JPS63179506A - High-frequency coil for nmr - Google Patents

Abstract

PURPOSE:To facilitate change in a resonance frequency of a high frequency coil of an NMR (nuclear magnetic resonance), by constituting a parallel/series circuit by an LC parallel resonance circuit comprising an inductor and a variable capacitor, which are connected in parallel, and a capacitor, which is connected in series to said LC parallel resonance circuit. CONSTITUTION:Protruding parts 11b of at least one pair of H type conductors 11 are coupled with fixed capacitors 2. At least one parallel/series circuit 4 is connected to each fixed capacitor 2 in parallel. The parallel-series circuit 4 is constituted by an LC parallel resonance circuit comprising an inductor 4a and a variable capacitor 4b, which are connected in parallel, and a capacitor 4c, which is connected in series to the LC parallel/series resonance circuit. The resonance frequency of the LC parallel resonance circuit in the parallel- series circuit 4 is made to agree with the first resonance frequency of a three- dimensional circuit. The synthesized impedance of the fixed capacitor 2 and the parallel/series circuit 4 is made to be capacitive. The three-dimensional circuit is resonated at the second resonance frequency. Thus, a high frequency coil for NMR, which is resonated with many frequencies, is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a high-frequency coil for NMR (nuclear magnetic resonance), and particularly to a high-frequency coil for NMR that can be applied to various types of nuclear spins such as protons, phosphorus, and sodium. be.

[Conventional technology]

Figure 4 shows, for example, [Journal of Magnetics]
Resonance (Journal of Magnetic
1 is a perspective view showing a conventional high-frequency coil for NMR shown in Hesonance) J, Vol. 36, pp. 447-451 (1979), and is arranged as shown in (1) in Fig. 1. These conductor plates (1) have a non-protruding part (la) called a vertical a band (Vertical band) and a protruding part (1b) called a wing (ving). (2) is inserted between adjacent protrusions (1b) and these protrusions (1b)
It is a fixed capacitor that capacitively couples. Note that the fixed capacitor (2) is soldered to the protrusion (1b). (
3) is a pair of conductor rings for electric field shielding, which are installed concentrically with the conductor plate (1) through an insulating layer (not shown) inside the protrusion (lb), and one conductor ring (3a ) is called the top Φ guard ring and the other conductor ring (3b)
is called the bottom Φ guard ring.

A conventional high-frequency coil for NMR is configured as described above, and the conductor plate (1), fixed capacitor (2), and conductor ring (3) form a three-dimensional circuit that equivalently functions as an LC series resonant circuit. Note that the conductor ring (3) is used for electric field shielding as described above, that is, for reducing dielectric loss within the measurement object due to the generated electric field when the measurement object is installed inside the NMR high-frequency coil. Note that this form of N
The high frequency coil for MR is called a slotted tube type.

[Problem that the invention seeks to solve]

With conventional high-frequency coils for NMR, when trying to receive NMR signals of protons and other nuclei such as phosphorus, it was necessary to change the resonant frequency of the high-frequency coil for NMR because these resonance frequencies differ. However, this change was not easy.

That is, when it is necessary to change the capacitance of the fixed capacitor (2) in FIG. 4, there is a problem in that it is not easy to replace the fixed capacitor (2) with one having a different capacitance.

This invention was made in order to solve the above-mentioned problems, and when receiving NMR signals of protons and other nuclei such as phosphorus, it is possible to easily switch between protons and other nuclei such as phosphorus.
The purpose is to obtain a high frequency coil for MR.

[Means for solving problems]

The high-frequency coil for NMR according to the present invention has at least one parallel-series circuit connected in parallel with each fixed capacitor that capacitively couples the protrusions of at least one pair of H-shaped conductors, and the parallel-series circuit is connected to an LC parallel resonant circuit consisting of an inductance and a variable capacitor connected in parallel to each other;
It consists of this LC parallel resonant circuit and a capacitor connected in series.

[Effect]

In this invention, the resonant frequency of the LC parallel resonant circuit in the parallel series circuit is made to match the first resonant frequency of the three-dimensional circuit, and the composite impedance of the fixed capacitor and the parallel series circuit is made capacitive, and the three-dimensional circuit is connected to the second resonant frequency of the three-dimensional circuit. resonate at the resonant frequency of.

〔Example〕

FIG. 1 is a perspective view showing an embodiment of the present invention. In the figure, (11) is a pair of KH-shaped conductors similar to the conductor plate (1) in a conventional high-frequency coil for NMR. , are arranged to constitute a hollow cylindrical coil body. These conductors (11) have a non-protruding part (lxa) and a protruding part (11b). (2) and (3
) is exactly the same as that in a conventional high-frequency coil for NMR, and forms a three-dimensional circuit together with the conductor (11).

(4) is a protrusion (1) in parallel with each fixed capacitor (2).
1b) A parallel series circuit connected between an LC parallel resonant circuit consisting of an inductance (4a) and a variable capacitor (4b) connected in parallel to each other, and a capacitor ( 4C).

