JP4023703B2 - Magnetic resonance imaging system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus), and has a particularly wide opening to give a subject a sense of openness and facilitate access to the subject for an operator. The present invention relates to a magnetic resonance imaging apparatus having a superconducting magnet apparatus.
[0002]
[Prior art]
Currently, permanent magnets and superconducting magnets are used in apparatuses using a uniform high magnetic field such as MRI apparatuses. In recent years, MRI apparatuses and the like are required to have high image resolution, and superconducting magnets that can generate a high magnetic field tend to be frequently used.
[0003]
In addition, a cylindrical horizontal magnetic field type superconducting magnet device was originally used in the MRI apparatus, but in this method, a uniform magnetic field region is generated in the cylinder, so that the subject is left in the cylinder for a long time during the examination. As a result, this gives a sense of blockage to the subject, which is a problem. For this reason, in recent MRI apparatuses, those using open-type magnets are becoming mainstream except those using high-magnetic superconducting magnet apparatuses.
[0004]
An open-type magnet has a pair of magnetic field generation sources facing each other across a uniform magnetic field region, and since the periphery of the uniform magnetic field region is open, the openness for the subject is very good. is there. As an MRI apparatus using an open-type magnet, a vertical magnetic field system using a permanent magnet has been the mainstream, but recently, an apparatus using a normal conducting magnet apparatus or a superconducting magnet apparatus has been commercialized. Yes.
[0005]
As the open superconducting magnet device, there are a vertical magnetic field type and a horizontal magnetic field type. Many of the magnetic field generation sources of these open superconducting magnet devices can adopt an active shield system in order to suppress the leakage magnetic field. In this active shield type magnet, a pair of shield coils are arranged outside the center of the uniform magnetic field space of the pair of main coils that generate a uniform magnetic field, and a current in a direction opposite to that of the main coil is disposed in the shield coil. The leakage magnetic field around the magnet is suppressed by flowing the.
[0006]
As a first example of an open type active shield type superconducting magnet device, there is one disclosed in Japanese Patent Laid-Open No. 9-153408 (hereinafter referred to as well-known example 1). In the magnet of publicly known example 1, a main coil and a cancellation coil (corresponding to a shield coil) housed in a pair of cooling containers are arranged facing each other across a uniform magnetic field region. The outer diameter of the main coil and the outer diameter of the cancellation coil are almost the same size, and the outer diameter of the cooling container that houses them is uniform. In the magnet having such a structure, there is a problem that the entire apparatus becomes large in order to reduce the leakage magnetic field.
[0007]
As a second example of the open-type active shield superconducting magnet device, there is one disclosed in Japanese Patent Laid-Open No. 9-190913 (hereinafter referred to as well-known example 2). In the magnet of the known example 2, a passive shield type magnetic shield made of a disk-shaped ferromagnetic material, a cylindrical ferromagnetic material, a columnar ferromagnetic material, or the like is arranged around the magnet of the known example 1, and the main coil is used. The leakage magnetic field is suppressed by forming a return path of the generated magnetic flux. In the known example 2, the cancellation coil is usually omitted. However, when the cancellation coil is used, the outer diameter of the cancellation coil is equal to or less than the outer diameter of the main coil, and the main coil and the cancellation coil are accommodated. The outer diameter of the cooling container is uniform. In the magnet having such a structure, the magnetic shield is performed by combining the active shield method and the passive shield method, so that the leakage magnetic field can be greatly suppressed, but since the passive shield method is adopted, the magnet The problem of increased weight arises.
[0008]
As a third example of the open-type active shield superconducting magnet apparatus, there is one disclosed in US Pat. No. 5,448,214 (hereinafter referred to as “known example 3”). The magnet of the known example 3 is of the horizontal magnetic field type, and the outer diameter of the shield coil is larger than the outer diameter of the main coil, but both coils are housed in separate cooling containers. In the magnet having such a structure, there are problems that the number of cooling containers increases and the structure becomes complicated, and the total length becomes long, so that it is difficult to adopt the vertical magnetic field method.
[0009]
[Problems to be solved by the invention]
As described in the above prior art, in the conventional open superconducting magnet device, it is difficult to suppress the leakage magnetic field with a simple structure. That is, when the shield coil is used in the active shield system, the outer diameter of the shield coil must be increased in order to increase the effect of suppressing the leakage magnetic field. As a result, in the case of the known example 1, the cooling container is used. The outer diameter of the patient becomes large, and the feeling of opening for the subject is greatly impaired, making it difficult for the operator to access the subject. Further, in the case of the known example 3, since the number of cooling containers increases, there is a problem that the structure becomes complicated and the cost increases. Further, when a magnetic shield made of iron or the like is used in the passive shield method, there is a problem that the weight of the whole magnet becomes very heavy.
