1. Articles from Qiang Yang

    1-12 of 12
    1. Characterizing Rayleigh wave and longitudinal shear wave propagation for measurements of elastic moduli using optical coherence elastography

      Characterizing Rayleigh wave and longitudinal shear wave propagation for measurements of elastic moduli using optical coherence elastography

      Optical coherence elastography based on the measurements of elastic wave speeds can quantify elastic moduli in the wave propagation directions and provide high-resolution elasticity maps for tissue. Here, we simultaneously visualized a longitudinal shear wave propagating along the depth and a Rayleigh wave propagating in the lateral direction, and analyzed the propagation characteristics of the elastic waves, including group speeds, frequency spectra, and frequency-dependent wave speeds. The analysis of the propagation characteristics demonstrates the reliability of the elasticity quantification by measuring different types of speeds of the elastic waves.

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    2. Optical Coherence Tomography Angiography for Mapping Cerebral Microvasculature Based on Normalized Differentiation Analysis

      Optical Coherence Tomography Angiography for Mapping Cerebral Microvasculature Based on Normalized Differentiation Analysis

      Optical coherence tomography angiography (OCTA) is a label‐free, noninvasive biomedical imaging modality for mapping microvascular networks and quantifying blood flow velocities in vivo . Simple computation and fast processing are critical for the OCTA in some applications. Herein, we report on a normalized differentiation method for mapping cerebral microvasculature with the advantages of simple analysis and high image quality, benefitting from computation of differentiation and characteristics of normalization. Normalized differentiation values are validated to have a nearly linear relationship with flow velocities in a range using a flow phantom. The measurements in a rat cerebral cortex show that the OCTA ...

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    3. Quantitative Assessment of Optical Coherence Tomography Angiography Algorithms for Neuroimaging

      Quantitative Assessment of Optical Coherence Tomography Angiography Algorithms for Neuroimaging

      Optical coherence tomography (OCT) angiography can noninvasively map microvascular networks and quantify blood flow in a cerebral cortex with a resolution of 1–10 μm and a penetration depth of 2–3 mm incorporating OCT signals and angiography algorithms. Different angiography algorithms have been developed in recent years; however, the performance of the algorithms has not been assessed quantitatively for neuroimaging applications. In this paper, we developed four metrics including vascular connectivity, contrast‐to‐noise ratio (CNR), signal‐to‐noise ratio (SNR) and processing time to quantitatively assess the performance of OCT angiography algorithms in image quality and computation speed ...

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    4. Extended imaging depth of en-face optical coherence tomography based on fast measurement of a reflection matrix by wide-field heterodyne detection

      Extended imaging depth of en-face optical coherence tomography based on fast measurement of a reflection matrix by wide-field heterodyne detection

      Multiple light scattering in biomedical tissue limits the penetration depth of optical imaging systems such as optical coherence tomography. To increase the imaging depth in scattering media, a computational method based on coherent reflection matrix measurement has been developed using low coherence interferometry. The complex reflection matrix is obtained via point-by-point scanning followed by a phase-shifting method; then singular value decomposition is used to retrieve the singly back-scattered light. However, the in vivo application of the current reported method is limited due to the slow acquisition speed of the matrix. In this Letter, a wide-field heterodyne-detection method is adopted to ...

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      Mentions: UC Irvine
    5. Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography

      Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography

      Multiple scattering in biomedical tissue limits the imaging depth within a range of 1–2 mm for conventional optical imaging techniques. To extend the imaging depth into the scattering medium, a computational method based on the reflection matrix measurement has been developed to retrieve the singly back-scattered signal light from the dominant detrimental multiple-scattered background. After applying singular value decomposition on the measured matrix in the post-process, the target image underneath the turbid media is clearly recovered. To increase the depth of focus of the incident light by elongating the focal spot along the optical axis, a digital grating pattern ...

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      Mentions: UC Irvine
    6. Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature

      Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature

      Endoscopic imaging technologies, such as endoscopic optical coherence tomography (OCT) and near-infrared fluorescence, have been used to investigate vascular and morphological changes as hallmarks of early cancer in the gastrointestinal tract. Here we developed a high-speed multimodality endoscopic OCT and fluorescence imaging system. Using this system, the architectural morphology and vasculature of the rectum wall were obtained simultaneously from a Sprague Dawley rat in vivo . This multimodality imaging strategy in a single imaging system permits the use of a single imaging probe, thereby improving prognosis by early detection and reducing costs.

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      Mentions: UC Irvine
    7. Quantitative angle-insensitive flow measurement using relative standard deviation OCT

      Quantitative angle-insensitive flow measurement using relative standard deviation OCT

      Incorporating different data processing methods, optical coherence tomography (OCT) has the ability for high-resolution angiography and quantitative flow velocity measurements. However, OCT angiography cannot provide quantitative information of flow velocities, and the velocity measurement based on Doppler OCT requires the determination of Doppler angles, which is a challenge in a complex vascular network. In this study, we report on a relative standard deviation OCT (RSD-OCT) method which provides both vascular network mapping and quantitative information for flow velocities within a wide range of Doppler angles. The RSD values are angle-insensitive within a wide range of angles, and a nearly linear ...

