Superconducting magnets and magnetic resonance imaging apparatus

Abstract

To enable static magnetic field distribution of a superconducting magnet to be formed with a high degree of freedom and enable a permanent current mode of a superconducting magnet to be continued over a long period of time.SOLUTION: A superconducting magnet includes: a first coil segment composed of a superconductive wire, through which a current in a forward direction flows; a second coil segment composed of the superconductive wire, through which a current in a direction reverse to the forward direction flows; and an intermediate wiring part disposed between the first coil segment and the second coil segment, which changes the directions of the current so that the current in the forward direction flows through the first coil segment and the current in the reverse direction flows through the second coil segment, and connects the first coil segment and the second coil segment to each other without disconnecting them.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to superconducting magnets and magnetic resonance imaging devices.

Background Art

[0002] A magnetic resonance imaging device excites the nuclear spins of a subject placed in a static magnetic field with a high-frequency (RF: Radio Frequency) signal at the Larmor frequency, and reconstructs the magnetic resonance signal (MR (Magnetic Resonance) signal) generated from the subject due to the excitation to generate an image.

[0003] A magnetic resonance imaging device includes a static magnetic field magnet for forming a static magnetic field. In particular, in a magnetic resonance imaging device for inspection and diagnosis installed in a medical institution such as a hospital, a very large static magnetic field is required, so a superconducting magnet is used.

[0004] In a static magnetic field magnet using a superconducting magnet, for example, a superconducting coil is cooled to an extremely low temperature by liquid helium or the like. In a conventional static magnetic field magnet, a plurality of superconducting coils having different diameters and numbers of turns are arranged at different positions respectively to obtain a desired static magnetic field distribution.

[0005] Also, in a conventional static magnetic field magnet, each of a plurality of superconducting coils is connected using various connection means such as soldering connection and crimp connection. The connection between superconducting coils using these connection means is hereinafter referred to as "superconducting connection".

[0006] Although the position of the superconducting connection is placed in an extremely low temperature environment like the superconducting coil, due to the resistance of the solder layer intervening between the superconducting filaments at the connection point, the resistance due to the oxide layer of the superconducting filaments, etc., the superconducting connection has a minute but finite resistance value.

[0007] Generally, the time constant τ for magnetic field decay after transitioning to the persistent current mode is given by τ = L / R, where L is the inductance of the superconducting coil and R is the total resistance of the superconducting coil. In the persistent current mode, the resistance of each individual superconducting coil becomes virtually zero, so the total resistance R of the superconducting coil is dominated by the resistance due to the superconducting connection as described above.

[0008] Therefore, in order to lengthen the duration of the persistent current mode (i.e., to increase the time constant τ of magnetic field decay), the resistance value due to the superconducting connection should be minimized as much as possible.

[0009] In particular, with superconducting magnets where the static magnetic field strength is relatively small, the inductance L of the superconducting coil is also small. Accordingly, by minimizing the resistance value due to the superconducting connection, the duration of the persistent current mode can be extended. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2012-227178 [Overview of the project] [Problems that the invention aims to solve]

[0011] One of the problems that the embodiments disclosed in this specification and drawings aim to solve is to enable the formation of a static magnetic field distribution of a superconducting magnet with a high degree of freedom, and to enable the persistent current mode of the superconducting magnet to be sustained for a long period of time. However, the problems that the embodiments disclosed in this specification and drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0012] A superconducting magnet according to one embodiment comprises: a first coil segment made of a superconducting wire through which a forward current flows; a second coil segment made of the superconducting wire through which a current opposite to the forward current flows; and an intermediate wiring section provided between the first coil segment and the second coil segment, which changes the direction of the current so that the forward current flows through the first coil segment and the reverse current flows through the second coil segment, and connects the first coil segment and the second coil segment without cutting them. [Brief explanation of the drawing]