[0010]
For this reason, the present invention provides a super magnetic resonance imaging apparatus that is simple in structure, has little leakage magnetic field spread, gives the subject a great sense of openness, and allows the operator to easily access the subject. The purpose is to do.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, at least one pair of magnetic field generation sources arranged facing each other across a uniform magnetic field region, a pair of cooling containers storing the magnetic field generation source, and the pair of cooling containers connected to each other. In the magnetic resonance imaging apparatus comprising the two connecting tubes, each of the magnetic field generation sources is coaxially arranged in the magnetic field direction of the uniform magnetic field, and has a main coil and a shield coil made of a material having superconducting characteristics. Thus, the outer diameters of the portions that house the shield coils of the pair of cooling containers are different from each other .
Alternatively, in at least one of the cooling containers, the outer diameter of the portion that houses the shield coil and the outer diameter of the portion that houses the main coil are different .
[0012]
In this configuration, in an open superconducting magnet apparatus in which a pair of magnetic field generation sources are arranged opposite to each other centering on a uniform magnetic field region, the main coil on the side where the outer diameter of the cooling container is close to the uniform magnetic field region is disposed. It is small and large at the part where the shield coil on the far side is arranged. As a result, since the outer diameter of the shield coil can be made larger than the outer diameter of the main coil, the effect of reducing the leakage magnetic field by the shield coil can be improved. In addition, since the outer diameter of the peripheral portion of the uniform magnetic field region of the cooling container is small, the openness of the subject and the operator's accessibility to the subject are good and do not deteriorate compared to the conventional one.
[0013]
Also, this configuration can be applied as an open vertical magnetic field superconducting magnet device with the uniform magnetic field direction as the vertical direction, or as an open horizontal magnetic field method superconducting magnet device with the uniform magnetic field direction as the horizontal direction. Is possible. In either case, the effect of reducing the leakage magnetic field, the openness of the subject, and the operator's accessibility are ensured.
[0014]
Furthermore, in the superconducting magnet device of the present invention, the outer diameter of the portion accommodating the shield coil in both cooling containers is larger than the outer diameter of the portion accommodating the main coil. In this configuration, since the cooling vessel and the magnetic field generation source (main coil and shield coil) can be symmetrically shaped around the uniform magnetic field region, high magnetic field uniformity can be obtained, and electromagnetic field can be used as the magnetic field generation source. Benefits include easy balance of power.
[0015]
Furthermore, in the superconducting magnet device of the present invention, only in one cooling container, the outer diameter of the portion accommodating the shield coil is larger than the outer diameter of the portion accommodating the main coil. Regarding the outer periphery of the cooling container, changing the outer diameter between the part for storing the main coil and the part for storing the shield coil complicates the structure of the cooling container, which causes an increase in cost. Therefore, in this configuration, it is advantageous in cost because only one side needs to be a cooling container having a complicated structure, and the restriction of the leakage magnetic field on one side of the uniform magnetic field region is relaxed compared to the other side, etc. The configuration is suitable for.
[0016]
Further, in the superconducting magnet device of the present invention, the magnetic field direction of the uniform magnetic field is the vertical direction, and the surgeon has an outer diameter of a portion containing the shield coil of the lower cooling container smaller than an outer diameter of the portion containing the main coil. The outer diameter of the upper cooling container is made uniform by increasing the height of the outer cooling container. In this configuration, since the outer diameter of the upper cooling container is uniform, the upper side is not covered and the feeling of pressure on the subject is reduced. In addition, by setting the protrusion of the outer periphery of the portion of the lower cooling container that houses the shield coil to an extent that the surgeon can stand, the substantial outer diameter of the lower cooling container is determined by the size of the small diameter portion that houses the main coil. Therefore, the leakage magnetic field to the lower side of the apparatus can be reduced without changing the operator's access to the subject.
