

      Automated segmentation of intramacular layers in Fourier domain optical coherence tomography structural images from normal subjects

      Segmentation of optical coherence tomography (OCT) cross-sectional structural images is important for assisting ophthalmologists in clinical decision making in terms of both diagnosis and treatment. We present an automatic approach for segmenting intramacular layers in Fourier domain optical coherence tomography (FD-OCT) images using a searching strategy based on locally weighted gradient extrema, coupled with an error-removing technique based on statistical error estimation. A two-step denoising preprocess in different directions is also employed to suppress random speckle noise while preserving the layer boundary as intact as possible. The algorithms are tested on the FD-OCT volume images obtained from four normal subjects ...

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    10. Application of optical coherence tomography and high-frequency ultrasound imaging during noninvasive laser vasectomy

      Application of optical coherence tomography and high-frequency ultrasound imaging during noninvasive laser vasectomy

      A noninvasive approach to vasectomy may eliminate male fear of complications related to surgery and increase its acceptance. Noninvasive laser thermal occlusion of the canine vas deferens has recently been reported. Optical coherence tomography (OCT) and high-frequency ultrasound (HFUS) are compared for monitoring laser thermal coagulation of the vas in an acute canine model. Bilateral noninvasive laser coagulation of the vas was performed in six dogs (n = 12 vasa) using a Ytterbium fiber laser wavelength of 1075 nm, incident power of 9.0 W, pulse duration of 500 ms, pulse rate of 1 Hz, and 3-mm-diameter spot. Cryogen spray cooling ...

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    11. Miniature image guided three-axis scanning and positioning system

      Miniature image guided three-axis scanning and positioning system

      We have developed a high precision three axes scanning and positioning system for integration with Multifunctional Image Guided Surgical (MIGS) Platform. The stage integrates three main components: an optical coherence tomography (OCT) probe, laser scalpel and suction cup. The requirements for this stage were to provide scanning area of 400mm2, resolution of less than 10 microns and scanning velocity in the range of 10 - 40 mm/s. The stage was modeled using computer aided design software NX Unigraphics. In addition to the parameters mentioned above, additional boundary conditions for the stage were set as low volume and modularity. Optimized stage ...

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    12. Qualitative investigation of fresh human scalp hair with full-field optical coherence tomography

      Qualitative investigation of fresh human scalp hair with full-field optical coherence tomography

      We have investigated depth-resolved cellular structures of unmodified fresh human scalp hairs with ultrahigh-resolution full-field optical coherence tomography (FF-OCT). The Linnik-type white light interference microscope has been home-implemented to observe the micro-internal layers of human hairs in their natural environment. In hair shafts, FF-OCT has qualitatively revealed the cellular hair compartments of cuticle and cortex layers involved in keratin filaments and melanin granules. No significant difference between black and white hair shafts was observed except for absence of only the melanin granules in the white hair, reflecting that the density of the melanin granules directly affects the hair color. Anatomical ...

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    13. Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles

      Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles

      The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed ...

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    14. Numerical analysis of aperiodic photonic crystal fiber structures for supercontinuum generation

      Numerical analysis of aperiodic photonic crystal fiber structures for supercontinuum generation

      An unconventional photonic crystal fiber (PCF) is designed in order to obtain supercontinuum (SC) generation. The distance of the air hole rings is not constant, but it follows the Thue-Morse (ThMo) aperiodic sequence. The spectral broadening of high power femtosecond (fs) input pulses in anomalous dispersion regime is investigated by means of a homemade computer code, based on the generalized nonlinear Schrödinger equation (GNLSE) and implemented via the symmetrized split-step Fourier method (S-SSF). A lot of ThMo PCF transversal sections are simulated, and the one providing the flattest and the widest spectrum is identified and further refined by varying the ...

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    15. Optical characters and texture maps of skin and the aging mechanism by use of multiphoton microscopy and optical coherence tomography

      Optical characters and texture maps of skin and the aging mechanism by use of multiphoton microscopy and optical coherence tomography

      Cutaneous aging is a complicated biological process affecting different constituents of skin, which can be divided into two types: the chronological aging and the photo-aging. The two cutaneous aging processes often co-exist accompanying with each other. The effects are often overlapped including changes in epithelium and dermis. The degeneration of collagen is a major factor in dermal alteration with aging. In this study, multiphoton microscopy (MPM) with its high resolution imaging and optical coherence tomography (OCT) with its depth resolved imaging were used to study the anti-aging dermatology in vivo. It was attempted to make the optical parameter and texture ...

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    16. Multimodal full-field optical coherence tomography on biological tissue: toward all optical digital pathology

      Multimodal full-field optical coherence tomography on biological tissue: toward all optical digital pathology

      Optical Coherence Tomography (OCT) is an efficient technique for in-depth optical biopsy of biological tissues, relying on interferometric selection of ballistic photons. Full-Field Optical Coherence Tomography (FF-OCT) is an alternative approach to Fourier-domain OCT (spectral or swept-source), allowing parallel acquisition of en-face optical sections. Using medium numerical aperture objective, it is possible to reach an isotropic resolution of about 1x1x1 m. After stitching a grid of acquired images, FF-OCT gives access to the architecture of the tissue, for both macroscopic and microscopic structures, in a non-invasive process, which makes the technique particularly suitable for applications in pathology. Here we report ...