[0013] [Figure 1] A diagram showing an example of the overall configuration of a magnetic resonance imaging apparatus according to the present invention. [Figure 2] A diagram showing the first example of a planar superconducting magnet. [Figure 3] A diagram showing a second example of a flat-plate superconducting magnet. [Figure 4] (a) is a perspective view showing a schematic outline of a cylindrical superconducting magnet, and (b) is a cross-sectional view showing a schematic internal structure of a cylindrical superconducting magnet. [Figure 5] (a) is a perspective view showing a schematic outline of a planar superconducting magnet, and (b) is a cross-sectional view showing a schematic internal structure of a planar superconducting magnet. [Figure 6] (a) is a cross-sectional view of a superconducting magnet, and (b) is a magnified cross-sectional view of one of the two superconducting magnets. [Figure 7] A diagram illustrating the details of the winding frame and superconducting coil. [Figure 8] (a) is a schematic diagram showing a superconducting connection used in a conventional superconducting magnet, and (b) is a diagram showing an example in which the superconducting connection is reduced in the superconducting magnet of the embodiment. [Figure 9] (a) is a diagram showing an example of the configuration of a superconducting magnet according to a first modified embodiment, and (b) is a diagram showing an example of the configuration of a superconducting magnet according to a second modified embodiment. [Figure 10] (a) is the same figure as Figure 9(a), and (b) is a figure showing an example of the configuration of a superconducting magnet according to a third modified embodiment. [Figure 11] (a) shows a configuration example of a superconducting magnet according to a fourth modification of an embodiment, and (b) shows an equivalent circuit thereof.

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. (Magnetic Resonance Imaging Apparatus) FIG. 1 is a block diagram showing the overall configuration of a magnetic resonance imaging apparatus 1 including a superconducting magnet 10 according to the first embodiment. The magnetic resonance imaging apparatus 1 includes a magnet gantry 100, a bed 500, a control cabinet 300, a console 400, and the like.

[0015] The magnet gantry 100 has a superconducting magnet 10, a gradient magnetic field coil 11, a WB (Whole Body) coil 12, etc., and these components are housed in a cylindrical housing. The bed 500 has a bed body 50 and a top plate 51. Further, the magnetic resonance imaging apparatus 1 has a local coil 20 disposed close to the subject.

[0016] The control cabinet 300 includes gradient magnetic field power supplies 31 (31x for the X-axis, 31y for the Y-axis, 31z for the Z-axis), an RF receiver 32, an RF transmitter 33, and a sequence controller 34.

[0017] The superconducting magnet 10 of the magnet stand 100 has a generally cylindrical shape and generates a static magnetic field in the space inside the cylinder of the superconducting magnet 10, which is the imaging region of the subject (for example, a patient). The superconducting magnet 10 incorporates a superconducting coil, and the superconducting coil is cooled to an extremely low temperature by a refrigerant such as liquid helium or by a conduction cooling method or the like. The superconducting magnet 10 generates a static magnetic field by applying a current supplied from a static magnetic field power source (not shown) to the superconducting coil in the excitation mode, and then, when shifting to the persistent current mode, the static magnetic field power source is disconnected. Once shifting to the persistent current mode, the superconducting magnet 10 continues to generate a large static magnetic field for a long time, for example, over one year. The more specific configuration and functions of the superconducting magnet 10 according to the embodiment will be described later.

[0018] The gradient magnetic field coil 11 also has a generally cylindrical shape and is fixed inside the superconducting magnet 10. This gradient magnetic field coil 11 applies a gradient magnetic field to the subject in the directions of the X-axis, Y-axis, and Z-axis by a current supplied from the gradient magnetic field power sources (31x, 31y, 31z).

[0019] The bed body 50 of the bed 500 is movable in the vertical direction of the top plate 51, and moves the subject placed on the top plate 51 to a predetermined height before imaging. Then, at the time of imaging, the top plate 51 is moved in the horizontal direction to move the subject into the imaging space.

[0020] The WB coil 12 is fixed in a generally cylindrical shape so as to surround the subject inside the gradient magnetic field coil 11. The WB coil 12 transmits the RF pulse transmitted from the RF transmitter 33 toward the subject, and also receives the MR signal emitted from the subject due to the excitation of hydrogen atomic nuclei. [[ID=十三]]

[0021] The local coil 20, also called a surface coil or an RF coil, receives the magnetic resonance signal emitted from the subject at a position close to the body surface of the subject. The local coil 20 is composed of, for example, a plurality of element coils. The local coil 20 has various types such as for the head, chest, spine, lower limbs, or whole body according to the imaging site of the subject, and in FIG. 1, the local coil 20 for the chest is illustrated.

