1. 1-24 of 750 1 2 3 4 ... 30 31 32 »
    1. Methylene blue-filled biodegradable polymer particles as a contrast agent for optical coherence tomography

      Methylene blue-filled biodegradable polymer particles as a contrast agent for optical coherence tomography

      Optical coherence tomography (OCT) images largely lack molecular information or molecular contrast. We address that issue here, reporting on the development of biodegradable micro and nano-spheres loaded with methylene blue (MB) as molecular contrast agents for OCT. MB is a constituent of FDA approved therapies and widely used as a dye in off-label clinical applications. The sequestration of MB within the polymer reduced toxicity and improved signal strength by drastically reducing the production of singlet oxygen and leuco-MB. The former leads to tissue damage and the latter to reduced image contrast. The spheres are also strongly scattering which improves molecular ...

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    2. Optical coherence tomography for thyroid pathology: 3D analysis of tissue microstructure

      Optical coherence tomography for thyroid pathology: 3D analysis of tissue microstructure

      To investigate the potential of optical coherence tomography (OCT) to distinguish between normal and pathologic thyroid tissue, 3D OCT images were acquired on ex vivo thyroid samples from adult subjects (n=22) diagnosed with a variety of pathologies. The follicular structure was analyzed in terms of count, size, density and sphericity. Results showed that OCT images highly agreed with the corresponding histopatology and the calculated parameters were representative of the follicular structure variation. The analysis of OCT volumes provides quantitative information that could make automatic classification possible. Thus, OCT can be beneficial for intraoperative surgical guidance or in the pathology ...

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    3. Frequency-doubled FDML-MOPA laser in the visible

      Frequency-doubled FDML-MOPA laser in the visible

      Wavelength-swept lasers enable high-speed measurements in absorption spectroscopy, Raman spectroscopy, nonlinear Raman hyperspectral microscopy, rapid confocal microscopy, short impulse generation, and most importantly for high-speed optical coherence tomography, with speeds up to video-rate volumetric imaging. Recently, we introduced a pulsed wavelength-swept laser based on the Fourier domain mode-locked (FDML) laser principle combined with a master-oscillator power amplifier (MOPA) architecture. The high peak powers reached with this laser enabled rapid two-photon microscopy and two-photon fluorescence lifetime microscopy and high-speed light detection and ranging measurements. Here, we present the extension of this laser into the visible wavelength range by frequency doubling the ...

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    4. Visible light optical coherence tomography angiography (vis-OCTA) facilitates local microvascular oximetry in the human retina

      Visible light optical coherence tomography angiography (vis-OCTA) facilitates local microvascular oximetry in the human retina

      We report herein the first visible light optical coherence tomography angiography (vis-OCTA) for human retinal imaging. Compared to the existing vis-OCT systems, we devised a spectrometer with a narrower bandwidth to increase the spectral power density for OCTA imaging, while retaining the major spectral contrast in the blood. We achieved a 100 kHz A-line rate, the fastest acquisition speed reported so far for human retinal vis-OCT. We rigorously optimized the imaging protocol such that a single acquisition took < 6 seconds with a field of view (FOV) of 3×7.8 mm 2 . The angiography enables accurate localization of microvasculature down ...

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    5. Study of low-peak-power highly coherent broadband supercontinuum generation through a dispersion-engineered Si-rich silicon nitride waveguide

      Study of low-peak-power highly coherent broadband supercontinuum generation through a dispersion-engineered Si-rich silicon nitride waveguide

      Since the first observation by Alfano and Shapiro in the 1970s [Phys. Rev. Lett. 24 , 584 (1970) [ CrossRef ] ], supercontinuum generation study has become an attractive research area in the field of broadband light source design, including its use in various applications associated with nonlinear optics in recent years. In this work, the numerical demonstration of ultrabroadband supercontinuum generation in the mid-infrared (MIR) region via the use of complementary metal-oxide semiconductor compatible Si-rich silicon nitride as the core in a planar waveguide design employing one of two materials, either L i N b O 3 LiNbO3 or M g F 2 ...

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    6. Sensorless adaptive-optics optical coherence tomographic angiography

      Sensorless adaptive-optics optical coherence tomographic angiography

      Optical coherence tomographic angiography (OCTA) can image the retinal blood flow but visualization of the capillary caliber is limited by the low lateral resolution. Adaptive optics (AO) can be used to compensate ocular aberrations when using high numerical aperture (NA), and thus improve image resolution. However, previously reported AO-OCTA instruments were large and complex, and have a small sub-millimeter field of view (FOV) that hinders the extraction of biomarkers with clinical relevance. In this manuscript, we developed a sensorless AO-OCTA prototype with an intermediate numerical aperture to produce depth-resolved angiograms with high resolution and signal-to-noise ratio over a 2 × 2 ...

