JP2759185B2 - Magnetic resonance imaging equipment - Google Patents

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 apparatus, and more particularly to an improvement in a magnetic circuit for forming a static magnetic field in a measurement space into which a subject is inserted.

[0002]

2. Description of the Related Art A magnetic resonance imaging apparatus is an apparatus that obtains a tomographic image at an examination site of a subject by utilizing a so-called nuclear magnetic resonance (NMR) phenomenon.

[0003] As one means for causing the NMR phenomenon in the examination region of the subject, a magnetic circuit for forming a static magnetic field in the measurement space into which the subject is inserted is provided.

This magnetic circuit has conventionally been constructed as follows.

For example, as shown in FIG.
First yoke 92A, 92 arranged opposite to each other with 1 in between
B, each of these first yokes 92A and 92B is a second yoke 93A at a portion (each corner of the first yoke) corresponding to both sides of the subject inserted in the direction of arrow α in the figure. , 93B, 9
3C, 93D, said first yoke 92A,
Disc-shaped permanent magnets 94A (not shown) and 94B are respectively provided substantially at the center of the surface of the measurement space 91B on the measurement space 91 side.
Is fixed.

[0006]

However, in the magnetic circuit configured as described above, the insertion port of the subject into the measurement space 91 is provided with the second yoke which is positioned in front of the first yoke 92A, 92B. It was determined by 93A and 93B, and the frontage was relatively narrow.

For this reason, when the subject is inserted into the measurement space 91, it is inevitable that a so-called oppressive feeling is generated. For example, this causes a great sense of anxiety for the subject with claustrophobia. .

In recent years, it is often the case that a special part of a subject is diagnosed. In this case, if the frontage of the insertion port into the measurement space 91 is narrow, a doctor or the like directly touches the subject while the doctor or the like directly touches the subject. There remains a problem that it is difficult to freely diagnose a special site in a specimen.

Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a subject without giving a feeling of oppression and for a doctor or the like to directly touch the subject. It is an object of the present invention to provide a magnetic resonance imaging apparatus capable of freely diagnosing a special site in a subject while performing the diagnosis.

[0010]

In order to achieve the above object, a magnetic resonance imaging apparatus according to the present invention comprises:
A set of magnetic field sources arranged vertically opposite to each other across a space in which a subject can be inserted, and generating a uniform magnetic field having a predetermined strength and a spatial size serving as a measurement space in the space; A set of first yokes that support each of these magnetic field sources behind the space, and are disposed between the first yokes to maintain the spacing between the set of magnetic field sources at a predetermined value. A static magnetic field generation device having a second yoke constituting a magnetic circuit with the magnetic field generation source and the first yoke, and a bed for moving the subject to the measurement space. In the magnetic resonance imaging apparatus, each of the first yokes has an external plane larger than the diameter of the magnetic field generation source when the static magnetic field generation apparatus is viewed in a plan view, and the magnetic field generation source sandwiches the magnetic field generation source. Projections with a width smaller than the diameter of the , The second yoke is located between the protruding portions of the first yoke in the vertical direction, and is erected one by one on the outside of the magnetic field source, and the measurement space is Both sides orthogonal to the facing direction of the second yoke are open to the external space. (Claim 1)

In order to achieve the above object, the present invention is arranged so as to be vertically opposed to each other across a space into which a subject can be inserted, and has a predetermined strength and spatial A set of magnetic field sources for generating a uniform magnetic field having a magnitude, a set of first yoke supporting each of these magnetic field sources behind the space, and a first yoke arranged between the first yoke. A static magnetic field generation device having a second yoke that forms a magnetic circuit with the magnetic field generation source and the first yoke while maintaining an interval between the one set of magnetic field generation sources at a predetermined value; A magnetic resonance imaging apparatus comprising: a bed for moving the subject to a space;
The yoke has a smaller outer plane than the diameter of the magnetic field source and a width smaller than the diameter of the magnetic field source on a straight line passing through the center of the magnetic field source when the static magnetic field generator is viewed in a plan view. The second yoke is formed at both ends, and the second yoke is located between the respective projections vertically opposed to each of the first yoke, and each second yoke faces the outside of the magnetic field generation source. The measurement space is erected, and both sides of the measurement space orthogonal to the facing direction of the second yoke are open to the external space. (Claim 2)

