JP2008130947A - Superconducting magnet device and magnetic resonance imaging device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet device which allows enhancing a magnetic field strength produced in an observation region, even when a superconducting coil divided in an axial direction is employed, and furthermore allows inhibiting reduction of a space of the observation region, because of an increase in a board thickness of a supporting member, which is given allowing for occurrence of a quench, and to provide a magnetic resonance imaging device that uses the magnet device. <P>SOLUTION: The superconducting magnet device has a pair of annular superconducting main coils arranged oppositely across an observation region to produce a static magnetic field in the observation region; a pair of radiation shields which encapsulate the superconducting main coils; and a pair of vacuum vessels which accommodate the superconducting main coils and the radiation shields. Each superconducting main coil of the pair of superconducting main coils is provided with a first superconducting coil and a second superconducting coil, where the second superconducting main coil is located on the observation region side in the axial direction, with respect to the first superconducting main coil, having a magnetic material arranged between the first superconducting main coil and the second superconducting main coil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnet apparatus using a superconducting coil and a magnetic resonance imaging apparatus using the same.

A magnetic resonance imaging apparatus (hereinafter referred to as “MRI apparatus”) is an imaging apparatus that utilizes a nuclear magnetic resonance (hereinafter referred to as “NMR”) phenomenon, and measures an electromagnetic wave emitted by a hydrogen nuclear spin by the NMR phenomenon. By processing the signal, a tomographic image is obtained as a hydrogen nucleus density distribution in the body of the subject. In the MRI apparatus, a strong magnetic field (0.2 T or more) is required in the observation region, and a magnetic field distribution having high static magnetic field uniformity (about 10 ppm) needs to be formed. In general, in an MRI apparatus, it is necessary to increase the strength of a static magnetic field formed in an observation region in order to improve image resolution. The higher the electromagnetic wave intensity emitted by the hydrogen nuclear spins, the higher the resolution of the image, but the electromagnetic wave intensity emitted by the hydrogen nuclear spins is proportional to the static magnetic field intensity, so it is necessary to increase the static magnetic field intensity to increase the image resolution. There is.

  In order to increase the strength of the magnetic field formed in the observation region, it is desirable to reduce the facing distance between the superconducting main coils arranged facing each other across the observation region. However, simply reducing the facing distance of the superconducting main coil narrows the facing distance of the vacuum container that houses the superconducting main coil, giving the patient a feeling of pressure and thus making it difficult to insert the subject into the observation region. There is a possibility.

  As a solution to this problem, there is one in which the superconducting main coil is divided in the axial direction (see, for example, Patent Document 1). When the superconducting main coil is divided in the axial direction, electromagnetic forces attracting each other act on the divided superconducting main coil, and the joint acts on a support member positioned between the divided superconducting main coils. Therefore, the support member on the observation region side of the superconducting main coil can be made thinner than when the superconducting main coil is not divided. Thereby, the opposing space | interval of a superconducting main coil can be narrowed, without narrowing the opposing space | interval of a vacuum vessel.

  On the other hand, when a quench occurs in the superconducting main coil (a phenomenon in which the superconducting state collapses and the current flowing through the superconducting coil decays), an eddy current flows through the radiation shield portion on the observation region side of the superconducting main coil, and the superconducting main coil Electromagnetic force that attracts the radiation shield is generated. In other words, since the superconducting coil current flows at the beginning of the quench, the superconducting main coil located on the observation region side among the divided superconducting main coils is pulled to the superconducting main coil located on the opposite side to the observation region side. Although the force applied is strong, the force attracted to the radiation shield gradually increases, and as a result, the electromagnetic force is reversed, and the superconducting main coil (located on the observation region side among the divided superconducting main coils) attracts the radiation shield. It becomes like this. Therefore, considering the electromagnetic force support at the time of quenching, the support member on the radiation shield side has to be thick, and as a result, the facing distance between the vacuum containers is narrowed, giving the patient a feeling of pressure.

Japanese Patent No. 3624254

  Even when a superconducting coil divided in the axial direction is used, the present invention increases the static magnetic field strength formed in the observation region and narrows the observation region space by increasing the thickness of the support member considering the occurrence of quenching. It is an object of the present invention to provide a magnet device capable of suppressing the formation of a magnetic field and a magnetic resonance imaging apparatus using the magnet device.

