1. 1-24 of 525 1 2 3 4 ... 20 21 22 »
    1. Spectral domain optical coherence tomography with extended depth-of-focus by aperture synthesis

      Spectral domain optical coherence tomography with extended depth-of-focus by aperture synthesis

      We developed a spectral domain optical coherence tomography (SD-OCT) with an extended depth-of-focus (DOF) by synthetizing aperture. For a designated Gaussian-shape light source, the lateral resolution was determined by the numerical aperture (NA) of the objective lens and can be approximately maintained over the confocal parameter, which was defined as twice the Rayleigh range. However, the DOF was proportional to the square of the lateral resolution. Consequently, a trade-off existed between the DOF and lateral resolution, and researchers had to weigh and judge which was more important for their research reasonably. In this study, three distinct optical apertures were obtained ...

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    2. En-face sectional imaging using single-shot full-field optical coherence tomography (SS-FF-OCT) based on white light emitting diode (WLED)

      En-face sectional imaging using single-shot full-field optical coherence tomography (SS-FF-OCT) based on white light emitting diode (WLED)

      This work reports a Linnik type single shot full-field optical coherence tomography (SS-FF-OCT), which uses a fast generalized analytic signal based complex Riesz transform scheme to reconstruct wide area en-face OCT images. The OCT interferometer is illuminated using a single broad band white light emitting diode (WLED) (wavelength range 470- 850nm, central wavelength 650nm) and detection unit is a two-dimensional (2D) charge complementary metal oxide semiconductor (CMOS) camera. The measured axial and lateral resolution (using 4x, NA=0.1 microscope objective) of the present system is 0.9μm and 3.9μm, very close to theoretical values. The measured ...

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      Mentions: Wen-Chuan Kuo
    3. Wavelength-swept fiber laser based on acousto-optic tuning method

      Wavelength-swept fiber laser based on acousto-optic tuning method

      In this study, we have demonstrated a wavelength-swept fiber laser based on an acousto-optic tunable filter(AOTF) as a selective element and a semiconductor optical amplifier(SOA) as a gain medium in an internal fiber ring cavity. The light deriving from one port of the SOA goes through an optical isolator, the AOTF, a fiber coupler and a polarized controller successively, then it goes back to the other port of the SOA to form a ring cavity. The laser output is from another port of the fiber coupler. The laser made by this method is mainly used for swept-source optical ...

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    4. Endoscopic optical coherence tomography using compressive sensing

      Endoscopic optical coherence tomography using compressive sensing

      Conventionally endoscopic OCT images are reconstructed by uniform sampling in both axial and transverse direction of the image. To shorten the scanning time and reduce the acquisition data, we propose to sparsely sample the axial scans and use compressive sensing (CS) to reconstruct the full endoscopic OCT image with randomly chosen axial scans that are much less than conventional Nyquist criteria requirement. And we study the ratio of sparse sampling numerically and experimentally that are required to reconstruct acceptable OCT images. We demonstrate that the OCT image acquisition time can be significantly reduced because of much less acquired data.

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    5. All-optically integrated multimodality imaging system: combined photoacoustic microscopy, optical coherence tomography, and fluorescence imaging

      All-optically integrated multimodality imaging system: combined photoacoustic microscopy, optical coherence tomography, and fluorescence imaging

      We have developed a multimodality imaging system by optically integrating all-optical photoacoustic microscopy (AOPAM), optical coherence tomography (OCT) and fluorescence microscopy (FLM) to provide complementary information including optical absorption, optical back-scattering and fluorescence contrast of biological tissue. By sharing the same low-coherence Michelson interferometer, AOPAM and OCT could be organically optically combined to obtain the absorption and scattering information of the biological tissues. Also, owing to using the same laser source and objective lens, intrinsically registered photoacoustic and fluorescence signals are obtained to present the radiative and nonradiative transition process of absorption. Simultaneously photoacoustic angiography, tissue structure and fluorescence molecular ...

