JP2005144132A - Superconductive magnet device and magnetic resonance imaging device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI device with small magnetic field fluctuation in spite of room temperature fluctuation and vibration. <P>SOLUTION: The superconductive magnet device for the MRI device is characterized in that a magnetic material for correcting the magnetic field is arranged in a heat shield system of the superconductive magnet device. Further, the device is also characterized in that the magnetic material for correcting the magnetic field is arranged in a location where the room temperature fluctuation is not conducted present in a vacuum container. The MRI device having the small magnetic fluctuation in spite of the room temperature fluctuation and the vibration can be provided while ensuring magnetic field correction effect according to the superconductive magnet device for the MRI device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a superconducting magnet apparatus and a magnetic resonance imaging (hereinafter referred to as MRI) apparatus using the same, and more particularly to a superconducting magnet apparatus suitable for open-type MRI analysis that does not give a sense of blockage to a subject. It relates to the used MRI apparatus.

  In the conventional MRI apparatus, the magnetic material is generally disposed in the room temperature portion of the superconducting magnet apparatus of the MRI apparatus as a place where the magnetic material is disposed.

  In addition, as an example of another conventional superconducting magnet device of an MRI apparatus, Japanese Patent Laid-Open No. 2001-224571 (hereinafter referred to as Reference 1) discloses a ferromagnetic material in a coil container filled with cryogenic helium. An MRI apparatus in which is installed is disclosed.

JP 2001-224571 A Japanese Patent Laid-Open No. 10-99717

However, when a magnetic material is disposed in the room temperature portion shown in the conventional example, the following problems occur.
(1) The magnetic material disposed in the normal temperature part is subjected to a change in room temperature, and the dimension is displaced, and the magnetic field uniformity is changed.
(2) Relative displacement between the low temperature part of the superconducting magnet device and the vacuum vessel is inevitable with respect to vibrations when GC is applied and external vibrations. In this case, if the magnetic material for magnetic field correction is in the normal temperature system, a relative displacement occurs between the magnetomotive force position in the low temperature part and the magnetic material for magnetic field correction in the normal temperature part, and the magnetic field uniformity changes.

The above problem may be solved by arranging a magnetic material in a container filled with a cryogenic helium liquid. In this case, the following problem occurs.
(1) Since the container filled with helium liquid is installed in the heat shield plate in the cryostat, the gap between the heat shield plate and the container filled with helium liquid, and the thickness of the container plate filled with helium liquid are Inevitably, it will move away from the magnet center. Therefore, the sensitivity of the influence of the magnetic field on the center of the magnet is reduced accordingly, and the volume of the magnetic material for magnetic field correction is increased, increasing the magnet weight and making correction difficult in some cases.

  The present invention is intended to solve the above-mentioned problems, and its purpose is to reduce the change in the generated magnetic field against changes in room temperature and vibration, and to suppress an increase in weight even when a magnetic material for magnetic field correction is used. It is an object of the present invention to provide a superconducting electromagnet apparatus and an MRI apparatus.

  In order to achieve the above object, the superconducting electromagnet device of the present invention is characterized in that a magnetic material for magnetic field correction is installed on a heat shield plate.

  In order to achieve the above object, the superconducting electromagnet apparatus of the present invention is characterized in that a magnetic material for magnetic field correction is installed outside the coil container and inside the vacuum container.

  Furthermore, in order to achieve the above object, in the superconducting electromagnet apparatus of the present invention, a magnetic material for magnetic field correction is installed outside the coil container and in a vacuum container where a change in room temperature is not transmitted. It is a feature.

  According to the superconducting magnet device of the present invention described above, even if a magnetic material for magnetic field correction is used, the magnetic field change can be reduced with respect to room temperature change and vibration. It is possible to provide a high-performance MRI apparatus using this.

  Embodiments of the present invention will be described below with reference to the drawings.

  An outline of an embodiment of the MRI apparatus of the present invention will be described. As shown in FIG. 6, the MRI apparatus includes a superconducting coil (not shown), a coil container (not shown) that houses the superconducting coil together with a helium liquid refrigerant, surrounds the coil container, and the inside is a vacuum. A superconducting magnet device 300 comprising vacuum vessels 41 and 42, an RF coil 5 and a gradient magnetic field coil 6, a bed 400 on which the subject is placed, and a control device 500 for analyzing a nuclear magnetic resonance signal from the subject. The vacuum vessels 41 and 42 are supported by support members 202 and 204 and arranged so as to be opposed to each other, and a magnetic field space is vertically formed between the vacuum vessels 41 and 42, and the bed Tomography is performed through a subject on 400.

