JPH0370490B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a gradient magnetic field coil for a nuclear magnetic resonance imaging diagnostic apparatus, and more specifically, to a gradient magnetic field coil for use in a nuclear magnetic resonance imaging diagnostic apparatus. The present invention relates to gradient magnetic field coils used for this purpose.

[Conventional technology]

FIG. 3 shows the magnet part of a conventional superconducting nuclear magnetic resonance imaging system, which includes a superconducting main coil 2 housed in a cryostat 1, gradient magnetic field coils 3, 4, and 5 arranged inside the main coil 2. , a winding frame 6 and a bed device 7, and the subject 8 is positioned inside the winding frame 6. The gradient magnetic field coils include two pairs of saddle-shaped X-direction gradient magnetic field coils 3 placed on the left and right, two pairs of saddle-shaped Y-direction gradient magnetic field coils 4 placed above and below, and one pair placed front and back. It consists of a solenoid-shaped Z-direction gradient magnetic field coil 5, which is attached to a winding frame 6 made of a non-conductive material.

To attach the gradient magnetic field coil to the winding frame 6, as shown in FIG. 4, the winding frame 9 of the gradient magnetic field coil is firmly tied to the winding frame 6 with a band 10 such as a glass fiber tape. Alternatively, as shown in FIG. 5, the winding 9 is pressed and fixed to the winding frame 6 with bolts 12 via a holding plate 11.

In the nuclear magnetic resonance (NMR) image diagnostic apparatus described above, gradient magnetic field coils 3, 4, 5 are operated in a strong DC magnetic field generated by the main coil 2.
is excited. At this time, the current flowing through the gradient magnetic field coil has a pulse-like waveform as shown in FIG. 6a. For this purpose, the gradient magnetic field coil 3,
Electromagnetic mechanical force is generated at 4 and 5, and the coil vibrates as shown in FIG. 6b as the current increases or decreases.

The electromagnetic mechanical force generated in the gradient magnetic field coil is
The current waveform is almost similar to the current waveform shown in Figure a. Therefore, the frequency components of the mechanical force are distributed over a wide frequency range from DC to several KHz, and the vibration noise generated thereby also has similar frequency components.

[Problems to be Solved by the Invention] In the conventional gradient magnetic field coil, since the winding wire is directly fixed to the winding frame, the vibration of the coil is directly transmitted to the winding frame. For this reason, there was a problem in that the vibrations and the noise emitted from the reel caused pain to the subject located inside the reel.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a gradient magnetic field coil for a nuclear magnetic resonance imaging diagnostic apparatus in which vibration noise is reduced.

[Means to solve the problem]

A gradient magnetic field coil for a nuclear magnetic resonance imaging diagnostic apparatus according to the present invention is formed by fixing a coil to a winding frame via a mass body made of an anti-vibration material and a non-magnetic material.

[Effect]

This invention attenuates the high-frequency components to which the sense of hearing is sensitive among the wide range of frequency components of generated noise, and the vibration-proofing material attenuates the high-frequency components of the vibrations transmitted from the coil to the winding frame. .
In this case, the frequency component to be attenuated is the natural frequency determined by the mass of the coil and the spring constant of the vibration isolator.
Then, it is a frequency component of √2×fn or more, and by adding a vibration isolator and a mass body to the coil, the mass of the coil increases and the natural frequency of the coil decreases, resulting in a frequency range where there is a damping effect. becomes wider.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which a vibration-proof rubber 13 and a mass body 14 made of a non-magnetic material such as stainless steel are interposed on both sides of the winding 9.
The winding 9 is tightly bound to the winding frame 6 with a band 10.

FIG. 2 shows another embodiment of the present invention, in which a vibration-proof rubber 13 is also used on one side of the mass body 14, and a holding plate 11 and bolts 12 are used in place of the band 10.

With the above configuration, when the gradient magnetic field coil in which the winding 9 is vibration-isolated and supported from the winding frame 6 is excited and electromagnetic mechanical force is generated in the coil, the coil vibrates as in the conventional case, but it is transmitted to the winding frame 6. The high frequency components of the vibrations generated are attenuated, the vibrations of the winding frame 6 are reduced, and the noise radiated from the winding frame 6 can be significantly reduced.
Furthermore, in addition to the attenuation of high frequency components by the vibration isolating rubber 13, the mass body 14 lowers the natural frequency of the coil, thereby expanding the frequency range in which the damping effect can be achieved.

〔Effect of the invention〕

As explained above, according to the gradient magnetic field coil for nuclear magnetic resonance imaging diagnostic equipment of the present invention, vibration noise of the winding frame is significantly reduced by adding a vibration isolating material and a mass body to the winding. This has the effect of alleviating the pain of the subject located inside the reel.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of one embodiment of the present invention, FIG. 2 is a partial sectional view of another embodiment, and FIG. 3 is a partially cutaway perspective view of the main parts of a conventional nuclear magnetic resonance imaging diagnostic apparatus. , FIGS. 4 and 5 are partial cross-sectional views, respectively.
FIG. 6 is a waveform diagram of current and vibration. 1... Cryostat, 6... Winding frame, 9...
Winding wire, 13... Anti-vibration rubber (vibration isolating material), 14... Mass body. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A winding frame attached to a cryostat, and a winding wire wound and held on the winding frame, with vibration-proofing material and mass bodies made of non-magnetic materials disposed on both sides, respectively. A gradient magnetic field coil for a nuclear magnetic resonance imaging diagnostic apparatus, comprising: 2. The gradient magnetic field coil for a nuclear magnetic resonance imaging diagnostic apparatus according to claim 1, wherein the non-magnetic material is stainless steel.