JPH04132537A - Electromagnet type magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To enable imaging not only in a position of reposing on a bed but also in a standing position without limited mental affliction on a person to be inspected by connecting a first magnetic pole section magnetically to the other end of a yoke part while a second pole section is provided facing the first pole part. CONSTITUTION:A roughly U-shaped core section is made up of a yoke core 30, a first magnetic leg core 32 and a second magnetic leg core 34 and the core part and a space 48 composes a circular magnetic circuit. Then, a person 108 to be inspected is laid on his back in the space 48 as magnetic gap. With such an arrangement, an opposed space formed by the first and second magnetic pole sections 36 and 38 makes a static magnetic field generating space to allow imaging with the person 108 placed in the space 48. In this case, the first and second magnetic pole sections 36 and 38 only face each other and the other two opposed surfaces thereof are not closed. Even when the person 108 to be inspected is placed in the space 48, the person 108 to be inspected can secure a larger perspective, hence having no visual pressure.

Description

[Detailed Description of the Invention] [Object of the Invention (Industrial Application Field) The present invention relates to magnetic resonance (MR)
res.

The present invention relates to an electromagnetic magnetic resonance imaging apparatus that obtains morphological information such as a slice image of a subject (living body) and functional information such as spectroscopy by utilizing the ``nance'' phenomenon.

(Prior art) Magnetic resonance is a phenomenon in which an atomic nucleus with non-zero spin and magnetic moment placed in a static magnetic field resonantly absorbs and emits only electromagnetic waves of a specific frequency. The angular frequency ω shown in (ω.−2πν., .

niller-more frequency) ν It resonates with me.

ω. -γ B.

where γ is the gyromagnetic ratio specific to the type of atomic nucleus,
Further, B is the static magnetic field strength.

The device that performs biological diagnosis using the above principle is the J
(The electromagnetic waves of the same frequency as above, which are induced after sound absorption, are processed to produce diagnostic information that reflects information such as nuclear density, longitudinal relaxation time T3, transverse relaxation time T2, flow, chemical shift, etc.) We are trying to obtain slice images etc. non-invasively.

Collecting diagnostic information by magnetic resonance can excite all parts of a subject placed in a static magnetic field and collect signals, but there are limitations in the equipment configuration and clinical requirements for imaging images. Therefore, in an actual device, a specific part is excited and its signal is collected.

In this case, the specific region to be imaged is generally a sliced region with a certain thickness;
Magnetic resonance signals (MR multiplied signals) of echo signals and FID signals from this slice site are collected by performing a data encoding process many times, and these data groups are subjected to image reconstruction processing using, for example, a two-dimensional Fourier transform method. By doing so, an image of the specific slice region is generated.

As the static magnetic field generating means in such a magnetic resonance imaging apparatus, there are an electromagnet using a normal conducting coil or a superconducting coil such as a Helmtz type or a solenoid type, and a permanent magnet.

Here, since the magnetic field generated by a permanent magnet is several thousand Gauss at most, a high-intensity uniform magnetic field over a wide area cannot be obtained, and it cannot be applied to an apparatus for photographing a wide area or special photographing.

Therefore, electromagnets are exclusively used as static magnetic field generating means in devices for wide-area imaging or special imaging.

Note that there are two types of electromagnets: a transverse magnetic field type in which a static magnetic field is generated in the horizontal direction, and a vertical magnetic field type in which a static magnetic field is generated in the vertical direction.

FIG. 5 is a perspective view of a conventional electromagnetic magnetic resonance imaging apparatus using a transverse field type superconducting magnet as an electromagnetic static magnetic field generating means. The transverse magnetic field type superconducting magnet 100 is
It is a sealed double cylindrical body with both axial ends closed, and its longitudinal direction is, for example, the Z axis. This sealed double cylinder contains at least a superconducting coil as well as a coolant such as liquid helium that makes the coil a superconducting state.
It generates a static magnetic field in the Z-axis direction.

In addition, in the cavity] 02 of the transverse magnetic field type superconducting magnet 100,
A gradient magnetic field coil and a probe coil (not shown) are incorporated. The cavity 102 forms a subject introduction cavity. A bed 104 is arranged facing the opening of the cavity 102 of the superconducting magnet 100, and the bed 104 is provided with a slide top plate 106. This slide top plate 106
The subject 108 is placed on top. And subject 108
is inserted into the cavity 102 of the superconducting magnet 100 by the sliding operation of the slide top plate 106.

