JP2015000165A - Magnetic resonance imaging apparatus, and bed for imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus suppressing vibration transmitted to a top plate caused by Lorentz force produced in a gradient magnetic field coil without making a gantry length longer, and further reducing an artifact due to movement of a subject by suppressing the vibration to improve image quality.SOLUTION: A magnetic resonance imaging apparatus includes an imaging apparatus and a bed 20, and has: a bed vertical movement part 4 vertically moving a top plate holding part 6 holding a top plate 7 provided to the bed 20 and mounted with a subject 30; at least one vibration isolation material 8 disposed in a ground contact part with a floor of a top plate guide vertical movement part 10 vertically moving a top plate guide 5 provided in the imaging apparatus and holding the top plate 7; the top plate guide vertical movement part 10; and a control part 15 controlling the top plate guide vertical movement part 10. The top plate holding part 6 and the top plate guide part 5 are connected to each other at a desired height, and the top plate guide 5 is supported in a non-contact manner with the imaging apparatus.

Description

  The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a magnetic resonance imaging apparatus including a bed that suppresses unpleasant vibration during imaging.

  A magnetic resonance imaging device uses a nuclear magnetic resonance phenomenon of a nucleus to obtain a magnetic resonance image that represents the physical properties of an object placed in the imaging space, and generates a static magnetic field that generates a static magnetic field in the imaging space. Means, a gradient magnetic field generating means for providing a linear gradient magnetic field superimposed on the static magnetic field, an irradiation coil for generating high-frequency electromagnetic waves for causing nuclear magnetic resonance in the nuclei constituting the subject, and nuclear magnetic resonance A receiving coil or the like for detecting an echo signal generated by the above is provided, and an image is reconstructed using the echo signal to obtain a tomographic image.

  In such a magnetic resonance imaging apparatus, in recent years, there is a growing need for shortening the time required for imaging. In response to such a demand, for example, a pulse sequence with high-speed inversion of a gradient magnetic field pulse has been developed and put into practical use.

  When taking an image using the above pulse sequence, a pulsed large current is passed through a gradient coil placed in a static magnetic field to give position information to each signal emitted from the measurement target. There is a phenomenon in which Lorentz force acts on the coil and mechanical distortion occurs in the gradient coil. Since this phenomenon repeatedly acts, the gradient magnetic field coil vibrates, and further, when the gradient magnetic field pulse is reversed at high speed, the vibration increases, so that the vibration increases as the imaging speed increases. This vibration is transmitted to the top plate on which the subject in the imaging space is placed via the gantry in which the gradient magnetic field coil is installed, and not only makes the subject uncomfortable, but also the subject moves, This causes artifacts and causes disturbance in the captured image.

  As a technique for reducing this vibration, a technique for reducing the vibration of the top board by disposing the top board support portion from the gantry in a non-contact manner is disclosed (for example, see Patent Document 1).

JP 2010-284233 A

  However, in the conventional method as shown in Patent Document 1, the top plate support portion installed from the floor requires a large space at the end of the gantry, the length of the gantry becomes long, and there is a problem that it lacks openness. is there.

  Therefore, an object of the present invention is to suppress vibration transmitted to the top plate due to Lorentz force generated in the gradient coil without increasing the gantry length in the magnetic resonance imaging apparatus.

  In order to solve the above problems, the main configuration of the magnetic resonance imaging apparatus of the present invention is as follows.

  An imaging device for imaging the subject and a bed on which the subject is mounted and moved, and a top plate holding unit for holding the top plate on which the subject is mounted, and the imaging device is carried into the imaging space A top plate guide for holding the top plate, a top plate guide vertical movement unit that is provided on the floor surface where the imaging device is installed via a vibration insulating material and supports one end of the top plate guide, and attached to the imaging device A top plate guide support portion that supports the other end of the top plate guide, and at the time of imaging, a top plate guide portion is provided using a connecting portion that is provided on the bed and connects the top plate holding portion and the top plate guide portion. The other of these is floated from the top guide support part and is held in a non-contact state.

