1. Articles from Qingyun Li

    1-11 of 11
    1. Investigating Local Polarisation Contrast With Fibre-Based Polarisation-Sensitive Optical Coherence Tomography and Microscopy (Thesis)

      Investigating Local Polarisation Contrast With Fibre-Based Polarisation-Sensitive Optical Coherence Tomography and Microscopy (Thesis)

      This thesis makes several important contributions to polarisation-sensitive optical coherence tomography (PS-OCT) through developing no el methods to effectively extract local contrast from birefringence and the orientation of the associated optic axis, at conventional and ultra-high resolution.

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    2. Jones matrix‐based speckle‐decorrelation angiography using polarization‐sensitive optical coherence tomography

      Jones matrix‐based speckle‐decorrelation angiography using polarization‐sensitive optical coherence tomography

      We show that polarization‐sensitive optical coherence tomography angiography (PS‐OCTA) based on full Jones matrix assessment of speckle decorrelation offers improved contrast and depth of vessel imaging over conventional OCTA. We determine how best to combine the individual Jones matrix elements and compare the resulting image quality to that of a conventional OCT scanner by co‐locating and imaging the same skin locations with closely matched scanning setups. Vessel projection images from finger and forearm skin demonstrate the benefits of Jones matrix‐based PS‐OCTA. Our study provides a promising starting point and a useful reference for future pre ...

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    3. Vectorial birefringence imaging by optical coherence microscopy for assessing fibrillar microstructures in the cornea and limbus

      Vectorial birefringence imaging by optical coherence microscopy for assessing fibrillar microstructures in the cornea and limbus

      The organization of fibrillar tissue on the micrometer scale carries direct implications for health and disease but remains difficult to assess in vivo . Polarization-sensitive optical coherence tomography measures birefringence, which relates to the microscopic arrangement of fibrillar tissue components. Here, we demonstrate a critical improvement in leveraging this contrast mechanism by employing the improved spatial resolution of focus-extended optical coherence microscopy (1.4 µm axially in air and 1.6 µm laterally, over more than 70 µm depth of field). Vectorial birefringence imaging of sheep cornea ex vivo reveals its lamellar organization into thin sections with distinct local optic axis ...

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    4. Depth-resolved birefringence imaging of collagen fiber organization in the human oral mucosa in vivo

      Depth-resolved birefringence imaging of collagen fiber organization in the human oral mucosa in vivo

      Stromal collagen organization has been identified as a potential prognostic indicator in a variety of cancers and other diseases accompanied by fibrosis. Changes in the connective tissue are increasingly considered for grading dysplasia and progress of oral squamous cell carcinoma, investigated mainly ex vivo by histopathology. In this study, polarization-sensitive optical coherence tomography (PS-OCT) with local phase retardation imaging is used for the first time to visualize depth-resolved (i.e., local) birefringence of healthy human oral mucosa in vivo . Depth-resolved birefringence is shown to reveal the expected local collagen organization. To demonstrate proof-of-principle, 3D image stacks were acquired at labial ...

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    5. Robust reconstruction of local optic axis orientation with fiber-based polarization-sensitive optical coherence tomography

      Robust reconstruction of local optic axis orientation with fiber-based polarization-sensitive optical coherence tomography

      It is challenging to recover local optic axis orientation from samples probed with fiber-based polarization-sensitive optical coherence tomography (PS-OCT). In addition to the effect of preceding tissue layers, the transmission through fiber and system elements, and imperfect system alignment, need to be compensated. Here, we present a method to retrieve the required correction factors from measurements with depth-multiplexed PS-OCT, which accurately measures the full Jones matrix. The correction considers both retardation and diattenuation and is applied in the wavenumber domain, preserving the axial resolution of the system. The robustness of the method is validated by measuring a birefringence phantom with ...

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    6. A study of the effects of supine position and fluid intake on normal airway geometry using anatomical optical coherence tomography

      A study of the effects of supine position and fluid intake on normal airway geometry using anatomical optical coherence tomography

      Airway inhalation injuries are present in up to a third of all major burns patients and are the leading cause of mortality among this population. Understanding the mechanism of injury could minimise oedema (swelling) and airway damage. In this study, we present an anatomical OCT (aOCT) imaging system, based on a 1300-nm wavelength, high-speed, long-range MEMS-VCSEL swept laser source, for real-time volumetric imaging and assessment of inhalation injuries in airways up to 3 cm in diameter. A custom fibre-optic probe with GRIN lens and micro prism is inserted though the nasal passage. Airway cross-sectional images acquired are used to assess ...

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    7. Dark-field polarization-sensitive optical coherence tomography

      Dark-field polarization-sensitive optical coherence tomography

      Polarization-sensitive optical coherence tomography (PS-OCT) is a functional OCT providing both structural and birefringent information of the sample, and it has been applied to the studies of various organs having polarization properties. Fiber-based PS-OCT is sensitive to specular reflection from the sample surface, because signal saturation due to the strong specular reflection can make the polarization measurement difficult. We developed a dark-field PS-OCT which can avoid the specular reflection problem. Dark-field PS-OCT was implemented by adapting a hybrid method of Bessel-beam illumination and Gaussian-beam detection, and a PS-OCT method based on passive delay unit (PDU). The new system was characterized ...

