JP2002200055A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus which can effectively suppress noise generated from an inclined magnetic field coil, etc. SOLUTION: This magnetic resonance imaging apparatus is equipped with a static magnetic field magnet, an inclined magnetic field coil 102, a high frequency coil 103, a closed vessel 133 to house the inclined magnetic field coil 102. The closed vessel 133 is connected to a vessel 116 for the static magnetic field magnet via a ring shape flange 106.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging (MRI) apparatus for medical diagnosis and a sound insulation method thereof, and in particular, significantly reduces noise generated due to driving of a gradient magnetic field coil. The present invention relates to a silent type magnetic resonance imaging apparatus.

[0002]

2. Description of the Related Art A magnetic resonance imaging apparatus for medical diagnosis is an imaging apparatus based on a magnetic resonance phenomenon of nuclear spins in a subject, and is non-invasive and X-ray like an X-ray apparatus.
An image of the inside of the subject can be obtained without any radiation exposure. For this reason, its usefulness has been demonstrated in clinical settings in recent years.

Generally, a magnetic resonance imaging apparatus for obtaining an MR image includes a gantry for inserting a subject into an imaging space, and a main body of the apparatus cooperating with the gantry.
The gantry has a static magnetic field magnet such as a superconducting magnet for generating a static magnetic field in the diagnostic space, a gradient magnetic field coil for generating a linear gradient magnetic field superimposed on the static magnetic field, and an RF for transmitting a high frequency signal and receiving an MR signal. It has a coil. During imaging, the static magnetic field magnet, the gradient coil, and the RF coil are driven in accordance with a desired pulse sequence. In other words, according to the pulse sequence,
A linear gradient magnetic field in each of the x, y, and z axes is superimposed on the subject placed in the static magnetic field, and the nuclear spin of the subject is magnetically excited by a high frequency signal of the Larmor frequency. A magnetic resonance (MR) signal generated by the excitation is detected, and a two-dimensional tomographic image of the subject is reconstructed based on the signal.

[0004] In such magnetic resonance imaging, in recent years, the need for high-speed imaging to reduce the time required for imaging has become extremely high. In response to this, pulse sequences involving high-speed switching (high-speed reversal) of gradient magnetic field pulses, such as the high-speed echo planar imaging (EPI) method, have been developed, and some have been successfully commercialized.

When a gradient magnetic field pulse is generated, an electromagnetic force acts on the gradient magnetic field coil when the pulse rises or reverses.
The electromagnetic force causes mechanical distortion in the coil unit, and the entire unit vibrates starting from the mechanical distortion. Due to the vibration of the coil unit, there is a problem that air vibration is generated and noise is generated.

In particular, when the gradient magnetic field pulse is reversed at a high speed, the vibration increases, so that the noise increases as the speed increases. This noise may give the subject (patient) lying in the imaging space of the gantry a great discomfort or anxiety.

[0007] Therefore, in order to eliminate such noise, there is an attempt to seal the entire unit of the gradient magnetic field coil in a vacuum vessel and cut off the air propagation of vibration or noise in a vacuum space.

[0008] However, the above-mentioned conventional noise control method still has the following unsolved problems. In a hermetic container for hermetically closing a gradient magnetic field coil in a vacuum space, containers and covers forming the vacuum space are jointed to a cover and a housing of a static magnetic field magnet. The gradient magnetic field coil itself has a structure in which the static magnetic field magnet is supported by a container or a cover.

For this reason, a part of the vibration (noise) generated by the gradient magnetic field coil is cut off in the vacuum space, but another part of the vibration propagates to the static magnetic field magnet or the like via the support of the gradient magnetic field coil. Resulting in. Therefore, there is a problem that the static magnetic field magnet also vibrates due to the vibration generated by the gradient magnetic field coil, and the whole gantry acts as a vibration source to generate a large noise.

Further, an O-ring structure is used to seal the inside of the portion where the cover of the closed container is joined to the cover of the static magnetic field magnet, but the airtightness is not sufficient, and a sufficient vacuum is not provided. I can't get a degree.
Therefore, the effect of preventing noise from propagating in the air is not sufficient.

As described above, the gradient coil is housed in a closed container for noise prevention, but the coil in the container cannot be checked from the outside. Therefore, it is necessary to remove the container cover for checking and adjusting the position of the gradient magnetic field coil, and the work load is large.

When the degree of vacuum is increased to enhance the noise prevention effect, the sealed container may be deformed. Increasing the strength of the closed container to prevent deformation increases the size and weight of the container this time. Therefore, the degree of vacuum cannot be made too high.

In the above description, the noise mainly generated by the gradient magnetic field coil has been described. However, there are other vibration sources. For example, superconducting coils have been widely used as static magnetic field magnets, and the superconducting coils are housed in a cryostat. The displacer of the cold head of this cryostat makes a piston movement by the pressure of helium gas. This piston motion propagated to a container such as an 80k shield and generated noise. At present, no particular countermeasures are taken against noise generated by the cold head as a vibration source.

The gantry is composed of many parts.
Many of these components are made of metal. If there is a potential difference between the metal parts when they are fastened to each other, a so-called B radio wave is generated by the vibration generated mainly by the gradient magnetic field coil, and the B radio wave is picked up by the RF coil. There is also a problem that the image quality is deteriorated due to the electrons mixed into the signal line.

In order to magnetically shield the RF coil, a magnetic shield is arranged outside the RF coil. This magnetic shield generally has a structure in which a plurality of thin strip-shaped copper plates are attached in parallel at predetermined intervals on the surface of a resin substrate, and a capacitor is inserted between adjacent copper plates.
Further, there is a type in which a plurality of thin strip-shaped copper plates are attached to the front and back surfaces of a resin substrate as a dielectric in parallel with a predetermined space therebetween, thereby realizing a capacitor structure between the front and back surfaces. However, in any of these structures, there is a problem that a sufficient shielding effect cannot be obtained due to a shortage of capacity of the capacitor.

As a vibration source, not only the above-mentioned gradient magnetic field coil but also an eddy current due to a leakage magnetic field from the gradient magnetic field coil is generated in a conductive material of a circuit unit including a tuning circuit of an RF coil, thereby causing Lorentz. Vibration occurs with the force. At present, no countermeasures are taken against this vibration.

Also, a vacuum pump for evacuating the air inside the sealed container needs to be maintained at a relatively high frequency, and under a situation where the load on the pump increases more and more with the spread of high-speed sequences. However, reducing the frequency of maintenance of this pump is also an issue for the future.

Further, the degree of vacuum of the sealed container is inevitable to some extent over time due to the operating conditions of the pump, the airtightness of the sealed container, and various other factors. Since the magnetic field intensity also fluctuates due to the fluctuation of the degree of vacuum, the resonance frequency fluctuates, and there is a concern that the image may be deteriorated due to the fluctuation. But,
At present, no special measures are taken against the deterioration of the image quality due to the fluctuation of the degree of vacuum.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to satisfactorily suppress noise generated by a gradient coil or the like in a magnetic resonance imaging apparatus.

[0020]

According to the present invention, there is provided a magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient coil, a high-frequency coil, and a sealed container accommodating the gradient coil. It is characterized by being joined to the static magnetic field magnet or its container via an annular flange.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic resonance imaging apparatus according to the present invention will be described with reference to the drawings. First, a basic configuration of the magnetic resonance imaging apparatus will be described with reference to FIG. The magnetic resonance imaging apparatus includes a mount (gantry) 14 having an imaging space into which an object to be diagnosed is inserted and arranged, and the mount 14
And a control processing unit (computer system) that controls the operations of the gantry 14 and the bed 18 and processes the MR signal. Note that the gantry 14 is typically formed with a substantially cylindrical photographing space penetratingly formed in a central portion on the inner side thereof. The axial direction of this cylindrical imaging space is defined as Z, and an X direction (left-right method) and a Y direction (vertical direction) orthogonal to the Z direction are defined.