[0017]
Further, in the superconducting magnet device of the present invention, the magnetic field direction of the uniform magnetic field is the vertical direction, and the outer diameter of the portion containing the shield coil of the upper cooling vessel is made larger than the outer diameter of the portion containing the main coil, The outer diameter of the cooling container is made uniform. In this configuration, since the outer diameter of the shield coil of the upper magnetic field generation source can be increased, the leakage magnetic field to the upper side of the apparatus can be suppressed, and the influence of the magnetic field on the floor can be eliminated.
[0018]
In the superconducting magnet apparatus of the present invention, the pair of cooling containers are connected by a plurality of connecting pipes, and the position of the outermost part from the center of the uniform magnetic field region of the connecting pipes is the part in which the shield coil of the cooling container is stored This is almost the same as the position of the outer diameter. In this configuration, since the outer diameter of the magnet including the plurality of connecting pipes is substantially the same as the maximum diameter of the cooling container, there is no protruding portion at the outer diameter of the magnet, and the structure of the cooling container is simplified. Moreover, since the protrusions are reduced in terms of design, the feeling of opening of the entire apparatus is enhanced.
[0019]
The superconducting magnet device according to the present invention further comprises a disk-shaped shield plate made of a pair of ferromagnetic materials around a pair of cooling vessels and a columnar yoke made of a plurality of ferromagnetic materials connecting both shield plates. Arranged magnetic circuit. In this configuration, a passive shield type magnetic shield is formed around the magnetic field generation source housed in the cooling container as a return path of the magnetic flux generated in the uniform magnetic field region by the main coil. It is greatly reduced.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows an external view of a first embodiment of the superconducting magnet apparatus of the present invention. In FIG. 1, the vertical direction is the Z axis, the horizontal direction is the X axis, and the direction perpendicular to the paper surface is the Y axis. FIG. 2 shows a cross-sectional view of this embodiment. In FIG. 2, the left half is the XZ cross section, and the right half is the YZ cross section.
[0021]
In FIG. 1, the superconducting magnet apparatus according to the present embodiment has an upper cooling vessel 2 and a lower cooling vessel 3 facing each other with a uniform magnetic field region 1 interposed therebetween. The upper cooling vessel 2 and the lower cooling vessel are connected by connecting pipes 8 disposed on the left and right sides of the uniform magnetic field region 1. The upper cooling container 2 is supported by the connecting pipe 8.
[0022]
As shown in FIG. 2, an upper magnetic field generation source 9 is included in the upper cooling container 2, and a lower magnetic field generation source 10 is included in the lower cooling container 3, and the upper magnetic field generation source 9 includes the upper main coil 11 and the upper main coil 11. The lower magnetic field generation source 10 includes a lower main coil 13 and a lower shield coil 14. For the main coils 11 and 13 and the shield coils 12 and 14, a superconducting material, for example, a wire such as NbTi is used. The upper cooling container 2 and the lower cooling container 3 include a refrigerant container 16 filled with a superconducting refrigerant 15, a vacuum container 17 containing the refrigerant container 16, and a heat shield (not shown) covering the outside of the refrigerant container 16. Z)). The upper and lower refrigerant containers 16 are thermally and electrically connected by a connecting pipe 8. The connecting pipe 8 also serves to hold the upper and lower cooling containers 2 and 3 at a constant interval.
[0023]
The main coils 11 and 13 and the shield coils 12 and 14 are immersed in the superconducting refrigerant 15, cooled to a temperature exhibiting superconducting characteristics, and maintained. When an alloy superconductor such as NbTi is used as the coil wire, liquid helium is used as the superconducting refrigerant 15. Usually, a refrigerator (not shown) is connected to the cooling containers 2 and 3. However, the high performance of the refrigerator enables a configuration that does not use a cooling liquid such as liquid helium. The refrigerant container 16 for storing the superconducting refrigerant 15 becomes unnecessary, and the configuration of the cooling containers 2 and 3 is simplified.
[0024]
A uniform magnetic field (magnetic flux density B ₀ ) in the vertical direction (Z-axis direction) is generated in the uniform magnetic field region 1 by the upper main coil 11 of the upper magnetic field generation source 2 and the lower main coil 13 of the lower magnetic field generation source 3. . In order to shield the leakage magnetic field from the upper main coil 11 and the lower main coil 13, the upper shield coil 12 and the lower shield coil 14 are disposed outside the main coils 11 and 13, and are opposite to the corresponding main coils. Current is energized.
