JP2004130052A - Gradient magnetic field coil device and magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gradient magnetic field coil device, realized by upgrade to an existing system without generation of artifact and noise even if an active shield gradient magnetic field coil device (ASGC) is shorter than a static magnetic field generating magnet, and a magnetic resonance imaging apparatus. <P>SOLUTION: A magnetic field intercepting part formed of a conductive metal is provided at the end of the ASGC axially shorter than the static magnetic field generating magnet. The magnetic field generated from the end of the ASGC with application of a pulsed current is intercepted by coupling with the magnetic field intercepting part. Thus, electromagnetic coupling between the gradient magnetic field generated by the ASGC and the static magnetic field generating magnet can be restrained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic resonance imaging apparatus used in the medical field and a gradient coil device used for the magnetic resonance imaging apparatus.
[0002]
[Prior art]
2. Description of the Related Art A magnetic resonance imaging (MRI) apparatus is an image diagnostic apparatus that images a spatial distribution of nuclear magnetization using a nuclear magnetic resonance phenomenon. It is possible to collect images having excellent contrast in soft tissue mainly by utilizing the hydrogen atom density, relaxation time, blood flow information, and the like of the human body, and occupies an important position in medical image diagnosis. This magnetic resonance imaging apparatus includes, for example, a main magnet for generating a static magnetic field, an irradiation coil for irradiating a high frequency magnetic field to a subject, a receiving coil for receiving an NMR signal from the subject, and a gradient coil for generating a gradient magnetic field. It has a gradient coil device.
[0003]
The quality of a magnetic resonance image is affected by various factors. One of the factors is an eddy current. This is, for example, a current generated in the outer wall of the main magnet, the gradient coil, or the like due to a pulse current flowing through the gradient coil device, and causes an artifact.
[0004]
As a technique for suppressing the generation of the eddy current, there is a technique called an active shielded gradient coil device (hereinafter, referred to as “ASGC”). In this technology, the gradient magnetic field coil device is composed of two layers of a main coil and a shield coil, and by supplying currents in opposite directions to each other, the magnetic fields generated by each are canceled out and the generation of eddy current is suppressed. Things.
[0005]
By the way, in recent years, the length of a mount (including a static magnetic field generating magnet, ASGC, and the like) of a magnetic resonance imaging apparatus tends to be shorter. This is to prevent a patient entering the mount, which is a narrow space surrounded by static magnetic field magnets and the like, from feeling blocked.
[0006]
However, when the ASGC is shorter than the static magnetic field generating magnet, the leakage magnetic field from the end of the ASGC increases, and electromagnetic coupling is induced. The electromagnetic coupling generates an eddy current in the ASGC or the like, and generates an artifact or noise caused by the eddy current.
[0007]
As a solution to this problem, for example, a method has been disclosed in which the generation of eddy currents is prevented by making the interior of the magnet for generating a static magnetic field nonconductive, such as FRP, to thereby reduce noise (for example, William A. EDELSTEIN, et al "Making MRI Quiet": Proc. Intl. Soc. Mag. Reson. Med. Int. Soc.Mag.Reson.Med 9, 1751 (2001) However, since this method cannot be applied to a system that has already been introduced, an update from a conventional model is not possible. It can not be realized in the grade.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and does not generate an artifact or noise even when the ASGC is shorter than the static magnetic field generating magnet, and the gradient magnetic field that can be realized by upgrading the existing system. It is an object to provide a coil device and a magnetic resonance imaging device.
[0009]
[Means for Solving the Problems]
The present invention employs the following means to achieve the above object.
[0010]
A first aspect of the present invention is a gradient magnetic field coil device used in a magnetic resonance imaging apparatus that receives a magnetic resonance signal generated from a subject disposed in a static magnetic field generated by a magnet and generates a magnetic resonance image And a first coil for generating a gradient magnetic field in a predetermined area in the static magnetic field area, and a second coil for generating a magnetic field for canceling the gradient magnetic field leaking out of the predetermined area. And a magnetic field blocking means for blocking a magnetic field leaking from at least one end of the shield type coil.
