JP2005160842A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus which reduces an oppressive sensation on an upper surface of a subject placed in an examination space. <P>SOLUTION: A homogeneous magnetic field region 50 is formed by vertically placing static magnetic field generating devices 1 to oppose each other. Gradient magnetic field coils 2 are vertically placed to have the region 50 between the coils 2, while opposing each other, and high-frequency magnetic field coils 3 are vertically placed to have the region 50 between the coils 3, while opposing each other. A circular dent 51 is formed in the central part on the surface of the region 50 of a device 1. The coil 2 is mounted on the dent 51, and the coil 3 is mounted to cover the coil 2. A V-shaped cut 52 is formed along the direction in which a bed 4 is inserted on the surface of the region 50 of the device 1. Consequently, the oppressive sensation the subject receives when he/she is placed in a homogeneous magnetic field space 50 is reduced because of the expanded upper region of the space where the devices 1 oppose each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a structure of a magnetic resonance imaging apparatus that reduces a subject's feeling of pressure.

  Magnetic resonance imaging apparatuses (MRI apparatuses) are classified into a horizontal magnetic field cylindrical type and a vertical magnetic field opposing type as a method for generating a static magnetic field.

  In the horizontal magnetic field method, the subject feels pressure because he enters a tunnel having a diameter of about 600 mm and a length of about 1500 to 1800 mm.

  On the other hand, in the vertical magnetic field method, as described in Patent Document 1, a measurement space is formed by the upper surface of the examination table on which the subject is placed and the lower surface of the ceiling (upper and lower magnets), and the side surface side of the measurement space. The inspection table and the ceiling are connected by the support.

  With the configuration as described in Patent Document 1, the open portion of the side surface of the measurement space is enlarged, and the pressure feeling in the side surface direction of the subject is suppressed, and the approach to the examination table such as a doctor is facilitated. be able to.

Japanese Patent No. 2774777

  However, in the technique described in the above-mentioned Patent Document 1, the subject on the examination table is inserted into the gap between the upper and lower magnets of about 400 to 450 mm. However, in the vertical direction, the cover covering the device was approaching, so when I was lying on my back, I still felt a sense of pressure.

  For this reason, there has been a demand for a vertical magnetic field type MRI apparatus capable of reducing the feeling of pressure on the upper surface side of the examination table.

  An object of the present invention is to realize a magnetic resonance imaging apparatus capable of reducing a feeling of pressure on the upper surface side of a subject who enters an examination space.

  In order to achieve the above object, the present invention is configured as follows.

  (1) A magnetic resonance imaging apparatus is arranged so as to face each other in the vertical direction, and a pair of static magnetic field generation means for forming a uniform magnetic field region between the opposed arrangements, and mutually facing surfaces of the pair of static magnetic field generation apparatuses A pair of gradient magnetic field coils and a pair of high-frequency magnetic field coils that are arranged opposite to each other with the uniform magnetic field region interposed therebetween, and a bed that conveys the subject within the uniform magnetic field region.

  In the magnetic resonance imaging apparatus, on the surface of the pair of static magnetic field generating units on the side of the uniform magnetic field region, first depressions for accommodating the gradient magnetic field coil and the high frequency magnetic field coil are formed, respectively, and the upper side A notch is formed on the upper surface of the static magnetic field generating means arranged on the side of the uniform magnetic field region along the subject conveyance direction of the bed.

    By this depression, the upper space area where the subject is arranged can be enlarged, and the feeling of pressure can be reduced.

  Moreover, the notch expands the space area where the subject is placed, and can further reduce the feeling of pressure.

  (2) Preferably, in the above (1), the gradient magnetic field coil has a shape corresponding to a first depression and a notch formed on the upper surface of the static magnetic field generating means on the uniform magnetic field side.

  (3) Preferably, in the above (2), the high-frequency magnetic field coil has a shape corresponding to a first depression and a notch formed on an upper surface of the static magnetic field generating means on the uniform magnetic field region side. Formed.

  (4) A pair of static magnetic field generating means which are arranged opposite to each other in the vertical direction and form a uniform magnetic field region between the opposing arrangements, and the uniform magnetic field region on the mutually opposing surface side of the pair of static magnetic field generators In the magnetic resonance imaging apparatus, comprising: a pair of gradient magnetic field coils and a pair of high-frequency magnetic field coils that are arranged opposite to each other with a bed interposed therebetween; and a bed that conveys the subject within the uniform magnetic field region. On the surface on the uniform magnetic field region side, first depressions for accommodating the gradient magnetic field coil and the high frequency magnetic field coil are formed, respectively, on the upper surface on the uniform magnetic field region side of the static magnetic field generating means arranged on the upper side. A second depression is formed.

