JPH03212261A - Magnetic resonance image diagnostic device - Google Patents

Abstract

PURPOSE:To suppress the noise generated from a spool by installing a coil device on the spool having a frame structure which is constituted in the combination of a rod-shaped member and a ring-shaped member. CONSTITUTION:The spool 6 of an inclined magnetic field coil device is a spool having a cylindrical frame structure in combination of a rod-shaped member 6a and a ring- shaped member 6b. Though a vibration is generated on the spool 6 by the electromagnetic mechanical force generated on the coil, the vibration surface area of one member is small, and the conversion rate from vibration to sound, i.e., the sound irradiation efficiency is low, and the gradient magnetic field coil device having the less sound can be obtained, since the spool 6 has a frame structure and consists of rod-shaped or ring-shaped member 6a or 6b. Further, the sound irradiation efficiency is given with the influence of the magnitude of the vibration surface and the wave length of the sound, and on the vibration surface having the equal size, the irradiation efficiency of the high frequency sound having the shorter wave length is generally high. Though the vibration generated by the gradient magnetic field coil has the wide frequency components in Dc - several kHz, particularly the components in 200-2kHz are large, and when the irradiation efficiency of the sound of this components is to be lowered, it is effective to reduce the length of one side of the vibration surface to 10cm or less.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic resonance imaging diagnostic apparatus, and in particular, (1) a magnetic resonance imaging apparatus used for obtaining position information in a magnetic resonance imaging diagnostic apparatus. The present invention relates to a gradient magnetic field coil device.

[Prior Art] Fig. 4 shows the magnet part of a conventional superconducting magnetic resonance imaging system, which includes a superconducting main coil (2) housed in a cryostat (1) and a superconducting main coil (2) placed inside the main coil (2). It consists of gradient magnetic field coils (3), (4), and (5), a winding frame (6) to which the gradient magnetic field coils are attached, and a bed device (7). located on the device (7).

The gradient magnetic field coil device includes two pairs of saddle-shaped X-direction gradient magnetic field coils (3) arranged on the left and right, two pairs of saddle-shaped Y-direction gradient magnetic field coils (4) arranged above and below, and A pair of solenoid-shaped Z-direction gradient magnetic field coils (5) arranged
It is attached to a winding frame (6) made of a non-conductive material such as synthetic resin.

As shown in FIG. 2, a cylindrical winding frame (6) of the gradient magnetic field coil device is used (2) made of a non-conductive material.

In the magnetic resonance imaging diagnostic apparatus described above, in order to correct the strong DC magnetic field generated by the main coil (2), the gradient magnetic field coil (3) (
4) (5) is excited. At this time, the current flowing through the gradient magnetic field coil has a pulse-like waveform as shown in FIG. 3(a). For this purpose, a gradient magnetic field coil (3
) (4) In (5), electromagnetic mechanical force is generated as the current increases and decreases, causing the coil to vibrate, and this vibration to the winding frame (6
), generating a large noise from the surface of the reel, causing pain to the subject (8) located inside the reel.

The electromagnetic mechanical force generated in the gradient magnetic field coils (3), (4), and (5) has a waveform that is almost similar to the current waveform shown in FIG. 3(a). Therefore, the vibrations generated in the coil and the winding frame have the waveform shown in FIG. 3(b), and the noise generated by this vibration has frequency components in a wide range from DC to several kilohertz.

[Problems to be Solved by the Invention] (3) Conventional magnetic resonance imaging diagnostic equipment has a cylindrical winding frame and a large surface area, so the sound radiation efficiency is high, and the noise radiated from the winding frame can be transmitted to the patient. The problem was that it caused pain to people.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a magnetic resonance imaging diagnostic apparatus in which noise generated from the winding frame is reduced.

[Means for Solving the Problems] A magnetic resonance imaging diagnostic apparatus according to the present invention has a coil device attached to a winding frame having a framework structure constructed by combining a rod-shaped material and a ring-shaped material.

Further, in order to obtain a greater effect, the length of one side of the cross section of the rod-shaped material and the ring-shaped material is set to 10 cm or less.

