1. 1-24 of 709 1 2 3 4 ... 28 29 30 »
    1. Spectroscopic optical coherence refraction tomography

      Spectroscopic optical coherence refraction tomography

      In optical coherence tomography (OCT), the axial resolution is often superior to the lateral resolution, which is sacrificed for long imaging depths. To address this anisotropy, we previously developed optical coherence refraction tomography (OCRT), which uses images from multiple angles to computationally reconstruct an image with isotropic resolution, given by the OCT axial resolution. On the other hand, spectroscopic OCT (SOCT), an extension of OCT, trades axial resolution for spectral resolution and hence often has superior lateral resolution. Here, we present spectroscopic OCRT (SOCRT), which uses SOCT images from multiple angles to reconstruct a spectroscopic image with isotropic spatial resolution ...

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    2. Imaging retinal structures at cellular-level resolution by visible-light optical coherence tomography

      Imaging retinal structures at cellular-level resolution by visible-light optical coherence tomography

      In vivo high-resolution images are the most direct way to understand retinal function and diseases. Here we report the use of visible-light optical coherence tomography with volumetric registration and averaging to achieve cellular-level retinal structural imaging in a rat eye, covering the entire depth of the retina. Vitreous fibers, nerve fiber bundles, and vasculature were clearly revealed, as well as at least three laminar sublayers in the inner plexiform layer. We also successfully visualized ganglion cell somas in the ganglion cell layer, cells in the inner nuclear layer, and photoreceptors in the outer nuclear layer and ellipsoid zone. This technique ...

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    3. Self-aligned micro-optic integrated photonic platform

      Self-aligned micro-optic integrated photonic platform

      In this work, we present the fabrication technology of a monolithically integrated photonic platform combining key components for optical coherence tomography (OCT) imaging, thereby including a photonic interferometer, a collimating lens, and a 45° reflecting mirror that directs the light from the interferometer to the collimator. The proposed integration process simplifies the fabrication of an interferometric system and inherently overcomes the complexity of costly alignment procedures while complying with the necessarily stringent optical constraints. Fabricated waveguide characterization shows total optical losses as low as 3 dB, and less than 1 dB of additional loss due to the Si 45° mirror ...

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    4. Real-time Lissajous imaging with a low-voltage 2-axis MEMS scanner based on electrothermal actuation

      Real-time Lissajous imaging with a low-voltage 2-axis MEMS scanner based on electrothermal actuation

      Laser scanning based on Micro-Electro-Mechanical Systems (MEMS) scanners has become very attractive for biomedical endoscopic imaging, such as confocal microscopy or Optical Coherence Tomography (OCT). These scanners are required to be fast to achieve real-time image reconstruction while working at low actuation voltage to comply with medical standards. In this context, we report a 2-axis Micro-Electro-Mechanical Systems (MEMS) electrothermal micro-scannercapable of imaging large fields of view at high frame rates, e.g. from 10 to 80 frames per second. For this purpose, Lissajous scan parameters are chosen to provide the optimal image quality within the scanner capabilities and the sampling ...

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    5. Optically computed optical coherence tomography for volumetric imaging

      Optically computed optical coherence tomography for volumetric imaging

      We describe an innovative optically computed optical coherence tomography (OC-OCT) technology. The OC-OCT system performs depth resolved imaging by computing the Fourier transform of the interferometric spectra optically. The OC-OCT system modulates the interferometric spectra with Fourier basis function projected to a spatial light modulator and detects the modulated signal without spectral discrimination. The novel, to the best of our knowledge, optical computation strategy enables volumetric OCT imaging without performing mechanical scanning and without the need for Fourier transform in a computer.

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      Mentions: Xuan Liu
    6. Functional optical coherence tomography and photoacoustic microscopy imaging for zebrafish larvae

      Functional optical coherence tomography and photoacoustic microscopy imaging for zebrafish larvae

      We present a dual modality functional optical coherence tomography and photoacoustic microscopy (OCT-PAM) system. The photoacoustic modality employs an akinetic optical sensor with a large imaging window. This imaging window enables direct reflection mode operation, and a seamless integration of optical coherence tomography (OCT) as a second imaging modality. Functional extensions to the OCT-PAM system include Doppler OCT (DOCT) and spectroscopic PAM (sPAM). This functional and non-invasive imaging system is applied to image zebrafish larvae, demonstrating its capability to extract both morphological and hemodynamic parameters in vivo in small animals, which are essential and critical in preclinical imaging for physiological ...