  Next, an embodiment of the present invention employed in the MRI apparatus will be described below.

  FIG. 1 shows the configuration of the superconducting magnet device according to the first embodiment of the present invention. In the embodiment of FIG. 6, the central axis Z passing through the center of the superconducting magnet device intersects with the central axis Z. The structure seen from the cross section which passes along the axis | shaft R is shown.

  In the superconducting magnet apparatus of FIG. 1, liquid helium 8 is contained in a coil container 2, and an annular superconducting coil 1 is accommodated in the cryogenic liquid. And the coil container 2 has the heat shield 31 covering the perimeter, and the heat insulation with the exterior is achieved. Further, the heat shield 31 is covered with the vacuum vessel 4 so that the outside and the coil vessel 2 are evacuated to achieve heat insulation. The vacuum vessel 4 facing the measurement space has a recess, and the gradient magnetic field coil 6 is accommodated in the recess, and the RF coil 5 is provided on the measurement space side.

  In the configuration of this apparatus, a columnar or cylindrical magnetic material 51 for correcting a magnetic field is provided on the central axis Z, and an axially symmetric position with the central axis Z sandwiched outside the magnetic material 51. Is provided with an annular magnetic material 52. And these magnetic materials 51 and 52 are hold | maintained by the plate-shaped heat shield 31 arrange | positioned up and down. In addition, an annular magnetic material 53 is disposed outside the magnetic material 52 while being held by the heat shield 31 at an axially symmetric position with the central axis Z in between.

  In the conventional superconducting magnet device, since the magnetic material is arranged in the vacuum vessel, when the room temperature changes, the vacuum vessel is thermally contracted or expanded, and the position of the magnetic material is changed according to the displacement of the vacuum vessel. However, since it has been difficult to ensure the stability of the central magnetic field, the superconducting magnet device according to the present invention uses magnetic materials 51, 52, and 53 as shown in FIG. By installing it so that it is supported by the heat shield plate, even if the room temperature changes and the vacuum vessel 4 is thermally contracted or expanded, the position and dimensions of the magnetic material are changed without being affected by the heat shield plate. Therefore, the uniformity of the magnetic field can be kept stable.

  FIG. 2 shows a second embodiment of the present invention.

  This embodiment shows a region sandwiched between the central axis Z and the axis R in the cross section passing through the central axis Z of the superconducting magnet device and the axis R intersecting the central axis Z. Unless otherwise indicated, the same reference numerals in the embodiment of FIG. 2 as those in the embodiment of FIG. 1 have the same configuration and effects.

In this embodiment, unlike the previous embodiment, the magnetic materials 51 and 52 are not held by the heat shield 31 covering the coil container 2, and the heat shield 62 is made of the same material as the heat shield 31. , 64. The magnetic materials 51 and 52 and the heat shields 62 and 64 are supported by the heat insulating plate 7 from the heat shield 31. The heat insulating plate 7 has a structure in which the heat insulating plate 7 standing in the vertical direction is an annular magnetic material. The magnetic members 51 and 52 are supported from the heat shield 31 via the heat insulating plate 7. The same function and effect can be obtained by using an annular heat insulating material instead of the heat insulating plate 7. Further, the heat shield 62 made of the same material as the heat shield 31,
Instead of 64, a member made of a different material can be used.

  According to the present embodiment, the arrangement positions of the magnetic members 51 and 52 are integrated with the heat shield 31 via the heat insulating plate 7, so that the same effect as in the first embodiment can be expected. Further, by supporting the magnetic materials 51 and 52 via the heat insulating plate 7, the amount of heat of the magnetic materials 51 and 52 is less transferred to the heat shield 31, so that the magnetic materials 51 and 52 than the heat shield 31. It becomes possible to use the apparatus at a high temperature. Thereby, the radiation penetration | invasion heat amount from the vacuum vessel 4 to the magnetic materials 51 and 52 reduces compared with the case of FIG. 1 integrated and comprised by the shield board. When the amount of heat penetration into the heat shield 31 is reduced, the load on the refrigerator (not shown) that cools the liquid helium is reduced, and it is possible to realize a freezing allowance in the system configuration.

  FIG. 3 shows a third embodiment of the present invention.