FIG. 2 is an equivalent circuit diagram of the embodiment shown in FIG.
b), the capacitance of the capacitor (4C) is C1,
C2, capacitance of fixed capacitor (2) and conductor ring (
Let C be the combined capacitance between 3a) or (3b) and the protrusion (1tb). Furthermore, the non-protruding part (11
Let the inductance value of a) be L/2. Then, the following (so that formula 11 is satisfied, C0, L I
Decide on C.

At this time, the high-frequency coil body circuit for KMR resonates at the first resonant frequency f1. In this case, since the LC parallel resonant circuit consisting of L, , and C1 is also resonating, its impedance becomes 100 KΩ or more, which is almost equivalent to not connecting the parallel-series circuit.

(The impedance 2 of the parallel-series circuit at 21ω2=2πf2 determines the values of Ll, C1, and C2. That is, they are made capacitive. Therefore, K.

If Cx is selected so as to satisfy the second resonant frequency f
2, the three-dimensional circuit of the high-frequency coil for NMR resonates.

As described above, according to the present invention, a high frequency coil for NMR that resonates at two frequencies, fl and f2, can be obtained.

Furthermore, as shown in the equivalent circuit diagram of FIG. 3, by providing two parallel-series circuits, a high-frequency coil for NMR that resonates at three frequencies can be obtained. In this case, CY should be selected so as to satisfy the resonance frequencies of the two parallel resonant circuits, respectively: fl, fl2. f3
A high frequency coil for NMR is obtained by using the following three frequencies.

To be more specific, when using fl, the parallel series circuits of Ll, C1, and C2 are connected to L31 for the reason mentioned above.
03. It should be a composite capacitor IC of the parallel series circuit of C4 and the capacitor C.

It is sufficient to use the combined capacitance C6 of the parallel series circuit of C1 and C2 and the capacitor C.

For example, static magnetic field strength 1. In the case of s T (Tesla), the resonance frequencies of proton, phosphorus, and sodium are each about 6
4 MHz, 25 M) (z, 17 MHl, so f = 64 MHz, f2 = 25 MHz, f3
= 17 MHz, it becomes a high frequency coil for NMR that can be applied to three types of nuclei.

In the above embodiment, a wide conductor plate was used as the non-protruding part of the conductor, but a plurality of narrow conductor plates, conductor pipes, or conductor wires such as copper wires may be arranged in the axial direction with a predetermined interval. The present invention can also be implemented in a high-frequency coil for NMR.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a three-dimensional circuit including at least one pair of conductors and a fixed capacitor that capacitively couples the protrusions of these conductors, and at least one parallel series circuit connected in parallel with each fixed capacitor. This parallel series circuit consists of an LC parallel resonant circuit consisting of an inductance and a variable capacitor connected in parallel with each other, and a capacitor connected in series to this LC parallel resonant circuit, so that it can be used at many frequencies. This has the effect of providing a resonant high frequency coil for NMR.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of the embodiment shown in FIG. 1, FIG. 3 is an equivalent circuit diagram of another embodiment, and FIG. 4 is an equivalent circuit diagram of the embodiment shown in FIG. FIG. 2 is a perspective view showing a conventional high-frequency coil for NMR. In the figure, (11) is a conductor, (ha) is a non-protruding part of the conductor, (11b) is a protruding part of the conductor, (2) is a fixed capacitor, (3) is a conductor ring, (4) is a parallel series circuit, (4a) is inductance, (4b) is variable capacitor, (4C)
is a capacitor. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Ko 2 diagram

Claims (4)

[Claims] (1) At least one pair of conductors arranged to form a hollow cylindrical coil body that is H-shaped; a fixed capacitor that capacitively couples the protrusions of these conductors; A three-dimensional circuit consisting of a conductor ring arranged concentrically with the conductor through an insulating layer and functioning equivalently as an LC series resonant circuit, and at least one parallel circuit connected between the protruding parts in parallel with each fixed capacitor. Equipped with a series circuit,
A high frequency coil for NMR characterized in that the parallel series circuit is composed of an LC parallel resonant circuit consisting of an inductance and a variable capacitor connected in parallel with each other, and a capacitor connected in series to the LC parallel resonant circuit. . (2) The resonant frequency of the LC parallel resonant circuit in the parallel series circuit is made to match the first resonant frequency of the three-dimensional circuit, and the three-dimensional circuit is made to have a composite impedance capacitance of a fixed capacitor and the parallel series circuit. The high-frequency coil for NMR according to claim 1, characterized in that the coil resonates at a resonant frequency. (3) Provide two parallel series circuits, and L in the first parallel series circuit.
The resonant frequency of the C parallel resonant circuit is matched with the first resonant frequency of the three-dimensional circuit, the resonant frequency of the LC parallel resonant circuit in the second parallel series circuit is matched with the second resonant frequency of the three-dimensional circuit, and 2. The high frequency coil for NMR according to claim 1, wherein the combined impedance of the fixed capacitor and the two parallel series circuits is made capacitive to cause the three-dimensional circuit to resonate at a third resonant frequency. (4) The conductor has a non-protruding part and a protruding part, and the non-protruding part is a single wide conductor plate or a plurality of narrow conductor plates arranged at a predetermined interval in the coil axis direction. A high-frequency coil for NMR according to any one of claims 1 to 3, characterized in that the coil is a conductor plate, a conductor pipe, or a conductor wire.