JP3469436B2 - Split type magnetic field generator for MRI - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a split-type magnetic field generator for MRI used in a nuclear magnetic resonance tomography apparatus (hereinafter referred to as MRI).

[0002]

2. Description of the Related Art FIG. 5 shows, for example, JP-A-6-176917.
FIG. 3 is an external view of a conventional split type MRI magnetic field generation device (hereinafter, may be simply referred to as a magnetic field generation device) described in Japanese Patent Publication No. In the figure, reference numeral 100 denotes a magnetic pole device, which is composed of a superconducting coil 101 and a magnetic pole piece 102 of a ferromagnetic material. The magnetic pole device 100 has its axis vertical as shown in FIG.
The pieces are arranged so as to face each other. A uniform magnetic field is generated in the imaging space 103 formed in the middle of the pair of magnetic pole devices, and the subject (patient) is placed there.

In MRI, a gradient magnetic field generator for obtaining position information and an RF coil (high-frequency transmitting and receiving coils) are arranged in the middle of a pair of magnetic pole devices to obtain distribution information of specific atomic nuclei in a desired cross section of a subject. Then, a tomographic image is generated. Required space for arranging the subject, RF coil, and gradient magnetic field generator (for example, as a gradient magnetic field generator, see Japanese Patent Application Laid-Open No.
The space between the magnetic pole devices is set according to the size of the device (see Japanese Patent Publication No. 14900).

FIG. 6 is a sectional view showing a main part of another conventional magnetic field generator. It does not use ferromagnetic pole pieces to reduce the weight of the device. In the figure,
110 is a magnetic pole device, which is configured as follows.
Reference numeral 111 denotes a cryogenic container having a rectangular section and an annular shape centered on the Z axis, 112 denotes a coil assembly, and an annular side coil 112a having a rectangular section and centered on the Z axis, and second to fifth coils 112b. ˜112e. Reference numeral 114 is a disk-shaped gradient magnetic field generator, 115 is a flat-plate high-frequency transmission coil (hereinafter may be simply referred to as a transmission coil), and 116 is a flat-plate high-frequency reception coil (hereinafter may be simply referred to as a reception coil). Is.

The magnetic pole device 110 configured as described above.
Are paired and face each other in the Z-axis direction. The two magnetic pole devices 110 are provided with a facing distance J between the receiving coils 116 to secure a space for the subject. The facing distance between the side coils 112a at this time is H. A uniform magnetic field is generated in the imaging space formed in the middle of the pair of magnetic pole devices, and the subject (patient) is placed there.

In order to give the subject a feeling of openness, it is desirable that the subject arrangement space is large, and a large gap between the magnetic pole devices is required. Further, a large magnetic field output is desired in order to improve the resolution of the tomographic image. Therefore, the magnetic pole device 110 tends to be large.

As the gap between the magnetic pole devices 110 increases, the magnetomotive force required by the magnetic pole devices inevitably increases. Figure 7
For the magnetic field generator of FIG.
2 is a graph showing the relationship between 2) and magnetomotive force [AT]. The central magnetic field is 0.5 [T]. In FIG. 7, the symbol H is the coil spacing including the imaging space, and the horizontal axis is graduated based on H / 2. It should be noted that a non-shield type (denoted by symbol N / S) that does not have a shield coil and the magnetic field of the device leaks to the outside, and an active shield type (symbol A / S that has a shield coil for suppressing leakage to the outside). (Indicated by) are shown.

From FIG. 7, the required magnetomotive force is the non-shield type N
It can be seen that in both / S and active shield type A / S, the coil spacing is proportional to approximately the fifth power.

[0009]

As described above, in the conventional magnetic field generator, when the distance between the magnetic pole devices facing each other, that is, the interval between the coil assemblies facing each other, is increased, the required magnetomotive force is remarkably increased and the coil is enlarged. However, there is a problem that the price and the weight are increased.

An object of the present invention is to realize a split type MRI magnetic field generator which has a small required magnetomotive force and is small in size and inexpensive.