  This embodiment shows a cross section passing through the central axis Z of the superconducting magnet device and the axis R intersecting with the central axis Z as in the embodiment of FIG. 2, and in this embodiment, particular mention is made. Unless otherwise indicated, the same reference numerals as those in the above-described embodiments have the same configuration and effect.

  In this embodiment, the magnetic material 52 is supported from the heat shield 31 via the heat insulating supports 101, 102 at a plurality of locations on the outer periphery, and the magnetic material 51 is also supported at the heat insulating supports 103, The magnetic material 52 is supported via 104. As described above, in this embodiment, the magnetic materials 51 and 52 are supported by the heat insulating supports 101, 102, 103, and 104 from the heat shield 31. Further, as the shape of the heat insulating supports 101, 102, 103, 104, the same function and effect can be obtained even if a heat insulating material having an annular shape or a rod shape is used instead of the plate shape.

  According to the present embodiment, since the magnetic members 51 and 52 are integrated with the heat shield 31 via the heat insulating supports 101, 102, 103, and 104, the same effects as those of the embodiments described above can be expected. Further, since the amount of heat of the magnetic materials 51 and 52 is less transferred to the heat shield 31 through the heat insulating support, the apparatus is used in a state where the temperature of the magnetic materials 51 and 52 is higher than that of the heat shield 31. It becomes possible. Thereby, the radiation penetration | invasion heat amount from the vacuum vessel 4 to the magnetic materials 51 and 52 reduces compared with the case of FIG. 1 integrated and comprised by the shield board. When the amount of heat intrusion into the heat shield 31 is reduced, the load on the refrigerator (not shown) is reduced as in the embodiment of FIG. 2, and it is possible to secure a freezing allowance in the system configuration.

  FIG. 4 shows a fourth embodiment of the present invention.

  This drawing shows the superconducting magnet device as seen in a cross section passing through the central axis Z and the central part of the support members 202 and 204 for the MRI apparatus shown in FIG. 7, and shows the cooling mechanism of the heat shield. It is.

In this embodiment, the cooling pipe 311 for the heat shield is connected to the coil container 2 so as to guide the evaporated helium gas to the outside, and extends downward from the support member 204 along the heat shield 31. Yes. And the magnetic material 61 stored in the lower vacuum vessel 42,
The magnetic material 51 extends along the surface of the heat shield 31 in the vicinity of the magnetic materials 61 and 62 so as to cool the magnetic material 61, and further extends upward in the support member 202, and is now housed in the upper vacuum vessel 41. , 52 extends along the surface of the heat shield 31 in the vicinity of the magnetic members 51, 52 so as to cool down, and then is connected to the outside.

  In a structure in which a magnetic material is installed on a heat shield plate as in the device of the present invention, when the heat shield plate and the magnetic material are cooled by conduction cooling from a refrigerator as in the conventional device, the initial heat capacity of the magnetic material is increased. It takes time to cool down. Thus, by adopting a structure in which the evaporative gas generated when the refrigerant is injected into the coil container cools the heat shield in the vicinity of the magnetic material, it is possible to realize mainly shortening the initial precooling time.

Also, the cooling pipe can be divided into upper and lower vacuum vessels as in the embodiment of FIG. In this embodiment, heat shield cooling pipes 311 and 312 are provided, and both the cooling pipes 311 and 312 are connected to the coil container 2 so as to guide the evaporated helium gas to the outside. The pipe 311 is disposed along the heat shield 31 on the surface facing the gradient coil 6 so as to cool the heat shield 31 housed in the upper vacuum vessel 41, and then the upper portion of the heat shield 31. It is connected with the outside after being arranged along. Further, the cooling pipe 312 extends downward in the support member 204 along the heat shield 31. After extending along the lower part of the heat shield 31 of the lower vacuum vessel 42 and further along the heat shield 31 on the surface facing the gradient magnetic field coil 6, the inside of the support member 204 is moved upward. It is configured to extend and connect to the outside.

  When the volume of the magnetic material is large, there is a temperature difference between the heat shield plate that cools first when it is cooled by one cooling pipe, for example, the lower heat shield in the embodiment of FIG. 5 and the upper heat shield that is cooled later. However, according to this embodiment, since the heat shield supporting the magnetic material in the upper and lower vacuum vessels is separately cooled, the target steady temperature distribution is reached. Time can be shortened.