Further, in order to achieve the above object, the present invention is arranged so as to be vertically opposed to each other across a space into which a subject can be inserted, and has a predetermined strength and spatial A set of magnetic field sources for generating a uniform magnetic field having a magnitude, a set of first yoke supporting each of these magnetic field sources behind the space, and a first yoke arranged between the first yoke. A static magnetic field generation device having a second yoke that forms a magnetic circuit with the magnetic field generation source and the first yoke while maintaining an interval between the one set of magnetic field generation sources at a predetermined value; A magnetic resonance imaging apparatus comprising: a bed for moving the subject to a space;
The yoke has, when the static magnetic field generator is viewed in a plan view, one of regions divided by a first straight line passing through a center point of the magnetic field source and having an external plane larger than the diameter of the magnetic field source. A protrusion having a width smaller than the diameter of the magnetic field generation source is formed symmetrically with respect to a second straight line orthogonal to the first straight line and passing through the center of the magnetic field generation source. One between each protruding portion of the first yoke vertically opposed to each other and outside the magnetic field generation source, and the measurement space is orthogonal to the facing direction of the second yoke portion. Both sides are open to the outside space.
(Claim 3)

In the present invention, the bed of the bed is movable in the longitudinal direction, and the bed is set so that the moving direction is along a straight line orthogonal to the facing direction of the second yoke. (Claim 4)

[0014] The bed of the bed is moved in a direction in which a longitudinal direction thereof is not orthogonal to a facing direction of the second yoke, and the subject is inserted into the measurement space, (Claim 5)

[0015] Further, the projection of the first yoke of the static magnetic field generating device is formed so as to be wider from the end toward the center of the magnetic field generating source when viewed in a plan view. (Claim 6)

Further, in the magnetic resonance imaging apparatus according to claim 4, the static magnetic field generating device is covered with an envelope, and when the static magnetic field generating device is viewed in a plan view, the static magnetic field generating device has an outer periphery. A flat portion is provided along the facing direction of the second yoke, and one end in the longitudinal direction of the bed of the bed is aligned with the flat portion. (Claim 7)

[0017]

In the magnetic resonance imaging apparatus thus constructed, both ends of the first yoke in the magnetic circuit project from the magnetic field generation source and are formed with a width smaller than the diameter of the magnetic field generation source. Since the iron is erected between the protrusions of the first yoke with the magnetic field generation source interposed therebetween, and the measurement space is open on both sides in the opposite direction of the two second yoke, the measurement space Even when the subject is put in, the subject feels a better open feeling compared to the conventional device. Further, a doctor or the like can make a diagnosis while directly touching the subject through the opening.

Further, when the apparatus is viewed in a plan view, the second yoke is positioned on one side of a region divided by a straight line passing through the center of the magnetic field source, passing through the center of the magnetic field source and orthogonal to the center line. By symmetrically arranging the openings, one of the openings can be made wider than the other, which further increases the sense of openness felt by the subject and makes it easier for a doctor or the like to access the center of the measurement space from both sides of the bed.

[0019]

FIG. 1 is a perspective view showing an embodiment of a magnetic circuit provided in a magnetic resonance imaging apparatus according to the present invention.

In FIG. 1, the magnetic circuit 10 is
It has a measurement space 11 into which a subject (not shown) is inserted from the direction of the arrow α. The first yokes 12A and 12B are opposed to each other with the measurement space 11 interposed therebetween, and the first yokes 12A and 12B are supported by portions corresponding to both sides of the subject into which the first yokes 12A and 12B are inserted. And second permanent magnets 14A (not shown) and 14B fixed to substantially the center of the surface of the first yoke 12A, 12B on the measurement space 11 side. ing.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 and shows a magnetic path crossing the measurement space 11. In the figure, permanent magnets 14A opposed to each other,
The magnetic flux generated by one of the permanent magnets 14B passes through the pole piece 15B and the measurement space 11, and the magnetic pole piece 15B
A, through the permanent magnet 14A, the first yoke 12A, and further through the second yoke 13A, 13B, the first yoke 12B, and return to the permanent magnet 14B to form a magnetic circuit forming two closed loops. Has become.

