A development of a permanent magnet assembly for MRI devices using Nd-Fe-B material

A permanent-magnet assembly for whole-body magnetic resonance imaging (MRI) has been developed, using a high-energy Nd-Fe-B magnet material. The developed assemblies have the following features: (1) by using shimmed pole pieces in addition to the new material, a compact assembly is realized compared with currently used magnets. (2) The signal/noise ratio can be improved about 40% because the field is oriented vertically with respect to the patient. (3) Since the assembly has a four-column configuration, patients feel comfortable during examination. (4) Small leakage flux makes possible installation in a small room. (5) Operating cost is drastically reduced by using a permanent magnet. A typical assembly and its characteristics are shown. It is confirmed that the quality is almost at the same level as that of a mid-field superconducting magnet