JPH0718301B2 - 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, a magnetic resonance diagnostic device (hereinafter referred to as MRI) has been installed in a hospital, but there are patients who have pacemakers installed in the hospital, 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 gaps for magnetic and radio wave 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. At the entrance and exit of the MRI room, a stretcher carrying a patient and treatment equipment go in and out, so the size is about 1400 mm in width and 2100 mm in height, for example, and a large door is 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.

Since the magnetic field is generated from the 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 stray magnetic field from I could not be reached.

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 Problems" The magnetic shield room door of the present invention has a solenoid coil arranged in the door of a room equipped with a strong magnetic field generator,
The outside of the solenoid coil is covered with a ferromagnetic material so that the leakage magnetic field to the door can be canceled.

In order to more effectively cancel the leakage magnetic field at the door portion, a solenoid coil may be arranged on the wall portion of the magnetic shield room on the outer periphery of the door to cancel the leakage magnetic field near the periphery of the door. Further, the solenoid coil arranged on the door may be formed in a plurality of rectangular shapes having different sizes, and they may be arranged concentrically to effectively cancel the leakage magnetic field. Further, a magnetic sensor is provided on the door, and the microcomputer can control the current supplied to the plurality of rectangular solenoid coils according to the detected value.

"Operation" 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 in the door, the magnetic field generated from the magnetic field leaks from the strong magnetic field generator to the door part. Can be canceled. Outside the rectangular solenoid coil provided on the door surface, the magnetic field generated by the solenoid coil is in the same direction as the leakage magnetic field, but the magnetic field acts outside due to the ferromagnetic material provided outside the solenoid coil. Is suppressed, and the stray magnetic field is not strengthened.

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

The leakage magnetic field that acts on the door changes depending on the opening angle of the door, but multiple solenoids are installed on the door and solenoid coils are installed on the chamber wall around the door. The door can be opened and closed more easily by controlling the magnitude and direction of the current supplied to each solenoid coil by a microcomputer in response to the signal to cancel the leakage magnetic field acting on the door portion. Although the indoor polarity of the ferromagnetic material provided in the solenoid coil with the door closed is different from the leakage magnetic field, it is attracted, but when the door is opened, by controlling the current supplied to each solenoid coil, You can prevent the door from being sucked.

[Example] An example 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 a magnetic shield wall A made of pure iron and a radio wave shield wall B such as copper foil, the door 2 of the room 1 is installed.
Was magnetically shielded by the following configuration. A stainless frame 3 is provided around the opening of the chamber 1 in which the door 2 is provided.
Although illustration is omitted, finger contacts for radio wave shielding are provided on the inner peripheral surface of the stainless steel frame 3, and the radio wave shielding wall B is electromagnetically connected to a stainless plate forming a door described later.

The door 2 is formed of a non-magnetic stainless plate in a hollow shape, and two rectangular solenoid coils 4a and 4b having different sizes are concentrically arranged in the hollow portion. In addition, although two solenoid coils are provided in this embodiment, even one solenoid coil is provided.
However, the shape is not limited to the rectangular shape. Each solenoid coil 4a, 4b is covered with ferromagnetic materials 5a, 5b on the outer three sides with respect to the center of the door. This is because the magnetic field generated by itself on the outside of 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 bodies 5a and 5b function as a yoke, and can strengthen the magnetic field on the side not covered with the ferromagnetic body.

Solenoid coil 4c is also provided on the periphery of the opening of the wall where the door 2 is provided.
Are arranged, and the three sides of the solenoid coil 4c excluding the door facing surface are covered with the ferromagnetic material 5c. As with the above, the ferromagnetic material 5c is provided so that the leakage magnetic field is not strengthened on the side opposite to the door side.
Moreover, it is to function as a yoke. Ferromagnet 5c
Is magnetically connected to the magnetic shield wall A provided on the chamber wall so that the portion of the solenoid coil 4c can be effectively magnetically shielded.

Each of the solenoid coils 4a, 4b, 4c is a copper wire.
A current is supplied from a stabilized DC power supply 7 which is constructed by winding 10 to several hundreds of turns. Further, a plurality of magnetic sensors 8 are provided on the entire surface of the door 2 so that the strength of the leakage magnetic field from the ferromagnetic substance 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, 4c. By changing the size and direction of the magnetic field, the leakage magnetic field acting on the door is effectively canceled.

For example, the magnetic field generated by the three solenoid coils 4a, 4b, 4c 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 one-dot chain line. Further, the leakage magnetic field from the strong magnetic field generator is in the opposite direction as shown by the broken line in FIG.
It can be seen that the magnetic field generated by the two solenoid coils 4a, 4b, 4c can almost cancel this leakage magnetic field.

In the above embodiments, the solenoid coil is provided on both the door and the peripheral edge of the opening of the chamber wall. However, with a small door, it is possible to cancel the leakage magnetic field to some extent only by providing it on one of them.

[Advantages of the Invention] According to the magnetic shield room door of the present invention, the leakage magnetic field from the strong magnetic field generator to the door portion can be canceled by the solenoid coil provided in the door or in the outer peripheral portion thereof. The leakage magnetic field from the part to the outside can be reduced. Further, by providing a plurality of solenoid coils on the door portion, it is possible to cancel the leak magnetic field with high accuracy, and it is also possible to cancel the non-uniform leak magnetic field. In addition, since the polarity of the yoke material on the indoor side is different from the leakage magnetic field when the door is closed, the door is attracted, but when the door is opened, it is not attracted by adjusting the current supplied to the solenoid coil. Can be opened to

In addition, since the door of the room can be magnetically shielded, the degree of freedom in setting the position of the door is increased, and since it is not necessary to consider the attenuation of the magnetic field generated by MRI etc., 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]

FIG. 1 is a plan sectional view of a door for a magnetically shielded room according to the present invention, FIG. 2 is a front view of the door showing an arrangement state of solenoid coils, and FIG. 3 is a graph showing a change in magnetic force of the door portion by each solenoid coil. FIG. 4 is an explanatory diagram showing a magnetic field state in a conventional MRI room. 2; Door, 4a, 4b, 4c; Solenoid coil 5a, 5b, 5c; Ferromagnetic material, 7; Power supply 8; Magnetic sensor, 9: Microcomputer

Claims (4)

[Claims] 1. In a door of a magnetically shielded room in which a strong magnetic field generator is installed, a solenoid coil is arranged on the door and the outside of the solenoid coil is covered with a ferromagnetic material.
A door for a magnetically shielded room characterized by canceling a leakage magnetic field from the strong magnetic field generator to the door part. 2. A solenoid coil is arranged on the wall of the magnetically shielded room on the outer periphery of the door, and the outer side of the solenoid coil is covered with a ferromagnetic material so as to cancel the leakage magnetic field near the periphery of the door. Door for magnetically shielded room described in. 3. The door for a magnetically shielded room according to claim 1 or 2, wherein a plurality of rectangular solenoid coils having different sizes are concentrically arranged on the door. 4. The door for a magnetically shielded room according to claim 3, wherein an appropriate number of magnetic sensors are provided on the door to input a detection signal to the microcomputer, and the microcomputer controls the current supplied to the plurality of solenoid coils.