[0025]
In the illustrated example, each of the main coils 11 and 13 and the shield coils 12 and 14 is shown as one coil, but in order to obtain a desired magnetic field strength and magnetic field uniformity in the uniform magnetic field region 1, In order to obtain a desired spread of the leakage magnetic field, it is also possible to arrange a plurality of coils in combination in the vertical direction (Z-axis direction) on the same axis. In the actual structure of the magnetic field generation source, in order to obtain a static magnetic field with high magnetic field uniformity, it is advantageous to use a plurality of coils having different or all of the coil diameter, the number of turns, and the arrangement position.
[0026]
In order to improve the effect of reducing the leakage magnetic field by the shield coils 12, 14, the shield coils 12, 14 are made larger in diameter than the corresponding main coils 11, 13 to cover the main coils 12, 14. In addition, the space between the main coils 11 and 13 and the shield coils 12 and 14 is increased to improve the efficiency as a shield coil.
[0027]
Further, in the present embodiment, the outer diameter of the portion for storing the main coils 11 and 13 of the upper and lower cooling containers 2 and 3 and the shield coil 12 are matched to the difference in diameter between the main coils 11 and 13 and the shield coils 12 and 14. , 14 is provided with a difference from the outer diameter of the portion in which it is stored. That is, the portion of the upper cooling vessel 2 that houses the upper main coil 11 is the upper small-diameter portion 4 and the portion that houses the upper shield coil 12 is the upper large-diameter portion 5, and the lower main coil 13 of the lower cooling vessel 3 is accommodated. The portion that accommodates the lower small-diameter portion 6 and the portion that houses the lower shield coil 14 are the lower large-diameter portion 7.
[0028]
With this configuration, the diameter of the portion of the cooling containers 2 and 3 that is far from the uniform magnetic field region 1 into which the subject is inserted (the portion that houses the shield coils 12 and 14) is large, but the close portion (the main coil). Since the diameters of the portions 11 and 13 are small, the leakage magnetic field can be reduced without impairing the openness around the subject.
[0029]
In FIG. 1, the connecting pipe 8 is disposed on both sides of the uniform magnetic field region 1, but is usually a circular tube. Although this shape is square, there is no functional problem, but a circular tube is preferable in terms of workability. The cooling containers 2 and 3 are connected to the connecting pipe so that the outer shape of the connecting pipe 8 substantially matches the maximum diameter of the cooling containers 2 and 3. By configuring in this way, the protruding portion at the outer diameter portion of the magnet is eliminated, so that the structure of the cooling container is simplified, the number of protrusions is reduced in terms of design, and the open feeling of the entire apparatus is enhanced.
[0030]
FIG. 3 shows an external view of a second embodiment of the superconducting magnet apparatus of the present invention. In the present embodiment, the diameter of the upper shield coil 12 included in the upper cooling container 2 is made substantially the same as or smaller than the diameter of the upper main coil 11, and the outer diameter of the upper cooling container 2 is reduced over the entire length (upper small diameter). The lower cooling container 3 is formed by increasing the diameter of the portion containing the lower shield coil 14 as in the first embodiment.
[0031]
In the present embodiment, the outer diameter of the upper cooling container 2 becomes a small diameter over the entire length, and there is no portion that covers the upper side of the apparatus, so that there is no object that gives a heavy pressure to the subject, and the openness of the subject is improved. Further, the diameter of the lower shield coil 14 (the lower large diameter portion 7) containing the lower shield coil 14 is sufficiently increased, and the diameter of the lower shield coil 14 is increased, thereby shielding the leakage magnetic field. The effect can be improved. Furthermore, by making the diameter of the lower large-diameter portion 7 large enough to allow an operator to stand on the subject and operate on the subject, accessibility to the central portion of the apparatus (homogeneous magnetic field region 1) is also improved. To do.
[0032]
FIG. 4 shows an external view of a third embodiment of the superconducting magnet apparatus of the present invention. In the present embodiment, the diameter of the portion of the upper cooling container 2 in which the upper shield coil 12 is accommodated is increased, and the outer diameter of the lower cooling container 3 is reduced over the entire length (lower small diameter portion 21). In the present embodiment, by increasing the outer diameter of the upper large-diameter portion 5, only the outer diameter of the upper shield coil 12 can be increased, so that the leakage magnetic field upward of the apparatus can be sufficiently reduced. By reducing the influence of the leakage magnetic field on the floor, installation conditions can be relaxed. In addition, since the outer diameters of the portions (upper small diameter portion 4, lower small diameter portion 21) close to the uniform magnetic field region 1 of the upper and lower cooling containers 2 and 3 are configured to be small, there is no decrease in the degree of openness of the subject. The operator's access to the subject is also good.
