1. Articles from Yuemei Luo

    1-16 of 16
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. Depth-of-focus extension in optical coherence tomography via multiple aperture synthesis

      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 ∼10 times larger than the ...

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    9. Multifiber angular compounding optical coherence tomography for speckle reduction

      Multifiber angular compounding optical coherence tomography for speckle reduction

      We report on an integrated fiber optic design to implement multifiber angular compounding optical coherence tomography, which enables angular compounding for speckle reduction. A multi-facet fiber array delivers three light beams to the sample with different incident angles. Back-reflective/back-scattered signals from these channels were simultaneously detected by a three-channel spectrometer. The axial and lateral resolution was measured to be ∼ 3 ∼3 and ∼ 3.5    μm ∼3.5  μm , respectively, in air with ∼ 100    dB ∼100  dB sensitivity. We conducted ex vivo experiments on a rat esophagus to demonstrate a contrast to noise improvement of 1.58.

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    10. Contrast Enhanced Subsurface Fingerprint Detection using High-speed Optical Coherence Tomography

      Contrast Enhanced Subsurface Fingerprint Detection using High-speed Optical Coherence Tomography

      Spectral-domain optical coherence tomography (SDOCT) has been demonstrated to be a viable tool in forensic science for fingerprint detection, yet it still suffers from certain practical issues, e.g., the limited scanning speed and low image contrast. In this letter, we report a high-speed SD-OCT together with an image contrast enhancement mechanism for reliable subsurface fingerprint detection. The constructed SDOCT system achieves a scanning rate up to 60K A-lines/s, and thus, both 3D volumetric images, reaching up to 20mm × 20mm × 1.2mm, and en face internal fingerprint furrow pattern images could be obtained. Based upon the analyses of the ...

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    11. Toward High-Speed Imaging of Cellular Structures in Rat Colon Using Micro-optical Coherence Tomography

      Toward High-Speed Imaging of Cellular Structures in Rat Colon Using Micro-optical Coherence Tomography

      The mucosal microanatomy of the large intestine is characterized by the presence of crypts of Lieberkühn, which is associated predominantly with goblet cells. Such cellular-level intestinal microstructures undergo morphological changes during the progression of bowel diseases, such as colon cancer or ulcerative colitis. As an indicator of gastric cancers, intestinal metaplasia in the large intestine is characterized by the appearance of goblet cells in gastric epithelium, and therefore, visualization of intestinal microstructure changes in cross-sectional view, particularly in vivo, in a highspeed fashion would assist early disease diagnosis and its treatment. In this paper, we investigated the capability of ...

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    12. Spectral domain optical coherence tomography with dual-balanced detection

      Spectral domain optical coherence tomography with dual-balanced detection

      We developed a spectral domain optical coherence tomography (SD-OCT) system employing dual-balanced detection (DBD) for direct current term suppression and SNR enhancement, especially for auto-autocorrelation artifacts reduction. The DBD was achieved by using a beam splitter to building a free-space Michelson interferometer, which generated two interferometric spectra with a phase difference of π. These two phase-opposed spectra were guided to the spectrometer through two single mode fibers of the 8 fiber v-groove array and acquired by ultizing the upper two lines of a three-line CCD camera. We rotated this fiber v-groove array by 1.35 degrees to focus two spectra onto ...

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    13. High-resolution extended source optical coherence tomography

      High-resolution extended source optical coherence tomography

      High resolution optical coherence tomography (OCT) is capable of providing detailed tissue microstructures that are critical for disease diagnosis, yet its sensitivity is usually degraded since the system key components are typically not working at their respective center wavelengths. We developed a novel imaging system that achieves enhanced sensitivity without axial resolution degradation by the use of a spectrally encoded extended source (SEES) technique; it allows larger sample power without exceeding the maximum permissible exposure (MPE). In this study, we demonstrate a high-resolution extended source (HRES) OCT system, which is capable of providing a transverse resolution of 4.4 µm ...

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    14. One-micron resolution optical coherence tomography (OCT) in vivo for cellular level imaging

      One-micron resolution optical coherence tomography (OCT) in vivo for cellular level imaging

      We developed a spectral domain OCT system combining two NIR, CW light sources of different spectral range. Its resolving power is validated by visualizing the cellular structures of zebra fish larvae in vivo. An NIR extended illumination from 755-1100 nm is achieved. The axial resolution is 1.27 μm in air, corresponding to 0.93μm in tissue (n=1.36), which is the highest axial resolution using NIR, CW laser sources up to date to the best of our knowledge. In vivo imaging is conducted to demonstrate the resolving power of proposed one-micron resolution OCT system. The top and ...

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    15. Dual spectrometer system with spectral compounding for 1 um optical coherence tomography in vivo

      Dual spectrometer system with spectral compounding for 1 um optical coherence tomography in vivo

      1 μm axial resolution spectral domain optical coherence tomography (OCT) is demonstrated for in vivo cellular resolution imaging. Output of two superluminescent diode sources is combined to provide near infrared illumination from 755 to 1105 nm. The spectral interference is detected using two spectrometers based on a Si camera and an InGaAs camera, respectively. Spectra from the two spectrometers are combined to achieve an axial resolution of 1.27 μm in air. Imaging was conducted on zebra fish larvae to visualize cellular details.

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    1-16 of 16
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    Dual spectrometer system with spectral compounding for 1 um optical coherence tomography in vivo One-micron resolution optical coherence tomography (OCT) in vivo for cellular level imaging Spectral domain optical coherence tomography with dual-balanced detection Toward High-Speed Imaging of Cellular Structures in Rat Colon Using Micro-optical Coherence Tomography Contrast Enhanced Subsurface Fingerprint Detection using High-speed Optical Coherence Tomography Single-camera full-range high-resolution spectral domain optical coherence tomography 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 Multiple aperture synthetic optical coherence tomography for biological tissue imaging Evaluating micro-optical coherence tomography (μOCT) as a feasible imaging tool for pancreatic disease diagnosis Optos, Bühler, Lumishore among latest Queen's Award winners Capabilities of Gabor-domain optical coherence microscopy for the assessment of corneal disease