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    6. In vivo noninvasive measurement of preprandial and postprandial blood glucose using optical coherence tomography

      In vivo noninvasive measurement of preprandial and postprandial blood glucose using optical coherence tomography

      Blood glucose concentration measurement is essential for the diagnosis and treatment of diabetes. However, conventional glucose measurement methods are invasive and not suitable for real-time monitoring. This study demonstrated a noninvasive blood glucose measurement method using optical coherence tomography to image human lip in vivo. Optical coherence tomography (OCT) is a noninvasive and depth-resolved technique capable of acquiring tissue structure images in real time. Human lip has very thin skin and is full of blood vessels, which is appropriate for noninvasive glucose measurement. To verify the feasibility of OCT for glucose concentration monitoring, two groups of OCT imaging data were ...

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    7. A segmental dispersion compensation method to improve axial resolution of specified layer in FD-OCT

      A segmental dispersion compensation method to improve axial resolution of specified layer in FD-OCT

      A segmental dispersion compensation method is proposed to compensate the dispersion in frequency domain optical coherence tomography. Tomographic imaging for epidermal layer of an onion slice is achieved in the experimental setup using optical fiber. The axial resolution of the tomography can be improved by using segmental dispersion compensation, because this dispersion compensation method employs segmental dispersion coefficients for the different lateral positions in one specific layer. Comparing with the traditional dispersion compensation method, segmental dispersion compensation method has the capability of separating the specified layer of sample and eliminating the dispersion broadening effect of specified layer

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    8. A standard model eye with micro scale multilayer structure for ophthalmic optical coherence tomography equipment

      A standard model eye with micro scale multilayer structure for ophthalmic optical coherence tomography equipment

      Optical coherence tomography (OCT) has been widely applied in diagnosis of eye diseases during the last 20 years. Differing from traditional two-dimension imaging technologies, OCT could also provide cross-sectional information of target tissues simultaneously and precisely. As well known, axial resolution is one of the most critical parameters impacting the OCT image quality, which determines whether an accurate diagnosis could be obtained. Therefore, it is important to evaluate the axial resolution of an OCT equipment. Phantoms always play an important role in the standardization and validation process. Here, a standard model eye with micro-scale multilayer structure was custom designed and ...

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    9. Full-field optical coherence tomography apply in sphere measurements

      Full-field optical coherence tomography apply in sphere measurements

      The geometry of a spherical surface, for example that of a precision optic, is completely determined by the radius –of-curvature at one point and the deviation from the perfect spherical form at all other points of the sphere. Full-field Optical Coherence Tomography (FF-OCT) is a parallel detection OCT technique that utilizes a 2D detector array. This technique avoids mechanical scanning in imaging optics, thereby speeding up the imaging process and enhancing the quality of images. The current paper presents an FF-OCT instrument that is designed to be used in sphere measurement with the principle of multiple delays (MD) OCT to ...

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    10. A standard test method based on point spread function for three-dimensional imaging system

      A standard test method based on point spread function for three-dimensional imaging system

      Point spread function (PSF) theory has been demonstrated as proof of concept in evaluation of spatial resolution of three dimensional imaging technology like optical coherence tomography (OCT) and confocal microscopy. A robust test target and associated evaluation algorithm are in demand for keeping regular quality assurance and inter-comparison of such 3D imaging system performance. To achieve this goal, standard-size micro spheres were utilized to develop PSF phantoms. The OCT system was investigated with the microsphere PSF phantom. Differing from previous study, a statistical model comprising data from hundreds of scatterers was established to acquire the PSF distribution and variation. The ...

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    11. Automated segmentation of nine retinal layers with layer thickness information on SD-OCT images

      Automated segmentation of nine retinal layers with layer thickness information on SD-OCT images

      Changes in the structure of the retina can reflect a variety of pathological physiological changes. To analyze the structural characteristics of the retina layers, an automated segmentation algorithm of retinal layers was developed. This algorithm, based on the Dijkstra's algorithm, limiting the search region with statistics information of layer thickness information, constructs a graph from every 2D OCT image and use a shortest path algorithm to iteratively segment multiple layers. The experiments showed that this segmentation algorithm has great repeatability, accuracy, and high efficiency.

