Browsing by Subject "Optical fibers in medicine"

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Biomedical applications of a fiber based low-coherence interferometer for quantitative differential phase measurements
(2003) Akkin, Taner; Milner, Thomas E.; Rylander, H. Grady, (Henry Grady), 1948-
This dissertation presents design, implementation, and biomedical applications of a novel polarization-maintaining-fiber based phase sensitive optical low-coherence reflectometer (PS-OLCR). Using dual channels, PS-OLCR detects Angstrom/nanometer scale optical path length changes by calculating phase difference between depth resolved interference fringes. Ability to detect such small changes in optical path length at specific depths is useful in a wide variety of biomedical imaging and sensing applications. Application areas investigated in this dissertation include (i) measurement of analyte concentrations, (ii) imaging surface topography, (iii) cartilage surface response to electrical stimulation, (iv) arterial tissue response to photothermal stimulation, (v) birefringence measurement, and (vi) optical detection of neural activity. For each application, results of PS-OLCR differential phase measurements are presented.
Fiber optic confocal microscope: in vivo precancer detection
(2006) Carlson, Kristen Dawn; Richards-Kortum, Rebecca, 1964-; Solgaard, Olav
Cancer is a significant public health problem worldwide. Many cancers originate as precancerous lesions in the epithelium which, when removed in sufficient time, can prevent progression to cancer. However, current detection techniques are typically timeconsuming and expensive, limiting their acceptance and accessibility. Optical techniques, such as confocal microscopy, have significant potential to provide clinicians with real-time, high-resolution images of cells and tissue without tissue removal. These images of cell morphology and tissue architecture can be used to characterize tissue and determine the presence or extent of precancer and cancer. This dissertation explores the instrumentation and application of fiber optic reflectance confocal microscopy for in vivo precancer detection. The first part of the dissertation presents in vivo imaging of suspicious lesions in the human uterine cervix and oral mucosa using a fiber bundle based confocal microscope with a complex glass miniature objective lens. Images are analyzed quantitatively and qualitatively to determine the potential of this technology in vivo. An analysis of nuclear density from vii images of 30 cervical epithelium sites shows differentiation between normal and precancerous sites. Similarly, images from 20 oral mucosa sites demonstrate changes in nuclear density and tissue architecture indicative of progression of precancer and cancer. In addition to this multi-fiber confocal microscope used with a glass objective lens for the clinical studies, imaging of tissue samples has been accomplished with the same confocal system using an injection molded plastic miniature objective lens demonstrating comparable optical quality for a significantly less expensive optical component. Finally, a benchtop prototype of a single fiber confocal microscope using a gimbaled two-axis MEMS scanner has been designed and constructed. Imaging of a resolution target and cellular samples demonstrates sufficient resolution and field of view for cellular imaging. The results from the imaging studies presented here indicate that in vivo confocal microscopy has the potential to improve early precancer detection in epithelial tissue. Advances in imaging technology will continue to reduce the cost of imaging systems and improve the imaging capability, leading to an inexpensive, real-time, minimally-invasive tool for in vivo imaging.
Fiber optic confocal reflectance microscopy: in vivo detection of pre-cancerous lesions in epithelial tissue
(2003) Sung, Kung-bin; Richards-Kortum, Rebecca, 1964-
This dissertation describes the development of a fiber optic confocal reflectance microscope for imaging cell nuclei in cervical epithelium and oral mucosa in vivo. The ultimate goal of this research is to construct a non-invasive confocal imaging system to aid in the detection of pre-cancerous lesions in epithelial tissue. Confocal microscopy is a technique capable of imaging individual cells and cell nuclei within tissue by spatially isolating and detecting light from a small focal volume in the tissue. In vivo confocal images have only been obtained from skin and the lip due to the accessibility of these organs with conventional microscopes. Fiber optic confocal fluorescence microscopes with miniaturized objectives have been presented and used to obtain in vivo images from animal models. However, the choice of nontoxic fluorescent dyes suitable for clinical applications remains to be explored. A bench-top fiber optic confocal imaging system was designed and constructed to assess the feasibility of obtaining reflectance images of epithelial cells at 15 frames per second through a flexible fiber optic bundle. The performance of the bench-top system was tested by imaging standard samples and biological specimens. The spatial resolution and sensitivity were sufficient to permit imaging of sub-cellular structures in epithelial tissue. The in vivo imaging capability was achieved by incorporating a miniaturized objective lens and an axial scanning device into the system. Similar spatial resolution and sensitivity were obtained. The modified system was used in a pilot in vivo study: “Reflectance Confocal Imaging of Cervical Intraepithelial Neoplasia (CIN)”. The study protocol was approved by the Institutional Review Board at the University of Texas at Austin, and written informed consent was obtained from each of the participating patients before the experiments began. Images of cell nuclei were obtained from 15 cervical sites in 9 patients. Average nuclear size, nuclear-cytoplasmic ratio and scattering coefficient were measured from images of normal cervical epithelium and compared well with results from existing in vitro studies. The results described in this dissertation indicate that this technique can potentially improve early detection of precancers.