JPH02159595A - Magnetically shielded room window - 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 is directed to a magnetically shielded room that prevents the leakage of magnetic fields to the outside from a room in which a strong magnetic field generator such as a magnetic resonance diagnostic instrument (MHI) is installed. This invention relates to a window for a magnetically shielded room in which a window is provided to see through the interior of the room and the window is magnetically shielded.

"Prior Art" Recently, hospitals have begun to install magnetic resonance diagnostic equipment (hereinafter referred to as MHI), but in addition to patients with pacemakers, there are also devices such as computers that are adversely affected by magnetism. There are many devices available. Therefore, in the room where the MRf is installed, a magnetic shield A made of a ferromagnetic material such as pure iron is installed on four or six sides of the room, as shown in Figure 4, in order to prevent leakage of magnetic fields to the outside.

Radio wave shields B are installed on six sides of the room to block the influence of external radio waves.

The room where the MHI is installed is equipped with windows and entrances and exits to allow the inside to be viewed from the outside, but if there are gaps in the area where these are installed, the effectiveness of both shields will be significantly reduced. The gaps in the room where the MHI etc. are installed are completely welded, all soldered, etc. to eliminate any gaps that may cause magnetic leakage. In addition, the openings such as the entrance and exit of the room are also equipped with radio wave shielding such as stainless steel plates, shielding glass, and finger contacts.

However, when it comes to magnetic shielding, the magnetic material used is heavy and opaque.

It cannot be applied to window areas where transparency is required.
The size of the window is 1000+nn wide to see through the interior of the room.
+, Although a height of about 800 mm is desirable, the current situation is to make the windows as small as possible in order to reduce the leakage magnetic field from the windows.

``Problems to be Solved by the Invention'' In conventional MHI rooms, it is not possible to provide magnetic shielding to the windows, and in that case, a large amount of magnetic field leaks from the window portion. That is, as shown in Figure 4, 1.57 (terrace)
When installing MHL, I, the 5G (Gauss) line, which is a controlled area where pacemaker wearers are prohibited from entering and the guideline for computer installation, spreads out from the window area, causing many management problems.

Furthermore, if an attempt is made to keep the leakage magnetic field small by placing the window as far away from the MHI as possible and utilizing distance attenuation, the room area will increase or the window position will be restricted, causing problems in architectural planning. Furthermore, large distortions occurred in the magnetic field distribution in the MHI chamber, making it difficult to make adjustments using shim coils to prevent distortions from occurring in MHI images.

In order to suppress the generation of a strong magnetic field from the MHI, it is possible to cut off the power supplied to the MHI except during inspections, but the currently mainstream superconducting type MHI uses a superconducting electromagnet and generates a persistent current. The MRT was in full operation 24 hours a day, making it impossible to suppress the magnetic field generated from the MRT6.Therefore, the present invention provides effective magnetic shielding to the windows of the magnetically shielded room to suppress the leakage of the magnetic field to the outside. With the goal.

"Means for Solving the Problems" The window for a magnetically shielded room of the present invention has a solenoid coil arranged around the window frame of a magnetically shielded room in which a strong magnetic field generator is installed, so that a solenoid coil is connected from the strong magnetic field generator to the window part. The leaked magnetic field was canceled out.

In order to magnetically shield the magnetic field generated on the opposite side of the solenoid coil from the window frame, a ferromagnetic material may be provided in the solenoid coil except for the window frame side.

"Operation" The magnetic shielding window of the above means has a solenoid coil arranged around the window frame, and the magnetic field generated by the solenoid coil cancels the magnetic field leaked from the strong magnetic field generator to the window, so that the magnetic field leaks from the window to the outside. The magnetic field can be reduced.

The effect of canceling the leakage magnetic field at the window in this way will be explained with reference to FIG. FIG. 3(A) shows a state in which the magnetic field generated by the MHI leaks outside from the window when the window W provided in the magnetic shield wall M is not magnetically shielded. FIG. 3(B) shows the magnetic field generated from the solenoid coil S when the solenoid coil S is arranged around the window frame, and the relationship is that of the leakage magnetic field from the MHI and the opposite magnetic field. The maximum magnetic field is at the window, and the field attenuates as you move away from the window.

FIG. 3(C) is a combination of the above two cases, in which the leakage magnetic field from the MHI is canceled by the magnetic field generated from the solenoid coil S at the window portion.

In the window portion, the magnetic field becomes approximately O, and outside the window, both magnetic fields decrease as they move away from the window W, so they cancel each other out and become approximately 0. Also, inside the window, the magnetic field generated by the solenoid coil S weakens as it approaches the MHI, while the MH
Since the leakage magnetic field from I becomes larger as it approaches MHI, the ratio at which the leakage magnetic field decreases decreases, and the MH
Near l, the magnetic field of the solenoid coil S has almost no effect.

