  The human lung and its functions are extremely sensitive to gravity, however
the conventional high-field magnets used for most laser-polarized 3He MRI of
the human lung restrict subjects to lying horizontally. Imaging of human lungs
using inhaled laser-polarized 3He gas is demonstrated in an open-access
very-low-magnetic-field (< 5 mT) MRI instrument. This prototype device employs
a simple, low-cost electromagnet, with an open geometry that allows variation
of the orientation of the imaging subject in a two-dimensional plane. As a
demonstration, two-dimensional lung images were acquired with 4 mm in-plane
resolution from a subject in two orientations: lying supine, and sitting in a
vertical position with one arm raised. Experience with this prototype device
will guide optimization of a second-generation very-low-field imager to enable
studies of human pulmonary physiology as a function of subject orientation.
