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: A magnetic field generating device used for MRI includes a pair of magnetic pole pieces to each other to provide a gap therebetween and generate a magnetic field in the gap, the magnetic pole pieces being formed by laminating and integrating a plurality of non-oriented silicon steel sheets. By using laminated non-oriented silicon sheets the eddy current generated in the magnetic pole pieces caused by the application of GC pulses can be reduced and phenomenon of the residual magnetism can also be reduced.

Abstract: A magnetic field generating apparatus for a magnetic resonance imaging (MRI) apparatus, including soft ferrite disposed adjacently to a gradient magnetic field coil which is disposed in a gap and serves to form a static magnetic field. The soft ferrite has saturated magnetic flux density (Rs) more than 0.4 T, coersive force (He) less than 50 A/m, and specific resistance .rho. more than 10.sup.-5 .OMEGA..multidot.cm. The magnetic field generating apparatus thus constructed has a magnetic circuit arrangement that a pair of permanent magnetic bodies which are disposed so as to confront each other and define the gap are magnetically connected through a yoke, and pole pieces are fixedly secured to the surfaces of the respective permanent magnetic bodies facing the gap, thereby generating the magnetic field in the gap.

Abstract: Disclosed is an MRI-dedicated magnetic field generating device for generating magnetic fields within an air gap, including: a pair of permanent magnet assemblies opposite to each other to form an air gap therebetween; yokes for magnetically linking the permanent magnet assemblies; and magnetic pole pieces fixed to air-gap-confronting surfaces thereof. Based on this construction, intensities of the magnetic fields are increased by disposing a plurality of magnetic material segments on the same circle or a concentric circle on the confronting surface thereof or decreased by disposing a plurality of permanent magnet segments having a magnetizing direction opposite to that of the permanent magnet assemblies on the same circle or the concentric circle on the confronting surface thereof; or alternatively both the magnetic material segments and the permanent magnet segments are disposed on the same circle or the concentric circle.

Abstract: A magnetic field-generating device includes a pair of permanent magnet components disposed in such a manner as to face each other with a gap formed therebetween, a yoke for magnetically coupling the pair of permanent magnet components, and pole pieces which are each fixed to a surface of a corresponding permanent magnet component that faces the gap. The magnetic field generating device is adpated to generate a magnetic field in the gap. Each of the pole pieces is made of a laminate of magnetic plates which laminated in a direction substantially perpendicular to the sides of the solid care portion.

Abstract: A magnetic field generating device for the NMR-CT comprises a pair of opposing permanent magnet segments magnetically coupled by a yoke which define therebetween an air gap where a magnetic field is created. Each segment has a pole piece attached to its gap-facing surface. Each segment is composed of a ferrite magnet and a rare earth magnet, one of the two magnets being disposed in the central portion of the segment and the other disposed around the one magnet. The thickness of the ferrite magnet in the direction of attaching it to the yoke is larger than that of the rare earth magnet.

Abstract: A magnetic field generating device for nuclear magnetic resonance-computerized tomography of the type wherein permanent magnet assemblies of a pair opposing mutually to define an air gap therebetween are magnetically coupled together by yoke means to create a magnetic field within the air gap is provided, which is characterized in that each permanent magnet assembly comprises a flat plate-like central permanent magnet and peripheral permanent magnets arranged around the central permanent magnet and inclined toward the inside of the air gap, the magnetic pole surface of each permanent magnet assembly forms a curved concave face with respect to the air gap, and each permanent magnet is magnetized in the direction perpendicular to the corresponding magnetic pole surface, whereby the leakage flux is reduced and the magnetic efficiency is enhanced, thus, reduction of the device dimension and weight can be achieved.

Abstract: A magnetic field generating device for a nuclear magnetic resonance-computerized tomography comprising a pair of permanent magnets magnetized in the same direction with different-polarity poles opposing mutually to define an air gap, whose maximum energy product, (BH).sub.max, is not less than 30 MGOe (240 KJ/m.sup.3), on each of the opposing faces of the permanent magnets a magnetic pole segment being provided which has an annular projection and, as occasion demands, at least one central convex projection inside the annular projection, and the permanent magnets being coupled magnetically by a yoke to generate a magnetic field within the air gap.The present device is able to create a uniform and stable magnetic field, in spite of its small-sized body.

Abstract: A magnetic field generating apparatus for a magnetic resonance imaging (MRI) apparatus, including soft ferrite disposed adjacently to a gradient magnetic field coil which is disposed in a gap and serves to form a static magnetic field. The soft ferrite has saturated magnetic flux density (Rs) more than 0.4 T, coersive force (He) less than 50 A/m, and specific resistance .rho. more than 10.sup.-5 .OMEGA..multidot.cm. The magnetic field generating apparatus thus constructed has a magnetic circuit arrangement that a pair of permanent magnetic bodies which are disposed so as to confront each other and define the gap are magnetically connected through a yoke, and pole pieces are fixedly secured to the surfaces of the respective permanent magnetic bodies facing the gap, thereby generating the magnetic field in the gap.