HYPERPOLARIZED GASES - A NEW-TYPE OF MR CONTRAST AGENTS

The nuclear spin polarization of noble gases can be strongly enhanced by laser optical pumping followed by electron-nuclear polarization tra nsfer. Direct optical pumping of metastasable He-3 atoms has been show n to produce enormous polarization in the order of 0.4-0.6. This is ab out 10(5) times greater than the polarization of water protons at ther mal equilibrium used at conventional MR imaging. We demonstrate that h yperpolarized 3He gas can be applied to nuclear MR imaging of human or gans with air-filled spaces. In vivo He-3 MR experiments were performe d in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T and at 1.5 T using a double resonant Helmholtz coil operatin g at 63.6 and 48.6 MHz for H-1 and He-3, respectively. Anatomical deta ils of the lungs of a volunteer were visualized with the FLASH techniq ue demonstrating the potential of the method for fast imaging of airwa ys in the human body and for pulmonary ventilation studies.