[0022] The RF transmitter 33 transmits RF pulses to the WB coil 12 based on instructions from the sequence controller 34. Meanwhile, the RF receiver 32 detects the MR signal received by the WB coil 12 and the local coil 20, digitizes the detected MR signal, and sends it to the sequence controller 34.

[0023] The sequence controller 34 performs a scan of the subject by driving the gradient power supply 31, RF transmitter 33, and RF receiver 32, respectively, under the control of the console 400. The sequence controller 34 then receives the MR signals collected by the scan from the RF receiver 32 and sends them to the console 400.

[0024] The sequence controller 34 includes a processing circuit (not shown in the diagram). This processing circuit consists of, for example, a processor that executes a predetermined program, or hardware such as an FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit). The console 400 is configured as a computer having a processing circuit 40, a memory circuit 41, an input device 43, and a display 42.

[0025] The memory circuit 41 is a storage medium that includes ROM (Read Only Memory), RAM (Random Access Memory), and external storage devices such as HDD (Hard Disk Drive) and optical disc drives. The memory circuit 41 stores various information and data, as well as various programs executed by the processor equipped in the processing circuit 40.

[0026] The input device 43 includes, for example, a mouse, keyboard, trackball, touch panel, etc., and includes various devices for the operator to input various types of information and data. The display 42 is a display device such as a liquid crystal display panel, plasma display panel, or organic EL panel.

[0027] The processing circuit 40 is, for example, a circuit equipped with a CPU or a dedicated or general-purpose processor. The processor realizes various functions by executing various programs stored in the memory circuit 41. The processing circuit 40 may be composed of hardware such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Furthermore, the processing circuit 40 can realize various functions by combining software processing by the processor and programs with hardware processing.

[0028] The console 400 controls the entire magnetic resonance imaging apparatus 1. Specifically, it receives imaging conditions and other various information and instructions from operators such as medical technologists through the use of a mouse, keyboard, or other input devices (input devices 43). The processing circuit 40 then causes the sequence controller 34 to execute a scan based on the input imaging conditions, while simultaneously reconstructing the image based on the raw data transmitted from the sequence controller 34. The reconstructed image is displayed on the display 42 or stored in the memory circuit 41.

[0029] The magnetic resonance imaging apparatus 1 shown in Figure 1 has a cylindrical superconducting magnet 10, gradient coil 11, and WB coil 12. Therefore, this type of magnetic resonance imaging apparatus 1 will hereafter be referred to as a cylindrical magnetic resonance imaging apparatus. Furthermore, this type of superconducting magnet 10 will be referred to as a cylindrical superconducting magnet 10.

[0030] In cylindrical magnetic resonance imaging systems, imaging is performed in a closed, cylindrical space, which can make imaging difficult for some patients, such as those with claustrophobia.

[0031] In contrast, magnetic resonance imaging (MMRI) systems have been proposed and developed in which the superconducting magnets 10 and gradient magnetic field coils 11 are flat, and the system is configured to image a subject, such as a patient, in an open space sandwiched between two flat superconducting magnets 10. This type of MMRI system will be hereinafter referred to as a planar open-type MMRI system (or simply an open-type MMRI system). In an open-type MMRI system, imaging is performed in an open space, making it possible to image patients with claustrophobia. This type of superconducting magnet 10 will be referred to as a planar superconducting magnet 10.

[0032] Figure 2 shows a first example of a planar superconducting magnet 10. This first example consists of two planar superconducting magnets 10 suitable for imaging a standing subject, for example. In this first example, the standing subject is positioned in an imaging space between two planar superconducting magnets 10, which are arranged so that their respective cylindrical axis directions (the Z-axis direction shown in Figure 2) are coaxial and horizontal, and is imaged from there.

[0033] Figure 3 shows a second example of the planar superconducting magnet 10. In addition to the planar superconducting magnet 10, Figure 3 also shows the bed body 50 and the tabletop 51. This second example is a planar superconducting magnet 10 suitable for imaging a subject lying on the tabletop 51, for example. In this second example, the subject lying on the tabletop 51 is positioned in an imaging space between two planar superconducting magnets 10, which are arranged so that their respective cylindrical axis directions are coaxial and vertical, and is imaged from there.

