JPH01254154A - Magnetic field correcting device - Google Patents

Abstract

PURPOSE:To accurately and easily execute magnetic field correction by moving a magnetic substance piece along a rail or a cylindrical body and adjusting the position of the piece. CONSTITUTION:In the inner surface of a cylinder 5 of a nonmagnetic substance, plural linear rails 6 and ring rails 7, which are coaxial with the cylinder 5, are respectively fit in parallel with the central shaft of the cylinder 5. Here, the rails 6 and 7 and cylinder 5 are fixed by welding, etc. This cylinder 5, on which the rails 6 and 7 are arranged, is fit to the normal temperature bore of a superconductive magnet for MRI. a steel piece 1, whose cross section is rectangular, is fit to the rail 6, slided up to a prescribed position and fixed by a tape or adhesive, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic field correction device for a magnetic resonance imaging apparatus (MRI apparatus).

(Prior Art) Superconducting magnets are widely used in MHI devices because the higher the magnetic field used, the better the image quality.

In addition, the diagnostic space inside the magnet requires a highly uniform magnetic field, so it is designed with high precision. Due to the influence of certain magnetic substances, the uniformity of the magnetic field in the actual diagnostic space deteriorates, so a magnetic field correction device is used, and one of the correction devices is a small piece of iron called an iron shim. This iron piece 1 is stuck inside the normal temperature bore 3 of the superconducting magnet 2 as shown in FIG. 11 to correct the magnetic field in the diagnostic space 4.

During correction, until the specified magnetic field uniformity is achieved.

A plurality of iron pieces 1 are pasted at appropriate locations within the bore 3.

(Problems to be Solved by the Invention) As mentioned above, in an MHI device, using a superconducting magnet to create a high magnetic field provides a better image, but when using a high magnetic field, the electromagnetic force acting on the iron piece increases, making it difficult to attach the iron piece. There is a problem that it becomes difficult to correct the magnetic field because it becomes difficult or the attached iron piece comes off. Furthermore, if it is fixed with a strong adhesive, there is a problem that it will be difficult to remove it during the correction process.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a magnetic field correction device that prevents the iron piece from coming off and has a structure that allows easy correction.

(Structure of the Invention) (Means for Solving the Problems) In the present invention, as shown in FIG. A plurality of linear rails 6 made of non-magnetic material are attached in parallel with the cylindrical body 5, and magnetic pieces are attached to the rails.Alternatively, magnetic pieces are attached to the cylindrical body 5.

(Function) With this structure, it is possible to adjust the device by moving the magnetic piece along the rail or cylindrical body.
Magnetic field correction can be performed precisely and easily.

(Example) An example of the present invention is shown in FIG. On the inner surface of the non-magnetic cylinder 5, parallel to the central axis of the cylinder 5, a plurality of non-magnetic straight rails having a cross section as shown in FIG. 2 and a ring rail 7 coaxial with the cylinder 5 are provided. Attach. Here, the rail and cylinder are fixed by welding or the like. The cylinder 5 with such a rail is attached to the two-warm bore 3 of a super conductive groove magnet for MRI as shown in FIG.

The cross sections of the straight rail 6 and the ring rail 7 are shaped like a curtain rail, as shown in FIG. As shown in Figure 3, fit the iron piece 1 with a rectangular cross section or the iron piece 1' with a convex cross section into the rail of this type, slide it to a specified position, and fix it with tape or adhesive. . Also.

In the case of ring rail 7, as shown in Figure 4, one of the rings
Notches 9 are provided at several locations, from which the rectangular parallelepiped iron piece 1 or the convex iron piece 1' is fitted, brought to a predetermined position, and fixed. Further, by attaching a protrusion 10 to the outer periphery of the ring rail 7, the ring rail 7 can be fitted into the linear rail 6 attached to the inner surface of the cylinder 5, as shown in FIG. By doing so, it is possible to slide the ring rail 7 in the axial direction and place the ring rail 7 at an arbitrary position.