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    12. Two-dimensional noise reduction in optical coherence tomography based on the shearlet transform

      Two-dimensional noise reduction in optical coherence tomography based on the shearlet transform

      Image denoising is a very important step in image processing. In recent years, a lot of image denoising algorithms have been proposed, several of them are transform domain based methods, such as wavelet, contourlet, and shearlet. Shearlet is a new type of multiscale geometric analysis tool, which can obtain a sparse representation of the image and produce the optimal approximation. The transform generates shearlet functions with different features by scaling, shearing, and translation of the basic functions. In this paper, we introduced shearlet transformation into optical coherence tomography images to reduce noise, and proposed a multiscale, directional adapted speckle reduction ...

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    13. Non-contact investigation of the corneal biomechanics with air-puff swept source optical coherence tomography

      Non-contact investigation of the corneal biomechanics with air-puff swept source optical coherence tomography

      In this paper, we use swept source optical coherence tomography combined with air-puff module (air-puff SS-OCT) to investigate the properties of the cornea. During OCT measurement the cornea was stimulated by short, air pulse, and corneal response was recorded. In this preliminary study, the air-puff SS-OCT instrument was applied to measure behavior of the porcine corneas under varied, well-controlled intraocular pressure conditions. Additionally, the biomechanical response of the corneal tissue before, during and after crosslinking procedure (CXL) was assessed. Air-puff swept source OCT is a promising tool to extract information about corneal behavior as well as to monitor and assess ...

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    14. A study on optical coherence tomography using high frequency swept source

      A study on optical coherence tomography using high frequency swept source

      Optical coherence tomography based on ultra technology is used for the assessment of subcutaneous tissue. Using high swept laser technology based on Fourier domain mode locking (FDML), the system operated in the 1300 nm wavelength range with axial scan rate of 150 kHz. Imaging at this wavelength range reduces optical scattering and improves imaging penetration depths in the tissues. The laser consists of a semiconductor amplifier as the gain medium, a tunable Fabry-Perot filter to change the wavelengthcand a long fiber ring cavity. The tuning range of laser is 102 nm. A balanced detector is used for spectra collection instead ...

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    15. High efficiency for prostate biopsy qualification with full-field OCT after training

      High efficiency for prostate biopsy qualification with full-field OCT after training

      Full-field optical coherence tomography (FFOCT) offers a fast and non-destructive method of obtaining images of biological tissues at ultrahigh resolution, approaching traditional histological sections. In the context of prostate cancer diagnosis involving multiple biopsies, FFOCT could be used to validate the cores just after they are obtained in order to guide the number of biopsies to be performed. The aim of the study was to define and test a training protocol for efficient FFOCT prostate biopsy assessment. Three readers (a pathologist with previous experience with FFOCT, a pathologist new to FFOCT, and a urologist new to FFOCT) were trained to ...

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    16. The application of diffractive optical elements in the optical coherence tomography

      The application of diffractive optical elements in the optical coherence tomography

      The article investigates the possibility of using diffractive optical elements on an example of the kinoform in the optical coherence tomography (OCT). The article gives a brief overview of modern methods of research in the OCT, the expediency of development hyperchromatic lenses for spectral OCT systems. The authors made the aberration analysis of diffractive optical element (DOE), conducted a review of its application, and the DOE proposed to use in the example of a kinoform as the main force component of the hyperchromatic lens. In conclusion, the article provides examples of developed hybrid lenses for two spectral ranges, lens transmittance ...

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    17. Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability

      Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability

      Recently proposed in vivo label-free optical coherence angiography techniques based on phase and amplitude speckle variability often require additional signal pre- and post processing operations to enhance vessel-contrast. We observe here 1) contrast enhancement by optimizing the signal normalization/weighing before processing; 2) algorithm based on Kasai estimator for phase compensation between processed A-scans to reduce masking role of motion artifacts; and 3) image projection through the imaging depth for en face plotting. We demonstrate the efficiency of proposed additional algorithms as for the microcirculation imaging of hamsters cheek in vivo as for the preliminary microcirculation imaging of patients after ...

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    18. Flexible A-scan rate MHz OCT: computational downscaling by coherent averaging

      Flexible A-scan rate MHz OCT: computational downscaling by coherent averaging

      In order to realize fast OCT-systems with adjustable line rate, we investigate averaging of image data from an FDML based MHz-OCT-system. The line rate can be reduced in software and traded in for increased system sensitivity and image quality. We compare coherent and incoherent averaging to effectively scale down the system speed of a 3.2 MHz FDML OCT system to around 100 kHz in postprocessing. We demonstrate that coherent averaging is possible with MHz systems without special interferometer designs or digital phase stabilisation. We show OCT images of a human finger knuckle joint in vivo with very high quality ...

