JPH03131235A - Transmission/reception equipment for magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To enable transmission and reception drives in magnetic resonance to be carried out effectively by interposing a 90 deg. phasing device between one channel of RF coil system and a synthesis device in a transmission/reception equipment of a magnetic resonance imaging apparatus. CONSTITUTION:A transmission/reception coil unit is equipped with a QD coil 10 including the first coil 10A and the second coil 10B, which are shifted by 90 deg. geometrically from each other. One terminal of the first resonator 12A is connected with a terminal of the first coil 10A of the QD coil 10, one terminal of the second resonator 12B with a terminal of the second coil 10B and the other terminal of the first resonator 12A with a terminal of a 90 deg. phase controller 24. The other terminal of the 90 deg. phase controller 24 and the other terminal of the second resonator 12B are connected with input terminal of a synthesizer 14, and a transmitter 18 and a receiver 20 are connected with the output terminal of the synthesizer 14 through a transmission/reception switching circuit 16. It is thus possible to carry out transmission or reception drives in magnetic resonance effectively.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to magnetic resonance (MR)
The present invention relates to a transmitting/receiving device for a magnetic resonance imaging apparatus that obtains morphological information such as a slice image of a subject (living body) and functional information such as spectroscopy using the phenomenon (sonance).

(Prior art) Magnetic resonance is a phenomenon in which an atomic nucleus with non-zero spin and magnetic moment placed in a static magnetic field resonantly absorbs and emits only electromagnetic waves of a specific frequency. The angular frequency ω shown in (ω.−2πν., ν.;
Larmor frequency).

ω0−γH0 Here, γ is the gyromagnetic ratio specific to the type of atomic nucleus,
Further, H is the static magnetic field strength.

This type of MR imaging device (MRI device), which performs biological diagnosis using the above-mentioned principle, processes electromagnetic waves of the same frequency as above that is induced after the above-mentioned resonance absorption, and
Nuclear density, longitudinal relaxation time T1. Transverse relaxation time T2. flow,
Diagnostic information that reflects information such as chemical shifts, such as slice images of a subject, is obtained non-invasively.

Collecting diagnostic information by magnetic resonance can excite all parts of a subject placed in a static magnetic field and collect signals, but there are limitations in the equipment configuration and clinical requirements for imaging images. Therefore, in an actual device, a specific part is excited and its signal is collected.

In this case, the specific region to be imaged is generally a sliced region with a certain thickness;
Magnetic resonance signals (MR multiplied signals) of echo signals and FID signals from this slice site are collected by performing a data encoding process many times, and these data groups are subjected to image reconstruction processing using, for example, a two-dimensional Fourier transform method. By doing so, an image of the specific slice region is generated.

In addition, this type of MHI device uses permanent magnets, superconducting magnets,
a static magnetic field generator using one or a combination of normally conducting magnets;
Gradient magnetic field generating coil and its power supply, transmitting (dedicated) coil, and receiving (dedicated) coil.

an RF coil unit including one or a combination of transmitting/receiving (combined) coils; a transmitter that generates a transmitting signal for excitation of a magnetic resonance phenomenon to be transmitted from the transmitting/receiving coil unit or the transmitting coil to the subject; A receiver that receives magnetic resonance signals induced in the specimen from the transmitting/receiving coil unit or the receiving coil, and a power supply for the gradient magnetic field generating coil, the transmitter, and the receiver are operated in a pulse sequence for signal collection, and the receiving signal is On the other hand, it is configured with a computer system that performs pixel reconstruction such as Fourier transform to generate images and handles necessary control and signal processing.

Note that the RF coil unit, transmitter, and receiver constitute a transmitting/receiving device.

Here, as shown in FIG. 13, the RF coil unit 1
Since the test object 22 is placed inside the RF coil unit 100, there is a stray capacitance C5, and its value varies depending on the test object 22 due to factors such as the size of the test object. This was a contributing factor to the change.

On the other hand, the RF coil unit 100 of this type of MHI device
As a receiver, there is a receiver having a first coil and a second coil, and the first coil and the second coil are arranged with a geometrical deviation of 90''. Some detectors perform quadrature detection using two detectors with a 90' phase shift.This detector uses quadrature phase detection (Q
D ; Quadruture Detection) method. The RF coil unit 100 in which the first coil and the second coil described above are arranged geometrically shifted by 900 degrees is called a QD coil, and there are several types of QD coils.

FIG. 14 is a configuration diagram of a conventional transmitting/receiving device, in which impedance fluctuations of a QD coil due to fluctuations in stray capacitance Cs can be compensated by a capacitance component of a resonator.

That is, the coil 10 constitutes a linear coil, to which a resonator 12 is connected, and a transmitter 18 . It is connected to the receiver 20. A human head, for example, is placed within the coil 10 as a subject 22 .

Here, the capacitance component of the resonator 12 is composed of a variable capacitance type tuning capacitor CT r and a variable capacitance type matching capacitor CM.

