1. Articles from Peng Li

    1-24 of 49 1 2 »
    1. Three-dimensional optical coherence digital-null deformography of multi-refractive-surface optics with nanometer sensitivity

      Three-dimensional optical coherence digital-null deformography of multi-refractive-surface optics with nanometer sensitivity

      Knowledge of the lens deformation during the reliability test is critical for lens design and fabrication. Refractive surface distorts the optical path of probing light, and poses a great challenge to measuring the test-induced nanoscale changes of all refractive lens surfaces simultaneously. In this work, we present an optical coherence digital-null deformography (ODD). A digital null, i.e., the interference signals (including intensity and phase) of the backscattered probing light from each lens surface, was recorded prior to the test with a phase-sensitive optical coherence tomography (OCT). Then the post-test lens was physically aligned to the digital null by actuating ...

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    2. OCT Retinal fundus image super-resolution based on a realistic mixed attention GAN (RMA-GAN)

      OCT Retinal fundus image super-resolution based on a realistic mixed attention GAN (RMA-GAN)

      Purpose: Optical coherence tomography (OCT) is widely used to diagnose retinal diseases. However, due to the limited resolution of OCT imaging systems, the quality of fundus images displayed is not satisfactory, which hinders the diagnosis of patients by ophthalmologists. This is an inevitable problem of OCT imaging systems, but few people have given attention to it. We attempt to solve this problem through deep learning methods. Methods: In this paper, we propose a single image superresolution (SISR) model that is based on a generative adversarial network (GAN) for restoring low-resolution (LR) OCT fundus images to high-resolution (HR) counterparts. To obtain ...

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    3. Automatic 3D adaptive vessel segmentation based on linear relationship between intensity and complex-decorrelation in optical coherence tomography angiography

      Automatic 3D adaptive vessel segmentation based on linear relationship between intensity and complex-decorrelation in optical coherence tomography angiography

      Background: Vascular quantitative metrics have been widely used in the preclinical studies and clinical applications (e.g., the diagnosis and treatment of port wine stain, PWS), which require accurate vessel segmentation. An automatic 3D adaptive vessel segmentation is in need for a reproducible and objective quantification of the optical coherence tomography angiography (OCTA) image. Methods: Human skin imaging was performed with a lab-built optical coherence tomography (OCT) system. Rather than separately applying the conventional 2-step (intensity and binarization) thresholding in the decorrelation-contrast OCTA, we proposed a 3D adaptive threshold using the linear relationship between the local intensity and complex-decorrelation which ...

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    4. High performance OCTA enabled by combining features of shape, intensity, and complex decorrelation

      High performance OCTA enabled by combining features of shape, intensity, and complex decorrelation

      Motion contrast optical coherence tomography angiography (OCTA) entails a precise identification of dynamic flow signals from the static background, but an intermediate region with voxels exhibiting a mixed distribution of dynamic and static scatterers is almost inevitable in practice, which degrades the vascular contrast and connectivity. In this work, the static-dynamic intermediate region was pre-defined according to the asymptotic relation between inverse signal-to-noise ratio (iSNR) and decorrelation, which was theoretically derived for signals with different flow rates based on a multi-variate time series (MVTS) model. Then the ambiguous voxels in the intermediate region were further differentiated using a shape mask ...

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    5. INS-fOCT: a label-free, all-optical method for simultaneously manipulating and mapping brain function

      INS-fOCT: a label-free, all-optical method for simultaneously manipulating and mapping brain function

      Significance: Current approaches to stimulating and recording from the brain have combined electrical or optogenetic stimulation with recording approaches, such as two-photon, electrophysiology (EP), and optical intrinsic signal imaging (OISI). However, we lack a label-free, all-optical approach with high spatial and temporal resolution. Aim: To develop a label-free, all-optical method that simultaneously manipulates and images brain function using pulsed near-infrared light (INS) and functional optical coherence tomography (fOCT), respectively. Approach: We built a coregistered INS, fOCT, and OISI system. OISI and EP recordings were employed to validate the fOCT signals. Results: The fOCT signal was reliable and regional, and the ...

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    6. 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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    7. Apparatus and method for measuring blood flow of vessels

      Apparatus and method for measuring blood flow of vessels

      An apparatus and a method for measuring blood flow of vessels are provided. The apparatus includes a light source, a light splitting module, a reference arm module, a sample arm module, a probing module, and a control system. The sample arm module includes a scanning unit and an optical-path shifting device. A probe light is obtained from the light splitting module, and a central line of a main light of the probe light extends through a rotation axis of the scanning unit. The probe light is reflected by the scanning unit to the optical-path shifting device. When the optical-path shifting ...