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    7. Three-dimensional visualization of opacifications in the murine crystalline lens by in vivo optical coherence tomography

      Three-dimensional visualization of opacifications in the murine crystalline lens by in vivo optical coherence tomography

      Diagnostic classification techniques used to diagnose cataracts, the world’s leading cause of blindness, are currently based on subjective methods. Here, we present optical coherence tomography as a noninvasive tool for volumetric visualization of lesions formed in the crystalline lens. A custom-made swept-source optical coherence tomography (SS-OCT) system was utilized to investigate the murine crystalline lens. In addition to imaging cataractous lesions in aged wildtype mice, we studied the structure and shape of cataracts in a mouse model of Alzheimer’s disease. Hyperscattering opacifications in the crystalline lens were observed in both groups. Post mortem histological analysis were performed to ...

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    8. Multimodal quantitative optical elastography of the crystalline lens with optical coherence elastography and Brillouin microscopy

      Multimodal quantitative optical elastography of the crystalline lens with optical coherence elastography and Brillouin microscopy

      Assessing the biomechanical properties of the crystalline lens can provide crucial information for diagnosing disease and guiding precision therapeutic interventions. Existing noninvasive methods have been limited to global measurements. Here, we demonstrate the quantitative assessment of the elasticity of crystalline lens with a multimodal optical elastography technique, which combines dynamic wave-based optical coherence elastography (OCE) and Brillouin microscopy to overcome the drawbacks of individual modalities. OCE can provide direct measurements of tissue elasticity rapidly and quantitatively, but it is a challenge to image transparent samples such as the lens because this technique relies on backscattered light. On the other hand ...

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    9. Noise and bias in optical coherence tomography intensity signal decorrelation

      Noise and bias in optical coherence tomography intensity signal decorrelation

      Functional optical coherence tomography (OCT) imaging based on the decorrelation of the intensity signal has been used extensively in angiography and is finding use in flowmetry and therapy monitoring. In this work, we present a rigorous analysis of the autocorrelation function, introduce the concepts of contrast bias, statistical bias and variability, and identify the optimal definition of the second-order autocorrelation function (ACF) g (2) to improve its estimation from limited data. We benchmark different averaging strategies in reducing statistical bias and variability. We also developed an analytical correction for the noise contributions to the decorrelation of the ACF in OCT ...

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    10. Platform for quantitative multiscale imaging of tissue composition

      Platform for quantitative multiscale imaging of tissue composition

      Changes in the multi-level physical structure of biological features going from cellular to tissue level composition is a key factor in many major diseases. However, we are only beginning to understand the role of these structural changes because there are few dedicated multiscale imaging platforms with sensitivity at both the cellular and macrostructural spatial scale. A single platform reduces bias and complications from multiple sample preparation methods and can ease image registration. In order to address these needs, we have developed a multiscale imaging system using a range of imaging modalities sensitive to tissue composition: Ultrasound, Second Harmonic Generation Microscopy ...

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    11. Forward multiple scattering dominates speckle decorrelation in whole-blood flowmetry using optical coherence tomography

      Forward multiple scattering dominates speckle decorrelation in whole-blood flowmetry using optical coherence tomography

      Quantitative blood flow measurements using optical coherence tomography (OCT) have a wide potential range of medical research and clinical applications. Flowmetry based on the temporal dynamics of the OCT signal may have the ability to measure three-dimensional flow profiles regardless of the flow direction. State-of-the-art models describing the OCT signal temporal statistics are based on dynamic light scattering (DLS), a model which is inherently limited to single scattering regimes. DLS methods continue to be applied to OCT despite the knowledge that red blood cells produce strong forward multiple scattering. Here, we postulate that forward multiple scattering is the primary mechanism ...

