JP6887768B2 - Magnetic shield and its installation method - Google Patents

Description

Embodiments of the present invention relate to magnetic shields and methods of installing them.

When a device that generates a magnetic field, such as a magnetic resonance imaging device, is used, a magnetic shield may be provided so that the magnetic field does not leak to the outside or an unnecessary magnetic field from the outside does not enter. Magnetic shields are typically configured to cover a room equipped with a device that generates a magnetic field.

Japanese Unexamined Patent Publication No. 2015-15487 Japanese Unexamined Patent Publication No. 2004-167104 Japanese Unexamined Patent Publication No. 62-203399

An object to be solved by the present invention is to provide a magnetic shield that changes the leakage range of the leakage magnetic field and a method for installing the magnetic shield.

The magnetic shield of the embodiment is provided so as to cover a part or all of the examination room containing the magnetic resonance imaging device. The magnetic shield comprises at least one shield material, which absorbs the leakage magnetic field generated from the static magnetic field magnet of the magnetic resonance imaging apparatus. The shield material is installed so as to have a magnetic gap, and the position of the magnetic gap in the examination room is determined based on the distribution of the leakage magnetic field leaking from the static magnetic field magnet.

The figure which looked at the magnetic resonance imaging apparatus installed in the examination room which concerns on embodiment from the ceiling side. The figure which shows the magnetic resonance imaging apparatus and the magnetic shield seen from the side which concerns on embodiment. The figure which shows the structural pattern of the magnetic shield which concerns on embodiment. The figure which shows the difference of the leakage range of the leakage magnetic field depending on the presence or absence of a magnetic gap which concerns on embodiment. The perspective view of the laboratory which concerns on embodiment. FIG. 3 is a perspective view of an examination room having a magnetic shield provided with a magnetic gap on the side surface according to the modified example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is a view of the magnetic resonance imaging apparatus 20 installed in the examination room 300 as viewed from the ceiling side. In order to clarify the correspondence of the orientations with other drawings, the longitudinal direction of the sleeper 202 is the Z direction, the lateral direction of the sleeper 202 orthogonal to the Z direction in the horizontal plane is the X direction, and the direction orthogonal to the XZ plane is Y. Determine the direction. The examination room 300 refers to the space in which the magnetic resonance imaging device 20 is installed.

The magnetic resonance imaging device 20 images a subject placed on the bed 202. The subject is moved into the bore of the gantry 200 by a top plate (not shown) on the berth 202. The static magnetic field magnet 201 housed in the gantry 200 forms, for example, a static magnetic field of about several tesla. The static magnetic field magnet 201 is composed of, for example, a superconducting coil or the like. In the bore of the gantry 200 in which the static magnetic field is formed, in the imaging space where the subject is imaged, for example, by applying a gradient magnetic field and a high-frequency magnetic field to the subject, magnetic resonance data of the subject is acquired. can do. The gradient magnetic field is formed by a gradient magnetic field coil (not shown). The high frequency magnetic field is formed by a high frequency coil (not shown). The acquired magnetic resonance data is sent to, for example, a unit in a machine room provided outside the examination room 300. The machine room unit produces a magnetic resonance image based on the magnetic resonance data. The unit placed in the machine room is not limited to a unit that generates a magnetic resonance image, but also includes, for example, a unit that supplies power and a unit that cools.

The static magnetic field formed by the static magnetic field magnet 201 is preferably formed only in the imaging space inside the bore, but in reality, the static magnetic field is also formed outside the imaging space. Here, the static magnetic field formed outside the imaging space is referred to as a leakage magnetic field. Since the leaked magnetic field may cause harm to electronic devices, for example, it is required to prevent the leaked magnetic field having a predetermined strength or higher from leaking to the outside of the examination room. The leakage magnetic field is controlled by the magnetic shield 1 so as not to leak to the outside of the examination room 300 with a predetermined strength or more.