  According to the present invention, it is possible to suppress the vibration transmitted to the top plate due to the Lorentz force generated in the gradient coil without increasing the gantry length. As a result, vibration suppression can reduce artifacts due to movement of the subject and improve image quality.

The figure which shows the magnetic resonance imaging apparatus of this invention. The figure explaining the top-plate holding | maintenance part of this invention. The figure explaining the bed vertical moving part of this invention. The figure which shows the magnetic resonance imaging apparatus of this invention. The figure explaining the connection part of this invention. AA sectional drawing explaining the connection part of this invention. The figure explaining the connection part of this invention. The figure which shows another example of the magnetic resonance imaging apparatus of this invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments of the invention. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the invention, and the repetitive description thereof is omitted.

First embodiment

≪Device configuration≫
A magnetic resonance imaging apparatus according to the first embodiment will be described below.
FIG. 1 is a diagram showing a magnetic resonance imaging apparatus of the present invention. As shown in FIG. 1, the gradient magnetic field coil 2 is arranged inside the static magnetic field generator 1, and the irradiation coil 3 is arranged inside the gradient magnetic field coil 2. The static magnetic field generator 1 forms a uniform magnetic field region, and the gradient magnetic field coil 2 is composed of three types of coils (X, Y, Z) orthogonal to each other, and each applies a gradient magnetic field to the imaging space. The irradiation coil 3 irradiates a high-frequency signal to cause nuclear magnetic resonance to occur in atomic nuclei constituting the biological tissue of the subject.

  The bed 20 is vibration-insulated between the top surface 7 on which the subject is placed, the top plate holding unit 6 that holds the top plate 7, the bed vertical moving unit 4 that moves the top plate holding unit 6 up and down, and the floor surface. It is composed of a material 8.

  The top plate guide 5 is on the side opposite to the bed side of the static magnetic field generator 1 and the top plate guide support portion 9 disposed on the side of the static magnetic field generator 1 on the side of the bed, and is not different from the static magnetic field generator 1. The top plate 7 is supported by the top plate guide vertical movement unit 10 installed on the floor surface via the vibration insulating material 8 so that the top plate 7 travels on the top surface of the top plate guide 5.

Here, the vibration insulating material 8 is a rubber having a natural frequency in a low frequency region of 10 Hz or less and capable of obtaining a vibration isolating effect in a frequency band of 15 to 40 Hz where the human body feels uncomfortable. Since the static spring constant is ideally 200 to 300 N / mm or less, a static displacement of several mm to several tens mm is caused by the load of the bed 20 and the subject. For this reason, according to load, the top-plate holding | maintenance part 6 and the top-plate guide 5 are moved up and down, and the operation | movement which makes it non-contact with the static magnetic field generator 1 is needed.
In this embodiment, rubber is used as a member for obtaining a vibration isolation effect, but other members may be used as long as they have a vibration isolation effect and have the above-described spring constant.

  The top plate guide vertical movement unit 10 has the same mechanism as the bed vertical movement unit 4 and moves the top plate guide 5 up and down.

  Furthermore, it comprises a control unit 15 for controlling the top plate holding unit 6, the bed vertical movement unit 4 and the like, and a console 14 for operating the apparatus.

  FIG. 2 is a diagram illustrating details of the top plate holding unit 6 of the bed 20 described above. The top plate 7 includes wheels 7 a on the bottom surface thereof, and the wheels 7 a can travel on the top surface of the top plate holding unit 6 and the top plate guide 5. The forward / backward moving unit 12 for moving the top and the back is provided in the top plate holding unit 6 and includes a pulley 12b to which the belt 12a is connected and a drive motor 12c for moving the top and bottom, and according to instructions received by the operation unit. The drive motor 12c is operated by the control signal, and the belt 12a is driven to move the top plate 7 back and forth.