The gantry 14 receives a current from the static magnetic field power supply 2 and places a static magnetic field H0 in the imaging space. Is provided. This static magnetic field magnet 1 is typically constituted by a superconducting magnet. The overall shape of the static magnetic field magnet 1 is formed in a substantially cylindrical shape. A gradient magnetic field coil 3 is arranged in the bore of the magnet 1. The gradient magnetic field coil 3 is provided with three sets of coils 3x, 3y, 3z for individually receiving a current supply from the gradient magnetic field power supply 4 and generating a gradient magnetic field for each of the XYZ axes.
Consists of This gradient magnetic field coil 3 is used to reduce noise.
It is housed in a sealed container whose inside is maintained at or near a vacuum by a vacuum pump.

A radio frequency coil (RF coil) 7 is arranged further inside the gradient magnetic field coil 3. RF coil 7
Is connected to the transmitter 8T and the receiver 8R.
The transmitter 8T supplies a current pulse oscillating at a Larmor frequency for exciting nuclear magnetic resonance (NMR) to the high-frequency coil 7 under the control of the sequencer 5. Receiver 8R
Receives the MR signal (high-frequency signal) via the high-frequency coil 7 and performs various kinds of signal processing to form a corresponding digital signal.

The sequencer 5 is placed under the control of a controller 6 that manages the entire apparatus. Controller 6
Is connected to the input device 13. In the operation, a desired pulse sequence can be selected from a plurality of types of pulse sequences such as a spin echo method (SE) and an echo planar method (EPI) via the input device 13. The controller 6 sets the selected pulse sequence in the sequencer 5. The sequencer 5 controls the application timing and strength of each gradient magnetic field in the X, Y, and Z axis directions, the application timing of the high-frequency magnetic field, the amplitude, the duration, and the like in accordance with the set pulse sequence.

The arithmetic unit 10 receives the MR signal (digital data) formed by the receiver 8R, arranges the actually measured data in a two-dimensional Fourier space formed by a built-in memory, and reconstructs an image. Processing such as Fourier transform is performed to generate image data and spectrum data. The storage unit 11 stores the calculated image data. The display 12 displays an image.

Next, an embodiment relating to a magnetic resonance imaging apparatus having the above basic configuration will be described.

(First Embodiment) FIG. 2 is a longitudinal sectional view of a mount of the magnetic resonance imaging apparatus according to the first embodiment. The gradient coil 102 may be a non-shield type or an active shield type. The gradient magnetic field coil 102 has an x coil, a y coil, and a z coil as its windings. The x coil, y coil and z coil are impregnated in a bobbin having a cylindrical shape.

This gradient magnetic field coil 1 having a substantially cylindrical shape
02 is supported on a heavy concrete base base 125 installed on the floor surface. Further, the gradient magnetic field coil 102 is housed in a closed container 133.
The sealed container 133 has a liner 131 having a substantially cylindrical shape and constituting the inner wall thereof, and a vacuum lid 132 thereof.
A cryostat 1 for placing a static magnetic field magnet (here, a superconducting coil) in a cryogenic environment is provided on the back surface of the closed vessel 133.
It is closed by 16 inner walls 117. The side wall 118 of the cryostat 116 is joined to the vacuum lid 132 by a joining plate 135. The airtight container 133 and the gantry base 125 are connected by a vacuum bellows 134 in order to keep the airtightness of the airtight container 133.

The air inside the closed vessel 133 is exhausted by a vacuum pump, and the inside of the closed vessel 133 is kept in a vacuum or a state close to the vacuum. As a result, air propagation of noise generated by the gradient magnetic field coil 102 is prevented.

An RF coil 1 is provided on the inner surface of the liner 131.
A high frequency magnetic field is applied to the subject via the RF coil 103, and an MR signal from the subject is received.

In such a configuration, vacuum leakage is likely to occur at the connection between the side wall 118 of the cryostat 116 and the joining plate 135. In order to prevent this vacuum leak, an O-ring 108 for vacuum sealing is sandwiched between the side wall 118 of the cryostat 116 and the bonding plate 135. However, the surface accuracy of the side wall 118 of the cryostat 116 is not very high. Therefore, the contact accuracy of the O-ring 108 with the side surface 118 of the cryostat 116 is not so high, and the sealing performance of the O-ring 108 is not sufficient.

On the other hand, in this embodiment, as shown in FIG. 3, an annular flange 106 is welded to the side wall 118 of the cryostat 116 (reference numeral 107), and the flange 106 is attached to the closed container 133. Joining plate 135
Are fixed by bolts 109 via O-rings 108. The flange 106 can be formed with high precision by shaving or the like. Therefore, the flange 106 can make good contact with the O-ring 108,
The sealing performance of the ring 108 can be maximized. Further, since the connection between the side wall 118 of the cryostat 116 and the flange 106 is performed by welding, airtightness therebetween is ensured. Therefore, a substantially vacuum state inside the sealed container 133 can be maintained, and air propagation of vibration and noise can be shielded well.

(Second Embodiment) FIG. 4A shows the appearance of a sealed container of a gradient coil according to a second embodiment. The gradient magnetic field coil is housed in a closed container 201 which is maintained in a substantially vacuum state in order to reduce noise. For this reason, conventionally, in order to confirm the position of the gradient coil, it was necessary to partially disassemble the closed vessel 201.

On the other hand, in the present embodiment, the closed container 2
Each of the side walls 207 of 01 is hollowed out in a pair on the left and right. In this part, a window 202 made of glass or fiber-reinforced plastic which transmits visible light is fitted. Through the window 202, the position of the gradient coil in the closed container 201 can be easily visually recognized from the outside.

As shown in FIG. 4B, a scale 206 indicating the position is attached to the gradient magnetic field coil 204. The scale 206 is visible through the window 202. By looking at the scale 206, the relative position of the gradient magnetic field coil 204 with respect to the static magnetic field magnet 205 can be objectively grasped.

As shown in FIG. 4C, the leg 203 of the closed container 201 has a base 212. The gradient magnetic field coil 2
A support 213 supporting the support 04 is fitted so as to be movable up and down. A thread is cut on the outer periphery of the column 213, and a screw 215 is engaged with the thread by a cross axis. By rotating the dial 214 at the tip of the screw 215, the column 213 moves up and down together with the gradient coil 204 inside the container 201. Thereby, the relative position of the gradient magnetic field coil 204 with respect to the static magnetic field magnet 205 can be adjusted.

As described above, even if the container is not disassembled, the gradient coil can be visually recognized from the outside, and the position can be adjusted. Therefore, the chance of deterioration in airtightness can be reduced. Thereby, the airtightness of the container can be ensured, and the effect of shielding the air propagation of vibration and noise can be enhanced.

As shown in FIG. 4D, the static magnetic field magnet container 217 is joined to the side wall 207 of the sealed container 201 via the joining plate 235.
A round is made at the corner where the 35 is joined. Similarly, not only the joint between the side wall 207 and the joint plate 235 but also the cylindrical inner wall (liner) of the closed container 201
A round is also provided at the corner where the joint plate 235 is joined with the joint plate 235. As a result, the resistance of the sealed container containing the gradient coil to the atmospheric pressure can be improved.

(Third Embodiment) FIG. 5 shows the appearance of a sealed container of a gradient coil according to a third embodiment.
The gradient magnetic field coil is housed in the closed container 301. In order to prevent air propagation of noise generated by the gradient magnetic field coil 102, the air inside the sealed container 301 is evacuated by a vacuum pump, and the inside of the sealed container 133 is maintained at a vacuum or a state close thereto. The closed container 13
3 receives atmospheric pressure. Therefore, the strength of the closed container 133 is important. In the second embodiment, the closed container 133 is used.
The window 302 is attached to the side wall 204 of the rim. In this embodiment, in order to increase the strength of the window 302,
By forming a side wall 304 around the window 302 as a convex portion 303 having a round shape like a half pipe, the strength of a portion around the window 302 is reinforced.

