JPH0672937B2 - Magnetic shield room door - Google Patents

Description

TECHNICAL FIELD The present invention relates to a door of a room in which a strong magnetic field generator such as a magnetic resonance diagnostic apparatus is installed, and in particular, a magnetic field from which a magnetic field does not leak. Is.

“Prior art” Recently, in a hospital, a magnetic resonance diagnostic device (hereinafter referred to as MRI) is installed, but in a hospital, there are patients who are equipped with pacemakers, and magnetic influences such as computers are adversely affected. There are many devices to receive. Therefore, as shown in Fig. 4, in order to prevent the leakage magnetic field from MRI from leaking to the outside, a magnetic shield A made of a ferromagnetic material such as pure iron is provided on the 4th or 6th side of the room, and the influence of external radio waves is reduced. A radio wave shield B is provided on the six sides of the room for the purpose of shutting off.

Even in a room where the magnetic shield A and the radio wave shield B are provided, if there is a gap at the entrance and exit of the room, both shield effects will be significantly reduced. For this reason, the gaps in the room where the MRI, etc. are installed are all welded, all soldered, etc. to eliminate the gap for magnetic leakage. In addition, the openings such as the entrance and exit of the room are also provided with a radio wave shield by a stainless plate, shield glass, finger contacts, and the like.

However, since a heavy magnetic material is used for the magnetic shield, it is difficult to magnetically shield the door portion of the entrance / exit. The entrance / exit of the MRI room has a size of, for example, 1400 mm in width and a height because a stocker carrying a patient and treatment equipment go in and out.
It will be about 2100 mm, and a large door will be required. When such a large door is made of a magnetic material, it is pulled by a magnet and opening and closing becomes extremely difficult. Therefore, it is unavoidable that the door is not magnetically shielded.

[Problems to be Solved by the Invention] When the door is not magnetically shielded as in the conventional MRI room, a large magnetic field leaks at the door.

That is, as shown in Fig. 4, when a 1.5T (Tesla) MRI is installed, a 5G (Gauss) line, which is a controlled area for pacemaker wearers and a standard for computer installation, greatly expands from the door, There was a big management problem.

In addition, if the door is separated from the MRI as much as possible and the distance attenuation is used to suppress the leakage magnetic field, the position of the door is restricted, which causes a problem in construction planning. Moreover, the magnetic field distribution in the MRI room is greatly distorted, and it was difficult to adjust the shim coil to prevent distortion in the MRI image.

In addition, in order to suppress magnetic field generation from MRI, M when opening and closing the door
It is possible to cut off the power supplied to the RI, but the superconducting type MRI that generates a strong magnetic field uses a superconducting electromagnet to send a permanent current to it, so it operates fully for 24 hours.
The leakage magnetic field from I could not be suppressed.

Therefore, it is an object of the present invention to provide a magnetic shield on the door of an MRI room and to easily open and close the door.

"Means for Solving the Problem" The magnetic shield room door of the present invention is provided with a ferromagnetic material having substantially the same plane shape as that of the door and a heater for heating the ferromagnetic material to a Curie temperature or higher, and A heat dissipation device for cooling the magnetic body is provided.

In order to effectively heat the door and block heat to the outside of the door, heat insulating materials may be provided on both sides of the ferromagnetic material. Further, the heat dissipation device can be composed of, for example, a heat pipe and a fan.

[Operation] In the magnetically shielded room door of the above means, when the door is closed, the heat dissipation device is operated to lower the temperature of the ferromagnetic material to the Curie temperature or lower, so that the ferromagnetic material has ferromagnetism. Thus, if the ferromagnetic material has a ferromagnetism if it is below the Curie temperature, the magnetic shield of the door portion is maintained.

When opening the door, the heater is operated to heat the ferromagnetic material to the Curie temperature or higher. Since the ferromagnetic material becomes non-magnetic above the Curie temperature, the door is not pulled by the leakage magnetic field from the strong magnetic field generator in the magnetic shield room, and the door can be easily opened and closed.

As shown in FIG. 3, the ferromagnet becomes non-magnetic above the Curie temperature, and suddenly loses the ferromagnetism above the Curie temperature. Is changed to and. For example, the Curie temperature of iron is 49
6 ° C, and the Curie temperature of nickel is about 85 ° C.

"Embodiment" An embodiment of the present invention will be described with reference to FIGS.