In this way, the cylinder 5 to which several straight rails and several ring rails are attached is connected to the groove conductive magnet 2 for MRI.
Install it inside the warm bore 3 as shown in Figure 6.

With this configuration, since the iron piece is fitted into the rail, the iron piece will not come off even if an electromagnetic force is applied, and the magnetic field can be easily corrected.

The shape of the iron piece is a rectangular parallelepiped iron piece 1 as shown in FIG. 3 or a convex iron piece 1'. Further, a protrusion 10 is attached to the outer periphery of the ring rail 7 as shown in FIG.
Fit it into the straight rail 6 attached to the inner surface of the cylinder as shown in the figure. With such a configuration, the ring rail 7 can move in the axial direction.

To fit the iron piece 1 or 1' onto the straight rail 6, it is fitted by sliding it from both ends of the straight rail 6. In order to fit the iron piece 1 or 1' into the ring rail 7, insert the iron piece 1 or 1' into the ring rail 7 from the notch 9 (Fig. 4).
’ and slide it in the circumferential direction. Use adhesive tape or the like to secure the iron pieces to the rails.

In this way, the magnetic field is corrected using several or dozens of iron shims until a predetermined magnetic field uniformity is achieved, and once the position of the iron piece is determined, it is fixed with adhesive or the like.

This configuration has the effect of preventing the iron piece from coming off even if the magnetic field is high and the electromagnetic force increases.Also, since the iron piece can be moved within the rail, the capacity is reduced.
This has the effect of easily correcting the magnetic field using the iron piece.

(Other Embodiment 1) Another embodiment of the iron piece fixing method is shown in FIGS. 7 and 9.
This is a cylinder 5 made of non-magnetic material with several bolt holes 11 drilled therein, and a rectangular parallelepiped iron piece 1'' with holes 11' for passing bolts as shown in FIG. It is fixed.

In this way, by drilling a large number of bolt holes 11 in the cylinder 5, the iron piece 1' can be fixed with the bolts 12.
' has the effect of not being removed by electromagnetic force, and has the effect of making it easy to correct the magnetic field.

(Other Embodiment 2) FIG. 10 shows a linear rail 6 directly attached to the normal temperature bore 3 of the superelectric magnet 2 for MRI.

Even with such a configuration, the same effect as when using the cylinder shown in FIG. 1 can be obtained.

〔Effect of the invention〕

As described above, the magnetic field correction device of the present invention has the effect that the iron shims do not come off even if the electromagnetic force increases due to a high magnetic field, and the iron shims can be fixed at any position, making it easy to correct the magnetic field. 6.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the magnetic field correction device of the present invention;
Figure 2 is a sectional view of the rail used in the above embodiment, Figure 3 is a diagram showing the straight rail used in the above embodiment and the iron piece fitted into it, Figure 4 is a diagram showing the ring rail used in the same device, Figure 5 shows the ring rail fitted into the straight rail, Figure 6 shows the magnetic field correction device of the present invention fitted into an MRI magnet, and Figure 7 shows the magnetic field correction device of the present invention and other parts. FIG. 8 is a cross-sectional view of the iron piece used in the device shown in FIG. 7, and FIG. 9 is a view showing the iron piece shown in FIG. 8 attached to the device shown in FIG. 7. , 10th
This figure shows a modified example of FIG. 1 in which a rail is directly attached to a superconducting magnet, and FIG. 11 shows a conventional device in which an iron shim is attached to the normal temperature bore of a superconducting magnet. 1.1', 1'... Iron shim 2... Superconducting magnet for MRI 5... Cylinder 6... Straight rail 7... Ring rail 10... Protrusion 11
...Bolt Hole Agent Patent Attorney Nori Ken Chika Yudo Ken Daishimaru Figure 2 Figure 3 O Figure 4 Figure 5 V! J Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] A magnetic field correction device characterized in that a magnetic piece is attached to a cylindrical or cage-shaped support formed by a ring rail and a straight rail provided inside a cylindrical magnet body.