JPH0257236A - Magnetic resonance diagnostic apparatus - Google Patents

Abstract

PURPOSE:To enhance the positional accuracy of an inclined magnetic field to an air-core main magnet without damaging the capacity absorbing the vibration phenomenon generated in the coil by mounting elastic structural bolts composed by bonding elastomers elastically deformed in the axial direction thereof upon the reception of load in the axial direction on the same axis. CONSTITUTION:The positional adjustment of an inclined magnetic field coil 3 in an up-and-down direction is performed by rotating an elastic structural bolt 9 and that of said coil 3 in a horizontal direction is performed by rotating the elastic structural bolts 10, 11 respectively forming screw pairs with respect to both of a T-block 8 and an L-block 7. The elastic structural bolt 10 is provided at several places symmetric centering around the central part of the inclined magnetic field coil 3 and tightened on one side thereof to push the inclined magnetic field coil 3 in the horizontal direction crossing the inner wall of an air-core main magnet 1 at a right angle. By tightening said bolts 10 on the other side thereof, said coil can be pushed back along the horizontal direction. That is, the inclined magnetic field coil 3 receives control stress on both sides thereof and the positional adjustment thereof is achieved accurately.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention collects magnetic resonance signals (hereinafter referred to as MR multiplied signals) from a subject placed in a static magnetic field and processes the signals. Regarding a magnetic resonance diagnostic apparatus that can provide image information for diagnosis that reflects at least one of the spin tightness and relaxation time of a specific atomic nucleus in a subject, in particular, it is possible to The present invention relates to an improvement in grooves for holding gradient magnetic field coils in a pedestal section to be formed.

(Prior Art) In general, this type of magnetic resonance diagnostic apparatus includes an air-core main magnet having an air-core structure so as to accommodate a subject, and a gradient magnetic field added to the static magnetic field generated from the air-core main magnet. A mount equipped with a gradient magnetic field coil that applies a superimposed magnetic field, and a transmitting/receiving coil that transmits a high frequency excitation pulse (hereinafter referred to as RF pulse) to a subject placed in a static magnetic field space and receives an MR multiplied signal from the subject. has a department.

Further, it has a signal processing section for collecting 1q MR multiplied signals in the mount section and reconstructing an image.

Like this! In a single-unit resonance diagnostic system, the gradient magnetic field coil is installed to provide positional information of the MR multiplied signal image, so high positional accuracy is required when or after the fixed arrangement with respect to the air-core main magnet. required.

On the other hand, the electromagnetic force acting between the static Ii field generated by the air-core main magnet and the current flowing through the gradient magnetic field coil generates vibrations in the gradient magnetic field coil itself. When a vibration phenomenon occurs in the gradient magnetic field coil itself due to the above electromagnetic force, if no treatment is applied to absorb this vibration reduction,
It is considered that the above-mentioned high accuracy cannot be maintained.

Therefore, in the past, for example, as shown in FIG.
These were tightened and fixed with bolts or the like with a rubber material 5 interposed therebetween.

However, if the rubber material is interposed and the tightening is fixed with bolts, etc., even if the vibration of the gradient magnetic field coil 3 can be absorbed, the positional accuracy of the gradient magnetic field coil 3 in the fixed arrangement state is high. I couldn't get it.

(Problem to be Solved by the Invention) That is, in the case of a conventional magnetic resonance diagnostic apparatus of this type, the rubber material 3 is used to absorb the vibration phenomenon of the gradient magnetic field coil 3. Even if the gradient magnetic field coil 3 is initially attached to the air-core main magnetic field 1, it is desirable to ensure high positional accuracy due to the presence of the rubber material 5.

Moreover, since the rubber material 5 is a viscoelastic body, when the load of the gradient magnetic field coil 3 is constantly applied, deformation force is generated in the rubber material 5 due to aging. As the shape deformation of the rubber material 5 progresses, the position of the gradient magnetic field coil 3 with respect to the air-core main magnet 1 gradually moves downward. Therefore, in the past, it was not possible to obtain a high position M resistance in the mounting state of the gradient magnetic field coil 3 with respect to the air-core main magnet, and there was a problem in that the position accuracy was significantly reduced, especially after a long WJ period had elapsed. .