Then, when the subject 108 is placed in the cavity 102, a static magnetic field is generated, and the gradient magnetic field by the gradient magnetic field coil and the excitation high-frequency magnetic field by the probe coil are superimposed on the static magnetic field. As a result, a magnetic resonance phenomenon occurs in a specific region of the subject 108, and a magnetic resonance signal is induced along with the phenomenon. This induced magnetic resonance signal is collected by the probe head, and an image is reconstructed by a computer system (not shown).

(Problems to be Solved by the Invention) In the conventional electromagnetic magnetic resonance imaging apparatus described above, the subject 108 is inserted into the narrow, deep, and dimly lit cavity 102 for several minutes to several tens of minutes. Because it restrains the patient 108 for a long time, the mental pain suffered by the subject 108 is often compared to X@
It is larger than a CT scanner device.

In addition, in the conventional electromagnetic magnetic resonance imaging apparatus described above, the subject 108 is inserted into the cavity 102 and imaged, so the subject 108 lies down or on his back (recumbent position) and his whole body is Photography is only possible when the camera is fully extended. Therefore, there is a problem in that it is usually not possible to image the lumbar region of a person in an active state, that is, in a standing position, which is a state in which stress is applied to the vertebrae and spinal cord. Note that although the above description has been made regarding the transverse magnetic field type, the situation is almost the same for the vertical magnetic field type.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electromagnetic magnetic resonance imaging apparatus that causes less mental pain to the subject and allows imaging not only in the lying position but also in the standing position.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following measures are taken to solve the above-mentioned RW1 and achieve the objects.

That is, the present invention produces a magnetic resonance phenomenon in a specific part of the subject by placing the subject in a static magnetic field generated by an electromagnetic static magnetic field generating means and superimposing a gradient magnetic field and an excitation high-frequency magnetic field. In an electromagnetic magnetic resonance imaging apparatus that obtains diagnostic information by collecting magnetic resonance signals induced by the phenomenon, the electromagnetic static magnetic field generating means includes a static magnetic field generating coil and a magnetic field generated by the static magnetic field generating coil. a yoke part that is inserted in the longitudinal direction along the direction of the static magnetic field; a first magnetic pole part that is magnetically coupled to one end of the yoke part; and a first magnetic pole part that is magnetically coupled to the other end of the yoke part. It is characterized in that it is composed of a second magnetic pole part that is coupled and faces the first magnetic pole part.

(Function) According to such a configuration, the facing space between the first magnetic pole part and the second magnetic pole part becomes a static magnetic field generation space, and a subject can be placed in this space and photographed. In this case, the first magnetic pole part and 1@
It only faces the magnetic pole part 2 and does not cover the other two facing faces. Therefore, even when the examinee is placed in the space, the examinee's line of sight is largely secured;
There is no visual pressure.

Furthermore, for the same reason, the subject can be placed in the space not only in a recumbent position but also in a standing position, which increases the degree of freedom of the imaging site.

(Embodiment) An embodiment of the electromagnetic magnetic resonance imaging apparatus according to the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a sectional view of an embodiment of the device. In FIG. 1, an electromagnetic static magnetic field generator 10 is, for example, a magnetic resonance imaging device MRT-50A (0
, 57) and MRT-200 (1.5T or more) are typical examples of superconducting magnets.

This electromagnetic static magnetic field generator WL (hereinafter referred to as "superconducting magnet")
It is called. ) 10 is a vacuum container 12 which is a sealed double cylindrical body with both axial ends closed, a shield container 14 disposed within this vacuum container 12, and this rolled container 14.
It is a triple container structure consisting of a helium container 16 placed inside. Then, the vacuum container 12 and the shield container 14
A thermally insulating material 18 is housed between the thermally shielding container 14 and the helium container 16, and another type of thermally insulating material 20 is stored between the thermally shielding container 14 and the helium container 16. A superconducting coil 22 in which a superconducting conductor is wound in a solenoid style and liquid helium 24 are housed. Koni,
Thermal shield container] 4 is cooled by an externally attached refrigerator 26.

Further, the static magnetic field generation space 28 of the superconducting magnet 10 is formed along the static magnetic field generation direction, and in this space 28, in the above-mentioned magnetic resonance imaging apparatus M RT-50A, a gradient magnetic field coil and a whole-body A probe coil for this purpose is installed. In this embodiment, this space 2
A yoke core 30 made of a highly magnetic material is inserted through 8.