  A pair of annular superconducting main coils arranged opposite to each other across the observation region and forming a static magnetic field in the observation region, a pair of radiation shields containing the superconducting main coil, the superconducting main coil, and the And a pair of superconducting main coils each including a first superconducting main coil and a second superconducting main coil, and the second superconducting main coil being the first superconducting coil. A superconducting magnet device, which is located on the observation region side in the axial direction with respect to the conduction main coil, and a magnetic material is disposed between the first superconducting main coil and the second superconducting main coil.

  According to the present embodiment, even when a superconducting coil divided in the axial direction is used, since the magnetic material is disposed between the divided superconducting coils, the superconducting main coil can be used even when a quench occurs. Thus, the electromagnetic force acting on the radiation shield can be reduced, and as a result, the strength of the static magnetic field formed in the observation region can be increased and the narrowing of the observation region space due to the increase in the thickness of the support member can be suppressed.

  In the MRI apparatus of the present invention, the superconducting coil is divided in the axial direction, and a magnetic material is disposed between the divided superconducting coils in consideration of the electromagnetic force acting when quenching occurs. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  A first embodiment of an electromagnet apparatus according to the present invention and an MRI apparatus using the electromagnet apparatus will be described with reference to FIGS. The MRI apparatus in the present embodiment is divided in the axial direction in order to suppress the reduction of the facing distance of the observation region due to the increase in the thickness of the support member in consideration of the electromagnetic force acting when the quench occurs while the superconducting main coil is divided in the axial direction. A magnetic material is disposed between the divided superconducting magnets.

  The MRI apparatus is an apparatus that forms a tomographic image as a hydrogen nucleus density distribution in the body of a subject by measuring an electromagnetic wave emitted by a hydrogen nucleus spin due to an NMR phenomenon and processing the signal. In the observation region, it is necessary to form a magnetic field distribution having a high magnetic field uniformity (about 10 ppm) with a strong magnetic field (0.2 T or more).

The configuration of the electromagnet device provided in the MRI apparatus will be described with reference to FIGS. FIG. 2 is a conceptual diagram of the open type MRI apparatus, and FIG. 1 is a cross-sectional view taken along the line AA ′ of FIG. 2, showing the open type MRI apparatus in the first embodiment of the present invention. The bed 2 in FIG. 1 is different from the AA ′ cross section in FIG.

  The subject 1 is transferred by the bed 2 between a pair of vacuum vessels 3 arranged so as to face each other across the observation region, and is positioned so that the region to be imaged coincides with the predetermined observation region 4. The pair of vacuum containers 3 are connected by a column 5. A static magnetic field generation source is stored inside the vacuum vessel 3 and generates a static magnetic field in the direction of the arrow 6 in the observation region 4. Inside the vacuum vessel, an annular superconducting main coil 7 that generates a static magnetic field in the direction of arrow 6 in the observation region, and an annular superconducting shield coil 8 that passes a current in the direction opposite to that of the superconducting main coil to suppress the leakage magnetic field. And are arranged. Superconducting main coil 7 is held by main coil bobbin 9, and superconducting shield coil 8 is held by shield coil bobbin 10.

  The MRI apparatus further includes a superconducting main coil 7 and a superconducting shield coil 8, a cooling container 11 that stores liquid helium for cryogenic temperature maintenance, and a cooling container 11, and relaxes the heat flux from the vacuum container 3. And a heat insulating support member 13 for supporting the cooling container 11 and the radiation shield 12 and reducing the amount of heat penetration. These structures are generally axisymmetric with respect to the axis 14 (the central axis of the MRI apparatus passing through the central portion of the observation region 4 and the central portion of the ring-shaped superconducting main coil 7), and further, with the observation region 4 interposed therebetween. Arranged symmetrically. Stainless steel can be used for the vacuum vessel 3 and the cooling vessel 11, aluminum with good thermal conductivity can be used for the radiation shield 12, and FRP can be used for the heat insulating support member 13. Since it is difficult to completely remove heat intrusion due to radiation or conduction, the cooling container 11 and the radiation shield 12 are connected to a refrigerator (not shown).