The present invention has been made in view of the above problems, and its purpose is to improve the positional accuracy of the gradient magnetic field coil with respect to the air-core main magnet without impairing its ability to absorb vibration phenomena occurring in the gradient magnetic field coil. There is a particular thing.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a cylindrical housing coaxially installed along the inner wall of the air core main magnet, and a cylindrical housing installed coaxially along the inner wall of the air core main magnet. The gradient magnetic field coil is interposed between the cylindrical casing and a gradient magnetic field coil that applies a gradient magnetic field to the static magnetic field generated by the magnet, and the gradient magnetic field coil is connected to the cylindrical casing by means of bolts forming a pair of screws. On the other hand, there is a fixing device configured to be able to fix the tightening T-piece, an appropriate number of bolts are used for this fixing device, and an elastic body that is elastically deformed in the axial direction when receiving an axial load. The gist of the present invention is to include an elastic structural bolt coaxially coupled.

(Function) With the magnetic resonance diagnosis 1t7i device according to the present invention, the vibration phenomenon of the gradient magnetic field coil can be absorbed by the elastic structural bolt. In particular, if an elastic structural bolt with an integrally formed elastic body is used, the air core It becomes possible to obtain high positional accuracy in the mounting state of the gradient magnetic field coil with respect to the magnet.

(Embodiment) FIG. 1 is a configuration diagram showing the main parts of a magnetic resonance diagnostic apparatus according to an embodiment of the present invention, in which FIG. (B) is a front view of the pedestal section.

The magnetic resonance diagnostic apparatus of this embodiment includes a cylindrical housing 6 and an L
A fixing device consisting of a block 7 and a T-block 8, and an appropriate number of elastic structural bolts (9 in the figure) to be used for this fixing device.
．． 10.11).

The cylindrical housing 6 is positioned coaxially along the inner wall of the air-core main magnet 1 , and is connected to the air-core main magnet 1 by a support shaft 21 .
Fixed by.

The fixture consisting of the Shi block 7 and the T block 8 is interposed between a gradient magnetic field coil 3 that superimposes a gradient magnetic field on the static magnetic field formed by the air-core main magnet 1, and a cylindrical casing 6. The gradient magnetic field coil 3 can be fastened (=I) to the cylindrical casing 6 using bolts forming the shape.

Here, the L block 7 is integrally fixed to the inner peripheral surface of the cylindrical casing 6, and elastic structural bolts are connected to each other in the coil axis direction of the gradient magnetic field coil 3 and in the vertical direction perpendicular to the coil axis. It is something that will be done. An elastic structure bolt 11 is screwed together in the direction of the coil axis of the gradient magnetic field coil 3, and an elastic groove bolt 9 is screwed in a vertical direction perpendicular to the coil axis of the gradient magnetic field coil 3.

The T-block 8 is supported by an elastic member 15 interposed therebetween by an elastic structure bolt 9 that is screwed together with the L block 7, and an elastic structure bolt 10 is attached to the screw pair in the left-right direction perpendicular to the coil axis of the gradient magnetic field coil 3. has been done.

Therefore, the tightening angle of the elastic structure bolt 11 in the block 7 can be adjusted by adjusting the elastic body (same as the elastic body 15, but not shown for convenience of drawing) to apply a pressing force to the gradient magnetic field coil 3 in the coil axial direction. This can be used as an example.

Further, the tip of the elastic W4 bolt 10 on the T block 8 is pressed against the inner circumferential surface of the cylindrical casing 6 by adjusting the elastic body 15a to connect the gradient magnetic field coil 3 to the coil axis. The pressure horn can be biased in the right and left directions.

In addition, up to the above elasticity drawing, Pol 1-9. Same 10. Nuts 12 screwed into the same 11 respectively. Same 13. According to the same 14,
Although the elastic groove bolts 9 to 11 are tightened properly, it is also possible to adopt a structure in which the nuts 12 to 14 are omitted.

In addition, each elastic body 15° 15a of the elastic structural bolts 9 to 11
For example, a metal elastic body that is elastically deformed in the axial direction when subjected to an axial load is suitable.For example, various metal materials such as iron and copper can be used. The shape can also be devised to make it easier to deform.

In addition, after conducting various studies and experiments on suitable structures for the elastic structural bolts 9 to 11, we found that the following figures 3 to 5
As shown in the figures, it was concluded that it would be better to form a plurality of grooves on the side circumferential surface other than the part where the thread groove 16 is formed, and to use an elastic structure bolt with an integrated elastic body 15. reached.

To explain each of these preferred pieces in detail, the elastic structure bolt shown in FIG. and at least the elastic body 15
This is a bolt in which a hole 18 is formed along the axial direction on the axial center of the bolt, so that the elastic body 15 can be easily elastically deformed.

