JP2002093616A - Open-type superconducting magnet device and magnetic resonance imaging equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a open-type superconducting magnet for MRI equipment, where a subject would sense openness when he undergoes a medical examination, and an operator is improved in accessibility to the subject from sideways. SOLUTION: A superconducting magnet is composed of an upper superconducting coil 10 and a lower superconductive coil 12, an upper magnetic plate 20 and a lower magnetic plate 22 are provided, so as to restrain a leakage magnetic flux, magnetic material poles 24 and 26 are provided to support the magnetic plates 20 and 22, and an upper cooling vessel 16 and a lower cooling vessel 18 house the superconducting coils 10 and 12 and the magnetic material poles 24 and 26. Connecting tubes 44 and 46 linking the cooling vessels 16 and 18 are, so disposed at positions as to overlap with each other as seen from the center of a uniform magnetic field space 14 and so to be located toward the inner side in the direction, into which the subject is introduced, and a refrigerator 48 for cooling down the superconducting coils 10 and 12 is provided above the upper magnetic material plate 20 and apart from the magnetic material poles 24 and 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an open side for use in a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus), which is excellent in terms of accessibility to a subject and a feeling of openness of the subject. The present invention relates to an improvement of an open type superconducting magnet device comprising a pair of superconducting coils arranged vertically opposite each other as a magnetic field generating source.

[0002]

2. Description of the Related Art This type of open superconducting magnet apparatus for an MRI apparatus is disclosed in, for example, Japanese Patent Application Laid-Open Nos.
234746. In the open-type superconducting magnet device disclosed in these prior arts, a pair of upper and lower donut-shaped cooling containers accommodating a pair of superconducting coils disposed vertically facing each other are electrically, thermally or structurally. Sufficient consideration has not been given to the structure and arrangement of the connecting pipes to be connected and the structure and arrangement of the refrigerator for cooling the pair of superconducting coils housed in the pair of upper and lower cooling vessels, respectively. The tube and the refrigerator were also a factor that hindered the operator's accessibility to the subject and the open feeling of the subject.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an open superconductivity for an MRI apparatus which gives a subject a high sense of openness and gives a surgeon high access to the subject and a wide working space. It is to provide a magnet device.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a refrigerator for cooling a pair of upper and lower superconducting coils housed in a pair of upper and lower cooling vessels, respectively. The pair of upper and lower magnetic material plates disposed on the upper side are disposed on the upper magnetic material plate of the pair of upper and lower magnetic material plates at a position distant from the magnetic material column that is magnetically and mechanically coupled. This is achieved by connecting the upper cooling container of the pair of upper and lower cooling containers through a cutout formed in the magnetic material plate.

The object of the present invention is further to provide a magnetic material column that magnetically and mechanically couples a pair of upper and lower magnetic material plates disposed above and below a pair of upper and lower cooling vessels. A pair of superconducting coils formed by a pair of upper and lower superconducting coils housed in a donut-shaped cooling container are arranged so as to be deviated from the center of the uniform magnetic field space to the back for performing MRI imaging, and a pair of upper and lower cooling units are provided. Electrical container,
The connecting pipe thermally connected is also arranged in substantially the same direction as the arrangement direction of the magnetic material columns when viewed from the center of the uniform magnetic field space, and is arranged outside the outer periphery of a pair of upper and lower donut-shaped cooling vessels. Achieved by

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An open superconducting magnet apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG.

When a DC exciting current in the same direction flows through a pair of upper and lower symmetrically arranged superconducting coils 10 and 12, a uniform static magnetic field is generated vertically between the pair of upper and lower superconducting coils 10 and 12. Then, a uniform magnetic field space 14 for inserting a subject and performing MRI imaging is provided in the center of the magnet.
Is formed.

The pair of upper and lower superconducting coils 10 and 12 are accommodated in a pair of upper and lower cooling vessels 16 and 18, respectively.

A pair of upper and lower magnetic material plates 20 and 22 are arranged close to the superconducting coils 10 and 12, respectively, outside the superconducting coils 10 and 12 in order to suppress a leakage magnetic field to the outside of the magnet device. The magnetic material plates 20, 22 are magnetically coupled by two magnetic material columns 24, 26 and are structurally supported.

Inside the pair of upper and lower superconducting coils 10, 12, pole pieces 28, 3 having a pair of upper and lower protrusions are provided.
0 is provided. Each pole piece 28, 3
A pair of upper and lower gradient magnetic field coils 32 and 34 for providing positional information in a static magnetic field are provided in the respective circular concave portions surrounded by zero. Behind the respective gradient magnetic field coils 32 and 34, a magnetic field uniformity control member 3 is provided.
6, 38 are provided.