[0011]
A second aspect of the present invention is a magnetic resonance imaging apparatus that receives a magnetic resonance signal generated from a subject existing in a static magnetic field region and generates a magnetic resonance image, and includes a space for arranging the subject. A magnet that generates the static magnetic field, and a gradient coil device that has a shorter axis than the magnet in the longitudinal direction of the magnet and is provided in the space for arranging the subject. A first coil for supplying a gradient magnetic field to a predetermined area in the static magnetic field area, and a first coil for generating a magnetic field for canceling the gradient magnetic field leaking out of the predetermined area. A magnetic resonance imaging apparatus comprising: a shield type coil having two coils; and a magnetic field blocking unit for blocking a magnetic field leaking from at least one end of the shield type coil.
[0012]
According to such a configuration, even when the ASGC is shorter than the static magnetic field generating magnet, the gradient magnetic field coil device which does not generate an artifact or noise and can be realized by upgrading an existing system, and a magnetic resonance apparatus. An image device can be realized.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, components having substantially the same functions and configurations are denoted by the same reference numerals, and repeated description will be made only when necessary.
[0014]
FIG. 1 is a block diagram illustrating a configuration of the magnetic resonance imaging apparatus according to the present embodiment. In FIG. 1, a magnetic resonance imaging apparatus 10 includes a static magnetic field magnet 11, a gradient magnetic field coil device 13, a shim coil 12, a high frequency coil 14, a gradient magnetic field coil device power supply 16, a shim coil power supply 17, a transmission unit 18, a reception unit 19, and data collection. It comprises a unit 20, a sequence control unit 21, a computer system 22, a console 23, and a display 24.
[0015]
The static magnetic field magnet 11 is a magnet that generates a static magnetic field, and generates a uniform static magnetic field. As the static magnetic field magnet 11, for example, a permanent magnet, a superconducting magnet, or the like is used.
[0016]
The gradient magnetic field coil device 13 is provided inside the static magnetic field magnet 11 and has a shorter axis than the static magnetic field magnet 11, and converts a pulse current supplied from the gradient magnetic field coil device power supply 16 into a gradient magnetic field. The signal generation site (position) is specified by the gradient magnetic field generated by the gradient magnetic field coil device 13.
[0017]
The gradient magnetic field coil device 13 has a function as an active shielded gradient magnetic coil device (hereinafter, referred to as “ASGC”). Furthermore, the gradient magnetic field coil device 13 has a magnetic field cutoff unit for suppressing an eddy current generated by a change in a magnetic field due to application of a pulse current (see FIG. 2). This will be described later in detail.
[0018]
In the present embodiment, the gradient magnetic field coil device 13 and the static magnetic field magnet 11 have a cylindrical shape, and the gradient magnetic field coil device 13 is arranged in a vacuum by a predetermined support mechanism. This is because, from the viewpoint of noise reduction, the vibration of the gradient magnetic field coil device 13 generated by the application of the pulse current is not transmitted to the outside as sound waves.
[0019]
The shim coil 12 is provided inside the static magnetic field magnet 11, and is a coil for actively increasing the uniformity of the magnetic field. The shim coil 12 is driven by a shim coil power supply 17.
[0020]
The shim coil 12 and the gradient magnetic field coil device 13 apply a uniform static magnetic field and a gradient magnetic field having linear gradient magnetic field distributions in three orthogonal directions X, Y, and Z to a subject (not shown). In the present embodiment, the Z-axis direction is assumed to be the same as the direction of the static magnetic field.
