Sumitomo Special Metals Co., Ltd.

Neomax Co., Ltd.

Hitachi Metals, Ltd.

Hiroshima University

Sumitomo Special Meter Co., Ltd.

Masaaki Aoki

Shigeo Hashimoto

Tsuyoshi Tsuzaki

Hideya Sakurai

Hiroyuki Takeuchi

Hirotaka Takeshima

Hitoshi Yoshino

Mitsuo Ochi

Eiji Sugiyama

Youichi Ohnishi

Chikako Nakamura

Kimiharu Ohta

Yasuhiro Marukawa

Masayuki Nakatsu

Shiego Hashimoto

Shigemasu Okada

Michiaki Kishimoto

Kimiharu Ota

A magnetic circuit that forms an arc-shaped magnetic field space is provided. Of two magnets constituting a first magnetic circuit, a first magnetic poleis provided with a first yokethat is arc-shaped in planar view, a first magnetthat is arc-shaped in planar view and a magnetic pole piece. On the other hand, a second magnetic poleis provided with a second yokethat is arc-shaped in planar view, a second magnetthat is arc-shaped in planar view and a magnetic pole piece. The first magnetic pole pieceand the second magnetic pole pieceare disposed so as to be opposed to each other while being separated from each other. The first magnetand the second magnetare formed by arranging a plurality of small magnets.

Magnetic circuit for magnetic field generator

A fixation device set S includes an external fixation device which is attached on one end-side of first and second pins; and a pin fixture which is attached on the other end-side. The external fixation device includes a first and a second permanent magnets disposed with their same poles opposed to each other; a first holding portion provided in the first permanent magnet; a second holding portion provided in the second permanent magnet; first limiter portions sandwiching the first and the second permanent magnets from a second direction; and second limiter portions connecting the first limiter portions to each other. The first pins are inserted through through-holes in the first holding portion, whereas the second holding portion is attached to the second pin via a ball joint.

External fixation device and fixation device set

There is provided a magnetic field generator in which separation and dislocation of permanent magnets from their permanent magnet groups is prevented easily and reliably for a long period of time without sacrificing productivity. A magnetic field generatorincludes a permanent magnet groupwhich is provided on a plate yoke; a pole piecewhich is provided in a first main surface of the permanent magnet group, leaving an exposed regionthereon; a frame-like memberwhich is provided on the plate yoketo surround the permanent magnet group; and a flange-shaped memberwhich is provided in the pole pieceto cover the exposed region. Presser boltsare threaded into the frame-like memberand press an outer circumferential surfaceof the permanent magnet groupdirectly or via insertion members. Presser boltsare threaded into the flange-shaped member, and press the exposed regionof the permanent magnet groupdirectly or via insertion members. A plate yokehas the same configuration.

Magnetic field generator

There is provided a method of manufacturing a magnetic field generator () that includes a pair of plate yokes (), () which are opposed to each other, with their opposing faces provided with respective permanent magnet assemblies (), () which have faces opposing to each other, to which pole pieces (), () are fixed respectively, and include permanent magnets (). The permanent magnets (), () include R&#x2014;Fe&#x2014;B magnets. During manufacturing, the assembled magnetic field generator () is heated in its entirety at a temperature not lower than 40&#xb0; C. and not higher than 70&#xb0; C., whereby the R&#x2014;Fe&#x2014;B magnets are magnetized to a magnetization rate not smaller than 80% and not greater than 99.9%.

Magnetic field generator manufacturing method

There is provided a magnetic field generator for MRIapplicable to a variety of magnetic field generators, and capable of preventing separation of permanent magnetswhich constitute permanent magnet groups. The magnetic field generator for MRIincludes a pair of permanent magnet groups. The pair of permanent magnet groupseach including a plurality of permanent magnetsbonded to each other, are opposed to each other with a space in between. The permanent magnet groupshave projectionsprojecting more outward than the area of contact with respective pole pieces. A flange-shaped memberis attached to each outer circumferential surface of the pole pieces, covering a space-facing surfaceof the projection

Magnetic field generator for MRI

There is provided a magnetic field generator which is capable of generating a uniform magnetic field of a desired intensity easily and stably without increasing running cost. The magnetic field generator includes a pair of plate yokes. The plate yokes have opposed surfaces provided with magnetic pole respectively. The magnetic pole includes a permanent magnet group whereas the magnetic pole includes a permanent magnet group. Each of the permanent magnet groups is formed substantially in a disc like shape, as an integral body made of a plurality of permanent magnets and a plurality of heat conducting members. Tubular heaters, buried in the plate yokes, generate heat, which is conducted via the plate yokes to each permanent magnet and each heat conducting member which constitute the permanent magnet groups.