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    19. Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

      Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

      Selective laser sintering (SLS) enables fast, flexible and cost-efficient production of parts directly from 3D CAD data. However, compared with more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables to optimize production parameters in-situ. We apply optical coherence tomography (OCT) to evaluate components produced by SLS and suggest a route for its application in in-situ process monitoring within the SLS tool for real-time monitoring of the SLS process for assurance, or even dynamic correction of defects during the build. OCT is shown to be a viable technique for evaluation of ...

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    20. Cell sheets image validation of phase-diversity homodyne OCT and effect of the light irradiation on cells

      Cell sheets image validation of phase-diversity homodyne OCT and effect of the light irradiation on cells

      Optical coherence tomography (OCT) is one of powerful 3D tissue imaging tools with no fluorescence staining. We have reported that Phase-Diversity Homodyne OCT developed in Hitachi could be useful for non-invasive regeneration tissue evaluation test. The OCT enables cell imaging because of high resolution (axial resolution; ~2.6 μm, lateral resolution; ~1 μm, in the air), whereas conventional OCT was not used for cell imaging because of low resolution (10~20 μm). Furthermore, the OCT has advantage over other 3D imaging devices in cost because the light source and the objective were originally used as an optical pickup of compact ...

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    21. The how and why of a $10 optical coherence tomography system

      The how and why of a $10 optical coherence tomography system

      Optical Coherence Tomography (OCT) is the fastest growing medical imaging modality with more than $1Bln worth of scans ordered and over $400M worth of equipment shipped in 2010, just nine years after its commercialization. It is at various stages of acceptance and approvals for eye care, coronary care and skin cancer care and is spreading rapidly to other medical specialties. Indeed, it is the leading success of translation of biophotonics science into clinical practice. Significant effort is being made to provide sufficient evidence for efficacy across a broad range of applications, but more needs to be done to radically reduce ...

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    22. 3D registration of intravascular optical coherence tomography and cryo-image volumes for microscopic-resolution validation

      3D registration of intravascular optical coherence tomography and cryo-image volumes for microscopic-resolution validation

      High resolution, 100 frames/sec intravascular optical coherence tomography (IVOCT) can distinguish plaque types, but further validation is needed, especially for automated plaque characterization. We developed experimental and 3D registration methods, to provide validation of IVOCT pullback volumes using microscopic, brightfield and fluorescent cryoimage volumes, with optional, exactly registered cryo-histology. The innovation was a method to match an IVOCT pullback images, acquired in the catheter reference frame, to a true 3D cryo-image volume. Briefly, an 11-parameter, polynomial virtual catheter was initialized within the cryo-image volume, and perpendicular images were extracted, mimicking IVOCT image acquisition. Virtual catheter parameters were optimized to ...

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    23. Voxel based morphometry in optical coherence tomography: validation and core findings

      Voxel based morphometry in optical coherence tomography: validation and core findings

      Optical coherence tomography (OCT) of the human retina is now becoming established as an important modality for the detection and tracking of various ocular diseases. Voxel based morphometry (VBM) is a long standing neuroimaging analysis technique that allows for the exploration of the regional differences in the brain. There has been limited work done in developing registration based methods for OCT, which has hampered the advancement of VBM analyses in OCT based population studies. Following on from our recent development of an OCT registration method, we explore the potential benefits of VBM analysis in cohorts of healthy controls (HCs) and ...

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    24. OCT imaging of myocardium extending to pulmonary vein

      OCT imaging of myocardium extending to pulmonary vein

      In this study, we propose to use optical coherence tomography to enable a direct visualization of myocardium extending into the pulmonary vein (PV). The results showed that there are obvious differences in the morphology of myocardium and fibrous tissue in the transition region of myocardial sleeve, which is in agreement with the histological analysis. In addition, the myocardial area in transition point has three layers in the depth of 1 mm, and the depth-resolved myocardial fiber show different orientation in the different layers. This characteristic was applied for segmentation of the structures of myocardium extending into PV.

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    1-24 of 525 1 2 3 4 ... 20 21 22 »
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