1. Articles from Linbo Liu

    1-24 of 62 1 2 3 »
    1. Postdoctoral Position Opening in High Resolution OCT at Nanyang Technological University

      Postdoctoral Position Opening in High Resolution OCT at Nanyang Technological University

      x The School of Electrical & Electronic Engineering at the Nanyang Technological University invites applications for a postdoctoral fellow position in the area of high resolution optical coherence tomography (OCT) devices. The successful candidate will work on a collaborative research project with a focus on micro-optical coherence tomography, synthetic aperture endoscopy, and point-of-care optical imaging devices. Specific requirements: A PhD’s degree in optical instrumentation, optics and optical technology, precision instrument or related fields; Extensive experiences in optical microscopic or endoscopic system design and alignment; Experiences in designing and development of opto-mechanical systems such as an OCT endoscope; Research track records ...

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    2. High-Resolution Optical Coherence Tomography (OCT) for Skin Imaging (Book Chapter)

      High-Resolution Optical Coherence Tomography (OCT) for Skin Imaging (Book Chapter)

      This important, timely book covers the latest understanding about today's major skin disorders, the development of imaging technologies for skin diagnosis, and the applications of micro/nano-technologies for the treatment of skin complications. It also places great emphasis on the critical role that interdisciplinary science occupies to achieve the requisite level of understanding of skin conditions and their management, which is essential to creating technologies that work. Imaging Technologies and Transdermal Delivery in Skin Disorders starts by outlining the structural characteristics of skin and skin appendages. It then discusses the key pathways involved in skin growth and development. Clinical ...

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    3. Excess mucus viscosity and airway dehydration impact COPD airway clearance

      Excess mucus viscosity and airway dehydration impact COPD airway clearance

      The mechanisms by which cigarette smoking impairs airway mucus clearance are not well understood. We recently established a ferret model of cigarette smoke-induced chronic obstructive pulmonary disease (COPD) exhibiting chronic bronchitis. We investigated the effects of cigarette smoke on mucociliary transport (MCT). Adult ferrets were exposed to cigarette smoke for 6 months, with in vivo mucociliary clearance (MCC) measured by Tc-labeled DTPA (Tc-DTPA) retention. Excised tracheae were imaged with micro-optical coherence tomography. Mucus changes in primary human airway epithelial cells and ex vivo ferret airways were assessed by histology and particle tracking microrheology. Linear mixed models for repeated measures identified ...

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    4. Constrained polarization evolution simplifies depth-resolved retardation measurements with polarization-sensitive optical coherence tomography

      Constrained polarization evolution simplifies depth-resolved retardation measurements with polarization-sensitive optical coherence tomography

      We observed that the polarization state of light after round-trip propagation through a birefringent medium frequently aligns with the employed input polarization state ‘mirrored’ by the horizontal plane of the Poincaré sphere. We explored the predisposition for this mirror state and evidence that it constrains the evolution of polarization states as a function of the round-trip depth into weakly scattering birefringent samples, as measured with polarization-sensitive optical coherence tomography (PS-OCT). Combined with spectral variations in the polarization state transmitted through system components, we demonstrate how this constraint enables measurement of depth-resolved birefringence using only a single input polarization state, which ...

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    5. Rapid, High-Resolution, Label-Free, and 3-Dimensional Imaging to Differentiate Colorectal Adenomas and Non-Neoplastic Polyps With Micro-Optical Coherence Tomography

      Rapid, High-Resolution, Label-Free, and 3-Dimensional Imaging to Differentiate Colorectal Adenomas and Non-Neoplastic Polyps With Micro-Optical Coherence Tomography

      INTRODUCTION: “ Resectanddiscard ” paradigmisoneofthemainstrategiestodealwithcolorectaldiminutivepolyps after optical diagnosis. However, there are risks that unrecognized potentially malignant lesions are discarded without accurate diagnosis. The purpose of this study is to validate the potential of micro- optical coherence tomography ( m OCT) to improve the diagnostic accuracy of colorectal lesions and help endoscopists make better clinical decision without additional pathology costs. METHODS: RESULTS: DISCUSSION: Fresh tissue samples were obtained from patients with colorectal polyps or colorectal cancer who received endoscopic therapy or laparoscopic surgery. These samples were instantly imaged by m OCT and then sent to pathological evaluation. Then, m OCT images were compared with ...

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    6. Automatic evaluation of stratum basale and dermal papillae using ultrahigh resolution optical coherence tomography

      Automatic evaluation of stratum basale and dermal papillae using ultrahigh resolution optical coherence tomography

      Diagnosis of many skin conditions requires evaluation of dermal papillae and stratum basale, such as vitiligo. In clinical practice, imaging dermal papillae structures relies on excisional biopsy followed by histological processing and analysis. As biopsy is invasive and associated with complications, a noninvasive imaging method such as optical coherence tomography (OCT) can complement the existing method by enabling large area scanning. However, because OCT image analysis requires training and it takes time to review OCT images from large skin areas, an automatic evaluation method is preferred to reduce the workload and avoid ‘sampling errors’ during image analysis. Here we report ...

