Sumitomo Special Metals Co., Ltd.

Neomax Co., Ltd.

Tdk Corporation

Hitachi Metals, Ltd.

Hitachi Medical Corporation

Shigeo Hashimoto

Masaaki Aoki

Hitoshi Yoshino

Hideya Sakurai

Kimiharu Ohta

Masahiro Yuki

Shigemasu Okada

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

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 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.

Magnetic field generator for MRI, method for assembling the same, and method for assembling a magnet unit for the same

A method for dismantling a magnetic field generator, which includes the steps of providing a plate yoke, and a permanent magnet provided on the plate yoke and having a plurality of neodymium magnets bonded together by an adhesive for the magnetic field generator; heating the magnetic field generator at a temperature of 200&deg; C.&tilde;1000&deg; C.; and thereafter dismantling the magnetic field generator. The dismantling method further includes the step of providing a column yoke connected to the plate yoke for the magnetic field generator.

Method for dismantling a magnetic field generator

A magnetic field generator for MRI comprises a pair of plate yokes opposed to each other with space in between. A magnet is provided in each of the opposed surfaces of the pair of plate yokes. A column yoke is connected to the pair of plate yokes. An enhancing member made of magnetic material and having a curved slant face is provided in an inner surface of the connection between the column yoke and the plate yokes at a place farthest from the magnet. A first bolt of magnetic field adjusting bolts is screwed into the plate yoke, with a tip of the first bolt contacting the enhancing member. A second bolt of the magnetic field adjusting bolts is screwed into the plate yoke, with a tip of the second bolt contacting an upper end face of the column yoke. An engaging portion for engagement of the enhancing member with the yoke may be provided.

A magnetic field generator for an MRI includes a generator main body. The generator main body includes a pair of plate yokes opposed to each other with space in between, a permanent magnet disposed in each of the opposed surfaces of the plate yokes, and a column yoke for magnetically connecting the plate yokes. As a packing member, a shielding member, and if necessary, a stud pin as well as a fixing member are prepared. When packing, the shielding member is attached to the generator main body for shielding an opening. The stud pin may be used for providing a gap between the generator main body and the shielding member. For an open-type generator, the fixing member should preferably be attached to bridge the pair of plate yokes at a middle portion of the opening.

Magnetic field generator for MRI, packing member for the same, and method for packing the same

An object of the present invention is to provide an MRI magnetic field generator with which the magnetic field uniformity within the imaging field of view of the air gap can be adjusted easily and safely, without having to detach the gradient coils, after the MRI magnetic field generator has been installed with gradient coils already mounted on a pair of magnetic pole pieces. After the holder disk,has been placed on and fastened to the base disk,the magnetic material pellets or permanent magnet pellets for adjusting the magnetic field uniformity are inserted into the required pits disposed in a specific pattern, and if needed, spacers are placed in the gaps between &lsqb;the pellets&rsqb; and the cover disk,to position everything, after which the cover disk,is screwed on to hold everything together. The resulting shim holder,is aligned with and fastened to the gradient coil,or its support member.

MRI magnetic field generator

Magnetic field generating device for use in MRI

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.

A magnetic field generating apparatus has a permanent magnet arrangement for generating a magnetic field in a magnetic field generating space and a yoke arrangement for forming magnetic circuits for generation of the magnetic field together with the permanent magnet arrangement. The yoke arrangement includes a first pair of yokes arranged facing each other, a second pair of yokes arranged facing each other through which the first pair of yokes are magnetically connected to each other, a third pair of yokes arranged between one end of one of the first pair of yokes and one end of one of the second pair of yokes and between the other end of the one of the first pair of yokes and one end of the other of the second pair of yokes, respectively, and yoke moving units for independently moving the one of the first pair of yokes and each of the second pair of yokes with respect to the third pair of yokes, respectively.

Growing community of inventors

Saga, Japan

Shigeo Hashimoto