[0011]

In order to achieve the above object, in the split type MRI magnetic field generator of the present invention, a coil assembly is housed and a predetermined space is provided in the axial direction of the coil assembly. Low temperature arranged facing each other at intervals
In this configuration, a concave arrangement space for accommodating a flat-plate gradient magnetic field generating coil is formed in each of the mutually opposing portions of the coil accommodating container for use. With this configuration, the flat-plate-shaped gradient magnetic field generating coil can be accommodated in the concave arrangement space, and the facing interval between the coil accommodating containers can be narrowed by that much, so that the magnetomotive force for generating the predetermined magnetic field is reduced. Get smaller.

Then, a flat plate-shaped predetermined coil in the coil assembly is housed inside a portion of the coil accommodating container that surrounds the recessed layout space, and the predetermined flat plate-shaped coil is arranged in a concave shape. Along with the plate-shaped gradient magnetic field coil, it is arranged so as to surround the plate-shaped gradient magnetic field coil housed in the space.
It is a flat plate as a whole .

Further, a flat-plate gradient magnetic field generating coil is housed in the concave arrangement space.

Further, the concave arrangement space, a flat high-frequency transmission coil in addition to the flat plate-like gradient magnetic field generating coil Rights
At least one of the plate-shaped high-frequency receiving coil
A flat plate as a whole with a flat plate-shaped gradient coil
It is the one.

A flat-plate gradient magnetic field generating coil is housed in the concave arrangement space, and a high frequency transmitting coil and a high frequency receiving coil are arranged outside the concave arranging space. Since the high-frequency transmitting coil and the high-frequency receiving coil are arranged outside the concave arrangement space, they can be easily visually recognized and are also outside the concave arrangement space, so that the position and orientation adjustment work becomes easy.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a sectional view showing a main part of a magnetic field generator showing an embodiment of the present invention. In the figure, 10 is a magnetic pole device, which is configured as follows. Reference numeral 11 denotes a cylindrical cryogenic container, a detailed configuration of which is not shown in the drawing, but a vacuum chamber, two heat radiation shields of 80 [K] and 20 [K],
It is composed of a liquid helium tank or the like, and houses a superconducting coil assembly 12 described later. The cryogenic container 11 has an annular convex portion 11a centered on the Z axis having a rectangular cross section, which is provided at a predetermined height so as to project at a peripheral edge portion of the facing surface on the side of the subject arrangement space, that is, on the side where the cryogenic containers 11 face each other. Have. Annular convex portion 11
A has an annular housing portion 11b with a rectangular cross section formed inside. In addition, the sidewall 1 on the inner peripheral side (axis Z side) of the convex portion 11a
A recess 11d is formed surrounded by 1c. The vacuum tank and the liquid helium tank of the cryogenic container 11 are manufactured by welding non-magnetic stainless steel plates.

Reference numeral 12 denotes a coil assembly, each of which is an annular side coil 12a having a rectangular cross section and having the Z axis as its center.
It has the 2nd coil 12b, the 3rd coil 12c, and the 4th coil 12d. The coil assembly 12 is a cryogenic container 11
And is cooled and maintained at a temperature indicating superconductivity. Each of the coils 12a to 12d is wound around an annular winding frame having a U-shaped cross section, but the winding frame is not shown. Reference numeral 14 is a gradient magnetic field generating device, 15 is a transmitting coil, and 16 is a receiving coil. In this embodiment, the gradient magnetic field generating device 14, the transmitting coil 15, and the receiving coil 16 are integrally fixed with a synthetic resin. And the whole is shaped like a disc. The integrated gradient magnetic field generator 14, the transmitter coil 15, and the receiver coil 16 are housed in the recess 11d formed by the annular protrusion 11a so as not to project beyond the protrusion 11a.

The magnetic pole device 10 is constructed as described above, and the magnetic pole devices 10 of the same size are paired and arranged so as to face each other with a space J as shown in the drawing in the Z-axis direction to form a split type magnetic field generator. is doing. In addition, in order to reduce the weight in this magnetic field generator, the magnetic pole pieces are not provided.