In the 4 elastic structure bolt shown in FIG. 4, a plurality of half-moon grooves 19 are formed on the side circumferential surface of the portion other than the portion where the thread groove 16 is formed, with the fulcrum position being shifted in the axial direction to the intersection H, and the elastic body 15 is integrally formed. In addition, a hole 18 is formed along the axial direction at least on the axial center of the elastic body 15.
This bolt is made to be easily elastically deformed.

The elastic structure bolt shown in Figure @5 has a plurality of semicircular grooves 19 formed deep to integrate the elastic body 15, and the formation of a hole along the axial direction on the axial center of the elastic body 15 is omitted. It's a bottle.

In any of the elastic structure bolts shown in FIGS. 3 to 5, since the elastic body 15 is integrated, the dimensional accuracy can be increased, and as described later, the gradient magnetic field coil 3 This is extremely useful for obtaining high positional accuracy in a fixed arrangement state.

In addition, when the end of the bolt is brought into contact with the inner peripheral surface of the cylindrical housing 6, such as the elastic structure bolt 10 used to connect the L block 7 and the T block 8, the end of the bolt may be made of nylon resin or the like. It is preferable to load a cap 20 made of synthetic resin.

In addition, in order to coaxially install the cylindrical casing 6 on the inner wall of the air-core main magnet 1 with a jig, the space between the cylindrical casing 6 and the air-core main magnet 1 is fixed via a support 21. (See Figure 1).

As mentioned above, in order to tighten and fix the cylindrical housing 6 and the gradient magnetic field coil 3, the L block 7° and the T bronze 989 are used.
Elastic structure bolts 9-11. Since other nuts 12 to 14 are used, the gradient magnetic field coil 3 relative to the cylindrical housing 6 is
The position adjustment, vibration absorption effect and position accuracy of the gradient magnetic field coil after the position adjustment are as follows.

The vertical position adjustment of the gradient magnetic field coil 3 is performed by rotating the elastic structure bolt 9. In this case, by making a polygonal hole such as a hexagon in the intrusion part of the elastic structure bolt 9 as shown in FIG. 2, it is easy to rotate the elastic structure bolt 9 by inserting a corresponding polygon spanner. can be done.

Next, by tightening the nut 12, the first loosening of the elastic structural bolt 9 is achieved.

The horizontal position adjustment of the gradient magnetic field coil 3 is carried out by rotating an elastic structural bolt 10 screwed into the T block 8 and an elastic structural bolt 11 screwed into the L block 7. In this case as well, the elastic structural bolt is rotated nine times using a polygonal spanner.

The elastic structural bolts 10 are installed at several locations centered around the center of the gradient magnetic field coil 3. On the other hand, by tightening any of the structural bolts 10, the gradient magnetic field coil 3 is It is pushed in the horizontal direction perpendicular to the inner wall of the magnet 1. Further, by tightening the elastic M4 bolt 10 on the other side, it can be pushed back along the horizontal direction. In the end, the gradient magnetic field coil 3 has an elastic structure Pol 1 to
Adjustment stress is applied by 10 from both sides of the air-core main magnet 1, one side and the other side in the horizontal direction orthogonal to the inner wall, thereby achieving position adjustment in the horizontal direction.

Further, the adjustment using the elastic grooved bolt 11 is performed in the same manner as that of the elastic structure bolt 10, but in this case, the gradient magnetic field coil 3 is moved in the horizontal direction along the inner wall of the air-core main magnet 1.

Under conditions in which the position of the gradient magnetic field coil 3 is adjusted as described above, the magnetic resonance clinic neck device of this embodiment is used for imaging a subject.

During imaging of this subject, when the gradient magnetic field field 3 vibrates due to the Ta field switching operation, each elastic body 15 of the elastic structure bolts 9 to 11 moves by a deformation amount on the order of 1/100III11. The elastic structure bolts 9 to 11 can ensure that the 1/b magnetic field coil 3 is fixed to the cylindrical housing 6. In particular, when an elastic guide bolt in which the elastic body 15 is integrated as explained in FIGS. 3 to 5 is used, the positional accuracy becomes higher.

Therefore, the phenomenon in which the vibrations of the gradient magnetic field coil 3 are propagated to other parts can be suppressed to the elastic structural bolts 9 to 12.

Furthermore, since each of the elastic bodies 15 of the elastic structure bolts 9 to 12 is made of metal, there is no need to consider deterioration due to aging as is the case with rubber.

