MR-IMAGING WITH HYPERPOLARIZED HE-3 GAS

Magnetic resonance images of the lungs of a guinea pig have been produ ced using hyperpolarized helium as the source of the MR signal. The re sulting images are not yet sufficiently optimized to reveal fine struc tural detail within the lung, but the spectacular signal from this nor mally signal-deficient organ system offers great promise for eventual in vivo imaging experiments. Fast 2D and 3D GRASS sequences with very small flip angles were employed to conserve the nonrenewable longitudi nal magnetization. We discuss various unique features associated with performing MRI with hyperpolarized gases, such as the selection of the noble gas species, polarization technique, and constraints on the MR pulse sequence.