  These cooling pipe configurations can also be applied to the apparatus configurations shown in FIGS. In the apparatus of FIG. 2, the magnetic material is cooled by being disposed along the heat shields 62 and 64, and in the apparatus of FIG. 3, the cooling pipe is disposed along the magnetic material to directly magnetize the magnetic material. It is possible to cool the material.

It is sectional drawing which shows one Example of the superconducting magnet apparatus of this invention. It is sectional drawing of the superconducting magnet apparatus which is another Example of this invention. It is sectional drawing of the superconducting magnet apparatus which is another Example of this invention. It is sectional drawing of the superconducting magnet apparatus which is another Example of this invention. It is sectional drawing of the superconducting magnet apparatus which is another Example of this invention. It is a perspective view of the magnetic resonance imaging apparatus using the superconducting magnet apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Superconducting coil, 2 ... Coil container, 4, 41, 42 ... Vacuum container, 5 ... RF coil, 6 ... Gradient magnetic field coil, 7 ... Thermal insulation board, 8 ... Liquid helium, 31 ... Heat shield, 51, 52 ... Magnetic material for magnetic field correction, 101, 102, 103, 104 ... heat insulating support, 300 ... superconducting magnet device, 311, 312 ... cooling pipe, 400 ... bed, 500 ... control device.

Claims (15)

An annular superconducting coil;
A coil container that houses the annular superconducting coil together with a refrigerant;
A heat shield provided to surround the coil container;
A vacuum vessel that surrounds the coil vessel and the heat shield and that is held in a vacuum inside;
In the superconducting magnet which arranges the coil containers so as to face each other and forms a magnetic field space between the two coil containers,
A superconducting magnet device, wherein a magnetic material for magnetic field correction is installed on the heat shield. The superconducting magnet device according to claim 1,
A superconducting magnet device, wherein the magnetic material for magnetic field correction is supported by a support member from the heat shield. The superconducting magnet device according to claim 1,
A superconducting magnet apparatus comprising a cooling pipe for the heat shield. The superconducting magnet device according to claim 1,
The superconducting magnet device according to claim 1, wherein the magnetic material is disposed at an axially symmetrical position with respect to a central axis of a magnetic field space formed between the two coil containers. The superconducting magnet device according to claim 4, wherein
The superconducting magnet device, wherein the magnetic material is disposed on a central axis of the magnetic field space. An annular superconducting coil;
A coil container that houses the annular superconducting coil together with a refrigerant;
A heat shield provided to surround the coil container;
A vacuum vessel that surrounds the coil vessel and the heat shield and that is held in a vacuum inside;
In the superconducting magnet which arranges the coil containers so as to face each other and forms a magnetic field space between the two coil containers,
A superconducting magnet device, wherein a magnetic material for magnetic field correction is installed outside the coil container and inside the vacuum container. The superconducting magnet according to claim 6,
A superconducting magnet device, wherein a magnetic material for magnetic field correction is installed outside the coil container and inside the heat shield. The superconducting magnet according to claim 6,
A superconducting magnet device, wherein a magnetic material for magnetic field correction is installed outside the heat shield and inside the vacuum vessel. The superconducting magnet according to claim 8,
A superconducting magnet device, wherein the magnetic material for magnetic field correction is supported by a support member from the heat shield. The superconducting magnet device according to claim 6, wherein
A superconducting magnet device, wherein a cooling pipe is installed on the magnetic material. The superconducting magnet device according to claim 6, wherein
The superconducting magnet device according to claim 1, wherein the magnetic material is disposed at an axially symmetrical position with respect to a central axis of a magnetic field space formed between the two coil containers. The superconducting magnet device according to claim 6, wherein
The superconducting magnet device, wherein the magnetic material is disposed on a central axis of the magnetic field space. In claim 1 or claim 6,
A magnetic resonance imaging apparatus using the superconducting magnet apparatus. An annular superconducting coil;
A coil container that houses the annular superconducting coil together with a refrigerant;
A heat shield provided to surround the coil container;
A vacuum vessel that surrounds the coil vessel and the heat shield and that is held in a vacuum inside;
In the superconducting magnet which arranges the coil containers so as to face each other and forms a magnetic field space between the two coil containers,
A superconducting magnet device, wherein a magnetic material for magnetic field correction is installed outside the coil container and in a place where a change in room temperature is not transmitted in the vacuum container. The superconducting magnet device according to claim 14,
A superconducting magnet device, wherein a cooling pipe is installed in a place where a change in room temperature is not transmitted in the vacuum vessel.

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