JP2551273B2 - Magnetic field correction device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field correcting device for uniformly correcting a spatial magnetic field generated by a magnetic field generating coil of an electromagnet device used in a magnetic resonance imaging system or the like.

[0002]

2. Description of the Related Art FIG. 8 is a perspective view showing the structure of an electromagnet device including a conventional magnetic field correction device disclosed in, for example, Japanese Patent Laid-Open No. 3-40439, and FIG. 9 shows a mounting portion of the magnetic field correction device in FIG. It is a perspective view showing details. In the figure, 1 is a cylindrical magnetic field generating coil, and 2 is this cylindrical magnetic field generating coil 1.
Is a cryostat that cools to a very low temperature to keep it in a superconducting state and doubles as a magnet case. 3 is a magnetic body magnetic shield that forms the outer shell of the electromagnet device and shields the leakage magnetic field to the outside. Reference numeral 5 denotes a magnetic field correction device mounted on the case of the magnet, for correcting a non-uniform component of the magnetic field uniform space 4 as shown in FIG. 9, for correcting a magnetic field formed in a bar shape such as a soft iron wire. A magnetic body 6, a non-magnetic cylindrical body 7 made of, for example, polycarbonate for accommodating the required number of magnetic field correcting magnetic bodies 6, and both ends of the non-magnetic cylindrical body 7 are supported and fixed to the surface of the cryostat 2 with screws 8. And a lid plate 11 fixed to the pedestal 9 with a screw 10 to close the open end of the non-magnetic cylindrical body 7.

In the conventional magnetic field correction device constructed as described above, first, both ends of the non-magnetic cylindrical body 7 are pedestal 9 in advance.
Then, the pedestal 9 is fixed to the surface of the cryostat 2 with the screw 8, and then the magnetic field correcting magnetic body 6 is inserted into the non-magnetic cylindrical body 7. Thereafter, the lid plate 11 is fixed to the pedestal 9 with the screw 10 to close the open end of the non-magnetic cylinder 7. Due to this blockage, the magnetic field correcting magnetic body 6 is held against the magnetic attractive force of the magnetic field generated by the magnetic field generating coil 1 without protruding from the inside of the non-magnetic cylindrical body 7.

Next, the magnetic field homogeneity of the magnetic field uniform space 4 is measured, and if the magnetic field homogeneity needs to be adjusted, the lid plate 11 is removed from the pedestal 9 and the magnetic field correction magnetism in the non-magnetic cylinder 7 is measured. After the body 6 is taken in and out to increase / decrease the required amount of magnetic field-correcting magnetic material, the lid plate 11 is fixed again to the pedestal 9 to close the end of the non-magnetic cylindrical body 7, and the same magnetic field as above is applied. The magnetic field homogeneity of the uniform space 4 is measured again. As a result, if further adjustment is necessary, the above operation is repeated until the desired magnetic field homogeneity is obtained.

[0005]

Since the conventional magnetic field correction device is constructed as described above, although the magnetic field correction magnetic body 6 is constrained in the non-magnetic cylindrical body 7, Even the magnetic field correcting magnetic body 6 having the same effective length as that of the magnetic cylindrical body 7 is generated in the non-magnetic cylindrical body 7 by the external vibration such as the vibration generated by the gradient magnetic field coil used in the magnetic resonance imaging system. When the position of the non-magnetic cylinder 7 is changed in the radial direction and the magnetic field correcting magnetic body 6 shorter than the effective length of the non-magnetic cylinder 7 is used, the position is also changed in the longitudinal direction of the non-magnetic cylinder 7, so that the magnetic field is changed. The magnetic field distribution in the uniform space 4 changes.

In a strong magnetic field generated by the magnetic field generating coil 1 of, for example, 0.5 Tesla, the magnetic field-correcting magnetic body 6 receives an attraction force of 10 times or more of its own weight. It is very difficult to insert the magnetic field correcting magnetic body 6 from the opening of the magnetic cylindrical body 7 against the magnetic attraction force. Further, in the non-magnetic cylindrical body 7, the magnetic body 6 for magnetic field correction is provided.
If it becomes necessary to insert the additional magnetic field, the lid plate 11 that closes the open end of the non-magnetic cylindrical body 7 must be removed. Due to the magnetic attraction force of the above, it jumps out from the opening end of the non-magnetic cylinder 7 and poses a danger to the operator. Furthermore, the non-magnetic cylinder 7
Is closely attached to the case of the magnetic field generating coil 1, so that a magnetic field correcting magnetic body having a different shape and different output from the magnetic field correcting magnetic body 6 inserted in the non-magnetic cylindrical body 7 is used. There is a problem that the magnetic field generating coil 1 cannot be attached to the case.

