JPH0471534A - Magnetic resonance image device - Google Patents

Abstract

PURPOSE:To obtain a small magnetic resonance image device and solve problems such as the usage in the high magnetic field, stray capacity and size by constituting a 90 deg.-distributing/synthesizing unit with two pairs of impedance transformers, adjacently arranging transformers with different characteristic impedances, and connecting the transformers with different characteristic impedances together. CONSTITUTION:GND portions of four 1/4-wavelength impedance transformers 1, 2, 3, 4 are bundled, for example, they are soldered at a proximity layout with the minimum volume, two of the transformers 1-4 with different characteristic impedances are adjacently arranged, and the transformers with the same characteristic impedance are diagonally arranged. The adjacent transformers with different characteristic impedances are connected together. The transformers 1, 4 and 2, 3 are vertically connected in parallel on one side, and the transformers 1, 2 and 3, 4 are horizontally connected in parallel on the other side. This device can be used in the high magnetic field environment, it has no effect from the stray capacity of a casing, and it can be miniaturized and made lightweight as compared with conventional probes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application)] The present invention relates to a magnetic resonance imaging apparatus having a probe equipped with a 90° distributor/synthesizer.

(Prior Art) FIG. 4 is a conceptual diagram when using a QD probe in MHI. 1 is a QD type probe, and 2 is a 90° distributor/synthesizer (hybrid type) that distributes and combines RF power when transmitting and receiving to the QD type probe. Herein, QD type probes and 9
The 0'' distributor and combiner are collectively referred to as probes.

3 is an object to be measured placed inside a QD type probe. These operations will be explained below. During transmission, RF power is efficiently irradiated to the object under test 3, and during reception, N
As a method of receiving MR signals with a high S/N, it is often used to make the probe QD. This is capable of improving the efficiency of the transmitting/receiving device by transmitting and receiving circularly polarized waves to and from the object to be measured 3 within the QD type probe 1. At this time, as one of the elements constituting the QD type probe 1, the transmitted RF power is divided into two with a 3 dB lower power with a 90'' phase difference and sent to the QD type probe 1, and the 90'' position from the QD type probe 1 is divided into two. There is a 90° distribution/synthesizer 2 that combines received signals with phase differences.

FIGS. 5(a) and 5(b) are circuit configuration diagrams illustrating types of 90° distributor/synthesizer. FIG. 5(a) shows the combinations A and B of inductance and capacitance.

Each of the two terminals C and D is of a type in which one terminal is commonly connected to GND, and the other terminal is used as a connection terminal to a measuring device. Further, FIG. 5(b) shows a type in which a quarter-wavelength impedance transformer with a characteristic impedance Zo and a quarter-wavelength impedance transformer with a characteristic impedance Zo/J2 are combined. In addition, there is also a type that uses a transmission line transformer, which is similar in principle to the type that combines inductance and capacitance shown in FIG. 5(a).

When this is used in a magnetic resonance imaging apparatus (MHI), the magnetic flux generated in the core becomes saturated due to the high magnetic field environment, resulting in deterioration of the characteristics as a 90° distributor/synthesizer.

In the case of the type shown in Figure 5 (a) that uses only inductance and capacitance, in practice it is necessary to provide a casing to suppress fluctuations in frequency characteristics due to fluctuations in stray capacitance that occur in the inductance section, so stray capacitance must be taken into account. Additional adjustments will also be required. It is also necessary to consider the structural pressure resistance between the component parts and the case, the pressure resistance of the component parts themselves, and the like.

Furthermore, the one shown in FIG. 5(b) is a type constructed from a microstrip line using two types of characteristic impedances Z and /J2 by applying four quarter-wavelength impedance transformers. Generally, this is often used when the frequency to be handled is in the microwave band (UHF or higher). The reason for this is that the wavelength is short, so it can be constructed as short as four 1/4 wavelength impedance transformers of two types made of microstrip lines, and the circuit configuration of the 90° distributor/synthesizer itself can also be made smaller. . However, short wave band (HF) such as MRI
・In the very high frequency band (VHF), the wavelength spans several meters, so the four impedance transformers that make up the 90° splitter/synthesizer are arranged on each side of a square. If you use a device that connects , the distributor/synthesizer itself becomes a square box with a thickness of several meters on each side, which is not practical as it reduces the efficiency of work and transportation.

(Problems to be Solved by the Invention) As stated above, conventionally, the frequency band used in magnetic resonance imaging equipment is mainly a shortwave band, and the wavelength ranges over several meters, so a 90" splitter/synthesizer has been used. A probe equipped with this had the disadvantage of being large.

Therefore, the present invention has been made in view of the above points, and is composed of four impedance transformers that solve problems such as use under high magnetic fields, stray capacitance and withstand voltage due to construction, and size due to structure. The object of the present invention is to provide a magnetic resonance imaging apparatus equipped with a 90'' distributor/synthesizer.

[Configuration of the Invention (Means for Solving the Problems) In order to achieve the above object, the present invention includes a method of bringing a probe into contact with an object to be measured and measuring image data obtained from the object with the probe. , is a magnetic resonance imaging apparatus that inputs the measurement results from this probe section into a 90° distributor/synthesizer operating at a predetermined wavelength and analyzes the output results. Each impedance transformer is arranged close to a position where the longitudinal direction of each impedance transformer is parallel to each other so that each of the adjacent impedance transformers has different characteristic impedance characteristics, and This is characterized by connecting impedance transformers with different impedances.