  (5) Preferably, in the above (4), the gradient magnetic field coil has a shape corresponding to the first and second depressions formed in the static magnetic field generating means.

  (6) Preferably, in (4), the high-frequency magnetic field coil is formed on a substrate having a shape corresponding to the first and second depressions formed in the gradient magnetic field coil.

  According to the present invention, in the MRI apparatus, it is possible to reduce the feeling of pressure on the upper surface side of the subject who has entered the examination space, and to suppress unnecessary movement of the subject due to the feeling of pressure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
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.

  FIG. 1 is an overall schematic configuration diagram of a magnetic resonance imaging apparatus (MRI apparatus) to which the present invention is applied.

  In FIG. 1, the MRI apparatus includes a static magnetic field generation apparatus 1, a gradient magnetic field generation system 30, a transmission system 32, a reception system 33, a signal processing system 34, a sequencer 31, and a central processing unit (CPU) 35. It has.

  The static magnetic field generator 31 generates a uniform static magnetic field around the subject 54 in the direction of the body axis or in a direction perpendicular to the body axis, and in a space having a certain extent around the subject 54. Permanent magnet type, normal conducting type or superconducting type magnetic field generating means is arranged.

  The gradient magnetic field generation system 30 includes a gradient magnetic field coil 2 wound in three axial directions of X, Y, and Z, and a gradient magnetic field power source 36 for driving each gradient magnetic field coil, and according to a command from a sequencer 31 to be described later. By driving the gradient magnetic field power source 36 of each of the coils X, Y, Z, the gradient magnetic fields Gx, Gy, Gz in the three-axis directions of X, Y, Z are applied to the subject 54. The slice plane for the subject 54 can be set by applying the gradient magnetic field.

  The sequencer 31 repeatedly applies a high-frequency magnetic field pulse that causes nuclear magnetic resonance to the atomic nuclei constituting the living tissue of the subject 54 in a predetermined pulse sequence.

  The sequencer 31 operates under the control of the CPU 35, and sends various commands necessary for collecting tomographic image data of the subject 54 to the transmission system 32, the gradient magnetic field generation system 30, and the reception system 33.

  The transmission system 32 irradiates a high-frequency magnetic field that causes nuclear magnetic resonance to the atomic nuclei constituting the living tissue of the subject 54 by the high-frequency pulse sent out from the sequencer 31. The transmission system 32 includes a high-frequency oscillator 37, a modulator 38, a high-frequency amplifier 39, and the high-frequency coil 3 on the transmission side.

  The high frequency pulse output from the high frequency oscillator 37 is amplitude-modulated by the modulator 38 in accordance with an instruction from the sequencer 31, and the amplitude-modulated high frequency pulse is amplified by the high frequency amplifier 39. Then, by supplying the amplified high-frequency pulse to the high-frequency coil 3 disposed in the vicinity of the subject 54, the subject 54 is irradiated with electromagnetic waves.

  The receiving system 33 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of the nucleus of the living tissue of the subject 54. The reception system 33 includes a reception-side high-frequency coil 3, an amplifier 40, a quadrature phase detector 41, and an A / D converter 42.

  An electromagnetic wave (NMR signal) of the response of the subject 50 due to the electromagnetic wave irradiated from the high-frequency coil 3 on the transmission side is detected by the high-frequency coil 3 disposed in the vicinity of the subject 54, and the amplifier 40 and quadrature detection. The signal is input to the A / D converter 42 via the converter 41 and converted into a digital quantity.

  Further, the signal supplied to the quadrature detector 41 is made into two series of collected data sampled by the quadrature detector 41 at the timing according to the command from the sequencer 31, and the signal is sent to the signal processing system 34.

  The signal processing system 34 includes a CPU (operation control arithmetic means) 35, a recording device such as a magnetic disk 43 and a magnetic tape 44, and a display 45 such as a CRT. The CPU 35 performs Fourier transform, correction coefficient calculation, and image reconstruction. The signal intensity distribution of an arbitrary cross section or a distribution obtained by performing an appropriate calculation on a plurality of signals is imaged and displayed on the display 45 as a tomographic image.

