1. Articles from Linbo Liu

    1-24 of 74 1 2 3 »
    1. Spectrally Extended Line Field Optical Coherence Tomography Angiography

      Spectrally Extended Line Field Optical Coherence Tomography Angiography

      Optical coherence tomography angiography (OCTA) has been established as a powerful tool for investigating vascular diseases and is expected to become a standard of care technology. However, its widespread clinical usage is hindered by technical gaps such as limited field of view (FOV), lack of quantitative flow information, and suboptimal motion correction. Here we report a new imaging platform, termed spectrally extended line field (SELF) OCTA that provides advanced solutions to the above-mentioned challenges. SELF-OCTA breaks the speed limitations and achieves two-fold gain in FOV without sacrificing signal strength through parallel image acquisition. Towards quantitative angiography, the ‘frequency flow’ imaging ...

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    2. Inspection of Intraocular Lens with Dual-side View Optical Coherence Tomography

      Inspection of Intraocular Lens with Dual-side View Optical Coherence Tomography

      Intraocular lens (IOL) is widely used for cataract treatment. Its optical properties are crucial to obtain a good treatment efficacy and thus need to be evaluated and controlled. In this study, we propose a novel method based on optical coherence tomography (OCT) for noncontact and accurate in vitro measurement of thickness, refractive index and dioptric power of IOL implants. The OCT setup is specially designed to create two sampling optics, called dual-side view OCT (DSV-OCT), which allows for imaging IOL from the two opposite sides simultaneously in single OCT volume scanning. This can produce a three-dimensional surface contour without suffering ...

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    3. Cross‐Domain Retinopathy Classification with Optical Coherence Tomography Images via a Novel Deep Domain Adaptation Method

      Cross‐Domain Retinopathy Classification with Optical Coherence Tomography Images via a Novel Deep Domain Adaptation Method

      Deep learning based retinopathy classification with optical coherence tomography (OCT) images has recently attracted great attention. However, existing deep learning methods fail to work well when training and testing datasets are different due to the general issue of domain shift between datasets caused by different collection devices, subjects, imaging parameters, etc. To address this practical and challenging issue, we propose a novel deep domain adaptation (DDA) method to train a model on a labelled dataset and adapt it to an unlabelled dataset (collected under different conditions). It consists of two modules for domain alignment, i.e., adversarial learning and entropy ...

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    4. Automatic detection of retinopathy with optical coherence tomography images via a semi-supervised deep learning method

      Automatic detection of retinopathy with optical coherence tomography images via a semi-supervised deep learning method

      Automatic detection of retinopathy via computer vision techniques is of great importance for clinical applications. However, traditional deep learning based methods in computer vision require a large amount of labeled data, which are expensive and may not be available in clinical applications. To mitigate this issue, in this paper, we propose a semi-supervised deep learning method built upon pre-trained VGG-16 and virtual adversarial training (VAT) for the detection of retinopathy with optical coherence tomography (OCT) images. It only requires very few labeled and a number of unlabeled OCT images for model training. In experiments, we have evaluated the proposed method ...

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    5. Imaging sebaceous gland using optical coherence tomography with deep learning assisted automatic identification

      Imaging sebaceous gland using optical coherence tomography with deep learning assisted automatic identification

      Imaging sebaceous glands and evaluating morphometric parameters are important for diagnosis and treatment of serum problems. In this paper, we investigate the feasibility of high‐resolution optical coherence tomography (OCT) in combination with deep learning assisted automatic identification for these purposes. Specifically, with a spatial resolution of 2.3 μm × 6.2 μm (axial × lateral, in air), OCT is capable of clearly differentiating sebaceous gland from other skin structures and resolving the sebocyte layer. In order to achieve efficient and timely imaging analysis, a deep learning approach built upon ResNet18 is developed to automatically classify OCT images (with/without sebaceous ...

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    6. Evaluation of ultrahigh-resolution optical coherence tomography for basal cell carcinoma, seborrheic keratosis, and nevus

      Evaluation of ultrahigh-resolution optical coherence tomography for basal cell carcinoma, seborrheic keratosis, and nevus

      Background: Basal cell carcinoma, seborrheic keratosis, and nevus are common skin conditions. Though most of the skin diseases can be distinguished from each other by physician's naked eyes, the diagnostic accuracy is not 100%. The accurate diagnosis and assessment of three diseases make a big difference on the clinical management. Nowadays, biopsy is still the gold standard for diagnosis even it is invasive, time-consuming, and painful. Ultrahigh-resolution optical coherence tomography is an emerging technology that can produce in situ, cellular-resolution, real-time, continuous, 3D images in a noninvasive way. Materials and methods: In our study, four basal cell carcinoma patients ...

