JPH0382448A - Inclined magnetic field coil of mri - Google Patents

Abstract

PURPOSE:To reduce substantially noises in excitation by disposing a coil with a visco-elastic body interposed between the coil and a bobbin, while adhering a tape made rigid along with the passage of time to the upper surface of the coil through the visco-elastic body. CONSTITUTION:An axis X direction coil 14 is coiled around an inclined magnetic field coil on a bobbin 17 through a visco-elastic body 18, and a tape 44 is disposed on the upper surface of the axis X direction coil through the visco-elastic body. The tape 44 having a property made rigid along with the passage of time is adapted to unify the axis X direction coil, bobbin and visco-elastic body together with the tape. This constitution, not limited to the axis X direction coil, applies to axis Y direction and axis Z direction coils The coil has the visco-elastic body disposed on the opposite side of the bobbin side so that vibration can be absorbed and noises can be substantially reduced with a restricted type antivibration construction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gradient magnetic field coil for magnetic resonance imaging (hereinafter referred to as MRI).

[Conventional technology]

In MRI, there is a gradient magnetic field coil that has a function of specifying a tomographic position when obtaining a tomographic image of a subject.

This gradient magnetic field coil has an X-axis coil, a Y-axis coil, and an X-axis coil wound around a non-conductive cylindrical bobbin (for example, made of glass fiber reinforced plastic). In order to reduce the noise generated when the coils are excited, a cushioning material such as a rubber plate is interposed between each coil and the bobbin, or each coil is tied with cloth tape and fixed to the bobbin. It has been known.

[Problem to be solved by the invention]

However, with the conventional technology, the noise generated when each coil is excited has not been sufficiently reduced, and the psychological anxiety of the patient housed within the magnet cannot be ignored.

That is, the triaxial gradient magnetic field coils are opened and opened to provide position information to the NMR signal, and the gradient coils are opened to provide position information to the NMR signal, and the voltage is changed from zero ampere (A) to 20 ampere (A) in a short period of time, e.g., 1 millisecond (ms).
A large current of ~100A is rapidly applied, lasting several ms, and 1 m
s to rapidly reduce the current to zero, and several meters independently in three axial directions.
The above operation is repeated at intervals of s. Each coil, which suddenly changes the current in a pulsed manner, is placed in a static magnetic field, so each coil vibrates and hits the bobbin, which is made of glass fiber reinforced plastic, creating a large amount of noise.

For example, for a coil with a diameter of approximately 700 mm in a static magnetic field of H0 = 0.5 Tesla (T), when Hac =: 0, 3 Gauss (G)/911, at a position 1 m from magnet 1, 60 ~
If e Hoct H+s, which generates 70 horns of noise, increases, the noise will increase rapidly, and at H,=1.5T, the noise will exceed 100 horns.

Therefore, the present invention has been made based on such circumstances, and its object is to provide a gradient magnetic field coil for MRI that can significantly reduce noise during excitation.

[Means to solve the problem]

In order to achieve such an object, the present invention provides an MRI gradient magnetic field coil configured by winding a coil around a bobbin, wherein the coil has a viscoelastic body interposed between it and the bobbin surface, In addition, a tape is attached to the top surface via a viscoelastic material.

The tape has a property of becoming rigid over time.

Further, in an MRI gradient magnetic field coil configured by winding a coil around a bobbin, the coil is surrounded by a rigid body via a viscoelastic body, and the rigid body has a viscoelastic body between it and the bobbin surface. A tape is attached to the upper surface via a viscoelastic material, and the tape has a property of becoming rigid over time.

Further, in an MRI gradient magnetic field coil configured by winding a coil around a bobbin, the coil is surrounded by a viscoelastic body, and the coil surrounded by the viscoelastic body has a gap between the coil and the bobbin surface. A rigid body and a viscoelastic body are interposed in this order from the coil side, and the upper surface of the coil surrounded by the viscoelastic body is laminated with a rigid body, a viscoelastic body, and a tape that has a property of becoming rigid over time. The rigid body on the coil surrounded by the viscoelastic body extends along the side surface of the coil surrounded by the viscoelastic body, and further extends in a bent manner parallel to the bobbin surface. A vibration absorber is interposed between the existing part and the bobbin.

[Effect]

The MRI gradient magnetic field coil configured in this manner is arranged with a viscoelastic body interposed between it and the bobbin, and a tape that becomes rigid over time is attached to the upper surface of the coil through the viscoelastic body. There is. As a result, the coil and the viscoelastic body are fixed to the bobbin in an integrated state.

Therefore, the so-called constrained vibration damping structure can significantly reduce the noise caused by the vibration of the coil.

In this integrated structure, since the coil is provided with a viscoelastic body at least on the bobbin side and on the opposite side, vibration absorption in the viscoelastic body can be achieved, and this is similar to the constrained vibration damping structure described above. Combined, the effect of noise reduction becomes greater.

〔Example〕

An embodiment of an MRI gradient magnetic field coil according to the present invention will be described below.

