JPS63153055A - Magnetic resonance imaging apparatus - 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 (a) Industrial Application Field The present invention relates to magnetic resonance imaging for obtaining medically useful information such as tomographic images of the human body using nuclear magnetic resonance (hereinafter abbreviated as NMR). The present invention relates to a high-frequency coil for bag W (hereinafter abbreviated as 1 MRI apparatus).

(b) Conventional technology The MHI device detects a high-frequency magnetic field generated by the rotation of nuclear spins in a uniform static magnetic field in a plane orthogonal to the static magnetic field as an NMR signal using a receiving coil placed around the high-frequency magnetic field. This is a device that images the internal structure of a human body, etc., as a tomographic image.

In the MHI device, as a device for generating a static magnetic field, there are a magnet device using a permanent magnet, a magnet device using a normal conducting magnet, or a magnet device using a superconducting magnet. In the case of a magnet device using a permanent magnet, the direction of the static magnetic field is usually set in the vertical direction. In this case, the transmitting coil is arranged to generate a horizontal high frequency magnetic field, and the receiving coil is arranged so as to be sensitive to changes in the horizontal magnetic field. As the receiving coil, a solenoid type coil or a saddle type coil is generally used. Further, a surface coil that can obtain an NMR signal with a high S/N ratio (signal-to-noise ratio) is used as a receiving coil for a local area relatively close to the subject's body surface.

On the other hand, in the case of a magnet device using a normal conducting magnet or a superconducting magnet, the static magnetic field is set in the horizontal direction. In this case, a circular coil or a loop-shaped coil wound in a plane is used as the transmitting/receiving coil.

(c) Problems to be Solved by the Invention By the way, the transmitting/receiving coil must be placed close to the part of the human body to be imaged. Also, one normal subject is placed in a supine position within the magnetic device. Therefore, when imaging the vertebrae, medulla, or medulla oblongata.

For magnet devices that use normal conducting magnets or ultra-low 4 magnets.

Since circular coils and loop coils are flat, good images can be obtained by placing them under the subject's body.

However, when a circular coil or a loop-shaped coil is placed under the body, the direction of the magnetic field is vertical.

Cannot be used with permanent magnet devices. Furthermore, if these coils are arranged vertically, they will move away from the imaging site, making it impossible to obtain a good image. On the other hand, because of their shape, solenoid-type coils and saddle-type coils give subjects a sense of discomfort or discomfort when placed under the body.

In this way, when imaging vertebrae, medulla, or medulla oblongata, planar coils are suitable, but conventionally.

Planar coils have almost no sensitivity to horizontal magnetic fields, so they cannot be used when the static magnetic field is vertical.

An object of the present invention is to solve the above problems and provide a planar high-frequency coil for an MRI apparatus that has sufficient sensitivity to magnetic fields parallel to the coil surface.

(d) Means for solving the problem Therefore, in the present invention, a plurality of coils are arranged adjacently on a plane, and each coil is connected in series so that the direction of the loop current of each adjacent coil is opposite to each other. Alternatively, they may be connected in parallel to form a high frequency coil.

(e) Effect: The area between adjacent coils becomes sensitive to high-frequency magnetic fields parallel to the coil surface.

(F) Embodiments Below, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a magnetic resonance imaging apparatus (M
FIG. 3 is a plan view of a high-frequency coil of the HI device.

In the figure, this high frequency coil 1 is a rectangularly wound coil 1.
Two conductive loops la and lb of the turn are formed adjacent to each other in a plane and are connected so that the loop currents i flowing through the conductive loops la and lb are in opposite directions.

The high-frequency coil 1 is used by being placed under the back of a subject 3 who is in a supine position in a permanent magnet device 2, as shown in FIG. At this time, in order to avoid giving subject 3 a sense of discomfort or discomfort, the high-frequency coil 1
It is thin and has a soft shape that curves along the body surface.

Next, the principle of the high frequency coil 1 of this embodiment will be explained. Now, if a constant current is passed from terminal a to b of the high-frequency coil 1, the lines of magnetic force in the conductive loop 1a will be directed upward, and the lines of magnetic force in the conductive loop 1b will be directed downward, creating a composite magnetic field as shown in Figure 3. It is formed. As shown in region 4 in the figure, the direction of the magnetic lines of force becomes parallel to the plane of the high-frequency coil 1 at an intermediate position between the conductive loops 1a and 1b.

By the way, in general, the direction of magnetic lines of force generated when a coil is energized indicates that the coil is sensitive to the lines of magnetic force in that direction according to the reciprocity theorem. Therefore, the high-frequency coil 1 is sensitive to lines of magnetic force parallel to the coil surface in region 4 of FIG. 3, and thus induces an electromotive force in the high-frequency magnetic field in such a direction.

As a result, in the MHI device using the magnet device 2 that generates a static magnetic field in the vertical direction as shown in FIG. By arranging the high-frequency coil 1 in this way, it is possible to detect a horizontal high-frequency magnetic field and obtain tomographic images of those parts.

Similarly, by appropriately selecting the arrangement of the high-frequency coil I, tomographic images of the breast, eyes, nose, etc. can also be obtained.

In this way, by arranging the two conductive loops 1a and 1b adjacent to each other on a plane and connecting them so that the current directions are opposite to each other to form the high-frequency coil 1, an intermediate position between the two conductive loops 1a and 1b can be formed. This allows it to be sensitive to horizontal magnetic fields. In this case, the high-frequency coil 1 placed on a flat surface does not give the subject any discomfort or discomfort when placed under the back, so it is suitable for obtaining tomographic images of the vertebrae, medulla, or medulla oblongata. Become something.

In this embodiment, the conductive loops la and lb have one turn, and each loop is rectangular. However, any number of turns can be formed, and the shape can be changed, for example, as shown in FIG. 4(a).

It goes without saying that it can be formed into any desired shape, such as a semicircle or a circle, as shown in (b). At this time, as in the case of FIG. 4(a), if the section where the two loops are adjacent to each other and their lines are parallel is made longer, the sensitivity region will be wider.

It is also possible to arrange three or more coils on a plane to detect high frequency magnetic fields at two or more locations. moreover,
Even if a plurality of conductive loops are connected in parallel as shown in FIG. 5, the same function can be obtained.

(G) Effects of the Invention As described above, according to the present invention, a high-frequency coil is formed by arranging a plurality of coils adjacent to each other on a plane, so that a horizontal high-frequency magnetic field can be detected in the area sandwiched between the coils. , a planar high-frequency coil having sensitivity in a direction parallel to the coil surface can be obtained. This makes it possible to easily obtain local tomographic images of the spinal cord and similar areas while the subject remains in a normal back-up posture even in a magnet device that uses a permanent magnet that generates a vertical static magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a high-frequency coil of a magnetic resonance imaging apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of a permanent magnet device, and FIG. 3 is a cross-sectional view taken along line A-A' in FIG. 4(a), 5(b), and 5 are plan views showing other embodiments of the high-frequency coil. ■...High frequency coil, la, lb...conductive loop, 2...permanent magnet device. Figure 1 Figure 3 Figure 4 (a) (b) b

Claims (1)

[Claims] A magnetic resonance imaging device that uses a high-frequency coil that is placed around a subject placed in a uniform static magnetic field generated by a magnet device, and that generates a high-frequency magnetic field and/or receives a high-frequency signal. The high-frequency coil is composed of a plurality of conductive loops arranged adjacently on the same plane, and each conductive loop is connected so that loop currents in opposite directions flow through the adjacent conductive loops. Magnetic resonance imaging device.