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    8. Quantitative assessment of skin swelling using optical coherence tomography

      Quantitative assessment of skin swelling using optical coherence tomography

      Background Preclinical and clinical studies suggest that optical coherence tomography (OCT) is a useful tool to visualize inflammatory conditions. Objective The objective of this study was to evaluate the usefulness of combining OCT and various image processing techniques for quantitative assessment of histamine-induced tissue swelling. Methods Both time-domain and frequency-domain OCT were used on a mouse ear model. The ear thickness and volume before and after histamine challenge were determined from pixel locations in 2D scans and voxel number counting in 3D scans. Swelling kinetics was analyzed on 3D contour mapping. Microvessel network was visualized using speckle decorrelation analysis. Results ...

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    9. Anterior Segment Biometry with Phenylephrine and Tropicamide during Accommodation Imaged with Ultralong Scan Depth Optical Coherence Tomography

      Anterior Segment Biometry with Phenylephrine and Tropicamide during Accommodation Imaged with Ultralong Scan Depth Optical Coherence Tomography

      Purpose . To investigate the influence of phenylephrine and tropicamide on anterior segment biometry with ultralong scan depth optical coherence tomography (UL-OCT) during accommodation. Methods . In this study, 20 left eyes of healthy volunteers with a mean ± standard deviation age of 31.05 ± 5.84 years and a mean refraction of −1.16 ± 1.11 diopters (range 0∼−3.0 D) were imaged using UL-OCT after instillation of artificial tears, phenylephrine, and tropicamide in three follow-up trials, respectively. At each follow-up trial, two repeated measurements were performed at states of relax and 5D accommodative stimulation. The dimensional parameters included central corneal ...

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    10. All-fiber probe for optical coherence tomography with an extended depth of focus by a high-efficient fiber-based filter

      All-fiber probe for optical coherence tomography with an extended depth of focus by a high-efficient fiber-based filter

      Although methods have been proposed to maintain high transverse resolution over an increased depth range, it is not straightforward to scale down the bulk-optic solutions to minimized probes of optical coherence tomography (OCT). In this paper, we propose a high-efficient fiber-based filter in an all-fiber OCT probe to realize an extended depth of focus (DOF) while maintaining a high transverse resolution. Mode interference in the probe is exploited to modulate the complex field with controllable radial distribution. The principle of DOF extension by the fiber-based filter is theoretically analyzed. Numerical simulations are conducted to evaluate the performances of the designed ...

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    11. Adaptive classifier allows enhanced flow contrast in OCT angiography using a histogram-based motion threshold and 3D Hessian analysis-based shape filtering

      Adaptive classifier allows enhanced flow contrast in OCT angiography using a histogram-based motion threshold and 3D Hessian analysis-based shape filtering

      In this Letter, we propose an adaptive digital classifier for flow contrast enhancement in optical coherence tomography angiography (OCTA). To solve the depth dependence in the initial motion-based classification, a depth-adaptive motion threshold was determined by performing a histogram analysis of an en-face image at each depth and identifying the static and dynamic voxel populations through fitting. In the follow-up shape-based classification, to adapt to the deformed vessel shapes in OCTA, a modified vesselness function along with an anisotropic Gaussian probe kernel was defined, and then a three-dimensional (3D) Hessian analysis-based shape filtering was utilized for effectively removing the residual ...

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    12. Quasi-needle-like focus synthesized by optical coherence tomography

      Quasi-needle-like focus synthesized by optical coherence tomography

      It is known that lateral resolution and depth of focus (DOF) in an optical imaging system are coupled, and a compromise between them has to be made. In this Letter, we propose to resolve the trade-off between lateral resolution and the DOF by a synthetic effective point spread function in optical path length (OPL) domain. A quasi-needle-like focus is synthesized by optical coherence tomography. We demonstrate that the synthesized quasi-needle-like focus provides a four-fold extension of a conventional DOF, while maintaining a high lateral resolution of 2.5 μm over a depth range of approximately 240 μm. The focal range ...