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    8. In vivo wide-field reflectance/fluorescence imaging and polarization-sensitive optical coherence tomography of human oral cavity with a forward-viewing probe

      In vivo wide-field reflectance/fluorescence imaging and polarization-sensitive optical coherence tomography of human oral cavity with a forward-viewing probe

      We report multimodal imaging of human oral cavity in vivo based on simultaneous wide-field reflectance/fluorescence imaging and polarization-sensitive optical coherence tomography (PS-OCT) with a forward-viewing imaging probe. Wide-field reflectance/fluorescence imaging and PS-OCT were to provide both morphological and fluorescence information on the surface, and structural and birefringent information below the surface respectively. The forward-viewing probe was designed to access the oral cavity through the mouth with dimensions of approximately 10 mm in diameter and 180 mm in length. The probe had field of view (FOV) of approximately 5.5 mm in diameter, and adjustable depth of field (DOF ...

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    9. Gradient index lens based combined two-photon microscopy and optical coherence tomography

      Gradient index lens based combined two-photon microscopy and optical coherence tomography

      We report a miniaturized probe-based combined two-photon microscopy (TPM) and optical coherence tomography (OCT) system. This system is to study the colorectal cancer in mouse models by visualizing both cellular and structural information of the colon in 3D with TPM and OCT respectively. The probe consisted of gradient index (GRIN) lenses and a 90° reflecting prism at its distal end for side-viewing, and it was added onto an objective lens-based TPM and OCT system. The probe was 2.2 mm in diameter and 60 mm in length. TPM imaging was performed by raster scanning of the excitation focus at the ...

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    10. Detection of pH-induced aggregation of "smart" gold nanoparticles with photothermal optical coherence tomography

      Detection of pH-induced aggregation of "smart" gold nanoparticles with photothermal optical coherence tomography

      We report the feasibility of a novel contrast agent, namely “smart” gold nanoparticles (AuNPs), in the detection of cancer cells with photothermal optical coherence tomography (PT-OCT). “Smart” AuNPs form aggregation in low pH condition, which is typical for cancer cells, and this aggregation results in a shift of their absorption spectrum. A PT-OCT system was developed to detect this pH-induced aggregation by combining an OCT light source and a laser with 660 nm in wavelength for photothermal excitation. Optical detection of pH-induced aggregation was tested with solution samples at two different pH conditions. An increase in optical path length (OPL ...

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    11. Combined two-photon microscopy and angiographic optical coherence tomography

      Combined two-photon microscopy and angiographic optical coherence tomography

      A combined two-photon microscopy (TPM) and angiographic optical coherence tomography (OCT) is developed, which can provide molecular, cellular, structural, and vascular information of tissue specimens in vivo . This combined system is implemented by adding an OCT vasculature visualization method to the previous combined TPM and OCT, and then is applied to in vivo tissue imaging. Two animal models, a mouse brain cranial window model and a mouse ear cancer model, are used. Both molecular, cellular information at local regions of tissues, and structural, vascular information at relatively larger regions are visualized in the same sections. In vivo tissue microenvironments are ...

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    1-11 of 11
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  2. Topics in the News

    1. (6 articles) University of Western Australia
    2. (5 articles) Ki Hean Kim
    3. (5 articles) Karol Karnowski
    4. (5 articles) David D. Sampson
    5. (3 articles) Gwangju Institute of Science and Technology
    6. (3 articles) Martin L. Villiger
    7. (3 articles) Taejun Wang
    8. (2 articles) Yonsei University
    9. (2 articles) Harvard University
    10. (2 articles) Chulmin Joo
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    Combined two-photon microscopy and angiographic optical coherence tomography Detection of pH-induced aggregation of "smart" gold nanoparticles with photothermal optical coherence tomography Gradient index lens based combined two-photon microscopy and optical coherence tomography In vivo wide-field reflectance/fluorescence imaging and polarization-sensitive optical coherence tomography of human oral cavity with a forward-viewing probe Dark-field polarization-sensitive optical coherence tomography A study of the effects of supine position and fluid intake on normal airway geometry using anatomical optical coherence tomography Robust reconstruction of local optic axis orientation with fiber-based polarization-sensitive optical coherence tomography Depth-resolved birefringence imaging of collagen fiber organization in the human oral mucosa in vivo Vectorial birefringence imaging by optical coherence microscopy for assessing fibrillar microstructures in the cornea and limbus Investigating Local Polarisation Contrast With Fibre-Based Polarisation-Sensitive Optical Coherence Tomography and Microscopy (Thesis) Medical treatment of inflammatory punctual stenosis monitored by anterior segment optical coherence tomography Development and Validation of a Deep Learning System for Diagnosing Glaucoma Using Optical Coherence Tomography