In FIG. 1, the vertical direction of the paper is defined as the Z direction, the horizontal direction as the X direction, and the vertical direction as the Y direction.

FIG. 2 shows a superconducting coil 10 and a cooling vessel 16.
It is an enlarged view of the part. The superconducting coil 10 is arranged in a cooling vessel 16 for cooling to a predetermined temperature at which the superconducting properties can be exhibited. As the cooling vessel 16, the outermost part is surrounded by a vacuum tank 40, and a refrigerant tank (liquid helium tank in this embodiment) 42 is arranged inside the vacuum tank 40. Although not shown, a heat shield is arranged between the vacuum tank 40 and the refrigerant tank 42 to prevent the inflow of heat due to radiation, thereby preventing the heat from flowing into the refrigerant tank 42 (finally, the superconducting coil 10). It suppresses heat penetration.

Further, in the present superconducting magnet apparatus, the upper and lower cooling vessels 16, 18 are electrically, thermally, or structurally connected so as to withstand the electromagnetic force and load acting between the upper and lower superconducting coils 10, 12. Communication pipes 44 and 46 are provided. Similarly to the upper and lower cooling vessels 16 and 18, these connecting pipes 44 and 46 also include a vacuum tank and a refrigerant tank, and the upper and lower cooling vessels 16 and 18 are connected by the refrigerant tank so that the refrigerant communicates. I have. The upper and lower superconducting coils 1
In order to hold 0 and 12 at a predetermined distance, upper and lower support members may be arranged in the refrigerant tank. In this embodiment, the connecting pipe 4
The positions of the circumferential positions 4 and 46 in the circumferential direction are the same as the positions of the magnetic material columns 24 and 26 in the circumferential direction when viewed from the center of the uniform magnetic field space.

In this embodiment, use for an IVR or the like is considered.
Two connecting pipes 4 are provided so that the sides of the subject can be opened widely.
4, 46 are used, but the number is not limited to this.
It may be a book, or three or more. Further, in this embodiment,
As shown in FIG. 4 described below, the connecting pipes 44, 46,
By arranging the magnetic material columns 24, 26 asymmetrically in the front-rear direction, that is, on the back side in the subject insertion direction, a sufficiently wide space is formed on both sides on the front side.

To further explain the arrangement of the connecting pipes 44 and 46, FIG. 4 shows a central section viewed from above. In this embodiment, the subject is inserted into the magnet with the body axis in the Y direction, and the visual field in the X direction is defined by the distance W between the two connecting tubes 44 and 46. Therefore, if this interval is small, it is difficult to obtain a feeling of opening. As shown in the present embodiment, by arranging the connecting pipe further radially outward than the outer peripheral portion of the donut-shaped cooling container 18, the interval W can be increased and the openness can be enhanced.

In order to widen the interval between the connecting pipes 44 and 46, it is effective to provide a recess in the magnetic material columns 24 and 26 and to arrange the connecting pipes 44 and 46 having a soft structure between them. With this structure, the reduction in the cross-sectional area of the magnetic material columns 24 and 26 is minimized, so that the influence on the leakage magnetic field is small.

The upper and lower cooling vessels 16 and 18 are structurally connected by connecting pipes 44 and 46, so that the cooling vessel 1
Although it is possible to make the whole of 6, 18 into an integral structure,
In this embodiment, the cooling containers 16 and 18 are
0, 22 and the connecting pipes 44, 46 have a structure that only serves to electrically or thermally couple the upper and lower cooling vessels 16, 18, so that the distance between the upper and lower superconducting coils 10, 12 is equal to the magnetic material. Although it is indirectly defined by the columns 24 and 26, a higher rigidity can be obtained as a structure as compared with the case where it is supported by the connecting pipes 44 and 46. In addition, magnetic pillar 2
4, 26 have a larger cross-sectional area and a simpler structure,
Easy to obtain dimensional accuracy. As a result, the distance between the upper and lower superconducting coils as designed is easily obtained, and the uniformity of the magnetic field is easily increased.

As shown in FIGS. 1 and 3, in this embodiment, a refrigerator (compressor) 48 for cooling the superconducting coils 10 and 12 is disposed above the upper magnetic material plate 20. This eliminates the need for a space for disposing the refrigerator 48 on the side surface of the space surrounding the uniform magnetic field space, and thus improves the accessibility, workability, and openness from the side. Further, since the magnetic material plates 20 and 22 are interposed between the refrigerator 48 and the superconducting coils 10 and 12, the leakage magnetic field acting on the refrigerator 48 is greatly reduced. Since the performance of the cold storage material used in the refrigerator 48 generally deteriorates in a strong magnetic field, the use of this structure prevents the performance deterioration of the cold storage material.

