1. 1-24 of 273 1 2 3 4 ... 10 11 12 »
    1. Optical coherence tomography with a 2.8-mm beam diameter and sensorless defocus and astigmatism correction

      Optical coherence tomography with a 2.8-mm beam diameter and sensorless defocus and astigmatism correction

      An optical coherence tomography (OCT) system with a 2.8-mm beam diameter is presented. Sensorless defocus correction can be performed with a Badal optometer and astigmatism correction with a liquid crystal device. OCT B-scans were used in an image-based optimization algorithm for aberration correction. Defocus can be corrected from − 4.3    D −4.3  D to + 4.3    D +4.3  D and vertical and oblique astigmatism from − 2.5    D −2.5  D to + 2.5    D +2.5  D . A contrast gain of 6.9 times was measured after aberration correction. In comparison with a 1.3-mm beam ...

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      Mentions: Barry Cense
    2. Dynamic multimodal full-field optical coherence tomography and fluorescence structured illumination microscopy

      Dynamic multimodal full-field optical coherence tomography and fluorescence structured illumination microscopy

      We report on the development of a configuration of a multimodal full-field optical coherence tomography (FF-OCT) and fluorescence microscope. Our system can simultaneously acquire FF-OCT and structured illumination microscopy images. Dynamic parallel evolution of tissue microstructures and biochemical environments can be visualized. We use high numerical aperture objectives to optimize the combination of the two modalities. We imaged the propagation of mechanical waves initiated by calcium waves in a heart wall to illustrate the interest of simultaneous recording of mechanical and biochemical information.

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    3. Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 2: implementation

      Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 2: implementation

      We introduce a theoretical method for simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography (FD-OCT) without any auxiliary arrangement. The input data to the formalism are the FD-OCT measured optical path lengths (OPLs) and properly selected spectral components of FD-OCT interference spectrum. The outputs of the formalism can be affected significantly by uncertainty in measuring the OPLs. An optimization method is introduced to deal with the relatively large amount of uncertainty in measured OPLs and enhance the final results. Simulation result shows that by using the optimization method, indices can be extracted ...

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    4. Automated three-dimensional registration and volume rebuilding for wide-field angiographic and structural optical coherence tomography

      Automated three-dimensional registration and volume rebuilding for wide-field angiographic and structural optical coherence tomography

      We propose a three-dimensional (3-D) registration method to correct motion artifacts and construct the volume structure for angiographic and structural optical coherence tomography (OCT). This algorithm is particularly suitable for the nonorthogonal wide-field OCT scan acquired by a ultrahigh-speed swept-source system ( > 200    kHz >200  kHz A-scan rate). First, the transverse motion artifacts are corrected by the between-frame registration based on en face OCT angiography (OCTA). After A-scan transverse translation between B-frames, the axial motions are corrected based on the rebuilt boundary of inner limiting membrane. Finally, a within-frame registration is performed for local optimization based on cross-sectional OCTA. We evaluated ...

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    5. Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 1: theory

      Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 1: theory

      We introduce a theoretical framework for simultaneous refractive index and thickness measurement of multilayer systems using the Fourier domain optical coherence tomography (FD-OCT) system without any previous information about the item under investigation. The input data to the new formalism are the FD-OCT measured optical path lengths and properly selected spectral components of the FD-OCT interference spectrum. No additional arrangement, reference reflector, or mechanical scanning is needed in this approach. Simulation results show that the accuracy of the extracted parameters depends on the index contrast of the sample while it is insensitive to the sample’s thickness profile. For transparent ...

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    6. Impact of temporal resolution on estimating capillary RBC-flux with optical coherence tomography

      Impact of temporal resolution on estimating capillary RBC-flux with optical coherence tomography

       Optical coherence tomography (OCT) has been used to measure capillary red blood cell (RBC) flux. However, one important technical issue is that the accuracy of this method is subject to the temporal resolution (ΔtΔt) of the repeated RBC-passage B-scans. A ceiling effect arises due to an insufficient ΔtΔt limiting the maximum RBC-flux that can be measured. In this letter, we first present simulations demonstrating that Δt=1.5  msΔt=1.5  mspermits measuring RBC-flux up to 150  RBCs/s150  RBCs/s with an underestimation of 9%. The simulations further show that measurements with Δt=3 ...