Further, a first magnetic leg core 32 also made of a highly magnetic material is magnetically coupled to one end of the yoke core 30 at a substantially right angle, and a second magnetic leg core 32 also made of a highly magnetic material is connected to the other end. The magnetic leg cores 34 are magnetically coupled at approximately right angles. The first magnetic pole part 36 is formed at the end of the first magnetic leg core 32 that is not coupled to the yoke core 30, and the end of the second magnetic leg core 34 that is not coupled to the yoke core 30. A second magnetic pole portion 38 is formed. A first pole piece 40 and a gradient magnetic field coil 42 for adjusting magnetic lines of force are disposed at the end of the first magnetic pole part 36, and
At the end of the second magnetic pole section 38, a second pole piece 44 and a gradient magnetic field coil 46 are also arranged for adjusting the lines of magnetic force.

The first magnetic pole part 36 (for example, N pole) and the second magnetic pole part 38 (
For example, the S pole) is opposed by its magnetic pole surface (substantially the surface of the pole piece 40.44, but in the drawing it is the surface of the gradient magnetic field coil 42.46). The space between the opposing surfaces 48 is a magnetic gap, which is a static magnetic field generation space.

With the above configuration, the yoke core 30. First magnetic leg core 32. ji! The two magnetic leg cores 34 form a substantially U-shaped core, and the core and the space 48 constitute a circular magnetic circuit.

Then, the subject 108 is placed on his back in the space 48, which is a magnetic gap, via the top plate of a bed (not shown), and for example, a saddle-shaped probe coil 50 is placed. In the example of FIG. 1, a saddle-shaped probe coil 50 is used, but the present invention is not limited to this, and a surface coil or a solenoid coil can be used. Here, with respect to the origin O, the Y-axis direction is a vertical direction, the X-axis direction is a horizontal direction shown on the left and right sides of the paper, and the Z-axis direction is a horizontal direction shown on the top and bottom of the paper. Therefore, the generation direction of the static magnetic field is the X-axis direction, the line of sight direction of the subject 108 is the Y-axis direction, and the body axis direction of the subject 108 is the Z-axis direction.

An example of a combination of a static magnetic field and a probe coil will be described below with reference to FIGS. 2A, 2B, and 2C. That is, it is an essential condition from the principle of magnetic resonance phenomena that the static magnetic field B and the magnetic field B generated by the probe coil be orthogonal to each other. Therefore, the following example is a typical combination of a static magnetic field and a probe fill. In the case of a saddle type probe coil 50 as shown in FIG. 2A, in the case of a surface coil type probe coil 52 as shown in FIG. 2B, the second C
A typical example is a solenoid type probe coil 54 as shown in the figure.

According to the apparatus of this embodiment configured as described above, the facing space 48 formed by the first magnetic pole part 36 and the second magnetic pole part 38 becomes a static magnetic field generation space, and the subject is placed in the space 48. You can also set up the 108 and take pictures. In this case, the first magnetic pole part 36 and the second magnetic pole part 38 only face each other and do not cover the other two facing faces. In other words, subject 1
The field of view of 08 is blocked by the first magnetic pole part 36 and the second magnetic pole part 38 in the X-axis direction, and is slightly obstructed by the conductor of the probe coil 54 in the Y-axis direction. However, it is mostly open,
Furthermore, it is open in the Z-axis direction.

Therefore, even when the subject 108 is placed in the space 48, the subject 108 has a good line of sight and does not feel visually oppressed.

Also, for the same reason, the subject 108 is placed in the space 48 for ¥S.
Since the device can be placed not only in the lying position as shown in Figure 1, but also in the standing position, the degree of freedom in selecting the part to be imaged increases. Therefore, it is possible to image the lumbar region in a standing position, which is a state in which a person is normally active, that is, in a state in which stress is applied to the vertebrae and spinal cord, which is clinically advantageous. Note that the subject 108 who is in a lateral recumbent position is in a supine or prone position with his or her body stretched out on the top plate of a tower table (not shown).

On the other hand, in the case of a standing state, the subject 108 assumes a posture in which the subject 108 raises his or her upper body on the top plate of a bed (not shown), or assumes a posture in which the patient 108 stands up, excluding the bed (not shown).

Figure 3 shows a test subject 10 using a reclining chair.
FIG. 8 is a perspective view showing a specific example of an apparatus that can arbitrarily set the lying position and the standing position of No. 8 to take images. As shown in FIG. 3, a reclining chair 56, preferably all of which is made of non-magnetic material, is placed in the space 48, and the subject 108 is placed on the chair 56. chair 56
Lying position by adjusting the recline of the
Both the leaning state and the standing state can be set arbitrarily. Moreover, the surface coil 52 can also be fixedly installed on the chair 56.