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    12. Phase unwrapping based on a residual en-decoder network for phase images in Fourier domain Doppler optical coherence tomography

      Phase unwrapping based on a residual en-decoder network for phase images in Fourier domain Doppler optical coherence tomography

      To solve the phase unwrapping problem for phase images in Fourier domain Doppler optical coherence tomography (DOCT), we propose a deep learning-based residual en-decoder network (REDN) method. In our approach, we reformulate the definition for obtaining the true phase as obtaining an integer multiple of 2π at each pixel by semantic segmentation. The proposed REDN architecture can provide recognition performance with pixel-level accuracy. To address the lack of phase images that are noise and wrapping free from DOCT systems for training, we used simulated images synthesized with DOCT phase image background noise features. An evaluation study on simulated images, DOCT ...

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      Mentions: Yong Huang
    13. Dual-band infrared optical coherence tomography using a single supercontinuum source

      Dual-band infrared optical coherence tomography using a single supercontinuum source

      Recent developments and commercial availability of low-noise and bright infrared (IR) supercontinuum sources initiated intensive applied research in the last few years. Covering a significant part of near- and mid-infrared spectral ranges, supercontinuum radiation opened up unique possibilities and alternatives for the well-established imaging technique of optical coherence tomography (OCT). In this contribution, we demonstrate the development, performance, and maturity of a cost-efficient dual-band Fourier-domain IR OCT system (2 µm and 4 µm central wavelengths). The proposed OCT setup is elegantly employing a single supercontinuum source and a pyroelectric linear array. We discuss adapted application-oriented approaches to signal acquisition and ...

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    14. Mirau-based line-field confocal optical coherence tomography

      Mirau-based line-field confocal optical coherence tomography

      Line-field confocal optical coherence tomography (LC-OCT) is an imaging technique in which A-scans are acquired in parallel through line illumination with a broadband laser and line detection with a line-scan camera. B-scan imaging at high spatial resolution is achieved by dynamic focusing in a Linnik interferometer. This paper presents an LC-OCT device based on a custom-designed Mirau interferometer that offers similar spatial resolution and detection sensitivity. The device has the advantage of being more compact and lighter. In vivo imaging of human skin with a resolution of 1.3 µm × 1.1 µm (lateral × axial) is demonstrated over a field ...

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    15. Comparative study of deep learning models for optical coherence tomography angiography

      Comparative study of deep learning models for optical coherence tomography angiography

      Optical coherence tomography angiography (OCTA) is a promising imaging modality for microvasculature studies. Meanwhile, deep learning has achieved rapid development in image-to-image translation tasks. Some studies have proposed applying deep learning models to OCTA reconstruction and have obtained preliminary results. However, current studies are mostly limited to a few specific deep neural networks. In this paper, we conducted a comparative study to investigate OCTA reconstruction using deep learning models. Four representative network architectures including single-path models, U-shaped models, generative adversarial network (GAN)-based models and multi-path models were investigated on a dataset of OCTA images acquired from rat brains. Three ...

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    16. Optical coherence tomography modeling incorporating scattering, absorption, and multiple reflections

      Optical coherence tomography modeling incorporating scattering, absorption, and multiple reflections

      A direct scattering optical coherence tomography forward model was developed to simulate A-scans for both idealized and real light sources on an arbitrary given sample structure. Previous models neglected absorption, scattering, and multiple reflections at interfacial layers, and so two extended models were developed to investigate the impact of these processes. The first model uses the Beer–Lambert law to incorporate both absorption and scattering optical processes, and the second model uses a recursive form to model multiple reflections. These models were tested on a structure representative of a multilayered skin sample. The results show that the absorption and scattering ...

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    17. Optical coherence tomography imaging of plant root growth in soil

      Optical coherence tomography imaging of plant root growth in soil

      Complex interactions between roots and soil provide the nutrients and physical support required for robust plant growth. Yet, visualizing the root–soil interface is challenged by soil’s opaque scattering characteristics. Herein, we describe methods for using optical coherence tomography (OCT) to provide non-destructive 3D and cross-sectional root imaging not available with traditional bright-field microscopy. OCT is regularly used for bioimaging, especially in ophthalmology, where it can detect retinal abnormalities. Prior use of OCT in plant biology has focused on surface defects of above-ground tissues, predominantly in food crops. Our results show OCT is also viable for detailed, in situ ...