Magnetic field generating device for use in magnetic resonance imaging

A magnetic field generator comprises a pair of plate yokes connected by a column yoke. The pair of plate yokes has a pair of opposed surfaces each provided with a permanent magnet including a plurality of neodymium magnets. In a method in which the neodymium magnets are demagnetized and adhesive is ground, the magnetic field generator is heated to 200&#xb0; C.&#x2dc;350&#xb0; C. After the neodymium magnets are demagnetized, the adhesive is removed and the neodymium magnets are removed and collected from the magnetic field generator. In a method in which the adhesive is carbonized, the magnetic field generator is heated to 350&#xb0; C.&#x2dc;1000&#xb0; C. After carbonizing the adhesive, the neodymium magnets are removed and collected. Surfaces of the collected neodymium magnets are polished and the neodymium magnets are reused. Further, the collected neodymium magnets are re-aged and reused.

Recycling method for magnetic field generator

A magnetic field generator () capable of generating a more intense magnetic field, and an MRI apparatus () using it are provided. Permanent magnets (), (), (), (), (), (), (), (), (), (), () and () are disposed annularly for formation of a magnetic field generation space (). Ferromagnetic materials () and () are provided near the magnetic field generation space (), at places passed by a magnetic flux. Each of the permanent magnets (), (), (), () and () surrounding the ferromagnetic material () is magnetized so as to make an S pole on the side of the ferromagnetic material (). Each of the permanent magnets (), (), (), () and () surrounding the ferromagnetic material () is magnetized so as to make an N pole on the side of the ferromagnetic material (). An MRI apparatus () is obtained by using the magnetic field generator ().

Magnetic field generating device and MRI equipment using the 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

A recycling method for a magnetic field generator, which includes a plate yoke, and a permanent magnet provided on the plate yoke, the magnetic field generator further including a plurality of neodymium magnets bonded together by an adhesive. The magnetic field generator is heated to 200&#xb0; C.&#x2dc;1000&#xb0; C., then at least one of the plurality of neodymium magnets is removed; and a surface of the removed neodymium magnet is polished for reusing the neodymium magnet.

A magnetic field generator comprises a pair of pole-piece units. The pair of pole-piece units respectively include plate yokes. Each of the plate yokes includes a surface facing the other's and provided with a permanent magnet group and a pole piece. The pole piece includes an annular projection having a plurality of annular-projection pieces and a permanent magnet for reduction of magnetic flux leakage installed on an outside surface of each annular-projection piece. The permanent magnet for reduction of magnetic flux leakage may be disposed with a magnetizing direction thereof being slanted with respect to a main surface of the permanent magnet group.

Pole-piece unit, method for assembling the same, and magnetic field generator

It is an object of the present invention to provide a magnetic field generator for MRI with which it is possible to lower the residual magnetism and eddy current within pole pieces generated by the effect of the pulse current flowing through Gradient magnetic field coils, without decreasing the field uniformity within the air gap. Pole pieces in which a main component consisting of laminated silicon steel sheets is effectively combined with a magnetic annular protrusion disposed on the side on the main component facing the air gap, the result of which is the formation of a static magnetic field having the desired uniformity within the air gap without leading to a state of magnetic saturation in the vicinity of the magnetic annular protrusion . This also makes possible a reduction in the residual magnetism and eddy current within the pole pieces generated by the effect of the pulse current flowing through Gradient magnetic field coils.

Magnetic field generating device for MRI

A magnetic field generator comprises a pair of pole-piece units. The pair of pole-piece units respectively include plate yokes. Each of the plate yokes includes a surface facing the other's and provided with a permanent magnet group and a pole piece. The pole piece includes an annular projection having a plurality of annular-projection pieces and a permanent magnet for reduction of magnetic flux leakage installed on an outside surface of each annular-projection piece. When assembling the pole piece, first, the permanent magnet for reduction of magnetic flux leakage is fixed on the outside surface of each annular-projection piece. At this time, the permanent magnet is slid on the flat outside surface of the annular-projection piece, to a desired position on the annular-projection piece, and then fixed. Each of the annular-projection pieces mounted with the permanent magnet is fixed on a base plate. At this time, the annular-projection piece is lowered on a guide stake attached on the base plate, allowing the stake into a guide hole formed in the annular-projection piece, thereby guiding the annular-projection piece onto the base plate. The pair of pole-piece units are magnetically connected by a column yoke. The permanent magnet for reduction of magnetic flux leakage may be disposed with a magnetizing direction thereof being slanted with respect to a main surface of the permanent magnet group.

A magnetic field generator comprises a pair of plate yokes opposed to each other with a space in between. Each plate yoke has a main surface on which a permanent magnet is disposed. A shielding magnet is provided each at a forward portion on an open side and at a rearward portion, of another main surface in the plate yoke. A magnetic spacer is placed between the plate yoke and the shielding magnet. When assembling, a shielding magnet is mounted on a main surface of the spacer, and then another main surface of the spacer is placed on the main surface of the plate yoke. The shielding magnet is covered by a nonmagnetic cover member. A distance not smaller than 2 mm is provided between an outer surface of the cover member and a surface of the shielding magnet. The plate yoke is provided with nonmagnetic legs.

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Takatsuki, Japan

Masaaki Aoki