In the embodiment apparatus shown in FIGS. 1 and 3, the superconducting magnet 10 is placed at the bottom in the vertical direction (Y-axis direction), and the space 48 that can be used for imaging is placed at the top in the vertical direction (Y-axis direction). It has a layout configuration. For example, this can be laid out as follows. That is, the magnetic pole 36.
38 and a space 48 are placed in a photographing room (not shown), and a superconducting magnet]0 is placed under the floor of the photographing room (not shown). This layout allows the equipment to be installed with less floor space in the photography room. Further, by installing the superconducting magnet 10, which is a large and heavy electrical device, in a place out of sight of the subject 108, the feeling of pressure that the subject 108 may feel is reduced.

FIG. 4 is a perspective view showing an example of a layout different from that of FIG. 3 (or FIG. 11). That is, in the embodiment shown in FIG. 4, the superconducting magnet 10 is placed deep in the horizontal direction (Z-axis direction), and the space 48 that can be used for photographing is placed in the horizontal direction (Z-axis direction).
The arrangement is such that it is placed at the front in the axial direction. For example, this can be laid out as follows. That is, the magnetic poles 36, 38 and the space 48 are placed in a photographing room (not shown), and the superconducting magnet 10 is placed in a room next to the photographing room (not shown). With this layout, the floor area of the photographing room can be reduced to accommodate more equipment. Further, as described above, by installing the superconducting magnet [0], which is a large and heavy electrical device, out of sight of the subject 108, the feeling of pressure that the subject 108 may feel is reduced.

In the above example, the superconducting magnet 10, which is a triple container structure with a refrigerator, is used, but the superconducting coil and liquid helium are stored directly in a vacuum container without using a refrigerator. A superconducting magnet may be used, and various kinds of superconducting magnets can be used.

Moreover, it goes without saying that a normal conducting magnet may be used. Furthermore, the illustrated example shows a high magnetic field electromagnet, or it may be a small electromagnet with a low static magnetic field strength.

On the other hand, the format and arrangement of gradient magnetic field coils and probe coils are not similarly specified.

Of course, the same applies to beds and chairs.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, the electromagnetic static magnetic field generating means of the present invention includes a static magnetic field generating coil and a yoke that is inserted in the longitudinal direction along the direction of the static magnetic field generated by the static magnetic field generating coil. a first magnetic pole part that is magnetically coupled to one end of the yoke part, and a second magnetic pole that is magnetically coupled to the other end of the yoke part and faces the first magnetic pole part. Since the space where the first magnetic pole part and the second magnetic pole part face each other becomes a static magnetic field generation space, a subject can be placed in this space and imaged. In this case, the first magnetic pole part and the second magnetic pole part only face each other and do not cover the other two facing faces. Therefore, even when the subject is placed in the space, the subject's visibility is greatly ensured and there is no visual pressure.

Furthermore, for the same reason, the subject can be placed in the space not only in a lying position but also in a standing position, so that the degree of freedom of the imaging site can be increased.

Therefore, according to the present invention, it is possible to provide an electromagnetic magnetic resonance imaging apparatus that causes less mental pain to the subject and allows imaging not only in the lying position but also in the standing position.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an embodiment of an electromagnetic magnetic resonance imaging apparatus according to the present invention, FIG. 2A, and FIG. 2B.
Figure 2C is a diagram showing the relationship between the static magnetic field and the magnetic field created by the probe coil, Figures 3 and 4 are perspective views showing an example of the layout of the device shown in Figure 1, and Figure 5 is a diagram showing the conventional example. FIG. 10... Superconducting magnet, 30... Yoke core, 32° 34... Magnetic leg core, 36.38... Magnetic pole part, 40° 44... Pole piece, 42.46... Gradient magnetic field Coil, 48...Magnetic gap, 50...Probe coil, 56...Rikunining chair. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] By placing the subject in a static magnetic field generated by an electromagnetic static magnetic field generating means and superimposing a gradient magnetic field and a high-frequency magnetic field for excitation, a magnetic resonance phenomenon is caused in a specific part of the subject, and the phenomenon is accompanied by the phenomenon. In an electromagnetic magnetic resonance imaging apparatus that obtains diagnostic information by collecting induced magnetic resonance signals, the electromagnetic static magnetic field generating means includes a static magnetic field generating coil and a static magnetic field generated by the static magnetic field generating coil. a yoke portion through which the longitudinal direction thereof is inserted; a first magnetic pole portion magnetically coupled to one end portion of the yoke portion; and a first magnetic pole portion magnetically coupled to the other end portion of the yoke portion. An electromagnetic magnetic resonance imaging apparatus comprising a magnetic pole part and a second magnetic pole part facing each other.