Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Phillip E. Pace, Don Brutzman. Includes bibliographical references (p. 129-130). Also available online.

Computational imaging is an emerging field. Its rapid development has drawn tremendous attention from both research and commercial points of view. Unlike traditional imaging, which separately considers the optical imaging and computational processing, computational imaging combines the power of the optical elements and signal processing techniques to achieve augmented capabilities. Previous work on various aspects of computational imaging has shown the powerful abilities that computations can bring into the imaging systems. However, the research is still in an early stage. Some drawbacks need to be conquered. For example, in compressed sensing (CS) related systems, the reconstruction quality cannot be satisfactory due to the ill-posed nature of the problem. Likely, in computational photography, the systems share a major defect. That is, as four-dimensional radiance information is recorded by a regular two-dimensional sensor, an unavoidable sacrifice of the spatial resolution has to be made to resolve angular differences. This eventually causes the low spatial resolution output. To meet these challenges, more efforts have to be made in both imaging part and computational part. In this dissertation, we concentrate ourselves on a more specific form of computational imaging, i.e., mask-based coded imaging systems. In particular, the first part of the dissertation focuses on a mask-based terahertz (THz) CS imaging system. There we focus on the computational part and explore the reconstruction algorithms that can estimate the underlying scene as accurately as possible. After that, we discuss the lightfield photography and show that by combining the system modification and proper postprocessing algorithms, we can achieve a high-resolution lightfield. The corresponding simulation demonstrates the performance of our methods. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

In this work, a series of DTPA based Ln complexes containing one or two chromophores with different degrees of conjugation were synthesized. The proton relaxivities of Gd(III) analogues were investigated as potential MRI contrast agents while the photoluminescence of Eu(III) and Tb(III) analogues were studied for their applications in optical probes for cellular imaging. Later investigation indicates that only emissions from the chromophores could be measured upon long wavelength photon excitations in the microscope. With suitable ligand design, novel dual functional imaging probes were finally synthesized and these showed good luminescence intensity and image contrast in both in-vivo and in-vitro studies. Eight DTPA based Ln (III) complexes LnL1-L8 containing one or two chromophores which include benzene, 2-aminopyridine, 3-amino-pyridine and 4-aminopyridinewere synthesized. The syntheses, relaxometric properties, hydration numbers, quantum yields, sensitization efficiencies, brightnesses, cytotoxicities and cellular uptake properties were discussed. Those mono-substituted complexes show higher relaxivity, while the di-substituted complexes show lower relaxivity than Gd-DTPA (4.17 mM-1 s-1),a clinically used MRI contrast agent(CA).The di-substituted Tb(III)/Eu(III) analogues show lower sensitization efficiency than the mono-substituted ones in the energy transfer process. Therefore, the experimental results clearly illustrate that the complex with one chromophorein the DTPA system is a better option for being used as a MRI contrast agent and an optical probe. Another eight new mono-substituted DTPA based Ln(III) complexes LnL9-L16 containing extended conjugated chromophores were synthesized and investigated. The phenyl derivatives and naphthyl derivatives were added onto the para-position of 2-aminopyridine that was employed as the chromophore. All GdL9-L16possess one bound water molecule and show higher relaxivity than Gd-DTPA. The relaxivities at 300 MHz at 25oC are in the descending order of GdL15(5.37 mM-1s-1) > GdL16(5.23 mM-1s-1) > GdL13(5.12 mM-1s-1) > GdL14(5.06 mM-1s-1) > GdL11(4.96 mM-1s-1) > GdL12(4.83 mM-1s-1) > GdL10(4.80 mM-1s-1) > GdL9(4.50 mM-1s-1). Their quantum yields, sensitization efficiencies and brightnesses are greatly improved because of the highly conjugated chromophores. Moreover, they all showed low cytotoxicity to cells in a MTT assay and a high accumulation in cells in cellular uptake studies. However, no emission from the Eu(III) ion was detected from the Eu(III) analogues upon long wavelength photon excitation in the cell imaging studies, only the emissions from the chromophores were observed. Two mono-substituted DTPA based Ln(III) complexes containing anthracenyl derivatives as the chromophore LnL17-L18 and two DTPA-based binuclear Ln(III) complexes LnL19-L20were synthesized and investigated. Among the four complexes, GdL18 shows the highest relaxivity (4.65 mM-1s-1) and the highest fluorescent quantum yield (2.45%).It also has low cytotoxicity to cells in MTT assay and high accumulation in cells in cellular uptake study. In addition, GdL18shows very strong binding interaction towards serum albumin, i.e. 318,400mol-1dm3for HSA and 90,200 mol-1dm3for BSA. In preliminary studies, GdL18can both give good luminescence intensity and image contrast in both in vitro cell imaging and in vivo MRI studies. Therefore, GdL18 is considered as a potential candidate for use as a dual functional MRI/optical imaging probe. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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Coded-aperture imaging without detector motion can be used to reconstruct three-dimensional radionuclide distributions in the context of nuclear medicine. This approach offers several advantages over the rotating gamma-ray camera systems presently employed in the clinic. These advantages include improved sensitivity, potentially better spatial resolution, and the capability of doing dynamic studies. There are two problems associated with the coded-aperture approach, however. First, the data is "multiplexed", which refers to the fact that many line integrals of the source distribution are combined together and not measured individually, so that information is lost. Second, the number of resolvable detector elements is typically an order of magnitude less than the number of object elements to be reconstructed, so that the reconstruction problem is underdetermined. Consequently, the reconstruction is not unique. By using various types of a priori information in forming the reconstruction, however, it is possible to augment the incomplete data set. Two algorithms are presented to reconstruct objects from their coded-image projections and various types of a priori information. The first, a Monte Carlo algorithm, is a flexible and computationally efficient approach using the a priori knowledge of positivity and nearest-neighbor correlation. This algorithm is used to qualitatively explore the effect of the data-taking geometry on reconstruction performance. The second algorithm is a linear estimator incorporating as a priori knowledge completely general first- and second-order statistical information about the object class to be reconstructed. The linear-estimator formalism also provides a minimum-variance expression for system optimization. This linear algorithm is used to explore the effects of correct and incorrect a priori information on reconstruction performance, and to quantitatively investigate reconstruction quality with respect to data-taking geometry.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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