By this reinforcement, the degree of vacuum (internal pressure) of the sealed container 301 can be sufficiently increased (decreased), and the effect of shielding the air propagation of vibration and noise can be enhanced.

Further, as shown in FIG.
1 has a liner 309 having a substantially cylindrical shape constituting the inner wall thereof, and a vacuum lid 307 thereof. Closed container 30
The back of 1 is closed by the inner wall of a cryostat 306 for placing a static magnetic field magnet (here, a superconducting coil) in a cryogenic environment. Side wall 311 of cryostat 306
Are joined to a vacuum lid 307.

In the actual manufacturing process, the cryostat 3
For a length L1 of 06, a closed container 30 in which it is fitted.
In some cases, the length L2 of the opening 1 does not match. In this case, the airtightness of the container 301 is reduced, and a vacuum leak occurs. In order to solve this, in the present embodiment,
An annular packing 310 can be inserted between the liner 309 and the vacuum lid 307 of the closed container 301. Therefore, when the length L2 of the opening portion of the sealed container 301 into which the cryostat 306 is fitted does not match the length L1 of the cryostat 306, the liner 309 and the vacuum lid 307 of the sealed container 301 are sandwiched by a packing 310 having an appropriate width. Cryostat 3 by joining
For a length L1 of 06, a closed container 30 in which it is fitted.
The length L2 of the opening can be easily adjusted.

The packing 310 allows the closed container 30
1 and the cryostat 306 with improved joining accuracy,
The airtightness of the container 301 can be improved. Thus, the effect of shielding vibration and noise from air propagation can be enhanced.

(Fourth Embodiment) The source of vibration and noise in the magnet mount is not limited to the gradient coil. For example, there is a superconducting coil heat exchanger employed as a static magnetic field magnet. 7 and 8 are cross-sectional views of the heat exchanger according to the present embodiment. Superconducting coil 401 is housed in cryostat 404. Cryostat 4
Reference numeral 04 denotes heat radiation shields 402, 405, and outer peripheral surfaces of a liquid nitrogen tank accommodating the superconducting coil 401 together with liquid nitrogen.
At 406, it is configured so as to surround multiple.

The cryostat 404 has a heat exchanger 4 that absorbs heat from the shield 402 and discharges the heat to the outside.
07 is provided. The heat exchanger 407 has a cylinder 408 whose bottom is in contact with the shield 402, a cover for the cylinder 408, a cold head 411 cooled by helium gas He, and a cylinder 4.
08, between the bottom and the cold head 411, there is provided a displacer 409, which makes a piston movement by the pressure of the helium gas He, and a vacuum bellows 410.

When displacer 409 is at the bottom, displacer 409 absorbs heat from shield 402. When displacer 409 is on top,
Displacer 409 transfers heat to cold head 411. By repeating such an operation, the shield 40
2 can be exhausted.

As described above, the displacer 409
Makes a piston motion in the cylinder 408, so that vibration occurs. This vibration causes the shields 402, 405,
It propagates mechanically to 406. This generates noise.

A dynamic vibration absorber 414 is mounted on the cold head 411 to absorb the vibration. The dynamic vibration isolator 414 is configured such that the spring 412 serves as an elastic body so that the direction of expansion and contraction of the spring 412 is substantially parallel to the direction of the piston movement of the displacer 409.
11, and a weight 413 is connected to the spring 412. When the displacer 409 makes a piston movement, the weight 413 moves up and down following the piston movement. Thereby, the vibration of the cold head 411 generated by the displacer 409 is absorbed by the dynamic vibration isolator 414,
As a result, noise is reduced.

Normally, the displacer 409 makes a piston motion at the frequency of the commercial power supply. The dynamic vibration isolator 414
Displacer 40 that makes piston movement at this frequency
The resilience of the spring 412 and the mass of the weight 413 are set so as to resonate with the vibration generated by the source 9. Thereby, vibration can be effectively absorbed.

Note that, as shown in FIG.
8-1,408-2, Displacer 409-1,4
09-2, cold heads 411-1 and 411-2
Two heat exchangers are provided one by one, and the two heat exchangers are arranged so that the axes of movement of the pistons are opposed to each other.
Even if the pistons 09-2 are caused to move in opposite phases, the vibration can be reduced.

(Fifth Embodiment) FIG. 10 is a longitudinal sectional view of a mount of a magnetic resonance imaging apparatus according to a fifth embodiment. The gradient coil 502 has x as its winding.
It has a coil, a y coil and a z coil. The x coil, y coil and z coil are impregnated in a bobbin having a cylindrical shape. The gradient magnetic field coil 502 having a substantially cylindrical shape is supported on a heavy concrete base base 525 installed on the floor surface. Also,
The gradient magnetic field coil 502 is housed in a closed container 533. The sealed container 533 has a liner 531 having a substantially cylindrical shape and constituting the inner wall thereof, and a vacuum lid 532 thereof. The back surface of the sealed container 533 is closed by an inner wall 517 of a cryostat 516 for placing a static magnetic field magnet (here, a superconducting coil) in a cryogenic environment. The side wall 518 of the cryostat 516 is joined to the vacuum lid 5 by a joining plate 535.
32. Sealed container 533 and gantry base 5
Between 25 and, in order to keep the airtightness of the closed container 533,
They are connected by a vacuum bellows 534.

The vibration of the gradient magnetic field coil 502 is mechanically propagated to the closed vessel 533. The frequency of the oscillation of the gradient magnetic field coil 502 is equivalent to the alternating frequency of the gradient magnetic field of the pulse sequence. In response to the vibration of the gradient magnetic field coil 502, the liner 531 of the closed container 533 and the vacuum lid 53
2 so that the natural frequency of the liner 531 and the natural frequency of the vacuum lid 532 differ from each other with respect to the vibration frequency of the gradient magnetic field coil 502. Are mounted discretely with weights 541, 542, 543 and 544.

The weight 544 attached to the vacuum lid 532
For example, it is a non-magnetic metal piece. In addition, the liner 53 has an annular gel-like substance 541 along its inner wall,
542, 543 are mounted. Substances 541, 542,
The place where the 543 is attached is outside the RF coil 503 in order to avoid a decrease in the Q value of the RF coil 503.

According to such a structure, the liner 53 of the closed vessel 533 is not affected by the vibration of the gradient magnetic field coil 502.
1 and the vacuum lid 532 do not resonate. Therefore, noise is reduced.

Instead of attaching a weight to the liner 531 and the vacuum lid 532, or together with the weight, the liner 5
The thickness of the vacuum lid 31 and the vacuum lid 532 may be partially reduced. In short, the point of this embodiment is to partially increase or decrease the mass of the liner 531 and the vacuum lid 532 in order to shift the natural frequency. In addition, a beam or a brace may be inserted for reinforcement along with the shift of the natural frequency.

(Sixth Embodiment) FIG. 11 is a longitudinal sectional view of a mount of a magnetic resonance imaging apparatus according to a sixth embodiment. The gradient coil 602 has x as its winding.
It has a coil, a y coil and a z coil. The x coil, y coil and z coil are impregnated in a bobbin having a cylindrical shape. The gradient coil 602 having a substantially cylindrical shape is supported on a heavy concrete base base 625 installed on the floor. Also,
The gradient magnetic field coil 602 is housed in a closed container 633. The sealed container 633 includes a liner 631 having a substantially cylindrical shape, a vacuum lid 632 having a substantially annular plate shape,
And a back casing 634 having a substantially cylindrical shape. A cryostat 616 for placing a static magnetic field magnet (here, a superconducting coil) in a cryogenic environment is disposed outside the back casing 634 of the sealed container 633. An RF coil 635 is arranged on the inner surface of the liner 631, and applies a high-frequency magnetic field to the subject via the RF coil 635 and receives an MR signal from the subject.