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    7. Cascade optical coherence tomography (C-OCT)

      Cascade optical coherence tomography (C-OCT)

      Significant advances for optical systems in terms of both performance and packaging are enabled by freeform optical components. Yet, surface form metrology for freeform optics remains a challenge. We developed and investigated a point-cloud cascade optical coherence tomography (C-OCT) technique to address this metrology challenge. The mathematical framework for the working principle of C-OCT is presented. A novel detection scheme is developed to enable high-speed measurements. Experimental results validate the C-OCT technique with the prototype setup demonstrating single-point precision of ±26 nm (∼λ/24 at the He-Ne wavelength), paving the way towards full surface measurements on freeform optical components.

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    8. Optical coherence tomography with balanced signal strength across the depth for pearl inspection

      Optical coherence tomography with balanced signal strength across the depth for pearl inspection

      Optical coherence tomography (OCT) relies on the reflection of light from structures in different layers to interferometrically reconstruct the volumetric image of the sample. However, light returned from multiple layers suffers from imbalanced attenuation owing to the optical path difference and inhomogeneous tissue absorption. We report an optimization algorithm to improve signal strength in deep tissue for swept-source (SS)-OCT imaging. This algorithm utilizes the attenuation coefficient of consecutive layers within the sample and combines them to compensate for the signal intensity loss from deep tissue. We stacked 170-µm thick cover slides as a standard sample for benchmark testing ...

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    9. Detection and compensation of dispersion mismatch for frequency-domain optical coherence tomography based on A-scan’s spectrogram

      Detection and compensation of dispersion mismatch for frequency-domain optical coherence tomography based on A-scan’s spectrogram

      Balanced dispersion between reference and sample arms is critical in frequency-domain optical coherence tomography (FD-OCT) to perform imaging with the optimal axial resolution, and the spectroscopic analysis of each voxel in FD-OCT can provide the metric of the spectrogram. Here we revisited dispersion mismatch in the spectrogram view using the spectroscopic analysis of voxels in FD-OCT and uncovered that the dispersion mismatch disturbs the A-scan’s spectrogram and reshapes the depth-resolved spectra in the spectrogram. Based on this spectroscopic effect of dispersion mismatch on A-scan’s spectrogram, we proposed a numerical method to detect dispersion mismatch and perform dispersion compensation ...

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    10. Estimation and compensation of phase errors induced by axial bulk motion of a sample in wavelength-sweeping parallel Fourier domain OCT

      Estimation and compensation of phase errors induced by axial bulk motion of a sample in wavelength-sweeping parallel Fourier domain OCT

      We report a new, to the best of our knowledge, approach to correct image blurring due to the axial bulk motion of a sample in wavelength-sweeping Fourier domain parallel optical coherence tomography (OCT). This approach can estimate phase errors changing rapidly in time through direct measurements of the apparent axial shift during the sampling interval using common phase changes in parallel detection without additional hardware. To demonstrate the performance of the proposed algorithm, a single reflection and scattering sample were imaged with wavelength-sweeping parallel OCT implemented by scanning a spectrally dispersed line-field along the line direction. In addition, we quantitatively ...

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      Mentions: Kye-Sung Lee
    11. Optical coherence tomography and fluorescence microscopy dual-modality imaging for in vivo single-cell tracking with nanowire lasers

      Optical coherence tomography and fluorescence microscopy dual-modality imaging for in vivo single-cell tracking with nanowire lasers

      Emerging cell-based therapies such as stem cell therapy and immunotherapy have attracted broad attention in both biological research and clinical practice. However, a long-standing technical gap of cell-based therapies is the difficulty of directly assessing treatment efficacy via tracking therapeutically administered cells. Therefore, imaging techniques to follow the in vivo distribution and migration of cells are greatly needed. Optical coherence tomography (OCT) is a clinically available imaging technology with ultrahigh-resolution and excellent imaging depth. It also shows great potential for in vivo cellular imaging. However, due to the homogeneity of current OCT cell labeling contrast agents (such as gold and ...

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    12. Noise reduction in supercontinuum sources for OCT by single-pulse spectral normalization

      Noise reduction in supercontinuum sources for OCT by single-pulse spectral normalization

      Supercontinuum (SC) sources offer high illumination power from a single-mode fiber with large spectral bandwidth including the visible spectrum, which is a growing application area for optical coherence tomography (OCT). However, SC spectra suffer from pulse-to-pulse variations, increasing noise in the resulting images. By simultaneously collecting a normalization spectrum, OCT image noise can be reduced by more than half (7 dB) for single pulses without any pulse averaging using only simple optical components.

