JPH03964Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention is a nuclear magnetic resonance imaging device (hereinafter referred to as NMR-
(referred to as CT).

(b) Conventional technology In NMR-CT, it is necessary to form a highly uniform static magnetic field. The static magnetic field generating device that forms such a static magnetic field is generally equipped with the Japanese Clinical 41
As seen in Volume 7, No. 7 (71983), pages 254 to 257, normal magnets, superconducting magnets, or permanent magnets are used.

A device using a normal conducting magnet consumes a large amount of power, and also generates heat due to the application of a large current, which requires a cooling device to prevent the temperature from rising, resulting in a large device. Furthermore, in those using superconducting magnets, liquid helium or liquid nitrogen must be regularly replenished to maintain the superconducting state, which poses a problem in maintaining the superconducting state.

The solution to these problems is to use permanent magnets. In such a case, there is no need for a cooling device or replenishment of liquid helium, etc., making it extremely economical to maintain.

By the way, as a static magnetic field generating means using this kind of permanent magnet, a structure shown in FIG. 3 has been prototyped. 3, in the static magnetic field generating means 1 shown in the figure, 2, 2 are a pair of upper and lower disc-shaped permanent magnets made of rare earth magnet material;
5 is a disc-shaped upper yoke and a lower yoke made of a magnetic material arranged in contact with one side of each of the permanent magnets, and 5 is a cylindrical yoke made of a magnetic material that is electromagnetically connected to the upper yoke and the lower yoke. Use the side yoke to seal this opening with the upper yoke 3.
By disposing the lower yoke 4, each of these yokes constitutes a magnetic circuit, and a strong static magnetic field is formed between the pair of permanent magnets 2, 2 facing each other. The side yoke 5 also has a pair of circular openings 6', 6' arranged opposite each other for placing a subject (human body) in the static magnetic field. 8, 8 are provided on the other surface of each of the permanent magnets 2, 2 in a facing arrangement,
A pair of pole pieces 9, 9 for improving the uniformity of the static magnetic field are shim coils for magnetic field correction provided inside the pole piece 8. In order to insert this coil, the left and right sides of the openings 6', 6' are inserted. Notch 10 at the end,
They form a pair of 10.

In such a conventional configuration, since the openings 6', 6' are configured in a circular shape, the upper and lower ends of the openings 6', 6' are unnecessary for inserting the subject, and a strong magnetic flux is generated from these parts. The leakage could not be ignored.

(c) Problems to be solved by the invention In view of the above-mentioned drawbacks, the present invention aims to minimize leakage magnetic flux and reduce various drawbacks associated with magnetic flux leakage.

(d) Means for solving the problems The present invention solves the above problems by forming the opening for inserting the subject in the magnetic yoke into a flat shape whose vertical width is narrower than its horizontal width.

(E) Effect With the above means, the vertical width of the opening is narrower than before, so leakage of magnetic flux is reduced. In addition, since the left and right width of the opening is long, there is no problem when inserting a subject in a restrained state through the opening.

(f) Example An example of the present invention will be described with reference to FIG. Note that the same parts in FIG. 1 as in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. In Fig. 1, the difference from Fig. 3 is that the horizontal width L is larger than the vertical width H in order to reduce leakage magnetic flux from the openings 6, 6 for inserting the test subject.
Specifically, the opening 6, 6 has a circular part 6a with a diameter of 70 cm, and the shim coil, 9.
The string section 6 is substantially flush with the end surface 9a of the string section 6 and has a facing interval of 55 cm.
It is mainly composed of 6b and 6b, and the vertical width H is set to 55 cm, and the horizontal width L is set to 70 cm. The shapes of the openings 6, 6 are basically defined by the shape of the subject (human body). That is, the shoulder width of the subject in the depressed state is 45
cm, and the chest thickness is 20 to 25 cm. Based on this subject shape, the cross-sectional shape of an elliptical probe (not shown) into which the subject is inserted is determined. The cross-sectional shape of a tube (not shown) to be inserted between the openings 6 and 6 at both ends is determined, and this tube shape
The shape is determined.

Therefore, the shape of the openings 6, 6 is not limited to that shown in the drawings, but may be a shape in which point a and point b are connected by a string 6c as shown in FIG. In this case, since the aperture shape is entirely composed of strings, the aperture can be easily formed.

According to the configuration of the above-mentioned embodiment, the opening is narrower in the embodiment shown in FIG. 1 by the shaded areas A, A, compared to the conventional example, and in the embodiment shown in FIG. The opening becomes narrower by B, which reduces the leakage of magnetic flux from the openings 6, 6, and reduces various inconveniences caused by leakage, such as a person with a cardiac pacemaker disturbing his or her pace when approaching the device. .

(g) Effects According to the present invention configured as described above, leakage of magnetic flux from the permanent magnet type static magnetic field generating means can be reduced to the utmost, and various inconveniences caused by strong leakage magnetic flux can be easily reduced, etc. Great effect.

[Brief explanation of drawings]

Figure 1A is a front view of a partially cutaway main part of one embodiment of the present invention, Figure 1B is a front view of the main part of the same embodiment, and Figure 2 is a front view of the main part of another embodiment of the present invention. FIG. 3 is a front view of a partially broken main part of a conventional example. 1...Static magnetic field generating means, 2...Permanent magnet, 3,
4, 5... Yoke, 6... Opening, H... Vertical width,
L...Left and right width.

Claims (1)

[Scope of utility model registration request] Nuclear magnetism comprising a static magnetic field generating means consisting of a pair of upper and lower permanent magnets and a magnetic yoke that magnetically couples the magnets and forms a nearly sealed space, and has an opening for inserting a subject on the side surface of the magnetic yoke. A nuclear magnetic resonance imaging apparatus, wherein the aperture is formed into a flat shape with a vertical width narrower than a horizontal width.