JPH02309265A - High frequency tester of magnetic resonance measuring apparatus - Google Patents

Abstract

PURPOSE:To simplify the judgement of an automatic tuning circuit by receiving the simulation high frequency circuit substituting the high frequency coil of a magnetic resonance measuring apparatus in a housing and measuring the tuning control signal from the automatic tuning circuit in such a state that said signal is applied to said circuit. CONSTITUTION:The simulation high frequency circuit substituting the high frequency coil of a magnetic resonance measuring apparatus is received in a small-sized housing 10 and the cable of the output terminal of an automatic tuning circuit 20 is connected to the input/output connector of the housing 10 and the measuring terminals 7, 8 of the simulation high frequency circuit are connected to the measuring terminals 18, 19 of a DC voltage measuring device V. By this method, varicap control voltage can be measured under the same condition as when the high frequency coil would be actually connected.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention applies an RF multiplied signal to a subject placed in a static magnetic field to excite nuclear spins, receives an NMR signal from the subject, In a magnetic resonance measurement device (hereinafter referred to as MHI device) that obtains information about the subject by processing this received signal, the high-frequency coil installed to transmit and receive RF multiplied signals with the subject is automatically tuned. The present invention relates to a high frequency test device that tests the operation of a controlled autotuning circuit.

<Conventional technology> An MRI apparatus places a subject in a static magnetic field and applies RF pulses while applying a gradient magnetic field to selectively excite nuclear spins in the target area (slice plane). NMR
This is a device that receives signals and converts the difference in signal intensity into an image as gray scale information.

As is well known, the transmission of the RF pulse and the reception of the NMR signal are performed through a high-frequency coil placed around the subject.

By the way, the above-mentioned high-frequency coil is tuned to an RF frequency determined according to the strength of the static magnetic field and the type of object placed in the coil (for example, lH>) in order to improve reception efficiency. Generally, a tuning circuit consisting of a coil, a capacitor, a resistor, etc. is incorporated into the device.

This tuning operation can be electrically automated, reducing the time required for magnetic resonance imaging operations.
This automated tuning method (auto-tuning method) is widely adopted.

The applicant has already filed a patent application for a tuning circuit using resistors, varicaps, etc. to realize the above auto-tuning method (Japanese Patent Application No. 12/1986).
No. 4512]. According to this, the capacitance of the varicap can be changed simply by changing the voltage supplied from the auto-tuning circuit, and tuning can be automatically achieved.

<Problem to be solved by the invention> However, in order to operate the MHI device, it is necessary to always check whether the drive signal of the auto-tuning circuit is normal, that is, whether the high-frequency coil is tuned to the desired frequency. It is necessary. When attempting to check the operation of the auto-tuning circuit, it is usually undesirable to remove the auto-tuning circuit from the MHI device and measure it because it is complicated and generally requires a special measuring device. This is especially true when the MHI device is installed in a predetermined location and is in practical operation.

Therefore, it is conceivable to actually drive the auto-tuning circuit and test it while performing auto-tuning, but this work using an actual high-frequency coil is difficult because the high-frequency coil is relatively large and easily affected by the surrounding environment. Also, since the measurement target (human body or phantom) has a large influence, the conditions at the time of measurement are not always constant, and large errors often occur, making it impossible to accurately evaluate the autotuning circuit.

The present invention has been made in view of the above problems, and
The purpose is to provide a high-frequency test device that can easily determine whether the auto-tuning circuit is operating properly or not, even though the auto-tuning circuit is still installed.

Means for Solving the Problems> The high frequency test device of the present invention to achieve the above object houses a simulated high frequency circuit used as a substitute for the high frequency coil in a housing, and also has a The casing is provided with a measurement terminal for measuring the tuning control signal while applying it to the simulated high-frequency circuit, or a measuring device for measuring the tuning control signal.

<Function> With the high-frequency test equipment described above, a simulated high-frequency circuit is used as a substitute for the high-frequency coil, and the auto-tuning circuit is measured with the simulated high-frequency circuit connected to the load of the auto-tuning circuit. Circuits can be tested under conditions close to the actual environment,
Accurate evaluation of autotuning circuits can be performed.

<Example> Embodiments will be described in detail below with reference to the accompanying drawings showing examples.

FIG. 2 shows a circuit configuration diagram of a simulated high frequency circuit.