Next, another embodiment of the present invention will be described with reference to FIGS.
I will explain using. The same parts as those in the previous embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Also in this embodiment, as shown in FIG. 3 of the previous embodiment, the arrangement of the connecting pipes 44, 46 and the magnetic material columns 24, 26 is circumferentially viewed from the center of the uniform magnetic field space 14. At the same position and orientation.

Also, in this embodiment, a refrigerator 48 for cooling the superconducting coil is disposed above the upper magnetic material plate 20, as in the previous embodiment.

Further, in the present embodiment, the magnetic material plate 20 corresponding to a portion connecting the refrigerator 48 and the cooling vessel 16 is provided.
Is cut out, and the two are connected using the space.
With this structure, the connection portion 50 does not protrude beyond the outer diameter of the upper cooling container 16, so that openness can be obtained. Further, the path can be made shorter than in a case where the cooling vessel 16 is connected around the periphery, so that the thermal resistance can be reduced. As a result, the cooling efficiency is improved, and the consumption of the refrigerant can be reduced. Alternatively, from another point of view, it is possible to cope with an increase in the amount of heat infiltration, so that advantages such as simplification of the structure of the cooling vessel and improvement in rigidity of the superconducting coil support structure can be obtained.

One of the advantages of disposing the refrigerator 48 in front of the magnetic material plate 20 as shown in FIGS. 4 and 5 is that the height of the magnet device can be reduced. The thickness of the magnetic material plate 20 for suppressing the leakage magnetic field needs to be selected according to the density of the magnetic flux passing therethrough. For this reason,
When the positions of the magnetic material columns 24 and 26 are arranged asymmetrically in the front-rear direction, the front of the magnetic material plate 20 having a low magnetic flux density can be made thin. Therefore, by arranging the cooler 48 at this position, the height of the entire apparatus can be reduced, and the transportation and loading of the apparatus become easy. Further, since the magnetic flux density of the magnetic material plate 20 in this portion is low, even if this portion is cut out, the influence on the leakage magnetic field and the uniformity of the magnetic field can be reduced.

Further, as the axial direction of the piston cylinder of the refrigerator 48 approaches the vertical direction, the operation efficiency of the refrigerator generally improves. Therefore, by arranging the refrigerator 48 obliquely as shown in FIGS. 4 and 5, the cooling efficiency can be increased. In addition, 52 is a support member of the refrigerator 48.

FIG. 6 shows a modification of FIG.
A flexible pipe 5 is used to connect the connecting portion between the cooling vessel 8 and the cooling vessel 16.
By tying at 0a, the vibration of the refrigerator 48 is prevented from being transmitted to the superconducting coil. Furthermore, the flexible connection allows the mounting position accuracy of the refrigerator 48 with respect to the cooling vessel 16 to be increased in an allowable range, thereby facilitating the assembling work. In addition, the first and second
In the embodiment of the present invention, the cooling vessel was used as a cooling vessel as a component, but in this modification, a conduction cooling system in which the superconducting coil 10 was directly cooled by the refrigerator 48 was adopted. The structure of the cooling container is simplified, and the space for the refrigerant tank is not required, so that the outer diameter of the entire magnet device is reduced.

[0026]

As described above, in the superconducting magnet device composed of a pair of upper and lower superconducting coils, a magnetic material column for supporting a pair of upper and lower magnetic plates for suppressing a leakage magnetic field and a pair of upper and lower cooling containers for accommodating the superconducting coils are also provided. A refrigerator that cools the superconducting coil by arranging the connecting pipes in such a direction that they overlap each other when viewed from the center of the uniform magnetic field space and at a position deviated to the back side in the direction in which the subject is inserted. By arranging it on the upper magnetic material plate and at the front position far from the magnetic material column, it enhances the openness of the subject and improves the operator's accessibility to the subject from the side. You can do it.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a first embodiment of an open superconducting magnet device of the present invention.

FIG. 2 is an enlarged sectional view of a superconducting coil unit in the first embodiment of FIG.

FIG. 3 is a schematic cross-sectional view of the first embodiment of FIG. 1;

FIG. 4 is a schematic longitudinal sectional view of a second embodiment of the open superconducting magnet device of the present invention.

FIG. 5 is a schematic longitudinal sectional view of a third embodiment of the open superconducting magnet device of the present invention.