In order to provide spatial position information in imaging of a subject, a gradient magnetic field coil 15 that applies a spatial change (gradient magnetic field) of a magnetic field is disposed on the observation region 4 side of the vacuum vessel 3. Also,
In order to apply an electromagnetic wave having a resonance frequency for causing an NMR phenomenon, a high-frequency irradiation coil 16 is disposed on the observation region 4 side of the gradient magnetic field coil 15. The cross section of the subject is imaged using these configurations.

  Specifically, first, a region of interest (usually a slice plane with a thickness of 1 mm) is formed with a predetermined magnetic field intensity by superimposing a magnetic field with a gradient coil 15 on a uniform static magnetic field generated in an observation region by a static magnetic field generation source. To do. Subsequently, the region is irradiated with an electromagnetic wave having a resonance frequency using the high-frequency irradiation coil 16 to cause only the hydrogen nuclei in the region of interest to cause an NMR phenomenon, and the emitted electromagnetic wave is received to form an image. In general, in an MRI apparatus, it is necessary to increase the strength of a static magnetic field formed in an observation region in order to improve image resolution. The higher the electromagnetic wave intensity emitted by the hydrogen nuclear spins, the higher the resolution of the image, but the electromagnetic wave intensity emitted by the hydrogen nuclear spins is proportional to the static magnetic field intensity, so it is necessary to increase the static magnetic field intensity to increase the image resolution. There is.

  In order to increase the strength of the magnetic field formed in the observation region in the electromagnet apparatus having the configuration shown in FIG. 1, it is desirable that the facing distance of the superconducting main coil 7 is made closer. However, simply reducing the facing distance of the superconducting main coil narrows the facing distance of the vacuum container that houses the superconducting main coil, giving the patient a feeling of pressure and thus making it difficult to insert the subject into the observation region. There is a possibility.

  As a solution to this problem, the superconducting main coil is divided in the axial direction. That is, as shown in FIG. 1, the superconducting main coil 7 is divided in the direction of the axis 14 like the superconducting main coils 7a and 7b. The operation when the superconducting main coil 7 is divided into the superconducting main coils 7a and 7b will be described with reference to FIG. FIG. 3 is an enlarged view of a region surrounded by a dotted line in FIG. The superconducting main coils 7 arranged facing each other across the observation region 4 act as electromagnetic forces attracting each other. Therefore, if no countermeasure is taken, a support member is required on the observation region side of the superconducting main coil. When the magnetic field created in the observation region 4 is about 1T, the electromagnetic force is on the order of 1 MN, and it is necessary to support a force that is three orders of magnitude greater than its own weight. When the superconducting main coil 7 is divided in the direction of the axis 14, the superconducting main coils 7a and 7b act as electromagnetic forces attracting each other (since the divided superconducting main coils 7a and 7b flow in the same direction). It acts on the superconducting main coil support member 19. The superconducting main coil support member 19 is located between the superconducting main coils 7a and 7b and holds the superconducting main coil 7a. Since the electromagnetic force acting on the observation region side by the superconducting main coil 7 can be reduced, the support member on the observation region 4 side of the superconducting main coil 7b can be made thinner than when the superconducting main coil is not divided. Thereby, the facing distance of the superconducting main coil 7 can be narrowed without narrowing the facing distance of the vacuum vessel 3.

Furthermore, if such a coil division structure is applied to a superconducting shield coil, the height of the MRI apparatus can be reduced. That is, since the superconducting shield coil 8 is divided in the direction of the axis 14 as shown in FIG. 1, the electromagnetic coupling 22 acting on the superconducting shield coil 8 can be supported by the superconducting shield coil support member 21. The ceiling and floor side support members of the device can be made thinner, and as a result, the height of the device can be reduced.