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    7. Towards Indicating Human Skin State In Vivo Using Geometry-Dependent Spectroscopic Contrast Imaging

      Towards Indicating Human Skin State In Vivo Using Geometry-Dependent Spectroscopic Contrast Imaging

      Skin plays a significant role in human body function and its collagen states change during the human skin ageing process, which affects skin function. We previously reported on geometry-dependent spectroscopic contrast achieved by spectroscopic micro-optical coherence tomography ( S μ OCT), which discovered that transversely oriented and regularly arranged nano-cylinders selectively backscatter the long-wavelength lights and generate spectral centroid (SC) shifts towards the long wavelengths within a spectral window of 700 − 950 nm . Here we further proposed a novel method towards indicating the state of human skin in vivo using geometry-dependent spectroscopic contrast imaging. The proposed method can obtain spectroscopic contrast images ...

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    8. Automatic differentiation of nonkeratinized stratified squamous epithelia and columnar epithelia through feature structure extraction using OCT

      Automatic differentiation of nonkeratinized stratified squamous epithelia and columnar epithelia through feature structure extraction using OCT

      As a type of precancerous lesion, metaplasia is usually considered to be associated with developing cancer. In clinical practice, surveillance of metaplastic cases usually relies on excisional biopsy followed by histological processing and analysis. As it is an invasive method accompanied by other complications, non-invasive imaging methods such as optical coherence tomography (OCT) can complement the existing method by enabling large area scanning. However, because it takes time to review large amount of data acquired from the whole suspected mucosal areas, an automatic classification method is preferred to alleviate the laboring hours and to avoid ‘sampling errors’ during image analysis ...

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    9. Resolution enhancement and realistic speckle recovery with generative adversarial modeling of micro-optical coherence tomography

      Resolution enhancement and realistic speckle recovery with generative adversarial modeling of micro-optical coherence tomography

      A resolution enhancement technique for optical coherence tomography (OCT), based on Generative Adversarial Networks (GANs), was developed and investigated. GANs have been previously used for resolution enhancement of photography and optical microscopy images. We have adapted and improved this technique for OCT image generation. Conditional GANs (cGANs) were trained on a novel set of ultrahigh resolution spectral domain OCT volumes, termed micro-OCT, as the high-resolution ground truth (∼1 µm isotropic resolution). The ground truth was paired with a low-resolution image obtained by synthetically degrading resolution 4x in one of (1-D) or both axial and lateral axes (2-D). Cross-sectional image (B-scan ...

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    10. Dual-side view optical coherence tomography for thickness measurement on opaque materials

      Dual-side view optical coherence tomography for thickness measurement on opaque materials

      Optical coherence tomography (OCT), as an optical interferometric imaging technique, has found wide applications in various fields. In principle, OCT is well suited for imaging layered structures, and thus, one of the typical applications is thickness measurement. However, due to the limited imaging depth resulting from light attenuation, thickness measurement by OCT is limited to non-opaque materials. In this study, we developed a novel (to the best of our knowledge) dual-side view OCT (DSV-OCT) system for thickness measurement on opaque materials. The dual-side view was achieved on a conventional swept source OCT platform by creating two symmetrical sampling arms. This ...

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    11. Feasibility evaluation of micro-optical coherence tomography (μOCT) for rapid brain tumor type and grade discriminations: μOCT images versus pathology

      Feasibility evaluation of micro-optical coherence tomography (μOCT) for rapid brain tumor type and grade discriminations: μOCT images versus pathology

      Background Precise identification, discrimination and assessment of central nervous system (CNS) tumors is of critical importance to brain neoplasm treatment. Due to the complexity and limited resolutions of the existing diagnostic tools, however, it is difficult to identify the tumors and their boundaries precisely in clinical practice, and thus, the conventional way of brain neoplasm treatment relies mainly on the experiences of neurosurgeons to make resection decisions in the surgery process. The purpose of this study is to explore the potential of Micro-optical coherence tomography (μOCT) as an intraoperative diagnostic imaging tool for identifying and discriminating glioma and meningioma with ...

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    12. Interferometer-in-Spectrometer for High-Resolution Optical Coherence Tomography

      Interferometer-in-Spectrometer for High-Resolution Optical Coherence Tomography

      Ultrahigh-resolution optical coherence tomography provides an axial resolution of 1-2  μ m for resolving cellular structures of biological tissues critical for the diagnosis of diseases. However, it requires a relatively large spectral bandwidth which is not supported by the key components of the imaging system. We propose a novel spectral-domain OCT design, termed interferometer-in-spectrometer, which is able to compensate the bandwidth limitations of the grating and the line scan sensor by spectral shaping without compromising the signal intensity and adding the system cost. The advantage of axial resolution and ranging depth over the standard design is experimentally validated using the standard ...

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    13. Postdoctoral Position Opening in High Resolution OCT at Nanyang Technological University

      Postdoctoral Position Opening in High Resolution OCT at Nanyang Technological University

      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 (publications ...

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    14. 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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    15. 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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    16. 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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    17. 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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    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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    23. 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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    24. 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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    1-24 of 74 1 2 3 »
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