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    7. Detection of cervical intraepithelial neoplasia by using optical coherence tomography in combination with microscopy

      Detection of cervical intraepithelial neoplasia by using optical coherence tomography in combination with microscopy

      Optical coherence tomography (OCT) is a noninvasive high-resolution imaging technique that permits the detection of cancerous and precancerous lesions of the uterine cervix. The purpose of this study was to evaluate a new system that integrates an OCT device into a microscope. OCT images were taken from loop electrosurgical excision procedure (LEEP) specimens under microscopic guidance. The images were blinded with respect to their origin within the microscopic image and analyzed independently by two investigators using initially defined criteria and later compared to the corresponding histology. Sensitivity and specificity were calculated with respect to the correct identification of high-grade squamous ...

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    8. Fully automated macular pathology detection in retina optical coherence tomography images using sparse coding and dictionary learning

      Fully automated macular pathology detection in retina optical coherence tomography images using sparse coding and dictionary learning

      We propose a framework for automated detection of dry age-related macular degeneration (AMD) and diabetic macular edema (DME) from retina optical coherence tomography (OCT) images, based on sparse coding and dictionary learning. The study aims to improve the classification performance of state-of-the-art methods. First, our method presents a general approach to automatically align and crop retina regions; then it obtains global representations of images by using sparse coding and a spatial pyramid; finally, a multiclass linear support vector machine classifier is employed for classification. We apply two datasets for validating our algorithm: Duke spectral domain OCT (SD-OCT) dataset, consisting of ...

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    9. Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation

      Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation

      Vision loss due to corneal injuries or diseases can be treated by transplantation of human corneal grafts (keratoplasty). However, quality assurance in retrieving and cultivating the tissue transplants is confined to visual and microbiological testing. To identify previous refractive surgery or morphological alterations, an automatic, noncontact, sterile screening procedure is required. Twenty-three corneal grafts have been measured in organ culture with a clinical spectral-domain optical coherence tomographer. Employing a biconic surface fit with 10 degrees of freedom, the radii of curvature and conic constants could be estimated for the anterior and posterior corneal surfaces. Thereupon, central corneal thickness, refractive values ...

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    10. Optical sensing method to analyze germination rate of Capsicum annum seeds treated with growth-promoting chemical compounds using optical coherence tomography

      Optical sensing method to analyze germination rate of Capsicum annum seeds treated with growth-promoting chemical compounds using optical coherence tomography

      Seed germination rate differs based on chemical treatments, and nondestructive measurements of germination rate have become an essential requirement in the field of agriculture. Seed scientists and other biologists are interested in optical sensing technologies-based biological discoveries due to nondestructive detection capability. Optical coherence tomography (OCT) has recently emerged as a powerful method for biological and plant material discoveries. We report an extended application of OCT by monitoring the germination rate acceleration of chemically primed seeds. To validate the versatility of the method, Capsicum annum seeds were primed using three chemical compounds: sterile distilled water (SDW), butandiol, and 1-hexadecene. Monitoring ...

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    11. In vivo three-dimensional imaging of human corneal nerves using Fourier-domain optical coherence tomography

      In vivo three-dimensional imaging of human corneal nerves using Fourier-domain optical coherence tomography

      We have employed Fourier-domain optical coherence tomography (FD-OCT) to achieve corneal nerve imaging, which could be useful in surgical planning and refractive surgery. Because the three-dimensional (3-D) images of the corneal nerves were acquired in vivo, unintentional movement of the subject during the measurement led to imaging artifacts. These artifacts were compensated for with a series of signal processing techniques, namely realigning A-scan images to flatten the boundary and cross-correlating adjacent B-scan images. To overcome the undesirably large signal from scattering at the corneal surface and iris, volume rendering and maximum intensity projections were performed with only the data taken ...

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    12. Phase variance optical coherence microscopy for label-free imaging of the developing vasculature in zebrafish embryos

      Phase variance optical coherence microscopy for label-free imaging of the developing vasculature in zebrafish embryos

      A phase variance optical coherence microscope (pvOCM) has been created to image blood flow in the microvasculature of zebrafish embryos, without the use of exogenous labels. The pvOCM imaging system has axial and lateral resolutions of 2.8    μ m 2.8  μm in tissue and imaging depth of more than 100    μ m 100  μm . Images of 2 to 5 days postfertilization zebrafish embryos identified the detailed anatomical structure based on OCM intensity contrast. Phase variance contrast offered visualization of blood flow in the arteries, veins, and capillaries. The pvOCM images of the vasculature were confirmed by direct comparisons with fluorescence ...