  FIG. 3 is a diagram showing the bed up / down moving unit 4 of the bed 20 described above. The bed vertical movement unit 4 includes a link mechanism unit 4a, a ball screw 4b, and a drive motor 4c that rotates the ball screw 4b, and the drive motor 4c is operated by a control signal to move the top plate holding unit 6 up and down.

≪Bedroom operation explanation≫
In FIG. 4, the top plate holding unit 6 is operated by the bed vertical movement unit 4, the top plate holding unit 6 and the top plate guide 5 are in contact, and the top plate guide 5 on the side in contact with the top plate holding unit 6 is moved. A state in which the top plate guide 5 is separated from the top plate guide support portion 9 is shown.
Meanwhile, one end of the top plate guide 5 shown in FIG. 1 is supported by the top plate guide vertical movement unit 10, and the other end is supported by the top plate guide support unit 9. However, since one end of the top plate guide 5 is fixed by the top plate guide vertical movement unit 10, the top plate guide 5 is in a cantilever state with a fixed part with the top plate guide vertical movement unit 10 as a fulcrum. The end is a free end, and the portion of the top plate guide 5 that has been lowered by its own weight is supported by the top plate guide support portion 9. Since the structure as described above is employed, it is possible to create a gap between the top plate guide 5 and the top plate guide support portion 9 by lifting the top plate guide 5.

  In FIG. 4, a gap is generated between the top plate guide 5 and the top plate guide support portion 9, and the top plate guide 5 and the top plate guide support portion 9 are in a non-contact state. Therefore, the vibration from the floor is not transmitted to the top plate guide 5 through the top plate guide support portion 9.

≪Description of top plate connection part≫
FIG. 5 is a diagram showing details of the connecting portion between the top plate holding portion 6 and the top plate guide 5.
The top plate holding portion 6 has a structure in which the lower side of the side end protrudes, and the top plate guide 5 has a structure in which the upper side of the side end facing the top plate holding portion 6 protrudes. Therefore, the top plate holding part 6 and the top plate guide 5 can be connected so as to mesh with each other. Further, the lengths of the protruding portions are adjusted to be substantially the same so that there is no gap between them when connected. Note that this structure is an example, and other structures may be used as long as the protruding portions do not have a gap therebetween.

  Grooves 5 c and 6 b are provided on both side surfaces on the upper surface side and on the lower surface side of the top plate holding portion 6, and grooves 5 b are provided on both side surfaces on the upper surface side of the top plate guide 5.

  The connecting member 13 is a member that connects the top plate guide 5 and the top plate holding portion 6, and has a protruding portion on the upper side and the lower side, and the upper side of the protruding portion is movable along the grooves 5 c and 5 b. Yes, the lower side is movable along 6b.

Further, a connecting member 13 and a plunger 13b for preventing the connecting member from falling off are provided.
When the connecting member 13 moves, the plunger 13b has a structure that can be retracted into the groove of the top plate guide 5 so as not to inhibit the movement. When the movement is completed, the plunger 13b protrudes and functions to prevent the dropout by fixing the connecting member.

  Further, a projection 13 a that is movable up and down is provided near the tip of the top plate 7 on the connecting portion side, and the projection 13 a is fitted into a hole provided in the connecting member 13 to fix the top plate 7 and the connecting member 13. Accordingly, the connecting member 13 moves simultaneously with the movement of the top plate 7. When the movement is completed, the protrusion 13a is pulled out from the connecting member 13 (see FIG. 6), and the top plate 7 is in a state where it can move without being constrained by the connecting member 13.

  FIG. 6 shows a state in which the top plate 7 is moved in the front-rear direction (left to right in the figure) from the state of FIG. 5 and the top plate guide 5 and the top plate holding part 6 are connected by the connecting member 13.

  FIG. 7 is a cross-sectional view taken along the line AA in FIG. When the top plate 7 advances in the imaging region direction, the connecting member 13 moves together with the top plate 7 along the grooves 6b and 5c, 5b, and when the connecting member 13 is arranged at a desired position, the top plate 7 The protrusion 13a is retracted, and the connecting member 13 is held by the plunger. When the top plate 7 moves backward, when the projection 13 a returns to the position of the hole of the connecting member 13, it protrudes and contacts the connecting member 13, and the connecting member 13 is separated from the top plate guide 5.