Hereinafter, the first yoke 12A, 12B,
The yoke 13A, 13B, the permanent magnets 14A, 14B, etc. will be described in further detail.

The first yoke 12A, 12B each of the first yoke 12A, 12B has a plane shape, has a shape which is cut out nearly each corner of the rectangle. The first yokes 12A and 12B are arranged to face each other with the measurement space 11 interposed therebetween, and their respective major axis directions are positioned so as to be orthogonal to the insertion direction of the subject (α direction in the figure). I have.

As a result, the width of each of the first yokes 12A and 12B along the insertion direction α of the subject is reduced on both sides of the subject to be inserted.

The second yoke 13A, 13B is provided at both sides of the subject to be inserted so as to mutually support the first yoke 12A, 12B disposed opposite to each other. Is arranged.

The width of the second yoke 13A, 13B along the insertion direction α of the subject is smaller than the width of a permanent magnet 14 described later in the same direction.

That is, at the longitudinal ends of the first yokes 12A and 12B, in other words, the width along the insertion direction α of the subject at both sides of the subject to be inserted is formed small. The first yoke 12A, 1
2B is supported by the second yoke 13A, 13B.

The second yoke 13A, 13B passes through the center of the permanent magnet 14 in a plan view and the subject insertion direction α
Are positioned symmetrically with respect to a straight line orthogonal to the virtual line and passing through the center of the permanent magnet 14.

The permanent magnets 14A (not shown), 1
The 4B permanent magnets 14A and 14B each have a disk shape and are fixed to the surface of the first yoke 12A and 12B on the measurement space 11 side.

The diameters of the permanent magnets 14A, 14B are equal and are sufficiently large without protruding from the first yoke 12A, 12B.

Here, referring to FIG. 3, the first yoke 1
The respective sizes of the cross sections of the 2A, the permanent magnet 14A, and the second yoke 13A, 13B will be described. In the figure,
The width L1 of the second yoke 13A, 13B along the subject insertion direction α is approximately 50% of the width (slightly larger than the diameter of the permanent magnet 14A) L2 of the first yoke 12A in the same direction. . Then, the width T of the second yoke 13A, 13B in the direction orthogonal to the insertion direction α of the subject is taken, and T × L1
Assuming that the area determined by × 2 (since two are multiplied by two) is approximately the same as the total cross-sectional area of the second yoke of the apparatus having four second yoke shown in FIG. The characteristics are comparable to those of the conventional device. For this purpose, the first yoke 1
In some cases, the width L3 of the 2A in the direction orthogonal to the insertion direction α of the subject is larger than in the past, but this does not particularly cause any adverse effect.

Incidentally, pole pieces 15A (not shown) and 15B are respectively arranged on the surfaces of the permanent magnets 14A and 14B on the measurement space 11 side, and a gradient for forming a gradient magnetic field in the measurement space is provided. Magnetic field coils 16A (not shown) and 16B are arranged.

FIG. 4 shows an envelope 40 enclosing the magnetic circuit 10, and an insertion opening 41 into the measurement space of the envelope 40 is formed in accordance with the shape of the magnetic circuit 10. , Both sides 4 of the subject to be inserted
In 1A and 41B, it is possible to have a shape that is recessed rearward as compared with the central portion, and thus the frontage of the insertion port can be made substantially larger than in the conventional case. In addition,
In FIG. 4, a bed 42 for placing a subject is disposed in front of the insertion port 41. The bed 42 is movable in its longitudinal direction, and the subject is laid on the bed 42 at the position shown in FIG. 4, and then the bed 42 is advanced into the opening to position the affected part of the subject in the measurement space. In the arrangement shown in FIG. 4, the envelope 40 of the magnetic circuit 10 includes
In a plan view, a plane portion is formed along the direction in which the second yoke opposes, and one end of the bed 42 in the longitudinal direction is aligned with the plane portion.