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    13. Stepped frequency comb generation based on electro-optic phase-code mode-locking for moderate-speed circular-ranging OCT

      Stepped frequency comb generation based on electro-optic phase-code mode-locking for moderate-speed circular-ranging OCT

      Circular-ranging (CR) optical coherence tomography (OCT) uses frequency comb sources to improve long-range imaging. While the initial development of CR-OCT focused on extremely high-speed imaging (i.e., operation at A-line rates of several to tens of MHz), there are many applications and imaging strategies for which more moderate speeds are preferred. However, we lack suitable frequency comb sources to enable moderate speed CR-OCT imaging. Here, we describe a novel phase-code mode-locking (PCML) laser architecture that can be operated from the kilohertz to megahertz range, while also offering novel features such as dynamic re-configurability and simplified linear-in-time frequency stepping. We demonstrate ...

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    14. Optical coherence tomography angiography to evaluate murine fetal brain vasculature changes caused by prenatal exposure to nicotine

      Optical coherence tomography angiography to evaluate murine fetal brain vasculature changes caused by prenatal exposure to nicotine

      Maternal smoking causes several defects ranging from intrauterine growth restriction to sudden infant death syndrome and spontaneous abortion. While several studies have documented the effects of prenatal nicotine exposure in development and behavior, acute vasculature changes in the fetal brain due to prenatal nicotine exposure have not been evaluated yet. This study uses correlation mapping optical coherence angiography to evaluate changes in fetal brain vasculature flow caused by maternal exposure to nicotine during the second trimester-equivalent of gestation in a mouse model. The effects of two different doses of nicotine were evaluated. Results showed a decrease in the vasculature for ...

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    15. Effect of image artefacts on phase conjugation with spectral domain optical coherence tomography

      Effect of image artefacts on phase conjugation with spectral domain optical coherence tomography

      Recently the acquisition of the time-resolved reflection matrix was demonstrated based on spectral domain optical coherence tomography. In principle, the matrix describes the linear dependence of the OCT signal received from different depths on the field which is incident to the scattering sample. Knowledge of the matrix, hence, enables beam shaping to selectively enhance the received signal, for example to increase the penetration depth when imaging turbid media. We investigate the impact of image artefacts on the approach. Phase conjugation is shown to enhance the OCT signal, but not autocorrelation and mirror artefacts. Imaging applications are demonstrated indicating the potential ...

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    16. Registration of fluorescein angiography and optical coherence tomography images of curved retina via scanning laser ophthalmoscopy photographs

      Registration of fluorescein angiography and optical coherence tomography images of curved retina via scanning laser ophthalmoscopy photographs

      Accurate and automatic registration of multimodal retinal images such as fluorescein angiography (FA) and optical coherence tomography (OCT) enables utilization of supplementary information. FA is a gold standard imaging modality that depicts neurovascular structure of retina and is used for diagnosing neurovascular-related diseases such as diabetic retinopathy (DR). Unlike FA, OCT is non-invasive retinal imaging modality that provides cross-sectional data of retina. Due to differences in contrast, resolution and brightness of multimodal retinal images, the images resulted from vessel extraction of image pairs are not exactly the same. Also, prevalent feature detection, extraction and matching schemes do not result in ...

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    17. Deep iterative vessel segmentation in OCT angiography

      Deep iterative vessel segmentation in OCT angiography

      This paper addresses retinal vessel segmentation on optical coherence tomography angiography (OCT-A) images of the human retina. Our approach is motivated by the need for high precision image-guided delivery of regenerative therapies in vitreo-retinal surgery. OCT-A visualizes macular vasculature, the main landmark of the surgically targeted area, at a level of detail and spatial extent unattainable by other imaging modalities. Thus, automatic extraction of detailed vessel maps can ultimately inform surgical planning. We address the task of delineation of the Superficial Vascular Plexus in 2D Maximum Intensity Projections (MIP) of OCT-A using convolutional neural networks that iteratively refine the quality ...

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    18. Ultra-high-resolution SD-OCM imaging with a compact polarization-aligned 840 nm broadband combined-SLED source

      Ultra-high-resolution SD-OCM imaging with a compact polarization-aligned 840 nm broadband combined-SLED source

      We analyze the influence of intrinsic polarization alignment on image quality and axial resolution employing a broadband 840 nm light source with an optical bandwidth of 160 nm and an output power of 12 mW tailored for spectral-domain optical coherence microscopy (SD-OCM) applications. Three superluminescent diodes (SLEDs) are integrated into a 14-pin butterfly module using a free-space micro-optical bench architecture, maintaining a constant polarization state across the full spectral output. We demonstrate superior imaging performance in comparison to traditionally coupled-SLED broadband light sources in a teleost model organism in-vivo .