[0021]
The high-frequency coil (RF coil) 14 is connected to a transmission high-frequency coil for applying a high-frequency pulse for generating a magnetic resonance signal to the imaging region of the subject in the vicinity of, preferably in close contact with, the subject. A receiving high-frequency coil is provided so as to sandwich the subject and receives magnetic resonance from the subject. The high-frequency coil 14 generally has a dedicated shape for each part.
[0022]
The transmission unit 18 includes an oscillation unit, a phase selection unit, a frequency conversion unit, an amplitude modulation unit, and a high-frequency power amplification unit (each not shown), and transmits a high-frequency pulse corresponding to the Larmor frequency to the transmission high-frequency coil. I do. By the high frequency generated from the high-frequency coil 14 by the transmission, the magnetization of a predetermined atomic nucleus of the subject is in an excited state.
[0023]
The receiving unit 19 includes an amplifier, an intermediate frequency converter, a phase detector, a filter, and an A / D converter (each not shown). The receiving unit 19 amplifies a magnetic resonance signal (high-frequency signal) emitted from the high-frequency coil 14 when the magnetization of the nucleus is relaxed from the excited state to the ground state, and performs an intermediate frequency conversion process using the transmission frequency. , Phase detection processing, filter processing, and A / D conversion processing.
[0024]
The data collection unit 20 collects digital signals sampled by the reception unit 19.
[0025]
The sequence control unit 21 controls the gradient coil device power supply 16, the shim coil power supply 17, the transmission unit 18, the reception unit 19, and the data collection unit 20.
[0026]
The computer system 22 controls the sequence control unit 21 based on a command input from the console 23. The computer system 22 performs post-processing, that is, reconstruction such as Fourier transform, on the magnetic resonance signal input from the data acquisition unit 20, and obtains spectrum data or image data of a desired nuclear spin in the subject. .
[0027]
The console 23 has an input device (mouse, trackball, mode switch, keyboard, etc.) for receiving various instructions, commands, and information from the operator.
[0028]
The display 24 is an output unit that displays spectrum data or image data input from the computer system 22.
[0029]
(Gradient magnetic field coil device)
Next, details of the configuration of the gradient coil device 13 will be described with reference to FIG. The present gradient magnetic field coil device 13 is a hybrid gradient magnetic field coil device (Hybrid Shield) that combines a function of actively shielding a magnetic field (Active Shield) and a function of passively shielding (Passive Shield).
Gradient Coil: hereinafter referred to as “HSGC”).
[0030]
FIG. 2A is a diagram showing a part (lower half) of a cross section along the longitudinal direction of the gradient coil device 13. As shown in FIG. 2A, the gradient magnetic field coil device 13 includes an ASGC 130 having a function of actively shielding a magnetic field, and a magnetic field blocking unit 131 for passively blocking a magnetic field.
[0031]
The ASGC 130 includes a main coil 13a for generating a gradient magnetic field, and a shield coil 13b for canceling a leakage magnetic field from the main coil outside (see FIGS. 6 and 8). Opposite currents are supplied to the main coil 13a and the shield coil 13b so as to actively cancel the magnetic fields generated respectively.
[0032]
The magnetic field blocking units 131 are made of a conductive metal such as copper or aluminum, and are provided along both ends of the ASGC 130. In the present embodiment, since the ASGC 130 is cylindrical, the magnetic field blocking unit 131 is cylindrical along the end of the ASGC 130. Further, the magnetic field blocking unit 131 has a protrusion 1310 for effectively blocking the magnetic field leaking from the end of the ASGC 130. Note that the magnetic field blocking unit 131 vibrates due to the electromagnetic coupling and can be a noise source. In order to prevent this, the magnetic field interrupting unit 131 is supported by a mechanism independent of the static magnetic field magnet 11, or a vibration isolating material is provided on the static magnetic field magnet 11 to support it, so that vibration is not transmitted to the static magnetic field magnet 11. To do.
