JP2002085370A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus providing adequate and reliable insulation performance without causing operating errors during manufacture, for the connection of cables to a gradient magnetic field coil. SOLUTION: A cable 60 positioned outside a vacuum container 3 and another cable 8 positioned inside the vacuum container 3 are interconnected via a terminal support member 4 having a relay conductor part, by first connecting a cable terminal 8 to one end of the cable 8; hexagonally compressing them; then directly driving the cable terminal 9 into a screw hole S formed in the relay conductor part 83; then covering the terminal connection between the relay conductor part 83 and the cable terminal 9 with a heat contraction tube part 10 in such a manner as to completely cover the exposed part of the conductor; performing an insulating process; and potting with silicone resin 12 or the like a channel initially formed around the relay conductor part 83 of the terminal support member 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging apparatus for arranging a subject in a uniform static magnetic field and applying a gradient magnetic field and a high-frequency pulse to generate a magnetic resonance diagnostic image based on a magnetic resonance phenomenon.

[0002]

2. Description of the Related Art Generally, a magnetic resonance imaging apparatus of this type includes a static magnetic field magnet for generating a static magnetic field, a gradient magnetic field coil for generating a gradient magnetic field, and an RF coil for generating a radio frequency (RF) pulse. Placing the subject in a uniform static magnetic field generated by a static magnetic field magnet, executing a pulse sequence according to the imaging method, applying a gradient magnetic field by a gradient magnetic field coil, and an RF pulse by an RF coil under predetermined conditions, Collect echo signals from the subject. The acquired echo signals are subjected to reconstruction processing to obtain a magnetic resonance image representing a cross section of the subject.

In recent years, in the technical field of magnetic resonance imaging apparatuses, high-speed imaging techniques have been advanced, and active research and development have been promoted. One of them is MRI high-speed imaging. In MRI high-speed imaging, a high-intensity gradient magnetic field is switched at high speed. For this reason, a large force is generated due to the interaction between the current flowing in the gradient magnetic field coil and the static magnetic field, whereby the gradient magnetic field coil vibrates, and the vibration sound causes noise. This noise is usually 100 db (A) or more, and soundproofing of the subject such as earplugs and headphones is required. Such a noise problem is remarkable in MRI high-speed imaging, but is also the same in ordinary imaging.

Some known techniques relating to noise reduction in a magnetic resonance imaging apparatus are disclosed in, for example,
No. 3,246,146, U.S. Pat.
As described in Japanese Patent Application No. 93,210 and Japanese Patent Application No. 8-274609, a gradient magnetic field coil is housed in a vacuum vessel to suppress air propagation of vibration sound generated from the gradient magnetic field coil. There is something.

When the gradient coil is housed in a vacuum vessel as described above, a discharge start voltage is reduced in the vacuum vessel, so that a discharge easily occurs. For this reason,
Conventional insulation, such as covering with a heat-shrinkable tube or taking a creepage / space distance, is insufficient, and it is necessary to provide appropriate and reliable insulation.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cable connection to a gradient magnetic field coil which is suitable and reliable without causing an operation error during manufacturing. An object of the present invention is to provide a magnetic resonance imaging apparatus capable of obtaining high performance.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the object, the present invention is configured as follows.

(1) A magnetic resonance imaging apparatus according to the present invention, wherein a terminal of a cable connected to a gradient magnetic field coil housed in a container is supported by terminal supporting means on a wall surface of the container. Wherein the terminal is crimped to the cable by hexagonal compression, the terminal is screwed into a screw hole formed in advance in the conductor of the terminal supporting means, and the periphery of the connection portion of the terminal is insulated by insulating means. And

(2) The magnetic resonance imaging apparatus according to the present invention is the apparatus according to the above (1), wherein the insulating means is made of a thermosetting resin covering the terminals. And

(3) The magnetic resonance imaging apparatus according to the present invention is the apparatus according to the above (2), wherein a gap between the thermosetting resin and the terminal supporting means is insulated by a second insulating means. It is characterized by doing.

