Thesis (M.C.E.)--University of Delaware, 2006. / Principal faculty advisor: James T. Kirby, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 55-60). Also available in electronic version.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 151-166). Also available in electronic version.

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 21, 2007) Vita. Includes bibliographical references.

Proefschrift Universiteit Maastricht. / Auteursnaam op omslag: Koo de Priester. Met lit. opg. - Met samenvatting in het Nederlands.

Proefschrift Maastricht. / Lit. opg. - Met een samenvatting in het Nederlands.

Spin-exchange optical pumping (SEOP) is a hyperpolarisation method used in the hyperpolarisation of noble gases and can enhance nuclear spin polarisation by five orders of magnitude. Hyperpolarised (HP) 129-Xe has many properties that make it ideally suited to clinical lung imaging, but since its first demonstration in animals in 1994 and humans in 1996, translation to the clinic has been hampered by challenges associated with scaling up production. Within this thesis, construction and demonstration of a clinical-scale stopped-flow hyperpolariser is described, the design of which is based on the record holding XeUS and XeNA polarisers developed previously by our consortium, which had aimed to address the issue of production scale-up. Modifications enhancing the ease of operation and utility in-clinic are presented, as are modifications that reduce the capital cost of such a system. These include a re-design of the gas manifold and the development of a low-cost low-field NMR spectrometer which achieved an SNR of 125 at a cost of ~$300, a 13-fold improvement in cost/SNR compared with the existing spectrometer at a saving of ~$19,000. In continuous-flow 129-Xe polarisers there has long been a discrepancy in the polarisation achieved and that predicted by the standard model of SEOP which was shown recently to be due to the presence of rubidium clusters. Here, the standard model is applied to- and validated for the first time against the stopped-flow regime. The validated model is used to explore parameter space to identify the most effective ways to increase production yield in future stopped-flow polarisers. Stopped-flow SEOP in the xenon-rich regime presents unique thermal management problems due to the absence of gas flow and abundance of poorly thermally conductive, Rb spin destroying Xe. Raman spectroscopy is used to spatially examine in-cell thermal behaviour under steady-state and turbulent 'rubidium runaway' conditions as a function of temperature and Xe density and the beneficial impact of adding thermally conductive helium to the standard N2-Xe gas mix is demonstrated. Hybrid Rb-Cs-Xe SEOP is demonstrated for the first time and examined using in-situ NMR and Raman spectroscopies. High polarisations of ~50% were obtained. Finally, progress on the HP-Xe clinical trial is presented to illustrate the impact of the 4-fold increase in SNR that will come with the installation of the new N-XeUS stopped-flow polariser.

There is an increasing interest in evaluating the role of ultrasound in the identification and management of osteoporosis. We may measure the velocity of ultrasound through bone and the frequency-dependent attenuation, generally referred to as broadband ultrasound attenuation (BUA). The dependence of these parameters upon osteoporotic changes in density and architecture(total loss or thinning of trabeculae width) is still not well defined. A physical model for cancellous bone was developed by introducing an array of cylindrical voids of defined diameter and configuration into polymethylmethacrylate (Perspex). Experimental studies on the cancellous bone model demonstrated that the relationship between BUA and porosity is approximately parabolic, with low BUA values obtained at both low (cortical bone) and high (bone marrow) porosities. This explains the discrepancies in the correlation between BUA and density for different bone structures reported in the literature. BUA was also found to be dependent on the number of pores and the pore distribution(structure). Velocity was found to be dependent on pore size only. BUA and velocity were also found to be temperature dependent. Permeability provides quantitative information related to structure, validated using the perspex model. In vitro studies were carried out on bovine and human cancellous bone (calcaneus and vertebrae). The relationship between Young's modulus, strength and density followed the power law predicted by theoretical models. Measurements on bovine and vertebrae samples were carried out in three orthogonal directions. Young's modulus, strength, BUA, velocity and permeability were shown to be direction dependent and hence dependent upon structure. The relationship between BUA and density followed the parabolic trend observed in the physical model, with the human samples on the rising phase and the bovine on the falling phase of the parabola. BUA in the calcaneus was found to follow a power law relationship with density (BUA = rho[1.99]). BUA was a goodpredictor of strength in both the bovine (R[2] = 74%) and calcaneus (R[2] = 75%) samples. Velocity was a good predictor of both Young's modulus and strength whenapplied to the bar wave equation (E = V[2]rho) with an R[2] of 94% and 88% respectively for the calcaneus and 91% and 92% respectively for the bovine samples. For thecalcaneus samples an R[2] of 83% and 80% for Young's modulus and strength were obtained when density in the bar wave equation was substituted by BUA. The cortical end plates have a significant offset effect on BUA in the calcaneus. Permeability was highly correlated to strength. BUA and velocity were shown to be good predictors of cancellous bone strength in vitro. Future work should concentrate upon the investigation of controlled structural models of cancellous bone and also on the extrapolation of this study to the in vivo prediction of bone strength.