As described above, the gradient magnetic field generating device 14, the transmission coil 15 and the reception coil 16 which are integrated are formed in the recess 11
Since the convex portion 11a is protruded by a predetermined height so that the whole of the magnetic pole device 10 can be accommodated in d, the facing distance between the magnetic pole devices 10 can be reduced accordingly. Especially, the side coil 1
Since the facing distance between the two a can be made small, the required magnetomotive force of the coil assembly 12 may be small. Therefore, the coil assembly 12 can be downsized, and the magnetic field generator can be downsized. Of course, the integrated gradient magnetic field generator 1
4, the transmitting coil 15 and the receiving coil 16 may not be completely housed in the recess 11d, but a part may be out of the recess 11d.

The side coil 12a supplies, for example, about 70% of the required total magnetomotive force, and the second to fourth coils 12b to 12d supply the remaining magnetomotive force. Total number of coils of coil assembly 12 and side coil 1
The relative positional relationship between the second coil 12a and the second coil 12b to the fourth coil 12d is different from the conventional one shown in FIG. 7, but the required strength can be obtained by appropriately setting the position of each coil and the sharing of the magnetomotive force. And a magnetic field of homogeneity can be generated.

Embodiment 2. FIG. 2 is a sectional view showing a main part of a magnetic field generator showing another embodiment of the present invention. In this embodiment, the gradient magnetic field generator 24 and the transmission coil 2 which are separate bodies are provided in the recess 11d formed by the projection 11a.
5, the receiving coil 26 is housed. The gradient magnetic field generation device 24, the transmission coil 25, and the reception coil 26 are plate-shaped by fixing a coil conductor (not shown) made of a copper plate with synthetic resin, and the gradient magnetic field generation device 24 is a disc-shaped transmission coil 25. Is a rectangle smaller than the gradient magnetic field generator 24, and the receiver coil 26 is a rectangle smaller than the transmitter coil 25. The transmission coil 25 is fixed to the gradient magnetic field generator 24, and the reception coil 26 is fixed to the transmission coil 25.

Note that the gradient magnetic field generator 24, the transmission coil 25, and the reception coil 26 are shown with a distance larger than the actual distance for convenience of illustration. As described above, the magnetic pole device 2
0 is configured so that the receiving coils 26 face each other at a distance J.

The other parts of the configuration are the same as those shown in FIG. 1, so the corresponding parts are designated by the same reference numerals and the description thereof is omitted.

As described above, the gradient magnetic field generator 24, the transmission coil 25, and the reception coil 26 are separately formed and assembled in the recess 11d, so that the position and the posture can be individually moved, and the adjustment is easy. Is.

Embodiment 3. FIG. 3 is a sectional view showing a main part of a magnetic field generator according to another embodiment of the present invention. In this embodiment, the magnetic pole device 30 is configured as follows. The gradient magnetic field coil 34 and the transmission coil 35 are housed in the recess 31d formed by the side wall 31c of the projection 31a of the cryogenic container 31, and the reception coil 36 is arranged outside thereof. A part of the side coil 32a of the coil assembly 32 is housed in the housing portion 31b of the convex portion 31a. This magnetic pole device 30
The magnetic field generator is configured such that the receiving coils 36 are axially opposed to each other so that the distance between them is J. In this case, the interval between the coil assemblies 32 facing each other becomes slightly larger than that in the embodiment of FIG. 2, but by making the coils 32a to 32d according to that, a predetermined strength can be obtained at a predetermined place. It is possible to generate a magnetic field of uniform and uniform.

In this way, the receiving coil 36 is formed in the recess 31d.
By arranging it outside of, you can see it from the outside when you want to adjust the position of the receiving coil according to the subject.
In addition, the adjustment work is easy because it can be handled outside the recess 31d.

