Longitudinal Relaxation and Diffusion Measurements Using Magnetic Resonance Signals from Laser-Hyperpolarized ~(129)Xe Nuclei

摘要

Methods forT1relaxation and diffusion measurements based on magnetic resonance signals from laser-hyperpolarized129Xe nuclei are introduced. The methods involve optimum use of the perishable hyperpolarized magnetization of129Xe. The necessary theoretical framework for the methods is developed, and then the methods are applied to measure the longitudinal relaxation constant,T1, and the self-diffusion constant,D, of hyperpolarized129Xe. In a cell containing natural abundance129Xe at 790 Torr, theT1value was determined to be 155 ± 5 min at 20°C and at 2.0 T field. For a second cell at 896 Torr, at the same field and temperature, theT1value was determined to be 66 ± 2 min. At a higher field of 7.05 T, theT1values for the two cells were found to be 185 ± 10 and 88 ± 5 min, respectively. The129Xe self-diffusion constant for the first cell was measured to be 0.057 cm2/s and for the second cell it was 0.044 cm2/s. The methods were applied to129Xe in the gas phase,in vitro;however, they are, in principle, applicable forin vivoorex vivostudies. The potential role of these methods in the development of newly emerging hyperpolarized129Xe MRI applications is discussed.