3He Lung Imaging in an Open Access, Very-Low-Field Human MRI System
  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. 
R. W. Mair, M. I. Hrovat, S. Patz, M. S. Rosen, I. C. Ruset, G. P.   Topulos, L. L. Tsai, J. P. Butler, F. W. Hersman and R....