JPH0450011Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a so-called RF (high frequency) coil for transmitting and receiving nuclear magnetic resonance signals used for diagnosing the human body, and more specifically, it relates to a so-called RF (high frequency) coil for transmitting and receiving nuclear magnetic resonance signals used for diagnosing the human body. The present invention relates to a surf coil for transmitting and receiving nuclear magnetic resonance signals.

Conventional technology For example, when diagnosing the human body using nuclear magnetic resonance signals, a required magnetic field is set, a high frequency is applied by a coil to cause the atomic nuclei to resonate, and the nuclear magnetic resonance signals from the subject are detected. receive.

Generally, the magnetic field strength used is 0.2 Tesla to 2 Tesla, so the resonance frequency of the atomic nucleus is approximately
5MHz to 600MHz. A surf coil used for diagnosing a required part of the human body consists of an inductor and a capacitor for eliminating the influence of the self-capacitance of the conductor. Most inductors are limited by the size of nuclear magnetic resonance magnets, and the maximum external dimensions are 1
cm to 30cm, circular shape with one or more turns, two
It is often formed in a spiral shape with ~3 turns or more, and spatially fits around the head, eyes, arms, neck, etc. of a human subject. It is known that in the case of an annular inductor, the magnetic field generated by an inductor has sufficient strength and extends up to a distance of the radius of the annular ring in the perpendicular direction. Therefore,
Conventional surf coils are generated at a distance that can be called the geometric equivalent radius of the inductor, that is, when the inductor is placed on the human body surface, the inductor is generated from the human body surface to the depth of the inductor's geometric equivalent radius. This is the area where the magnetic field reaches. Also, when receiving nuclear magnetic resonance signals, it was possible to receive the nuclear magnetic resonance signals from a point at a distance of the geometrically equivalent radius of the inductor.

Problems to be Solved by the Invention There is often a need to observe nuclear magnetic resonance phenomena in tissues that exist at a relatively shallow distance in the direction perpendicular to the inductor contact surface, such as human skin or facial expression muscles. However, even if one attempts to observe only nuclear magnetic resonance phenomena in the skin, if a conventional SURFS coil is used, the magnetic field generated by the inductor will extend over a relatively long distance, making it difficult to observe nuclear magnetic resonance phenomena in muscle tissue deeper than the skin. As a result, signals from muscle tissue were often observed together as undesirable background signals. In other words, when you want to observe a fairly wide range, harmful signals from a relatively deep place perpendicular to the contact surface will affect the contact surface, and conversely, if you make the coil smaller to avoid that negative effect, it will affect the signal from a shallower place. Although only the signal can be observed, there is a problem in that it cannot cover the wide area required.

The present invention was developed in view of the above points, and its purpose is to generate magnetic sensitivity in a relatively shallow area perpendicular to the coil, and to spread magnetic sensitivity over a required area within the same plane. Our goal is to provide a surf coil that can be used as a surfboard.

Means for Solving the Problems The present invention is a surf coil for a nuclear magnetic resonance apparatus for transmitting high frequency signals or receiving nuclear magnetic resonance signals, and is designed to cancel the magnetic field far from the observation area. A SURF S coil is characterized in that a plurality of coil wire elements are arranged facing each other at approximately equal intervals in the same plane. The SURF S coil wire element of the present invention is arranged over the required area corresponding to the measurement area to be contacted such as the subject to be diagnosed, and although it is often located in the same plane, If the subject part is curved, it may be set to be curved or flexible. Coil wire elements are arranged facing each other around each point in the area, and when the opposite is actually two coil wire elements facing each other, or two sets of parallel coil wire elements, the opposite is a polygon. There are no special restrictions, such as when it consists of a coil element surrounded by a coil element. Currents in opposite directions are generated in the opposing coil wire elements. That is, at each point within the region, a current is generated in the surrounding opposing coil wire elements in the same moment direction vectorwise at each point. Magnetic sensitivity includes cases in which a magnetic field is applied to a subject by a SURF S coil, and cases in which a SURF S coil receives nuclear magnetic signals from the subject. In the former case, a current is supplied to the SURF S coil from a high-frequency oscillator, and in the latter case, a current is generated in the SURF S coil by a nuclear magnetic signal from the subject, etc., and is communicated to the SURF S coil. is sent to the receiving device.

Effect When current flows through a conductor, a magnetic field is generated around it. When the forward and return paths of a conductor with mutually opposite directions are placed close to each other, in the immediate vicinity of either the forward or return path of the conductor, a current generated in the direction flowing in the conductor on the near side is generated. A magnetic field is generated. Since the magnetic field at a point far from both the outward and return paths is canceled as a vector sum of the respective magnetic fields generated by the currents flowing through the conductors of the outbound and return paths, the SURF S coil of the present invention The magnetic field generated by the inductor is
It does not extend far vertically to the surf coil.
The distance that the generated magnetic field extends from the surface of the coil wire of the SURF S coil is calculated using the Biot-Savart law for the current flowing through each of the conductors constituting the inductor.

Embodiment In FIG. 1, coil wire elements 1 are arranged parallel to each other in a zigzag pattern on the same plane of a rectangle measuring 35 mm x 55 mm. The coil wire elements 1 are arranged facing each other over the entire rectangular area, and the interval between adjacent coil wire elements 1 is set to 5 mm. In terms of form, metal wires such as copper are fixed to a sheet made of a material such as synthetic resin with good electrical insulation, high frequency loss characteristics, heat resistance, and flexibility, or methods such as printed wiring. There are no particular restrictions, such as those in which a coil wire element is formed on the base. Coil wire element 1
The end thereof is connected to a required high frequency transmitting/receiving device (not shown) via a terminal 2 and a conductive wire 3.