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    7. Methods, systems, arrangements and computer-accessible medium for providing micro-optical coherence tomography procedures

      Methods, systems, arrangements and computer-accessible medium for providing micro-optical coherence tomography procedures

      Exemplary apparatus and method can be provided for obtaining data regarding a plurality of samples. For example, using at least one arrangement, it is possible to receive interferometric information that is based on radiations provided from a reference and the samples that are provided in respective chambers. Alternatively and/or in addition, based on the interferometric information, it is possible to discriminate between agents to identify a particular agent that affects a particular function within at least one of the samples.

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    8. Are nuclei in stratified squamous epithelium high scattering or low scattering?

      Are nuclei in stratified squamous epithelium high scattering or low scattering?

      Imaging nuclei of keratinocytes in the stratified squamous epithelium has been a subject of intense research since nucleus associated cellular atypia is the key criteria for the screening and diagnosis of epithelial cancers and their precursors. However, keratinocyte nuclei have been reported to be either low scattering or high scattering, so that these inconsistent reports might have led to misinterpretations of optical images, and more importantly, hindered the establishment of optical diagnostic criteria. We disclose that they are generally low scattering in the core using Micro-optical coherence tomography (µOCT) of 1.28-µm axial resolution in vivo; those previously reported ...

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    9. Single input state polarization-sensitive optical coherence tomography with high resolution and polarization distortion correction

      Single input state polarization-sensitive optical coherence tomography with high resolution and polarization distortion correction

      Abstract: In single input state polarization-sensitive optical coherence tomography (PS-OCT) with high resolution, the imperfections of quarter-wave plate (QWP) and the sensitivity roll-off mismatch between the two detection channels cause unpredictable polarization distortion. We present a correction method based on the Jones matrix modeling of the system. In a single input PS-OCT system working at 840 nm with an axial resolution of ~2.3 μm, the method yielded better estimation of retardation and optic axis orientation with significantly reduced noise level, especially in weakly birefringent samples. Numerical simulations and quantitative imaging of a sample of known birefringence were performed to ...

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    10. Optical coherence tomography with gapped spectrum

      Optical coherence tomography with gapped spectrum

      The axial resolution of optical coherence tomography (OCT) is determined by the spectral shape and bandwidth of the detected light, which are limited by the gaps in the wavelength range of illumination, transmission, and detection. In this work, we demonstrate that the axial resolution deteriorated by gaps in OCT spectra can be restored by adopting the gapped amplitude and phase estimation (GAPES) method. GAPES estimates the missing parts between separated spectral bands and obtains the axial profile of tissue with reduced sidelobe artifacts compared to the gapped spectra and significantly improved axial resolution over the individual bands. This technique may ...

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    11. Nondestructive Measurement of Conformal Coating Thickness on Printed Circuit Board with Ultra-high Resolution Optical Coherence Tomography

      Nondestructive Measurement of Conformal Coating Thickness on Printed Circuit Board with Ultra-high Resolution Optical Coherence Tomography

      Conformal coating (CC) is widely used to protect printed circuit board (PCB) from corrosion, mould growth and electrical failures. To ensure an effective protection, the thickness of the conformal coating layer needs to be well controlled. However, to date, the coating thickness is usually measured in a destructive way under microscopes. In this study, we proposed to use optical coherence tomography (OCT) to measure the CC thickness nondestructively. Specifically, to obtain a good accuracy in thickness measurement, we constructed a spectral domain OCT (SD-OCT) with ultra-high axial resolution to image the CC layer in three dimensions, and developed an image ...

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    12. Cellular resolution corneal imaging with extended imaging range

      Cellular resolution corneal imaging with extended imaging range

      Current optical coherence tomography (OCT) technology, which is used for imaging the eye’s anterior segment, has been established as a clinical gold standard for the diagnosis of corneal diseases. However, the cellular resolution level information that is critical for many clinical applications is still not available. The major technical challenges toward cellular resolution OCT imaging are the limited ranging depth and depth of focus (DOF). In this work, we present a novel ultrahigh resolution OCT system that achieves an isotropic spatial resolution of <2 µm in tissue. The proposed system could approximately double the ranging depth and extend the ...

