JPH0482536A - Magnet apparatus for mri - Google Patents

Abstract

PURPOSE:To allow no adverse effect on an output image of an MRI apparatus by forming a magnet apparatus from a plate-shaped insulation magnetic pole member with magnetic pole pieces thereof so arranged as to make a thickness- wise direction thereof vertical to a direction of a magnetic field. CONSTITUTION:A pulse-like magnetic field (b) is applied to a magnet apparatus 10 for MRI from a gradient magnetic field coil. As a result, the pulse-like magnetic fields (b) hit silicon steel plates 12a, 12b... in a direction the same as the direction of a magnetic field B and normally, an eddy current flows vertical to the direction of the magnetic field B. But as the silicon steel plates 12a, 12b... are treated to insulate, a flow of the eddy current is prevented on a magnetic pole piece 12 by the pulse-like magnetic fields from the gradient magnetic coil. This also prevents the generation of a magnetic field otherwise generated eventually. The magnet apparatus for MRI thus obtained allows no adverse effect on an output image of an MRI apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an MRI magnet device that forms a static magnetic field in, for example, an MRI apparatus.

(Prior Art) Generally, this type of MRI magnet device consists of permanent magnets 1, 1 arranged opposite to each other as shown in FIG. , 2 and a yoke 3 that magnetically couples the permanent magnets 1, 1, and forms a magnetic field between the magnetic pole pieces 2, 2. The magnetic pole pieces 2, 2 are made of pure iron.

(Problems to be Solved by the Invention) However, in the conventional apparatus shown in FIG. There is a problem in that it adversely affects the output image.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an MRI magnet device that does not adversely affect output images of an MHI device.

[Configuration of the Invention (Means for Solving the Problems) To achieve the above object, the configuration of the present invention includes permanent magnets arranged opposite to each other, magnetic pole pieces provided on opposing surfaces of these permanent magnets, and a yoke that magnetically couples the permanent magnets to form a magnetic field between the magnetic pole pieces. It is characterized in that it is formed of an insulated magnetic pole member, and the plate-shaped insulated magnetic pole members are arranged in parallel in a standing state along the outer periphery of a coaxial core; The insulated magnetic pole member is characterized by being made of a silicon steel plate.

(Function) The function of the present invention having the above configuration is that the plate-shaped insulated magnetic pole member, which is arranged so that the thickness direction of the magnetic pole piece is perpendicular to the magnetic field direction, is affected by the pulsed magnetic field from the gradient magnetic field coil. It prevents the flow of eddy currents on the pole pieces and the generation of magnetic fields thereby generated. Further, the plate-shaped insulating magnetic pole members are arranged in parallel along the outer periphery of the coaxial core in a standing state, and further, the plate-shaped insulating magnetic pole members are made of silicon steel plates, so that the effect is remarkable.

(Example) An example of the present invention will be described in detail below with reference to the drawings.

An MRI magnet device 1 according to an embodiment of the present invention shown in FIG.
0 is permanent magnets 11.11 arranged opposite to each other and a magnetic pole piece 12 provided on the opposing surface of these permanent magnets 11.11.
．． 12 and a yoke 13 that magnetically couples the permanent magnets 11.degree. 11 to form a magnetic field between the magnetic pole pieces 12.12.

As shown in FIG. 2, the magnetic pole pieces 12.12 are arranged so that the plate thickness direction is perpendicular to the direction of the static magnetic field B (in the direction of the arrow in the figure), and the pole pieces 12.12 are arranged along the outer periphery of the coaxial core P. silicon steel plates (plate-shaped insulated magnetic pole members) 12a arranged in parallel in the state;
12b... Note that the silicon steel plate 12a.

12b... have already been subjected to insulation treatment in the manufacturing process.

Next, referring also to FIG. 3, the operation of the MRI magnet device 10 having the above configuration will be described.

A pulsed magnetic field S, b from a gradient magnetic field coil (not shown) is applied to the MRI magnet device 10. Then, these pulse-shaped magnetic fields S, B strike the silicon steel plates 12a, 12b, etc. in the same direction as the magnetic field B (see Figure 3), and normally the eddy currents are perpendicular to the direction of the magnetic field B. However, the silicon steel plates 12a, 12b...
Since it is insulated, it prevents the flow of eddy current on the magnetic pole piece 12 due to the pulsed magnetic field from the gradient magnetic field coil, and also prevents the generation of a magnetic field generated thereby.

As a result, according to the MRI magnet device having the above configuration, MR
This eliminates any negative influence on the output image of the I device.

Furthermore, the magnetic properties of the silicon steel plates 12a, 12b, . . . are almost the same as those of pure iron, and the hysteresis is also small, so that the influence on the static magnetic field B is also reduced.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above embodiment, and can be modified as appropriate within the scope of the gist of the present invention.

For example, the plate-shaped insulating magnetic pole member is not limited to a silicon steel plate and can be modified in various ways, and as shown in FIG. 4, the magnetic pole piece 14 is a plate-shaped insulated magnetic pole member 14a.

14b may be formed in parallel arrangement, and even in this case, the same effect as described above can be obtained.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an MRI magnet device that does not adversely affect output images of an MRI device.

[Brief explanation of the drawing]

FIG. 1 is a schematic front sectional view showing one embodiment of the MRI magnet device according to the present invention, FIG. 2 is a schematic partial perspective view for explaining one embodiment of the MRI magnet device according to the present invention, and FIG. FIG. 3 is a schematic partial perspective view of a magnetic pole piece for explaining the operation of an embodiment of the present invention, FIG. 4 is a perspective view showing a modified example of the magnetic pole piece, and FIG. 5 is a front sectional view of a conventional device. be. 0... MRI magnet device, 11... Permanent magnet, 12... Magnetic pole piece,

Claims (3)

[Claims] (1) Consisting of permanent magnets arranged to face each other, magnetic pole pieces provided on opposing surfaces of these permanent magnets, and a yoke that magnetically couples the permanent magnets, and forms a magnetic field between the magnetic pole pieces. A magnet device for MRI, characterized in that the magnetic pole piece is formed of a plate-shaped insulated magnetic pole member arranged such that the plate thickness direction is perpendicular to the magnetic field direction.
Magnet device for RI. (2) The MRI magnet device according to claim 1, wherein the plate-shaped insulated magnetic pole members are arranged in parallel in a standing state along the outer periphery of a coaxial core. (3) The MRI magnet device according to claim 1 or 2, wherein the plate-shaped insulating magnetic pole member is a silicon steel plate.