This thesis outlines two advancements in the field of limited data absorption tomography. First, a novel reconstruction algorithm integrating the use of level set methods is presented that incorporates the additional a priori knowledge of a distinct interface between the species of interest and co-flow. The added a priori further reduces the ill-posedness of the system to produce a final concentration distribution that explains the laser absorption measurements and is qualitatively consistent with advection/diffusion transport. The algorithm is demonstrated by solving a simulated laser tomography experiment on a turbulent methane plume, and is compared with the current state-of-the-art reconstruction algorithm. Given the limited number of attenuated measurements, accurate reconstructions are also highly dependent on the locations sampled by the measurement array. This thesis displays how the mathematical properties of the coefficient matrix, A, formed by the locations of the lasers, are related to the information content of the attenuation data using a Tikhonov reconstruction framework. This formulation, in turn, becomes a basis for a beam arrangement design algorithm that minimizes the reliance on additional assumed information about the concentration distribution. Using genetic algorithms, beam arrangements can be optimized for a given application by incorporating physical constraints of the beam locations. The algorithm is demonstrated by optimizing unconstrained and constrained arrangements of light sources and detectors. Simulated experiments are performed to validate the optimality of the arrangements.

I experimentally studied ultrasound-modulated optical tomography, which holds the promise for biomedical diagnosis. I measured the degree of polarization of laser speckles generated by scattered light transmitted through turbid media, investigated three signal-detection schemes for extracting the intensity of the ultrasound-modulated light, carried out experiments to image thick biological-tissue samples, and studied two techniques providing resolution in the cross-sections containing the ultrasonic axis. The study of degree of polarization presented results important for the understanding of polarization phenomena in turbid media. I explored an optical-filtering based signal detection scheme, improved the parallel-lock-in speckle detection scheme and proposed a speckle-contrast detection scheme. With the speckle-contrast detection scheme, I successfully obtained images of biological-tissue samples up to 50 mm thick. Further I studied frequency-swept ultrasound-modulated optical tomography for sub-millimeter resolution imaging, and developed ultrasound-modulated optical computed tomography that was based on a back-projection image reconstruction method and obtained clear images of biological-tissue samples.

Die moderne multimodale Computertomografie (CT) beinhaltet das Schichtröntgen des Gehirns (native CT), die Darstellung der hirnversorgenden Arterien (CT-Angiografie) und die Messung der Hirndurchblutung (CT-Perfusion). Mit Hilfe dieser Untersuchungstechnik kann bei Patienten mit akutem Schlaganfall rasch die Ursache der plötzlich eingesetzten Symptome beleuchtet werden: Liegt eine Gefäßobstruktion oder eine Blutung in das Gehirn vor? Wie ausgedehnt ist die Durchblutungsstörung und wie viel Hirngewebe ist bereits beschädigt bzw. vom Untergang bedroht? Anhand dieser Informationen kann sofort eine spezifische Therapie eingeleitet werden, die es ermöglicht, die Patienten vor dauerhafter schwerer Behinderung zu bewahren bzw. die Prognose schon früh abzuschätzen. / Computed tomography (CT), including CT perfusion imaging and CT angiography, has the capacity to assess stroke pathology on a functional and morphological level and can thus provide important information about patients with acute stroke. It excludes brain haemorrhage, assesses the extent of perfusion deficit, the extent of ischemic damage, and the site and type of arterial obstruction. Ischemic brain tissue below the blood flow level of structural integrity takes up water immediately and causes a decrease in x-ray attenuation. Computed tomography thus has the specific advantage of being able to identify the brain tissue which is irreversibly injured. If CT can exclude major ischemic damage in acute stroke patients, reperfusion strategies may rescue brain function and prevent disability.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on Jan. 20, 2010. Major professor: Dr. Dennis Derickson. "Presented to the Electrical Engineering Department faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Electrical Engineering." "December, 2009." Includes bibliographical references (p. 111).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 152-162). Available also in a digital version from Dissertation Abstracts.

Optical Coherence Tomography (OCT) is an optical tomography technique which provides high resolution non-invasive three-dimensional (3D) structural images of the sample based on coherent properties of light. The dissertation focuses on the use of OCT systems for detecting glaucoma, which is the second leading cause of blindness worldwide. First, as a prerequisite of analyzing ophthalmologic OCT images, a retinal sublayer segmentation algorithm is presented and implemented with GPU assisted computation. Then, a polarization-sensitive optical coherence tomography (PS-OCT) system was constructed for the study of glaucoma. Three closely related clinical and animal studies on early-stage glaucoma detection using either OCT or PS-OCT were performed. Statistical analysis of the study results indicates that the scattering property of retinal nerve fiber layer (RNFL) is the earliest indicator for glaucoma. Finally, to investigate the scattering properties of RNFL, a pathlength-multiplexed scattering-angle-diverse optical coherence tomography (PM-SAD-OCT) system was designed and built. PM-SAD-OCT images were collected from human and rodent retina as well as earthworm nerve cord. PM-SAD-OCT system shows promising potentials to detect neurodegenerative diseases including glaucoma. / text

Not available / text

Not available / text

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

No description available.