[0033]
FIG. 5 shows a front view and a central sectional view of a fourth embodiment of the superconducting magnet apparatus of the present embodiment. FIG. 6 shows the same diagram in the case of the first embodiment for comparison. In this embodiment, the structure and arrangement of the upper and lower cooling containers 2 and 3 are the same as those in the first embodiment, but the arrangement of the connecting pipe 8 is different. As shown in the central cross-sectional view of this embodiment in FIG. 5B, in this embodiment, the left and right connecting pipes 8 are connected to the center line 22 in the left-right direction passing through the center of the uniform magnetic field region 1. It is arranged behind the first embodiment. As a result, the front and left and right spaces are opened with reference to the uniform magnetic field region 1, and the accessibility to the subject from the left and right direction (lateral direction) is improved as compared with the first embodiment.
[0034]
FIG. 7 shows an external view of a fifth embodiment of the superconducting magnet apparatus of the present invention. The present embodiment is a horizontal magnetic field type superconducting magnet device, in which a left cooling container 30 and a right cooling container 31 are arranged opposite to each other on the left and right sides of the uniform magnetic field region 1. Each cooling vessel 30, 31 contains a main coil that generates a horizontal uniform magnetic field in the uniform magnetic field region 1 and a shield coil for reducing the leakage magnetic field. Since the main coil included in the left cooling container 30 and the shield coil are formed to have substantially the same diameter, the outer periphery of the left cooling container 30 is composed of a small-diameter left small diameter portion 32, and the main coil included in the right cooling container 31. Since the diameter of the shield coil is larger than the diameter of the main coil, the outer periphery of the right cooling vessel 31 is composed of a small right small diameter portion 33 and a large right large diameter portion 34. Each cooling container 30 and 31 is provided with holes 35 and 36 for inserting a subject.
[0035]
By configuring the superconducting magnet apparatus as described above, the openness for the subject is slightly better on the left side of the uniform magnetic field region 1, but the outer circumferences of the cooling containers 30 and 31 around the uniform magnetic field region 1 are small in diameter. Therefore, the openness of the subject and the accessibility of the operator to the subject are good. In addition, regarding the shielding effect of the leakage magnetic field, the right part in which the large-diameter shield coil is included is better. In the case of the present embodiment, the large diameter portion is provided only in the right cooling container 31, but the present invention is not limited to this, and the large diameter portion may be provided only in the left cooling container 30, and provided in both cooling containers. May be.
[0036]
FIG. 8 shows an external view of a sixth embodiment of the superconducting magnet apparatus of the present invention. In this embodiment, the magnetic field generation source has the same structure as that of the first embodiment, but a magnetic shield made of a ferromagnetic material is provided around it. In FIG. 8, the upper cooling vessel 2 and the lower cooling vessel 3 are arranged facing each other in the vertical direction across the uniform magnetic field region 1. The upper cooling container 2 has an upper small-diameter part 4 that houses the upper main coil and an upper large-diameter part 5 that houses the upper shield coil, and the lower cooling container 3 has a lower small-diameter part 6 that houses the lower main coil, It has a lower large-diameter portion 7 that houses the lower shield coil. A disc-shaped upper shield plate 40 and a lower shield plate 41 made of a ferromagnetic material such as iron are disposed on the upper side of the upper cooling vessel 2 and the lower side of the lower cooling vessel 3. The space is connected and supported by a cylindrical yoke 42 made of two ferromagnetic materials such as iron.
[0037]
Also in the present embodiment, a uniform magnetic field is generated in the uniform magnetic field region 1 by the upper main coil and the lower main coil, and the leakage magnetic field to the outside is reduced by the upper shield coil and the lower shield coil. In the case of the present embodiment, the upper and lower shield plates 40 and 41 and the yoke 42 are disposed outside the upper and lower cooling containers 2 and 3, so that the upper shield plate 40, the yoke 42 and the lower shield are used as return paths for the magnetic flux in the vertical direction. A magnetic circuit composed of the plate 41 is formed to further reduce the leakage magnetic field.
[0038]
In this embodiment, in order to suppress the leakage magnetic field, the active shield system combining a main coil and a shield coil and the passive shield system using a magnetic circuit made of a ferromagnetic material are used together. However, the present invention is not limited only to the first embodiment described above, and combinations are possible even when the second to fifth embodiments are applied, and similar effects can be obtained. The combined use of such passive shield method is effective when it is desired to significantly reduce the leakage magnetic field or when it is difficult to reduce the leakage magnetic field only with the active shield method, and high magnetic field strength, openness, and low leakage magnetic field are required. It can be applied to various uses.