The magnetic shield 1 is made of a magnetic shield material and is provided so as to cover a part or all of the inspection room 300. By the way, "covering" a part or all of the examination room 300 is intended to cover the space in which the magnetic resonance imaging device 20 is installed. That is, there is no intention of limiting whether the shield material is provided inside or outside the interior forming the inspection room 300. The shield material absorbs the magnetic flux corresponding to the leakage magnetic field generated from the static magnetic field magnet 201 inside the shield material. As the shielding material, for example, electromagnetic soft iron, directional silicon steel, non-directional silicon steel, permalloy, amorphous and the like are used. The magnetic shield 1 can prevent the leaked magnetic field from leaking to the outside of the inspection room 300. At the same time, it is possible to prevent an external magnetic field from the outside of the examination room 300 from being mixed into the magnetic field formed by the magnetic resonance imaging device 20 as noise. The magnetic shield 1 is provided on, for example, a floor surface, a ceiling surface, and a side surface (wall surface). In addition, in FIG. 1, the magnetic shield 1 may be provided also in the lower part of the magnetic resonance imaging apparatus 20.

The magnetic shield 1 may be divided into a plurality of shield materials. For example, a plurality of shield materials may be spread on the floor surface of the inspection room 300 to form the magnetic shield 1. Further, the magnetic shield 1 may be configured by providing a shield material not only on one surface of the floor but also on a plurality of surfaces such as a wall surface and a ceiling surface. Since the surface that requires the shield material varies depending on, for example, the size of the inspection room 300, it is arbitrary on which surface of the inspection room 300 the shield material is installed. Hereinafter, the magnetic shield 1 is a general term for one or a plurality of shield materials.

The shield material constituting the magnetic shield 1 has a magnetic gap 2 at a position away from the static magnetic field magnet 201 so that the leakage range of the leaked magnetic field leaking in the vicinity of the static magnetic field magnet 201 becomes smaller with respect to the external direction of the inspection room 300. Is provided to have. For example, the magnetic gap 2 is provided in the vicinity of the end portion of the bed 202 in the longitudinal direction on the side away from the static magnetic field magnet 201. The magnetic gap 2 is a space intentionally provided in the inspection room 300 in which a shield material is not intentionally provided. The magnetic gap 2 is not, for example, an accidental gap between the shield materials that may occur when a plurality of shield materials are spread. FIG. 1 illustrates the magnetic gap 2. The magnetic gap 2 is a region surrounded by a broken line in FIG. The magnetic gap 2 is provided, for example, in the sleeper 202 near the end on the side away from the static magnetic field magnet 201. The magnetic gap 2 is not limited to a space having nothing materially, and may be a space provided with a non-magnetic material or a material having a magnetic permeability lower than that of the shielding material. The magnetic gap 2 may be filled with, for example, concrete or resin, or may be covered with a non-magnetic plate.

Generally, when the site area of the examination room is limited, the range affected by the strong leakage magnetic field in the examination room is wide, so that a magnetic shield is provided over the entire floor surface. On the other hand, the magnetic shield 1 according to the embodiment does not provide a shield material over the entire floor surface, but intentionally provides a magnetic gap 2 in a part of the floor surface and intentionally leaks into the magnetic gap 2. Leak the magnetic field. By leaking the leaked magnetic field into the magnetic gap 2 provided at a position away from the static magnetic field magnet 201, the leakage range of the leaked magnetic field leaking in the vicinity of the static magnetic field magnet becomes smaller with respect to the external direction of the inspection room 300.

If the magnetic gap 2 is provided close to the static magnetic field magnet 201, a strong leakage magnetic field leaks under the gantry 200. Therefore, the magnetic gap 2 is provided at a position farther than the static magnetic field magnet 201. For example, in the case of the inspection room 300 having a long side of 6 m and a short side of 4 m, a magnetic gap 2 having an area of about one-fifth of the floor surface is provided. That is, a magnetic gap 2 having a size of 4 m in the short side direction of the examination room 300 and 1.2 m in the long side direction of the examination room 300 is provided.

FIG. 2 is a view of the side surfaces of the magnetic resonance imaging device 20 and the magnetic shield 1 as viewed from the Y direction. Although FIG. 2 is drawn so that the magnetic resonance imaging device 20 and the magnetic shield 1 are in direct contact with each other, a floor material or the like may be provided between them. The magnetic gap 2 of the magnetic shield 1 is not limited to the configuration shown in FIG. 2, and may have a configuration as shown in FIG.