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    13. Motion correction using overlapped data correlation based on a spatial-spectral encoded parallel optical coherence tomography

      Motion correction using overlapped data correlation based on a spatial-spectral encoded parallel optical coherence tomography

      This paper presents an approach to remove motion artifacts based on a spatial-spectral encoded parallel OCT (SSE-POCT) system, where encoded rectangular illumination is employed. Motion artifacts within a B-scan are avoided due to parallel detection intrinsic to parallel OCT, while those between successive B-scans are estimated and corrected by a proposed overlapped data correlation (ODC) algorithm. To preserve axial resolution, decoded B-scan corresponding to complete spectrum is stitched from successive encoded B-scans after motion correction. Imaging is conducted on several samples under preset motion trajectories, and OCT images with unnoticed motion artifacts and well-preserved resolutions are reconstructed. The approach based ...

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    14. A useful way to develop effective in vivo skin optical clearing agents

      A useful way to develop effective in vivo skin optical clearing agents

      Skin optical clearing has shown tremendous potential in improving various optical imaging performances, but there is some certain blindness in screening out high-efficiency in vivo optical clearing methods. In this work, three optical clearing agents: sucrose (Suc), fructose (Fruc) and PEG-400 (PEG), and two chemical penetration enhancers: propylene glycol (PG) and thiazone (Thiaz) were used. PEG was firstly mixed with the two penetration enhancers, respectively, and then mixed with Fruc and Suc, respectively, to obtain six kinds of skin optical clearing agents (SOCAs). Optical coherence tomography angiography was applied to monitor SOCAs-induced changes in imaging performances, skin optical properties, refractive ...

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    15. Angular compounding by full-channel B-scan modulation encoding for optical coherence tomography speckle reduction

      Angular compounding by full-channel B-scan modulation encoding for optical coherence tomography speckle reduction

      We describe an angular compounding method by full-channel B-scan modulation encoding for speckle reduction in optical coherence tomography. The complex-valued spectral interferogram (SI) is reconstructed by removing one of the conjugate terms in the depth space. Fourier transform of the complex SI along the lateral direction enables a full-channel (with both negative and positive Fourier space) for B-scan modulation in the spatial frequency ( ν ν ) domain. A full-size probe beam, determined by the scanning mirror size, is centered on the mirror pivot, which allows the negative and positive half-channels working in parallel. Compared with the existing method, where only a half-channel (negative ...

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    16. Hybrid averaging offers high-flow contrast by cost apportionment among imaging time, axial, and lateral resolution in optical coherence tomography angiography

      Hybrid averaging offers high-flow contrast by cost apportionment among imaging time, axial, and lateral resolution in optical coherence tomography angiography

      The current temporal, wavelength, angular, and spatial averaging approaches trade imaging time and resolution for multiple independent measurements that improve the flow contrast in optical coherence tomography angiography (OCTA). We find that these averaging approaches are equivalent in principle, offering almost the same flow contrast enhancement as the number of averages increases. Based on this finding, we propose a hybrid averaging strategy for contrast enhancement by cost apportionment. We demonstrate that, compared with any individual approach, the hybrid averaging is able to offer a desired flow contrast without severe degradation of imaging time and resolution. Making use of the extended ...

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    17. Ophthalmic optical coherence tomography system and method for quick switching to realize anterior and posterior eye segments imaging

      Ophthalmic optical coherence tomography system and method for quick switching to realize anterior and posterior eye segments imaging

      An ophthalmic optical coherence tomography system and a method for quick switching to realize anterior and posterior eye segments imaging are provided, the system includes: an OCT interferometer primary module and a sample arm module, the OCT interferometer primary module includes an OCT light source, a fiber coupler, a reference arm, a detection module, an X-direction scanning unit, and a Y-direction scanning unit; the sample arm module includes an anterior eye segment imaging module and a posterior eye segment imaging module; the Y-direction scanning unit is rotatable; when the Y-direction scanning unit is at a first rotation angle, the Y-direction ...

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    18. Optical coherence tomography angiography offers comprehensive evaluation of skin optical clearing in vivo by quantifying optical properties and blood flow imaging simultaneously

      Optical coherence tomography angiography offers comprehensive evaluation of skin optical clearing in vivo by quantifying optical properties and blood flow imaging simultaneously

      Tissue optical clearing (TOC) is helpful for reducing scattering and enhancing the penetration depth of light, and shows promising potential in optimizing optical imaging performances. A mixture of fructose with PEG-400 and thiazone (FPT) is used as an optical clearing agent in mouse dorsal skin and evaluated with OCT angiography (Angio-OCT) by quantifying optical properties and blood flow imaging simultaneously. It is observed that FPT leads to an improved imaging performance for the deeper tissues. The imaging performance improvement is most likely caused by the FPT-induced dehydration of skin, and the reduction of scattering coefficient (more than ∼ 40.5 % ∼40 ...