FIG. 6 is a schematic longitudinal sectional view of a modification of the third embodiment of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Superconducting coil 12 Superconducting coil 14 Uniform magnetic field space 16 Cooling container 18 Cooling container 20 Magnetic material plate 22 Magnetic material plate 24 Magnetic material column 26 Magnetic material column 28 Pole piece protrusion 30 Pole piece protrusion 32 Gradient field coil 34 Gradient field coil 36 Magnetic field uniformity control member 38 Magnetic field uniformity control member 40 Vacuum tank 42 Refrigerant tank 44 Connecting pipe 46 Connecting pipe 48 Refrigerator 50 Connecting part 50a Flexible connecting part 52 Refrigerator supporting member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihide Wadayama 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Takao Real Name 1-chome Uchikanda, Chiyoda-ku, Tokyo No. 1-14 F-term in Hitachi Medical Corporation (reference) 4C096 AA01 AB36 AB42 AB47 CA02 CA16 CA32 CA36 CA51 CA53 CA70 4M114 AA02 AA25 AA27 AA31 BB04 CC03 CC11 DA02 DA07 DA12

Claims (6)

[Claims] 1. A pair of superconducting coils arranged vertically facing each other, a pair of upper and lower donut-shaped cooling containers accommodating the respective coils, and at least electrically and thermally connecting the pair of upper and lower cooling containers. A plurality of connecting pipes, a pair of upper and lower magnetic material plates disposed above and below the pair of upper and lower cooling vessels, a magnetic material column that magnetically and mechanically couples the pair of upper and lower magnetic material plates, and An open-type superconducting magnet device having a refrigerator that cools a pair of upper and lower superconducting coils housed in a pair of upper and lower cooling containers, wherein the refrigerator has the pair of upper and lower magnetic materials at a position far from the magnetic material column. The upper magnetic material plate is disposed on the upper magnetic material plate, and is coupled to the upper cooling container in the pair of upper and lower cooling containers through a cutout formed in the upper magnetic material plate. Open superconducting magnet apparatus characterized by being. 2. The opening according to claim 1, wherein the refrigerator is disposed on the upper magnetic material plate such that a direction of a piston cylinder axis thereof is inclined with respect to a horizontal direction. Type superconducting magnet device. 3. A pair of upper and lower superconducting coils, a pair of upper and lower donut-shaped cooling containers accommodating these, and a pair of upper and lower cooling containers are connected.
Or a plurality of connecting pipes, a pair of upper and lower magnetic material plates disposed above and below the pair of upper and lower cooling vessels, and a magnetic material column for magnetically and mechanically coupling the pair of upper and lower magnetic material plates. In the open-type superconducting magnet device, the magnetic material column is disposed so as to be deflected in a depth direction from a center of a uniform magnetic field space for performing MRI imaging by inserting a subject formed by the pair of upper and lower superconducting coils. The connecting pipe is also disposed in substantially the same direction as the arrangement direction of the magnetic material columns when viewed from the center of the uniform magnetic field, and is disposed outside the outer periphery of the pair of upper and lower donut-shaped cooling vessels. An open-type superconducting magnet device, characterized in that: 4. The method according to claim 1, wherein a recess is formed in the magnetic material column, and at least a part of the connecting pipe is disposed in the recess. Open superconducting magnet device. 5. A pair of superconducting coils disposed vertically facing each other, a pair of upper and lower donut-shaped cooling containers accommodating these, and a pair of these upper and lower cooling containers are connected.
A plurality of connecting pipes, a pair of upper and lower magnetic material plates disposed above and below the pair of upper and lower cooling vessels, a magnetic material column that magnetically and mechanically couples the pair of upper and lower magnetic material plates, and An open-type superconducting magnet device having a refrigerator that cools a pair of upper and lower superconducting coils housed in a pair of upper and lower cooling vessels, respectively, wherein the refrigerator has the pair of upper and lower magnetic material plates at a position far from the magnetic material column. The upper magnetic material plate is disposed on the middle upper magnetic material plate, is coupled to the upper cooling container of the pair of upper and lower cooling containers through a cutout formed in the upper magnetic material plate, and the magnetic material column, The subject formed by the pair of upper and lower superconducting coils is disposed so as to be deviated in the depth direction from the center of the uniform magnetic field space for performing MRI imaging by inserting the subject, and the connecting pipe is When viewed from the center of the uniform magnetic field space, the magnetic material columns are disposed in substantially the same direction as the direction in which the magnetic material columns are disposed, and are disposed outside the outer periphery of the pair of upper and lower cooling vessels having the donut shape. Open superconducting magnet device. 6. An MR comprising the open superconducting magnet device according to claim 1. Description:
I device. [0001]