[0034] Figure 4(a) is a perspective view showing a schematic outline of the cylindrical superconducting magnet 10, and Figure 4(b) is a cross-sectional view showing a schematic internal structure of the cylindrical superconducting magnet 10. Figures 4(a) and 4(b) are intentionally shown with the cylindrical axis perpendicular to allow for comparison with the flat plate superconducting magnet 10 (see Figure 5), which will be described later.

[0035] As shown in Figures 4(a) and 4(b), the cylindrical superconducting magnet 10 has a cylindrical vacuum vessel 110, and an imaging space 120 is formed in the hollow cylindrical region. As shown in Figure 4(b), a superconducting coil 200 and a winding frame 250 around which the superconducting coil 200 is wound are arranged inside the vacuum vessel 110.

[0036] On the other hand, Figure 5(a) is a perspective view showing a schematic outline structure of the flat plate superconducting magnet 10, and Figure 5(b) is a cross-sectional view showing a schematic internal structure of the flat plate superconducting magnet 10.

[0037] Figures 5(a) and 5(b) show the configuration of two planar superconducting magnets 10 arranged vertically. Each planar superconducting magnet 10 has a cylindrical vacuum vessel 110 with planes on its upper and lower sides, and an imaging space 120 is formed in the open space region sandwiched vertically between the two planar superconducting magnets 10.

[0038] As shown in Figure 5(b), a superconducting coil 200 and a winding frame 250 around which the superconducting coil 200 is wound are arranged inside each vacuum vessel 110. The two flat-plate superconducting magnets 10 have substantially the same configuration and structure, and as is clear from Figure 5(b), one flat-plate superconducting magnet 10 is positioned upside down relative to the other. The specific configuration and structure of the superconducting coil 200 and the winding frame 250 will be described later.

[0039] In the following, we will describe the configuration, structure, and characteristics of one of the two flat-plate superconducting magnets 10. However, these descriptions naturally apply to the other flat-plate superconducting magnet 10, and furthermore, to the cylindrical superconducting magnet 10 shown in Figures 4(a) and (b). Therefore, in the following, both the flat-plate superconducting magnet 10 and the cylindrical superconducting magnet 10 will simply be referred to as superconducting magnets 10.

[0040] Figures 6 and 7 illustrate the configuration of the superconducting magnet 10 according to the embodiment, and in particular, the configuration and structure of the superconducting coil 200 and the winding frame 250 of the superconducting magnet 10.

[0041] Figure 6(a) is a cross-sectional view of the same superconducting magnet 10 as Figure 5(b), and Figure 6(b) is an enlarged cross-sectional view of one of the two superconducting magnets 10. As mentioned above, the two superconducting magnets 10 have the same shape and structure, and each superconducting magnet 10 has an axisymmetric shape and structure with respect to the central axis 251 of the cylinder. Therefore, in the following explanation, as shown in Figures 6(b), 7, 8-10, and 11(b), the right-hand cross-sectional view of one superconducting magnet 10 (the upper superconducting magnet 10) will be used to explain the configuration and structure of the superconducting magnet 10.

[0042] As shown in Figure 6(b), the superconducting magnet 10 of the embodiment is configured to include at least a superconducting coil 200 and a winding frame 250 around which the superconducting coil 200 is wound.

[0043] The superconducting coil 200 is configured to include a first coil segment 210 through which a forward current flows, a second coil segment 220 through which a current in the opposite direction to the forward current flows, and an intermediate wiring section 230 that connects the first coil segment 210 and the second coil segment 220 without cutting them.

[0044] Each of the first and second coil segments 210, 220, and the intermediate wiring section 230 is formed using an ultra-fine multi-core wire structure in which a large number of thin filaments of superconducting material such as niobium-titanium (Nb-Ti) are embedded in a normal-conducting base material such as copper. Alternatively, each of the first and second coil segments 210, 220, and the intermediate wiring section 230 is formed using, for example, rare-earth or bismuth-based high-temperature superconducting wires in tape form.

[0045] The intermediate wiring section 230 is a wiring that is wound in such a way that the direction of the current flowing through the first coil segment 210 and the direction of the current flowing through the second coil segment 220 are reversed. By reversing the direction of the current flowing through the first coil segment 210 and the second coil segment 220, the direction of the first magnetic field generated in the first coil segment 210 and the second magnetic field generated in the second coil segment 220 can be reversed. By combining these first and second magnetic fields, the shape and intensity of the static magnetic field distribution can be realized with a high degree of freedom.