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    13. Estimation of refractive index for biological tissue using micro-optical coherence tomography

      Estimation of refractive index for biological tissue using micro-optical coherence tomography

      The refractive index of biological tissue is required for investigating the tissue's optical properties. Efforts have been made to characterize refractive indices of biological tissues at a single wavelength, but it is more convenient to know the Cauchy's coefficients, which provide refractive index over a wide range of wavelengths. We demonstrate a method to noninvasively provide the Cauchy's dispersion coefficients of biological tissues using micro-optical coherence tomography. Using short-frequency Fourier transforms, the relative optical thickness of the sample in the wavelength range of the broadband source was obtained from interferograms. The coefficients of Cauchy's equation were ...

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    14. Imaging cellular structures of atherosclerotic coronary arteries using circumferentially scanning micro-optical coherence tomography fiber probe ex vivo

      Imaging cellular structures of atherosclerotic coronary arteries using circumferentially scanning micro-optical coherence tomography fiber probe ex vivo

      Development and progression of coronary atherosclerotic lesions is mediated by a number of cellular components, which are not readily visualized using the current clinical investigation tools. Visualizing these cellular components in situ and in vivo may allow early detection of the vulnerable plaques, with implications for coronary artery disease (CAD) therapy and for the prevention of acute myocardial infarction (AMI). In this study, we have developed a fiber-optic micro-optical coherence tomography (µOCT) probe for intravascular use. We conducted ex vivo imaging experiments in normal swine aorta and human atherosclerotic coronary arteries, and demonstrate that the fiber-probe based µOCT could delineate ...

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    15. Novel application of In Vivo Micro-Optical Coherence Tomography to assess Cornea scarring in an Animal Model

      Novel application of In Vivo Micro-Optical Coherence Tomography to assess Cornea scarring in an Animal Model

      This pilot study uses a micro-optical coherence tomography (micro-OCT) system with ~1 μm axial resolution specifically to image the cornea and corneal scars in vivo . We used an established murine corneal scar model by irregular phototherapeutic keratectomy in ten C57BL/6 mice, with serial imaging using the micro-OCT and compared to anterior segment (AS-OCT) (RTvue, Optovue, Fremont, CA) before and after scar induction. Main outcome was agreement between the AS-OCT and micro-OCT using Bland-Altman plots (95% limits of agreement, LoA).We analysed 10 control eyes and 10 eyes with corneal scars and found that there was good agreement between AS-OCT ...

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    16. Extending the depth of focus of fiber-optic optical coherence tomography using a chromatic dual-focus design

      Extending the depth of focus of fiber-optic optical coherence tomography using a chromatic dual-focus design

      We report a dual-focus fiber-optic probe designed to extend depth of focus (DOF) in high-resolution endoscopic optical coherence tomography. We exploited the broad spectral bandwidth of a supercontinuum source and, in the fiber probe, the foci of the 750–1000 nm and 1100–1450 nm inputs were axially chromatically shifted. The interference signals from the two spectral bands were measured with a Si camera-based spectrometer and an InGaAs camera-based spectrometer, respectively. We verified the feasibility of the design using a phantom composed of microparticles and swine small intestine tissue ex vivo . The results showed that a transverse resolution below 5 ...

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    17. Multiscale skin imaging in vivo using optical coherence tomography

      Multiscale skin imaging in vivo using optical coherence tomography

      Optical coherence tomography (OCT) is a noninvasive high-resolution diagnostic imaging modality that plays an increasingly important role in dermatology. Diagnosis of skin diseases using OCT requires both cellular-level high resolution and large area skin coverage. In practice, however, there exists a trade-off between the achievable spatial resolutions and the transverse scanning range. In this study, we report a Micro-OCT ( μ OCT) system that is capable of providing three-dimensional images of the skin at multiple spatial scales with both cellular-level resolution (1–2 μ m) mode and large area (~ mm 2 ) scanning mode. Specifically, in the cellular-level scanning mode, we achieve a transverse ...

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    18. Evaluating micro-optical coherence tomography (μOCT) as a feasible imaging tool for pancreatic disease diagnosis

      Evaluating micro-optical coherence tomography (μOCT) as a feasible imaging tool for pancreatic disease diagnosis

      Pancreatic cancer is one of the leading causes of cancer mortality worldwide due to the lack of reliable tools for early diagnosis of this cancer. In this study, we evaluated the feasibility of micro-optical coherence tomography (μOCT) as an imaging tool for the diagnosis of pancreatic cancers. Specifically, we constructed a μOCT device that achieves a resolution of ∼1.67 μm and 1.79 μm in axial and lateral directions, respectively, and acquires three-dimensional μOCT images of mouse, rat and human pancreatic specimens ex vivo. We compared the results of μOCT with those of the corresponding histology. In μOCT images ...

