JPH03244434A - Nuclear magnetism resonator device - Google Patents

Abstract

PURPOSE:To lessen the measuring error and accomplish good inspecting condition of a person inspected, by furnishing a vibration isolating structure between inclined mag. field coils and a support, wherein the structure is composed of a porous body equipped with holes and a moving body inserted in them with possibility of moving freely, and thereby reducing noise and vibration generated from the inclined mag. field coils. CONSTITUTION:Inclined mag. field coils 5, 6 are supported by an inclined mag. field coil (bobbin) 8 through a vibration isolating structure 10 consisting of a porous body 11 equipped with holes 12 and a moving body 13 inserted in the holes 12 movably. The porous body 11 is made of a material which can be treated as rigid normally, for example, non-magnetic metal such as Al, ceramics, plastics, and at least one is inserted in the hole 12 so that granular substance (moving body) 13 can move freely. In case an exciting force from the coils 5, 6 is applied from the oversurface of the vibration isolating structure 10, part of energy is given to the granular substance 13 existing in the hole 12 to be exhausted as kinetic energy, thermal energy, or friction energy with the porous body 11.

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. 61-279
As described in Japanese Patent No. 238, the windings of the gradient magnetic field coil are tied to the gradient magnetic field coil support with a band, with a vibration isolating rubber sandwiched between the coil and the gradient magnetic field coil support. When a gradient magnetic field coil whose winding is vibration-proofly supported from a support is excited and an electromagnetic mechanical force is generated in the coil, the coil vibrates, but the high frequency component of the vibration transmitted to the support is attenuated and the vibration of the support is The noise emitted from the support can be reduced.

With the above configuration, the vibration and noise of the support are reduced, and the pain of the person to be inspected who is located inside the support is alleviated.

[Problem to be solved by the invention]

In the conventional nuclear magnetic resonance apparatus described above, no consideration is given to the transmission of the low frequency component of the vibration of the coil to the support body or the vibration damping of the support body that radiates noise.
Noise reduction was insufficient, and there was still the problem of causing a great deal of anxiety to the subject.

The purpose of the present invention is to suppress the coil vibrations transmitted to the support, and to easily reduce the vibrations and noise generated by the vibrations of the gradient magnetic field coils, thereby reducing measurement errors and improving the test condition of the test subject. An object of the present invention is to provide an improved nuclear magnetic resonance apparatus.

[Means to solve the problem]

In order to achieve the above object, the present invention provides strong magnetic field generating means for supplying a high magnetic field within a cylindrical space, said gradient magnetic field generating means for supplying a gradient magnetic field distribution in the radial direction of said cylinder, and said gradient magnetic field generating means. and a support for fixing the cylindrical body to a predetermined position of the cylinder, the vibration isolation structure comprising a porous body having a hole and a moving body movably inserted into the hole. This is achieved by providing the gradient magnetic field coil and the gradient magnetic field coil support.

[Effect]

The vibration isolating structure is made of a porous material with granular material inserted into the holes, so if it is installed between the gradient magnetic field coil and the gradient magnetic field coil support, it will not cause vibrations generated by the gradient magnetic field coil. A portion of the vibration energy is absorbed by the particles within the holes. Therefore, the vibration generated by the gradient magnetic field coil is
This means that the magnetic field will not be transmitted to the gradient coil support.

〔Example〕

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

FIG. 6 is a side sectional view showing the basic structure of a nuclear magnetic resonance apparatus according to an embodiment of the present invention. FIG. 1 is a detailed diagram of the gradient magnetic field generator shown in FIG. 6 according to an embodiment of the present invention.

In this device, a static magnetic field of 0.5 to 4 Tesla in the axial direction is generated in the bore 2 of the central space by a static magnetic field generator on the part.