[0046] Furthermore, the intermediate wiring section 230 may be made of wiring wound in a non-inductive winding manner. Non-inductive winding is a method of winding wiring such that the magnetic field generated by the intermediate wiring section 230 itself is substantially zero. For example, non-inductive winding can be achieved by winding a first wire wound in a first direction (or first orientation) and a second wire wound in a second direction (or second orientation opposite to the first orientation) in the same position or region, such that they overlap each other with the same amount of wiring.

[0047] As described above, by making the intermediate wiring section 230 a non-inductive winding, the magnetic field generated in the intermediate wiring section 230 can be made virtually zero, or extremely small, so as not to affect the static magnetic field distribution formed by the first coil segment 210 and the second coil segment 220.

[0048] As will be described later, although the first coil segment 210, the second coil segment 220, and the intermediate wiring section 230 are each formed from superconducting wire, they are formed from a single continuous superconducting wire without using superconducting connections.

[0049] As mentioned above, a superconducting connection is a connection method that connects superconducting wires that are separated from each other using various connection methods such as soldering or crimping.

[0050] On the other hand, the reel frame 250 is a frame around which the superconducting coil 200 (i.e., the first coil segment 210, the second coil segment 220, and the intermediate wiring section 230) is wound. In particular, the reel frame 250 of the embodiment is formed to facilitate the positioning of the first coil segment 210, the second coil segment 220, and the intermediate wiring section 230.

[0051] The reel frame 250 may be formed, for example, by processing a single cylindrical member, or by processing multiple cylindrical members stacked on top of each other. A cylindrical hollow region 270 is formed in the center of the cylindrical member. When the superconducting magnet 10 is formed as a cylindrical superconducting magnet 10, this hollow region 270 becomes the imaging space for the subject. Figure 7 is a diagram illustrating the details of the winding frame 250 and the superconducting coil 200, and for illustrative purposes, the winding frame 250 and the superconducting coil 200 are shown separately.

[0052] As shown on the right side of Figure 7, the first coil segment 210 is composed of multiple first subcoil segments 211. Furthermore, these multiple first subcoil segments 211 are formed by a single superconducting wire without the use of superconducting connections. Note that the number of first subcoil segments 211 can also be set to one.

[0053] Similarly, the second coil segment 220 is composed of multiple second subcoil segments 221. These multiple second subcoil segments 221 are also formed from a single superconducting wire without the use of superconducting connections. The number of second subcoil segments 221 can also be limited to one.

[0054] On the other hand, as shown on the left side of Figure 7, the winding frame 250 has guide structures 260 formed therein to define the winding positions of each first subcoil segment 211, each second subcoil segment 221, and the intermediate wiring section.

[0055] The guide structure 260 includes, for example, steps 261 and grooves 262, and also includes holes and rails, as will be described later. The steps 261 and grooves 262 are created by forming multiple steps on the outer circumference of the cylindrical member so that they have multiple different outer diameters along the direction of the central axis of the cylinder.

[0056] To obtain a desired static magnetic field distribution, the radial and axial positions of each first subcoil segment 211 and each second subcoil segment 221 are determined in advance by calculation or other means. Then, based on the determined radial and axial positions, the guide structures 260, such as steps 261 and grooves 262, can be determined.

[0057] In addition, the reel frame 250 may be equipped with fixing means for fixing each first subcoil segment 211, each second subcoil segment 221, or the intermediate wiring section 230, such as fixing brackets or fixing bands.

[0058] As described above, the superconducting magnet 10 according to this embodiment eliminates or reduces superconducting connections as much as possible. Figure 8(a) is a schematic diagram showing the configuration of a conventional superconducting magnet 600 and the superconducting connection SJ used therein, as a comparative example to the superconducting magnet 10 of this embodiment.

[0059] Conventional superconducting magnets 600 have a configuration in which multiple isolated superconducting coils are connected to each other by superconducting connections. For example, in the example shown in Figure 8(a), a conventional superconducting magnet 600 has four isolated superconducting coils 610, 620, 630, and 640, which are wound on two winding frames 650 and 660 and connected by four superconducting connections.