[0039]
【The invention's effect】
As described above, according to the present invention, the outer diameter of the cooling container of the superconducting magnet device is provided with an outer diameter difference depending on the distance from the uniform magnetic field region, the portion in which the main coil is accommodated has a small diameter, and the shield coil is accommodated. The part to be formed is configured to have a large diameter. As a result, the leakage magnetic field is greatly reduced by the application of the large-diameter shield coil, and the diameter of the cooling container in the portion close to the uniform magnetic field region is small, so that it is open to the subject and accessible to the operator. High magnetic resonance imaging apparatus can be provided. The superconducting magnet apparatus characterized by the present invention is mainly applied to an MRI apparatus by taking advantage of the above-mentioned characteristics, but can be applied to applications requiring a uniform high magnetic field such as a single crystal pulling apparatus in addition to the MRI apparatus. .
[Brief description of the drawings]
FIG. 1 is an external view of a first embodiment of a superconducting magnet apparatus according to the present invention.
FIG. 2 is a cross-sectional view of a first embodiment of the superconducting magnet apparatus of the present invention.
FIG. 3 is an external view of a second embodiment of the superconducting magnet apparatus according to the present invention.
FIG. 4 is an external view of a third embodiment of the superconducting magnet device of the present invention.
FIG. 5 is a front view and a central sectional view of a fourth embodiment of the superconducting magnet apparatus of the present invention.
FIG. 6 is a front view and a central sectional view of a first embodiment of the superconducting magnet apparatus of the present invention.
FIG. 7 is an external view of a fifth embodiment of the superconducting magnet device of the present invention.
FIG. 8 is an external view of a sixth embodiment of the superconducting magnet device of the present invention.
[Explanation of symbols]
1 Uniform magnetic field area (imaging area)
2 Upper cooling vessel 3 Lower cooling vessel 4, 20 Upper small diameter portion 5 Upper large diameter portion 6, 21 Lower small diameter portion 7 Lower large diameter portion 8 Connection tube 9 Upper magnetic field generation source 10 Lower magnetic field generation source 11 Upper main Coil 12 Upper shield coil 13 Lower main coil 14 Lower shield coil 15 Superconducting refrigerant (liquid helium)
16 Refrigerant container (liquid helium container)
17 Vacuum vessel 22 Center line 30 Right cooling vessel 31 Left cooling vessel 32 Right small diameter portion 33 Right large diameter portion 34 Left small diameter portions 35, 36 Hole 40 Upper shield plate 41 Lower shield plate 42 Yoke

Claims (6)

A pair of magnetic field generation sources arranged facing each other across the uniform magnetic field region, a pair of cooling containers that store the magnetic field generation sources, and at least one connecting pipe that connects the pair of cooling containers to each other. the magnetic resonance imaging apparatus, each of said magnetic field generating source is arranged coaxially to the magnetic field direction of the uniform magnetic field, made and a primary coil and a shield coil made of a material having a superconducting property, the pair A magnetic resonance imaging apparatus characterized in that the outer diameters of the portions of the cooling container for housing the shield coils are different from each other . 2. The magnetic resonance imaging apparatus according to claim 1 , wherein in at least one of the cooling containers, an outer diameter of a portion accommodating the shield coil and an outer diameter of a portion accommodating the main coil are different from each other. Resonance imaging device. 3. The magnetic resonance imaging apparatus according to claim 1 , wherein in at least one of the cooling containers, an outer diameter of a portion accommodating the shield coil is larger than an outer diameter of a portion accommodating the main coil. Magnetic resonance imaging apparatus. 4. The magnetic resonance imaging apparatus according to claim 1, wherein one of the pair of cooling containers includes an outer diameter of a portion accommodating the shield coil and an outer diameter of a portion accommodating the main coil. Are substantially the same, a magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to any one of claims 1 to 4, the magnetic resonance imaging apparatus characterized by being arranged so that the outer shape of the connecting tube is a maximum diameter that substantially matches the cooling vessel. 6. The magnetic resonance imaging apparatus according to claim 1, wherein a ferromagnetic member is disposed on the opposite side of the uniform magnetic field region for each cooling container.

Images