  2A and 2B are schematic explanatory views of a main part of an MRI apparatus according to an embodiment of the present invention, in which FIG. 2A is a front view and FIG. 2B is a side view. In FIG. 2, the pair of static magnetic field generating means constituting the static magnetic field generating device 1 is supported by the columns 46a and 46b, and is arranged to face each other in the vertical direction (ceiling side and floor surface side). 50 is formed.

  A subject (not shown) is placed in the uniform magnetic field region 50 and lies on the bed (bed) 4. The bed 4 is movable from the outside of the uniform magnetic field region 50 to the inside of the region, and carries the subject and carries it inside and outside the uniform magnetic field region 50.

  The gradient magnetic field coil 2 is formed of a pair of coils arranged opposite to each other in the vertical direction across the uniform magnetic field region 50, and is fixed between the static magnetic field generator 1 and the uniform magnetic field region 50.

  The high-frequency magnetic field coil 3 is formed of a pair of coils that are arranged to face each other in the vertical direction across the uniform magnetic field region 50, and is fixed between the uniform magnetic field region 50 and the gradient magnetic field coil 2.

FIG. 3 is a view of the static magnetic field generator 1 as viewed from the lower side in the Z-axis direction.
In FIG. 3, a circular recess 51 in which the gradient magnetic field coil 2 can be embedded is formed at the center of the surface of the static magnetic field generator 1 on the side of the uniform magnetic field region 50. The gradient magnetic field coil 2 is attached to the recess 51 of the static magnetic field generator 1, and the high frequency magnetic field coil 3 is attached so as to cover the gradient magnetic field coil 2.

  Furthermore, on the surface of the upper magnetic field generating means of the static magnetic field generating device 1 on the side of the uniform magnetic field region 50, a V-shape is formed along the insertion direction of the bed 4 (the direction in which the subject is carried in), that is, the Y direction in FIG. A notch (or depression) 52 having a shape is formed.

  FIG. 4 is a schematic outline view of the gradient coil 2. As shown in FIG. 4, the surface of the gradient magnetic field coil 2 on the side of the uniform magnetic field region 50 is cut in a V shape along the Y-axis direction (the transfer movement direction of the bed 4), similarly to the static magnetic field generator 1. A notch 52 (a notch corresponding to or continuous with the notch formed in the upper magnetic field generating means of the static magnetic field generating device 1) is formed.

  FIG. 5 is a schematic exploded perspective view of the gradient coil 2 arranged on the upper side. In FIG. 5, the gradient magnetic field coil 2 includes an X main coil 5, a Y main coil 6, and a Z main coil 7 that generate magnetic fields inclined in three directions orthogonal to each other, the X, Y, and Z axes. An X shield coil 8 that shields the magnetic field of the main coils 5, 6, and 7, a Y shield coil 9, and a Z shield coil 10 are provided.

  The X, Y, and Z main coils 5, 6, and 7 are bent in an inverted V shape so as to match the shape of the notch 52. On the other hand, the X, Y, and Z shield coils 8, 9, and 10 have a disk shape. The X and Y main coils 5, 6 are formed from two semi-disc shaped coils.

  The coils 5, 6, and 7 are molded and integrated with an epoxy resin or the like. The material of the coils 5, 6 and 7 is preferably copper, which is a good electrical conductor. As a manufacturing procedure of the coil 2, a pattern is first formed on a copper flat plate by machining such as etching and punching. The X main coil 5 is a combination of two flat coils, and these two flat coils are combined in a V shape.

  The Y main coil 6 is bent into a V shape by a bender or the like along the Y axis with respect to each of the two semicircular coils. The Z main coil 7 bends one disk-shaped coil into a V shape along the Y axis with a bender or the like.

  In this embodiment, the shield coils 8, 9, and 10 have a disk shape in order to increase the efficiency of the gradient magnetic field.

  Further, the notch 52 may be a rectangular shape such as a semi-ellipse, a semi-circle, or a quadrangle instead of a V-shape. For example, as shown in FIG. 6, the notch 52 of the X main coil 5 can be semicircular. Similarly, the notches 52 of the Y main coil 6 and the Z main coil 7 can be semicircular.

  Since the gradient magnetic field coil 2 arranged on the lower side is the same as the gradient magnetic field coil 2 shown in FIG. 5, illustration and description thereof are omitted (however, when arranged in the static magnetic field generator 1, The coils 5, 6, and 7 are V-shaped).

  FIG. 7 is a schematic outline view of the base plate 3 b of the high-frequency magnetic field coil 3. As shown in FIG. 7, the high-frequency magnetic field coil 3 is formed by bonding a copper plate processed into an arbitrary shape to a base plate 3 b processed into a V shape that is a shape corresponding to the notch 52 and connecting the copper plates. To form a coil.

