JPH03162831A - Nuclear magnetic resonance device - Google Patents

Abstract

PURPOSE:To suppress oscillation and noise by providing sound-proof plates which are so installed as to shield the space disposed with gradient magnetic field generating means and can suppress the deformation by the signal from the outside and a controller which outputs the signals corresponding to the signals from an acoustic wave or oscillation detecting means to the sound-proof plates according to the above-mentioned signals into a cylindrical space. CONSTITUTION:The sound-proof members 5 disposed apart a specified spacing 16 from the gradient magnetic field coils 11, 12 in the cylindrical space where a person to be inspected exists have the function to suppress the deformation by the control signal 10 from the controller 8 and the function to sense the deformation in a part or over the entire part of the sound- proof members themselves. These members are constructed by sticking plural sheets of, for example, the piezoelectric films which expand and contract in the intra-surface direction when impressed with voltages. When the sound-proof members 5 are deformed in the out-of-the surface direction in a part or over the entire part thereof by the acoustic waves of the noise generated by the oscillation of a bobbin 15, the sound-proof members 5 are forced to be deformed in a part or over the entire part thereof in the direction opposite from this deformation direction by the adequate control input 10 from the controller 8. The deformation of the sound-proof plates in the out-of-the surface direction is suppressed in this way and the transmission of the noise to the space where the person to be inspected exists is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure for suppressing vibrations and noise generated by gradient magnetic field generating coils in a nuclear magnetic resonance apparatus.

[Conventional technology]

In the conventional medical nuclear magnetic resonance apparatus, Japanese Patent Application Laid-Open No. 63-246
As described in Publication No. 146, a cylindrical vacuum container is placed inside a cylindrical static magnetic field generator. A gradient magnetic field generating coil is housed within this vacuum container via a support.

Further, the vacuum container has first and second cylindrical bodies having different diameters, and both axial ends of the cylindrical bodies are each sealed by a tubular sealing mechanism. A pipe inserted into the vacuum container 12 is led out from this one sealing mechanism, and by operating the pipe, the inside of the container can be brought into a vacuum state. With this configuration, the vibrations of the gradient magnetic field coils generated during operation and the noise thereof are not transmitted to the outside of the container, and the subjects placed inside the container do not hear the noise.

[Problem to be solved by the invention]

In the above-mentioned conventional nuclear magnetic resonance apparatus, no consideration was given to the placement of a large coil called a gradient magnetic field generation coil in a vacuum container, which made the actual processing difficult and the system large. There is a problem in that it gives people a great sense of pressure.

An object of the present invention is to provide a nuclear magnetic resonance apparatus that suppresses vibrations and noise generated by gradient magnetic field coils and improves the examination condition of the examinee without giving the examinee a feeling of pressure. [Means for Solving the Problems] In order to achieve the above object, the present invention provides strong magnetic field generating means for supplying a uniform high magnetic field to a cylindrical space, and supplying a gradient magnetic field distribution in the radial direction within the cylindrical space. In a nuclear magnetic resonance apparatus comprising a gradient magnetic field generating means and a support for fixing the gradient magnetic field generating means at a predetermined position within the cylindrical space, a space for arranging the gradient magnetic field generating means is blocked in the cylindrical space. A soundproof board (2 is a soundproof sheet) installed in such a manner that the deformation can be suppressed by an external signal, and a corresponding signal is output to the soundproof board or soundproof sheet by a signal from a sound wave or vibration detection means. It is equipped with a control device to

The soundproof board or sheet also serves as a means for detecting sound waves or vibrations. Alternatively, a sound wave or vibration detection means is provided within the cylindrical space to detect sound waves and output the signals. [Function] In the present invention, the control device operates so that the soundproof board or the soundproof sheet is not deformed. As a result, the soundproof plate operates to prevent the noise generated by the vibration of the gradient magnetic field coil from being transmitted to the space where the test subject is located when the device is in operation. Therefore, the noise that the test subject hears is suppressed, and the test subject's discomfort and anxiety are reduced. Further, the sound wave or vibration detection means operates to sense sound waves or vibrations and output the signal to the control device.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a side sectional view showing the structure of a nuclear magnetic resonance apparatus according to a first embodiment of the present invention. Figure 2 is a cross-sectional view of the gradient magnetic field coil system in Figure 1. A cylindrical static magnetic field generator 1 generates a static magnetic field of 0.5 to 4 Tesla in the axial direction within the bore 2 of the central space. A gradient magnetic field coil system is arranged in the bore 2 to generate gradient magnetic fields in the X direction, the y direction, and two directions, respectively, with respect to the static magnetic field direction 2. The gradient magnetic field coils 11 and 12 are fastened with fastening metal fittings and supported by a bobbin 5 whose integrated end is fixed. Here, to avoid complexity, only the gradient coils in the X and Y directions are shown. When a pulse current for generating a gradient magnetic field is passed through the saddle-shaped gradient magnetic field coils 11 and 12, the electromagnetic force acting on the circumference of the coil follows Fleming's left-hand rule, and the direction of the static magnetic field is from left to right in the diagram. At some point, the force acts radially outward on the upper left coil circumference, and acts radially toward the center of the axis on the lower coil circumference. Furthermore, since current flows in the opposite direction to the left-side center circumferential portion of the coils 11 and 12, a load in the opposite direction acts on the coils 11 and 12. This load can be reduced because the gradient magnetic field coils 1l and 12 are firmly connected and have high rigidity, and because it is absorbed by the large number of elastic bodies 14.