Fourth Embodiment FIG. 4 is a sectional view showing a main part of a magnetic field generator according to still another embodiment of the present invention. In this embodiment, the magnetic pole device 40 is configured as follows. The gradient magnetic field coil 44 is housed in the concave portion 41d formed by the side wall 41c of the convex portion 41a of the cryogenic container 41.
5 and the receiving coil 46 are arranged outside thereof. The side coil 42a of the coil assembly 42 is arranged in the housing portion 41b of the convex portion 41a. The magnetic pole devices 40 are arranged so as to face each other in the axial direction so that the facing distance between the receiving coils is J, thereby forming a magnetic field generator. In this case, the interval between the coil assemblies 42 facing each other is slightly larger than that in the embodiment of FIG. 2, but by making each of the coils 42a to 42d corresponding thereto, the magnetic field at a predetermined location can be set to a predetermined value. Can be strength and uniformity.

As described above, by arranging both the transmitting coil 45 and the receiving coil 46 outside the recess 41d,
When it is desired to adjust the positions and postures of the transmission coil 45 and the reception coil 46 according to the subject, they can be seen from the outside and can be handled outside the recess 41d, so that the adjustment work is easy.

As described above, according to each of the embodiments of the present invention, the facing distance between the coil assemblies 12, 32, 42, particularly the outermost side coils 12a, 32a, 42a, can be reduced. The required magnetomotive force of the coil assembly can be reduced. According to the graph of FIG. 7, for example, in the magnetic field generator of the active shield type A / S, the coil interval H is set from 375 × 2 = 750 [mm] to 3
If 80 [mm] is reduced to 35 × 2 = 670 [mm], that is, approximately 10.7 [%], the required magnetomotive force is approximately (5/9) × 100 = 56 [%], and accordingly The coil assembly can be made smaller. Therefore, the magnetic field generator can be reduced in size and weight.

Of course, a plurality of coils may be housed in the annular convex portion, including coils other than the side coils. Further, a plurality of annular convex portions may be provided in a concentric shape, and a side coil or another coil may be accommodated in each. Further, the cryogenic container may have an annular shape.

Further, the annular coil is not limited to the annular one, but may be an annular one such as a rectangular one or a field track one, that is, a loop one. Further, the shape of the cryogenic container may be changed according to the shape of these coils within a range that does not impair the object of the present invention.

Further, the order of arrangement of the gradient magnetic field generator, the transmitting coil and the receiving coil is not limited to the above-mentioned respective embodiments. Then, the function of both the transmitting coil and the receiving coil may be used, for example, one function may be selectively used by one coil by time shearing. The shape of the transmitting coil and the receiving coil is not limited to the rectangular plate shape, and the same effect can be obtained even if it has another shape.

Although the central axis Z of the coil assembly has been described in the vertical direction, it may be applied to a magnetic field generator in which the central axis Z is horizontal or inclined.

In the above embodiments, the magnetic field generator in which the coil assembly is the superconducting coil has been described, but the coil assembly uses the normal conducting coil and is not applicable to the magnetic field generator without the cryogenic container. Needless to say. Of course, the same effect can be obtained by applying it to both the non-shield type and the active shield type.

[0035]

Since the present invention is constructed as described above, it has the following effects. For accommodating the coil assembly for accommodating the coil assembly, and for accommodating the flat coil- shaped gradient magnetic field generation coils in the mutually opposing portions of the coil accommodating container for low temperature, which are arranged to face each other in the axial direction of the coil assembly at a predetermined space interval. Since the concave arrangement space is formed, it is possible to accommodate the flat-plate-shaped gradient magnetic field generating coil in the concave arrangement space, and to reduce the facing distance between the coil accommodating containers by that amount, it is necessary to generate the predetermined magnetic field. It is possible to reduce the magnetomotive force. Therefore, the coil assembly becomes smaller, and the magnetic field generator can be made smaller and lighter.

Then, a flat plate-shaped predetermined coil in the coil assembly is housed inside a portion of the coil accommodating container that surrounds the concave layout space, and the predetermined flat plate-shaped coil is arranged in a concave shape. Along with the plate-shaped gradient magnetic field coil, it is arranged so as to surround the plate-shaped gradient magnetic field coil housed in the space.
Since it is formed in a flat plate shape as a whole, the gap between the predetermined coils facing each other is reduced and the required magnetomotive force is reduced, so that the coil assembly can be downsized and the magnetic field generator can be downsized and lightweight.