  As described above, according to one embodiment of the present invention, the circular recess 51 is formed in the center of the surface of the static magnetic field generator 1 on the side of the uniform magnetic field region 50, and the V-shape is formed in the recess 51. The gradient magnetic field coil 2 and the V-shaped high-frequency coil 3 are accommodated, and the upper region of the space region where the static magnetic field generator 1 faces each other is enlarged. Thereby, when the subject is positioned in the uniform magnetic field space 50, it is possible to reduce the feeling of pressure in the upward direction.

FIG. 8 is a schematic external view of a gradient coil 2 according to another embodiment of the present invention.
The example shown in FIG. 8 is different from the example shown in FIG. 4 only in the shapes of the main coils 5 to 7, and the functions are the same.

  In the case of the example shown in FIG. 8, a rectangular notch 53 is formed on the surface of the coil 2 on the side of the uniform magnetic field region along the Z-axis direction.

  FIG. 9 is a schematic exploded perspective view of the gradient coil 2 shown in FIG. In FIG. 9, the X main coil 5 is composed of two semicircular coils, and is arranged with a distance corresponding to the notch 53 between the two coils. In addition, the Y main coil 6 is obtained by dividing the disk-shaped coil into four parts and dividing them into two coils that form a semicircular shape adjacent to each other, and a distance corresponding to the notch 53 is formed between the two coils. Provide and arrange.

  Further, the Z main coil 7 is divided into two in the Y-axis direction, each forming a semicircular coil, and a distance corresponding to the notch 53 is provided between the two coils.

  By making the gradient coil 2 in the shape as described above, a concave depression can be formed on the Y axis.

  FIG. 10 is a schematic outline view of the base plate 3 b of the high-frequency magnetic field coil 3. The high frequency magnetic field coil 3 is formed by bonding a copper plate processed into an arbitrary shape to a base plate 3b processed into a shape having a concave shape portion and two semicircular shape portions, and connecting the copper plates to each other. Form.

  Then, by arranging the gradient magnetic field coil 2 and the high frequency coil 3 shown in FIGS. 8 to 10 in the recess 51 formed in the static magnetic field generation device 1, the static magnetic field generation device 1 is opposed to each other in a spatial region. The upper region of is expanded into a concave shape. Thereby, when the subject is positioned in the uniform magnetic field space 50, it is possible to reduce the feeling of pressure in the upward direction.

  11 and 12 are diagrams showing other external shapes of the gradient coil 2. The shape shown in FIG. 11 is the coil 2 in which the conical recess 55 is formed, and the shape shown in FIG. 12 is the coil 2 in which the hemispherical recess 56 is formed.

  Here, the base plate 3b of the high-frequency magnetic field coil 3 has a shape having a recess similar to or corresponding to the gradient magnetic field coil 2 shown in FIG. 11 or FIG.

  When the gradient magnetic field coil 2 has the shape shown in FIG. 11 or FIG. 12, it is not necessary to form the notch 52 as shown in FIG.

  If the shape as shown in FIG. 11 and FIG. 12 is adopted, the gradient magnetic field coil 2 has a shape that covers the shape closer to the shape of the uniform magnetic field region 50, so that the efficiency of the gradient magnetic field coil 2 can be improved.

  FIG. 13 is a schematic exploded perspective view of the hemispherical gradient magnetic field coil 2.

  In FIG. 13, the X main coil 5 and the Y main coil 6 are configured by a combination of two coils in which a hemispherical shape is divided into two. The Z main coil 7 is composed of one hemispherical coil.

  The shape of the shield coils 8, 9, 10 is the same as that of the shield coil shown in FIG.

  Even with the gradient magnetic field coil 2 having such a shape, the same effect as the above-described example can be obtained. By enlarging the upper part of the measurement space into a hemispherical shape, it is considered that the subject's feeling of pressure can be further reduced.

  In addition, although it has illustrated so that a concave notch and a hollow shape may be formed in both of a pair of static magnetic field generation means of the static magnetic field generator 1 in this invention (FIG. 2), the lower static magnetic field generation means is Since it is hidden by the bed 4, only the upper static magnetic field generating means may be formed with a concave notch and a hollow shape.

  Further, as shown in FIG. 2, the notch 52 is formed on the carry-in side of the bed 4 of the static magnetic field generator 1, but the notch 52 is not necessarily required.