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    13. Development of a first-generation miniature multiple reference optical coherence tomography imaging device

      Development of a first-generation miniature multiple reference optical coherence tomography imaging device

      Multiple reference optical coherence tomography (MR-OCT) is a technology ideally suited to low-cost, compact OCT imaging. This modality is an extension of time-domain OCT with the addition of a partial mirror in front of the reference mirror. This enables extended, simultaneous depth scanning with the relatively short scan range of a miniature voice coil motor on which the scanning mirror is mounted. This work details early stage development of the first iteration of a miniature MR-OCT device. This iteration utilizes a fiber-coupled input from an off-board superluminescent diode. The dimensions of the module are 40×57  mm40×57  mm ...

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    14. Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography

      Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography

      Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation ...

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    15. Quantitative evaluation of atherosclerotic plaques using cross-polarization optical coherence tomography, nonlinear, and atomic force microscopy

      Quantitative evaluation of atherosclerotic plaques using cross-polarization optical coherence tomography, nonlinear, and atomic force microscopy

      A combination of approaches to the image analysis in cross-polarization optical coherence tomography (CP OCT) and high-resolution imaging by nonlinear microscopy and atomic force microscopy (AFM) at the different stages of atherosclerotic plaque development is studied. This combination allowed us to qualitatively and quantitatively assess the disorganization of collagen in the atherosclerotic arterial tissue (reduction and increase of CP backscatter), at the fiber (change of the geometric distribution of fibers in the second-harmonic generation microscopy images) and fibrillar (violation of packing and different nature of a basket-weave network of fibrils in the AFM images) organization levels. The calculated CP channel-related ...

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    16. Adaptive optics assisted and optical coherence tomography guided fs-laser system for ophthalmic surgery in the posterior eye

      Adaptive optics assisted and optical coherence tomography guided fs-laser system for ophthalmic surgery in the posterior eye

      While fs-lasers are clinically established for surgery in the anterior eye, their use in the posterior eye is impeded by aberrations and focus position errors. We implemented a laboratory system to investigate whether fs-laser surgery in the posterior eye is made more feasible by aberration correction and tomographic image guidance. Aberration correction is obtained by adaptive optics (AO) and the image guidance is accomplished by optical coherence tomography (OCT). System characteristic measurements and cutting experiments were performed inside an eye model. By aberration correction, wavefront errors were reduced from 270 nm root-mean-square (rms) to 64 nm rms, ignoring Zernike terms ...

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    17. Feasibility study: protein denaturation and coagulation monitoring with speckle variance optical coherence tomography

      Feasibility study: protein denaturation and coagulation monitoring with speckle variance optical coherence tomography

      We performed the feasibility study using speckle variance optical coherence tomography (SvOCT) to monitor the thermally induced protein denaturation and coagulation process as a function of temperature and depth. SvOCT provided the depth-resolved image of protein denaturation and coagulation with microscale resolution. This study was conducted using egg white. During the heating process, as the temperature increased, increases in the speckle variance signal was observed as the egg white proteins coagulated. Additionally, by calculating the cross-correlation coefficient in specific areas, denaturized egg white conditions were successfully estimated. These results indicate that SvOCT could be used to monitor the denaturation process ...

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    18. Quantitative optical coherence microscopy for the in situ investigation of the biofilm

      Quantitative optical coherence microscopy for the in situ investigation of the biofilm

      his paper explores the potential of optical coherence microscopy (OCM) for the in situ monitoring of biofilm growth. The quantitative imaging of the early developmental biology of a representative biofilm, Klebsiella pneumonia (KP-1), was performed using a swept source-based Fourier domain OCM system. The growth dynamics of the KP-1 biofilms and their transient response under perturbation was investigated using the enface visualization of microcolonies and their spatial localization. Furthermore, the optical density (OD) and planar density of the biofilms are calculated using an OCM technique and compared with OD and colony forming units measured using standard procedures via the sampling ...