≪Description of operation≫
Next, the operation of the first embodiment will be described.

  The operator inputs information necessary for imaging such as the name, registration number, imaging parameter, imaging region, and weight of the subject using the console 14 shown in FIG. The control unit 15 calculates the amount of movement of the longitudinal movement unit 12 and the bed vertical movement unit 4 from the imaging region and the body weight of the subject input at the console. The amount of movement of the bed vertical movement unit 4 and the table top vertical movement unit 10 is calculated based on the amount of displacement of the vibration insulating material acquired in advance according to the weight of the imaging region and the subject, The top plate holder 6 is raised from the static magnetic field generator to a desired height that can be supported in a non-contact manner.

  Next, the movement amount of the forward / backward movement part is calculated from the input information of the imaging region, and the top board moves according to the movement amount. At this time, the top plate guide 5 and the top plate holding part 6 are mechanically coupled by the coupling member as the coupling member 13 moves along the groove. Furthermore, a change in the load applied to the vibration insulating materials of the top plate holding unit 6 and the top plate guide 5 when the top plate 7 moves is calculated, and the bed vertical movement unit 4 and the top plate guide according to the load. The amount of movement of the vertical movement part is continuously changed.

  By the above, the top plate 7 moves smoothly and is supported in a non-contact manner from the static magnetic field generator, and unpleasant vibration during imaging can be reduced.

Second embodiment

  The second embodiment is the same as the first embodiment except for a control method for calculating the movement amount of the bed vertical movement unit 4 and the top plate guide vertical movement unit 10.

  In the present embodiment, a sensor (not shown) is provided that detects the height of the top plate holding unit 6 from the floor surface and the height of the top plate guide 5 from the floor surface. This sensor can be provided, for example, at a position where the sensor signal can go straight with respect to the floor surface on the bottom surface of the top plate holding unit 6. Note that the installation location is not limited as long as the height from the floor can be detected.

  The control unit 15 calculates the amount of movement of the back-and-forth moving unit 12 and the bed up-and-down moving unit 4 from the imaging region input from the console and the body weight of the subject. When the bed vertical movement unit 4 and the top guide vertical movement unit 10 are moved up and down, the height information from the sensor is acquired at any time and moved up and down until a desired height that does not contact the static magnetic field generator is obtained.

  Furthermore, when the top plate 7 moves, the height information from the sensor is acquired at any time, and the movement amount of the bed vertical movement unit 4 and the top plate guide vertical movement unit 10 is set so as to maintain a constant height. Control is performed by the control unit 15.

Third embodiment

  In the first and second embodiments described above, the bed 20 is described as being integrated with the magnetic resonance imaging apparatus. However, the bed 20 may be used separately from the magnetic resonance imaging apparatus.

  As an example, for example, a bed 21 shown in FIG. 8 can be a self-propelled mobile table with wheels 11. The couch 21 has the same structure as that of the couch 20 described in the first and second embodiments except for the wheel 11 and its mounting portion. That is, the top plate 7 is supported by the top plate holding unit 6, and the top plate holding unit 6 is moved up and down by the bed vertical movement unit 4. A subject 30 is placed on the top board 7. A wheel 11 is attached to the lower part of the bed vertical movement section 4 so that the bed 21 can be self-propelled.

  When the couch 21 is moved and the top plate holding unit 6 reaches a distance that can be connected to the magnetic resonance imaging apparatus, the couchtop 21 is fixed by causing the wheel stopper to function.

  The connecting portion provided at one end of the top plate holding portion 6 has the structure described in the first and second embodiments.

  Further, the operation of the bed 21 after fixing and the connecting operation with the magnetic resonance imaging apparatus are the same as those described in the first and second embodiments.

