JPH0331048Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application This invention relates to a magnet device, and in particular, the invention is a magnet device that is equipped with a magnetic field generating means that generates a magnetic field in one region, and at least one set of coils arranged in the region, The present invention relates to a magnet device in which a winding form is provided with an electric conductor to form a plurality of sets of coil windings.

BACKGROUND OF THE INVENTION Magnet devices of this type are used in particular in the field of magnetic resonance (NMR) imaging. In NMR imaging, the main magnetic field is formed and at least one
Two gradient magnetic fields are superimposed. A gradient magnetic field is generated by at least one set of coils located within the main magnetic field.

Problems to be Solved by the Invention In such a magnet device, there is a problem in that when a current starts to flow through the coil, the windings of the coil suddenly move and collide with each other or strike the former. This is due to the fact that the coil windings are placed within another magnetic field. As a result, a noisy ringing sound occurs. In particular, since a patient is placed inside a magnet device used in an NMR device, the generation of such noise is not only undesirable, but also
This may cause damage to the equipment.

Means for Solving the Problems A feature of the magnet device of this invention is that a plurality of wires are embedded in a soft elastomer material to form an electrical conductor.

In this invention, the electrical conductor is formed by embedding multiple strands of wire in a soft elastomer material, rather than using an electrical conductor made of relatively thick electrical wire such as copper wire, so the electrical conductor is flexible. , and therefore has high buffering properties.

For example, an electrical conductor consists of approximately 900 copper wires,
Each strand, approximately 0.3 mm in diameter, is embedded in a PVC layer to form an electrical conductor with an outer diameter of approximately 13.5 mm.

Since such electrical conductors do not themselves sustain vibrations, they significantly dampen the movement that occurs when electricity is initiated through the coil. That is, the initial travel amplitude is the same as for conventional gradient coils, but the amplitude of the oscillations decays rapidly with each cycle because the mechanical oscillations are damped to a greater extent.

Although the movement can be significantly damped using the above, loading the electrical conductor windings between layers of elastic material, such as silicone rubber, further improves the damping effect and significantly reduces noise.

Additionally, the entire coil may be coated with a resin material such as silica fiber insulation stage epoxy resin. It may be coated with a material other than resin, such as concrete, as long as it has high density and stiffness.

Typically, the magnetic field generating means comprises at least one electrical coil, and when used in an NMR apparatus, the coil is superconducting. Typically, the gradient field coils are resistive (non-superconducting).

EXAMPLES Hereinafter, this invention will be explained in detail based on examples.

The magnet device for an NMR imaging device shown in FIGS. 1 and 2 includes a superconducting coil (not shown) housed in a cryostat 1. A cylindrical hole 2 with a main axis 3 is formed by a cryostat. A magnet device housed in the cryostat 1 generates a uniform steady magnetic field extending in the direction of the main axis 3 (Z). A winding form 4 reinforced with a spirally wound glass fiber is installed in the hole 2 coaxial with the main shaft 3, and a large number of gradient coils are arranged in this winding form 4.

As shown in FIG. 1B, the coils 5 and 6 in the X direction
are coil pairs 5A, 5B and coil pair 6, respectively.
A, 6B, and are arranged symmetrically with respect to the central plane 70 of the magnet device. Each coil 5A, 5B, 6
A, 6B has a circumferential extent as shown in FIG. 1A. In use, a gradient magnetic field is created along a second axis extending through the coil pair of each coil.

Each coil 5, 6 has a series of windings made of electrical conductor 20 and is wired as shown in FIG.
As is clear from FIG. 3, there is a first region 7 consisting of six turns in the circumferential direction, a second region 8 consisting of four turns spaced apart from this first region, and a two turn region spaced apart from this second region. A third region 9 is provided.

A conductor 20 is formed by embedding a large number of about 900 annealed copper wires in a PVC material. The diameter of each strand is approximately 0.3mm
The outer diameter of the conductor is approximately 13.5 mm. As mentioned above, such a conductor itself has a buffering effect, but if each region shown in FIG. 3 is coated with silicone rubber, the buffering effect is further improved. When stretched in a plane, a coil coated in this manner has an appearance as shown in FIG. 4, and the cross section of each region is as shown in FIGS. 5A to 5C. For example, conductor 20 in region 8 with coating 25 has four electrical conductor windings 21-24 as shown in FIG. 5B.

Then, as shown in FIG. 4, each covered coil is placed on the winding form 4, and as shown in FIG. 6, each covered coil and the winding form are further coated with an epoxy resin coating 26 and fixed. FIG. 6 shows a portion where the resin coating 26 covers the coil 6A.