In the bore 2, gradient magnetic field coil systems are arranged that generate gradient magnetic fields in the X direction, the X direction, and two directions, respectively, with respect to the static magnetic field direction 2. In this gradient magnetic field coil system, the gradient magnetic field coils 5 and 6 are fastened and integrated by fastening fittings, and form a vibration-proofing structure consisting of a porous body with holes and a moving body movably inserted into the holes. It is supported by a gradient magnetic field coil (bobbin) 8 whose one end is fixed to a static magnetic field generator. Here, to avoid complexity, only the X and X-direction gradient coils are shown.

Both ends of the bobbin 8 are supported by support bolts 4 on the inner surface of the static magnetic field generator, thereby aligning the saddle-shaped coils 5 and 6 (ie, aligning the axis of the cylindrical body). Furthermore, an iron magnetic shielding body 7 weighing several tons is provided outside the static magnetic field generator in order to keep the leakage magnetic field space small.

When a pulse current for generating a gradient magnetic field is passed through the saddle-shaped gradient magnetic field coils 5 and 6, the electromagnetic force acting on the cylindrical portion of the coil is as follows.
According to Fleming's left-hand rule, when the direction of the static magnetic field is from left to right in Figure 6, the left-most upper coil circumference has a radial outward axis, and the lower coil circumferential area has a radial axis. Acts toward the center. Further, since current flows in the opposite direction to the left-side center circumferential portion of the coils 5 and 6, a load in the opposite direction acts on the coils 5 and 6. The action caused by the electromagnetic force described above attempts to deform the saddle-shaped coils 5 and 6, and if the coils 5 and 6 are deformed, the gradient magnetic field will be distorted and the image processing accuracy will be reduced. This will result in a decline.

However, in this example, since the gradient magnetic field coils 5 and 6 are firmly connected and have high rigidity, the deformation of the gradient magnetic field coils 5 and 6 due to this load is restrained, and the amount of displacement is kept very small. be able to. As a result, high-quality images can be obtained in three-dimensional space.

Here, when the electromagnetic force generated by the gradient magnetic field coils 5 and 6 is transmitted to the bobbin 8, the bobbin 8 vibrates and generates noise that is unpleasant for the person to be inspected. Therefore, in the present invention, since the gradient magnetic field coils 5 and 6 are fixed via the vibration isolation structure 1.0 consisting of a porous body having a hole in the bobbin 8 and a moving body movably inserted into the hole, A part of the energy of the electromagnetic force from the gradient magnetic field coils 5 and 6 is absorbed by the vibration isolation structure, so that the bobbin no longer vibrates, and the generation of noise can be considerably suppressed.

Here, the structure and function of the vibration isolation structure 10 used in this example will be explained with reference to FIG. 2.

As shown in FIG. 2, the porous body 11 is made of a material that can normally be treated as rigid, such as a non-magnetic metal such as aluminum, ceramics, or plastic.

A large number of pores 12 in the porous body 11 are provided by a method such as a machining-two-foaming method.

At least one granular body (moving body) 13 is inserted into the hole 12 so that it can move freely. With the structure described above, in the case shown in FIG. 1, the excitation force Fo from the gradient magnetic field coils 5 and 6 in this device is input to the upper surface of the vibration isolation structure 10. This side FO, that is, energy E.

is applied from the top surface, part of that energy is transferred to the hole 12.
is applied to the granules 13 present in the granules 13.

The energy given to the granular material 13 is consumed as kinetic energy, thermal energy, or frictional energy of the granular material 13 with the porous material 11. As a result, the energy Ex applied to the bobbin 8 located at the bottom in the figure becomes considerably smaller than the input energy EO.

As a result, the excitation force F when the vibration isolating structure 10 does not exist
Compared to the transmission of the excitation force Fo to the bobbin 8 when the vibration isolating structure 10 is provided, the transmission of the excitation force Fo to the bobbin 8 is considerably reduced, and the vibration of the bobbin 8 that generates noise can be suppressed considerably. Become. Further, vibrations transmitted to the bobbin 8 are suppressed by the sound absorbing material 9.

