1. 1-24 of 662 1 2 3 4 ... 26 27 28 »
    1. All fiber polarization insensitive detection for spectrometer based optical coherence tomography using optical switch

      All fiber polarization insensitive detection for spectrometer based optical coherence tomography using optical switch

      Polarization dependent image artifacts are common in optical coherence tomography imaging. Polarization insensitive detection scheme for swept source based optical coherence tomography systems is well established but is yet to be demonstrated for all fiber spectrometer-based Fourier domain optical coherence tomography systems. In this work, we present an all fiber polarization insensitive detection scheme for spectrometer based optical coherence tomography systems. Images from chicken breast muscle tissue were acquired to demonstrate the effectiveness of this scheme for the conventional Fourier domain optical coherence tomography system.

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    2. Stable multi-megahertz circular-ranging optical coherence tomography at 1.3 µm

      Stable multi-megahertz circular-ranging optical coherence tomography at 1.3 µm

      In Fourier-domain optical coherence tomography (OCT), the finite bandwidth of the acquisition electronics constrains the depth range and speed of the system. Circular-ranging (CR) OCT methods use optical-domain compression to surpass this limit. However, the CR-OCT system architectures of prior reports were limited by poor stability and were confined to the 1.55 µm wavelength range. In this work, we describe a novel CR-OCT architecture that is free from these limitations. To ensure stable operation, temperature sensitive optical modules within the system were replaced; the kilometer-length fiber spools used in the stretched-pulse mode-locked (SPML) laser was eliminated in favor of ...

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    3. Optical coherence tomography using physical domain data compression to achieve MHz A-scan rates

      Optical coherence tomography using physical domain data compression to achieve MHz A-scan rates

      The three-dimensional volumetric imaging capability of optical coherence tomography (OCT) leads to the generation of large amounts of data, which necessitates high speed acquisition followed by high dimensional image processing and visualization. This signal acquisition and processing pipeline demands high A-scan rates on the front end, which has driven researchers to push A-scan acquisition rates into the MHz regime. To this end, the optical time-stretch approach uses a mode locked laser (MLL) source, dispersion in optical fiber, and a single analog-to-digital converter (ADC) to achieve multi-MHz A-scan rates. While enabling impressive performance this Nyquist sampling approach is ultimately constrained by ...

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    4. Automated plaque characterization using deep learning on coronary intravascular optical coherence tomographic images

      Automated plaque characterization using deep learning on coronary intravascular optical coherence tomographic images

      Accurate identification of coronary plaque is very important for cardiologists when treating patients with advanced atherosclerosis. We developed fully-automated semantic segmentation of plaque in intravascular OCT images. We trained/tested a deep learning model on a folded, large, manually annotated clinical dataset. The sensitivities/specificities were 87.4%/89.5% and 85.1%/94.2% for pixel-wise classification of lipidous and calcified plaque, respectively. Automated clinical lesion metrics, potentially useful for treatment planning and research, compared favorably (<4%) with those derived from ground-truth labels. When we converted the results to A-line classification, they were significantly better (p < 0.05) than ...

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    5. Buffered polarization diverse detection for single-camera polarization-sensitive optical coherence tomography

      Buffered polarization diverse detection for single-camera polarization-sensitive optical coherence tomography

      Herein we propose a method to mitigate a position mismatch problem for a spectral-domain polarization-sensitive optical coherence tomography (SD-PS-OCT) system that uses a single line-scan detection scheme. A single detector-based PS-OCT detects two orthogonal polarization components as two adjacent A-scan signals in turns. Thus, two adjacent A-scan signals are not scattered at a fixed point in time (position mismatch problem), resulting in uncorrelated signals between them. To achieve sequential detection of simultaneously scattered light, a buffering single-mode fiber was connected to one of the two ports coming out of the optical switch, provided a proper time delay. A single-mode optical ...

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    6. Crosstalk-free volumetric in vivo imaging of a human retina with Fourier-domain full-field optical coherence tomography

      Crosstalk-free volumetric in vivo imaging of a human retina with Fourier-domain full-field optical coherence tomography

      Fourier-domain full-field optical coherence tomography (FD-FF-OCT) is currently the fastest volumetric imaging technique that is able to generate a single 3-D volume of retina in less than 9 ms, corresponding to a voxel rate of 7.8 GHz. FD-FF-OCT is based on a fast camera, a rapidly tunable laser source, and Fourier-domain signal detection. However, crosstalk appearing due to multiply scattered light corrupts images with the speckle pattern, and therefore, lowers image quality. Here, for the first time, we report on a system that can acquire essentially crosstalk-free volumes of the retina by using a fast deformable membrane. It enables ...

