Low-temperature polarized helium-3 for MRI applications

The first He-3 nuclear magnetic resonance (NMR) experiments using low-tempe rature prepolarization are presented. He-3 cells were polarized at 4.2 K an d 4.7 T, transported to another magnet, heated to room temperature, and use d for NMR experiments at 2.35 T. Cells with and without a rubidium coating were tested. In both cases, the NMR signal was greater than 100 times the t hermal equilibrium signal. No evidence of a rubidium coating effect on the longitudinal relaxation time T-1 of He-3 (500 mbar) at 4.2 K could be demon strated. NMR gradient-echo images of the cells were acquired. (C) 1999 Wile y-Liss, Inc.