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    19. Extending axial focus of optical coherence tomography using parallel multiple aperture synthesis

      Extending axial focus of optical coherence tomography using parallel multiple aperture synthesis

      Compromising the inherent trade-off between transverse resolution and depth of focus (DOF) remains a long-standing issue in optical coherence tomography (OCT). In this work, we report a novel technique—parallel multiple aperture synthesis (pMAS) to simultaneously generate multiple optical apertures in an OCT sample arm by employing a two-surface coated mirror. In the proposed pMAS, the DOF is extended by a factor of 16.49 without sacrificing the transverse resolution for proof-of-concept experiments when multiple distinctive apertures are digitally synthesized. The microparticles and tissue experiments demonstrate the feasibility of pMAS to address the fundamental problem of limited DOF in high-resolution ...

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    20. Multiple aperture synthetic optical coherence tomography for biological tissue imaging

      Multiple aperture synthetic optical coherence tomography for biological tissue imaging

      An inherent compromise must be made between transverse resolution and depth of focus (DOF) in spectral domain optical coherence tomography (SD-OCT). Thus far, OCT has not been capable of providing a sufficient DOF to stably acquire cellular-resolution images. We previously reported a novel technique named multiple aperture synthesis (MAS) to extend the DOF in high-resolution OCT [Optica 4, 701 (2017)]. In this technique, the illumination beam is scanned across the objective lens pupil plane by being steered at the pinhole using a custom-made microcylindrical lens. Images captured via multiple distinctive apertures were digitally refocused, which is similar to synthetic aperture ...

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    21. Visualizing Micro-anatomical Structures of the Posterior Cornea with Micro-optical Coherence Tomography

      Visualizing Micro-anatomical Structures of the Posterior Cornea with Micro-optical Coherence Tomography

      Diagnosis of corneal disease and challenges in corneal transplantation require comprehensive understanding of corneal anatomy, particularly that of the posterior cornea. Micro-optical coherence tomography (µOCT) is a potentially suitable tool to meet this need, owing to its ultrahigh isotropic spatial resolution, high image acquisition rate and depth priority scanning mode. In this study, we explored the ability of µOCT to visualize micro-anatomical structures of the posterior cornea ex vivo and in vivo using small and large animals. µOCT clearly delineated cornea layers and revealed micro-anatomical structures, including not only polygonal endothelial cells, stellate keratocytes, collagen fibres and corneal nerve fibres ...

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    22. Endomicroscopic optical coherence tomography for cellular resolution imaging of gastrointestinal tracts

      Endomicroscopic optical coherence tomography for cellular resolution imaging of gastrointestinal tracts

      Our ability to detect neoplastic changes in gastrointestinal (GI) tracts is limited by the lack of an endomicroscopic imaging tool that provides cellular-level structural details of GI mucosa over a large tissue area. In this paper, we report a fiber-optic based micro-optical coherence tomography (μOCT) system and demonstrate its capability to acquire cellular-level details of GI tissue through circumferential scanning. The system achieves an axial resolution of 2.48 µm in air and a transverse resolution of 4.8 µm with a depth-of-focus (DOF) of ~150 µm. To mitigate the issue of limited DOF, we used a rigid sheath to ...

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    23. Polarization management to mitigate misalignment-induced fringe fading in fiber-based optical coherence tomography

      Polarization management to mitigate misalignment-induced fringe fading in fiber-based optical coherence tomography

      In fiber-based optical coherence tomography (OCT), the interference fringes suffer from the fading effect due to misalignment of the light polarization states between the reference and sample arms, resulting in sensitivity degradation and image intensity variation. We theoretically and experimentally analyzed the relation between the misalignment and the fading coefficient. Assuming that the variation of the light polarization in single-mode fiber (SMF) was a random process, we statistically quantified the fading effect. Furthermore, in OCT configuration based on the Michelson interferometer, we reported an interesting observation that the polarization states of light traveling a round-trip in SMF are not evenly ...

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    24. Feature Of The Week 06/27/2017: Depth-of-Focus Extension in Optical Coherence Tomography via Multiple Aperture Synthesis

      Feature Of The Week 06/27/2017: Depth-of-Focus Extension in Optical Coherence Tomography via Multiple Aperture Synthesis

      In this paper, we report what we believe is a novel technique to overcome the depth-of-focus (DOF) limitation in optical coherence tomography (OCT). Using confocal optics on a sample arm, we scanned the illumination beam across the under-filled objective lens pupil plane by steering the beam at the pinhole using a microcylindrical lens. The detected interferometric signals from multiple distinctive apertures were digitally refocused, which is analogous to synthetic aperture radar (SAR). Using numerical simulations and imaging experiments, we verified that this technique can maintain a diffraction-limited transverse resolution along a DOF that is ∼10 times larger than the confocal ...

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    1-24 of 62 1 2 3 »
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    1. (61 articles) Linbo Liu
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