According to the magnetic circuit 10 of the above-described embodiment, the width of the second yoke 13A, 13B along the subject insertion direction α is reduced and the permanent magnet 14
A and 14B are positioned on an imaginary line passing through the center of the object and orthogonal to the subject insertion direction α. And the first yoke 12
A and 12B have their widths along the subject insertion direction α reduced at locations supported by the second yokes 13A and 13B.

For this reason, the insertion opening into the measurement space 11 can have a shape in which both sides are recessed as compared with the central portion. As a result, the frontage of the insertion port becomes substantially large, so that the subject inserted into the measurement space 11 does not have a feeling of oppression, and at the same time, the first yoke 12
A doctor or the like stands on the recessed portion of A, 12B, and can easily access the affected part of the subject located in the measurement space.

Further, since the insertion opening of the measurement space 11 has a shape slightly larger in the lateral direction on both sides, the subject can be inserted from the lateral direction, in other words, the bed arrangement. The degree of freedom in the direction can be increased, and a special site in the subject can be freely diagnosed.

The shapes of the first yokes 12A and 12B and the second yokes 13A and 13B are not limited to those shown in FIG. 1, but may be various as shown in FIGS. It goes without saying that deformation can be brought about.

In each of the above embodiments, the first yoke 12A,
The planar shape of 12B is almost an octagon,
The present invention is not necessarily limited to this, and it goes without saying that each corner may be cut to form a smooth arc. In short, it is only necessary that the width of the subject along the insertion direction α be small at a position supporting the second yoke.

In the above-described embodiment, the second yoke 13
A and 13B are positioned on an imaginary line passing through the centers of the permanent magnets 14A and 14B and orthogonal to the subject insertion direction α. However, the present invention is not limited to this, and it goes without saying that it may be moved and positioned directly behind the virtual line. Even in this case, the frontage of the insertion port of the subject into the measurement space 11 can be made sufficiently large. In this case, the opening is larger at the front where the bed is arranged than at the rear, so that a doctor or the like can easily access the affected part in the center of the measurement space from the front bedside.

[0040]

As is apparent from the above description,
ADVANTAGE OF THE INVENTION According to the magnetic resonance imaging apparatus according to the present invention, a doctor or the like can freely diagnose a special part of the subject while directly touching the subject without giving a feeling of oppression to the subject.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a magnetic circuit provided in a magnetic resonance imaging apparatus according to the present invention.

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and is an explanatory diagram showing a magnetic path crossing a measurement space.

FIG. 3 is an explanatory diagram for explaining respective sizes of a first yoke, a second yoke, and a permanent magnet in the magnetic circuit shown in FIG. 1;

FIG. 4 is a perspective view showing an embodiment of an envelope including a magnetic circuit provided in the magnetic resonance imaging apparatus according to the present invention.

FIG. 5 is a plan view showing another embodiment of the magnetic circuit provided in the magnetic resonance imaging apparatus according to the present invention.

FIG. 6 is a plan view showing another embodiment of the magnetic circuit provided in the magnetic resonance imaging apparatus according to the present invention.

FIG. 7 is a plan view showing another embodiment of the magnetic circuit provided in the magnetic resonance imaging apparatus according to the present invention.

FIG. 8 is a plan view showing another embodiment of the magnetic circuit provided in the magnetic resonance imaging apparatus according to the present invention.

FIG. 9 is a perspective view showing an example of a magnetic circuit provided in a conventional magnetic resonance imaging apparatus.