"Example" An embodiment of the present invention will be explained with reference to FIG. 1.2.

In a room where a device that generates a strong magnetic field, such as a magnetic resonance diagnostic instrument (MHI), is installed, the peripheral wall is covered with a wall finishing material 1, such as a magnetic shielding material 2 made of pure iron plate, from the outside to the inside.
, a radio wave shield panel 3 is provided, and a wall finishing material 1 is also provided.
A base H steel 4 is provided between the magnetic shield material 2 and the magnetic shield material 2 .

A window 5 is provided in the room by opening the peripheral wall in order to see through the interior.A window frame 6 made of non-magnetic stainless steel is attached to the opening edge of one peripheral wall, and a transparent radio wave is installed inside the window frame 6. The shield glass 7 is attached in duplicate.

A solenoid coil 8 is arranged within the wall around the window frame 6,
A DC stabilized power source 9 is connected to the solenoid coil 8, so that the solenoid coil 8 generates a magnetic field that cancels the leakage magnetic field from the MHI etc. to the window portion. The solenoid coil 8 is made of several tens or hundreds of copper wires, for example.
It is formed by winding it, and the magnitude of the magnetic field can be changed by changing the magnitude of the current supplied to it, and the direction of the magnetic field can be changed by changing the direction of the current.

Then, the magnitude and direction of the leakage magnetic field when the MHI is used is measured by a sensor, and the supplied current is adjusted so as to be suitable for canceling the leakage magnetic field at the window.

A ferromagnetic material 10 is arranged on three sides of the solenoid coil 8 except for the window frame 6 side, so that a magnetic field does not act from the solenoid coil 8 toward the outside of the window frame. In other words, the magnetic field acting from the solenoid coil 8 toward the outside of the window frame is MH
Although it is in the same direction as the leakage magnetic field from I and increases it, the ferromagnetic material 10 can prevent its increase. Further, the ferromagnetic material IO acts as a yoke of the solenoid coil 8, and can strengthen the magnetic field generated from the solenoid coil 8. In this example, the ferromagnetic material lO is formed into a U-shaped cross section by the cut stem material 10a (for example, made of SS41) and the end of the magnetic shielding material 2 on the window frame 6 side, but the ferromagnetic material lO may be formed into a U-shaped cross section using a ferromagnetic material without using a part of the magnetic shielding material 2.

Also, if the area of the window 5 becomes large and the difference in the distribution of the magnetic field inside the solenoid coil 8 becomes large, a Herholk coil type in which two solenoid coils are arranged in parallel can be used.
The uniformity of the internal magnetic field can be increased.

"Effects of the Invention" In the magnetically shielded room window of the present invention, a solenoid coil is arranged around the window frame of the window of the magnetically shielded room, and the solenoid coil is used to generate a magnetic field that cancels the leakage magnetic field from the indoor strong magnetic field generator to the window. Since the magnetic field is generated in the coil, the leakage magnetic field from the window can be significantly reduced. Although magnetic field leakage can be prevented in this way, there is no need to provide any magnetic shielding material on the window surface, so the transparency of the window is not impaired.

In addition, by preventing magnetic field leakage, it is possible to keep the 5G line around the magnetically shielded room small, reducing the control area and increasing the flexibility of installing computers.It also increases the freedom of setting window positions, making architectural planning easier. Become. Furthermore, since magnetic field leakage from the window can be prevented, there is no need to greatly attenuate the magnetic field over distance, so the area of the MRI room can be kept small, and since the number of magnetic field types in the room is small, adjustment using shim coils is easy.

[Brief explanation of the drawing]

Fig. 1 is a horizontal sectional view of a window portion for a magnetically shielded room according to the present invention, Fig. 2 is an external view of the window portion for a magnetically shielded room, and Figs. 3 (A), (B), and (C) are according to the present invention. FIG. 4 is an explanatory diagram showing the magnetic field leakage prevention effect of the conventional magnetic shield room. 2; Magnetic shielding material 5; Window 8: Solenoid coil 10: Ferromagnetic material

Claims (2)

[Claims] (1) In a window installed for internal viewing in a magnetically shielded room where a strong magnetic field generator is installed, a solenoid coil is placed around the window frame to generate a magnetic field that cancels the leakage magnetic field from the strong magnetic field generator to the window area. A magnetically shielded room window characterized by: (2) The window for a magnetically shielded room according to claim (1), characterized in that a ferromagnetic material for magnetic shielding is provided in a portion of the solenoid coil provided around the window frame except for the window frame side.