Electrical impedance tomography (EIT) is an imaging technique that aims to reconstruct the internal conductivity distribution of a body, based on the electrical measurements taken on its periphery. While relatively new it has received attention as a possible new medical imaging technique which offers non-hazardous applications and low-cost instrumentation. To understand the full potential of this new mode of imaging, a numerical modelling method has been used in order to investigate the behaviour of an EIT system. Using this mode of analysis, it is possible to simulate many experiments that otherwise physically would be very time consuming and expensive. Such investigation will include the effect and quantification of various physical conditions which have effects on the obtained boundary voltages of an EIT system. An aim of EIT is the ability to reconstruct accurate images of internal conductivity distributions from the measured boundary voltages. Image reconstruction in EIT using the sensitivity algorithm is generally based on the assumption that the initial conductivity distribution of the body being imaged is uniform. The technique of image reconstruction using the sensitivity algorithm is described and reconstructed images are presented. Improvements in image quality and accuracy are demonstrated when accurate a-priori 'anatomical' information, in the form of a model of the distribution of conductivity within the region to be imaged, are used. In practice correct a-priori information is not available, for example, the conductivity values within the various anatomical regions will not be known. An iterative algorithm is presented which allows the conductivity parameters of the a-priori model to be calculated during image reconstruction. Multi-frequency EIT is a modified approach of the single frequency method by which tissue characterisation has been proposed by imaging the internal conductivity of region over a range of frequencies. However, due to instrumentation drawbacks, only the real parts of the boundary voltages are presently measured. These real only voltages have sofar (in practice) been used to reconstruct images of the changes in internal conductivity of a region with frequency. The penalty for ignoring the imaginary parts of the data are presented and results obtained show that to accurately image the internal conductivity of a region, not only complex data are needed, but also some a-priori information about the region may be necessary.

The osteoclast ruffled border is a highly convoluted, complex membrane that is necessary for bone resorption. It is thought to form following mass lysosomal fusion with the boneapposing plasma membrane and vesicular trafficking is vital for its formation and function. The aim of this PhD was to better understand the ultrastructure, formation and function of the ruffled border using TEM and advanced imaging techniques. Ruffled border reformation following calcitonin treatment was visualised and the stages of ruffled border formation were described. Ruffled borders in healthy and osteopetrotic osteoclasts were also imaged by TEM and characterised using a morphological grading system. The key findings of this thesis are as follows: (1) vacuoles, not lysosomes, are the primary contributors of membrane to the ruffled border and the membrane projections of the ruffled border form passively as a consequence of channel formation, not actively by membrane folding, (2) extracellular vesicles are located, and appear to be released, at the ruffled border. Various functional aspects of the ruffled border were also investigated. Vesicles near the ruffled border were identified and characterised by immunoelectron microscopy based on their content and morphology. We found no morphological defects in ruffled borders in mice deficient in Plekhm1. In osteoclasts derived from patients with a SNX10 mutation, we found that while the cells retained the capacity to form well-developed ruffled borders, they did so less often than healthy control osteoclasts. Importantly, we observed that even in a population of healthy osteoclasts, ruffled border morphology is highly heterogeneous because they are at different stages in the resorption cycle. In conclusion, the data in this thesis provide novel findings, previously unseen details regarding how resorbing osteoclasts interact with the bone surface, and have revealed unique insights into ruffled border morphology, formation and the vesicles with which it interacts.