[0033]
The magnetic field generated from the end of the ASGC 130 due to the pulse current is cut off by coupling with the magnetic field cutoff unit 131. The length of the magnetic field blocking unit 131 in the direction of the central axis (the z direction in FIG. 2A) may be appropriately selected so as to sufficiently block the magnetic field leaking from the end of the ASGC 130.
[0034]
FIG. 2B is a diagram showing a modification of the gradient coil device 13. In the example of FIG. 2B, the gradient magnetic field coil device 13 includes a magnetic field blocking unit 132 provided along both ends of the ASGC 130 and covering at least a part of the end surface of the ASGC 130 with the wraparound unit 1320. I have. The magnetic field generated from the end of the ASGC 130 can be sufficiently blocked by such a magnetic field blocking unit 132 as well.
[0035]
It should be noted that the magnetic field cutoff unit that passively cuts off the magnetic field is not limited to the forms shown in FIGS. 2A and 2B, and preferably takes an appropriate form corresponding to the form of each system. For example, the embodiment shown in FIGS. 3A, 3B, 4A, and 4B shown below may be used.
[0036]
The gradient magnetic field coil device 13 shown in FIG. 3A is provided in a space between the housing of the ASGC 130 and the housing of the static magnetic field magnet 11 so as to surround the ASGC 130, and is longer than the ASGC 130 in the z direction (that is, longer than the ASGC 130). , Having a protrusion 1330). Further, the gradient coil device 13 shown in FIG. 3B is provided in a space between the housing of the ASGC 130 and the housing of the static magnetic field magnet 11 so as to surround the ASGC 130, and at least a part of the end face of the ASGC 130 is provided. It has a magnetic field cutoff part 132 covered by the wraparound part 1340.
[0037]
FIG. 4A is a diagram showing a part of a mount of the magnetic resonance imaging apparatus 10 having the opposed-type static magnetic field magnet 11. As shown in FIG. 4B, in the space between the housing of the ASGC 130 and the housing of the static magnetic field magnet 11, a tape, an adhesive or the like is attached to the housing of the ASGC 130, as shown in FIG. In this case, it is sufficient to adopt a form in which it is firmly fixed.
[0038]
As described above, the magnetic field generated from the end of the ASGC 130 can be sufficiently cut off by the appropriate magnetic field cut-off unit corresponding to the form of each system.
[0039]
Next, the operation of the gradient magnetic field coil device 13 will be described with a focus on the function of the magnetic field blocking unit, in comparison with a conventional gradient magnetic field coil device.
[0040]
FIG. 5 is a diagram showing a distribution of a magnetic field formed when a pulse current is applied to a conventional gradient coil device 50 (which has a shorter axis than the static magnetic field generating magnet). As shown in the figure, the magnetic flux density is particularly large near the end of the gradient magnetic field coil device 50, and thus there is an environment in which electromagnetic coupling between the magnetic field and the static magnetic field magnet occurs.
[0041]
On the other hand, FIG. 7 is a diagram showing a distribution of a magnetic field formed when a pulse current is applied to the gradient coil device 13. 7 and FIG. 5, the magnetic field blocking function of the magnetic field blocking unit clearly shows that the magnetic flux density is small near the end of the gradient coil device 13, and thus the electromagnetic coupling between the magnetic field and the static magnetic field magnet is reduced. Is suppressed. According to the experiments performed by the inventors, the eddy current generated at the end of the shield coil 13b due to the electromagnetic coupling between the magnetic field generated by the gradient coil device 13 and the static magnetic field magnet is caused by the region R2 in FIG. (At the end of ASGC), and was found to be reduced to 1/17 of the eddy current generated in the region R1 (at the end of ASGC) in FIG. In addition, even when calculation errors were taken into account, there was an effect of suppressing electromagnetic coupling by 20 dB or more as compared with the related art.
[0042]
According to the configuration described above, the following effects can be obtained.