(Problem to be Solved by the Invention) In the above-mentioned compensation means, each time compensation is required, that is, each time the object to be examined changes, the two variables, which are the tuning capacitor C↑ and the matching capacitor CM in the example of FIG. It is necessary to adjust the capacitive capacitor. To perform this adjustment, it is necessary to add an impedance detector and a driving means (motor, etc.) for the variable capacitor, and also to use a switch to insert the additional system into the circuit shown in Figure 14. Not only that, but the adjustment work is complicated and time consuming, resulting in a decrease in testing efficiency and increased patient pain.

Although the above discussion is about coil impedance variation due to stray capacitance variation when the subject is changed, coil impedance variation may also occur in cases other than those described above. That is, coil 10
The resonant frequency of must match the frequency of the magnetic resonance signal to be received. In this case, the frequency of the magnetic resonance signal varies depending on the static magnetic field strength even for the same nuclide, and also varies depending on the type of the nuclide even for the same static magnetic field strength. Generally, it is a wide band of several megahertz to several tens of megahertz.

Therefore, when the static magnetic field strength or the nuclide to be imaged is changed, the above-mentioned compensation must be performed each time, and the same problem as mentioned above occurs. every 14th
In the example shown in the figure, it is necessary to adjust two variable capacitors, which are the tuning capacitor C7% and the matching capacitor CM. In order to perform this adjustment, it is necessary to add an impedance detector, a drive means (motor, etc.) for the variable capacitor, and a switch to insert the additional system into the circuit shown in Fig. 14. Moreover, the adjustment work is complicated and time-consuming, resulting in a decrease in testing efficiency and increased patient pain.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmitting/receiving device for a magnetic resonance imaging apparatus that can practically compensate for coil impedance fluctuations due to stray capacitance fluctuations for each subject without requiring adjustment work.

Another object of the present invention is that even if the static magnetic field strength and the nuclide to be imaged are changed, coil impedance fluctuations can be compensated for in practice without the need for adjustment after -degree adjustment. An object of the present invention is to provide a transmitting/receiving device for a magnetic resonance imaging apparatus.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following means are taken to solve the above problems and achieve the objects.

That is, the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 1 of the present invention has an RF coil having a first coil and a second coil that are geometrically shifted by 90'' and each including a resonance means. The RF coil system is characterized in that it has a combining means for combining the impedances of two channels of the RF coil system, and a 900 phase means is provided between one of the channels and the transmitter or the receiver.

A transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 2 of the present invention includes a transmitting coil unit having a first coil and a second coil arranged geometrically shifted by 900 degrees, and a capacitance component having a capacitance component. a first resonance means that sets a resonance condition at a predetermined frequency by an inductance component of the first coil and an inductance component of the second coil; a second resonant means for setting a resonance condition at a frequency; a first channel impedance due to the first coil and the first resonant means; and a second channel impedance due to the second coil and the second resonant means. a 90" phase means interposed between the first channel and the combining means; and a 90" phase means for generating a transmission signal for excitation of a magnetic resonance phenomenon; a transmitter for transmitting the transmitted signal to the subject via the first channel including the 900 phase means and the first channel; a receiving coil system including the resonance means; and a magnetic resonance signal induced from the subject. The present invention is characterized by comprising a receiver that receives the signal as a two-channel reception signal via the reception coil system.

A transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 3 of the present invention includes a transmitting coil system including a resonance means, and a transmitting coil system that generates a transmitting signal for excitation related to a magnetic resonance phenomenon and transmits the generated transmitting signal to the transmitting coil system. a transmitter transmitting to the subject via a first coil geometrically offset by 900 degrees.

a receiving coil unit having a second coil; a first resonance means having a capacitance component and setting a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the first coil; a second resonant means for setting a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the second coil;
combining means for combining the impedance of the first channel caused by the resonance means and the impedance of the second channel caused by the second coil and the second resonance means; 90'' phase means inserted between the two, and the magnetic resonance signal induced from the subject is passed through the first channel including the 90'' phase means, the second channel, and the combining means as a received signal. The present invention is characterized by comprising a receiver for receiving data.

A transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 4 of the present invention includes a transmitting/receiving coil unit having a first coil and a second coil arranged geometrically shifted by 90'', and a capacitance component having a capacitance component. first resonance means for setting a resonance condition at a predetermined frequency by a capacitance component and an inductance component of the first coil;
a second resonance means having a capacitance component and setting a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the second coil;
combining means for combining the impedance of a first channel caused by the coil and the first resonance means and the impedance of the second channel caused by the second coil and the second resonance means; and a 90'' phase means interposed between the first channel and the first channel, which generates a transmission signal for excitation of a magnetic resonance phenomenon, and transmits the generated transmission signal to the first channel including the 90'' phase means. a transmitter for transmitting a magnetic resonance signal induced from the subject to the subject through the combining means; the first channel including the 900 phase means; the second channel; a receiver for receiving two channels of received signals through the transmitter, and a transmitting/receiving switching means for selectively connecting the transmitter and the receiver to a first channel or a second channel including the 90'' phase means. It is characterized by having the following.

A transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 5 of the present invention includes a transmitting/receiving coil unit having a first coil and a second coil arranged geometrically shifted by 90'', and a capacitance component having a capacitance component. first resonance means for setting a resonance condition at a predetermined frequency by a capacitance component and an inductance component of the first coil;
a second resonance means having a capacitance component and setting a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the second coil;
The impedance of the first channel caused by the coil and the first resonance means and the impedance of the second channel caused by the second coil and the second resonance means are combined, and the phase of the impedance of the first channel is adjusted to 90°. a first means for shifting the impedance of the first channel, a second means for synthesizing the impedance of the first channel and the impedance of the second channel and shifting the phase of the impedance of the second channel by 900; The first means generates a transmission signal for such excitation and transmits the generated transmission signal.

a transmitter that transmits to the subject via the first channel; a receiver that receives the magnetic resonance signal induced from the subject as a two-channel reception signal via the second channel and second means; , the first means alternatively transmitting the transmitter and the receiver.

a first transmission/reception switching means connected to the first channel; and a first transmission/reception switching means that selectively switches between the transmitter and the receiver in conjunction with the first transmission/reception switching means. and a second transmission/reception switching means connected to the transmission/reception switching means.

A transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 6 of the present invention is such that the synthesizing means according to any one of claims 1, 2, and 3. It is characterized by having frequency characteristics corresponding to.

In the transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 7 of the present invention, the first means and the second means according to claim 5 correspond to the frequency characteristics of the received signal determined by the static magnetic field strength and the nuclide to be imaged. It is characterized by having a frequency characteristic of

(Function) According to the transmitting/receiving device for the magnetic resonance imaging apparatus according to claim 1 of the present invention, the 900 phase means is inserted between one channel of the RF coil system and the combining means. When looking at the first coil from the combining means through the 90' phase means, the reflected wave will have a phase shift of 90" on the outward path, and a phase shift of 90" on the return path. Therefore, due to both, the reflected wave returns with ta shifted by 180'. As a result, when the impedance of the one channel including the 900 phase means is combined with the impedance of the other channel, the combined value has a phase difference of 180' between the reflected waves, and the reflected waves cancel each other out. . In other words, there is no reflected wave. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the R
Impedance matching can be achieved across the two channels without adjusting the capacitance component of the F coil system resonance means. Therefore, transmission drive or reception drive in magnetic resonance can be effectively performed.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 2 of the present invention, by interposing the 900 phase means between the first channel of the transmitting coil unit and the combining means, the combining means When looking at the first coil through the 900 phase means, the reflected wave will have a phase shift of 900 degrees on the outward path, and a phase shift of 900 degrees on the return path. The reflected wave will return with its phase shifted by 180'. As a result, when the impedance of the first channel including the 90' phase means and the impedance of the second channel are combined, the combined value is 18 degrees between the reflected waves.

There is a phase difference, and the reflected waves cancel each other out. In other words, there is no reflected wave. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first. Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel. Therefore, transmission drive in magnetic resonance can be performed effectively.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 3 of the present invention, the 900 phase means is inserted between the first channel of the receiving coil unit and the combining means. When looking at the first coil from the combining means through the 900 phase means, the phase of the reflected wave will be shifted by 90'' on the outward path, and the phase will be shifted by 90'' on the return path. Therefore, due to both, the reflected wave returns with its phase shifted by 1806. As a result, when the impedance of the first channel including the 900 phase means and the impedance of the second channel are combined, the combined value has a phase difference of 180° between the reflected waves, and the reflected waves cancel each other out. match. In other words, there is no reflected wave. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first. Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel. Therefore, reception driving in magnetic resonance can be performed effectively.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 4 of the present invention, by interposing the 900 phase means between the first channel of the transmitting/receiving coil unit and the combining means, the combining means from said 900
When looking at the first coil through the phase means, the reflected wave will have a phase shift of 90'' on the outward path, and
Since the phase on the return path will be shifted by 90'', the reflected wave will return with its phase shifted by 1800. As a result, the impedance of the first channel including the 90' phase means will change. and the impedance of the second channel, the combined value is:
The reflected waves have a phase difference of 180', and the reflected waves cancel each other out. In other words, there is no reflected wave. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first. Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel. Therefore, transmission drive or reception drive in magnetic resonance can be effectively performed.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 5 of the present invention, the impedance of the first channel or the second channel during transmission or reception -G 9
0'' phase and can combine the impedances of the first channel and the second channel.Thereby, when looking at the first coil from the first means, the reflected wave is Since the phase will be shifted by 900 on the outward journey and the phase on the return journey will be shifted by 90'', the reflected wave will return with a phase shift of 180' due to both. Furthermore, when looking at the second coil from the second means, the reflected wave is:
Since the phase will be shifted by 900 degrees on the outward path, and the phase will be shifted by 900 degrees on the return path, the reflected wave will return with a phase shift of 180 degrees due to both. As a result, when the impedance of the first channel and the impedance of the second channel are combined, the combined value is 180% between the reflected waves.
There is a phase difference, and the reflected waves cancel each other out. In other words,
There will be no reflected waves. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first. Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel. Therefore, transmission drive or reception drive in magnetic resonance can be effectively performed.