  On the other hand, as a result of examining the situation at the time of occurrence of quenching in the superconducting coil 7 by the inventor, when quenching occurs in the superconducting main coil 7, an eddy current 23 flows in the radiation shield portion 12 on the observation region 4 side of the superconducting main coil 7. It was found that an electromagnetic force that attracts the superconducting main coil 7 to the radiation shield 12 was generated. FIG. 4 shows the time variation of the electromagnetic force acting on the superconducting main coil on the radiation shield 12 side of the superconducting main coils 7a and 7b divided in the axial direction when quenching occurs. The time when the quenching occurs at the time of the origin and the electromagnetic force becomes zero represents the time when the coil current becomes zero. The superconducting main coil 7b is subjected to a force 25 that attracts the electromagnetic shield 24 and the radiation shield drawn from the superconducting main coil 7a. In FIG. 4, the resultant force of the electromagnetic force 24 drawn from the superconducting main coil 7a and the force 25 attracted by the radiation shield is indicated by reference numeral 26. Since the superconducting coil current flows at the beginning of the quench, the superconducting main coil 7b is strongly attracted to the superconducting main coil 7a. In reverse, the superconducting main coil 7b is attracted to the radiation shield 12. Therefore, considering the electromagnetic force support at the time of quenching, the support member on the radiation shield side has to be thick, and as a result, the facing distance between the vacuum containers is narrowed, giving the patient a feeling of pressure.

  The inventor has found that by arranging a magnetic body between the superconducting main coils 7a and 7b, the problem at the time of occurrence of quenching in the divided superconducting coil 7 can be solved, which will be described in detail below. FIG. 5 shows the time variation of the electromagnetic force acting on the superconducting main coil 7b in the MRI apparatus in which the magnetic material is arranged between the superconducting main coils 7a and 7b when quenching occurs. When the quench occurs at the time of the origin and the electromagnetic force becomes zero, it indicates the time when the coil current becomes zero. When the quench occurs, the superconducting main coil 7b is acted on by the electromagnetic force 24 attracted by the superconducting main coil 7a and the force 25 attracting the radiation shield 12. Further, since the magnetic body is disposed between the superconducting main coils 7a and 7b, the electromagnetic force 28 drawn to the superconducting main coil 7a side also acts. These joints are indicated by 26. Since the superconducting coil current flows at the beginning of the quench, the force 24 drawn to the superconducting main coil 7a is larger than the force 25 drawn to the radiation shield 12 side, but gradually the relationship between the two forces is Reverse. However, by arranging a magnetic body between the superconducting main coils 7a and 7b as in the present invention, the force 28 drawn to the superconducting main coil 7a side can be generated, so that the superconducting main coil 7 is on the radiation shield 12 side. The force attracted by can be reduced.

  In this embodiment, the coil bobbin 9 is arranged in an annular shape so as to be inscribed on the inner peripheral side of the superconducting main coil 7. The magnetic member 27 is disposed between the superconducting main coils 7a and 7b and is connected to the outer peripheral side of the coil bobbin 9 in a bowl shape. The magnetic member 27 functions as a support member 19 that supports the superconducting main coil. Since the superconducting coil coupling 20 acts on the support member 19 arranged in a bowl shape on the outer peripheral side of the coil bobbin 9, a large bending stress acts on the base of the support member 19. Generally, since the rigidity of the joint portion is low, it is preferable that the joint portion between the coil bobbin 9 and the magnetic body member 27 avoid the root position of the support member 19. If there is no problem in terms of strength, the joint portion between the coil bobbin 9 and the magnetic member 27 can be the base position of the support member 19.

  As the magnetic body disposed between the superconducting main coils 7a and 7b, a ferromagnetic body represented by iron is desirable. Furthermore, a material having a high initial permeability such as a silicon steel plate is suitable. In particular, a material having a higher initial permeability than iron is desirable. As can be seen from FIG. 5, the property required for the magnetic material of the present invention is that a higher magnetic attractive force can be maintained even when the coil current is reduced. A material with a high initial permeability has exactly this property.

  According to the present embodiment, even when a superconducting coil divided in the axial direction is used, since the magnetic material is disposed between the divided superconducting coils, the superconducting main coil can be used even when a quench occurs. Electromagnetic force acting on the radiation shield can be reduced, and as a result, it is possible to increase the static magnetic field strength formed in the observation region and to suppress the narrowing of the observation region space due to the increase in the thickness of the support member Become.

  A second embodiment of the electromagnet device and the MRI apparatus using the same according to the present invention will be described below with reference to FIG. FIG. 6 shows a cross-sectional view of the MRI apparatus in the second embodiment. Similar to the MRI apparatus described in the first embodiment, the MRI apparatus in the present embodiment has the superconducting main coil divided in the axial direction, and takes into consideration the electromagnetic force that acts when quenching occurs. In order to suppress a decrease in the facing distance of the observation region due to an increase in the magnetic field, a magnetic material is disposed between the divided superconducting magnets. The difference from the first embodiment is that the coil bobbin 9 and the magnetic member 27 shown in the first embodiment are formed as a magnetic bobbin 29. Since the rest is the same as that of the first embodiment, detailed description of the apparatus configuration and the like will be omitted.