FIG. 3 shows another example regarding the configuration of the magnetic shield 1. FIG. 3A is an example in which a thin shield material 1b is further provided on the bottom surface of the magnetic gap 2 in addition to the shield material 1a. Further, FIG. 3B is an example in which a thin shield material 1c is further provided in addition to the shield material 1a at a portion located on the upper surface of the magnetic gap 2. Further, FIG. 3C is an example in which the shield material 1a and the shield material 1d having the same thickness as the shield material 1a are provided so as to sandwich the magnetic gap 2. By combining the examples shown in FIGS. 3 (A), 3 (B), and 3 (C), the magnetic gap 2 is surrounded by the shield materials 1a, 1b, 1c, and 1d. A magnetic cavity may be formed. The magnetic shield 1 illustrated in FIG. 3 has a space having a low magnetic permeability to the extent that it can be magnetically regarded as a gap or a cavity with respect to the entire magnetic shield 1.

FIG. 4 is a diagram for comparing the leakage range of the leakage magnetic field between the case where the magnetic gap 2 is not provided and the case where the magnetic gap 2 is provided. The magnetic shield 1 is arranged so as to surround the examination room 300. The dotted line shows the distribution of the leakage magnetic field having a predetermined intensity. In FIGS. 4 (A) and 4 (B), the dotted line shows the distribution of the leakage magnetic field having the same intensity. The predetermined strength is, for example, the maximum permissible value of the leakage magnetic field defined by the standard. A slab 3 forming an underfloor is provided under the magnetic shield 1. The slab 3 is formed of, for example, concrete. The leaked magnetic field does not have to be completely absorbed by the magnetic shield 1. For example, a part of the leaked magnetic field may leak to the slab 3 as long as the leaked magnetic field having a predetermined strength does not leak to the room downstairs of the inspection room 300.

FIG. 4A is an example in which the magnetic shield 1 is not provided with the magnetic gap 2. When the magnetic gap 2 is not provided, the leakage magnetic field leaks under the static magnetic field magnet 201 to a maximum depth of T1 in the Y direction. The reference surface for the depth is the floor surface of the examination room 300. FIG. 4B is an example in which the magnetic shield 1 is provided with the magnetic gap 2. When the magnetic gap 2 is provided, the leakage magnetic field leaks to a maximum depth of T2 under the static magnetic field magnet 201. At the same time, a leaking magnetic field leaks to a maximum depth of T3 at the position of the magnetic gap 2. T2 and T3 are smaller than T1 with respect to the maximum depth at which the leaked magnetic field leaks. Comparing FIGS. 4 (A) and 4 (B), the magnetic gap 2 is provided in the magnetic shield 1, so that the distribution of the leakage magnetic field concentrated under the static magnetic field magnet 201 is dispersed. Will be done. Since the magnetic flux related to the leaked magnetic field is preserved, the leakage range of the leaked magnetic field having a predetermined strength leaking under the static magnetic field magnet 201 is reduced by the amount leaked from the magnetic gap 2. For example, in an examination room 300 having a long side of 6 m and a short side of 4 m, a magnetic gap 2 having a size of 4 m in the short side direction of the examination room 300 and 1.2 m in the long side direction of the examination room 300 is provided. If provided, the distribution of the leaked magnetic field leaking from the static magnetic field magnet 201 becomes smaller by about 10 cm in the Y direction. As described above, the leaked magnetic field may be partially leaked to the slab 3. In the example shown in FIG. 4B, the leakage magnetic field does not reach the slab 3. That is, it is considered that the leakage magnetic field can be kept in the slab 3 even if the thickness of the magnetic shield 1 under the floor is reduced. It should be noted that the size of the magnetic gap 2 having a short side of 1 meter or more as described above is merely an example, and indicates that it is larger than the gap between a plurality of shield materials that may unintentionally occur.

