JPH02186094A - Door for magnetic shielded room - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a door for a room in which a strong magnetic field generating device such as a magnetic resonance diagnostic device is installed, and in particular to a door that prevents magnetic field from leaking from the door portion. It is.

"Conventional technology" Recently, hospitals have begun to install magnetic resonance diagnostic equipment (hereinafter referred to as MHI), but in hospitals, there are patients who are equipped with base manufacturers, and there are also cases where magnetic resonance diagnostic equipment (hereinafter referred to as MHI) is installed in hospitals, and some devices such as computers have negative effects due to magnetic resonance. There are many devices that can be used. Therefore, as shown in Figure 4, in order to prevent the leakage magnetic field from the MHI from leaking outside, a magnetic shield A made of ferromagnetic material such as pure iron is installed on the 4th or 6th side of the chamber, and the influence of external radio waves is prevented. Radio wave shields B are installed on six sides of the room for the purpose of blocking.

Even in a room provided with magnetic shield A and radio wave shield B, if there is a gap at the entrance or exit of the room, the effectiveness of both shields will be significantly reduced. Therefore, all gaps in the room where the MHI etc. are installed are welded, all soldered, etc. in order to eliminate gaps for magnetic and radio wave leakage. In addition, openings such as the entrance and exit of the room are also shielded from radio waves using stainless steel plates, shielding glass, finger contacts, etc.

However, since heavy magnetic materials are used for magnetic shielding, it is difficult to magnetically shield the entrance/exit door. The entrance to the MRI room is, for example, 1,400 meters wide, as stretchers carrying patients and treatment equipment enter and exit.
5. The height will be approximately 2100mm, and a large door will be required. If such a large door is made of magnetic material, it will be pulled by the magnet and will be extremely difficult to open and close. Therefore, the reality is that it is unavoidable that magnetic shielding is not applied to the doors.

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

In other words, as shown in Figure 4, if a 1.5 T (Tesla) MHI is installed, it will be a controlled area where pacemaker wearers are prohibited from entering, and a 5.
The G (Gauss) line was thick (spreading) from the door area, creating a major management problem.

In addition, if you try to minimize the leakage magnetic field by placing the door as far away from the MHI as possible and using distance attenuation, you will be constrained by the position of the door, which will cause problems in architectural planning.
Large distortions occurred in the magnetic field distribution in the chamber, and it was difficult to make adjustments using shim coils to prevent distortions from occurring in MHI images.

In addition, in order to suppress the generation of magnetic fields from the MHI, it is possible to cut off the power supplied to the MHI when opening and closing the door.
The superconducting type MRr, which generates a strong magnetic field, uses a superconducting electromagnet to pass a persistent current through it, so it operates at full capacity 24 hours a day, and the leakage magnetic field from the MHI could not be suppressed.

Therefore, an object of the present invention is to provide a magnetic shield to the door of an MRI room and to enable the door to be opened and closed easily.

"Means for Solving the Problems" The magnetically shielded room door of the present invention includes a solenoid coil placed on the door of a room equipped with a strong magnetic field generator, and
The outside of the solenoid coil is covered with a strong magnetic material to cancel out the leakage magnetic field toward the door.

In order to more effectively cancel the leakage magnetic field at the door, a solenoid coil can be placed on the wall of the magnetically shielded room around the outer periphery of the door to cancel the leakage magnetic field near the periphery of the door. Furthermore, the solenoid coils disposed on the door may be formed into a plurality of rectangular shapes of different sizes, and the solenoid coils may be arranged concentrically to effectively cancel out the leakage magnetic field. Furthermore, by providing a magnetic sensor on the door, the microcomputer can control the current supplied to the plurality of rectangular solenoid coils according to the detected value.

"Function" In the magnetically shielded room door of the above means, when the door is closed, if a current is supplied to the solenoid coil provided on the door, the magnetic field generated from it will suppress the magnetic field leaked from the strong magnetic field generator to the door part. Can be canceled out. Furthermore, on the outside of the rectangular solenoid coil installed on the door surface, the magnetic field emitted by the solenoid coil is in the same direction as the leakage magnetic field, but this is because the magnetic field acts outwards due to the ferromagnetic material installed outside the solenoid coil. is suppressed,
It does not strengthen the leakage magnetic field.

When opening and closing the door, a current is supplied to the door's solenoid coil and a reverse magnetic field is applied, so the door will not be pulled by the leakage magnetic field from the strong magnetic field generator and the door can be opened easily. can.

In addition, the leakage magnetic field that acts on the door changes depending on the opening angle of the door, but in addition to installing multiple solenoids on the door, solenoid coils are also installed on the room wall outside the door, and detection from a magnetic sensor The door can be opened and closed more easily by controlling the magnitude and direction of the current supplied to each solenoid coil using a microcomputer in response to signals to cancel out the leakage magnetic field that acts on the door. Note that when the door is closed, the polarity of the indoor side of the ferromagnetic material provided in the solenoid coil is different from the leakage magnetic field, so it is attracted, but when the door is opened, the current supplied to each solenoid coil is controlled. can be prevented from being absorbed.

"Example" Embodiments of the present invention will be described with reference to FIGS. 1 to 3.