Since a device for generating a strong magnetic field such as a magnetic resonance diagnostic device (MRI) is installed in a room provided with the magnetic shield wall A and the current shield wall B, the door 2 of the room 1 is magnetically shielded by the following configuration. Let It should be noted that a stainless frame 3 having a heat insulating material inside is provided at the periphery of the opening of the chamber 1 in which the door 2 is provided, and a corner portion formed by the stainless frame 3 and the periphery of the opening of the chamber is made of, for example, an amorphous high-permeability material. 4 is provided, and finger contacts 5 for radio wave shielding are provided on the inner peripheral surface of the stainless steel frame 3.

The door 2 is formed in a hollow shape by a non-magnetic stainless steel plate 2a, and a ferromagnetic material 6 having substantially the same plane as the door 2 is arranged in the center of the hollow portion in the thickness direction. In this example, the ferromagnetic material 6 was made of iron with a Curie temperature of 496 ° C. A heater 7 in which, for example, a nichrome wire is spirally wound on both sides of the ferromagnetic body 6.
Is provided so that the ferromagnetic material 6 can be heated to the Curie temperature or higher. The heater 7 is arranged in a zigzag shape as shown in FIG. 2 so that the entire surface of the ferromagnetic material 6 can be heated.
Both ends thereof were connected to a power source 9 via a switch 8. A heat insulating material 10 such as ceramic fiber is filled between the ferromagnetic body 6 and the stainless steel plate 2a, and the heat insulating material 10 is provided with a concave groove 11 for disposing the heater 7. The heater 7 effectively heats the ferromagnetic material 6, and heat is prevented from being transmitted to the stainless plate 2a on the outer surface of the door as much as possible.

Several heat pipes from the right place of the ferromagnetic material 6 to the outside of the door
12 is provided, and the fan 13 is opposed to the wide portion of the outer end of the heat pipe 12 so that heat can be released. The inner end side of the heat pipe 12 is arranged in a recess 14 provided in the ferromagnetic body 6, and the heat pipe 12 passes through the through hole of the heat insulating material 10. The fan 13 is arranged in a recess provided in the heat insulating material 10, and the fan 13 faces an opening 15 provided in the stainless plate 2a on the outer surface of the door 2. And several fans 13 are the second
Connected to power supply 17 via switch 16 as shown
When the fan 13 is rotated, the ferromagnetic body 6 is cooled via the heat pipe 12.

The magnetic shield room door is configured as described above, and the switch 8 of the heater 7 and the switch 16 of the fan 13 are alternately turned ON and OF
The ferromagnetic material 6 can be changed to a temperature above or below the Curie temperature by performing F so that the door portion can appropriately have a magnetic shield function.

The present invention is not limited to the above-mentioned heating device (heater) and heat dissipation device (heat pipe and fan), and they can be changed to other known devices.

[Advantages of the Invention] According to the door for a magnetically shielded room of the present invention, the ferromagnetic material in the door is changed to a temperature above or below the Curie temperature as appropriate by a heater and a heat dissipation device to make it nonmagnetic and ferromagnetic. Can be changed. Therefore, when the door is opened and closed so that people and things can enter and leave it, the door can be opened and closed easily by making the door non-magnetic so that it cannot be attracted by magnetic force.

Furthermore, since the door of the room can be magnetically shielded, the degree of freedom in setting the position of the door is increased and it is not necessary to consider the distance attenuation of the magnetic field generated by MRI etc. so the area of the MRI room can be kept small and Since the distortion of the magnetic field of is small, adjustment by the shim coil is easy.

[Brief description of drawings]

1 is a side sectional view of a magnetic shield room door of the present invention, and FIG. 2 is a front view of the door showing the arrangement of a heater and a fan,
FIG. 3 is a graph showing a change in magnetism with respect to temperature of a ferromagnetic material, and FIG. 4 is an explanatory diagram showing a magnetic field state in a conventional MRI room. 2; Door, 6; Ferromagnetic material 7; Heater, 10; Thermal insulation material 13; Fan

Claims (3)

[Claims] 1. A door of a magnetically shielded room in which a strong magnetic field generator is installed is provided with a ferromagnetic material having substantially the same plane as that of the door, and a heater for heating the ferromagnetic material to a Curie temperature or higher is provided. A door for a magnetically shielded room, which is provided with a heat dissipation device for cooling the magnetic body. 2. The door for a magnetically shielded room according to claim 1, wherein a heat insulating material is provided on both sides of the ferromagnetic material. 3. A door for a magnetically shielded room according to claim 1, wherein a heat pipe is arranged in the ferromagnetic material and a fan is provided at an outer end portion of the heat pipe to constitute a heat dissipation device.