Longitudinal relaxation and diffusion measurements using magnetic resonance signals from laser-hyperpolarized Xe-129 nuclei

Methods for T-1 relaxation and diffusion measurements based on magnetic resonance signals from laser-hyperpolarized Xe-129 nuclei are introduced. The methods involve optimum use of the perishable hyperpolarized magnetization of Xe-129. The necessary theoretical framework for the methods is developed, and then the methods are applied to measure the longitudinal relaxation constant, T-1, and the self-diffusion constant, D, of hyperpolarized Xe-129. In a cell containing natural abundance Xe-129 at 790 Torr, the T-1 value was determined to be 155 +/- 5 min at 20 degrees C and at 2.0 T field. For a second cell at 896 Torr, at the same field and temperature, the T-1 value was determined to be 66 +/- 2 min. At a higher field of 7.05 T, the T-1 values for the two cells were found to be 185 +/- 10 and 88 +/- 5 min, respectively. The Xe-129 self-diffusion constant for the first cell was measured to be 0.057 cm(2)/s and for the second cell it was 0.044 cm(2)/s. The methods were applied to Xe-129 in the gas phase, in vitro; however, they are, in principle, applicable for in vivo or ex vivo studies. The potential role of these methods in the development of newly emerging hyperpolarized Xe-129 MRI applications is discussed. (C) 1997 Academic Press.