An open-access, very-low-field MRI system for posture-dependent 3He human lung imaging

We describe the design and operation of an open-access, very-low-field, magnetic resonance imaging (MRI) system for in vivo hyperpolarized He-3 imaging of the human lungs. This system permits the study of lung function in both horizontal and upright postures, a capability with important implications in pulmonary physiology and clinical medicine, including asthma and obesity. The imager uses a bi-planar B-0 coil design that produces an optimized 65 G (6.5 mT) magnetic field for He-3 MRI at 210 kHz. Three sets of bi-planar coils produce the x, y. and z magnetic field gradients while providing a 79-cm inter-coil gap for the imaging subject. We use solenoidal Q-spoiled RE coils for operation at low frequencies, and are able to exploit insignificant sample loading to allow for pre-tuning/matching schemes and for accurate pre-calibration of flip angles. We obtain sufficient SNR to acquire 2D He-3 images with up to 2.8 mm resolution, and present initial 2D and 3D He-3 images of human lungs in both supine and upright orientations. H-1 MRI can also be performed for diagnostic and calibration reasons. Published by Elsevier Inc.