By using a multiple receiving coil composed of receiving coils, an imaging portion of a subject is subjected to a first pulse sequence to create n sensitivity images (701 to 703) fewer than the examination images. When these sensitivity images are created, an NMR signal is measured for only the low-frequency region of the k space. A second pulse sequence from which a phase encode step is removed is conducted to create m (m>n) examination images (704, 705) of the subject by using the receiving coils. When sensitivity distributions (707, 708) of the receiving coils are determined for the sensitivity images (701 to 703), and if there are no sensitivity distributions corresponding to the slice positions of the examination images (704, 705), they are determined by slice interpolation using the sensitivity distributions (701 to 703), and the aliasing artifacts of the examination images (704, 705) are removed by matrix operation by using the sensitivity distributions (707, 708).

Magnetic resonance imaging device

Magnetic resonance imaging apparatus

A magnetic field generator for MRI, wherein a plurality of permanent magnet elements are arranged into a ring on the inner surface of a yoke having a polygonal hollow. The present invention contemplates to reduce a leaking magnetic flux, to improve homogeneity of a magnetic field at a required portion, to reduce the occurrence of eddy currents without lowering homogeneity of the magnetic field inside a space, and to raise the intensity of a gradient magnetic field to a predeterminded intensity within a short time. Further, the present invention contemplates to provide a magnetic field generator for MRI which reduces the weight of a magnet, facilitates machining and production, and has a high working property. In the present invention, a plurality of permanent elements disposed on the inner surface of the yoke having a polygonal hollow are constituted by permanent magnet blocks having a direction of magnetization thereof perpendicular to the yoke contact suface, a principal magnetic field is generated by a pair of permanent magnet constituent members so disposed as to face each other and to have the direction of magnetization thereof in the same direction as the direction of the magnetic field of the homogeneous magnetic field formed at the center of the space, and provided with magnetic pole plates. Protrusion of permanent magnet plates having the direction of magnetization thereof in the same direction as the direction of the permanent magnet elements are disposed on gap opposing end surfaces at both end portions of an opening of the permanent magnet elements not provided with the magnetic pole plates. Each magnetic pole plate has a construction wherein protrusions are disposed on both ends of a base material, the protrusions and a surface layer portion near the protrusions are composed of a silicon steel sheet or a soft ferrite, and a central protrusion portion, the major proportion of which comprises a flat protrusion and which is composed of soft ferrite or silicon steel sheet is disposed at the center. A silicon steel laminate is disposed on the entire inner surface of the yoke other than the fitting surface of the pair of permanent magnet elements.

Magnetic field generator for MRI

Axisymmetric solid of revolution derivable from section at FIG. 5 is generally toroidal with electric current(s) in windings (110, 160) preferably flowing circumferentially along major circle(s) during power coupling device operation. Current(s) in windings (110, 160); current(s) in half-shields (120, 170); and the volume of space swept out by shield airgap(s) (101) emerge from plane of paper perpendicularly at FIG. 5 but as these emerge therefrom they curve to follow toroidal major circle(s). Cores (115, 165) preferably shunt and align magnetic flux such that magnetic field lines escape therefrom primarily only in region(s) of core airgap(s) and such that magnetic flux loops lie in planes of toroidal minor circle(s). Half-shield(s) (120, 170) preferably have electrically conductive material(s) distributed therein as is sufficient to substantially cancel magnetic flux lines impinging thereon before effects of such impinging magnetic flux lines would reach shield airgap(s) (101) and/or outer surface(s) of half-shields (120, 170).

Shielded power coupling device

A plate yoke has an upper surface formed with a projection and a guiding rail. A new magnet block is transported by sliding on the upper surface of the plate yoke, and is bonded side by side with the projection or a magnet block which is already fixed. During the above operation, a magnetic member is held above the plate yoke. Preferably, the new magnet block is transported toward a corner portion, with side surfaces of the magnet block held parallel to a side surface of the projection and a side surface of the guiding rail respectively. When the magnet unit and the column yoke is connected, the column yoke or the magnet unit is lowered so that a guiding rod attached to an end face of the column yoke is inserted into a hole formed in the magnetic unit. Further, the column yoke is guided by a guiding member disposed between a permanent magnet on the plate yoke and a position where the column yoke is to be connected on the plate yoke.

Method for assembling a magnetic field generator for MRI

PURPOSE: To provide a permanent magnet magnetic circuit for a magnetic resonance imaging device (MRI device) which generates less eddy current due to the application of gradient magnetic field and is useful for generating bias magnetic field where gradient magnetic flux can easily pass in a nuclear magnetic resonance tomography device (MRI device). CONSTITUTION: In a permanent magnetic opposite type magnetic circuit where a pair of magnets are opposed each other and a magnet-adjustment plate 2 is provided on a magnet space surface and they are connected by yoke to constitute a closed magnetic path. Then, the magnet-adjustment plate 2 is a lamination steel plate consisting of iron plate and silicon steel plate and the silicon steel plate is arranged on the surface of the magnet-adjustment plate facing the space and the silicon steel plate is laminated so that a diameter orientation directionality steel plate 9 and non-oriented steel plate or the diameter orientation directionality silicon steel plate 9 and a peripheral orientation directionality silicon steel plate 10 whose orientation direction is orientated in peripheral direction are mixed in thickness direction.

Takeshi Ohashi

Papers

Permanent magnet magnetic circuit