JP3098214B2 - Magnetic resonance imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 of a subject to be examined using 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 opposed to each other with 1 in between
B, and these first yokes 92A, 92B are provided at the portions (each corner of the first yoke) corresponding to both sides of the subject inserted in the direction of the arrow α in the figure (the second yoke 93A). , 93B, 9
3C, 93D, the first yoke 92A,
Disc-shaped permanent magnets 94A (not shown) and 94B are provided at substantially the center of a surface of the measurement space 91 on the side of the measurement space 91B.
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 positioned in front of the first yoke 92A, 92B. 93A and 93B, 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 static magnetic field generating means for forming a measuring magnetic field in the measuring space and forming a static magnetic field in the measuring space to form a measuring space for measuring the subject, and for inserting the subject lying in the static magnetic field space; In a magnetic resonance imaging apparatus having a bed, the static magnetic field generating means includes an upper static magnetic field generator including a static magnetic field source arranged above the subject to generate a static magnetic field, and the subject. A lower static magnetic field generator including a static magnetic field generating source for generating a static magnetic field disposed opposite to the upper static magnetic field generator, and the upper static magnetic field generator disposed one by one beside the subject; And a supporting means for supporting the lower static magnetic field generating device, wherein the supporting means is formed of a column or a prism having a width smaller than an outer diameter of the static magnetic field generating source, and a center of the two supporting means. The first through In which virtual line is as is disposed behind the second imaginary line perpendicular to the center the street the subject insertion direction of the static magnetic field space.

In the magnetic resonance imaging apparatus thus configured, the support means in the magnetic circuit is constituted by a cylinder or a prism having a width smaller than the outer diameter of the static magnetic field generating source, and the first means passing through the centers of the two support means. Is located behind the second imaginary line passing through the center of the static magnetic field generation source and orthogonal to the subject insertion direction, the opening can be enlarged, the feeling of opening for the subject can be increased, and the doctor It becomes easy to access the subject such as.

When the apparatus is viewed in a plan view, the support means is provided on one side of a region divided by a straight line passing through the center of the static magnetic field generating source, at right angles to the center line passing through the center of the static magnetic field generating source. The opening can be made wider than the other by symmetrically arranging the opening, so that the subject feels more open and the doctor can easily access the center of the measurement space from both sides of the bed.

[0013]

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 arranged to face each other with the measurement space 11 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 two permanent magnets 14A (not shown) and 14B fixed at 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 in FIG. 1 and shows a magnetic path crossing the measurement space 11. In the same figure, opposed permanent magnets 14A, 1
The magnetic flux generated by one of the permanent magnets 14B of 4B is
The pole piece 15B passes through the measurement space 11, and the pole piece 15A,
The magnetic circuit forms two closed loops that pass through the permanent magnet 14A, the first yoke 12A, pass through the second yoke 13A, 13B, and the first yoke 12B, and return to the permanent magnet 14B. I have.

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

A 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 so as to face each other with the measurement space 11 therebetween, and their major axis directions are positioned so as to be orthogonal to the insertion direction of the subject (the 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.

In other words, at the longitudinal ends of the first yokes 12A and 12B, in other words, the width along both sides of the inserted subject along the inserting direction α of the subject is formed to be 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 permanent magnets 14A and 14B have the same diameter and are sufficiently large without protruding from the first yoke 12A and 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.

On the surfaces of the permanent magnets 14A and 14B on the measurement space 11 side, pole pieces 15A (not shown) and 15B are arranged, respectively, 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 port 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 in which it 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 located 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 side direction on both sides, the subject can be inserted from the side 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 yoke 12A, 12B and the second yoke 13A, 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 a virtual 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.

[0034]

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 the 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 Continuation of front page (56) References JP-A-1-146530 (JP, A) JP-A-62-295405 (JP, A) JP-A-2-21846 (JP, A) Patent 2759185 (JP, A) B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) A61B 5/055

Claims (1)

(57) [Claims] 1. A measurement space for measuring a subject is formed.
And generate a static magnetic field in the measurement space to form a static magnetic field space.
A static magnetic field generating means, and
Magnetic resonance image having a bed for inserting a subject
In the zing apparatus, the static magnetic field generating means includes
Static magnetic field generation for generating a static magnetic field placed on the upper part of the body
An upper static magnetic field generator including a source, and the subject
A static magnetic field is generated by being arranged opposite to the upper static magnetic field generator.
A lower static magnetic field generator including a static magnetic field source for
The upper static magnetic field generator is arranged one by one on the side of the subject.
Supporting means for supporting a raw device and the lower static magnetic field generating device
And the support means is provided outside the static magnetic field generation source.
It is composed of a cylinder or prism with a width smaller than the diameter, and the two
A first imaginary line passing through the center of the support means is the static magnetic field space.
Of the second virtual axis passing through the center of
Magnetic resonance characterized by being arranged behind a line
Imaging device.