1. Articles from DR-NTU HOME

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    1. Optical reflectance contrast of micro- and nano-structures revealed with intravital micro-OCT (Thesis)

      Optical reflectance contrast of micro- and nano-structures revealed with intravital micro-OCT (Thesis)

      Optical coherence tomography (OCT) provides depth-resolved three-dimensional images allowing the visualization of subsurface microstructures over large areas in situ and thus is a promising tool for epithelial disease screening. However, it has generally been relegated to a nonspecific diagnostic tool because the optical reflectance (back-scattering) contrast in OCT images is poorly understood although some contrast agents are available for OCT. This thesis focuses on elucidating the microstructural and ultrastructural bases underlying optical contrast to explore if OCT could provide diagnostic information in epithelial tissues with specificity. We investigate the back-scattered intensity of different intracellular scatterers at the micrometer and nanometer ...

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    2. Extending depth range of optical coherence tomography (Thesis)

      Extending depth range of optical coherence tomography (Thesis)

      Optical coherence tomography (OCT) is a noninvasive diagnostic imaging tool that has been established in various clinical fields. One of the most cited issue of OCT in clinical practices is the shortage of image depth range. This thesis proposes four novel techniques to significantly extend the depth range without compromising other imaging performances. The OCT depth range is fundamentally limited by two main factors, which are the axial field of view (FOV) and the system sensitivity. For standard OCT systems, the axial FOV can only be improved by decreasing the numerical aperture (NA) of the focusing optics, which unfortunately sacrifices ...

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    3. Characterization of biofouling with 3D-printed spacers using 3D optical coherence tomography (Thesis)

      Characterization of biofouling with 3D-printed spacers using 3D optical coherence tomography (Thesis)

      Biofouling in membrane filtration is a common occurrence which impedes the efficiency of the separation process. By looking into the biofouling mechanisms via the observation of a filtration process, potential problems can be addressed and resolved. This study uses optical coherence tomography (OCT) to investigate the effects of using different 3D-printed spacers on the biofouling process. A compilation of OCT scans of a representative unit cell of each spacer was taken as a function of time to generate 3D-images showing the morphology of a foulant layer. Through the usage of various quantitative analysing methods (such as EIS, DOTM and etc ...

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    4. Improving optical coherence tomography theories and techniques for advanced performance and reduced cost (Thesis)

      Improving optical coherence tomography theories and techniques for advanced performance and reduced cost (Thesis)

      Optical coherence tomography (OCT) has been developed as a high-resolution three-dimensional imaging technique for clinical diagnosis. This thesis proposes several theoretical discoveries and technical improvements to the current OCT systems aiming to drastically reduce system costs while achieving the state-of-the-art performance. Polarization-sensitive OCT (PS-OCT) is a functional extension of conventional OCT which offers the depth-resolved birefringence imaging capability. To resolve local retardation in tissue samples, the current PS-OCT system employs two multiplexed polarization states to illuminate the sample under investigation and detects the backscattered light with two detection channels. We observed that the polarization state of light after round-trip propagation ...

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    5. Development of cellular resolution optical coherence tomography (Thesis)

      Development of cellular resolution optical coherence tomography (Thesis)

      Diagnosis of most mucosal diseases including epithelial cancers relies on white-light endoscopy/visual inspection followed by random biopsy and histologic examination. These current standard-of-care tools are associated with many issues such as sampling errors, tissue destruction, and processing artifacts. In addition, it is too traumatic to take a biopsy from tissues like eyes and coronary arteries. Being high resolution, high speed, and non-invasive, optical coherence tomography (OCT) has emerged as an endoscopic and intravascular imaging tool that provides valuable anatomic information complementary to the standard-of-care techniques. However, it has a typical resolution of 10 μm, which is too coarse to ...

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    6. Investigation of low coherence interferometry techniques for biomedical applications (Thesis)

      Investigation of low coherence interferometry techniques for biomedical applications (Thesis)

      Interferometric techniques have been used as imaging techniques in many applications. In using low coherence sources in interferometry, good axial resolution can be achieved. The objective of this thesis is to investigate the use low coherence interferometry in biomedical applications. Low coherence interferometry (LCI) was incorporated into an optical tweezers system to determine the trapping dynamics. An optical coherence tomography (OCT) system based on LCI principles was designed and implemented to detect virus infection in orchid leaves. The OCT system was then modified to realize a high-speed endoscopic OCT imaging system. A numerical method and a common-path probe design were ...

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    1-6 of 6
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