(Function) The 90° distributor/synthesizer that makes up the probe consists of two sets of impedance transformers.

In the 90° distributor/synthesizer of the present invention, these two sets of impedance transformers are arranged close to each other so that the longitudinal directions of the impedance transformers are parallel to each other so that adjacent sets of impedance transformers have different characteristic impedances. Miniaturization can be achieved by connecting impedance transformers with different impedances.

(Example) An example of the present invention will be described with reference to the drawings. Here, a case will be described in which the 1/4 wavelength impedance transformer is configured with a semi-rigid cable. FIG. 1 is a structural diagram of an embodiment of a 90'' distributor/combiner (hybrid) constructed of four quarter-wavelength impedance transformers related to the present invention.
The structure of the distributor/synthesizer (hybrid) will be explained.

In this figure, as an example, the GND parts of four quarter-wavelength impedance transformers 1, 2, and 3.4 are bundled and soldered close together to minimize the volume. The connection between the /4 wavelength impedance transformers will be described later.

FIGS. 2(a), 2(b), and 2(c) are configuration diagrams illustrating the internal structure of an embodiment of the present invention. Figure 2 (a
) is a cross-sectional view of the 90'' distributor/synthesizer, Figure 2(b) is a cross-sectional view seen from the left side of Figure 2(a), and Figure 2(C) is a cross-sectional view of the 90'' distributor/synthesizer.
is a sectional view seen from the right side of FIG. 2(a). Figure 2 (
With reference to b), the case will be explained focusing on the semi-rigid cable 1 having a characteristic impedance Z0. The arrangement of the four quarter-wave impedance transformers 1, 2, 3, and 4 is such that adjacent ones have different characteristic impedances. For example, the quarter-wave impedance transformers 1 next to each other having a characteristic impedance Zo have different characteristic impedances. Impedance Z.

/J2 1/4 wavelength impedance transformers 2 and 4. Diagonally adjacent ones have the same characteristic impedance, for example, 1/4 of the characteristic impedance Zo/
Diagonally adjacent to the wavelength impedance transformer 1 is a quarter wavelength impedance transformer 3 having a characteristic impedance Zo/.

To connect the lines, adjacent lines having different characteristic impedances are connected as shown in FIGS. 2(b) and 2(c). That is, as shown in FIG. 2b, one side connects vertically in parallel, specifically, 1, 4, 2, and 3.

Moreover, as shown in FIG. 2(C), the other side is connected horizontally in parallel, specifically, 1, 2, 3, and 4.

The operation of the 90° distributor/synthesizer (hybrid) will be explained using the operation explanatory diagram showing details of an embodiment of the present invention shown in FIG. If the configuration in the same figure corresponds to that in Figure 1,
Between the terminals A and B shown in Fig. 3, the impedance transformer 1 shown in Fig. 1 is used, and between the terminals B and C shown in Fig. 3, the impedance transformer 2 shown in Fig. 1 is used. Terminals C, D
1 corresponds to the impedance transformer 3 in FIG. 1, and corresponds to the impedance transformer 4 in FIG. The power of the signal input from A or D is divided into two between B and C, and the signal is output at a value 3 [dB] lower than the input level. At this time B
The phase difference between the signals divided into two and outputted is 90°. However, since no signal passes between AD and BC (isolation is achieved), there is no interference, and for example, power input from A (B) cannot be directly transmitted to D (C). None. Although this case has been explained using a semi-rigid cable as an example, the present invention is not limited to this embodiment.

[Effects of the Invention] As described in detail above, the probe included in the magnetic resonance imaging apparatus of the present invention is configured with four impedance transformers and can be used in a high magnetic field environment compared to a conventional probe equipped with a 90" distributor/synthesizer. However, it can also be used in smaller sizes and lighter weight without being affected by stray capacitance caused by the casing.

[Brief explanation of drawings]

1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing an internal structure of the present invention, FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. 4 is a diagram showing another embodiment of the present invention. The figure shows a conventional example, and FIG. 5 is a diagram showing the circuit configuration of a conventional 90° distributor/synthesizer. 1.3...174 wavelength impedance transformer with characteristic impedance ZO, 2,4...characteristic impedance Z
o/J 2 quarter wavelength impedance transformer.

Claims (1)

[Claims] A probe is brought into contact with an object to be measured, and the image data obtained from the object is measured by the probe, and the measurement results from this probe are transferred to a 90° distribution device that operates at a predetermined wavelength.
In a magnetic resonance imaging apparatus that inputs input to a synthesizer and analyzes the output results, the 90° distribution synthesizer is composed of two sets of impedance transformers, and each adjacent impedance synthesizer has a different characteristic impedance characteristic. 1. A magnetic resonance imaging apparatus characterized in that impedance transformers having different impedance characteristics are connected to each other, and the impedance transformers are arranged close to each other at positions where the longitudinal directions of the impedance transformers are parallel to each other.