(4) A magnetic resonance imaging apparatus according to the present invention, wherein a terminal of a cable connected to a gradient magnetic field coil housed in a container is supported on a wall surface of the container by terminal support means. , The cable and at least a part of the terminal of the cable are covered by a third insulating means, and the exposed part of the terminal is connected to the terminal of the gradient coil, and the exposed part is covered by a fourth insulating means. It is characterized by insulation.

(5) The magnetic resonance imaging apparatus according to the present invention is the apparatus according to the above (4), wherein
The gap between the insulating means and the gradient magnetic field coil is insulated by a fourth insulating means.

(6) The magnetic resonance imaging apparatus according to the present invention is the apparatus according to any one of the above (1) to (5), wherein the cable has a vibration or Lorentz force generated in the cable. It is characterized in that it has flexibility enough to block vibration propagation from one end to the other end.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a magnetic resonance imaging apparatus according to an embodiment of the present invention as viewed from the side.

Reference numeral 1 denotes a vacuum container of a superconducting magnet, in which a superconducting coil which is brought into a superconducting state at an extremely low temperature is accommodated. This superconducting coil applies a uniform static magnetic field to the imaging region. The static magnetic field strength required in normal MR imaging is about 0.1 to 1 Tesla. The spatial uniformity of the static magnetic field is required to be several tens of ppm or less, and the imaging region is spherical with a diameter of about 50 cm.

Reference numeral 2 denotes a gradient magnetic field coil, and the vacuum vessel 1
Are arranged in a vacuum vessel 3 having the inner cylinder as a part of a component. The gradient magnetic field coil 2 is for giving a linear gradient to the main magnetic field for the purpose of determining an arbitrary imaging section or adding positional information to an RF signal from the subject. In general, the gradient magnetic field coil 2 is composed of three independent coil sets Gx, Gy, Gz that generate magnetic fields inclined in the orthogonal x, y, and z axes. For example, the gradient magnetic field coil 2 of the present embodiment is an active shield type gradient magnetic field coil (Actively Shield Gradient Coil: ASGC).
And The active shield type gradient coil is provided with a main coil that generates a gradient magnetic field, and a reverse coil to prevent the gradient magnetic field generated from the main coil from leaking outside the gradient coil. An active shield coil for generating a magnetic field.

Reference numeral 60 denotes a cable for inputting a current to the gradient coil 2 housed in the vacuum vessel 3. Reference numeral 4 denotes a terminal support member having a conductor portion for connecting terminals of the cable 60, reference numeral 30 denotes a mounting plate provided on a portion of the vacuum vessel 3 where a penetration is made, and reference numeral 8 denotes a conductor portion of one end of the terminal support member And the multi-end is a gradient coil 2
And a cable for inputting a gradient magnetic field current supplied from the cable 60 to the gradient magnetic field coil 2.

The gradient magnetic field coil 2 is supported by a support arm 13 via a rubber cushion 12 and a position adjusting bolt 11. The support points are 4 on the side surface of the gradient coil 2.
And two places on the bottom. The vibration damping rubber 12 made of an elastic material constitutes a vibration absorbing device (damper) in a broad sense,
The solid vibration of the gradient magnetic field coil 2 is attenuated, and this can be effectively prevented from propagating to the support arm 13 via the position adjusting bolt 11. The position adjusting bolt 11 is for finely adjusting the arrangement of the gradient coil 2. The support arm 13 is mounted on a base 15 via a shaft 14.

The vacuum vessel 3 is connected to a vacuum tube 6 and a vacuum pump 7 via an O-shaped ring 17. The inside of the vacuum vessel 3 is maintained at a vacuum by the suction operation of the vacuum pump 7. The degree of vacuum should be such that air propagation of vibration sound by the gradient magnetic field coil 2 can be cut off, and specifically, about several hundred pascals is sufficient. The sound insulation effect is expressed as follows. In the following equation, P1 is the degree of vacuum (Pascal) in the vacuum vessel 3.