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    7. Correlation of optical attenuation coefficient estimated using optical coherence tomography with changes in astrocytes and neurons in a chronic photothrombosis stroke model

      Correlation of optical attenuation coefficient estimated using optical coherence tomography with changes in astrocytes and neurons in a chronic photothrombosis stroke model

      The optical attenuation coefficient (OAC) estimated using optical coherence tomography (OAC-OCT) offers a label-free 3D mapping of tissue infarction, but the physiological origin of the OAC contrast remains unclear. For effectively suppressing OAC fluctuations, we propose a hybrid (wavelength/angle) division multiplexing (HDM) method, which improved the OAC contrast by 70.7% in tissue phantoms. To test the feasibility of OAC-based infarction detection, triphenyltetrazolium chloride (TTC) staining was performed on fresh ex vivo brain slices, and the TTC-defined infarction was used as the ground truth. Sharp OAC contrast was observed between the TTC-defined infarction (1.09 mm −1 ) and normal ...

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    8. Absolute linear-in-k spectrometer designs enabled by freeform optics

      Absolute linear-in-k spectrometer designs enabled by freeform optics

      Linear-in-wavenumber, k , spectrometers have the merits of saving signal processing time and improving the sensitivity of spectral-domain optical coherence tomography (SD-OCT) by avoiding post- k -interpolation. We report on an approach leveraging freeform optics to linearize spectrometers in k to achieve an extremely low residual k -nonlinearity in design. A freeform lens reduced the k -nonlinearity from 2.47% for a benchmark spectrometer to 2.79 × 10 −5 % and 3.36 × 10 −9 % using the Fringe Zernike coefficients up to the 16 th term and 37 th term, respectively. A simulation model was developed to evaluate the performance of SD-OCT ...

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    9. Deep learning-based automated detection of retinal diseases using optical coherence tomography images

      Deep learning-based automated detection of retinal diseases using optical coherence tomography images

      Retinal disease classification is a significant problem in computer-aided diagnosis (CAD) for medical applications. This paper is focused on a 4-class classification problem to automatically detect choroidal neovascularization (CNV), diabetic macular edema (DME), DRUSEN, and NORMAL in optical coherence tomography (OCT) images. The proposed classification algorithm adopted an ensemble of four classification model instances to identify retinal OCT images, each of which was based on an improved residual neural network (ResNet50). The experiment followed a patient-level 10-fold cross-validation process, on development retinal OCT image dataset. The proposed approach achieved 0.973 (95% confidence interval [CI], 0.971–0.975) classification ...

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    10. Optical coherence tomography through a rigid borescope applied to quantification of articular cartilage thickness in a porcine knee model

      Optical coherence tomography through a rigid borescope applied to quantification of articular cartilage thickness in a porcine knee model

      There exists an unmet need for an optical coherence tomography (OCT) delivery scheme that is simple, robust, and applicable to general surgical applications. To deliver the beam in a narrow form factor, optical borescopes present an attractive potential solution. We present a method for enabling endoscopic delivery of OCT using a handheld rigid borescope adapted to a low-cost OCT engine. The system reduces the distal profile of the scanner, enabling application of the system in otherwise hard-to-access regions. The clinical potential of this design is demonstrated through real-time quantification of articular cartilage thickness, a primary biomarker of joint health during ...

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    11. Spatial coordinate corrected motion tracking for optical coherence elastography

      Spatial coordinate corrected motion tracking for optical coherence elastography

      We investigate a spatial coordinate correction (SCC) method to track motion with high accuracy for optical coherence elastography (OCE). Through SCC, we refer the displacement field tracked by optical coherence tomography (OCT) in the loaded sample to individual material points defined in a fixed coordinate system. SCC allows OCE to perform spatially and temporally unambiguous tracking of displacement and enables accurate mechanical characterization of biological tissue for cancer diagnosis and tumor margin assessment. In this study, we validated the effectiveness of motion tracking based on SCC using experimental OCE data obtained from ex vivo human breast tissues.

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    12. Improved description of the signal formation in grating generated-optical coherence tomography

      Improved description of the signal formation in grating generated-optical coherence tomography

      Several optical instruments have been presented over recent years that use a tilted diffraction grating in the reference arm, describing its effect as introducing a continuous optical delay in the direction of the grating dispersion. Having examined these types of system carefully, we believe this description does not fully capture the manner by which the signal is formed in these instruments, and present here a simple model that clearly demonstrates the essential elements behind the way such systems operate. This analysis not only illustrates the reason for signals of the form seen being generated, but also shows how great care ...