  Therefore, in the third embodiment, similarly to the effects of the first and second embodiments, the vibration transmitted to the top plate due to the Lorentz force generated in the gradient coil without increasing the gantry length. Can be suppressed. Furthermore, by suppressing the vibration, artifacts due to the movement of the subject can be reduced and image quality can be improved.

1: Static magnetic field generator,
2: Gradient field coil,
3: Irradiation coil,
4: Sleeper vertical movement part,
5: Top plate guide,
6: Top plate holder,
7: Top plate
8: Vibration insulating material,
9: Top plate guide support part,
10: Top plate guide vertical movement part,
11: wheels,
12: Longitudinal moving part,
13: connecting member,
14: Console,
15: Control unit,
20: Sleeper.

Claims (10)

An imaging device for imaging a subject, and a bed on which the subject is mounted and moved,
A top plate holding unit for holding a top plate for mounting the subject provided on the bed;
A top plate guide for holding the top plate carried into the imaging space of the imaging device;
A top plate guide vertical movement unit provided on a floor surface on which the imaging device is installed via a vibration insulating material, and supporting one end of the top plate guide;
A top plate guide support part attached to the imaging device and supporting the other end of the top plate guide;
At the time of imaging, using the connecting portion that is provided on the bed and connects the top plate holding portion and the top plate guide portion, the other of the top plate guide portions is lifted from the top plate guide support portion and brought into a non-contact state. A magnetic resonance imaging apparatus characterized by holding. The couch has a couch vertical movement unit that drives the couch holding unit in the vertical direction, and a back-and-forth movement unit that moves the couch to the imaging space,
The connecting portion holds the other of the top plate guide portion and the top plate guide support portion in a contact state or a non-contact state by the vertical movement of the bed vertical movement portion. The magnetic resonance imaging apparatus described. One end of the top plate guide is supported by the top plate guide support portion, and the other end is supported by the top plate guide vertical movement portion,
The magnetic resonance imaging apparatus according to claim 1, wherein at the time of imaging, one end of the top plate guide is held in a non-contact state with respect to the top plate guide support portion. Both ends of the top plate in the imaging space are supported by a top plate guide vertical movement portion provided via a vibration insulating material and the top plate holding portion provided on the bed. The magnetic resonance imaging apparatus according to claim 1. Having a control unit for controlling the top plate guide vertical movement unit and the bed vertical movement unit;
The control unit moves the top / bottom guide vertical movement unit and the bed vertical movement unit in the vertical direction based on a desired vertical movement amount calculated based on the imaging region and body weight of the subject. The magnetic resonance imaging apparatus according to claim 2. The control unit includes a sensor that measures a displacement between the bed vertical movement unit and the top guide, and the bed vertical movement based on a vertical movement amount calculated from a displacement amount measured using the sensor. The magnetic resonance imaging apparatus according to claim 5, wherein the position adjustment in the vertical direction is performed by moving up and down the unit and the top / bottom guide vertical movement unit. The magnetic resonance imaging apparatus according to claim 1, wherein the bed has a moving mechanism capable of self-running. An imaging apparatus bed having a top board on which a subject is mounted and a top board holding part for supporting the top board,
The imaging apparatus bed has a coupling mechanism that enables attachment to and detachment from an imaging apparatus that images the subject,
The coupling mechanism is provided on one side surface of a top plate guide that supports a first projection portion provided on one side surface of the top plate holding portion and the top plate carried into the imaging space of the imaging device. A bed for an imaging device, comprising: a fixing mechanism that releasably fixes the second protrusion. The imaging apparatus bed includes a bed vertical movement unit that drives the top plate holding unit in the vertical direction,
The imaging apparatus according to claim 8, wherein at the time of imaging, the bed vertically moving unit is used to float from a top plate guide support unit that is attached to the imaging device and supports one end of the top plate guide and is held in a non-contact state. A bed for an imaging apparatus as described. The imaging apparatus bed according to claim 8, wherein the imaging apparatus bed has a self-propelled moving mechanism.

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