In addition to the gradient coils 5, 6 in the X direction, the second A, 2
Two Y-direction gradient coils 11 as shown in Figure B,
12 will be provided. The Y-direction gradient coils are substantially the same as the X-direction gradient coils, but their positions on the former 4 are different, and the gradient magnetic field generated by the Y-direction gradient coils is approximately orthogonal to the X-direction gradient magnetic field.

Furthermore, in addition to the X-direction and Y-direction gradient coils, two sets of Z-direction gradient coils 2 as shown in FIG. 7A are provided.
7 and 28 are provided. Each coil 27, 28 has a first coil 29 with 23 turns and a second coil 30 with 3 turns, and each coil 29, 3 is coaxial with the main shaft 3.
0 are inserted into the circumferential grooves 31 and 32 in the winding form 4, respectively.

The conductors forming the first coil 29 and the second coil 30 are the same as those used for the X-direction and Y-direction gradient coils, but the number of copper wires is small at about 530,
The diameter of each strand is approximately 0.2 mm. All wires are embedded in PVC material such as Hypalon (trademark) and are approximately 11.5mm long.
gives the outer diameter of The silicone rubber coating for the Z-direction gradient coils is different from that for the X,Y-direction gradient coils. That is, the circumferential groove 32
For example, as shown in FIG. 7B, first, a first silicone rubber layer 33 is placed in the groove, and then it is cured. Next, the winding of the coil 30 is inserted into the groove 32 and stacked on the silicone rubber layer 33, and a second silicone rubber layer is placed on top of it, and is glued so that it is on the same plane as the outer surface of the winding form 4. do. When the current starts flowing through the coil, the two silicone rubber layers 33,3
4 has a substantial damping effect on the movement of the coil conductor.

To assemble such a magnet device, first
After loading the directional gradient coils 27 and 28 between the silicone rubber layers 33 and 34 in the groove, the X and Y directional gradient coils are attached on the surface of the former, and finally the whole is covered with a resin material. The product thus produced is inserted into the hole 2 of the cryostat 1.

[Brief explanation of the drawing]

FIG. 1A is a simplified end view of an embodiment of this invention showing a coil for generating an X-direction gradient magnetic field, and FIG. 1B is a first
Figure A is a front view, Figure 2A is a simplified end view of the embodiment of this invention showing a coil for generating a gradient magnetic field in the Y direction, Figure 2B is a front view of Figure 2A, and Figure 3 is a diagram showing the inside of one gradient coil. A connection diagram of the windings, FIG. 4 is a plan view of the covered winding circuit, and FIGS. 5A to 5C are cross-sectional views taken in the direction of arrows A-A, B-B, and C-C in FIG. 4. ,
FIG. 6 is a partially cutaway front view of the embodiment of this invention, FIG. 7A is a partially cutaway front view of the embodiment of this invention showing a Z-direction gradient coil, and FIG. 7B is a cross-section of the Z-direction gradient coil of FIG. 7A. It is a diagram. 4... Winding form, 5, 6, 11, 12, 27, 28
... Coil set, 20-24, 30, 31 ... Electric conductor.

Claims (1)

[Claims for Utility Model Registration] 1. Comprising a magnetic field generating means for generating a magnetic field in one region and at least one set of coils disposed within the region, a plurality of coils are provided with an electric conductor on a rigid winding former. 1. A magnet device characterized in that a winding is formed, and a plurality of wires are embedded in a soft elastomer material to form an electric conductor. 2. A magnet device according to claim 1 of the utility model registration, characterized in that an electric conductor winding is loaded between layers of elastic material. 3 In claim 2 of the utility model registration claim, the winding form is substantially cylindrical, has an opening facing outward in the radial direction, and at least one set of coil windings is inserted into a circumferential groove formed in the winding form. A magnet device characterized by the fact that it is attached to a magnet. 4 Utility Model Registration A magnet device according to any one of claims 1 to 3, characterized in that at least one set of coil windings is embedded in an elastic material and arranged on the surface of a winding former. 5. A magnet device according to any one of claims 2 to 4 of the utility model registration, characterized in that the elastic material is silicone rubber. 6. A magnet device according to any one of claims 1 to 5 of the utility model registration claim, characterized in that the soft elastomer material is PVC. 7. A magnet device according to any one of claims 1 to 6 of the utility model registration claim, characterized in that at least one set of coils is entirely covered with a resin material.