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    13. Optical coherence tomography for in vivo imaging of endocardial to mesenchymal transition during avian heart development

      Optical coherence tomography for in vivo imaging of endocardial to mesenchymal transition during avian heart development

      The endocardial to mesenchymal transition (EndMT) that occurs in endocardial cushions during heart development is critical for proper heart septation and formation of the heart’s valves. In EndMT, cells delaminate from the endocardium and migrate into the previously acellular endocardial cushions. Optical coherence tomography (OCT) imaging uses the optical properties of tissues for contrast, and during early development OCT can differentiate cellular versus acellular tissues. Here we show that OCT can be used to non-invasively track EndMT progression in vivo in the outflow tract cushions of chicken embryos. This enables in vivo studies to elucidate factors leading to cardiac ...

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    14. Computational-imaging-based optical coherence tomography in time- and frequency-domain

      Computational-imaging-based optical coherence tomography in time- and frequency-domain

      A computational 3D imaging system is developed that enables polychromatic, depth-resolved, diffraction-limited imaging of semi-transparent objects. By combining coherent diffractive imaging (CDI) and optical coherence tomography (OCT), we reconstruct tomographic images of 3D objects from a set of wavelength- and phase-resolved diffraction patterns, using numerical methods to achieve image quality beyond the hardware limits of the optical systems used. We implement both time- and frequency-domain versions of full-field OCT systems, and for both versions we demonstrate fully lensless, as well as high-numerical-aperture configurations. We provide a comparison and overview of these different practical approaches to depth-resolved computational imaging. Furthermore, we ...

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    15. Noise and sensitivity in optical coherence tomography based vibrometry

      Noise and sensitivity in optical coherence tomography based vibrometry

      There is growing interest in using the exquisite phase sensitivity of optical coherence tomography (OCT) to measure the vibratory response in organ systems such as the middle and inner ear. Using frequency domain analysis, it is possible to achieve picometer sensitivity to vibration over a wide frequency band. Here we explore the limits of the frequency domain vibratory sensitivity due to additive noise and consider the implication of phase noise statistics on the estimation of vibratory amplitude and phase. Noise statistics are derived in both the Rayleigh ( s/n = 0 ) and Normal distribution ( s/n > 3 ) limits. These theoretical findings ...

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    16. Modeling of full-field optical coherence tomography in scattering media

      Modeling of full-field optical coherence tomography in scattering media

      We develop a model of full-field optical coherence tomography (FF-OCT) that includes a description of partial temporal and spatial coherence, together with a mean-field scattering theory going beyond the Born approximation. Based on explicit expressions of the FF-OCT signal, we discuss essential features of FF-OCT imaging, such as the influence of partial coherence on the optical transfer function, and on the decay of the signal with depth. We derive the conditions under which the spatially averaged signal exhibits a pure exponential decay, providing a clear frame for the use of the Beer–Lambert law for quantitative measurements of the extinction ...

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      Mentions: ESPCI ParisTech
    17. Deep learning based noise reduction method for automatic 3D segmentation of the anterior of lamina cribrosa in optical coherence tomography volumetric scans

      Deep learning based noise reduction method for automatic 3D segmentation of the anterior of lamina cribrosa in optical coherence tomography volumetric scans

      A deep-learning (DL) based noise reduction algorithm, in combination with a vessel shadow compensation method and a three-dimensional (3D) segmentation technique, has been developed to achieve, to the authors best knowledge, the first automatic segmentation of the anterior surface of the lamina cribrosa (LC) in volumetric ophthalmic optical coherence tomography (OCT) scans. The present DL-based OCT noise reduction algorithm was trained without the need of noise-free ground truth images by utilizing the latest development in deep learning of de-noising from single noisy images, and was demonstrated to be able to cover more locations in the retina and disease cases of ...

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    18. Ultrahigh-resolution optical coherence tomography/angiography with an economic and compact supercontinuum laser

      Ultrahigh-resolution optical coherence tomography/angiography with an economic and compact supercontinuum laser

      In this study, a Q-switch pumped supercontinuum laser (QS-SCL) is used as a light source for in vivo imaging via ultrahigh-resolution optical coherence tomography and angiography (UHR-OCT/OCTA). For this purpose, an OCT system based on a spectral-domain detection scheme is constructed, and a spectrometer with a spectral range of 635 − 875 nm is designed. The effective full-width at half maximum of spectrum covers 150 nm, and the corresponding axial and transverse resolutions are 2 and 10 µm in air, respectively. The relative intensity noise of the QS-SCL and mode-locked SCL is quantitatively compared. Furthermore, a special processing algorithm is ...