The point of this embodiment is that the inner wall of the cryostat 616 is not used for the sealed container 633 that houses the gradient magnetic field coil 602, in other words, the sealed container 633 is completely separate from the cryostat 616. Consists in configuring. When the inner wall of the cryostat 616 is used for the sealed container 633 accommodating the gradient magnetic field coil 602, vacuum leakage is likely to occur at the joint portion due to low surface accuracy and dimensional error of the cryostat 616. However, in this embodiment, since the cryostat 616 is not joined to the closed container 633, that is, the closed container 633 is manufactured independently, high airtightness is achieved without depending on the low surface accuracy and the dimensional error of the cryostat 616. be able to.

(Seventh Embodiment) The seventh embodiment is intended to prevent the generation of B radio waves and the generation of induced electrons due to the rubbing of metal parts in a gantry, and to physically vibrate or The present invention is applicable to fastening of all metal parts constituting a mount of the magnetic resonance apparatus in which the vibration propagates.

The gantry is composed of a large number of metal parts, and metal screws are mainly used for fastening these parts. For example, as shown in FIG. 12A, when attaching a copper tuner plate 724 to a metal frame frame 724, conventionally, it is common to use a metal screw 723 and a metal insert 722. Although many capacitors are provided in the gantry, metal screws are often used when attaching the capacitors to a tuner plate or the like and when fastening the connector of the RF coil tuner to the tuner plate. As described above, metal screws are used in almost all places to fix components in the gantry.
As shown in FIG. 2 (b), when the metal screw and the metal parts and the metal parts rub against each other due to the above-described intense vibration, a so-called B radio wave is generated. This B radio wave may be picked up by the RF coil and cause image artifacts, but has not been regarded as a problem until recently. However, in order to realize a high-speed and high-intensity gradient magnetic field in recent years, a higher voltage has been applied, and accordingly, the B radio wave tends to be stronger. At present, image artifacts caused by the increased B radio wave noise have already expanded to a level that cannot be ignored. Also, B
Not only radio waves but also electrons induced by, for example, contact and vibration between a connector and a tuner plate are mixed into a signal line as they are, which causes a problem that an image artifact is generated.

The present embodiment has been made for the purpose of preventing the generation of B radio waves and induced electrons which cause such noise.

As is well known, the gantry is a magnet device mainly composed of a static magnetic field magnet, a gradient magnetic field coil, and an RF coil, and includes many metal parts. There are numerous places where these metal parts can be attached to other parts. This attachment point can be roughly divided into two types.
As shown in FIG. 4, one is a copper plate 7 constituting an RF coil.
09,710 attached together, the RF coil copper plate 70
9, 710 and capacitor 711, RF coil copper plate 710 and lead copper plate 703, lead copper plate 703 and RF coil tuner copper plate 704, RF coil tuner copper plate 704 and connector 70
6 and a part that requires electrical connection while physically fixing parts such as the copper plate 704 of the RF coil tuner and the capacitor 715, and the other is simply This is a place where electrical connection is not required for the main purpose of physically fixing parts together.

In the former case, most preferably, the solder 70
5 is to be attached. In this case, there is no rubbing between parts, so no B radio wave is generated,
No induced electrons are generated. However, there are some places where solder cannot be used due to its weak fastening force. Screws are used at this point.

FIG. 15 shows, as an example, a resin screw 7
An example is shown in which metal parts 731 and 732 are attached to each other by using 33. Conventionally, since a metal screw was used, it was inevitable that B radio waves and induced electrons would be generated due to friction between the metal screw and the metal component 731 and between the metal screw and the metal component 732. But,
In this example, since the resin screw 733 is used, such occurrence can be prevented.

FIG. 16 shows a metal screw 734 as another example.
In this example, the metal parts 731 and 732 are attached to each other using a metal screw 734. In order to avoid contact between the metal screw 734 and the metal part 731, a substantially cylindrical resin spacer 735 is used.
In order to avoid contact between the metal screw 734 and the metal component 732, a resin tap 736 is used.
In this example, while using the metal screw 734, the gap between the metal screw 734 and the metal component 731 as well as the metal screw 733 is used.
4 and the metal component 732, the resin members 735, 736
, It is possible to prevent the generation of B radio waves and induced electrons.

Of course, either of the mounting methods shown in FIGS. 15 and 16 may be adopted, or both methods may be described.
Further, the effect of reducing the generation of the B radio wave and the induced electrons can be expected even if the mounting method shown in FIGS. .

At the latter attachment point, that is, at a place where electrical connection is not required mainly for the purpose of simply fixing the parts physically, for example, as shown in FIG. 737 and 738 are attached, but by inserting an insulating sheet 739 between the metal parts 737 and 738, the generation of B radio waves and induced electrons due to the friction between the metal screw and the metal parts as in the related art is prevented. Not only metal parts 737, 738
It is also possible to prevent the generation of the B radio wave and the induced electrons due to the friction between the two.

FIG. 18 shows an example in which metal parts 737 and 738 are attached to each other using a metal screw 734. Cylindrical resin spacer 740
In order to avoid contact between the metal screw 734 and the metal component 738, a resin tap 741 is used.
In this example, while using the metal screw 734, the gap between the metal screw 734 and the metal component 737 and the metal screw 73
4 and the metal component 738, the resin members 740, 741
, It is possible to prevent the generation of B radio waves and induced electrons.

Of course, either of the mounting methods shown in FIGS. 17 and 18 may be adopted, or both methods may be described.
In addition, the effect of reducing the generation of the B radio wave and the induced electrons can be expected even if the mounting method shown in FIGS. .

In addition to the mounting of metal parts, the mounting method shown in FIGS. 17 and 18 can be applied to the mounting parts of the metal parts and the resin parts such as the coil bobbin. Generation of B radio waves and induced electrons due to friction between the screw and the metal component can be prevented.

(Eighth Embodiment) The eighth embodiment relates to an improvement in an RF shield disposed on the outer periphery of an RF coil.
The RF shield is typically formed of a copper cylinder in order to magnetically isolate the RF coil from the outside and shield electromagnetic noise entering the RF coil from the outside.
An eddy current is generated in the copper cylinder due to the high-speed switching of the gradient magnetic field, causing distortion in the gradient magnetic field. In order to shorten the time constant of the eddy current, many slits are formed in the copper cylinder.

Further, a magnetic field having a relatively low frequency (up to about 100 KHz) such as a gradient magnetic field passes, and a high-frequency magnetic field of several MHz to several tens MHz such as an excitation pulse is cut off.
That is, a capacitor is connected between the copper plates across the slit in order to increase the low-frequency impedance and decrease the high-frequency impedance. As another conventional structure of the RF shield, a capacitance is formed between the front and back surfaces by pasting a plurality of copper plates on the surface of the dielectric substrate with a gap (slit) therebetween, and further pasting a plurality of copper plates on the back surface. R
There is also an F shield.

Echo Planar Imaging (EP
Although a high-speed imaging method such as I) is required for, for example, imaging of the heart, an extremely rapid gradient magnetic field response is essential for this. For this reason, it is necessary to provide a large number of slits at fine intervals (intervals). However, when a large number of slits are provided, the capacitance is reduced as the area of the copper plate is reduced, so that high-frequency short circuits in individual slits are incomplete. As a result, the shielding function is imperfect.

In the present embodiment, both the increase in the number of slits and the prevention of a decrease in capacity are realized. FIG. 19 is a partial perspective view of the RF shield according to the present embodiment. A plurality of copper plates 802 are provided on a surface of the dielectric substrate 801 with predetermined gaps (slits) 805.
Is pasted. Similarly, a plurality of copper plates 803 are stuck on the back surface of the dielectric substrate 801 with a predetermined gap (slit) 806. Dielectric substrate 8
A capacitance is formed between the copper plates 802 and 803 opposed to each other with the “01” therebetween.