  As in the present embodiment, the coil bobbin 9 and the magnetic member 27 as a whole shown in the first embodiment are also used as the magnetic bobbin 29. As in the first embodiment, when the quench occurs, the superconducting main coil changes from the main coil to the radiation shield. The acting electromagnetic force can be reduced, and as a result, the narrowing of the observation region space due to the increase in the thickness of the support member can be suppressed.

  A third embodiment of the electromagnet device and the MRI apparatus using the same according to the present invention will be described below with reference to FIG. FIG. 7 shows a cross-sectional view of the MRI apparatus in the third embodiment. Similar to the MRI apparatus described in the first embodiment, the MRI apparatus in the present embodiment has the superconducting main coil divided in the axial direction, and takes into consideration the electromagnetic force that acts when quenching occurs. In order to suppress a decrease in the facing distance of the observation region due to an increase in the magnetic field, a magnetic material is disposed between the divided superconducting magnets. The difference from the first embodiment is that the magnetic member 27 shown in the first embodiment is extended toward the inner periphery (in the direction of the shaft 14), and the inner peripheral position of the magnetic member 27 is set to the inner periphery of the superconducting main coil 7. The magnetic material member 30 is located inside the position. The magnetic member 30 is connected to the coil bobbin 9, and the connecting portion is on the inner side of the outer peripheral surface of the coil bobbin 9 arranged in an annular shape. The magnetic body member 30 and the coil bobbin 9 can be connected while avoiding the root position of the support member 19. Since the rest is the same as that of the first embodiment, detailed description of the apparatus configuration and the like will be omitted.

  As in the present embodiment, the magnetic member 30 shown in the first embodiment is extended toward the inner periphery (in the direction of the shaft 14), and the inner peripheral position of the magnetic member 27 is located inside the inner peripheral position of the superconducting main coil 7. As in the first embodiment, the magnetic member 30 positioned on the magnetic member 30 can reduce the electromagnetic force that acts on the radiation shield from the superconducting main coil when quenching occurs. It is possible to suppress the narrowing of the observation area space due to the increase in the number of observations.

  A fourth embodiment of the electromagnet device and the MRI apparatus using the same according to the present invention will be described below with reference to FIG. FIG. 8 shows a cross-sectional view of the MRI apparatus in the fourth embodiment. Similar to the MRI apparatus described in the first embodiment, the MRI apparatus in the present embodiment has the superconducting main coil divided in the axial direction, and takes into consideration the electromagnetic force that acts when quenching occurs. In order to suppress a decrease in the facing distance of the observation region due to an increase in the magnetic field, a magnetic material is disposed between the divided superconducting magnets. The difference from the first embodiment is that the magnetic material 31 is disposed in the support member 21 (preferably the central portion in the plate thickness direction of the support member 21) disposed between the superconducting coils 7a and 7b. Since the rest is the same as that of the first embodiment, detailed description of the apparatus configuration and the like is omitted.

  Even if a magnetic material is disposed in the support member 21 disposed between the superconducting coils 7a and 7b as in the present embodiment, radiation from the superconducting main coil occurs when quenching occurs as in the first embodiment. The electromagnetic force acting on the shield can be reduced, and as a result, it is possible to suppress the narrowing of the observation region space due to the increase in the thickness of the support member.

  A fifth embodiment of the electromagnet device and the MRI apparatus using the same according to the present invention will be described below with reference to FIG. FIG. 9 shows a sectional view of the MRI apparatus in the fifth embodiment. Similar to the MRI apparatus described in the first embodiment, the MRI apparatus in the present embodiment has the superconducting main coil divided in the axial direction, and takes into consideration the electromagnetic force that acts when quenching occurs. In order to suppress a decrease in the facing distance of the observation region due to an increase in the magnetic field, a magnetic material is disposed between the divided superconducting magnets. The difference from the first embodiment is that the magnetic material 31 is disposed on the surface where the support member 21 disposed between the superconducting coils 7a and 7b and the superconducting coils 7a and 7b are in contact with each other. Since the rest is the same as that of the first embodiment, detailed description of the apparatus configuration and the like will be omitted.