According to the transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 6 of the present invention, the combining means according to claims 1, 2, 3, and 4 corresponds to the frequency characteristics of the received signal determined by the static magnetic field strength and the nuclide to be imaged. Therefore, even if the static magnetic field strength and the nuclide to be imaged are changed, by shifting the phase by 900 in a wide band, the output frequency will be 90'' on the outward trip and 90'' on the return trip, for a total of 180@ Due to the phase shift, the reflected waves cancel each other out, resulting in a state where there is no reflected wave, and matching is achieved. Therefore, once the coil impedance is adjusted by -degrees, the coil impedance fluctuation can be compensated for in practice without requiring any further adjustment work.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 7 of the present invention, the first means and the second means according to claim 5 adjust the frequency characteristics of the received signal determined by the static magnetic field strength and the nuclide to be imaged. Since they have corresponding frequency characteristics, even if the static magnetic field strength and the nuclide to be imaged are changed, by shifting the phase by 90'' in a wide band, the output will be 900 on the outward trip and 90 on the return trip.
, a total of 1000 phase shifts, the reflected waves cancel each other out, resulting in a state where there is no reflected wave, and matching is achieved.

Therefore, once adjusted, coil impedance fluctuations can be compensated for in practice without requiring any further adjustment work.

(Embodiment) A first embodiment of a transmitting/receiving device for a magnetic resonance imaging apparatus according to the present invention will be described below with reference to FIG. 1, in which the same parts as in FIG. 14, which is a conventional example, are given the same reference numerals. .

In this embodiment, the transmitter/receiver coil unit is a QD coil 10 having a first coil 10A and a second coil IOB which are geometrically shifted by 90''. SlottedTube Re5o
nator) coil 200, a cross elliptical coil (not shown), a saddle-shaped coil (not shown), a bird gauge coil, a Surf Ace QD coil, etc. can be used.

One terminal of the first resonator 12A is connected to the terminal of the first coil IOA of the QD coil 10, and the second coil IOB
One terminal of the second resonator 12B is connected to the terminal of the second resonator 12B. Further, one terminal of a 90'' phase shifter 24 is connected to the other terminal of the first resonator 12A.The other terminal of the 90'' phase shifter 24 and the other terminal of the second resonator 12B are connected to each other. It is connected to two input terminals of a combiner 14, and the combined output terminal of the combiner 14 is connected to a transmitter 18. It is connected to the receiver 20. In the QD coil 10, a human head, for example, is placed as the subject 22.

Here, the capacitance components of the first resonator 12A and the second resonator 12B each include a variable capacitance type tuning capacitor CT+a variable capacitance type matching capacitor CM.

The transmission/reception switching circuit 16 is capable of bidirectional switching using, for example, a PIN diode as a high frequency switching element, and is controlled to alternately set the transmission mode and reception mode at high speed by a pulse sequence controller (not shown). .

Furthermore, the system including the first coil IOA and the first resonator 12A is referred to as a first channel.

The system including the second coil IOB and the second resonator 12B is referred to as a second channel.

The above is the configuration of the transmitting/receiving device. In addition to these transmitting/receiving devices, the magnetic resonance imaging device also includes a static magnetic field generator (not shown), a gradient magnetic field generating coil (not shown) and its power source, and a power source and transmitter for the gradient magnetic field generating coil. vessel 18
The receiver 20 is operated in a pulse sequence for signal collection, and the received signal is subjected to image reconstruction such as Fourier transform to generate an image, and a computer system is provided to perform necessary control and signal processing. This computer system is equipped with a pulse sequence controller, which controls the transmission/reception switching circuit 16 and the transmitter 18 as described above.
and controls the receiver 20.

The transmitting/receiving device of the magnetic resonance imaging apparatus according to this embodiment configured as described above operates as follows.

That is, 1st. Tuning capacitor CT for second resonators 12A and 12B + matching capacitor C
It is assumed that M is adjusted when the QD coil 10 is installed or at an appropriate time. Here, the first coil 10A and the second coil IOB of the QD coil 10 are arranged symmetrically with respect to the subject, that is, the first coil 10A.

The distance between the subjects, the second coil 10B, and the distance between the subjects are the same, and the first coil 10A and the second coil IOB have the same structure, so each time the subject changes, The change in impedance in the first channel and the change in impedance in the second channel are approximately the same.

In this case, since the 900 phase shifter 24 has the function of shifting the phase by 90 degrees, the
When looking at the first channel through the 0″ phaser 24,
The reflected wave will have a phase shift of 90″ on the outward path,
Furthermore, since the phase on the return path will be shifted by 90'', the reflected wave will return with its phase shifted by 180° due to both.

In other words, the reflected waves cancel each other out because the reflected waves are out of phase by 180 degrees. In other words, there is no reflected wave.

In other words, it is matched to 50Ω.

Therefore, when a change in coil impedance occurs due to a change in stray capacitance for each subject 22, the first. Even if the capacitance components of the second resonators 12A and 12B are not adjusted, the first. Impedance matching will be achieved across the second channel. In this case, the transmission/reception switching circuit 16 is set alternately between the transmission mode and the reception mode in conjunction with the pulse sequence for image data collection, and when the transmission mode is set, the transmission signal from the transmitter 18 is transferred to the QD coil 10. A transmission signal (high frequency pulse) for excitation is applied to the subject 22. On the other hand, when the reception mode is set, the magnetic resonance signal received by the QD coil 10 is guided to the receiver 20. become.