Which part of the magnetic shield 1 the magnetic gap 2 is provided in is determined based on the environment in which the examination room 300 is placed. The environment in which the inspection room 300 is placed is related to a building structure, for example, an arrangement related to a magnetic building member. Magnetic building members are, for example, walls, columns, beams, etc., including reinforced concrete and steel frames. Further, the environment in which the examination room 300 is placed is, for example, the influence of a shield opening provided separately from the magnetic gap 2. The shield opening is, for example, a filter panel 21, a window 22, and a door 23. The position of the magnetic gap 2 in the examination room is determined based on the distribution of the leaked magnetic field obtained from the static magnetic field magnet 201 by, for example, simulation.

FIG. 5 is a diagram for explaining the filter panel 21, the window 22, and the door 23.

The filter panel 21 is a distribution frame in which a cable for connecting the magnetic resonance imaging device 20 in the inspection room 300 and the unit in the machine room is wired.

The window 22 is, for example, a window provided so that the operator can observe the inside of the examination room 300 from the operation room provided with the console for operating the magnetic resonance imaging device 20. The windows may be magnetically shielded to prevent the leakage magnetic field from leaking. The window 22 does not necessarily have to be provided in the inspection room 300.

The door 23 is a door provided so that the subject and the operator can enter and exit between the inside and the outside of the examination room 300.

For example, the shield opening is formed by hollowing out a surface of the inspection chamber 300, whereas the magnetic gap 2 is a slit provided on one surface of the inspection chamber 300 without a magnetic shield. It can also be expressed.

Although the magnetic shield 1 described above shows an example in which the magnetic gap 2 is provided on the floor surface of the inspection room 300, it may be provided on the ceiling surface. When it is provided on the ceiling surface, the position where the magnetic gap 2 is installed is determined based on the environment in which the examination room 300 is placed, as in the case of the floor surface.

(Modification example)
The magnetic shield 1 according to the above-described embodiment is provided with the magnetic gap 2 on the floor surface or the ceiling surface, but the present invention is not limited thereto. The magnetic shield 1 according to this modification is provided with a magnetic gap 2 on the side surface.

FIG. 6 is a diagram showing a magnetic shield 1 provided with a magnetic gap 2 on the side surface. The magnetic shield 1 is provided with magnetic gaps 2a and 2b separately from the filter panel 21, the window 22, and the door 23. The magnetic gap 2 is provided in a slit shape at a corner of the examination room 300.

The magnetic gaps 2a and 2b are provided on the side surface of the examination room 300 and on the side where the sleeper 202 is installed with respect to the gantry 200. In FIG. 6, among the side surfaces of the inspection room 300, magnetic gaps 2a and 2b are provided on the surface where the door 23 is located and the surface facing the surface. For example, the filter panel 21 is provided. A magnetic gap 2 may be provided on the surface facing the surface. In any case, the magnetic gap 2 is provided at a position away from the static magnetic field magnet 201.

According to the embodiment described above, the magnetic gap 2 is provided at a position away from the static magnetic field magnet 201 of the magnetic shield 1 provided in the examination room 300. As a result, the leakage range of the leakage magnetic field leaking to the outside of the examination room 300 can be reduced as compared with the case where the magnetic shield is comprehensively provided for the examination room 300. In particular, the strength of the leaked magnetic field can be reduced in a region where the strength of the leaked magnetic field is large in the vicinity of the static magnetic field magnet 201. At the same time, since the shield material in the portion corresponding to the magnetic gap 2 is not required, the material cost of the magnetic shield can be reduced.

Further, if the leakage range of the leakage magnetic field leaking to the outside of the inspection room 300 can be reduced, the thickness of the shield material constituting the magnetic shield 1 can be reduced. Therefore, the material cost related to the shield material can be further reduced.

Conventionally, when installing a magnetic resonance imaging device 20 that generates a high static magnetic field in a narrow examination room, for example, increasing the thickness of the shield material has been a countermeasure. However, when the magnetic resonance imaging device 20 is used, there is a problem that when the thickness of the magnetic shield is increased, the force of attraction between the superconducting coil included in the static magnetic field magnet 201 and the magnetic shield 1 becomes large. When the attractive force increases, the superconducting coil in the static magnetic field magnet is displaced, and enormous thermal energy is generated. Then, a large amount of liquid helium, for example, for cooling the superconducting coil is vaporized and quenched. On the other hand, since the magnetic shield 1 according to the embodiment can be made thinner than the conventional configuration, the risk of quenching can be reduced. In particular, the risk of quenching can be reduced by making it possible to reduce the thickness of the shield material on the floor surface close to the static magnetic field magnet 201.