Further, on the surface of the dielectric substrate 801, a capacitor 804 is connected between the adjacent copper plates 802. Similarly, a capacitor 805 is connected between the adjacent copper plates 803 on the back surface of the dielectric substrate 801.

In this configuration, the surface capacitor 8
04, the capacitor 805 on the back surface, and the capacitance between the copper plate 802 on the front surface and the copper plate 803 on the back surface are:
Sufficient capacity can be ensured to complete a high frequency short circuit.

(Ninth Embodiment) FIG. 20 is a longitudinal sectional view of a gantry of a magnetic resonance imaging apparatus according to a ninth embodiment. The gradient coil 902 has x as its winding.
It has a coil, a y coil and a z coil. The x coil, y coil and z coil are impregnated in a bobbin having a cylindrical shape. The gradient magnetic field coil 902 having a substantially cylindrical shape is supported on a heavy concrete base base 925 installed on the floor surface. Also,
The gradient magnetic field coil 902 is housed in a closed container 933. The closed container 933 has a liner 931 having a substantially cylindrical shape and constituting the inner wall thereof, and a vacuum lid 932 thereof. The back surface of the sealed container 933 is closed by an inner wall 917 of a cryostat 916 for placing a static magnetic field magnet (here, a superconducting coil) in a cryogenic environment. The side wall 918 of the cryostat 916 is joined by a joining plate 935 to the vacuum lid 9.
32. Closed container 933 and gantry base 9
Between 25 and, in order to keep the airtightness of the closed container 933,
They are joined by a vacuum bellows 934.

An RF coil 9 is provided on the inner surface of the liner 931.
03 is arranged. A transmitter and a receiver are connected to the RF coil 903. The transmitter is provided to supply a high-frequency current pulse corresponding to the Larmor frequency to the RF coil 903 in order to bring the nuclear magnetization of the subject into an excited state with a high-frequency magnetic field, and typically includes an oscillation unit, It comprises a phase selector, a frequency converter, an amplitude modulator, and a high-frequency power amplifier. In addition, the receiver is an RF coil 903
In order to receive the MR signal from the subject through the, a preamplifier, an intermediate frequency converter, a phase detector, a low frequency amplifier, a low-pass filter, and an AD converter are provided.

The transmitter and the receiver are contained in an RF unit 940. The location of the RF unit 940 is set near the RF coil 903 in order to shorten the cable and reduce power loss and noise. Conventionally, as shown by a dotted line in FIG. 20, the RF unit is attached to a vacuum lid 932 near the edge of the opening 941. However, this place is the gradient coil 902
This is the place where the magnetic field leaking from is largest. The RF unit 940 includes many conductive components, and these conductive components include:
An eddy current is generated from the gradient magnetic field coil 902 by a leakage magnetic field, and as a result, the conductive component vibrates due to Lorentz force. This vibration is transmitted to the sealed container 933 and noise is generated.

The present embodiment aims at reducing noise generated by the RF unit 940 as a source. RF
The unit 940 includes the vacuum lid 9 near the edge of the opening 941.
32, and in a location physically separated from the closed container 933, here, in the radial direction of the gantry cylinder from the central axis (Z axis), outside the RF coil 903 and near immediately below the opening 941 Installed in Specifically, the RF unit 940 is installed on a heavy concrete base base 925 or a separate dedicated base.

This installation location is more than a conventional installation location.
The influence of the leakage magnetic field from the RF coil 903 is small. Therefore, the vibration of the conductive component of the RF unit 940 is reduced. In addition, since the RF coil 903 is physically separated from the closed container 933 and is attached to the heavy concrete base base 925, the minute vibration of the RF coil 903 is hardly transmitted to the closed container 933. .

Therefore, noise generated by the RF unit 940 can be reduced. (Tenth Embodiment) As described above, the gradient coil is
For noise control, it is housed in a sealed container whose internal air is exhausted by a vacuum pump. The higher (lower) the degree of vacuum (pressure) in the closed container, the greater the noise shielding effect. Conventionally, in order to increase the degree of vacuum in the closed container, the vacuum pump is continuously operated during scanning. This continuous operation shortens the life of the vacuum pump. The use of a vacuum pump with reduced capacity cannot increase the degree of vacuum in the closed container, and the noise shielding effect is reduced.

This embodiment realizes the noise shielding effect to be maintained as long as possible by reducing the load on the vacuum pump. FIG. 21 shows a vacuum pump and a piping system according to the present embodiment. The sealed container 1001 is connected to a vacuum pump 1002 via a main tube 1003. An electromagnetic valve 1004 is arranged in the middle of the main tube 1003. A branch tube 1005 is connected to the main tube 1003, and the end is opened via an electromagnetic valve 1006.

Operation of vacuum pump 1002, electromagnetic valve 1
Opening and closing of 004 and opening and closing of electromagnetic valve 1006 are under the control of pump / valve control unit 1020. The vacuum pump 1002 operates (ON) and stops (O) according to the control of the pump / valve control unit 1020 as shown in FIG.
FF) are alternately repeated. The length of the operation period T1 and the length of the stop period T2 are set in advance so that the pressure in the sealed container 1001 does not exceed a predetermined upper limit. The length of the operation period T1 and the length of the stop period T2 can be arbitrarily adjusted.

By operating the vacuum pump 1002 intermittently instead of continuously, the vacuum pump 1
The maintenance frequency of the oil and the oil filter can be reduced as compared with the case where the 002 is operated continuously. As shown in FIG. 23, opening and closing of the electromagnetic valve 1004,
The opening / closing of the electromagnetic valve 1006 is related to the intermittent operation of the vacuum pump 1002 by the pump / valve control unit 1020.

First, the electromagnetic valve 1006 of the branch tube 1005 is opened and closed in synchronization with the intermittent operation of the vacuum pump 1002. That is, the electromagnetic valve 1006
It is closed in synchronization with the switching of the vacuum pump 1002 from off to on, and is opened in synchronization with the switching of the vacuum pump 1002 from on to off.

On the other hand, in order to reduce the load on the vacuum pump 1002, the electromagnetic valve 1004 of the main tube 1003 is opened with a time T3 later than the switching timing of the vacuum pump 1002 from off to on. It is closed at a timing earlier than the switching timing of the vacuum pump 1002 from on to off by a time T4. These time differences T3 and T4 are set to arbitrary times from several seconds to several minutes.

The electromagnetic valve 100 is delayed by a time T3 from the switching timing of the vacuum pump 1002 from off to on.
By opening 4, the lubrication in the vacuum pump 1002 can be completed within a relatively short time (prevacuum period) of time T3 after the on-start of the vacuum pump 1002. This is because the exhaust target has a small volume from the pump inlet to the electromagnetic valve 1004. And time T after on-start
After a lapse of 3 seconds, the valve 1004 of the main tube 1003
Is opened and the closed container 1001 is opened from the electromagnetic valve 1004.
Evacuation operation (main vacuum) for the large capacity of the total volume of the closed container 1001
At this time, since the lubrication in the vacuum pump 1002 has already been completed, it is possible to smoothly shift to the main vacuum operation. Therefore, the load on the vacuum pump 1002 can be reduced.

Next, after a lapse of a predetermined time (T1-T4) since the vacuum pump 1002 was turned on, that is, at a time T4 earlier than the timing when the vacuum pump 1002 was turned off, the valve 10 of the main tube 1003 was turned off.
04 is closed. This means that the sealed container 1001 is separated from the vacuum pump 1002 with the pressure of the sealed container 1001 sufficiently reduced. Thus, it is possible to prevent a sudden increase in the pressure in the sealed container 1001 due to the stoppage of the vacuum pump 1002.

(Eleventh Embodiment) FIG. 24 shows the structure of a main part of a magnetic resonance imaging apparatus according to an eleventh embodiment. The gantry 1101 has a static magnetic field magnet 1102 for generating a static magnetic field H0, a gradient magnetic field power supply (G-amp) 11
05, a gradient coil 1103 receiving a current supply from
RF coil 1104 and shim coil power supply (Shim-a
mp) and a plurality of shim coils 1116 for generating a magnetic field for correcting static magnetic field inhomogeneity by receiving a current supply from 1107.