  Moreover, if the depth dimension of the hollow 51 formed in the static magnetic field generator 1 is about one half of the thickness of the static magnetic field generator 1, it is considered that a sufficient effect can be obtained.

  Furthermore, the present invention can be applied to the static magnetic field generator 1 regardless of whether it is a superconducting magnet or a permanent magnet.

1 is an overall schematic configuration diagram of an MRI apparatus to which the present invention is applied. It is a principal part schematic explanatory drawing of the MRI apparatus which is one Embodiment of this invention. It is the figure which looked at the static magnetic field generator in one Embodiment of this invention from the Z-axis direction lower side. It is a schematic external view of the gradient coil in one Embodiment of this invention. It is a general | schematic disassembled perspective view of the gradient magnetic field coil arrange | positioned above. It is a figure which shows the other example of the gradient magnetic field coil arrange | positioned above. It is a schematic external view of the base plate of a high frequency magnetic field coil. It is a schematic external view of the gradient coil in other embodiment of this invention. FIG. 9 is a schematic exploded perspective view of the gradient coil shown in FIG. 8. It is a schematic external view of the base plate of the high frequency magnetic field coil in other embodiment of this invention. It is a figure which shows the other external shape of a gradient magnetic field coil. It is a figure which shows other external shape of a gradient magnetic field coil. It is a schematic exploded perspective view of a hemispherical gradient magnetic field coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Static magnetic field generator 2 Gradient magnetic field coil 3 High frequency magnetic field coil 3b Base board 4 Bed 5 X main coil 6 Y main coil 7 Z main coil 8 X shield coil 9 Y shield coil 10 Z shield coil 30 Gradient magnetic field generation system 31 Sequencer 32 Transmission system 33 Reception system 34 Signal processing system 35 CPU
36 Gradient magnetic field power supply 37 High frequency oscillator 38 Modulator 39, 40 Amplifier 41 Quadrature detector 42 A / D converter 46a, 46b Post 50 Uniform magnetic field region 51 Recess 52, 53 Recess 55, 56 Recess

Claims (6)

A pair of static magnetic field generating means that are arranged opposite to each other in the vertical direction and form a uniform magnetic field region between the opposing arrangements, and the uniform magnetic field region sandwiched between the opposing surfaces of the pair of static magnetic field generation devices In a magnetic resonance imaging apparatus comprising a pair of gradient magnetic field coils and a pair of high-frequency magnetic field coils arranged to face each other, and a bed for carrying a subject within the uniform magnetic field region,
On the surface of the pair of static magnetic field generating means on the side of the uniform magnetic field region, first depressions for accommodating the gradient magnetic field coil and the high frequency magnetic field coil are respectively formed, and the static magnetic field generating means disposed on the upper side is formed. 2. A magnetic resonance imaging apparatus, wherein a notch is formed on the upper surface of the uniform magnetic field region along the subject conveyance direction of the bed.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the gradient magnetic field coil has a shape corresponding to a first depression and a notch formed on an upper surface of the static magnetic field generating means on the uniform magnetic field region side. Magnetic resonance imaging device.   3. The magnetic resonance imaging apparatus according to claim 2, wherein the high-frequency magnetic field coil is formed on a substrate having a shape corresponding to a first recess and a notch formed on the upper surface of the static magnetic field generating means on the uniform magnetic field region side. A magnetic resonance imaging apparatus. A pair of static magnetic field generating means that are arranged opposite to each other in the vertical direction and form a uniform magnetic field region between the opposing arrangements, and the uniform magnetic field region sandwiched between the opposing surfaces of the pair of static magnetic field generation devices In a magnetic resonance imaging apparatus comprising a pair of gradient magnetic field coils and a pair of high-frequency magnetic field coils arranged to face each other, and a bed for carrying a subject within the uniform magnetic field region,
On the surface of the pair of static magnetic field generating means on the side of the uniform magnetic field region, first depressions for accommodating the gradient magnetic field coil and the high frequency magnetic field coil are formed, respectively. A magnetic resonance imaging apparatus, characterized in that a second depression is formed on the upper surface of the uniform magnetic field region side.   5. The magnetic resonance imaging apparatus according to claim 4, wherein the gradient coil has a shape corresponding to the first and second depressions formed in the static magnetic field generating means.   5. The magnetic resonance imaging apparatus according to claim 4, wherein the high-frequency magnetic field coil is formed on a substrate having a shape corresponding to the first and second depressions formed in the gradient magnetic field coil. Resonance imaging device.

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