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      Mentions: UC Irvine
    8. Feature of The Week 05/19/2017: Longitudinal Shear Wave Imaging for Elasticity Mapping Using Optical Coherence Elastography

      Feature of The Week 05/19/2017: Longitudinal Shear Wave Imaging for Elasticity Mapping Using Optical Coherence Elastography

      Shear wave measurements for the determination of tissue elastic properties have been used in clinical diagnosis and soft tissue assessment. A shear wave propagates as a transverse wave where vibration is perpendicular to the wave propagation direction. Using shear wave elastography, the shear modulus of a soft tissue can be quantified by tracking the shear wave propagation. In previous measurements, the transverse shear wave propagates perpendicular to the force direction, so the shear modulus in the lateral region of the force can be quantified. However, the shear modulus in the axial region of the force cannot be measured. Dr. Jiang ...

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      Mentions: UC Irvine
    9. Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography

      Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography

      Shear wave measurements for the determination of tissue elastic properties have been used in clinical diagnosis and soft tissue assessment. A shear wave propagates as a transverse wave where vibration is perpendicular to the wave propagation direction. Previous transverse shear wave measurements could detect the shear modulus in the lateral region of the force; however, they could not provide the elastic information in the axial region of the force. In this study, we report the imaging and quantification of longitudinal shear wave propagation using optical coherence tomography to measure the elastic properties along the force direction. The experimental validation and ...

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      Mentions: UC Irvine
    10. Ultra-deep imaging of optical coherence tomography in highly scattering media

      Ultra-deep imaging of optical coherence tomography in highly scattering media

      A time-domain optical coherence tomography system based on measuring the reflection matrix of back-scattered light is proposed for extended imaging depth into scattering media. A filtering operation is applied to the reflection matrix to preserve the back-scattered light with near-forward directions while discarding most of the multiple scattered light. A singular value decomposition is then carried out in the filtered matrix for principal component analysis, to remove the residual multi-scattered light. The results show the near-forward propagating single scattered light, which is mostly discarded in conventional OCT, can be separated computationally to increase the penetration depth of OCT.

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      Mentions: UC Irvine
    11. Real-time eye motion correction in phase-resolved OCT angiography with tracking SLO

      Real-time eye motion correction in phase-resolved OCT angiography with tracking SLO

      In phase-resolved OCT angiography blood flow is detected from phase changes in between A-scans that are obtained from the same location. In ophthalmology, this technique is vulnerable to eye motion. We address this problem by combining inter-B-scan phase-resolved OCT angiography with real-time eye tracking. A tracking scanning laser ophthalmoscope (TSLO) at 840 nm provided eye tracking functionality and was combined with a phase-stabilized optical frequency domain imaging (OFDI) system at 1040 nm. Real-time eye tracking corrected eye drift and prevented discontinuity artifacts from (micro)saccadic eye motion in OCT angiograms. This improved the OCT spot stability on the retina and ...

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    12. Real-time eye motion compensation for OCT imaging with tracking SLO

      Real-time eye motion compensation for OCT imaging with tracking SLO

      Fixational eye movements remain a major cause of artifacts in optical coherence tomography (OCT) images despite the increases in acquisition speeds. One approach to eliminate the eye motion is to stabilize the ophthalmic imaging system in real-time. This paper describes and quantifies the performance of a tracking OCT system, which combines a phase-stabilized optical frequency domain imaging (OFDI) system and an eye tracking scanning laser ophthalmoscope (TSLO). We show that active eye tracking minimizes artifacts caused by eye drift and micro saccades. The remaining tracking lock failures caused by blinks and large saccades generate a trigger signal which signals the ...

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    1-12 of 12
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    1. (7 articles) UC Irvine
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    Real-time eye motion compensation for OCT imaging with tracking SLO Real-time eye motion correction in phase-resolved OCT angiography with tracking SLO Ultra-deep imaging of optical coherence tomography in highly scattering media Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography Feature of The Week 05/19/2017: Longitudinal Shear Wave Imaging for Elasticity Mapping Using Optical Coherence Elastography Quantitative angle-insensitive flow measurement using relative standard deviation OCT Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography Extended imaging depth of en-face optical coherence tomography based on fast measurement of a reflection matrix by wide-field heterodyne detection Quantitative Assessment of Optical Coherence Tomography Angiography Algorithms for Neuroimaging Perimeter Medical Imaging AI Receives U.S. FDA Breakthrough Device Designation for its Optical Coherence Tomography (OCT) Imaging System with ImgAssist AI Correlation of corpus callosum index and optic coherence tomography findings in multiple sclerosis with or without optic nerve involvement