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    19. Supercontinuum generation in a chalcogenide all-solid hybrid microstructured optical fiber

      Supercontinuum generation in a chalcogenide all-solid hybrid microstructured optical fiber

      We report the fabrication of a chalcogenide all-solid hybrid microstructured optical fiber and its application in supercontinuum generation for the first time, to the best of our knowledge. The fiber possesses all-normal and flattened chromatic dispersion, making it highly potential for broad and coherent supercontinuum generation. By pumping the fiber with a femtosecond laser at 3, 4, and 5 µm, broad supercontinua with good spectral flatness are generated. The broadest SC spectrum extending from 2.2 to 10 µm at -20 dB level was obtained when the fiber was pumped at 5 µm with an input power of 3.9 ...

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    20. Penetration capability of near infrared Laguerre–Gaussian beams through highly scattering media

      Penetration capability of near infrared Laguerre–Gaussian beams through highly scattering media

      The higher capability of optical vortex beams of penetrating turbid media (e.g., biological fluids) with respect to the conventional Gaussian beams is, for the first time to our knowledge, demonstrated in the 1.3 µm wavelength range which is conventionally used for optical coherence tomography procedures in endoscopic intravascular scenarios. The effect has been demonstrated by performing transmittance measurements through suspensions of polystyrene microspheres in water with various particulate concentrations and, in reflection, by using samples of human blood with different thicknesses. The reduced backscattering/increased transmittance into such highly scattering media of Laguerre–Gaussian beams with respect to ...

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    21. Automatic stent reconstruction in optical coherence tomography based on a deep convolutional model

      Automatic stent reconstruction in optical coherence tomography based on a deep convolutional model

      Intravascular optical coherence tomography (IVOCT) can accurately assess stent apposition and expansion, thus enabling the optimisation of a stenting procedure to minimize the risk of device failure. This paper presents a deep convolutional based model for automatic detection and segmentation of stent struts. The input of pseudo-3D images aggregated the information from adjacent frames to refine the probability of strut detection. In addition, multi-scale shortcut connections were implemented to minimize the loss of spatial resolution and refine the segmentation of strut contours. After training, the model was independently tested in 21,363 cross-sectional images from 170 IVOCT image pullbacks. The ...

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    22. Tracking the invasion of breast cancer cells in paper-based 3D cultures by OCT motility analysis

      Tracking the invasion of breast cancer cells in paper-based 3D cultures by OCT motility analysis

      3D paper-based cultures (PBCs) are easy-to-use and provide a biologically representative microenvironment. By stacking a sheet of cell-laden paper below sheets containing cell-free hydrogel, we form an assay capable of segmenting cells by the distance they invaded from the original cell-seeded layer. These invasion assays are limited to end-point analyses with fluorescence-based readouts due to the highly scattering nature of the paper scaffolds. Here we demonstrate that optical coherence tomography (OCT) can distinguish living cells from the surrounding extracellular matrix (ECM) or paper fibers based upon their intracellular motility amplitude ( M ). M is computed from fluctuation statistics of the sample ...

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    23. Spectral 3D reconstruction of impressionist oil paintings based on macroscopic OCT imaging

      Spectral 3D reconstruction of impressionist oil paintings based on macroscopic OCT imaging

      Art conservators have adopted optical technologies to improve conservation efforts; laser triangulation, stereophotogrammetry, structured light, laser scanners, and time of flight sensors have been deployed to capture the 3D information of sculptures and architectures. Optical coherence tomography (OCT) has introduced new imaging methods to study the surface features and subsurface structures of delicate cultural heritage objects. However, the field of view of OCT severely limits the scanning area. We present a hybrid scanning platform combined with an effective algorithm for real-time sampling and artifact removal to achieve macroscopic OCT (macro-OCT) imaging and spectral 3D reconstruction of impressionist style oil paintings.

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      Mentions: Yi Yang
    24. In vivo imaging of the human cornea with high-speed and high-resolution Fourier-domain full-field optical coherence tomography

      In vivo imaging of the human cornea with high-speed and high-resolution Fourier-domain full-field optical coherence tomography

      Corneal evaluation in ophthalmology necessitates cellular-resolution and fast imaging techniques that allow for accurate diagnoses. Currently, the fastest volumetric imaging technique is Fourier-domain full-field optical coherence tomography (FD-FF-OCT), which uses a fast camera and a rapidly tunable laser source. Here, we demonstrate high-resolution, high-speed, non-contact corneal volumetric imaging in vivo with FD-FF-OCT that can acquire a single 3D volume with a voxel rate of 7.8 GHz. The spatial coherence of the laser source was suppressed to prevent it from focusing on a spot on the retina, and therefore, exceeding the maximum permissible exposure (MPE). The inherently volumetric nature of ...

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    1-24 of 750 1 2 3 4 ... 30 31 32 »
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