First, FIG. 2 is a schematic diagram showing the entire MRI to which the gradient magnetic field is applied. In the figure, there is a magnet 1, the inside of which forms a static magnetic field space. The subject 3 mounted on the bed 13 is accommodated within this static magnetic field space. Further, a gradient magnetic field coil 7 is disposed within the magnet 1 surrounding the subject 3, and this gradient magnetic field coil 7 is excited by a gradient magnetic field power supply 6. An irradiation coil 5 is arranged inside the gradient magnetic field coil 7 and surrounding the subject 3, and the irradiation coil 5 is excited by the transmitter 4. The irradiation coil 5 is designed to produce a nuclear magnetic resonance phenomenon at a predetermined location of the subject specified by the excitation of the gradient magnetic field coil 7, thereby generating a so-called NMR signal.

This NMR signal includes position information and is received by the receiving coil 8. The receiving coil 8 is arranged inside the irradiation coil 5 and surrounding the subject 3. The signal from the receiving coil 8 is sent to a receiver 9
is sent to the display 1 via the data processing device 11.
2, the image is displayed.

Note that the gradient magnetic field power supply 6, the transmitter 4, and the receiver 9
are each controlled and driven by the sequence control section 10.

FIGS. 3(a) and 3(b) are explanatory diagrams showing details of the gradient magnetic field coil 7. FIG. In the same figure (a), there is a bobbin 17, and an X-axis direction coil 14 is provided on the outer peripheral surface of this bobbin F.
．． 14', a Y-axis coil 15.15' and an X-axis coil 16.16' are wound. The X-axis direction coil 16.16' is constructed by going around the bobbin 17, and the X-axis direction coils 14, 14' and the Y-direction coil 15.15' each have a saddle shape and are arranged on the surface of the bobbin 17. It is located.

The X-axis direction coil 14.14' and the Y-axis direction coil 15.15' are formed with a spread of 120@ from the central axis as shown in FIG. 3(b), and the X-axis direction coil 14°14' and Y-axis direction coil 15.
15' are arranged in an overlapping state at a portion corresponding to the spread of 30''.

Note that current flows through each of the axial coils independently, as shown in Figures 2 (a,) and (b).
The arrows indicate the direction of the current at any instant.

FIG. 1 further shows details of the X-axis direction coil 14 in FIG. 3 above. Around the bobbin 17, an X-axis coil 14 is connected via a viscoelastic body 18.
A tape 44 is placed on the upper surface of the X-axis direction coil 14 with a viscoelastic body 18 interposed therebetween. This tape 44.

This tape 44 has the property of becoming rigid over time, and the X-axis direction coil 14 including this tape 44. The bobbin 17 and the viscoelastic body 18 are integrated.

Such a configuration is not limited to the X-axis direction coil 14, but is the same for the other Y-axis direction coils 15 and the X-axis direction coils 16.

FIG. 4 is a configuration diagram showing another embodiment of the MRI gradient magnetic field coil according to the present invention. In the figure, an X-axis direction coil 14 enclosed by a rigid body 32 is wound around a surface of a bobbin 17 with a viscoelastic body 28 interposed therebetween. That is, the circumference of the X-axis direction coil 14 is covered with a viscoelastic body 18, 30, and the bottom part is covered with a rigid body 27, and the side surface is also covered from the top, and both ends thereof extend along the side surface. It is bent and extends parallel to the bobbin 17 surface at a predetermined distance from the bobbin 17 surface. A vibration absorber (Iridump grommet Isodump mount,
C-1002, EAR Corporation, USA) 39 is interposed. In addition, a viscoelastic body 18 is connected to the top of the rigid body 32, and
A tape 44 is applied which has a similar function to that shown in FIG. Furthermore, the bobbin 17 has two layers of viscoelastic material 2.
It has a 5M structure that incorporates 5.26.

Such a configuration also has the effect that vibration transmitted from the X-axis direction coil 14 to the rigid body 32 is absorbed by the vibration absorber 39 having a relatively large area that contacts the rigid body 32.

FIG. 6 is a block diagram showing another embodiment according to the present invention. The structure is almost the same as that shown in FIG. 5, but the structure different from that shown in FIG. It has a configuration in which a U-shaped rigid body 32 is fitted. Further, a tape 44 having the same function as that shown in FIG. 3 is attached to the upper surface of the rigid body 32 via the viscoelastic body 18. In addition, in FIG. 4, the bobbin 17 has also been devised, and a rigid body 31 is attached to the inner circumferential surface of the bobbin 17 via a viscoelastic body 29.

With this configuration, the X-axis direction coil 14 is integrated with the bobbin by the tape 44, resulting in a constrained vibration damping structure, and the area around the X-axis direction coil 14 is made of a viscoelastic body or a rigid body. Because it is covered, noise caused by vibration can be significantly reduced.

FIG. 5 is a block diagram showing another embodiment according to the present invention. In the figure, a viscoelastic body 28.
The X-axis coil 14 is arranged via the rigid body 27 and the viscoelastic body 18, and the top and side surfaces of the X-axis coil 14 are covered by the viscoelastic body 18. Further, a rigid body 32 is disposed on the upper surface of the X-axis direction coil 14 via the viscoelastic body 18.