The gradient magnetic field coil 1103 is housed in a sealed container 1115 whose inside is maintained at or near a vacuum by a vacuum pump 1111 in order to reduce noise.
Inside the sealed container 1115, a plurality of vacuum sensors (vacuum gauges) 1112 for measuring the internal pressure are discretely arranged. The vacuum degree data measured by the vacuum degree sensor 1112 is sent to the storage unit 1113 and stored. The storage unit 1113 stores the operating state data from the vacuum pump 1111 together with the degree of vacuum data. The operation status data indicates the operation time of the vacuum pump 1111.

The maintenance information generating unit 1114 is configured to store the airtight container 1115 and the vacuum pump 11 based on the degree of vacuum data and the operation status data stored in the storage unit 1113.
11 maintenance information is generated in a timely manner. The maintenance information generating unit 1114 obtains the closed container 11 from the vacuum degree data.
When the degree of vacuum (pressure) in 15 does not fall below a predetermined pressure corresponding to, for example, 99 dB in the imaging region, maintenance information is generated to prompt maintenance of the vacuum pump 1111 and the sealed container 1115. Further, the maintenance information generating unit 1114 calculates the cumulative operation time from the operation status data, and generates maintenance information for urging the maintenance of the vacuum pump 1111 when the cumulative operation time exceeds a predetermined value. Maintenance information is in the closed container 1
This message is, for example, a message for prompting maintenance of the vacuum pump 115 and the vacuum pump 1111 and is displayed on the display 1110.

The receiver 1108 collects an MR signal (high-frequency signal) via the RF coil 1104, performs preprocessing such as detection and AD conversion, and outputs the result to the processor 1109. A processor 1109 processes the collected MR data and generates images and spectra. These images and spectra are sent to the display 1110 and displayed.

The processor 1109 has a function of correcting the phase of the MR data collected by the receiver 1108 and performing a frequency shift based on the degree of vacuum data, in addition to the main function of generating an image and a spectrum. ing. When the degree of vacuum changes, the intensity H0 of the static magnetic field also changes. When the intensity H0 of the static magnetic field varies, the resonance frequency f0 of, for example, protons under a static magnetic field on which no gradient magnetic field is superimposed also varies. Processor 1109
Holds data representing the relationship between the degree of vacuum measured in advance and the resonance frequency f0, and refers to this relationship data to specify the resonance frequency (corrected resonance frequency) f0 corresponding to the degree of vacuum data. On the basis of the corrected resonance frequency f0, MRS (MR spectroscopy)
The phase of the MR data collected at 108 is corrected and the frequency is shifted. A spectrum is generated based on the corrected data. In practice, we ’ve collected data several times,
Phase correction and frequency shift are individually performed for each data to generate a plurality of spectra, and the plurality of spectra are added. At the time of EPI (echo planar imaging), an EPI image is generated based on the acquired data, and the EPI image is shifted in the phase encoding direction.
(E direction is large, but also occurs a little in RO direction). In practice, data acquisition is repeated several times, an EPI image is individually generated for each data, each image is individually shifted in the phase encoding direction, and addition or subtraction of these plurality of EPI images is performed. Similarly, in the case of a phase image,
Calculate the amount of phase shift based on the corrected resonance frequency f0,
The phase image is corrected based on the phase shift amount.

As described above, according to this embodiment, maintenance information can be generated in a timely manner. Further, the phase and frequency can be corrected according to the change in the degree of vacuum.

(Twelfth Embodiment) FIG. 25 shows the structure of a main part of a magnetic resonance imaging apparatus according to a twelfth embodiment. The gantry 1201 has a static magnetic field magnet 1202 for generating a static magnetic field H0, a gradient magnetic field power supply (G-amp) 12
05, a gradient coil 1203 receiving a current supply from
An RF coil 1204 connected to a transceiver (RF-amp) 1208, and a shim coil power supply (Shim-amp)
A plurality of shim coils 1216 for generating a magnetic field for correcting static magnetic field inhomogeneity by receiving a current supply from 1207 are incorporated.

The gradient magnetic field coil 1203 is housed in a sealed container 1215 whose inside is maintained at or near a vacuum by a vacuum pump 1211 for noise control.
Inside the closed container 1215, a plurality of vacuum sensors (vacuum gauges) 1212 for measuring the internal pressure are discretely arranged. A real-time manager 1210 based on the vacuum data measured by the vacuum sensor 1212
Is a gradient magnetic field power supply 1205 according to the pulse sequence,
The transceiver 1208 outputs a command to the sequence controller 1209 for controlling the shim coil power supply 1207, for example, to wait for the execution of the pulse sequence. The real-time manager 1210 controls the operation of the vacuum pump 1211 based on the measured data of the degree of vacuum.
Note that the system manager 1213 is a console 121
The system is provided to control the entire system in accordance with an operator's instruction input via the control unit 4.

First, the real-time control of the real-time manager 1210 will be described. Real-time manager 1210 performs the following functions. (1) The vacuum pump 1211 starts operating prior to the start of a scan. At this time, a scan start command is issued to the sequence controller 1209 until the degree of vacuum in the sealed container 1215 (pressure inside the sealed container) falls below a predetermined value. Do not issue That is, the real-time manager 1210
Sends a scan start command to the sequence controller 1209 for the first time when the degree of vacuum exceeds a predetermined value. (2) When performing a pulse sequence that is sensitive to magnetic field fluctuations such as MRS and EPI, the vacuum pump 1211 is continuously operated, particularly during scanning. (3) When the degree of vacuum exceeds a predetermined value during a scan, a scan start command is issued to the sequence controller 1209 to stop the scan. (4) When the degree of vacuum is lower than the predetermined value, the vacuum pump 1211 is operated before the start of scanning, and a scan start command is not issued to the sequence controller 1209 until the degree of vacuum reaches the predetermined value.

(5) The operation pattern of the vacuum pump 1211 is selectively used according to the photographing conditions (type of pulse sequence, number of averages, dynamic photographing, etc.). For example,
When performing a pulse sequence such as spin echo that is not so sensitive to magnetic field fluctuation, the pump 1211 is operated intermittently as shown in FIG. For example, vacuum pump 1
211 is operated for a period ΔT1, and then the operation is performed for a period Δt1.
Stop for a while. This operation / stop is repeated alternately. When performing a pulse sequence that is relatively sensitive to magnetic field fluctuations, FIG.
As shown in FIG. 6B, the operation period ΔT2 of the pump 1211
And the suspension period Δt2 is shorter than ΔT1 and Δt1,
Thereby, the magnetic field fluctuation width is reduced. Further, when performing a pulse sequence that is extremely sensitive to magnetic field fluctuations such as MRS and EPI, the pump 1211 is continuously operated as shown in FIG. Furthermore, when performing a pulse sequence that is very sensitive to magnetic field fluctuations such as MRS and EPI, instead of continuously operating the pump 1211, the pump 1211 is stopped and the inside of the sealed container is brought to atmospheric pressure. You may. in this case,
No noise reduction effect can be expected, but at least magnetic field fluctuations are eliminated. The real-time manager 1210
Stores information on image quality parameters (magnetic field non-uniformity, center frequency, phase shift) corresponding to the atmospheric pressure in advance so that the image can be properly reconstructed even at the atmospheric pressure. , Shim coil current, center frequency and phase of high frequency current pulse of transceiver 1208,
Further, the reference frequency and phase of the receiving system are adjusted.