In this magnetic resonance imaging apparatus, the magnetic field generated from the end of the ASGC is sufficiently blocked by the magnetic field blocking unit provided in the gradient coil device. Therefore, electromagnetic coupling between the magnetic field generated by the gradient coil device and the static magnetic field magnet can be suppressed. As a result, even when ASGC is shorter than the magnet for generating a static magnetic field, it is possible to provide a high quality magnetic resonance image without generating artifacts.
[0043]
The present magnetic resonance imaging apparatus can be realized only by providing a magnetic field blocking unit in the ASGC of an existing system. Therefore, the present invention can be realized by upgrading from a conventional model without replacing expensive static magnetic field generating magnets, gradient magnetic field coil devices, and the like.
[0044]
The magnetic field interrupter is made of a conductive metal such as copper or aluminum, and is relatively inexpensive. Further, the magnetic field interrupting section can be easily installed on the ASGC by a normal method such as an adhesive or a fixing device. Therefore, the present magnetic resonance imaging apparatus can be realized simply and at low cost.
[0045]
Further, according to the present magnetic resonance imaging apparatus, noise during imaging can be reduced for the following reasons. That is, generally, as a cause of noise during the operation of the magnetic resonance imaging apparatus, the vibration itself of the gradient magnetic field coil device directly vibrates the air, and the vibration of the gradient magnetic field coil device causes the external air to vibrate through the support mechanism. It can be considered that the static magnetic field magnet vibrates external air due to the electromagnetic coupling between the magnetic field generated by the gradient magnetic field coil device and the static magnetic field magnet. In the present magnetic resonance imaging apparatus, the magnetic coupling between the magnetic field generated by the gradient coil device and the static magnetic field magnet is suppressed by the function of the magnetic field blocking unit provided in the gradient magnetic field coil device. Can be prevented from vibrating. Further, since the gradient magnetic field coil device is disposed in a vacuum, propagation of the vibration of the gradient magnetic field coil device to the air can be prevented.
[0046]
(Second embodiment)
In the first embodiment, the electromagnetic coupling between the gradient magnetic field and the static magnetic field magnet can be significantly suppressed by the magnetic field blocking function of the magnetic field blocking unit 131 as compared with the related art (see FIGS. 5 and 7). .). However, in FIG. 7, in the region A near the end point of the static magnetic field magnet 11, the distribution of the magnetic field is still dense, and electromagnetic coupling between the gradient magnetic field and the static magnetic field magnet is easily induced. This coupling vibrates the end face of the static magnetic field magnet and acts in the same manner as the principle of striking a drum, which also causes a large noise.
[0047]
Therefore, in the second embodiment, a gradient coil device as an HSGC that reduces the density of the magnetic field near the end point of the static magnetic field magnet 11 and more appropriately suppresses the electromagnetic coupling between the gradient magnetic field and the static magnetic field magnet, And a magnetic resonance imaging apparatus having the same will be described.
[0048]
FIG. 9A is a diagram showing a part of a cross section along the longitudinal direction of the gradient coil device 13 according to the present embodiment. As shown in FIG. 9A, the gradient coil device 13 includes a magnetic field blocking unit 31 for passively blocking a magnetic field. The magnetic field blocking unit 31 includes a protrusion 310 for effectively blocking the magnetic field leaking from the end of the ASGC 130 and an end face of the static magnetic field magnet 11 for effectively blocking the magnetic field leaking from the end of the static magnetic field magnet 11. And a wraparound portion 33 that wraps around. Note that, as in the first embodiment, the magnetic field cutoff section 31 is made of a conductive metal such as copper or aluminum and is provided along the contour of both ends of the ASGC 130. In addition, a vibration isolator (not shown) is provided between the magnetic field blocking unit 31 and the static magnetic field magnet 11.