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    19. Electrically tunable lens integrated with optical coherence tomography angiography for cerebral blood flow imaging in deep cortical layers in mice

      Electrically tunable lens integrated with optical coherence tomography angiography for cerebral blood flow imaging in deep cortical layers in mice

      We report the use of an electrically tunable lens (ETL) in a 1.3 μm spectral-domain optical coherence tomography (SD-OCT) system to overcome the depth of focus (DOF) limitation in conventional OCT systems for OCT angiography (OCTA) in a mouse cerebral cortex. The ETL provides fast and dynamic control of the axial focus of the probe beam along the entire range of the mouse cortex, upon which we performed cerebral blood flow imaging of all cortical layers by stitching the OCTA images automatically captured at six focal depths. Capillary vasculature and axial blood flow velocity were revealed in distinctive cortical ...

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    20. Metasurface-based focus-tunable mirror

      Metasurface-based focus-tunable mirror

      Varifocal mirrors, which have various applications in optical coherent tomography and three-dimensional displays, are traditionally based on the fluid pressure or mechanical pusher to deform the mirror. The limitations of conventional varifocal mirrors are obvious, such as the heavy size of the device and constraints of tunability, due to their mechanical pressure control elements. The reprogrammable metasurface, a new flat photonic device with multifunction in an ultrathin dimension, paves the way towards an ultrathin and lightweight mirror with precise phase profile. Here, an active reconfigurable metasurface is proposed to achieve the manipulation of the wavefront. The meta-atom in the metasurface ...

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    21. Retina phantom for the evaluation of optical coherence tomography angiography based on microfluidic channels

      Retina phantom for the evaluation of optical coherence tomography angiography based on microfluidic channels

      Optical coherence tomography (OCT) angiography (OCTA) has been actively studied as a noninvasive imaging technology to generate retinal blood vessel network maps for the diagnoses of retinal diseases. Given that the uses of OCT and OCTA have increased in the field of ophthalmology, it is necessary to develop retinal phantoms for clinical OCT for product development, performance evaluation, calibration, certification, medical device licensing, and production processes. We developed a retinal layer-mimicking phantom with microfluidic channels based on microfluidic fabrication technology using polydimethylsiloxane (PDMS) and titanium dioxide (TiO 2 ) powder. We implemented superficial and deep retinal vessels using microfluidic channels. In ...

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      Mentions: Sang-Won Lee
    22. Co-cultured microfluidic model of the airway optimized for microscopy and micro-optical coherence tomography imaging

      Co-cultured microfluidic model of the airway optimized for microscopy and micro-optical coherence tomography imaging

      We have developed a human bronchial epithelial (HBE) cell and endothelial cell co-cultured microfluidic model to mimic the in vivo human airway. This airway-on-a-chip was designed with a central epithelial channel and two flanking endothelial channels, with a three-dimensional monolayers of cells growing along the four walls of the channel, forming central clear lumens. These cultures mimic airways and microvasculature in vivo . The central channel cells are grown at air-liquid interface and show features of airway differentiation including tight-junction formation, mucus production, and ciliated cells. Combined with novel micro-optical coherence tomography, this chip enables functional imaging of the interior of ...

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    23. Optical coherence tomography velocimetry based on decorrelation estimation of phasor pair ratios (DEPPAIR)

      Optical coherence tomography velocimetry based on decorrelation estimation of phasor pair ratios (DEPPAIR)

      Quantitative velocity estimations in optical coherence tomography requires the estimation of the axial and lateral flow components. Optical coherence tomography measures the depth resolved complex field reflected from a sample. While the axial velocity component can be determined from the Doppler shift or phase shift between a pair of consecutive measurements at the same location, the estimation of the lateral component for in vivo applications is still challenging. One approach to determine lateral velocity is multiple simultaneous measurements at different angles. In another approach the lateral component can be retrieved through repeated measurements at (nearly) the same location by an ...

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    24. Automated accurate lumen segmentation using L-mode interpolation for three-dimensional intravascular optical coherence tomography

      Automated accurate lumen segmentation using L-mode interpolation for three-dimensional intravascular optical coherence tomography

      Intravascular optical coherence tomography (IVOCT) lumen-based computational flow dynamics (CFD) enables physiologic evaluations such as of the fractional flow reserve (FFR) and wall sheer stress. In this study, we developed an accurate, time-efficient method for extracting lumen contours of the coronary artery. The contours of cross-sectional images containing wide intimal discontinuities due to guide wire shadowing and large bifurcations were delineated by utilizing the natural longitudinal lumen continuity of the arteries. Our algorithm was applied to 5931 pre-intervention OCT images acquired from 40 patients. For a quantitative comparison, the images were also processed through manual segmentation (the reference standard) and ...

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    1-24 of 662 1 2 3 4 ... 26 27 28 »
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