We develop a 3He polarization based ultra-low field (ULF) magnetic resonance imaging (MRI) system prototype for lung inspection. Using hyperpolarized 3He gas as probe can distinguish lung from other tissues and improve signal-to-noise ratio, making it possible to use ultra-low magnetic field main magnets. In order to adapt to the magnetic resonance characteristics of the hyperpolarized 3He probe, we propose a self-calibrating fast imaging sequence, which reduces the workload of equipment tuning and parameter matching. Vertical open resistance magnets were used to meet the research needs of lung function under different postures. The maximum outer size of the magnet is less than 1900mm, the entrance space is not less than 600mm, and the operating power consumption is less than 1kW. Compared with superconducting and permanent magnetic resonance systems, there is no standby consumption. We carried out imaging experiments of water model, in vitro animal organs, plants and hyperpolarized 3He gas model. The results show that the field of view of the device is no less than 310mm×310mm×400mm, and the single imaging time of hyperpolarized 3He model is less than 7s. These results show the applicability of the ULF-MRI system in lung inspection.

ultra-low field,Magnetic resonance imaging (MRI),hyperpolarization