As described above, according to this embodiment, when the QD coil 10 is installed or at an appropriate time, the first . Second resonator 12A, 1
By simply adjusting the 2B tuning capacitor CT + matching capacitor CM, the impedance detector and variable A predetermined impedance matching can be achieved without adding a capacitive capacitor driving means (such as a motor), a switching device, etc., and without requiring adjustment work. This improves inspection efficiency.

Next, a second embodiment of the present invention will be described with reference to FIG.

That is, the second embodiment shows an example of a detailed example of the first embodiment, in which the synthesizer 14 and the 90'' phase shifter 24 in the first embodiment are replaced with a high frequency impedance converter. 38 and 900 phase shifters 24.Here, the high frequency impedance converter 38 combines two systems each having an impedance of 50Ω and converts it into one system having an impedance of 50Ω.

The operation of the configuration of this second embodiment will be explained below.

That is, 1st. The tuning capacitors CT t and matching capacitors CM of the second resonators 12A and 12B are used to perform impedance matching adjustment of 50Ω using, for example, a standard human body equivalent phantom at the time of installing the QD coil 10 or at an appropriate time. It is assumed that this has been done. Here, the first coil IOA and the second coil 10B of the QD coil 10 are arranged symmetrically with respect to the subject, that is, the first coil 10A, the distance between the subject and the second coil 10B, the distance between the subjects is the same, and the first coil IOA and the second coil 10B have the same structure, so if the impedance in the first channel changes, the change will be This is approximately the same as the change in impedance in the second channel.

Here, a case will be described in which the test object 22 changes and the coil impedance changes due to the stray capacitance change for each test object 22.

In this case, if the impedance of the first channel at point 0 in the figure is ZA□, then ZAI-(50+ΔR)+jΔ I Similarly, if the impedance of the first channel at point ■ in the figure is ZA□, then ZA□ -(50+ΔR)+jAI Here, ΔR and 41 represent the real component and imaginary component of the deviation width of each impedance from 50Ω. Note that the real component ΔR is ΔR(50).

Also, if the impedance of the first channel at point 0 in the figure is ZAI, then ZA3■ZAI-(5,0+ΔR)+jΔ ■On the other hand, the reflected wave of the second channel at point 0 in the figure is 90
``There is a shift of 90' due to the phase shifter 24, and a shift of 90' again on the return trip, resulting in a total shift of 180°.

Therefore, the impedance ZB4 of the second channel at the zero point in the figure is as follows.

ZB4- (50+A R)-ja 1 This is ZAI
The relationship is complex conjugate.

Therefore, the combined impedance Z' of ZAI and ZB4 is as follows.

Z−−Z)3+Zsa −[(50+Δ R)+jΔ l] +[(50+Δ R) −jΔ 11 sets 100+2Δ
R This composite impedance Z is reduced to 1/2 by the high frequency impedance converter 38, so if it is set to 25, it becomes as follows.

z, -Z"/2 - (100+2ΔR)/2 -50+ΔR ← 50 Therefore, if the coil impedance changes due to the stray capacitance variation for each object 22, the imaginary component is canceled out and the real component is It can be seen that ΔR is unaffected by only changes (usually Δ 2).

). As a result, by simply adjusting the tuning capacitor CT + matching capacitor CM of the first and second resonators 12A and 12B, even if the coil impedance fluctuates due to the stray capacitance fluctuation for each test object 22, Even if this occurs, the impedance deviation is suppressed to such an extent that it does not pose a problem in practice. In other words, predetermined impedance matching can be achieved without adding an impedance detector, variable capacitor drive means (motor, etc.), switching device, etc., and without requiring adjustment work. .

Next, a third embodiment of the present invention will be described with reference to FIG.

That is, the third embodiment shows a specific example of the first embodiment, in which a transmitter/receiver switch 1 is provided between the first channel and the transmitter 18 and the receiver 20.
6A, 26B, 90" hybrids 26A, 26B, and resistors 28A, 28B, where the 90" hybrids 26A, 26B are the second
This is the same as that in the embodiment, and can have a 900 phase function and a 00 output synthesis function. Further, the resistance values of the resistors 28A and 28B are the same as the impedance of the QD coil 10 (for example, 50Ω).

According to this configuration, the impedance of the first channel or the second channel can be shifted in phase by 90'' during transmission or reception, and the impedance of the first channel and the second channel can be combined, and the impedance of the first channel or the second channel can be combined.
The same actions and effects as in the embodiment can be obtained.

A modification of the above-mentioned FIG. 4 is shown in FIG. In other words, the configuration shown in FIG. 5 is a balun (unbalanced/balanced conversion circuit) with an impedance of 50Ω for each channel in FIG.
29A and 29B are inserted, and the operation and characteristics are basically the same as those shown in FIG.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

That is, in the fourth embodiment, the QD coil 10 in the configuration of the first embodiment is used only for transmission, the transmission/reception switch 16 is removed, and the reception coil 30 and resonator 32 are replaced.
is added and connected to the receiver 20.

According to this configuration, the impedance of the first channel or the second channel can be phased by 906 when transmitting, and the impedance of the first channel and the second channel can be combined. The same actions and effects as in the embodiment can be obtained.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

That is, in the fifth embodiment, the QD coil 10 in the configuration of the first embodiment is used only for reception, the transmission/reception switch 16 is removed, and the transmission coil 34 and the resonator 34 are replaced.
is added and connected to the transmitter 18.