[Explanation of symbols]

 11 Measurement space 12 First yoke 13 Second yoke 14 Permanent magnet

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) A61B 5/055 G01N 24/08

Claims (7)

(57) [Claims] 1. A vertical direction across a space into which a subject can be inserted.
Where the measurement space is located in the space
Generates a uniform magnetic field with constant strength and spatial magnitude
A set of magnetic field sources, and each of these magnetic field sources
A set of first yoke to be supported behind the gap;
It is arranged between the yoke and sets the interval between the pair of magnetic field sources.
And the magnetic field source and the first yoke
Magnetic field generation device having a second yoke constituting a magnetic circuit
And moving the subject to the measurement space.
In a magnetic resonance imaging apparatus including a bed,
Each of the first yoke is in a plan view of the static magnetic field generator.
In the case of having an external plane larger than the diameter of the magnetic field source,
Smaller than the diameter of the magnetic field source with the magnetic field source interposed therebetween.
Projections having a width are formed at both ends, and the second yoke is formed.
Is between each protruding portion of the first yoke which is opposed in the vertical direction.
And standing one by one outside the magnetic field source.
And the measurement space is orthogonal to the facing direction of the second yoke.
Characterized in that both sides are open to the outside space
Magnetic resonance imaging apparatus. 2. A vertical direction across a space into which a subject can be inserted.
Where the measurement space is located in the space
Generates a uniform magnetic field with constant strength and spatial magnitude
A set of magnetic field sources, and each of these magnetic field sources
A set of first yoke to be supported behind the gap;
It is arranged between the yoke and sets the interval between the pair of magnetic field sources.
And the magnetic field source and the first yoke
Magnetic field generation device having a second yoke constituting a magnetic circuit
And moving the subject to the measurement space.
In a magnetic resonance imaging apparatus including a bed,
Each of the first yoke is in a plan view of the static magnetic field generator.
In the case of having an external plane larger than the diameter of the magnetic field source,
The magnetic field is generated on a straight line passing through the center of the magnetic field source.
Projections with a width smaller than the diameter of the source are formed at both ends,
The second yoke was opposed to the first yoke in the vertical direction.
Between each protrusion, outside the magnetic field source, each one pair
The measurement space is facing the second yoke part
Both sides perpendicular to are open to the outside space
A magnetic resonance imaging apparatus comprising: 3. A vertical direction across a space into which a subject can be inserted.
Where the measurement space is located in the space
Generates a uniform magnetic field with constant strength and spatial magnitude
A set of magnetic field sources, and each of these magnetic field sources
A set of first yoke to be supported behind the gap;
It is arranged between the yoke and sets the interval between the pair of magnetic field sources.
And the magnetic field source and the first yoke
Magnetic field generation device having a second yoke constituting a magnetic circuit
And moving the subject to the measurement space.
In a magnetic resonance imaging apparatus including a bed,
Each of the first yoke is in a plan view of the static magnetic field generator.
In the case of having an external plane larger than the diameter of the magnetic field source,
By a first straight line passing through the center point of the magnetic field source
Smaller than the diameter of the magnetic field source in one of the divided areas
A projection having a width which is perpendicular to the first straight line and
Formed symmetrically about a second straight line passing through the center of the source,
The second yoke was opposed to the first yoke in the vertical direction.
Between each protrusion, outside of the magnetic field source, one stand each
And the measurement space is orthogonal to the direction in which the second yoke section faces.
Is open to the outside space on both sides.
Magnetic resonance imaging equipment. 4. The bed of the bed is movable in a longitudinal direction.
This moving direction is orthogonal to the facing direction of the second yoke.
The bed is installed along a straight line
4. The magnetic resonance imaging apparatus according to claim 1, wherein
Place. 5. The bed of the bed is arranged such that its longitudinal direction is forward.
Move in a direction that is not orthogonal to the facing direction of the second yoke and
The subject is inserted into the measurement space.
The magnetic resonance imaging apparatus according to claim 1. 6. A protrusion of a first yoke of the static magnetic field generator.
Is from the end to the center of the magnetic field source when viewed in plan.
Claims characterized in that the width is formed so wide
4. The magnetic resonance imaging apparatus according to any one of 1 to 3. 7. The static magnetic field generator is covered with an envelope.
When the static magnetic field generator is viewed from above,
A flat portion is provided on the outer periphery along the facing direction of the second yoke.
And one end of the bed of the bed in the longitudinal direction
5. The method according to claim 4, wherein the parts are aligned.
The magnetic resonance imaging apparatus according to claim 1.