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    19. Analysis and compensation for the effect of the catheter position on image intensities in intravascular optical coherence tomography

      Analysis and compensation for the effect of the catheter position on image intensities in intravascular optical coherence tomography

      Intravascular optical coherence tomography (IVOCT) is an imaging technique that is used to analyze the underlying cause of cardiovascular disease. Because a catheter is used during imaging, the intensities can be affected by the catheter position. This work aims to analyze the effect of the catheter position on IVOCT image intensities and to propose a compensation method to minimize this effect in order to improve the visualization and the automatic analysis of IVOCT images. The effect of catheter position is modeled with respect to the distance between the catheter and the arterial wall (distance-dependent factor) and the incident angle onto ...

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    20. Nondestructive imaging of fiber structure in articular cartilage using optical polarization tractography

      Nondestructive imaging of fiber structure in articular cartilage using optical polarization tractography

      Collagen fiber orientation plays an important role in determining the structure and function of the articular cartilage. However, there is currently a lack of nondestructive means to image the fiber orientation from the cartilage surface. The purpose of this study is to investigate whether the newly developed optical polarization tractography (OPT) can image fiber structure in articular cartilage. OPT was applied to obtain the depth-dependent fiber orientation in fresh articular cartilage samples obtained from porcine phalanges. For comparison, we also obtained collagen fiber orientation in the superficial zone of the cartilage using the established split-line method. The direction of each ...

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    21. Combined optical coherence tomography and hyperspectral imaging using a double-clad fiber coupler

      Combined optical coherence tomography and hyperspectral imaging using a double-clad fiber coupler

      This work demonstrates the combination of optical coherence tomography (OCT) and hyperspectral imaging (HSI) using a double-clad optical fiber coupler. The single-mode core of the fiber is used for OCT imaging, while the inner cladding of the double-clad fiber provides an efficient way to capture the reflectance spectrum of the sample. The combination of both methods enables three-dimensional acquisition of the sample morphology with OCT, enhanced with complementary molecular information contained in the hyperspectral image. The HSI data can be used to highlight the presence of specific molecules with characteristic absorption peaks or to produce true color images overlaid on ...

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    22. Two-axis polydimethylsiloxane-based electromagnetic microelectromechanical system scanning mirror for optical coherence tomography

      Two-axis polydimethylsiloxane-based electromagnetic microelectromechanical system scanning mirror for optical coherence tomography

      Compact size and fast imaging abilities are key requirements for the clinical implementation of an optical coherence tomography (OCT) system. Among the various small-sized technology, a microelectromechanical system (MEMS) scanning mirror is widely used in a miniaturized OCT system. However, the complexities of conventional MEMS fabrication processes and relatively high costs have restricted fast clinical translation and commercialization of the OCT systems. To resolve these problems, we developed a two-axis polydimethylsiloxane (PDMS)-based MEMS (2A-PDMS-MEMS) scanning mirror through simple processes with low costs. It had a small size of 15 × 15 × 15    mm 3 15×15×15  mm3 , was fast ...

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    23. Quantifying tissue viscoelasticity using optical coherence elastography and the Rayleigh wave model

      Quantifying tissue viscoelasticity using optical coherence elastography and the Rayleigh wave model

      This study demonstrates the feasibility of using the Rayleigh wave model (RWM) in combination with optical coherence elastography (OCE) technique to assess the viscoelasticity of soft tissues. Dispersion curves calculated from the spectral decomposition of OCE-measured air-pulse induced elastic waves were used to quantify the viscoelasticity of samples using the RWM. Validation studies were first conducted on 10% gelatin phantoms with different concentrations of oil. The results showed that the oil increased the viscosity of the gelatin phantom samples. This method was then used to quantify the viscoelasticity of chicken liver. The Young’s modulus of the chicken liver tissues ...

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    24. Adaptive optics full-field optical coherence tomography

      Adaptive optics full-field optical coherence tomography

      We describe a simple and compact full-field optical coherence tomography (FFOCT) setup coupled to a transmissive liquid crystal spatial light modulator (LCSLM) to induce or correct aberrations. To reduce the system complexity, strict pupil conjugation was abandoned because low-order aberrations are often dominant. We experimentally confirmed a recent theoretical and experimental demonstration that the image resolution was almost insensitive to aberrations that mostly induce a reduction of the signal level. As a consequence, an image-based algorithm was applied for the optimization process by using the FFOCT image intensity as the metric. Aberration corrections were demonstrated with both an USAF resolution ...

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    1-24 of 273 1 2 3 4 ... 10 11 12 »
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