According to this configuration, the impedance of the first channel or the second channel can be phased by 900 during reception, and the impedance of the first channel and the second channel can be combined, and the impedance of the first channel or the second channel can be combined. The same actions and effects as in the embodiment can be obtained.

The examples shown in FIGS. 1 to 7 described above are configurations in which coil impedance fluctuations due to stray capacitance fluctuations for each test object can be compensated for without the need for adjustment even if the test object is replaced. The examples shown in Figures 8 to 12 below show that even when the static magnetic field strength and the nuclide to be imaged are changed, the phase can be changed to 9 in a wide band.
By shifting the phase by 0", the phase is shifted by 900" on the outward trip and 90" on the return trip, for a total of 180", so the reflected waves cancel each other out, resulting in a state where there is no reflected wave, and matching is achieved.Therefore, there is a This shows a configuration in which coil impedance fluctuations can be compensated for in practice without requiring any adjustment work once the frequency has been adjusted.

The sixth embodiment shown in FIG. 8 corresponds to the first embodiment shown in FIG. 1, and includes the 90'' phase shifter 24 in FIG. Instead, a broadband hybrid 114 having the functions of a synthesizer and a 90' phase shifter is used.In the first embodiment, the stray capacitance fluctuates each time the object is changed. However, in this example, the frequency of the magnetic resonance signal changes depending on the static magnetic field strength even for the same nuclide, and also varies depending on the type of nuclide even for the same static magnetic field strength. The circumstances are the same in that it is necessary to adjust the two variable capacitors, which are the tuning capacitor CT and the matching capacitor CM.The difference is that in this example, the frequency range is from several megahertz to several tens of megahertz. Therefore, in this example, instead of the 90'' phase shifter 24 and the synthesizer 14 with normal frequency band characteristics in FIG. A broadband hybrid 114 is used.

Similarly, the examples shown in FIGS. 9 to 12 will be explained below.

The seventh embodiment shown in FIG. 9 corresponds to the third embodiment shown in FIG. The configuration uses hybrid F126A and 126B.

The modification of the seventh embodiment shown in FIG. 10 corresponds to the modification of the third embodiment shown in FIG.
Broadband 906 hybrid 126 instead of 6A, 26B
The configuration uses A and 126B.

The eighth embodiment shown in FIG. 11 corresponds to the fourth embodiment shown in FIG. 6, and the 900 phase shifter 24 in FIG. Instead, a broadband hybrid 114 having both the functions of a synthesizer and a 90'' phase shifter is used.

The ninth embodiment shown in FIG. 12 corresponds to the fifth embodiment shown in FIG. Instead, a broadband hybrid 114 having both the functions of a synthesizer and a 90'' phase shifter is used.

The present invention is not limited to the above embodiments, but can be implemented with various modifications without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 1 of the present invention, a 900 phase means is inserted between one channel of the RF coil system and the combining means. As a result, the 900%
When looking at the first coil through the phase means, the reflected wave will have a phase shift of 90'' on the outward path, and
Since the phase on the return path will be shifted by 900, the reflected wave will return with a phase shift of 180". As a result, the impedance of the one channel including the 900 phase means and When combining the impedance of the other channel, the combined value is that the reflected waves have a phase difference of 180' and the reflected waves cancel each other out.In other words, there is no reflected wave.In other words, at 50Ω This means that they are matched.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the R
Impedance matching can be achieved throughout the two channels without adjusting the capacitance component of the resonance means of the coil system F. Therefore, transmission drive or reception drive in magnetic resonance can be effectively performed.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 2 of the present invention, by interposing the 900 phase means between the first channel of the transmitting coil unit and the combining means, the combining means When looking at the first coil through the 900 phase means, the reflected wave will have a phase shift of 900 on the outward path, and a 90'' phase shift on the return path, so both As a result, the reflected wave returns with its phase shifted by 180°.As a result, when the impedance of the first channel including the 900 phase means and the impedance of the second channel are combined, the resultant The value is that the reflected waves have a 180° phase difference and cancel each other out.In other words, there is no reflected wave.In other words, they are matched to 50Ω.Therefore, each subject If the coil impedance fluctuates due to the stray capacitance fluctuation in the first.
Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel.

Therefore, transmission drive in magnetic resonance can be performed effectively.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 3 of the present invention, by interposing the 90@ phase means between the first channel of the receiving coil unit and the combining means, the combining When looking at the first coil from the means through the 90' phase means, the reflected wave will have a phase shift of 90" on the outward path, and a phase shift of 9011 on the return path. , the reflected wave returns with its phase shifted by 180'.As a result, when the impedance of the first Q channel including the 900 phase means and the impedance of the second channel are combined, the The composite value is
There is a 180° phase difference between the reflected waves, and the reflected waves cancel each other out. In other words, there is no reflected wave. In other words, it is matched to 50Ω. Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first
．． Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel.