When a high frequency wave is applied to the SURF S coil shown in FIG. 1 from a high frequency transmitter or the like, a current flows through the coil wire element 1 in the direction of the arrow at a certain moment. Each point in the entire rectangular area (strictly speaking, other than the points on the coil wire element 1) is surrounded by a coil wire element 1 that faces each other, and current flows in the opposite direction through the opposing coil wire elements 1.
At the moment when the flow direction of the high-frequency current is reversed, the direction of the current flowing through the coil wire element 1 becomes opposite to the arrow in Fig. 1, but the opposite coil wires around each point in the area A current in the opposite direction flows through element 1.

In the actual SURF S coil of nuclear magnetic resonance diagnostic equipment, a capacitor C is usually installed between the terminals 2 to eliminate the influence of the self-capacitance of the conductor, as shown in Figure 2. This also applies to the present invention.

The above explanation deals with the case where a magnetic field is generated by applying a current to the SURF S coil, but the same applies when a current is generated in the SURF S coil due to a magnetic field such as a nuclear magnetic signal and is transmitted to an external receiving device, etc. applied to.

In FIG. 4, which is another embodiment, coil wire elements 1 are arranged concentrically on a circular plane having a diameter of 35 mm with an interval of 5 mm. The coil wire elements of each circle are cut out at a part of the circle and connected to the coil wire elements of the adjacent circle. Terminal 2 on the outermost coil wire element
is provided, and is connected to a required high frequency transmitting/receiving device etc. via a conductor 3. Currents in opposite directions flow in the coil wire elements 1 facing each other around each point in the area.

Although the area is circular in FIG. 4, it is easily possible to form it in an elliptical shape, or in a square or rectangular shape using the same concept of relative arrangement.

In FIG. 5, which is another embodiment, rectangular wave-like coil wire elements 1A and 1B are arranged in a grid pattern as a whole with respective bending points close to each other. Coil wire element 1
Both ends of A and 1B are connected to internal conductors 4A and 4B so that current flows in opposite directions in every other wire. The internal conducting wires 4A, 4B are connected to a required high frequency transmitting/receiving device etc. via terminals 2A, 2B and conducting wires 3A, 3B. Currents in opposite directions flow through the opposing coil wire elements 1A and 1B around each point in the area. In this case, since the upper and lower ends of FIG. 5 do not have a uniform magnetic field, the size of the SURF S coil may be designed to be somewhat larger than the required diagnostic area.

In FIG. 6 showing the main part of yet another embodiment,
Coil wire elements 1A are arranged in parallel at equal intervals, coil wire elements 1B are arranged in parallel at equal intervals and intersect at an angle of 60 degrees, and coil wire elements 1C are arranged in parallel at equal intervals at an angle of 120 degrees. Arranged in parallel at intervals. The coil wire elements 1A, 1B, and 1C are electrically insulated at each intersection point. The current flows from an internal conductor (not shown) to the right in coil wire element 1A, and to the right in coil wire element 1B.
In the case of the coil wire element 1C, it flows diagonally downward to the left, and in the case of the coil wire element 1C, it flows diagonally upward to the left. Internal conductors, terminals, conductors, etc. are arranged in the same manner as in the previous embodiment.

The high frequency current has a property of flowing on the surface of a coil wire element, and in this case, for example, a plate-shaped coil wire element as shown in FIG. 7 is used. In FIG. 7, copper plates having a thickness of 0.3 mm and a width of 5 mm are formed in parallel in a zigzag shape with an interval of 5 mm. Required conductor wires and the like are connected to both ends. This coil wire element is 10~
Can be used for high frequency requirements of 100MZz.

Effects As explained above, the present invention can be used as a surf coil that generates a magnetic field in a direction perpendicular to a coil element to which a current is applied, or as a surface coil that generates a current in a coil element by a magnetic field such as a nuclear magnetic signal. When used as a SURF S coil to transmit the state of the magnetic field by the current, the magnetically sensitive range is specified within the vicinity of the SURF S coil in the vertical direction,
Moreover, since the size (required area) of the surface coil can be set independently of the above-mentioned neighboring values, it is extremely useful for a nuclear magnetic resonance information processing apparatus for diagnosing the condition of a subject such as a human body.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the situation of coil wire elements arranged in the required area in the same plane in one embodiment of the present invention, and Fig. 2 shows the connection of capacitors to eliminate the influence of the self-capacitance of the conducting wire. Figure 3 is a schematic diagram of a conventional SurfS coil, Figure 4 shows a wiring diagram showing the situation
5 is a schematic diagram showing the situation of coil wire elements arranged in a required area in the same plane in another embodiment, and FIG. 6 is a schematic diagram showing the main parts of a coil wire element in another embodiment. FIG. 7 is a perspective view showing a coil wire element of an embodiment for high frequency use. 1... Coil wire element, 2... Terminal, 3... Conductor wire,
4... Internal conductor, C... Capacitor, L... Inductor.

Claims (1)

[Scope of utility model registration request] A surf coil for a nuclear magnetic resonance apparatus for transmitting high frequency signals or receiving nuclear magnetic resonance signals.Multiple coil wire elements are arranged approximately in the same plane so that the magnetic field is canceled in areas far from the observation area. Surf S coils are characterized by being arranged facing each other at equal intervals.