Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes vita. Includes bibliographical references (p. 161-182).

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016 / The theoretical and experimental investigation of electron spin-resonance relaxation to deposit thermal energy into liquid gadolinium-based contrast agents for cancer hyperthermia treatment is presented. Previous works suggest that using protons in water are inadequate, with a thermal deposition rate of approximately 1 ◦C per two years. A novel component of this research relies on the use of gadolinium-chelated molecules, which are currently used as contrast agents in clinical MRI scans. The chelating agents, or ligands, investigated are Gadobenate (MultiHance R ), Gadopentetate (Magnevist R ), Gadoterate (DotaremR ) and Gadoteridol (ProHance R ). The gadolinium atom has seven unpaired electrons in its inner f shell orbital and as a result has a 660 times stronger paramagnetic response when placed in an external magnetic field. The research tests the hypothesis that by using an appropriate external homogeneous DC magnetic field, together with a radiofrequency excited resonator, that a measurable amount of thermal energy is deposited into a liquid gadolinium-based contrast agent. The aim of this research is to ultimately discover a new cancer hyperthermia treatment. The research theory suggests that a temperature rate of 13.4 ◦C · s−1 can be achieved using the gadolinium-based contrast agents under certain experimental conditions, and a maximum of 29.4 ◦C · s−1 under more optimal conditions. The temperature rates are calculated using parameter values commonly found in literature and practice. The simulation and design of the DC magnetic field coil system is discussed, together with the simulation results and design parameters of the radiofrequency loop-gap resonator. The experimental results and analysis indicate that the selected contrast agents have varied responses based on their chemical nature and that only two out of the four contrast agents, Dotarem and ProHance, show a measurable effect albeit sufficiently small that statistical techniques were necessary to distinguish the effect from background. A model fit to the data is performed in order to determine the spin-lattice relaxation time of the contrast agents under the specified experimental conditions. The model estimate is significantly smaller than the values found in literature under similar conditions, with a spin-lattice relaxation time τ1e of approximately 0.2 ps compared to the literature value of 0.1 ns. Although the observed electron spin resonance heating rate is in the milli-Watt range it is still notably larger (167 000 times) compared to the heating rate obtained using protons. The low temperature rates suggest that a more suitable agent or molecule with a larger spin-relaxation time be used, in order to achieve clinical useful temperature rates in the range of 14 ◦C · s−1. / MT2017

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 175-181). Also available via World Wide Web.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 205-218).

Iron oxide nanoparticles are of great interest as contrast agents for research and potentially clinical molecular magnetic resonance imaging (MRI). Biochemically modifying the surface coatings of the particles with proteins and polysaccharides enhances their utility by improving cell receptor specificity, increasing uptake for cell labeling and adding therapeutic molecules. Together with the high contrast they produce in MR images, these characteristics promise an expanding role for iron oxide nanoparticles and molecular MR imaging for studying, diagnosing and treating diseases at the molecular level. However, these contrast agents produce areas of signal loss with traditional MRI sequences that are not specific to the nanoparticles and cannot easily quantify the contrast agent concentration. With the expanding role of iron oxide nanoparticles in molecular imaging, new methods are needed to produce a quantitative contrast that is specific to the iron oxide nanoparticle. This dissertation presents a new method for detecting and quantifying iron oxide nanoparticles using an adiabatic preparation pulse and the failure of the adiabatic condition for spins diffusing near the particles. In the first aim, the theoretical foundation of the work is presented, and a Monte Carlo simulation supporting the proposed mechanism of the contrast is described. Adiabatic pulse prepared imaging sequences are also developed for imaging at 3 Tesla and 9.4 Tesla to highlight the translational potential of the approach for clinical examinations and scientific research, and the linear correlation of the contrast with iron concentration ideal for quantification is presented. Further, the physical characteristics of the nanoparticles and the parameters of the MRI sequence are modified to characterize the approach. In the second aim, the contrast is characterized in more realistic phantoms and in vitro, and a method to more accurately quantify nanoparticle concentration in the presence of magnetization transfer is presented. Finally, accelerated imaging methods are implemented to acquire the adiabatic contrast in a time compatible with in vivo imaging, and the technique is evaluated in an in vivo model of quantitative iron oxide nanoparticle imaging. Together, these aims present a method using an adiabatic preparation pulse to generate an MR contrast based on the microscopic magnetic field gradients surrounding the iron oxide nanoparticles that is suitable for in vivo quantitative, molecular imaging.