NUCLEAR-MAGNETIC-RESONANCE IMAGING OF AIRWAYS IN HUMANS WITH USE OF HYPERPOLARIZED HE-3

The nuclear spin polarization of noble gases can be enhanced strongly by laser optical pumping followed by electron-nuclear polarization tra nsfer. Direct optical pumping of metastable He-3 atoms has been shown to produce enormous polarization on the order of 0.4-0.6. This is abou t 10(5) times larger than the polarization of water protons at thermal equilibrium used in conventional MRI. We demonstrate that hyperpolari zed He-3 gas can be applied to nuclear magnetic resonance imaging of o rgans with air-filled spaces in humans. In vivo He-3 MR experiments we re performed in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T. Anatomical details of the upper respiratory trac t and of the lungs of a volunteer were visualized with the FLASH techn ique demonstrating the potential of the method for fast imaging of air ways in the human body and for pulmonary ventilation studies.