(6) The pump 1211 is operated / stopped according to the result of comparison between the measured degree of vacuum and a predetermined value. That is, when the measured degree of vacuum exceeds the upper limit, the pump 1211 is operated, and when the measured degree of vacuum is lower than the lower limit, the pump 1211 is stopped. Thereby, the fluctuation of the degree of vacuum can be suppressed to a range between the upper limit value and the lower limit value. The upper limit value and the lower limit value can be changed according to the photographing conditions, as in (5).

(7) If the degree of vacuum does not fall below a predetermined value even when the pump 1211 is continuously operated, a warning is issued by voice or image display.

The real-time manager 1210 also has a function of performing the following correction according to the degree of vacuum.
(1) The non-uniformity of the magnetic field changes according to the degree of vacuum. The relationship between the degree of vacuum and the non-uniformity of the magnetic field is measured in advance and stored in the real-time manager 1210. The real-time manager 1210 refers to this relationship, specifies the magnetic field non-uniformity according to the degree of vacuum, and adjusts the shim coil current flowing through the shim coil 1207 according to the specified magnetic field non-uniformity. Thereby, the non-uniformity of the magnetic field can be corrected immediately. In practice, the relationship between the degree of vacuum and the magnetic field inhomogeneity is measured discretely, and the magnetic field inhomogeneity is obtained from the discrete values by linear interpolation. (2) When the degree of vacuum fluctuates, the intensity of the static magnetic field also fluctuates, and accordingly, for example, the resonance frequency B0 of protons under a static magnetic field on which no gradient magnetic field is superimposed also fluctuates. The real-time manager 1210 adjusts the center frequency and phase of the high-frequency current pulse of the transmission system of the transceiver 1208 according to the resonance frequency B0 corresponding to the degree of vacuum. Also, the reference frequency and phase of the receiving system are adjusted.

(Modifications) The present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the scope of the invention at the stage of implementation.
Furthermore, the above embodiment includes various steps,
Various inventions can be extracted by appropriately combining a plurality of disclosed components. For example, some components may be deleted from all the components shown in the embodiment.

[0103]

According to the present invention, noise generated by a gradient magnetic field coil or the like can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a magnetic resonance imaging apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a vertical sectional view of a gantry according to the first embodiment.

FIG. 3 is an enlarged view within a broken line in FIG. 2;

FIG. 4 is a diagram showing a structure of a closed container according to a second embodiment.

FIG. 5 is a perspective view of a closed container according to a third embodiment.

FIG. 6 is a cross-sectional view showing the joining of the closed container and the static magnetic field magnet container of FIG. 5;

FIG. 7 is a longitudinal sectional view of a cryostat of a static magnetic field magnet according to a fourth embodiment.

FIG. 8 is an internal structural diagram of the dynamic vibration absorber of FIG. 7;

FIG. 9 is an internal structural view of a cold head portion according to another example of the seventh embodiment.

FIG. 10 is a longitudinal sectional view of a gantry according to a sixth embodiment.

FIG. 11 is a longitudinal sectional view of a gradient coil unit according to a seventh embodiment.

FIG. 12 is a diagram showing the principle of generation of noise radio waves in the seventh embodiment.

FIG. 13 is a view showing the tuner copper plate of FIG. 11 and its connection parts.

FIG. 14 is a view showing a connection example of metal parts in the seventh embodiment.

FIG. 15 is a view showing another connection example between metal parts in the seventh embodiment.

FIG. 16 is a view showing an example of insulated connection between metal parts in the seventh embodiment.

FIG. 17 is a view showing another example of insulated connection between metal parts in the seventh embodiment.

FIG. 18 is a view showing still another example of insulated connection between metal parts in the seventh embodiment.

FIG. 19 is a perspective view of an RF shield according to an eighth embodiment.

FIG. 20 is a longitudinal sectional view of a gantry of the magnetic resonance imaging apparatus according to the ninth embodiment.

FIG. 21 is a system diagram of a vacuum pump of a sealed container according to a tenth embodiment.

FIG. 22 is a diagram showing a pressure change in a closed container in the tenth embodiment.

FIG. 23 is a timing chart of ON / OFF of a vacuum pump and opening and closing of a valve in the tenth embodiment.

FIG. 24 is a main part configuration diagram of a magnetic resonance imaging apparatus according to an eleventh embodiment.

FIG. 25 is a main part configuration diagram of a magnetic resonance imaging apparatus according to a twelfth embodiment.

FIG. 26 is a diagram showing a variation of the operation pattern of the vacuum pump in the twelfth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Static magnetic field magnet, 2 ... Static magnetic field power supply, 3 ... Gradient magnetic field coil 3, 4 ... Gradient magnetic field power supply, 5 ... Sequencer, 6 ... Controller, 7 ... RF coil, 8T ... Transmitter, 8R ... Receiver, 10 ... Arithmetic unit, 11 storage unit, 12 display unit, 13 input unit, 14 gantry, 18 bed.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ayumu Katsunuma 1385-1 Higashiyama, Higashiyama, Shimoishi-kami, Otawara-shi, Tochigi Pref. (1) Inside the Toshiba Nasu Factory (72) Inventor Masao Yui 1385 Higashiyama, Higashiyama, Shimoishi-kami, Otawara-shi, Tochigi Prefecture Inside (72) Inventor Yoshitomo Sakakura 1385 Higashiyama, Shimoishi-kami, Otawara-shi, Tochigi Ban No. 1 Toshiba Nasu Factory Co., Ltd. (72) Inventor Manabu Ishii 2-16-4 Akabane, Kita-ku, Tokyo Toshiba Medical System Engineering Co., Ltd. (72) Inventor Yasuhara Yasuhara 1385 Higashiyama, Shimoishigami, Otawara City, Tochigi Prefecture No. 1 Toshiba Nasu Factory Co., Ltd. (72) Inventor Kazuto Nogami 1385-1 Higashiyama, Shimoishigami, Otawara-shi, Tochigi Pref. Inside the plant (72) Inventor Takeshiro Suzuki 1385-1 Higashiyama, Higashiyama, Shimoishi-kami, Otawara-shi, Tochigi Prefecture Inside of the Toshiba Nasu Factory (72) Inventor Haruji Nozaki 1385-1, Higashiyama, Shimoishi-kami, Otawara-shi, Tochigi Inside the Nasu Factory (72) Inventor Yoshio Machida 1385-1 Higashiyama, Shimoishigami, Otawara City, Tochigi Prefecture Inside the Nasu Factory Toshiba Corporation (72) Inventor Masaaki Yamanaka 1385-1, Higashiyama, Shimoishigami, Otawara City, Tochigi Co., Ltd. F-term in Toshiba Nasu factory (reference) 4C096 AB47 AD08 AD19 CA02 CA22 CA27 CA42 CA52 CA59 CA60 CA62 CA67 CA70 CB07 CB19 CB20 FC20

Claims (39)