According to the magnetic shield 1 according to the embodiment, for example, when the space prepared for installing the magnetic resonance imaging device 20 is limited, the thickness of the magnetic shield can be reduced, so that the examination room can actually be used. The space that can be used as 300 can be expanded more than before.

According to the magnetic shield 1 according to the above-described modification, the leakage range of the leakage magnetic field leaking to the outside of the inspection room 300 can be reduced by providing the magnetic gap 2 on the side surface of the inspection room 300. Further, by providing the magnetic gap 2 on the side surface of the examination room 300 in addition to the floor surface, the leakage magnetic field leaking to the outside of the examination room 300 as compared with the case where the magnetic gap 2 is provided only on the floor surface. Can be more dispersed. Further, since the number of places where the shield material is conventionally arranged is replaced with the magnetic gap 2, the material cost can be further reduced.

Although embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 Magnetic shield 2 Magnetic gap 20 Magnetic resonance imaging device 200 Stand 201 Static magnetic field magnet 202 Sleeper 21 Filter panel 22 Window 23 Door 300 Inspection room

Claims (9)

A magnetic shield provided to cover the examination room that houses the magnetic resonance imaging device.
It is provided with at least one shield material that absorbs the leakage magnetic field generated from the static magnetic field magnet of the magnetic resonance imaging apparatus.
The shield material is provided so as to have a magnetic gap, and the position of the magnetic gap in the examination room is determined based on the distribution of the leakage magnetic field leaking from the static magnetic field magnet.
Magnetic shield. A magnetic shield provided to cover the examination room that houses the magnetic resonance imaging device.
It is provided with at least one shield material that absorbs the leakage magnetic field generated from the static magnetic field magnet of the magnetic resonance imaging apparatus.
The shield material is provided so as to have a magnetic gap, and the position of the magnetic gap in the examination room is the side of the longitudinal end of the bed of the magnetic resonance imaging device away from the static magnetic field magnet. Near the edge of
Magnetic shield. The magnetic gap is at least one of a space in which nothing is physically arranged, a space in which a non-magnetic material is arranged, and a space in which a member having a magnetic permeability lower than that of the shield material is arranged. ,
The magnetic shield according to claim 1 or 2. The shield material is provided on at least one of the floor surface, the ceiling surface, and the side surface of the inspection room.
The magnetic shield according to any one of claims 1 or 3. The magnetic gap is provided for wiring between a window provided so that the inside of the examination room can be seen from the outside of the examination room, and the outside of the examination room and the inside of the examination room. It is provided separately from the filter panel provided and the shield opening including at least one of the doors provided to enter and exit the outside and inside of the laboratory.
The magnetic shield according to any one of claims 1 to 4. The position or size of the magnetic gap was determined based on the building structure of the laboratory.
The magnetic shield according to any one of claims 1 to 5. The building structure is provided to wire between a window provided so that the inside of the inspection room can be seen from the outside of the inspection room, and between the outside of the inspection room and the inside of the inspection room. At least the influence of the shield opening including at least one of the filter panel and the door provided to enter and exit the outside and the inside of the inspection room, or the arrangement of magnetic building members. Including one,
The magnetic shield according to claim 6. It is a method of installing a magnetic shield so as to cover the examination room that houses the magnetic resonance imaging device.
A magnetic gap is located in the laboratory in which at least one shield material that absorbs the leakage magnetic field generated from the static magnetic field magnet of the magnetic resonance imaging device is defined based on the distribution of the leakage magnetic field leaking from the static magnetic field magnet. To install,
How to install the magnetic shield. It is a method of installing a magnetic shield so as to cover the examination room that houses the magnetic resonance imaging device.
At least one shield material that absorbs the leakage magnetic field generated from the static magnetic field magnet of the magnetic resonance imaging device is attached to the end portion of the longitudinal end of the bed of the magnetic resonance imaging device on the side away from the static magnetic field magnet. A magnetic gap is provided in the vicinity of the above so as to be located in the inspection room.
How to install the magnetic shield.

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