  Even if the magnetic material 31 is disposed on the surface where the support member 21 disposed between the superconducting coils 7a and 7b and the superconducting coils 7a and 7b are in contact with each other as in the present embodiment, the quenching is performed as in the first embodiment. When this occurs, the electromagnetic force acting on the radiation shield from the superconducting main coil can be reduced. As a result, it is possible to suppress the narrowing of the observation region space due to the increase in the thickness of the support member.

  A sixth embodiment of the electromagnet apparatus according to the present invention and an MRI apparatus using the same will be described below with reference to FIG. FIG. 10 shows a cross-sectional view of the MRI apparatus in the sixth embodiment. Similar to the MRI apparatus described in the first embodiment, the MRI apparatus in the present embodiment has the superconducting main coil divided in the axial direction, and takes into consideration the electromagnetic force that acts when quenching occurs. In order to suppress a decrease in the facing distance of the observation region due to an increase in the magnetic field, a magnetic material is disposed between the divided superconducting magnets. The difference from the first embodiment is that the magnetic member 33 is disposed in the superconducting main coil coil 7a located farther from the radiation shield 12 among the divided superconducting main coils 7a and 7b. . The magnetic member 31 may be arranged in any form such as a block shape, a wire shape, or a powder shape. Since the rest is the same as that of the first embodiment, detailed description of the apparatus configuration and the like will be omitted.

  Even if the magnetic body member 33 is arranged in the superconducting main coil coil 7a located away from the radiation shield 12 among the divided superconducting main coils 7a and 7b as in the present embodiment, Similarly, it is possible to reduce the electromagnetic force acting on the radiation shield from the superconducting main coil when quenching occurs, and as a result, it is possible to suppress the narrowing of the observation region space due to the increase in the thickness of the support member It becomes.

  In each of the above embodiments, the embodiment in which the superconducting coil is divided into two parts has been described. However, the number of divisions of the coil may be two or more, and the number of divisions of the superconducting coil is not limited to two.

  In each of the above embodiments, the superconducting main coil 7 has been described as an example. However, even if the superconducting shield coil 8 is divided, the electromagnetic force drawn to the radiation shield 12 side can be reduced by the same action. Thereby, since the support member by the side of the radiation shield of a superconducting coil can be made thin, apparatus height and weight can be reduced.

  In each of the above embodiments, the central axis 14 is set in the vertical direction. However, since the force targeted by the present invention is not a heavy force but an electromagnetic force, the center axis 14 is not limited to the horizontal direction. The same effect can be obtained by applying the structure of the invention.

1 is a cross-sectional view of an MRI apparatus in a first embodiment of the present invention. An overview of an open MRI apparatus. The expanded sectional view of the MRI apparatus of FIG. The figure which shows the time change of the axial direction electromagnetic force which acts on a superconducting main coil. The figure which shows the time change of the axial direction electromagnetic force which acts on a superconducting main coil. Sectional drawing of the MRI apparatus in the 2nd Example of this invention. Sectional drawing of the MRI apparatus in the 3rd Example of this invention. Sectional drawing of the MRI apparatus in 4th Example of this invention. Sectional drawing of the MRI apparatus in 5th Example of this invention. Sectional drawing of the MRI apparatus in 6th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Bed 3 Vacuum container 4 Observation area 5 Support column 7 Superconducting main coil 8 Superconducting shield coil 9 Superconducting main coil bobbin 10 Superconducting shield coil bobbin 11 Cooling container 12 Radiation shield 13 Heat insulation support part 15 Gradient magnetic field coil 16 High frequency irradiation apparatus 17 Enlargement part 18 Coil current direction 19, 21 Superconducting coil support member 20, 22 Direction of electromagnetic force acting in the axial direction on the superconducting coil support member 23 Direction of eddy current on the radiation shield 24 Axial direction of superconducting main coil 7b by superconducting main coil 7a Electromagnetic force 25 Axial electromagnetic force 26 of superconducting main coil 7b due to eddy current on radiation shield A resultant force 27, 29, 30, 31, 32, 33 of the axial electromagnetic force of superconducting main fork 7b Magnetic member 28 of the present invention Axial electromagnetic force of superconducting main coil 7b by a ferromagnetic member