Therefore, reception driving in magnetic resonance can be performed effectively.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 4 of the present invention, by interposing the 900 phase means between the first channel of the transmitting/receiving coil unit and the combining means, the combining means From above 90@
When looking at the first coil through the phase means, the reflected wave will have a phase shift of 90'' on the outward path, and
Since the phase on the return path will be shifted by 900, the reflected wave will return with its phase shifted by 1800 due to both. As a result, when the impedance of the first channel including the 900 phase means and the impedance of the second channel are combined, the combined value is:
The reflected waves have a phase difference of 180@, and the reflected waves cancel each other out. In other words, there is no reflected wave. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first. Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel. Therefore, transmission drive or reception drive in magnetic resonance can be effectively performed.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 5 of the present invention, the impedance of the first channel or the second channel is set to 900 when transmitting or receiving.
The impedances of the first channel and the second channel can be combined. As a result, when looking at the first coil from the first means, the phase of the reflected wave will be shifted by 900 on the outward path, and the phase will be shifted by 90 @ on the return path. Due to both, the reflected wave has a phase of 18
0@ will be shifted back. Furthermore, when looking at the second coil from the second means, the reflected waves have a phase shift of 900 on the outward path, and a phase shift of 90@ on the return path, so both As a result, the reflected wave returns with its phase shifted by 180°. As a result, when the impedance of the first channel and the impedance of the second channel are combined, the combined value has a phase difference of 180@ between the reflected waves, and the reflected waves cancel each other out. In other words, there is no reflected wave. In other words, it is matched to 50Ω.

Therefore, if the coil impedance fluctuates due to the stray capacitance variation for each subject, the first. Even if the capacitance component of the second resonance means is not adjusted, the first. Impedance matching will be achieved across the second channel. Therefore, transmission drive or reception drive in magnetic resonance can be effectively performed.

According to the transmitting/receiving device for a magnetic resonance imaging apparatus according to claim 6 of the present invention, the combining means according to claims 1, 2, 3, and 4 corresponds to the frequency characteristics of the received signal determined by the static magnetic field strength and the nuclide to be imaged. Even if the static magnetic field strength or the nuclide to be imaged is changed, coil impedance fluctuations can be compensated for in practice without the need for further adjustment after -degree adjustment. can be done.

According to the transmitting/receiving device of the magnetic resonance imaging apparatus according to claim 7 of the present invention, the first means and the second means according to claim 5 adjust the frequency characteristics of the received signal determined by the static magnetic field strength and the nuclide to be imaged. Since they have corresponding frequency characteristics, even if the static magnetic field strength and the nuclide to be imaged are changed, the phase can be shifted by 900 over a wide band, resulting in a 90" on the outward trip and a 90" on the return trip.
, are out of phase by a total of 180 degrees, so that the reflected waves cancel each other out, resulting in a state where there is no reflected wave, and matching is achieved.

Therefore, once adjusted at a certain frequency, coil impedance fluctuations can be compensated for in practice without requiring any further adjustment work.

Therefore, according to the present invention, it is possible to provide a transmitting/receiving device for a magnetic resonance imaging apparatus that can compensate for variations in coil impedance due to variations in stray capacitance for each subject without requiring adjustment work.

Furthermore, according to the present invention, even when the static magnetic field strength and the nuclide to be imaged are changed, the phase can be adjusted to 90'' in a wide band.
By shifting the phase by 90'' on the outward path and 900'' on the return path, for a total of 180 @ phase, the reflected waves cancel each other out, resulting in a state where there is no reflected wave and matching is achieved.Therefore, - degree adjustment Then, it is possible to provide a transmitting/receiving device for a magnetic resonance imaging apparatus in which coil impedance fluctuations can be practically compensated for without requiring any subsequent adjustment work.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a first embodiment of a transmitting/receiving device for a magnetic resonance imaging apparatus according to the present invention. FIG. 2 is a perspective view of an STR coil as an example of a QD coil in the same embodiment. FIG. 4 is a diagram showing the configuration of a second embodiment of the transmitting/receiving device of the magnetic resonance imaging apparatus according to the present invention, and FIG. 5 is a diagram showing the configuration of a modification of the third embodiment shown in FIG. 4, and FIG. 6 is a diagram showing the configuration of a modification of the third embodiment shown in FIG. 4. FIG.
7 is a diagram showing the configuration of a fifth embodiment of the transmitting/receiving device of the magnetic resonance imaging apparatus according to the present invention, and FIG. 8 is a diagram showing the configuration of the transmitting/receiving device of the magnetic resonance imaging apparatus according to the present invention. A diagram showing the configuration of a sixth embodiment of the device,
FIG. 9 is a diagram showing the configuration of a seventh embodiment of the transmitting/receiving device of the magnetic resonance imaging apparatus according to the present invention, and FIG. 10 is a diagram showing the configuration of a modification of the seventh embodiment shown in FIG. 1st
FIG. 1 shows the configuration of an eighth embodiment of the transmitting and receiving device for a magnetic resonance imaging apparatus according to the present invention, and FIG. 12 shows the configuration of a ninth embodiment of the transmitting and receiving device for a magnetic resonance imaging apparatus according to the present invention. FIG. 13 is a diagram showing stray capacitance occurring between the QD coil and the subject,
FIG. 14 is a diagram showing the configuration of a transmitting/receiving device of a conventional magnetic resonance imaging apparatus. 10...QD coil, 10A...first coil, 1
0B...second coil, 12A...first resonator,
12B...Second resonator, 14...Synthesizer, 16.
...Transmission/reception switching device, 16A...Transmission/reception switching device, 16B...
・Transmission/reception switch, 18... transmitter, 20... receiver,
24...900 phase shifter, 26A...first 90'' hybrid, 26B...second 90'' hybrid, 28A...first resistor, 28B...second resistor,
29A, 29B... Balun, 30... Receiving coil,
32... Resonator, 34... Transmission coil, 36...
Resonator, 114... wideband 900 hybrid, 12
6A...first broadband 900 hybrid, 26B...
...Second wideband 90'' bibrid.