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    17. Office based multi-functional anterior eye segment optical coherence tomography

      Office based multi-functional anterior eye segment optical coherence tomography

      An office based Doppler and polarization sensitive swept-source optical coherence tomography (Doppler-PS-SS-OCT) was developed for diagnosis and evaluation of abnormalities of anterior eye segment in clinic. A healthy eye was measured in vivo by the Doppler PS-OCT. The results showed that the Doppler PS-OCT may have potential to identify blood vessels and discriminate fibrous tissues in abnormalities, such as scarring in bleb, and scleral inflammation.

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    18. Polarization-sensitive optical coherence tomography using continuous polarization modulation with arbitrary phase modulation amplitude

      Polarization-sensitive optical coherence tomography using continuous polarization modulation with arbitrary phase modulation amplitude

      We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated ...

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    19. Endomicroscopy Technologies and Biomedical Applications

      Endomicroscopy Technologies and Biomedical Applications

      Recent years have witnessed rapid developments of highresolution optical imaging technologies, including (but not limited to) confocal, multispectral, optical coherence tomography, multiphoton fluorescence, second harmonic generation, Raman and/or coherent anti-Stokes Raman spectroscopy, and stimulated Raman scattering microscopy. The highresolution, noninvasive (or minimally invasive), and real-time imaging capability make these technologies well positioned for performing “optical biopsy” in situ and in real time, with a resolution approaching or at that of standard histology. Clinical translation of these technologies, particularly for assessing internal organs, requires miniature probes for delivery, scanning, and collection of the probing/imaging beams. Endomicroscopy is emerging as ...

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    20. Automatic three-dimensional registration of intravascular optical coherence tomography images

      Automatic three-dimensional registration of intravascular optical coherence tomography images

      Intravascular optical coherence tomography (IV-OCT) is a catheter-based high-resolution imaging technique able to visualize the inner wall of the coronary arteries and implanted devices in vivo with an axial resolution below 20 μm. IV-OCT is being used in several clinical trials aiming to quantify the vessel response to stent implantation over time. However, stent analysis is currently performed manually and corresponding images taken at different time points are matched through a very labor-intensive and subjective procedure. We present an automated method for the spatial registration of IV-OCT datasets. Stent struts are segmented through consecutive images and three-dimensional models of the ...

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    21. Optical coherence photoacoustic microscopy: accomplishing optical coherence tomography and photoacoustic microscopy with a single light source

      Optical coherence photoacoustic microscopy: accomplishing optical coherence tomography and photoacoustic microscopy with a single light source

      We developed optical coherence photoacoustic microscopy (OC-PAM) to demonstrate that the functions of optical coherence tomography (OCT) and photoacoustic microscopy (PAM) can be achieved simultaneously by using a single illuminating light source. We used a pulsed broadband laser centered at 580 nm and detected the absorbed photons through photoacoustic detection and the back-scattered photons with an interferometer. In OC-PAM, each laser pulse generates both one OCT A-line and one PAM A-line simultaneously; as a result, the two imaging modalities are intrinsically co-registered in the lateral directions. In vivo images of the mouse ear were acquired to demonstrate the capabilities of ...

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    22. Differential phase-contrast, swept-source optical coherence tomography at 1060 nm for in vivo human retinal and choroidal vasculature visualization

      Differential phase-contrast, swept-source optical coherence tomography at 1060 nm for in vivo human retinal and choroidal vasculature visualization

      Human retinal and choroidal vasculature was visualized by a differential phase-contrast (DPC) method using high-speed, swept-source optical coherence tomography (SS-OCT) at 1060 nm. The vasculature was recognized as regions of motion by creating differential phase-variance (DPV) tomograms: multiple B-scans of individual slices through the retina were collected and the variance of the phase differences was calculated. DPV captured the small vessels and the meshwork of capillaries associated with the inner retina in en-face images over 4  mm2. The swept-source laser at 1060 nm offered the needed phase sensitivity to perform DPV and generated en-face images that capture motion in the ...

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    23. Real-time geometric lens distortion correction using a graphics processing unit

      Real-time geometric lens distortion correction using a graphics processing unit

      Optical imaging systems often suffer from distortion artifacts which impose important limitations on the direct interpretation of the images. It is possible to correct for these aberrations through image processing, but due to their calculation-intensive nature, the required corrections are typically performed offline. However, with image-based applications that operate interactively, real-time correction of geometric distortion artifacts can be vital. We propose a new method to generate undistorted images by implementing the required distortion correction algorithm on a commercial graphics processing unit (GPU), distributing the necessary calculations to many stream processors that operate in parallel. The proposed technique is not limited ...

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    24. Small business technology program (SBIRs) gains new lease on life

      Small business technology program (SBIRs) gains new lease on life

      Although the federal science and technology budget is expected to shrink in the coming years, one of the largest federal R&D programs should continue to thrive: Congress took action last month to extend the $2.3 billion Small Business Innovation Research program for six years. The SBIR’s reauthorization will increase from 2.5% to 3.2% the amount of money that goes to small businesses from the so-called extramural—that is, externally performed—R&D budgets of 11 federal agencies. But it will also shrink the amount of money available for universities, the major external performers of federal ...

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    73-96 of 143 « 1 2 3 4 5 6 »
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