In the second embodiment, as shown in FIG. 2, a vibration isolation structure 10 is provided on the surface of the bobbin 8. The structure of the vibration isolating structure 10 in this case is the same as that described in the first embodiment (
The vibration isolating structure 10 used in this example absorbs and damps the vibration of the bobbin 8 without requiring rigidity. As long as it works, the porous body 1 is used as shown in Figure 3.
1 may be a material with low rigidity such as rubber.

When the vibration isolating structure 1o having such a structure is provided on the surface of the bobbin, the vibration energy of the bobbin is transferred to the kinetic energy and thermal energy of the granular bodies 13 in the vibration isolating structure, or to the porous body 11.
It is consumed as frictional energy with the material, suppressing noise generation. In this embodiment, an elastic body 20 is provided between the gradient magnetic field coils 5 and 6 and the bobbin 8.

As shown in FIG. 3, the third embodiment has a structure having both the vibration isolation structures used in the first embodiment and the second embodiment. According to this structure, higher effects can be obtained.

As a fourth embodiment, as shown in FIG. 4, the bobbin 8 has a vibration-proof structure. In this embodiment, the bobbin 8 has a structure in which, for example, a fibrous porous body 11 is provided with a large number of holes 12, at least one granular body 13 is inserted into the hole 12, and the granular body 13 is covered with an FRP resin or the like. It has become. As a result, a part of the vibration energy transmitted from the gradient magnetic field coil is consumed as kinetic energy or thermal energy of the granular material 13 in the bobbin 8, or as frictional energy with the porous material 11, thereby reducing the vibration of the bobbin itself. suppress. here,
In this embodiment, an elastic body 20 is provided between the gradient magnetic field coils 5 and 6 and the bobbin 8, and a sound absorbing material 9 is provided on the surface of the bobbin 8.
is provided.

In the fifth embodiment, as shown in FIG.
Set 0. The vibration isolating structure 10 at this time has the same structure as the vibration isolating structure 10 described in the second embodiment. In this case, the noise (air vibration energy) generated from the bobbin 8 is absorbed and attenuated by the action of the vibration isolation structure 10,
It is no longer transmitted to the space where the person to be inspected is located.

Several embodiments have been described here, but in the nuclear magnetic resonance apparatus of the present invention, by combining the embodiments described above, more effects can be produced, measurement errors can be reduced, and It is possible to reduce noise, which is a great mental burden for the person to be inspected.

〔Effect of the invention〕

According to the present invention, vibrations of the gradient coil support are absorbed;
Further, by attenuating the noise, it is possible to reduce the measurement error of the nuclear magnetic resonance apparatus, reduce noise, which is a serious problem for the examinee, and easily create an examination condition that allows the examinee to take the examination with peace of mind.

[Brief explanation of drawings]

FIG. 1 is a sectional view of main parts showing details of a gradient magnetic field generator applied to one embodiment of the present invention, and FIG. 2 is a main part showing details of a gradient magnetic field generator applied to a second embodiment. Partial sectional view,
FIG. 3 is a cross-sectional view of main parts showing details of the gradient magnetic field generator applied to the third embodiment, and FIG. 4 is a cross-sectional view of main parts showing details of the gradient magnetic field generator applied to the fourth embodiment. 5 is a partial side sectional view of the basic internal structure of the nuclear magnetic resonance apparatus according to the fifth embodiment, and FIG. 6 is the basic internal structure of the nuclear magnetic resonance apparatus of the present invention. FIG. 10... Vibration isolation structure, 11... Porous body, 13...
Granular Atsushizu Fuzufuzu 4th Zuzuzuzu 1ρ... Bosama Kibairin

Claims (1)

[Scope of Claims] 1. Strong magnetic field generating means for supplying a high magnetic field within the space of a cylinder; gradient magnetic field generating means for supplying a gradient magnetic field distribution in the radial direction of the cylinder; In a nuclear magnetic resonance apparatus, a vibration isolating structure consisting of a porous body having holes and a moving body movably inserted into the holes is connected to a gradient magnetic field coil. and the gradient magnetic field coil support.