[0049]
The magnetic field generated from the end of the ASGC 130 due to the pulse current is cut off by coupling with the magnetic field cutoff unit 31. In particular, since the wraparound portion 33 is electromagnetically coupled with the gradient magnetic field or the static magnetic field magnet, it is possible to suppress the generation of the magnetic field near the end point of the static magnetic field magnet 11 (region A in FIG. 7). The magnetic field cutoff unit 31 vibrates violently due to a gradient magnetic field or an electromagnetic coupling with a static magnetic field magnet, but this vibration can be absorbed by a vibration isolator provided between the ASGC 130 and the static magnetic field magnet 11. it can.
[0050]
FIG. 9B is a diagram illustrating a modified example of the gradient coil device 13 according to the present embodiment. In the example of FIG. 9B, the magnetic field blocking unit 32 is provided along the longitudinal direction of the ASGC 130, and has a protruding portion 310 and a wraparound portion 33 that goes around the end surface of the static magnetic field magnet 11. The magnetic field generated from the end of the ASGC 130 can also be sufficiently blocked by such a magnetic field blocking unit 32.
[0051]
According to experiments by the inventors, it is preferable that the wraparound portion 33 has an area that covers approximately 20% or more of the end face of the static magnetic field magnet 11.
[0052]
Further, as shown in FIGS. 10A and 10B, a configuration in which the first embodiment and the second embodiment are combined may be employed. That is, as shown in FIGS. 10A and 10B, the magnetic field blocking units 35 and 36 include a protruding portion 310 and a first wraparound portion 350 for effectively blocking the magnetic field leaking from the end of the ASGC 130, A configuration may be provided that includes a wraparound portion 33 that wraps around the end face of the static magnetic field magnet 11 in order to effectively block a magnetic field leaking from the end of the static magnetic field magnet 11. With such a configuration, the coupling between the magnetic field leaking from the end of the ASGC 130 and the magnetic field leaking from the end of the static magnetic field magnet 11 can be more reliably prevented.
[0053]
As described above, the present invention has been described based on the embodiments. However, in the scope of the concept of the present invention, those skilled in the art can come up with various modified examples and modified examples. It is understood that it belongs to the scope of the present invention.
[0054]
For example, each embodiment has been described as a configuration in which the magnetic field blocking unit for passively blocking the magnetic field is provided on the gradient magnetic field coil device side. On the other hand, the purpose of the magnetic field interrupter is to prevent the electromagnetic coupling between the magnetic field generated by the gradient coil device and the magnetic field generated by the static magnetic field magnet. It may be a configuration provided on the side.
[0055]
In addition, the embodiments may be implemented in appropriate combinations as much as possible, in which case the combined effects can be obtained. Further, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effects described in the column of the effect of the invention can be solved. When at least one of the above is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.
[0056]
【The invention's effect】
As described above, according to the present invention, even when the ASGC is shorter than the static magnetic field generating magnet, the gradient magnetic field coil device that can be realized by upgrading an existing system without generating an artifact or noise, and a magnetic resonance image The device can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a magnetic resonance imaging apparatus according to an embodiment.
FIG. 2A is a diagram showing a part of a cross section along a longitudinal direction of a gradient coil device according to the present embodiment. FIG. 2B is a diagram illustrating a modified example of the gradient magnetic field coil device having the magnetic field blocking unit.
FIGS. 3A and 3B are views showing a modified example of the gradient coil device according to the present embodiment having a magnetic field cutoff unit.
FIG. 4A is a diagram showing a part of a mount of a magnetic resonance imaging apparatus having a facing type static magnetic field magnet. FIG. 4B is a diagram showing a modification of the gradient coil device according to the present embodiment having a magnetic field cutoff unit.
FIG. 5 is a diagram showing a distribution of a magnetic field formed when a pulse current is applied to a conventional gradient coil device (one having a shorter axis than a static magnetic field generating magnet).
FIG. 6 is a sectional view of a conventional gradient coil device and an end of a static magnetic field generating magnet.
FIG. 7 is a diagram showing a distribution of a magnetic field formed when a pulse current is applied to the gradient coil device according to the present embodiment.