Door 2 of room was magnetically shielded using the following configuration. A stainless steel frame 3 is provided around the opening of the chamber 1 in which the door 2 is provided, and although not shown, finger contacts for radio wave shielding are provided on the inner peripheral surface of the stainless steel frame 3, and a radio wave shield wall B is provided later. It is electromagnetically connected to the stainless steel plate that forms the door.

The door 2 is formed into a hollow shape by a non-magnetic stainless steel plate, and two rectangular solenoid coils 4a and 4b of different sizes are arranged concentrically in the hollow part. In this embodiment, two solenoid coils are provided, but one or three or more solenoid coils may be used, and their shape is not limited to a rectangular shape. Each solenoid coil 4a, 4b is covered with ferromagnetic material 5a, 5b on three sides outside the center of the door. This is because the magnetic field generated by the solenoid coils 4a and 4b is in the same direction as the leakage magnetic field from the strong magnetic field generator and strengthens the leakage magnetic field, so that no magnetic field is generated outside the solenoid coils. Further, the ferromagnetic materials 5a and 5b function as a yoke, and can strengthen the magnetic field on the side not covered with the ferromagnetic material.

A solenoid coil 4 is also installed around the opening of the chamber wall where the door 2 is installed.
C is arranged, and three sides of this solenoid coil 4C excluding the door facing surface are covered with a ferromagnetic material 5c. The reason why the ferromagnetic material 5c is provided is to prevent the leakage magnetic field from being strengthened on the side opposite to the door side, and to function as a yoke, as described above. The ferromagnetic material 5c is magnetically connected to the magnetic shield wall A provided on the chamber wall, so that the solenoid coil 4c can also be effectively magnetically shielded.

Each of the solenoid coils 4a, 4b, 4c is
It is constructed by winding a copper wire 10 to several hundred times, and is supplied with current from a stabilized DC power supply 7.

Further, a plurality of magnetic sensors 8 are provided over the entire surface of the door 2, so that the strength of the leakage magnetic field from the ferromagnetic material acting on each position of the door can be detected. The detection signal of each magnetic sensor 8 is input to the microcomputer 9, and the microcomputer 9 controls the DC power supply 7 according to the strength of the leakage magnetic field at each position of the door to supply current to each solenoid coil 4a, 4b, and 4C. By changing the size and direction of the magnetic field, the leakage magnetic field acting on the door can be effectively canceled.

For example, the three solenoid coils 4a, 4b, 4c
The magnetic field generated by this is in the solid line state shown in FIG. 4 at each position in the lateral direction of the door 2, and the combined value thereof is shown by the dashed line. In addition, the leakage magnetic field from the strong magnetic field generator is in the opposite direction at each position in the lateral direction of the door, as shown by the broken line in Figure 4, and the magnetic field generated by the three solenoid coils 4a, 4b, and 4c almost eliminates this leakage magnetic field. I know it can be canceled out.

In the embodiments described above, solenoid coils were provided on both the door and the periphery of the chamber wall opening, but in the case of a small door, it is possible to cancel the leakage magnetic field to some extent by providing the solenoid coil on only one of them.

"Effects of the Invention" According to the magnetically shielded room door of the present invention, the solenoid coil provided inside the door or on its outer periphery can cancel out the leakage magnetic field from the strong magnetic field generator to the door. The leakage magnetic field from the part to the outside can be reduced. Furthermore, by providing a plurality of solenoid coils in the door portion, leakage magnetic fields can be canceled with high accuracy, and uneven leakage magnetic fields can also be canceled. In addition, when the door is closed, the polarity of the indoor side of the yoke material is different from the leakage magnetic field, so the door is attracted, but by adjusting the current supplied to the solenoid coil when opening the door, it can be prevented from being attracted ( Can be opened easily.

Furthermore, by being able to magnetically shield the room door, the degree of freedom in setting the door position increases, and there is no need to take into account the distance attenuation of the magnetic field generated from MHI, etc., so the area of the MRI room can be kept small, and the Since the distortion of the magnetic field becomes small, adjustment using shim coils is also easy.

[Brief explanation of the drawing]

FIG. 1 is a plan sectional view of the magnetically shielded room door of the present invention, FIG. 2 is a front view of the door showing the arrangement of solenoid coils, and FIG. 3 is a graph showing magnetic force changes in the door portion due to each solenoid coil. FIG. 4 is an explanatory diagram showing the state of the magnetic field in a conventional MRI room.

Claims (4)

[Claims] (1) At the door of the magnetically shielded room where the strong magnetic field generator is installed, a solenoid coil is placed on the door and the outside of the solenoid coil is covered with a ferromagnetic material to cancel the leakage magnetic field from the strong magnetic field generator to the door. A door for a magnetically shielded room, which is characterized by a magnetically shielded room door. (2) A solenoid coil is disposed on the wall of the magnetically shielded room around the outer periphery of the door, and the outside of the solenoid coil is covered with a ferromagnetic material to cancel the leakage magnetic field near the periphery of the door. Door for magnetically shielded room. (3) Claim 1 characterized in that a plurality of rectangular solenoid coils of different sizes are arranged concentrically on the door.
Or the magnetically shielded room door described in 2. (4) The door for a magnetically shielded room according to claim 3, wherein the door is provided with an appropriate number of magnetic sensors, the detection signals are inputted to a microcomputer, and the microcomputer controls the current supplied to the plurality of solenoid coils.