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    18. Light-efficient beamsplitter for Fourier-domain full-field optical coherence tomography

      Light-efficient beamsplitter for Fourier-domain full-field optical coherence tomography

      Any full-field optical coherence tomography (FF-OCT) system wastes almost 75% of light, including 50% of the OCT signal, because it uses a 50/50 beamsplitter (BS) in the standard implementation. Here, a design of a light-efficient BS is presented that loses almost no light when implemented in Fourier-domain FF-OCT. It is based on pupil engineering and a small highly asymmetric BS. The presented signal-to-noise ratio (SNR) analysis demonstrates almost four times improvement over the conventional design. In addition, it is shown that the light-efficient BS can be used to suppress specular reflections from a sample and, thus, further improve the ...

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    19. Deep learning segmentation for optical coherence tomography measurements of the lower tear meniscus

      Deep learning segmentation for optical coherence tomography measurements of the lower tear meniscus

      The tear meniscus contains most of the tear fluid and therefore is a good indicator for the state of the tear film. Previously, we used a custom-built optical coherence tomography (OCT) system to study the lower tear meniscus by automatically segmenting the image data with a thresholding-based segmentation algorithm (TBSA). In this report, we investigate whether the results of this image segmentation algorithm are suitable to train a neural network in order to obtain similar or better segmentation results with shorter processing times. Considering the class imbalance problem, we compare two approaches, one directly segmenting the tear meniscus (DSA), the ...

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    20. Dispersion correction for optical coherence tomography by the stepped detection algorithm in the fractional Fourier domain

      Dispersion correction for optical coherence tomography by the stepped detection algorithm in the fractional Fourier domain

      Dispersion in optical coherence tomography (OCT) leads to a series of wavelength-dependent phase distortions, which cause degradation of axial resolution. Due to the lack of prior information or the complexity of an exhaustive search calculation, all-depth dispersion suppression can hardly be realized in practical cases, especially for high-speed processing and irregular-structure samples. This paper explores the understanding of the depth-dependent dispersion in the fractional Fourier domain (FRFD) and addresses a new method for dispersion correction based on the FRFD stepped detection algorithm that is able to adaptively compensate the dispersion at all depths of the sample. For the detection of ...

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    21. Three-dimensional detection and quantification of defects in SiC by optical coherence tomography

      Three-dimensional detection and quantification of defects in SiC by optical coherence tomography

      Silicon carbide (SiC) is widely used in high power electronic devices. However, defects on the SiC significantly reduce the yield and decrease the performance of SiC. Accurate detection of the defects is essential in the process control. We demonstrated a noninvasive three-dimensional (3D) defect detection method for SiC using optical coherence tomography (OCT). Defects including the triangular defects, hexagonal voids, grain boundaries, and carrot defects were inspected and analyzed on SiC wafers. The 3D images of defects acquired with OCT provided detailed information on the 3D structures and dimensions of defects, and the locations and orientations of the defects inside ...

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      Mentions: Pei Ma
    22. Uniform focusing with an extended depth range and increased working distance for optical coherence tomography by an ultrathin monolith fiber probe

      Uniform focusing with an extended depth range and increased working distance for optical coherence tomography by an ultrathin monolith fiber probe

      It is difficult to maintain high transverse resolution over an increased depth range using miniature probes for optical coherence tomography (OCT) due to the rapid divergence of light and the space limitation. To solve this problem, we introduce a fiber-based filter in the proposed probe to manipulate its output beam. Significant mode interference (MI) is exploited to enhance the depth of focus (DOF), and the mode phase difference is tuned to achieve a uniform axial intensity within the DOF. The magnified MI field instead of the diffracted one is adopted as the final pupil filter in the probe to increase ...

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    23. Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping

      Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping

      The retinal volumetric flow rate contains useful information not only for ophthalmo-logy but also for the diagnosis of common civilization diseases such as diabetes, Alzheimer's disease, or cerebrovascular diseases. Non-invasive optical methods for quantitative flow assessment, such as Doppler optical coherence tomography (OCT), have certain limitations. One is the phase wrapping that makes simultaneous calculations of the flow in all human retinal vessels impossible due to a very large span of flow velocities. We demonstrate that three-dimensional Doppler OCT combined with three-dimensional four Fourier transform fast phase unwrapping (3D 4FT FPU) allows for the calculation of the volumetric blood ...

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    1-24 of 709 1 2 3 4 ... 28 29 30 »
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