UNC-CH Physics and Astronomy Thesis Proposal Presentation

Drew McCallister, UNC Chapel Hill

“The Effect of Magnetic Field Inhomogeneities on Fat Fraction MR Quantification and Optimization of a Continuous Flow Xenon-129 Polarizer for Biomedical Imaging Applications”

Brown adipose tissue (BAT) is a fat tissue specialized in heat production whose malfunction has been recently associated with the development of obesity and diabetes. The most commonly used technique to detect this tissue is FDG-PET, however radiation free MR techniques have also been proposed to detect and quantify this tissue. Here we analyzed how microscopic magnetic susceptibility gradients affect the accuracy of these MR quantification techniques. Additionally, hyperpolarized 129Xe gas has been used as a MR contrast agent for lung imaging, but its applications to other organs are quickly expanding. The largest barrier continues to be the low xenon polarization value achievable by continuous flow spin exchange optical pumping (SEOP). While theoretically polarization values should approach 90%, in practice they have been around 30%. Work done in our lab using finite element analysis simulations of the spin exchange optical pumping (SEOP) process pointed out major shortcomings of the continuous flow SEOP setup. The goal of my work is to improve the SEOP setup. To this end I have designed and constructed a new continuous flow 129Xe polarizer that is expected to increases xenon residency time inside the optical pumping cell and reduce turbulence. At the same time, the new polarizer will make use of a new narrow laser that is specifically designed to optimize the optical pumping process.