Further, since the flat-plate-shaped gradient magnetic field generating coil is housed in the concave arrangement space, the facing space between the coil housing containers is reduced by that much, and the required magnetomotive force is reduced, thereby reducing the size of the coil assembly. Therefore, the magnetic field generator can be reduced in size and weight.

In addition to the flat-plate-shaped gradient magnetic field generating coil, the flat-plate-shaped high-frequency transmission coil and the flat- plate are provided in the concave arrangement space.
Accommodating at least one of the Jo high frequency reception coil
Together with a flat plate gradient magnetic field coil
Since the further by the required magnetomotive force can be reduced opposing distance between the coil container is reduced, the coil assembly becomes small, the magnetic field generator can size and weight.

Since the plate-shaped gradient magnetic field generating coil is housed in the concave arrangement space and the high frequency transmitting coil and the high frequency receiving coil are arranged outside the concave arranging space,
The magnetic field generator is small and lightweight, and the high-frequency transmitting coil and the high-frequency receiving coil can be easily visually recognized, and since the magnetic field generating device is located outside the concave arrangement space, the position and posture adjustment work becomes easy.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a magnetic field generator according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a magnetic field generator according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of a magnetic field generator according to another embodiment of the present invention.

FIG. 4 is a sectional view showing a main part of a magnetic field generating apparatus according to another embodiment of the present invention.

FIG. 5 is an external view of a conventional magnetic field generator.

FIG. 6 is a cross-sectional view showing a main part of another conventional magnetic field generator.

7 is a graph showing the relationship between the coil spacing and the magnetomotive force in the magnetic field generator of FIG.

[Explanation of symbols]

10, 20, 30, 40 Magnetic pole device, 11, 31, 41
Cryogenic container, 11a, 31a, 41a Ring-shaped convex portion, 1
1c, 31c, 41c accommodation part, 11d, 31d, 41
d recess, 12, 32, 42 coil assembly, 12a,
32a, 42a side coil, 14, 34, 44 gradient magnetic field device, 15, 35, 45 transmitter coil, 16, 3
6,46 Receive coil.

Front page continuation (72) Inventor Hirotaka Takeshima 2-12 Shinjuyo, Kashiwa-shi, Chiba Hitachi Medical Co., Ltd. (56) Reference JP-A-1-165106 (JP, A) JP-A-61-172040 (JP) , A) JP 63-65848 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) A61B 5/055

Claims (5)

(57) [Claims] 1. A magnetic pole device having a coil assembly having a plurality of annular coils and a low-temperature coil housing container for housing the coil assembly, facing each other in a predetermined space in the axial direction of the coil assembly. Divided MRI with intervals
A magnetic field generator for use in split magnetic field generator for split MRI, characterized in that a recessed arrangement space for accommodating a coil for generating a gradient magnetic field in a flat plate shape is formed at a portion facing each other of the coil accommodating containers. 2. A plate-shaped predetermined coil in the coil assembly within the portion sow takes a concave space for the coil container is housed, the flat plate shape having a predetermined coil is accommodated in a concave arrangement space It is arranged so as to surround the flat-plate gradient magnetic field coil, and together with the flat-plate gradient magnetic field coil
The split type MRI magnetic field generator according to claim 1, wherein the split type MRI magnetic field generator is a flat plate . 3. The split-type magnetic field generator for MRI according to claim 1, wherein a flat-shaped gradient magnetic field generating coil is housed in the concave arrangement space. 4. A flat- plate high-frequency transmission coil and a flat plate in addition to the flat-plate gradient magnetic field generating coil in the concave arrangement space.
Accommodating at least one of the Jo high frequency reception coil
Together with a flat plate gradient magnetic field coil
The magnetic field generator for split MRI according to claim 3, wherein 5. The split mold according to claim 3, wherein a flat-plate-shaped gradient magnetic field generating coil is housed in the concave arrangement space, and the high-frequency transmitting coil and the high-frequency receiving coil are arranged outside the concave arrangement space. Magnetic field generator for MRI.