JP3629656B2 - Superconducting magnet device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a superconducting magnet device with a superconducting coil, and more particularly to an improvement to allow adjustment of a Gaussian line around the device. Such a superconducting magnet device is particularly suitable for a superconducting magnet device for MRI (Magnetic Resonance Imaging).
[0002]
[Prior art]
A device using a superconducting magnet device as a magnetic field generation source in MRI for diagnostic imaging is well known as a superconducting magnet device for MRI. In general, in a superconducting magnet device, a leakage magnetic field is unavoidable. Such a leakage magnetic field affects diagnosis accuracy especially in the superconducting magnet apparatus for MRI in consideration of the installation environment. For example, suppose that the MRI superconducting magnet device 40 is installed at a site adjacent to a steel pillar 41 as shown in FIG. In this case, for example, a 5 gauss line around the MRI superconducting magnet device 40 is affected by the magnetic column 41 and has a shape indicated by a one-dot chain line. However, it is desirable that the Gaussian line is uniform around the MRI superconducting magnet device 40. For this reason, it is preferable that the shape of the Gaussian line around the MRI superconducting magnet device can be arbitrarily adjusted.
[0003]
On the other hand, it is conventionally known to provide a coil called a backing coil in order to minimize the leakage magnetic field. This backing coil is made of the same superconducting wire as the superconducting coil and is connected in series to the superconducting coil in the MRI superconducting magnet device 40, and acts to cancel the leakage magnetic field.
[0004]
[Problems to be solved by the invention]
However, the superconducting magnet device for MRI equipped with the backing coil is manufactured only in the same form, and it is not possible to adjust the Gaussian line according to the actual situation and installation environment of the site where the superconducting magnet device for MRI is installed. Can not.
[0005]
Therefore, an object of the present invention is to provide a superconducting magnet device in which the shape of a Gaussian line around the device main body can be arbitrarily adjusted.
[0006]
[Means for Solving the Problems]
The present invention is a superconducting magnet device provided with a superconducting coil, wherein a plurality of permanent magnets can be detachably attached to the casing of the device to enable adjustment of a Gaussian line around the device. And
[0007]
Specifically, a band surrounding the device is provided in the casing of the apparatus, and the permanent magnet is detachably attached to the band.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 1, the case where the embodiment of the present invention is applied to a superconducting magnet apparatus for MRI will be described. In FIG. 1, a band 12 surrounding the casing 11 of the MRI superconducting magnet apparatus 10 is provided, and a plurality of permanent magnets 13 are detachably attached to the band 12. Here, two bands 12 are provided at intervals in the central axis direction of the apparatus, and the permanent magnets 13 are detachable at intervals. In particular, the band 12 has a guide rail so that the position of the permanent magnet 13 can be shifted in the circumferential direction of the apparatus and can be fixed at an arbitrary position. The band 12 itself can also be displaced in the direction of the central axis of the apparatus with respect to the housing 11.
[0009]
The material of the band 12 is preferably a steel material, but may be anything such as a resin material. The material of the permanent magnet 13 is not limited, such as a ferrite magnet.
[0010]
FIG. 2 shows an example of a band 12 for making the permanent magnet 13 detachable. The band 12 has a guide rail shape having folded portions on both sides, and a permanent magnet 13 is sandwiched therein. The permanent magnet 13 is pressed and fixed to the band 12 by a presser fitting 14 and a screw 15. If the screw 15 is loosened, the permanent magnet 13 can slide along the band 12. In order to make the permanent magnet 13 detachable from the band 12, for example, as shown in FIG. 2B, a cutout is provided in the folded portion in the middle of the band 12 so that the permanent magnet 13 can be taken out. Just do it.
[0011]
The band 12 having such a structure is merely an example, and the attachment structure of the permanent magnet 13 may be any structure as long as it can be attached to an arbitrary position of the housing 11.
[0012]