[Claims] 1. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the closed container is provided with an annular flange through an annular flange. A magnetic resonance imaging apparatus which is joined to a magnetic field magnet or its container. 2. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the closed container has a reinforcing projection on an end face. A magnetic resonance imaging apparatus, characterized in that: 3. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein a round is provided at a corner of the closed container. A magnetic resonance imaging apparatus. 4. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient coil, wherein the closed container comprises a plurality of container portions, A magnetic resonance imaging apparatus, wherein parts are joined via a packing material. 5. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the closed container has a window. Magnetic resonance imaging device. 6. A magnetic resonance imaging apparatus according to claim 5, wherein said gradient magnetic field coil is provided with a scale for visually recognizing a position of said gradient magnetic field coil through said window. 7. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the position of the gradient magnetic field coil is independent of the closed container. A magnetic resonance imaging apparatus, comprising: a mechanism for performing a change. 8. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the static magnetic field magnet is a superconducting magnet. A magnetic resonance imaging apparatus, comprising: a cold head having a displacer for performing a piston motion for performing heat exchange with the cold head, wherein the cold head is provided with a vibration absorbing mechanism. 9. The magnetic resonance imaging apparatus according to claim 8, wherein said vibration absorbing mechanism has a characteristic of resonating at a frequency of a commercial power supply. 10. A magnetic resonance imaging apparatus comprising a mount having a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the mount comprises: A magnetic resonance imaging apparatus, wherein a metal piece or a gel-like substance is attached to shift a natural frequency with respect to a frequency of vibration. 11. A magnetic resonance imaging apparatus comprising a mount having a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the mount comprises: A magnetic resonance imaging apparatus, wherein a slit is formed to shift a natural frequency with respect to a frequency of vibration. 12. A magnetic resonance imaging apparatus comprising a mount having a static magnetic field magnet, a gradient coil, a high-frequency coil, and a sealed container accommodating the gradient coil, wherein the mount shifts a resonance frequency. For this purpose, a magnetic resonance imaging apparatus characterized in that a plurality of metal pieces or gel substances having different masses are attached. 13. A magnetic resonance imaging apparatus comprising a gantry having a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein the closed container is provided from the static magnetic field magnet. A magnetic resonance imaging apparatus, which is configured independently. 14. A magnetic resonance imaging apparatus comprising a gantry having a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a sealed container accommodating the gradient magnetic field coil, wherein a plurality of parts constituting the gantry are fastened. In some places,
A magnetic resonance imaging apparatus wherein metal contact is avoided. 15. The magnetic resonance imaging apparatus according to claim 14, wherein the other portions of the plurality of parts are electrically connected to each other. 16. The magnetic resonance imaging apparatus according to claim 14, wherein said parts are fastened with resin screws to avoid said metal contact. 17. A magnetic resonance imaging apparatus comprising: a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and a magnetic shield for suppressing magnetic interference between the gradient magnetic field coil and the high frequency coil. The magnetic shield is characterized in that a plurality of strip-shaped copper plates are arranged at predetermined intervals on both sides of the dielectric substrate, and a capacitor is connected between adjacent copper plates. Magnetic resonance imaging device. 18. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and the gradient magnetic field coil, wherein a circuit unit of the high frequency coil includes the gradient magnetic field coil as viewed from an imaging center axis. A magnetic resonance imaging apparatus, wherein the magnetic resonance imaging apparatus is located farther away than the target. 19. A magnetic resonance imaging apparatus comprising a gantry having a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and the gradient magnetic field coil, wherein the circuit unit of the high frequency coil is mounted on a floor base of the gantry. A magnetic resonance imaging apparatus. 20. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a sealed container accommodating the gradient magnetic field coil, wherein a pump for exhausting air inside the sealed container is provided. A magnetic resonance imaging apparatus comprising: a control circuit for intermittently operating the pump. 21. The magnetic resonance imaging apparatus according to claim 20, wherein an electrically controllable valve is provided in a pipe between the pump and the closed vessel. 22. The control circuit according to claim 21, wherein the control circuit operates the pump intermittently and shifts a timing of opening and closing the valve with respect to a timing of switching the pump on and off. The magnetic resonance imaging apparatus according to claim. 23. The control circuit, wherein a timing of opening the valve is delayed by a predetermined time from a timing of starting the operation of the pump, and a timing of closing the valve is advanced by a predetermined time from a timing of stopping the pump. The magnetic resonance imaging apparatus according to claim 22. 24. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient magnetic field coil, a high frequency coil, and a sealed container accommodating the gradient magnetic field coil, wherein a pump for exhausting air inside the sealed container is provided. A magnetic resonance imaging apparatus comprising: a vacuum gauge for detecting a degree of vacuum inside the closed container. 25. The magnetic resonance imaging apparatus according to claim 24, further comprising a recording unit for recording the data of the detected degree of vacuum. 26. The magnetic device according to claim 24, further comprising a correction unit configured to correct data collected via the high-frequency coil or an image generated from the data based on the detected degree of vacuum. Resonance imaging device. 27. The correction unit estimates a shift of a resonance frequency based on the detected degree of vacuum, and generates a shift from data collected via the high-frequency coil based on the estimated shift of the resonance frequency. 27. The magnetic resonance imaging apparatus according to claim 26, wherein a phase correction and / or a frequency shift are performed on a plurality of spectra, and these spectra are added. 28. The correction unit estimates a shift of a resonance frequency based on the detected degree of vacuum and generates a shift from data collected via the high-frequency coil based on the estimated shift of the resonance frequency. 27. The magnetic resonance imaging apparatus according to claim 26, wherein each of the plurality of images is shifted in a phase encoding direction, and the plurality of images are added or subtracted. 29. The correction unit estimates a shift of a resonance frequency based on the detected degree of vacuum, and generates the shift from data collected via the high-frequency coil based on the estimated shift of the resonance frequency. 27. The magnetic resonance imaging apparatus according to claim 26, wherein each of the plurality of phase images is phase-shifted. 30. The magnetic resonance imaging apparatus according to claim 24, further comprising: means for outputting maintenance information of the sealed container and / or the pump based on the detected degree of vacuum. 31. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein a pump for exhausting air inside the closed container is provided. Means for generating an MR signal from the subject in accordance with arbitrarily set imaging conditions and driving the gradient magnetic field coil and the high-frequency coil to collect the MR signals; and an operation pattern of the pump according to the imaging conditions A magnetic resonance imaging apparatus, comprising: 32. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient coil, a high-frequency coil, and a sealed container accommodating the gradient coil, wherein a pump for exhausting air inside the sealed container is provided. A control unit that drives the gradient magnetic field coil and the high-frequency coil in accordance with a pulse sequence selected from a plurality of types of pulse sequences to generate an MR signal from the subject and collect the MR signal; And a pump controller for changing the on-time of the pump in accordance with the pulse sequence. 33. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient coil, a high frequency coil, and a sealed container accommodating the gradient coil, wherein a pump for exhausting air inside the sealed container is provided. A control unit that drives the gradient magnetic field coil and the high-frequency coil in accordance with a pulse sequence selected from a plurality of types of pulse sequences in order to generate an MR signal from the subject and collect the MR signal; And a pump control unit for operating the pump when the selected pulse sequence is a first pulse sequence and stopping the pump when the selected pulse sequence is a second pulse sequence. Magnetic resonance imaging apparatus. 34. The magnetic resonance imaging apparatus according to claim 33, further comprising a vacuum gauge for detecting a degree of vacuum of the closed container. 35. The magnetic resonance imaging apparatus according to claim 34, further comprising a processing unit for correcting a phase and / or a frequency of data collected via the high-frequency coil according to the detected degree of vacuum. apparatus. 36. The apparatus according to claim 33, further comprising a control unit for stopping the driving of the gradient magnetic field coil and the high frequency coil and the data collection when the detected degree of vacuum does not satisfy a predetermined condition. Magnetic resonance imaging equipment. 37. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a sealed container accommodating the gradient magnetic field coil, wherein a shim coil for correcting the intensity distribution of the static magnetic field is provided. A magnetic resonance imaging apparatus, comprising: a vacuum gauge for detecting a degree of vacuum of the closed container; and means for changing a current supplied to the shim coil based on the detected degree of vacuum. 38. A magnetic resonance imaging apparatus comprising a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, a sealed container accommodating the gradient magnetic field coil, and a shim coil for correcting magnetic field non-uniformity. A magnetic resonance imaging apparatus, comprising: a sensor for detecting a degree of vacuum in a closed container; and a control unit that changes a driving condition for the shim coil based on the detected degree of vacuum. 39. A magnetic resonance imaging apparatus having a static magnetic field magnet, a gradient magnetic field coil, a high-frequency coil, and a closed container accommodating the gradient magnetic field coil, wherein a pump for exhausting air inside the closed container is provided. A vacuum gauge for detecting the degree of vacuum in the closed container; and a degree of vacuum in the closed container of about 3 mmHg (0.7 kPa).
A magnetic resonance imaging apparatus comprising: a pump control unit that controls operation of the pump based on the detected degree of vacuum as described below.