[0060] On the other hand, in the superconducting magnet 10 of the embodiment shown in Figure 8(b), as described above, the first coil segment 210, the second coil segment 220, and the intermediate wiring section 230 that constitute the superconducting coil 200 are each formed from superconducting wire, but they are formed from a single continuous superconducting wire without using superconducting connections. Furthermore, only one point at both ends of the superconducting coil 200 is a superconducting connection.

[0061] Thus, the superconducting magnet 10 of this embodiment has a significantly reduced superconducting connection compared to the conventional superconducting magnet 600. Consequently, the resistance value due to the superconducting connection is reduced, and the duration of the persistent current mode can be extended. Furthermore, the second coil segment 220 is wound in close proximity to the first coil segment 210, and part or all of the winding portion of the second coil segment 220 may be substantially non-inductive winding.

[0062] (A variation of a superconducting magnet) Figure 9(a) shows an example of the configuration of a superconducting magnet 10 according to a first modification of the embodiment. In the first modification, a sub-coil segment for fine adjustment of the magnetic field is included, and a hole is formed in the winding frame 250 for passing the sub-coil segment through in order to position this sub-coil segment.

[0063] Figure 9(b) shows an example of the configuration of a superconducting magnet 10 according to a second modification of the embodiment. In the second modification, the cylindrical member is formed to have a hollow region 270a, as well as multiple cavity regions 270b with different inner diameters corresponding to multiple different outer diameters. By providing the cavity regions 270b in the cylindrical member, the weight of the superconducting magnet 10 can be reduced. Furthermore, as shown in Figure 9(b), the sub-coil segment for fine-tuning the magnetic field is positioned by a rail, which serves as a guide structure 260 for the winding frame 250.

[0064] Figure 10(b) shows an example of the configuration of the superconducting magnet 10 according to the third modified embodiment. Figure 10(a) is the same as the first modified embodiment (Figure 9(a)) for comparison with the third modified embodiment.

[0065] In the third modified example, the cylindrical member is formed solidly, and unlike the first embodiment, its first modified example, and its second modified example, there is no hollow region 270 in the center of the cylinder. The third modified example is a configuration specific to the flat plate superconducting magnet 10. In the superconducting magnet 10 according to the third modified example, the imaging space on which the subject is placed during imaging is formed in the axial direction of the cylindrical member and in the region outside the winding frame 250.

[0066] Figure 11(a) is a diagram showing an example configuration of a superconducting magnet 10 according to a fourth modification of the embodiment, and Figure 11(b) is a diagram showing its equivalent circuit. The superconducting magnet 10 according to the fourth modification has a configuration that includes a third coil segment 240 and a permanent current switch 242, in addition to the first coil segment 210, the second coil segment 220, and the intermediate wiring section 230. As shown in Figure 11(b), the permanent current switch 242 is provided between the third coil segment 240 and at least one of the first coil segment 210 and the second coil segment 220.

[0067] In addition, Figure 11(b) also shows the external configuration of the superconducting magnet 10, including the permanent magnet power supply 160 and the permanent current switch 150 for transitioning from the excitation mode to the permanent current mode.

[0068] The third coil segment 240 is configured to generate a magnetic field that cancels all or part of the magnetic field generated by the first coil segment 210 or the second coil segment 220 when the persistent current switch 242 is turned on. The third coil segment 240 and the persistent current switch 242 allow for more flexible adjustment of the strength and shape of the static magnetic field distribution.

[0069] Up to this point, we have described two opposing planar superconducting magnets 10 as examples of the superconducting magnets 10 used in an open-type magnetic resonance imaging apparatus. However, a configuration with only one planar superconducting magnet 10 is also acceptable. For example, as shown in Figure 3, a configuration with only one superconducting magnet 10 located below the top plate 51 is also acceptable.

[0070] As described above, according to at least one embodiment of the superconducting magnet, the static magnetic field distribution of the superconducting magnet can be formed with a high degree of freedom, and the persistent current mode of the superconducting magnet can be maintained for a long period of time.