FIG. 8 is a cross-sectional view of a gradient coil device according to the present embodiment and an end of a static magnetic field generating magnet.
FIG. 9A is a diagram showing a part of a cross section along a longitudinal direction of the gradient coil device 13 according to the present embodiment. FIG. 9B is a diagram illustrating a modified example of the gradient coil device 13 according to the present embodiment.
FIGS. 10A and 10B are views showing a modification of the first embodiment or the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Magnetic resonance imaging apparatus 11 ... Static magnetic field magnet 12 ... Shim coil 13 ... Gradient magnetic field coil apparatus 13a ... Main coil 13b ... Shield coil 14 ... High frequency coil 16 ... Gradient magnetic field coil apparatus power supply 17 ... Shim coil power supply 18 ... Transmission part 19 ... Reception Unit 20 Data collection unit 21 Sequence control unit 22 Computer system 23 Console 24 Display 31, 32, 35, 36 Magnetic field blocking unit 33 Wrap-around unit 50 Gradient magnetic field coil device 50b Shield coil 130 ASGC
131 ... magnetic field blocking part 132 ... magnetic field blocking part 133 ... magnetic field blocking parts 310, 1310, 1330 ... protruding parts 350, 1320, 1340 ... wraparound part

Claims (24)

A magnetic field gradient coil device used in a magnetic resonance imaging apparatus that receives a magnetic resonance signal generated from a subject arranged in a static magnetic field generated by a magnet and generates a magnetic resonance image,
A shield having a first coil for generating a gradient magnetic field in a predetermined area in the static magnetic field area, and a second coil for generating a magnetic field for canceling the gradient magnetic field leaking out of the predetermined area; Type coil,
Magnetic field blocking means for blocking a magnetic field leaking from at least one end of the shielded coil,
A gradient coil device comprising: The gradient magnetic field coil device according to claim 1, wherein the magnetic field blocking means is made of a conductive metal. The said magnetic field cut-off means is provided in at least one end part of the said shield type coil, and has a protrusion part which protrudes in the longitudinal direction of the said shield type coil from the said at least one end part. 3. The gradient coil device according to 2. The said magnetic field cut-off means is provided in at least one end part of the said shield type coil, and has a wraparound part which covers at least one part of the end surface of the said at least one end part. Gradient coil device. The gradient magnetic field coil device according to claim 1, wherein the magnetic field blocking unit has a protrusion that covers a side surface of the shield-type coil and protrudes in a longitudinal direction of the shield-type coil. The said magnetic field cut-off means has the wraparound part which covers the side surface of the said shield type coil, and covers at least one part of the end surface of at least one end part of the said shield type coil, The Claims 1 or 2 characterized by the above-mentioned. Gradient coil device. The magnetic field blocking means,
A protrusion provided at at least one end of the shielded coil, and protruding from the at least one end in the longitudinal direction of the shielded coil,
A wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet,
The gradient coil device according to claim 1, further comprising: The magnetic field blocking unit covers a side surface of the shield-type coil, and is provided at at least one end of the shield-type coil, and a protrusion that projects from the at least one end in the longitudinal direction of the shield-type coil. ,
A wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet,
The gradient coil device according to claim 1, further comprising: The magnetic field blocking means,
A protrusion provided at at least one end of the shielded coil, and protruding from at least one of the ends of the shielded coil in a longitudinal direction of the shielded coil,
A first wraparound portion that covers at least a part of an end surface of at least one of the ends of the shielded coil;
A second wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet;
The gradient coil device according to claim 1, further comprising: The magnetic field blocking means covers a side surface of the shield type coil, and is provided at at least one end of the shield type coil, and extends from at least one end of the shield type coil in a longitudinal direction of the shield type coil. A protruding part,
A first wraparound portion that covers at least a part of an end surface of at least one of the ends of the shielded coil;
A second wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet;