S = 20 log ₁₀ (P1 / 1.01325 × 10 ⁵ ) (dB: dB) For example, if the degree of vacuum in the vacuum vessel 3 is 1000 Pascal, a sound insulation effect of about 40 dB can be obtained.

The vacuum vessel 3 has a coupler and a tube 18 for releasing the heat generated from the gradient coil 2 by water cooling.
Is connected.

A metal (bellows) 19 is provided at the bottom of the vacuum vessel 3 at a position corresponding to the shaft 14, thereby ensuring a required degree of vacuum and disassembly / assembly.

An RF coil 10 is fixedly arranged inside the cylindrical gradient magnetic field coil 2. This RF coil 10 is a whole-body (Whole Body) RF coil,
It is for transmitting a radio frequency (RF) magnetic field to the subject and receiving a magnetic resonance (MR) signal from the subject.

In the magnetic resonance imaging apparatus of this embodiment, as described above, the gradient magnetic field coil 2 is housed in the vacuum vessel 3, and this gradient magnetic field coil 2 is attached to the base 15 via a vibration absorbing device (damper). They are connected, and the propagation of solid vibration is suppressed.

FIG. 2 is a diagram showing terminal connections of cables inside and outside a vacuum vessel accommodating a gradient magnetic field coil and connection of cables to the gradient magnetic field coil inside the vacuum vessel.

A terminal 61 of a cable 60 extending from a power supply (not shown) is screwed to a shaft-shaped conductor 82 of the terminal support member 4. The conductor 82 is connected to a relay conductor 83 provided inside the terminal support member 4. As can be seen from the figure, the relay conductor portion 83 penetrates from the upper surface to the lower surface of the terminal support member 4 and partially projects. The terminal 9 of the cable 8 is connected to this protruding portion. The other terminal 84 of the cable 8 is connected to a terminal of the gradient coil 2.

With regard to the terminal connection structure of the cable 8 connecting the gradient magnetic field coil 2 and the terminal support member 4 inside the vacuum vessel 3, the magnetic resonance imaging apparatus of the present invention employs first and second embodiments described below. Has features.

First, a configuration relating to connection of the cable 8 to the terminal support member 4 will be described. As shown in FIG. 3, first, a cable terminal 9 is connected to one end of the cable 8 and hex-compressed. That is, by performing crimping by hexagonal compression in which pressure is applied from six directions, deformation of the cable terminal 9 can be suppressed as compared with normal crimping. Terminal support member 4
A screw hole S is formed in the relay conductor 83 provided in the cable terminal 9. The hexagonally compressed cable terminal 9 is formed in the screw hole S.
Screw directly. Thereby, the loosening of the screw due to the vibration of the cable 8 can be prevented. As described above, the cable 60 arranged outside the vacuum vessel 3 and the cable 8 arranged inside the vacuum vessel 3 are electrically connected as shown in FIG.

Next, a heat-shrinkable tube (thermosetting resin) 10 is placed over the terminal connection portion between the relay conductor portion 83 and the cable terminal 9 so as to completely cover the exposed portion of the conductor, and insulation treatment is performed. The silicon resin or the like 12 is potted into a groove formed in advance around the relay conductor portion 83 of No. 4. In this way, it is possible to perform appropriate and reliable insulation that is unlikely to cause a difference (manufacturing error) between workers during manufacturing.

Next, a configuration relating to connection of the cable 8 to the gradient coil 2 will be described. First, the cable terminal 84 crimped to the cable 8 is covered with the insulating material 13 as shown in FIG. The insulating material 13 is made of resin or the like, and the cable terminals 84 are exposed inside the cylindrical portion. This is connected to the gradient coil 2 via the spacer 14.
Is fixed to the terminal portion with a screw 15. Further, a silicon resin or the like 16 is potted on a contact portion between the insulating material 13 and the gradient magnetic field coil 2. In addition, silicon resin or the like 16 is potted so that the screw 15 is completely buried in the hollow portion of the cylinder of the insulating material 13. In this manner, similar to the connection of the cable terminal to the relay conductor portion 83, appropriate and reliable insulation that does not easily cause a difference (manufacturing error) between workers during manufacturing can be performed.