The present invention has been made in order to solve the above-mentioned problems, and the magnetic field correcting magnetic body does not change its position due to external vibration, and has a magnetic attraction force in a strong magnetic field. By doing so, the adjustment work can be performed safely without the difficult work of inserting the magnetic field correction magnetic body from the small opening end, and furthermore, the magnetic field correction magnetic body having a shape intersecting with the magnetic field correction device at the mounting position can be mounted. The purpose is to obtain a magnetic field correction device capable of

[0008]

Means for Solving the Problems Claim 1 according to the present invention.
3. The magnetic field correction device according to claim 2, wherein a required number of bar-shaped magnetic field correction magnetic bodies are collectively fixed to a mounting plate that is attachable to and detachable from the case of the magnetic field generation coil.
In the first aspect, the magnetic field correcting magnetic body is bound to the mounting plate with a non-magnetic binding band, and the magnetic field correcting apparatus according to the third aspect is the magnetic field correcting magnetic body according to the first aspect, which is attached to the mounting plate with an adhesive. The magnetic field correction device according to claim 4, which is adhered,
In claim 3, the adhesive is a thermosetting adhesive applied to the magnetic field correcting magnetic body in advance, and the magnetic field correcting device of claim 5 is the case of the mounting plate and the magnetic field generating coil in claim 1. It secured a space between
According to a sixth aspect of the magnetic field correction device of the first aspect, the magnetic field correction magnetic body is dispersed and fixed to a plurality of mounting plates for each magnetic field component to be corrected.

[0009]

The binding band of the magnetic field correction device according to the present invention binds the magnetic field correcting magnetic body onto the mounting plate, and the adhesive is used to bond the magnetic field correcting magnetic body onto the mounting plate to generate a magnetic field due to external vibration. Prevents movement of the position of the correction magnetic body. or,
The mounting plate is removed from the case of the magnetic field generating coil to facilitate the mounting work of the magnetic field compensating magnetic body, and the space between the case of the magnetic field generating coil and the mounting plate is fixed to the magnetic field compensating plate. This enables attachment of another magnetic field correcting magnetic body having a different shape and different output from the magnetic body for use.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. 1 is a perspective view showing a configuration of an electromagnet device including a magnetic field correction device according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view showing a configuration of the magnetic field correction device in FIG. In the figure, the magnetic field generating coil 1, the cryostat 2, the magnetic substance magnetic shield 3 and the magnetic field uniform space 4 are the same as those of the conventional device in FIG.

Reference numeral 11 is a case of the magnetic field generating coil 1, 12 is a fixture fixed to the case 11, and 13 is a first nonmagnetic material having a tongue piece 13a formed on the lower surface as shown in FIG. Mounting plate, 14 is a rod-shaped magnetic field compensating magnetic body adhered to the mounting plate 13 in the required number , and 15 is L fixed to the case 11.
It is a character-shaped support fitting and is arranged at a position corresponding to the tongue piece 13a of the mounting plate 13. Reference numeral 16 is a second mounting plate, and a required number of rod-shaped magnetic field correcting magnetic bodies 17 are bonded together . A holding tool 18 has a recess 18a into which both ends of the second mounting plate 16 are fitted, and a fitting hole 18b in the side surface which is fitted into the recess 18a and into which a holding pin 19 is fitted.
In the space formed between the mounting plate 13 and the case
The magnetic field-correcting magnetic bodies 14 and 17 which are adhered to and disposed on 11
Other magnetic field correction magnetic substance different from the above, and the above 12 to 18
The magnetic field correction device 30 is configured with the.

In the magnetic field correction device 20 according to the first embodiment of the present invention which is fixed as described above, first, an epoxy adhesive, for example, is applied to the surfaces of the magnetic field correction magnetic bodies 14 and 17 in advance and semi-cured ( Attach in the state of (B stage). And
Based on the magnetic field distribution of the desired magnetic field uniform space 4 measured by the same method as the conventional device, the nonuniform magnetic field component analysis is performed to select the magnetic field correcting magnetic bodies 14 and 17 required for compensation. Next, as shown in FIG. 4, the selected magnetic substance 14 for magnetic field correction is tied to the first mounting plate 13 with, for example, a glass tape 21 and temporarily fixed, and then the heating heater box 22 as shown in FIG. The magnetic field compensating magnetic body 14 is attached to the first mounting plate 13 by putting it inside and heating it at about 120 ° C. for several tens of minutes to cure the adhesive.
Adhesively fixed on top.

In this way, the first mounting plate 13 to which the required number of magnetic field correcting magnetic bodies 14 are collectively adhered and fixed is placed on the fixing tool 12 and fixed by the mounting screws, and the tongue The piece 13a is fixed to the support fitting 15 with a mounting screw. When another magnetic field correction magnetic body 20 having a shape that cannot be mounted is required on the first mounting plate 13, the first mounting plate 13
Before fixing 13 to the fixture 12, it is adhered to the case 11 in advance by using an adhesive that cures at room temperature. Further, after the magnetic field correcting magnetic body 14 is attached, when the magnetic field homogeneity of the desired magnetic field uniform space 4 does not reach the desired value, or the electromagnet device is moved to a place where the surrounding magnetic body environment is different. If
It becomes necessary to newly attach the magnetic body for magnetic field correction to make the magnetic field distribution uniform.