However, in this case, the load that could not be absorbed is the bobbin 15.
vibrates and generates noise. Although the generation of this noise is suppressed by the sound absorbing material 13 such as urethane, glass wool, maltbrane, etc. attached to the inner and outer peripheral surfaces of the bobbin 15, the sound absorption of the noise heard by the testee is insufficient. Therefore, in the present invention, a certain space l6 is provided from the gradient magnetic field coil system in the cylindrical space where the test subject is located, so that the gradient magnetic field coil system placement space and the space where the test subject is located are completely separated and cut off. , a soundproof board or soundproof sheet 5 that can suppress deformation due to external signals is installed. Hereinafter, the soundproofing board or soundproofing sheet will be referred to as a soundproofing member. At this time, an iron magnetic shield 6 is installed outside the static magnetic field generator to suppress the leakage magnetic field space.
Separation and isolation are accomplished by fixing the

Here, the soundproofing member 5 receives a control signal 10 from the control device 8.
It has the function of suppressing deformation due to the soundproofing member itself, and the function of sensing the deformation of a part of the soundproofing member itself or the entirety. It has a bonded structure and can handle deformation in the out-of-plane direction. The operation of this structure will be described below. If a part or the whole of the soundproof plate 5 is to be deformed in an out-of-plane direction due to the sound waves of the noise generated by the vibration of the bobbin 15, the soundproof member 5 can be partially deformed by an appropriate control force 10 from the control device 8. Attempts to deform a part or the whole in the opposite direction to its deformation direction. As a result, deformation of the soundproof board in the out-of-plane direction is suppressed, and the transmission of noise to the space where the test subject is located is suppressed. Therefore, the noise that the test subject hears is reduced. In this embodiment, as described above, the soundproofing member 5 has a function of sensing deformation of a part or the whole of the soundproofing member 5 itself, and is combined with the control device 8 to form a closed loop feedback control system.

FIG. 3 is a block diagram of the control device 8 applied to this embodiment. The control device 8 in this embodiment includes an amplifier 8a, a gain adjuster 8b, a voltage generator 8c, and a voltage amplifier 8d. In operation, first, a minute detection signal 9 from the soundproofing member due to the deformation of the soundproofing member is amplified by the amplifier 8a. Next, the detection signal is multiplied by an appropriate control gain by the gain adjuster 8b, and a corresponding voltage is generated by the voltage generator 8C. Further, it is amplified by the voltage amplifier 8d and finally applied to the soundproofing member as a control signal to control the out-of-plane deformation of the soundproofing member 5.

Next, a second embodiment will be described with reference to FIG. FIG. 4 is a partial side sectional view showing the structure of the nuclear magnetic resonance apparatus according to this embodiment. This embodiment differs from the first embodiment in that the soundproofing member 5 does not have the function of sensing its own deformation, but has at least l or a plurality of e.g. This is a case where acoustic sensors 17a and 17b are installed, and detection signals 9a,
9b is input to the control device 8. This embodiment differs from the first embodiment only in the sound wave or vibration detection means, but the operation and effects after sound wave or vibration detection are the same as in the first embodiment. Next, a third embodiment will be explained with reference to FIG. FIG. 5 is a partial side sectional view showing the structure of the nuclear magnetic resonance apparatus according to this embodiment.

Similar to the second embodiment, this embodiment is also a case in which the soundproofing member 5 does not have the function of sensing its own deformation. Therefore, as a sound wave or vibration detection means, at least one piece having a function of sensing the deformation of the sound wave proofing 5, or
For example, a plurality of vibration sensors 18 are installed on the soundproof board 5.
In this embodiment as well, the operation and effects after sound waves or vibrations are detected are similar to those in the first embodiment.

〔Effect of the invention〕

According to the present invention, it is possible to suppress the noise generated by the vibration of the gradient magnetic field coil during the test from being transmitted to the space where the test subject is located. In addition, since the nuclear magnetic resonance apparatus does not increase in size when the suppression is performed, the examinee can undergo the examination without feeling pressured or uncomfortable.

[Brief explanation of the drawing]

Fig. I is a partial side sectional view of the internal structure of a nuclear magnetic resonance apparatus according to an embodiment of the present invention, and Fig. 2 is a sectional view of main parts showing details of the gradient magnetic field coil system applied to the embodiment of Fig. 1. , FIG. 3 is a block diagram of a control device applied to an embodiment of the present invention, FIG. 4 is a partial side sectional view of the internal structure of a nuclear magnetic resonance apparatus according to a second embodiment of the present invention, and FIG. 5 is a block diagram of a control device applied to an embodiment of the present invention. FIG. 7 is a partial side sectional view of the internal structure of a nuclear magnetic resonance apparatus according to a third embodiment of the present invention. 5... Soundproof board, 8... Control device, 9, 9a, 9b.
...Detection signal, 10...Control signal, 17a, 17b.
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Claims (1)

[Scope of Claims] 1. Strong magnetic field generating means for supplying a uniform high magnetic field to a cylindrical space, gradient magnetic field generating means for supplying a gradient magnetic field distribution in the radial direction within the cylindrical space, and the gradient magnetic field generating means A nuclear magnetic resonance apparatus comprising: a support fixed at a predetermined position within the cylindrical space; A nuclear magnetic resonance apparatus comprising: a soundproof plate that can suppress deformation; and a control device that outputs a signal to the soundproof plate according to a signal from a sound wave or vibration detection means. 2. The nuclear magnetic resonance apparatus according to claim 1, wherein the soundproof plate also serves as a sound wave or vibration detection means. 3. The nuclear magnetic resonance apparatus according to claim 1, further comprising sound wave or vibration detection means for detecting sound waves in the cylindrical space and outputting the signals.