The permanent magnet 13 is attached in consideration of the polarity so as to cancel the leakage magnetic field from the apparatus. As described above, since the plurality of permanent magnets 13 can be attached to arbitrary positions of the casing 11 of the apparatus, the shape of the Gaussian line having an arbitrary value formed by the leakage magnetic field of the apparatus is desired. The shape can be adjusted.
[0013]
FIG. 3 shows a case where the MRI superconducting magnet device 10 is installed at a site adjacent to the steel column 21 as described in FIG. Even in such a case, by adjusting the mounting position of the permanent magnet 13, for example, a 5 gauss line is formed in a uniform circle around the MRI superconducting magnet device 10 as shown by a one-dot chain line in FIG. 3. It can be shaped. Needless to say, the adjustment of the attachment position of the permanent magnet 13 is performed while measuring the magnetic field intensity around the device. Further, FIG. 3 shows the planar shape of the Gaussian line as viewed in a plan view, but it goes without saying that the shape adjustment of the Gaussian line is possible in the three-dimensional direction.
[0014]
FIG. 4 shows an example of forming a 5 Gauss line in an arbitrary shape by a one-dot chain line. This shape means that it is assumed in advance that there is something that affects the magnetic field on the right side of the MRI superconducting magnet apparatus 10 in FIG. Of course, the shape is not limited to the shape shown in FIG.
[0015]
Note that, as indicated by a broken line in FIG. 1B, a plurality of permanent magnets may be attached to a band extending in the central axis direction of the apparatus in the housing 11.
[0016]
The superconducting magnet device 10 for MRI according to the present embodiment is not limited to a stationary object having magnetism, that is, a site affected by the pillar 21 made of steel as described in FIG. It is also suitable for sites that are installed near roads, highways, and railroads where magnetic mobile objects pass. In such a site, in the conventional superconducting magnet device for MRI, the Gaussian line is disturbed every time the moving metal passes, and the diagnostic accuracy is affected. On the other hand, according to this embodiment, it is possible to form a Gaussian line having a predetermined shape in consideration of the influence of the moving metal in advance.
[0017]
The scope of application of the present invention is not limited to the superconducting magnet device for MRI, but can be applied to all superconducting magnet devices that require adjustment of the shape of the Gaussian line due to the leakage magnetic field.
[0018]
【The invention's effect】
According to the present invention, a plurality of permanent magnets can be attached to any position of the casing of the superconducting magnet device, thereby canceling the leakage magnetic field of the superconducting magnet device and adjusting the Gaussian line of any value. It can be combined with functions. Therefore, it is possible to form a Gaussian line having an arbitrary value according to the actual state of the site where the superconducting magnet device is installed. In particular, since an expensive material such as a superconducting wire is not required, it can be realized at a low cost. Also, adverse effects due to the moving metal can be prevented.
[Brief description of the drawings]
FIG. 1 is a view showing a superconducting magnet device for MRI according to the present invention, in which FIG. 1 (a) is a side view and FIG. 1 (b) is a view seen from an oblique direction.
FIGS. 2A and 2B are diagrams showing an example of a structure and an example for making a permanent magnet attachable to and detachable from a band according to the present invention. FIG. 2A is a cross-sectional view, and FIG.
3 is a diagram showing an example of a planar shape of a 5-Gauss line of the MRI superconducting magnet apparatus according to FIG. 1; FIG.
4 is a diagram showing another planar shape of a 5-Gauss line of the MRI superconducting magnet apparatus according to FIG. 1; FIG.
FIG. 5 is a diagram showing an example of a planar shape of a 5-Gauss line of a conventional MRI superconducting magnet apparatus.
[Explanation of symbols]
10, 40 Superconducting magnet device for MRI 11 Housing 12 Band 13 Permanent magnet 14 Holding bracket 15 Screws 21 and 41 Pillar

Claims (2)

A superconducting magnet device provided with a superconducting coil, wherein a plurality of permanent magnets can be detachably attached to the casing of the device to enable adjustment of a Gaussian line around the device. Magnet device. 2. The superconducting magnet device according to claim 1, wherein a band surrounding the device is provided in a casing of the device, and the permanent magnet is detachably attached to the band.

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