Further, for the silicone resin 16 or the like, by selecting a material having good adhesion to the insulating material 13 and high curability, the screw 15 can be prevented from being loosened due to vibration or the like.

As for the covering of the cable 8, it is preferable to select a material having a high adhesiveness to the potting agent and a material having excellent flexibility (flexibility) (for example, silicone resin). . As a result, not only the insulation property is improved, but also the vibration caused by Lorentz force generated in the cable can be reduced, and the sound insulation effect can be improved.

According to the present embodiment described above, the connection point between the relay conductor 83 of the terminal support member 4 and the terminal 9 of the cable 8 and the connection of the cable 8 to the gradient coil 2 in the vacuum vessel 3. Appropriate and reliable insulation can be provided for the location without causing a working error during manufacturing.

The present invention is not limited to the above-described embodiment, but can be implemented with various modifications.

For example, the present invention may be applied to a magnetic resonance imaging apparatus having a configuration in which a gradient magnetic field coil is not accommodated in a vacuum vessel or a configuration in which a vibration absorbing device is not provided in a gradient magnetic field coil. Further, it is needless to say that the static magnetic field generation method is not limited to the method using the superconducting coil, and the gradient magnetic field coil is not limited to only the active shield type gradient magnetic field coil.

[0037]

As described above, according to the present invention,
With respect to the connection of the cable to the gradient magnetic field coil, it is possible to provide a magnetic resonance imaging apparatus capable of obtaining appropriate and reliable insulation performance without causing an operation error during manufacturing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a magnetic resonance imaging apparatus according to an embodiment of the present invention when viewed from a side.

FIG. 2 is a diagram showing a terminal connection structure of a cable inside and outside a vacuum vessel accommodating a gradient magnetic field coil of the magnetic resonance imaging apparatus according to the embodiment.

FIG. 3 is a diagram showing a connection between a cable, a cable terminal, and a relay conductor portion 83 of a terminal support member 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Static magnetic field magnet 2 ... Gradient magnetic field coil 3 ... Vacuum container 4 ... Terminal support member 8, 60 ... Cable

Claims (6)

[Claims] 1. A magnetic resonance imaging apparatus in which a terminal of a cable connected to a gradient coil housed in a container is supported by terminal supporting means on a wall surface of the container, wherein the terminal is connected to the cable by hexagonal compression. A magnetic resonance imaging apparatus wherein the terminal is crimped, the terminal is screwed into a screw hole formed in advance in a conductor portion of the terminal supporting means, and the periphery of a connection portion of the terminal is insulated by insulating means. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the insulating unit is made of a thermosetting resin that covers the terminal. 3. The magnetic resonance imaging apparatus according to claim 2, wherein a gap between the thermosetting resin and the terminal supporting means is insulated by a second insulating means. 4. A magnetic resonance imaging apparatus in which a terminal of a cable connected to a gradient magnetic field coil housed in a container is supported by terminal support means on a wall surface of the container. Magnetic resonance imaging wherein at least a part is covered by a third insulating means, an exposed part of the terminal is connected to a terminal of the gradient coil, and the exposed part is insulated by a fourth insulating means. apparatus. 5. The magnetic resonance imaging apparatus according to claim 4, wherein a gap between the third insulating means and the gradient magnetic field coil is insulated by a fourth insulating means. 6. The cable according to claim 1, wherein the cable has such a flexibility that vibration caused by Lorentz force generated in the cable or vibration propagation from one end to the other end can be cut off. Or a magnetic resonance imaging apparatus.