As a result, according to each of the embodiments of the present invention described above, the gradient magnetic field coil can be held with high positional accuracy for a long period of time.

[Effects of the Invention] As explained above, the magnetic resonance diagnostic apparatus to which the present invention is applied has a cylindrical housing installed coaxially along the inner wall of the air-core main magnet and a gradient magnetic field coil. Since the bolts are tightened and fixed using elastic bolts, the elastic body of the elastic bolts can prevent the vibration phenomenon of the gradient magnetic field coil from propagating to other parts. especially,
If you use an elastic M4 bolt with an integrally formed elastic body,
It becomes possible to obtain high positional accuracy in the mounting state of the gradient coil with respect to the air-core main magnet, which is extremely useful from the viewpoint of maintenance and the like.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the main parts of a magnetic resonance diagnostic apparatus according to an embodiment of the present invention, FIG. 2 is a detailed explanatory diagram of the main parts of the magnetic resonance diagnostic apparatus, and FIGS. 3 and 4. 5 are perspective views of elastic structure bolts used in other embodiments of the present invention, and FIG. 6 is an explanatory view showing the mounting state of a conventional gradient magnetic field coil. 1... Air core main magnet 3... Tilt! i-field cocoil...cylindrical housing 7...1-block 8...
T block 9.10.11...Elastic borrowed bolt 12.13.14...Nut 15...Metal elastic body 16...Thread groove 17...Spiral groove 18...
・Hole 19... Half-moon groove 20... Buffer cap 8T block

Claims (8)

[Claims] (1) A cylindrical casing installed coaxially along the inner wall of the air-core main magnet, a gradient magnetic field coil that applies a gradient magnetic field superimposed on the static magnetic field generated by the air-core main magnet, and the cylindrical tube. a fixing device interposed between the body and the fixing device configured to be able to tighten and fix the gradient magnetic field coil to the cylindrical casing using bolts that form a pair of screw threads; and an appropriate number of bolts for the fixing device. 1. A magnetic resonance diagnostic apparatus comprising: an elastic bolt having an elastic structure coaxially connected with an elastic body that is elastically deformed in the axial direction when subjected to an axial load. (2) The fixing device is integrally fixed to the inner circumferential surface of the cylindrical casing, and the elastic structural bolts are respectively screwed in the coil axis direction of the gradient magnetic field coil and in the vertical direction perpendicular to the coil axis. The L block is supported via the elastic body by the elastic structure bolts screwed together in the vertical direction perpendicular to the coil axis in this L block, and is supported in the horizontal direction perpendicular to the coil axis of the gradient magnetic field coil. The elastic structure bolt is provided with a T block to which the elastic structure bolt is screwed together, and the coil is attached to the gradient magnetic field coil through the elastic body by adjusting the tightening of the elastic structure bolt which is screwed together in the coil axis direction in the L block. By applying a pressing force in the axial direction, and adjusting the tightening so that the tips of the elastic structure bolts screwed together in the left and right directions perpendicular to the coil axis in the T block are brought into pressure contact with the inner circumferential surface of the cylindrical casing. 2. The magnetic resonance diagnostic apparatus according to claim 1, wherein a pressing force is applied to the gradient magnetic field coil in a left-right direction perpendicular to the coil axis via an elastic body. (3) The magnetic resonance diagnostic apparatus according to claim 1, wherein the elastic body of the elastic structure bolt is a metal elastic body. (4) The elastic structural bolt has a structure in which the elastic body is integrated by forming a plurality of grooves on the side peripheral surface of a portion other than the thread groove forming portion. Magnetic resonance diagnostic equipment. (5) The elastic structural bolt has a structure in which the elastic body is integrated by forming a spiral groove multiple times on the side circumferential surface of a portion other than the thread groove forming portion. The magnetic resonance diagnostic device described. (6) The elastic structure bolt has a structure in which the elastic body is integrated by forming a plurality of grooves on the side circumferential surface other than the thread groove forming portion by alternately shifting the fulcrum position in the axial direction. The magnetic resonance diagnostic apparatus according to claim 1, characterized in that: (7) The elastic structure bolt has a structure in which the elastic body is integrated, and a hole is formed along the axial direction at least on the axial center of the elastic body.
The magnetic resonance diagnostic device described. (8) The magnetic resonance diagnostic apparatus according to claim 1, wherein the elastic structure bolt has a shock absorbing cap made of synthetic resin or the like mounted on the tip portion that comes into contact with the cylindrical casing or the like. .