By adopting such a configuration, reliability of integration is increased, and a more effective restraint type vibration damping structure can be obtained.

FIG. 7 is a configuration diagram showing still another embodiment of the present invention. This figure has almost the same configuration as FIG. 5. The difference in configuration from FIG. 5 is that the rigid body 27 and viscoelastic body 28 directly below the X-axis direction coil 14 shown in FIG. 5 do not exist.

Since vibration absorption by the vibration absorber 39 is large, unnecessary materials are eliminated within an allowable range in consideration of manufacturing effects and the like.

In addition, the negative effect of eliminating the above material is bobbin 17.
This can also be prevented by attaching the rigid body 31 via the viscoelastic body 29 to the inner circumferential surface of the .

FIG. 8 is a configuration diagram showing another embodiment according to the present invention. The configuration is almost the same as that in FIG. 7, and the difference from FIG. 7 is that a rigid body 32 is placed at the bottom of the X-axis coil 14, and this rigid body 32 is placed at the top and side of the X-axis coil 14. The coil 14 is integrated with the rigid body 32 and encloses the X-axis coil 14 therein.

With such a configuration, vibrations from the bottom of the X-axis direction coil 14 are transmitted through the rigid body 32 and easily absorbed by the vibration absorber 39.

FIG. 9 is a block diagram showing another embodiment according to the present invention. The configuration is similar to that in FIG. 8, and the difference from FIG. 8 is that tapes 44 that integrate the X-axis coil 14 with the bobbin 17 are formed on each upper part of the rigid body 32 with a vibration absorber 39 interposed therebetween. It's in being.

〔Effect of the invention〕

As is clear from the above explanation, MR according to the present invention
According to the gradient magnetic field coil I, the coil is arranged with a viscoelastic body interposed between it and the bobbin, and a tape that becomes rigid over time is attached to the upper surface of the coil through the viscoelastic body. . As a result, the coil and the viscoelastic body are fixed to the bobbin in an integrated state.

Therefore, the so-called constrained vibration damping structure can significantly reduce the noise caused by the vibration of the coil.

In this integrated structure, since the coil is provided with a viscoelastic body at least on the bobbin side and on the opposite side, vibration absorption in the viscoelastic body can be achieved, and this is similar to the constrained vibration damping structure described above. Combined, the effect of noise reduction becomes greater.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is an MR
3 is a block diagram schematically showing the gradient magnetic field coil, and FIGS. 4 to 9 are block diagrams showing other embodiments of the present invention. 14... X-axis direction coil, 18, 28, 29, 30° 31... Viscoelastic body, 17... Bobbin, 27.31,
32...Rigid plate, 39...Vibration absorber. 44...A tape that becomes rigid over time. No. 1 ink map (Bobbin Uchiko 9 Reno Hayabusa 1, Stone 1 Stone 2, Shutake purchase space 3° Sode ridge 8: Receiving letter Kojiru 9, Fee f Genki 6: Tilt t 4 stone factory electric; Freeze 7: Iyu t + ζ Namihanawa coil 12 Te °zufulge 13:'\'・nd 1!3 Figure (0) Figure 4 Figure Figure Figure Figure Figure 8 Figure 8

Claims (5)

[Claims] 1. In an MRI gradient magnetic field coil constructed by winding a coil around a bobbin, the coil has a viscoelastic body interposed between it and the bobbin surface, and a tape is adhered to the upper surface via the viscoelastic body. MRI gradient magnetic field coil, characterized in that the tape has a property of becoming rigid over time. 2. The coil has a viscoelastic body interposed between it and the bobbin surface, and a tape is attached to the upper surface of the coil through the viscoelastic body, and the tape has a gradient magnetic field coil that becomes rigid over time. M characterized by having
R.I. 3. In an MRI gradient magnetic field coil configured by winding a coil around a bobbin, the coil is surrounded by a rigid body with a viscoelastic body in between, and the rigid body has a viscoelastic body interposed between it and the bobbin surface. 1. A gradient magnetic field coil for MRI, characterized in that a tape is adhered to the upper surface via a viscoelastic material, and the tape has a property of becoming rigid over time. 4. The coil is surrounded by a rigid body with a viscoelastic body in between, and the rigid body has a viscoelastic body interposed between it and the bobbin surface, and a tape is adhered to the upper surface of the coil through the viscoelastic body. Further, the MRI is characterized in that the tape includes a gradient magnetic field coil having a property of becoming rigid over time. 5. In an MRI gradient magnetic field coil configured by winding a coil around a bobbin, the coil is surrounded by a viscoelastic body, and the coil surrounded by the viscoelastic body is placed between the bobbin surface and the coil. A rigid body and a viscoelastic body are interposed sequentially from the side, and the upper surface of the coil surrounded by the viscoelastic body is laminated with a rigid body, a viscoelastic body, and a tape that has a property of becoming rigid over time. The rigid body on the coil surrounded by the elastic body extends along the side surface of the coil surrounded by the viscoelastic body, and further extends in a bent manner parallel to the bobbin surface, and is connected to the extending portion. An MRI gradient magnetic field coil characterized in that a vibration absorber is interposed between the coil and the bobbin.