The gradient coil device according to claim 1, further comprising: The gradient magnetic field according to any one of claims 1 to 10, further comprising a vibration isolator provided between the magnetic field blocking unit and the magnet and configured to absorb vibration of the magnetic field blocking unit. Coil device. The gradient magnetic field coil device according to any one of claims 1 to 10, wherein the magnetic field cut-off unit is not in spatial contact with the magnet. A magnetic resonance imaging apparatus that receives a magnetic resonance signal generated from a subject present in a static magnetic field region and generates a magnetic resonance image,
Having a space for placing the subject, a magnet for generating the static magnetic field,
A gradient magnetic field coil device that is shorter than the magnet in the longitudinal direction of the magnet and is provided in the space for arranging the subject,
With
The gradient magnetic field coil device includes a first coil that supplies a gradient magnetic field to a predetermined area in the static magnetic field area, and a second coil that generates a magnetic field for canceling the gradient magnetic field leaking out of the predetermined area. And a shield-type coil having:
Magnetic field blocking means for blocking a magnetic field leaking from at least one end of the shielded coil,
A magnetic resonance imaging apparatus characterized in that: 14. The magnetic resonance imaging apparatus according to claim 13, wherein the magnetic field blocking unit is made of a conductive metal. The said magnetic field cut-off means is provided in at least one end of the said shield type coil, and has a protrusion part which protrudes in the longitudinal direction of the said shield type coil from the said at least one end, The Claim 13 or 15. The magnetic resonance imaging apparatus according to 14. The said magnetic field cut-off means is provided in at least one end part of the said shield type coil, and has a wraparound part which covers at least one part of the end surface of the said at least one end part, The Claims 13 or 14 characterized by the above-mentioned. Magnetic resonance imaging equipment. 15. The magnetic resonance imaging apparatus according to claim 13, wherein the magnetic field blocking unit has a protruding portion that covers a side surface of the shield type coil and protrudes in a longitudinal direction of the shield type coil. The said magnetic field cut-off means has the wraparound part which covers the side surface of the said shield type coil, and covers at least one part of the end surface of at least one end part of the said shield type coil, The Claims 13 or 14 characterized by the above-mentioned. Magnetic resonance imaging equipment. The magnetic field blocking means,
A protrusion provided at at least one end of the shielded coil, and protruding from the at least one end in the longitudinal direction of the shielded coil,
A wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet,
The magnetic resonance imaging apparatus according to claim 13, further comprising: The magnetic field blocking unit covers a side surface of the shield-type coil, and is provided at at least one end of the shield-type coil, and a protrusion that projects from the at least one end in the longitudinal direction of the shield-type coil. ,
A wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet,
The magnetic resonance imaging apparatus according to claim 13, further comprising: The magnetic field blocking means,
A protrusion provided at at least one end of the shielded coil, and protruding from at least one of the ends of the shielded coil in a longitudinal direction of the shielded coil,
A first wraparound portion that covers at least a part of an end surface of at least one of the ends of the shielded coil;
A second wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet;
The magnetic resonance imaging apparatus according to claim 13, further comprising: The magnetic field blocking means covers a side surface of the shield type coil, and is provided at at least one end of the shield type coil, and extends from at least one end of the shield type coil in a longitudinal direction of the shield type coil. A protruding part,
A first wraparound portion that covers at least a part of an end surface of at least one of the ends of the shielded coil;
A second wraparound portion covering at least a part of at least one end face of the longitudinal end of the magnet;
The magnetic resonance imaging apparatus according to claim 13, further comprising: 23. The magnetic resonance apparatus according to claim 13, further comprising a vibration damping member provided between the magnetic field blocking unit and the magnet, for absorbing vibration of the magnetic field blocking unit. Imaging device. 23. The magnetic resonance imaging apparatus according to claim 13, wherein the magnetic field blocking unit is not in spatial contact with the magnet.

Images