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    19. Single-shot angular compounded optical coherence tomography angiography by splitting full-space B-scan modulation spectrum for flow contrast enhancement

      Single-shot angular compounded optical coherence tomography angiography by splitting full-space B-scan modulation spectrum for flow contrast enhancement

      We proposed a single-shot spatial angular compounded optical coherence tomography angiography (AC-Angio-OCT) for blood flow contrast enhancement. By encoding incident angles in B-scan modulation frequencies and splitting the modulation spectrum in the spatial frequency domain, angle-resolved independent subangiograms were obtained and compounded to improve the flow contrast. A full space of the spatial frequency domain allows a wide modulation spectrum. To get access to the full space of the spatial frequency domain and avoid the complex-conjugate ambiguity of the modulation spectrum, a complex-valued OCT spectral interferogram was retrieved by removing one of the conjugate terms in the depth space. To ...

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    20. Improved motion contrast and processing efficiency in OCT angiography using complex-correlation algorithm

      Improved motion contrast and processing efficiency in OCT angiography using complex-correlation algorithm

      The complex-based OCT angiography (Angio-OCT) offers high motion contrast by combining both the intensity and phase information. However, due to involuntary bulk tissue motions, complex-valued OCT raw data are processed sequentially with different algorithms for correcting bulk image shifts (BISs), compensating global phase fluctuations (GPFs) and extracting flow signals. Such a complicated procedure results in massive computational load. To mitigate such a problem, in this work, we present an inter-frame complex-correlation (CC) algorithm. The CC algorithm is suitable for parallel processing of both flow signal extraction and BIS correction, and it does not need GPF compensation. This method provides high ...

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    21. Statistical analysis of motion contrast in optical coherence tomography angiography

      Statistical analysis of motion contrast in optical coherence tomography angiography

      Optical coherence tomography angiography (Angio-OCT), mainly based on the temporal dynamics of OCT scattering signals, has found a range of potential applications in clinical and scientific research. Based on the model of random phasor sums, temporal statistics of the complex-valued OCT signals are mathematically described. Statistical distributions of the amplitude differential and complex differential Angio-OCT signals are derived. The theories are validated through the flow phantom and live animal experiments. Using the model developed, the origin of the motion contrast in Angio-OCT is mathematically explained, and the implications in the improvement of motion contrast are further discussed, including threshold determination ...

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    22. Assessment of Full-Eye Response to Osmotic Stress in Mouse Model In Vivo Using Optical Coherence Tomography

      Assessment of Full-Eye Response to Osmotic Stress in Mouse Model In Vivo Using Optical Coherence Tomography

      NaCl based solutions were applied as osmotic stress agents to alter the hydration state of the mouse eye. Full-eye responses to these osmotic challenges were monitored in vivo using a custom-built optical coherence tomography (OCT) with an extended imaging range of 12.38 mm. Dynamic changes in the mouse eye were quantified based on the OCT images using several parameters, including the central corneal thickness (CCT), the anterior chamber depth (ACD), the crystalline lens thickness (LT), the cornea-retina distance (CRD), the iris curvature (IC), and the lens scattering intensity (LSI). Apparent but reversible changes in the morphology of almost all ...

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    23. Statistical analysis of motion contrast in optical coherence tomography angiography

      Statistical analysis of motion contrast in optical coherence tomography angiography

      Optical coherence tomography angiography (Angio-OCT), mainly based on the temporal dynamics of OCT scattering signals, has found a range of potential applications in clinical and scientific researches. In this work, based on the model of random phasor sums, temporal statistics of the complex-valued OCT signals are mathematically described. Statistical distributions of the amplitude differential (AD) and complex differential (CD) Angio-OCT signals are derived. The theories are validated through the flow phantom and live animal experiments. Using the model developed in this work, the origin of the motion contrast in Angio-OCT is mathematically explained, and the implications in the improvement of ...

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    24. Identification of surface defects on glass by parallel spectral domain optical coherence tomography

      Identification of surface defects on glass by parallel spectral domain optical coherence tomography

      Defects can dramatically degrade glass quality, and automatic inspection is a trend of quality control in modern industry. One challenge in inspection in an uncontrolled environment is the misjudgment of fake defects (such as dust particles) as surface defects. Fortunately, optical changes within the periphery of a surface defect are usually introduced while those of a fake defect are not. The existence of changes within the defect peripheries can be adopted as a criterion for defect identification. However, modifications within defect peripheries can be too small to be noticeable in intensity based optical image of the glass surface, and misjudgments ...

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    1-24 of 49 1 2 »
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