Claims (13)

A pair of annular superconducting main coils arranged opposite to each other across the observation region and forming a static magnetic field in the observation region, a pair of radiation shields containing the superconducting main coil, the superconducting main coil, and the A pair of vacuum containers for storing the radiation shield,
Each of the pair of superconducting main coils includes a first superconducting main coil and a second superconducting main coil,
The second superconducting main coil is positioned on the observation region side in the axial direction with respect to the first superconducting main coil,
A superconducting magnet device, wherein a magnetic material is disposed between the first superconducting main coil and the second superconducting main coil.   The superconducting magnet device according to claim 1, wherein a holding member for holding the first superconducting main coil is disposed between the first superconducting main coil and the second superconducting main coil, A superconducting magnet device, wherein the holding member is the magnetic material.   The superconducting magnet device according to claim 1, wherein a holding member for holding the first superconducting main coil is disposed between the first superconducting main coil and the second superconducting main coil, A superconducting magnet device, wherein the magnetic material is disposed on an outer periphery of a holding member.   The superconducting magnet device according to claim 1, wherein a holding member for holding the first superconducting main coil is disposed between the first superconducting main coil and the second superconducting main coil, A superconducting magnet apparatus, wherein the magnetic material is disposed inside a holding member. A pair of annular superconducting main coils arranged opposite to each other across the observation region and forming a static magnetic field in the observation region, a pair of radiation shields containing the superconducting main coil, the superconducting main coil, and the A pair of vacuum containers for storing the radiation shield,
Each of the pair of superconducting main coils includes a first superconducting main coil and a second superconducting main coil,
The second superconducting main coil is positioned on the observation region side in the axial direction with respect to the first superconducting main coil,
A superconducting magnet apparatus, wherein a magnetic material is disposed inside the first superconducting main coil. A pair of annular superconducting main coils arranged opposite to each other across the observation region and forming a static magnetic field in the observation region; and an annular superconducting shield coil for suppressing a leakage magnetic field generated by the superconducting main coil; A pair of radiation shields that contain the superconducting main coil and the superconducting shield coil, and a pair of vacuum containers that house the superconducting main coil, the superconducting shield coil, and the radiation shield,
Each of the pair of superconducting shield coils includes a first superconducting shield coil and a second superconducting shield coil,
The second superconducting shield coil is positioned on the observation region side in the axial direction with respect to the first superconducting shield coil,
A superconducting magnet device, wherein a magnetic material is disposed between the first superconducting shield coil and the second superconducting shield coil.   The superconducting magnet device according to claim 6, wherein a holding member for holding the first superconducting shield coil is disposed between the first superconducting shield coil and the second superconducting shield coil, A superconducting magnet device, wherein the holding member is the magnetic material.   The superconducting magnet device according to claim 6, wherein a holding member for holding the first superconducting shield coil is disposed between the first superconducting shield coil and the second superconducting shield coil, A superconducting magnet device, wherein the magnetic material is disposed on an outer periphery of a holding member.   The superconducting magnet device according to claim 6, wherein a holding member for holding the first superconducting shield coil is disposed between the first superconducting shield coil and the second superconducting shield coil, A superconducting magnet apparatus, wherein the magnetic material is disposed inside a holding member. A pair of annular superconducting main coils arranged opposite to each other across the observation region and forming a static magnetic field in the observation region; and an annular superconducting shield coil for suppressing a leakage magnetic field generated by the superconducting main coil; A pair of radiation shields that contain the superconducting main coil and the superconducting shield coil, and a pair of vacuum containers that house the superconducting main coil, the superconducting shield coil, and the radiation shield,
Each of the pair of superconducting shield coils includes a first superconducting shield coil and a second superconducting shield coil,
The second superconducting shield coil is positioned on the observation region side in the axial direction with respect to the first superconducting shield coil,
A superconducting magnet apparatus, wherein a magnetic material is disposed inside the first superconducting main coil.   The superconducting magnet device according to any one of claims 1 to 10, wherein the magnetic material is iron.   The superconducting magnet device according to any one of claims 1 to 10, wherein the magnetic material has an initial permeability higher than that of iron.   A magnetic resonance imaging apparatus comprising the superconducting magnet apparatus according to claim 1.

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