[0071] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0072] 1. Magnetic Resonance Imaging System 10 Superconducting Magnets 110 Vacuum container 200 Superconducting Coils 210 First coil segment 211 First subcoil segment 220 Second coil segment 221 Second subcoil segment 230 Intermediate wiring section 240 Third coil segment 242 Permanent Current Switch 260 Guide Structure 261 steps 262 Groove

Claims

1. The first coil segment is composed of superconducting wires through which a forward current flows, A second coil segment, composed of the aforementioned superconducting wire, through which a current flows in the reverse direction to the forward direction, An intermediate wiring section is provided between the first coil segment and the second coil segment, which changes the direction of the current so that the forward current flows through the first coil segment and the reverse current flows through the second coil segment, and superconducts the first coil segment and the second coil segment together with a single continuous superconducting wire without cutting them. The system comprises a winding frame for winding the superconducting wire, The first coil segment, the second coil segment, and the intermediate wiring section are each superconducting magnets wound at different positions in the axial direction of the winding frame.

2. The second coil segment is wound in close proximity to the first coil segment, and part or all of the winding portion of the second coil segment is substantially non-inductive. The superconducting magnet according to claim 1.

3. The intermediate wiring section is a wiring made of superconducting wire wound in a non-inductive winding manner, which reverses the direction of the current flowing through the first coil segment and the second coil segment, and substantially reduces the magnetic field generated in the intermediate wiring section to zero. The superconducting magnet according to claim 1.

4. The intermediate wiring section is formed by winding the forward wiring and the reverse wiring so that they overlap at the same position or region in the axial direction of the winding frame. The superconducting magnet according to claim 3.

5. Formed in a flat plate shape, The superconducting magnet according to claim 1.

6. A first coil segment made of superconducting wire through which a forward current flows, A second coil segment, composed of the aforementioned superconducting wire, through which a current flows in the reverse direction to the forward direction, An intermediate wiring section is provided between the first coil segment and the second coil segment, which changes the direction of the current so that the forward current flows through the first coil segment and the reverse current flows through the second coil segment, and superconducts the first coil segment and the second coil segment together with a single continuous superconducting wire without cutting them. The system comprises a winding frame for winding the superconducting wire, The first coil segment is composed of one or more first subcoil segments, and the one or more first subcoil segments are formed from one superconducting wire without using the superconducting connection. The second coil segment is composed of one or more second subcoil segments, and the one or more second subcoil segments are formed from one superconducting wire without using the superconducting connection. The winding frame is provided with a guide structure for defining the winding positions of the one or more first subcoil segments, the one or more second subcoil segments, and the intermediate wiring section. Superconducting magnet.

7. The winding positions of the one or more first subcoil segments and the one or more second subcoil segments are determined based on a predetermined static magnetic field distribution. The superconducting magnet according to claim 6.

8. The guide structure includes at least one of a step, groove, hole, and rail formed along the circumferential direction of the winding frame. The superconducting magnet according to claim 6.

9. The winding frame comprises fixing means for fixing one or more first subcoil segments, one or more second subcoil segments, and at least one of the intermediate wiring sections, which are positioned by the guide structure. The superconducting magnet according to claim 6.

10. The winding frame is produced by forming multiple steps on the outer circumference of the cylindrical member so that it has multiple outer diameters that differ along the axial direction of the cylindrical member. The cylindrical member is hollow, and the imaging space on which the subject is placed during imaging corresponds to the hollow region. The superconducting magnet according to claim 6.

11. The hollow region of the cylindrical member is formed to have multiple different inner diameters corresponding to the multiple different outer diameters. The superconducting magnet according to claim 10.

12. The winding frame is produced by forming multiple steps on the outer circumference of the cylindrical member so that it has multiple outer diameters that differ along the axial direction of the cylindrical member. The cylindrical member is formed solid, and the imaging space on which the subject is placed during imaging corresponds to the area outside the winding frame in the axial direction of the cylindrical member. The superconducting magnet according to claim 6.

13. The third coil segment and A persistent current switch is provided between the third coil segment and at least one of the first coil segment and the second coil segment, Furthermore, The third coil segment is configured to generate a magnetic field that cancels all or part of the magnetic field generated by the first coil segment or the second coil segment when the persistent current switch is turned on. The superconducting magnet according to claim 1.

14. A magnetic resonance imaging apparatus comprising a superconducting magnet according to any one of claims 1 to 13.

Images