The simulated high frequency circuit includes a coil 1 and a tuning capacitor 3 that is combined with the coil 1 at a predetermined frequency to create a resonant circuit.
Matching capacitors 4a, 4b for impedance matching between the varicap 2 and the transmission cable connected to the input/output connector 6, and a capacitor for supplying DC voltage to drive the varicap 2. It consists of a pair of resistors 5a and 5b and measurement terminals 7 and 8.

Coil 1. is made relatively small, and M
In an RI apparatus, this corresponds to a high frequency coil placed around a subject.

The varicap 2 is for making the tuning frequency of the coil 1 variable, and the resistor 5 is for preventing high frequency leakage.
The capacitance value is controlled by the DC voltage applied from the input/output connector 6 via a and 5b.

The capacitors 4a and 4b are for impedance matching between the coil 1 and the transmission cable in order to optimize the RF signal transmission efficiency.

The capacitors 3a and 3b prevent DC voltage from being applied to anything other than the varicap 2, and the capacitors 3a and 3b prevent the application of DC voltage to anything other than the varicap 2.
Together with this, it forms part of a resonant circuit. □ The measurement terminal 7.8 is a terminal for externally measuring the DC voltage value that controls the varicap 2.
is the positive side, and the measurement terminal 8 is the ground side.

At the frequency used here, the resistors 5a and 5b are considered to have substantially infinite impedance, and the tuning frequency as a simulated high-frequency circuit is equal to the inductance of the coil 1.
Varicap 2, capacitor 3g, 3bs capacitor 4
It is determined by the capacitance of a and 4b.

The tuning frequency changes as the capacitance of the varicap 2 changes depending on the DC voltage supplied from the transmission cable.

FIG. 1 is a plan view showing a high frequency test device in which the above-mentioned simulated high frequency circuit is housed in a small housing.

The casing (lO) is a small case made of resin or metal that houses component parts, and the lid of the casing is removed. However, when using it, keep it closed with a lid on.

The coil 1 is wound around a resin bobbin 11 in a solenoid shape, for example. However, it is not limited to this, and may have a shape other than a solenoid. The size of the bobbin 11 and the number of turns of the coil are determined based on the inductance determined from the tuning frequency and convenience of handling. For example, it can have a diameter of about 20 mm and a length of about 501 TII11.

12 is a varicap 2 and a capacitor 3a.

3b, capacitor 4 a * 4 b s resistor 5a, 5
This is a board on which b is appropriately arranged.

The input/output connector 6 usually uses a BNC connector, but
Other coaxial connectors such as N type may also be used.

The l811J constant terminals 7 and 8 are terminals for easily measuring DC voltage, and the measurement terminal 7 on the positive side is the center conductor of the human output connector 6, and the measurement terminal 8 on the ground side is the outer conductor of the human output connector 6. cable 16, respectively.
．． 17.

The structure of the measurement terminals 7 and 8 is not particularly limited.

An outline of an autotuning module whose characteristics are to be tested using the above-mentioned high frequency test device will be explained. FIG. 3 is a block diagram illustrating the RF transmitter/receiver 23, the high frequency coil 21, the branch section 22 and the voltage source 24 that constitute the autotuning module 20, which are included in the MHI device.

The high frequency coil 21 is tuned to a predetermined RF frequency in order to improve reception efficiency, and a tuning circuit (not shown) identical to that shown in FIG. 2 above is incorporated in order to achieve this tuning. ing. However, it is not a necessary condition that they be the same, but only that the circuits may be the same or similar due to frequency constraints or the like.

The RF transmitter/receiver 23 feeds the RF multiplied signal to the high frequency coil 21 of the MRI apparatus and receives the RF multiplied signal from the high frequency coil 21, and the voltage [24] is a varicap control voltage signal to the high frequency coil 21. It is intended to supply

The branch section 22 is interposed between the RF transmitter/receiver 23 and the high frequency coil 21, and superimposes the varicap control voltage signal from the voltage source 24 onto the transmission cable. Branch part 22
The specific configuration of the high frequency coil 2 is as shown in FIG.
1. It has terminals 31, 32 and 33 which are respectively connected to the RF transceiver 23 and the voltage source 24, the terminals 31 and 32 are connected by a capacitor 34, and the terminals 31 and 33 are connected by a resistor 3.
5 are connected. Resistor 35 is a high resistance element and blocks RF frequencies. Therefore, although it can freely pass between the RF multiplier signal terminals 31 and 32, it does not leak to the terminal 33 because of the resistor 35. On the other hand, the DC voltage applied through the terminal 33 is applied to the high frequency coil 21 through the terminal 31, but is not applied to the terminal 32 because the capacitor 34 is present therein.

