UNC-CH Physics and Astronomy Preliminary Defense

Alex Burant

“Characterizing Hyperpolarized ¹²⁹Xe Depolarization Mechanisms During Continuous-flow SEOP and as a Source of Image Contrast.”

Xenon-129 has become the isotope of choice for applications of hyperpolarized (HP) noble gases in magnetic resonance imaging (MRI) and spectroscopy due to its lower cost and higher availability compared to 3He, relatively high tissue solubility, and wide range of chemical shifts. As the signal achieved in HP gas MRI is directly related to nuclear spin polarization, the production of large volumes of highly polarized 129Xe is paramount. While near unity levels of xenon polarization have been achieved in optical cells using stopped-flow spin exchange optical pumping (SEOP), continuous-flow SEOP is the most widely used method for clinical applications as it enables the production of large volumes of hyperpolarized gas which are necessary for imaging applications in humans. However, polarization levels achieved via continuous-flow SEOP are well below the theoretically predicted values. We investigate, through both simulations and experiments, 129Xe relaxation mechanisms which are often ignored during continuous-flow SEOP to quantify their effects. This work will feed efforts to bridge the gap between theoretical and experimental xenon polarization levels.