Claims (7)

[Claims] (1) RF having a first coil and a second coil arranged geometrically shifted by 90 degrees, each including a resonance means
It has a coil system, is provided with a synthesis means for synthesizing the impedances of two channels of the RF coil system, and is characterized in that a 90° phase means is provided between one of the channels and the transmitter or the receiver. Transmitter/receiver for magnetic resonance imaging equipment. (2) A transmitting coil unit having a first coil and a second coil arranged geometrically shifted by 90 degrees, and having a capacitance component, which is predetermined by the capacitance component and the inductance component of the first coil. a first resonance means that sets a resonance condition at a predetermined frequency; and a second resonance means that has a capacitance component and sets a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the second coil. and combining means for combining the impedance of the first channel due to the first coil and the first resonant means and the impedance of the second channel due to the second coil and the second resonant means; and a 90° phase means interposed between the channel of the 90° and the combining means, and a 90° phase means for generating a transmission signal for excitation related to a magnetic resonance phenomenon, and transmitting the generated transmission signal to the 90° phase means.
゜A transmitter that transmits to the subject via the first channel and the second channel including a phase means, a receiving coil system including a resonance means, and a receiving coil system that transmits a magnetic resonance signal induced from the subject. 1. A transmitting/receiving device for a magnetic resonance imaging apparatus, comprising: a receiver for receiving a received signal via a receiver. (3) a transmitting coil system including a resonance means, a transmitter that generates a transmitting signal for excitation related to a magnetic resonance phenomenon and transmitting the generated transmitting signal to the subject via the transmitting coil system; a first coil arranged 90° apart from each other;
a receiving coil unit having a second coil; a first resonance means having a capacitance component and setting a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the first coil; a second resonant means for setting a resonance condition at a predetermined frequency by the capacitance component and the inductance component of the second coil;
combining means for combining the impedance of the first channel caused by the resonance means and the impedance of the second channel caused by the second coil and the second resonance means, and between the first channel and the combining means. a 90° phase means inserted therein, and a magnetic resonance signal induced from the subject to the first channel including the 90° phase means;
A transmitting/receiving device for a magnetic resonance imaging apparatus, comprising: the second channel; and a receiver that receives a two-channel reception signal via the combining means. (4) a transmitting/receiving coil unit having a first coil and a second coil arranged geometrically shifted by 90 degrees;
a first resonance means that sets a resonance condition at a predetermined frequency by an inductance component of the second coil; a second resonant means for setting, a first channel impedance due to the first coil and the first resonant means, and a second channel impedance due to the second coil and the second resonant means. a synthetic means for
a 90° phase means interposed between the first channel and the combining means; and a 90° phase means for generating a transmission signal for excitation of a magnetic resonance phenomenon and transmitting the generated transmission signal to the 90° phase means. a first channel, said second channel, a transmitter for transmitting a magnetic resonance signal induced from the subject to the subject via said combining means; two channels, a receiver for receiving two channels of received signals via the combining means, and a second 90° phase means for selectively phasing the transmitter and the receiver; or a transmission/reception switching device connected to the second channel. (5) a transmitting/receiving coil unit having a first coil and a second coil arranged geometrically shifted by 90 degrees;
a first resonance means that sets a resonance condition at a predetermined frequency by an inductance component of the second coil; a second resonant means for setting, a first channel impedance due to the first coil and the first resonant means, and a second channel impedance due to the second coil and the second resonant means. and a first means for shifting the phase of the impedance of the first channel by 90 degrees; 9
a second means for shifting by 0°; a second means for generating a transmission signal for excitation related to a magnetic resonance phenomenon; and transmitting the generated transmission signal to the first
means, a transmitter that transmits to the subject via the first channel, a second channel, and a transmitter that receives the magnetic resonance signal induced from the subject as a two-channel reception signal via the second means. a receiver; a first transmission/reception switching means for selectively connecting the transmitter and the receiver to the first means and the first channel; A transmitting/receiving device for a magnetic resonance imaging apparatus, comprising second transmitting/receiving switching means for selectively connecting the transmitter and the receiver to the second means and the second channel. (6) Claims 1 and 2 characterized in that the combining means has a frequency characteristic corresponding to a frequency characteristic of the received signal determined by the static magnetic field strength and the nuclide to be imaged.
, 3, 4, or 5. A transmitting/receiving device for a magnetic resonance imaging apparatus according to any one of . (7) The magnetic field according to claim 6, wherein the first means and the second means have frequency characteristics corresponding to the frequency characteristics of the received signal determined by the static magnetic field strength and the nuclide to be imaged. Transmitter/receiver for resonance imaging equipment.