JPH03966Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a nuclear magnetic resonance imaging apparatus (referred to as NMR-CT) having a permanent magnet type static magnetic field generator.

(B) Prior Art The device on which the present invention is based consists of a pair of permanent magnets that are arranged opposite to each other with a gap between them, and a magnetic yoke that magnetically couples the magnets and forms a substantially sealed space inside. This is a static magnetic field generator constructed of

In order to achieve a uniformity of about 10 ppm in the magnetic field to obtain good image quality with this device, a shim coil for magnetic field correction must be installed in a closed space. Furthermore, in order to generate an NMR signal, a gradient coil for forming a gradient magnetic field must be provided. These coils must be able to be inserted and removed from the insertion opening provided in the yoke for inspection and adjustment.

(c) Problems to be solved by the invention In answering the above request, the following technical problems exist. In other words, when attaching a shim coil and a gradient coil to a yoke, the structure becomes complicated depending on the mounting structure, and if both coils are formed integrally, the vertical width of the coil insertion opening becomes wide, and the magnetic The drawback was that performance deteriorated.

The present invention attempts to solve the above drawbacks.

(d) Means for solving the problem The present invention includes a fixing member made of a non-magnetic material that fixes a permanent magnet to the inner surface of the magnetic yoke at its peripheral edge, and a fixing member that is inserted into the magnetic yoke through the insertion opening and attached to the fixing member. The above problem has been solved by having a separate shim coil plate and gradient coil plate that are fastened together by non-magnetic screws and are superimposed and fixed.

(e) Effect By the above means, the shim coil plate and the gradient coil plate are separately inserted into the yoke from the insertion opening, and then superimposed and fixed with screws to the fixing member for fixing the permanent magnet.

(F) Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 4. 1 is a static magnetic field generator for NMR-CT.
2 and 2 are a pair of disk-shaped permanent magnets made of rare earth magnetic material; 3 and 4 are disk-shaped upper and lower yokes made of magnetic material that are arranged with one side of each permanent magnet in contact with each other; 5 is a pair of disk-shaped permanent magnets made of rare earth magnet material; A cylindrical side yoke made of a magnetic material is electromagnetically connected to the upper yoke and the lower yoke. A magnetic circuit is constructed with each yoke of
A static magnetic field of 3000 Gauss is created. Further, the side yoke 5 has a pair of circular openings 6, 6 arranged opposite each other for insertion of a subject (for example, a human body) into the static magnetic field. 8, 8 are a pair of pole pieces 9, 9 provided on the other surfaces of each of the permanent magnets 2, 2 in an opposing arrangement to improve the uniformity of the static magnetic field;
is a seat ring provided protruding from the upper inner surface of the side yoke 5 and supporting the upper yoke 3 and the lower yoke 4;
A side ring with an L-shaped cross section, which is disposed in contact with the side surface of the yoke and is screwed, for example, to the upper yoke 3 and the lower yoke 4 with non-magnetic screws 11. As well as being positioned, it is clamped and fixed by the upper yoke 3 or the lower yoke 4 and each side ring 10. The pole pieces 8, 8 are attracted to the magnets 2, 2, and are positioned by the side rings 10.

Referring to Fig. 2, 12 is a shim coil plate on which shim coils 13a, 13b, 13d, etc. of various shapes are attached, and by passing various constant currents through each shim coil 13a, non-uniformity of the magnetic field within the yoke is corrected. death,
Improve the uniformity of the magnetic field. The shim coil 13
The mounting of a... is carried out by forming a groove along the shape of the coil in a plate made of a non-magnetic material such as a synthetic resin, winding the coil around the groove, and bonding the coil with an adhesive.

Referring to FIG. 3, reference numeral 14 denotes a gradient coil plate to which a gradient coil 15 for generating a gradient magnetic field is attached in the same manner as a shim coil.

Both coil plates 12 and 14 have fixing holes 1 in advance.
6..., 17... are formed, while the side ring 10
Screw holes 18 are formed to match these fixing holes, and both coil plates 12 and 14 are overlapped and fastened together with non-magnetic screws 19 as shown in FIG. 1 to be fixed to the side ring 10. Ru. The positions of the above fixing holes 16..., 17... and screw holes 18... are X as shown in FIG. 2 and FIG.
Y, Z axis direction (Z axis direction is perpendicular to the paper surface) and X, Y,
It is set so that it coincides with the Z-axis direction (the Z direction is a direction perpendicular to the plane of the paper).

Further, 20, 20 are coil insertion ports for inserting or taking out both the coil plates 12, 14 into the yoke, and slits 20a, 20a are continuously provided at both ends of the openings 6, 6, and a part of the openings 6, 6 is inserted. and slits 20a, 20a
It is formed with a horizontal width L and a vertical width H. This vertical width H is wider than the thickness of each coil plate 12, 14, and narrower than the total thickness of both coil plates 12, 14. Therefore, both coil plates 12 and 14 are inserted into the yoke 5 separately and then fixed as described above.

(g) Effects According to the present invention configured as described above, the shim coil plate and the gradient coil plate can be fixed using the fixing member for fixing the permanent magnet, the fixing structure can be simplified, and the fixing member is non-magnetic. Since it is made of a body, there is no change in magnetic performance by forming the coil plate fixing hole in it. Furthermore, since the shim coil plate and the gradient coil plate are inserted as separate bodies through the coil insertion opening, the vertical width of the coil insertion opening can be narrowed, and magnetic performance can be improved.

[Brief explanation of the drawing]

FIGS. 1 to 4 all show an embodiment of the present invention, with FIG. 1 being a longitudinal sectional view, FIGS. 2 and 3 being a plan view of essential parts, and FIG. 4 being an external perspective view. 1...Static magnetic field generating means, 2...Permanent magnet, 3,
4, 5... Yoke, 10... Side ring (fixing member), 12... Shim coil plate, 14... Gradient coil plate, 19... Screw, 20... Coil insertion port.

Claims (1)

[Scope of utility model registration request] A static magnetic field generating device consisting of a pair of permanent magnets that are arranged facing each other with a gap between them, and a magnetic yoke that magnetically couples the magnets, forms a substantially sealed space inside, and has an insertion port formed on the side surface. A fixing member made of a non-magnetic material that fixes the permanent magnet to the inner surface of the magnetic yoke at its peripheral edge;
Nuclear magnetic resonance characterized by having a mutually separate cis-coil plate and gradient coil plate which are inserted into the magnetic yoke from the insertion port and are fastened together with non-magnetic screws to be superimposed and fixed to the fixing member. Imaging device.