Spin-Exchange Optical Pumping and Nuclear Magnetic Resonance of 129Xe

The nuclear spin polarisation of 129Xe can be increased by four to five orders of magnitude using the technique spin-exchange optical pumping. The resulting enhancement in polarisation can be utilised to dramatically enhance the sensitivity of 129Xe in nuclear magnetic resonance (NMR) applications. This thesis is concerned with the physics of spin-exchange optical pumping and NMR spectroscopy of hyperpolarised 129Xe. Its general aims are to optimise the production of hyperpolarised 129Xe and to evaluate the underlying NMR mechanisms of 129Xe in blood (in vitro and in vivo). Chapters 3 and 4 detail experiments and modelling on a spin-exchange optical pumping polariser with the aim to optimise the production of hyperpolarised 129Xe for nuclear magnetic resonance NMR spectroscopy. This optimisation has enabled high-quality imaging of the airspaces of the human lungs as well as spectroscopy of 129Xe dissolved in blood and lung tissue. In addition to 129Xe polarisation optimisation, in Chapter 5, NMR experiments on 129Xe in human blood were performed to determine constants underpinning 129Xe NMR relaxation and exchange dynamics in whole blood samples. These constants should enable accurate modelling of 129Xe signal dynamics during in vivo experiments involving xenon transport from the lungs to distal tissues. Lastly, in Chapter 6, hyperpolarised 129Xe NMR was used to probe pulmonary blood oxygenation in vivo. A non-linear relationship between the 129Xe chemical shift in red blood cells was determined in vitro on human blood samples at 1.5 T and 3 T. This relationship was used for dynamic measurements of pulmonary blood oxygenation in a healthy volunteer during breath-hold apnoea on a 3 T scanner.