Magnetic resonance imaging at low magnetic field using hyperpolarized ^{3}He gas

A low magnetic field magnetic resonance imaging system for small animal lung imaging using hyperpolarized ^{3}He gas is presented. The hyperpolarized ^{3}He gas at 1 mbar pressure and 30% polarization is obtained by the metastability exchange optical pumping technique. The magnetic resonance imaging unit is based on a permanent magnet of open geometry, built from a new generation Nd-B-Fe magnetic material. It produces the magnetic field of 88 mT with homogeneity better than 50 ppm in the 10 cm diameter sphere, after application of passive shimming. The magnetic field gradients of 30 mT/m are generated by a set of biplanar, actively shielded gradient coils. The first ^{1}H images of various biological objects, as well as ^{3}He images of the rat lung in vivo obtained in the described system are shown. In terms of sensitivity and resolution, the technique is superior to conventional ^{1}H magnetic resonance imaging, and offers great possibilities in early diagnosis of lung diseases.