[Function] The magnetic resonance imaging diagnostic apparatus according to the present invention has a frame structure made of rod-shaped and ring-shaped materials, so that
The sound radiation efficiency is reduced, and noise can be reduced to a low level (4).

Further, when the length of one side of the cross section of the frame material is set to 10 cm or less, the noise reduction effect is large, and it is effective in reducing vibration and noise.

[Embodiment of the invention] Fig. 1 shows a winding frame (6) of a gradient magnetic field coil device which is an embodiment of the present invention, and shows a cylindrical frame made of a combination of a rod-shaped material (6a) and a ring-shaped material (6b). It has a framework structure. The quantity of the rod-shaped material (6a) and the ring-shaped material (6b) arranged and supported in a cylindrical shape can be increased or decreased as necessary.

Further, the coils (3), (4), and (5) are wound or firmly attached and held on the frame structure winding frame (6) to complete the gradient magnetic field coil device.

That is, the radiation efficiency of sound from the surface of a vibrating object increases as the surface area becomes larger. That is, in the conventional gradient magnetic field coil device, the winding frame (6) has a cylindrical shape and the vibration surface is large, so the conversion efficiency from vibration to sound is high.
It was making a lot of noise.

(5) In the gradient magnetic field coil device according to the present invention, the electromagnetic mechanical force generated in the coil generates vibrations in the winding frame (6) of the same magnitude as the conventional one, but the winding frame (6) has a skeleton structure. and rod-shaped or ring-shaped materials (6a), (6b
), the vibration surface area of each member is small,
The conversion efficiency from vibration to sound, that is, the radiation efficiency of sound, is low.
A gradient magnetic field coil device with low noise can be obtained.

In addition, the radiation efficiency of sound is affected by the relationship between the size of the vibration surface and the wavelength of the sound, that is, the main frequency components. is common.

The vibrations generated by the gradient magnetic field coils have a wide frequency component from DC to several KH, but among them, 200 to 2 KH,
component is large, and in order to reduce the radiation efficiency of sound of this component, it is effective to make the length of one side of the vibrating surface 10 cm or less.

Furthermore, non-conductive materials are used for the winding frames of gradient magnetic field coil devices in order to prevent the generation of eddy currents, but with the frame structure of the winding frames, eddy currents flow (6) and a current circuit cannot be formed. Metal materials can be used in some parts of the range. - By way of example, the rod-shaped material (6a) in FIG. 1 can be a metallic material.

In this case, the rigidity and mass of the winding frame are increased, and vibration and noise of the winding frame can be further reduced.

[Effects of the Invention] As is clear from the above description, according to the present invention, the winding frame of the gradient magnetic field coil device of the magnetic resonance imaging diagnostic apparatus has a cylindrical frame structure, thereby reducing the sound radiation efficiency. This has the effect of significantly reducing noise and alleviating the pain of the patient located inside the reel.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a winding frame of a gradient magnetic field coil device of a magnetic resonance imaging diagnostic imaging apparatus according to an embodiment of the present invention, FIG. 2 is a configuration diagram showing a winding frame of a conventional gradient magnetic field coil device, and FIG. 4 is a waveform diagram showing current and vibration, and FIG. 4 is a configuration diagram showing a magnet portion of a conventional superconducting magnetic resonance imaging apparatus. (+)−... Taliostat, (2)... Main coil, (7) (3) (4) (5)... Gradient magnetic field coil, (6
)...Reeling frame, (6a) Rod-shaped material, (6b)... Ring-shaped material, (7)... Bed device, (8)... Subject. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A main coil that generates a DC magnetic field, a cylindrical frame that is placed within the DC magnetic field generated by this main coil and is made up of a plurality of rod-shaped materials and a ring-shaped material that arranges and supports the plurality of rod-shaped materials in a cylindrical shape. 1. A magnetic resonance imaging diagnostic apparatus comprising: a winding frame having a structure; and a coil device attached to the winding frame for correcting a DC magnetic field generated by the main coil. (2) The magnetic resonance imaging diagnostic apparatus according to claim 1, wherein the length of one side of the cross section of the rod-shaped material and the ring-shaped material constituting the winding frame is 10 cm or less.