Abstract: A magnetic field generating device for use in MRI having a pair of pole pieces opposed at a space to each other and generating a magnetic field in the space, wherein the pole piece has a laminate structure in which a soft ferrite and a magnetic material base are disposed from the side of the space, and a layer of small magnetic permeability and high electric resistance is interposed between the soft ferrite and the magnetic material base. The soft ferrite may be lamination of the soft ferrite and silicon steel sheets. High speed image pick-up at high sensitivity and sharpness is enabled by reducing the eddy current and the remanent magnetism generated in the pole piece by the gradient magnetic field coils.

Abstract: In a magnetic field generating apparatus for use in MRI comprising cylindrical yokes, a pair of permanent magnets of a trapezoidal section opposed in parallel with each other in the cylindrical yokes with a predetermined gap being defined between each of the pole faces of them, permanent magnets of a triangular section in adjacent with both sides of the trapezoidal permanent magnet in which a magnetic field space having a hexagonal cross section in perpendicular to the longitudinal direction defined by pole faces of the trapezoidal permanent magnets and the pole faces of the triangular permanent magnets, whereinthe trapezoidal permanent magnets comprise rare earth system permanent magnet and the direction of magnetization thereof is identical with the direction of the magnetic field in the magnetic field space, the triangular permanent magnets comprise a ferrite system permanent magnet and the direction of magnetization thereof is at a 90.degree.

Abstract: An improved magnetic field generating device for use with a medical nuclear magnetic resonance tomographic device (MRI). The device comprises a magnetic circuit formed of a pair of magnetic pole pieces connected by yoke members in opposite relationship with each other leaving a space sufficient to accommodate therebetween an object receiving a medical inspection. According to the present invention, a super-conductive coil is wound around one of the pairs of magnetic pole pieces and the dimensional relationship between the two magnetic pole pieces is varied in a variety of ways to reduce the magnetic field imbalance, with the advantages that the magnetic flux distribution becomes highly uniform throughout the space between the pair of magnetic pole pieces, the patient entering the space has no oppressive sensation and the manufacturing cost can be reduced to a considerable degree.