When testing the auto-tuning module using the high-frequency test device, a cable is connected from the output terminal of the auto-tuning module 20 to the input/output connector 6 of the high-frequency test device, as shown in FIG. Then, connect measurement terminal 1 of the DC voltage measuring device to measurement terminal 7°8.
8.19 and read the voltage value.

Thereby, the varicap control voltage superimposed on the output cable of the branch section 22 can be measured with the simulated high frequency circuit connected. As shown in FIG. 2, the simulated high-frequency circuit has a circuit configuration that simulates the high-frequency coil 21 of the MHI device, so it is possible to measure voltage under the same conditions as when the high-frequency coil is actually connected. .

Thereby, it is possible to accurately determine whether the auto-tuning module is operating with appropriate characteristics.

In addition, in the above-mentioned high frequency test apparatus, it is also possible to incorporate a DC voltage measuring device instead of or together with the 7111 constant terminals 7 and 8.

FIG. 6 shows another embodiment of the circuit configuration of the high frequency test device. The basic operation is the same as that described in FIG. 2, but capacitors 21a and 21b are added to lower the equivalent inductance of the coil 1 in order to increase the operating frequency. When using a high frequency test device having the circuit configuration shown in FIG. 6, the configuration of the high frequency coil of the MRI apparatus may be basically the same as or similar to the circuit shown in FIG.

FIG. 7 shows yet another example of circuit configuration. In comparison to the circuit of FIG. 6, capacitor set 2.3a.

3b is replaced with a single capacitor 46, and conversely, capacitors 21a and 21b are replaced with varicaps 40 and 41, respectively.
A set of capacitors including 40, 42° 43 and 41.4
4.45, and the capacity is made variable.

The resistance for supplying voltage to the varicap 4o is 47.
48, and the resistance for supplying voltage to the varicap 41 is 49.50. When using a high frequency test device having the circuit configuration shown in FIG. 7, the configuration of the high frequency coil of the MR1 device may also be basically the same as or similar to the circuit shown in FIG.

Note that the present invention is not limited to the above-described embodiments, and for example, the circuits of the high-frequency coil and the simulated high-frequency circuit are not limited to those shown in FIGS. 2, 6, and 7, and the auto-tuning module Any other circuit may be used as long as the tuning frequency can be varied by a control signal from the circuit.

Moreover, what is described as a fixed capacitance capacitor in FIGS. 2, 6, and 7 can be made adjustable by using a trimmer capacitor if necessary.

Furthermore, resistors 5a, 5b, 47 used for cutting off the RF multiplied signal.
, 48, 49, and 50 may be replaced with coils, or a coil and a capacitor may be connected in parallel to form a parallel resonant circuit. Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, according to the high frequency test device of the present invention, a simulated high frequency circuit used as a substitute for a high frequency coil is used,
Since the auto-tuning circuit can be measured with the simulated high-frequency circuit connected as a load to the auto-tuning circuit, the auto-tuning circuit can be tested under conditions close to the actual environment. Therefore, the state of the auto-tuning circuit can be grasped at any time, maintenance is facilitated, and the auto-tuning circuit can always be operated under constant conditions. As a result, it becomes possible to maintain the performance of the MHI device at its best.

[Brief explanation of drawings]

Figure 1 is a plan view showing a state in which a simulated high-frequency circuit is housed in the housing and measurement terminals are attached, Figure 2 is a circuit diagram of the simulated high-frequency circuit, and Figure 3 is an MHI
A block diagram showing the auto-tuning circuit etc. installed in the device, Fig. 4 is a circuit configuration diagram of a branch section, Fig. 5 is a diagram showing a state in which the auto-tuning circuit is tested using a high frequency test device, Fig. 6, FIG. 7 is a circuit configuration diagram showing another embodiment of the simulated high frequency circuit. 7.8...1IIJ constant terminal, 10... Housing, 20... Auto tuning circuit, 21... High frequency coil

Claims (1)

[Claims] 1. High frequency for testing the operation of an auto-tuning circuit that automatically controls the tuning of a high-frequency coil included in a magnetic resonance measurement device that uses nuclear magnetic resonance phenomena to obtain information from a subject. A test device, wherein a simulated high-frequency circuit used as a substitute for the high-frequency coil is housed in a housing, and a tuning control signal given from the auto-tuning circuit is applied to the simulated high-frequency circuit to perform the tuning control. 1. A high-frequency test device for a magnetic resonance measuring device, characterized in that a measurement terminal for measuring the tuning control signal or a measuring device for measuring the tuning control signal is provided in the housing.