In this case, the required number of magnetic field correction magnetic bodies 17 are newly selected, the magnetic field correction magnetic bodies 17 are provided on the second mounting plate 16, and the magnetic field correction magnetic bodies 17 are provided on the first mounting plate 13. The body 14 is adhered and fixed in the same manner as in the case where the second mounting plate 16 is attached, both ends of the second mounting plate 16 are fitted into the recesses 18a of the holder 18, and the holding pins 19 are fitted into the fitting holes 18b. After holding 16, the holder
18 is stacked on the first mounting plate 13 and fixed on the fixture 12 by mounting screws. After that, the magnetic field distribution in the uniform magnetic field space 4 is measured again, and when the work of mounting the magnetic field correcting magnetic body is required, the second mounting plate 16 is removed and the magnetic field correcting magnetic body 17 is added to bond the magnetic body. Therefore, it will be reheated, but the first and second mounting plates 13 and 16 will have magnetic field compensating magnetic bodies 14 and 17, respectively.
Since only the second mounting plate 16 needs to be reheated, the electric energy required for heating and curing can be small.

Example 2. In the first embodiment, the magnetic field correcting magnetic bodies 14 and 17 are adhesively fixed to the first and second mounting plates 13 and 16, respectively, with an adhesive, but as shown in FIG. First tie plate 13 with cable tie 23
It may be bound and fixed to.

Embodiment 3. Further, the above embodiments have been described magnetic field correction for magnetic 14 and 17 of the rod-shaped, that the bar-shaped but may be applied to plate-shaped magnetic field correction magnetic body 24 as shown in FIG. 7 Needless to say.

[0017]

As described above, according to the present invention, the required number of bar-shaped magnetic field correcting magnetic members are collectively fixed to the mounting plate which can be attached to and detached from the case of the magnetic field generating coil. It is possible to prevent the movement of the position of the magnetic field correction magnetic body due to the
Since the fixed mounting plate can be attached and detached, the magnetic field correction magnetic body can be mounted easily and easily, and a space is formed between the case of the magnetic field generating coil and the mounting plate. It is possible to provide a magnetic field correction device to which another magnetic field correction magnetic body having a different shape can be attached.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an electromagnet device including a magnetic field correction device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a magnetic field correction device in FIG.

FIG. 3 is a perspective view showing details of a first mounting plate which constitutes a main part of the magnetic field correction apparatus in FIG.

FIG. 4 is a perspective view showing a state in which a magnetic field correction magnetic body is temporarily attached to the first mounting plate in FIG.

FIG. 5 is a perspective view showing an outer appearance of a heater box used when thermosetting and adhering magnetic field correcting magnetic bodies to the first and second mounting plates, respectively.

FIG. 6 is a perspective view showing details of a first mounting plate that constitutes a main part of the magnetic field correction apparatus according to the second embodiment of the present invention.

FIG. 7 is a perspective view showing a shape of a magnetic field correcting magnetic body that constitutes a main part of a magnetic field correcting apparatus according to a third embodiment of the present invention.

FIG. 8 is a perspective view showing a configuration of an electromagnet device supplementing a conventional magnetic field correction device.

9 is a perspective view showing details of a mounting portion of the magnetic field correction device in FIG.

[Explanation of symbols]

 1 magnetic field generating coil 11 magnetic field generating coil case 13 first mounting plate 14, 17, 19, 24 magnetic field correcting magnetic body 16 second mounting plate 23 binding band 30 magnetic field correcting device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 39/04 8908-2G G01R 33/22

Claims (6)

(57) [Claims] 1. A bar-shaped magnetic field correction magnetic body is arranged around each magnetic field generation coil in a required number and arranged at each required position, and is generated by the magnetic field correction coil by the magnetic field correction magnetic body. in a magnetic field correction device for uniformly correcting the spatial magnetic field, comprising a mounting plate made of a nonmagnetic material detachable from the coil case for the upper Symbol field generation, the magnetic field correcting magnetic
The magnetic field correction device is characterized in that the body is fixed to the mounting plate for each of the required number of bodies to be assembled . 2. The magnetic field correction device according to claim 1, wherein the magnetic field correction magnetic body is bound to the mounting plate with a non-magnetic binding band. 3. The magnetic field correction device according to claim 1, wherein the magnetic field correction magnetic body is bonded to the mounting plate with an adhesive. 4. The magnetic field correction device according to claim 3, wherein the adhesive is a thermosetting adhesive previously applied to the magnetic field correction magnetic body. 5. The magnetic field correction device according to claim 1, wherein a space is secured between the mounting plate and the case of the magnetic field generation coil. 6. The magnetic field correction apparatus according to claim 1, wherein the magnetic field correction magnetic body is dispersed and fixed to a plurality of mounting plates for each magnetic field component to be corrected.