JPH0515511A - Orthogonal receiving type receiving coil and magnetic resonance imaging apparatus using the same - Google Patents

Abstract

PURPOSE:To enable the executing of orthogonal adjustment properly by arranging two systems of coils with receiving sensitivity directions thereof orthogonal to each other to making an orthogonal axis thereof adjustable electrically in an orthogonal receiving type receiving coil used as such in a receiving system of a magnetic resonance imaging apparatus. CONSTITUTION:Three or more of conductor loops L1, L2 and L3 acting as respective resonance systems different in the receiving sensitivity direction from one another are used and combined to form two systems of coils 11 and 14 having one or two of the conductor loops. The resonance frequency of the individual conductor loops of the respective systems is adjusted to allow a adjustment so that the receiving sensitivity directions of the two systems of the coils 11 and 14 are orthogonal to each other. Thus, the electric adjustment of the orthogonal axis of the two systems of the coils 11 and 14 facilitates orthogonal adjustment properly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrature reception system in which two systems of coils are arranged such that their receiving sensitivity directions are orthogonal to each other, and the orthogonal axes can be electrically adjusted to appropriately perform orthogonal adjustment. The present invention relates to a coil and a magnetic resonance imaging apparatus using the receiving coil as a receiving coil in a receiving system.

[0002]

2. Description of the Related Art A magnetic resonance imaging apparatus utilizes a nuclear magnetic resonance (hereinafter abbreviated as "NMR") phenomenon to obtain a density distribution of nuclear spins at a desired inspection site in a subject,
The relaxation time distribution is measured, and the cross section of the subject is displayed as an image from the measured data. In this case, the nuclear spins of the subject placed in the uniform and strong static magnetic field generator perform precession about the direction of the static magnetic field at a frequency (Larmor frequency) determined by the strength of the static magnetic field. Therefore, when a high-frequency pulse having a frequency equal to this Larmor frequency is externally applied, spins are excited and transition to a high energy state (NMR phenomenon). When this irradiation is stopped, the spin returns to the original low energy state with a time constant corresponding to each state, and at this time, an electromagnetic wave is emitted to the outside. This is detected by the high frequency receiving coil tuned to the frequency. At this time, a triaxial gradient magnetic field is applied to the static magnetic field space in order to add position information to the space. As a result, it is possible to capture position information in space as frequency information.

As a means for improving the sensitivity of the above receiving coil, there is a receiving coil of a quadrature receiving system which improves the S / N ratio by arranging two coils in an orthogonal state and using them at the same time. This quadrature receiver coil
Of Magnetic Resonance 53-324-327,1983
Year ”(JOURNAL OF MAGNETIC RESONANCE 53-324-327,198
As described in 3), paying attention to the fact that the nuclear spins rotate on a plane, two receiving coils arranged in an orthogonal state perform independent signal reception, and the respective output positions are After the phase difference is corrected by the phase corrector and then combined by the adder, the signal is doubled compared to the case of only one receiving coil, and the noise is random noise, so it becomes √2 times on average. As a result, about 40% S / N
The ratio can be improved.

In order to improve the S / N ratio in the quadrature reception system as described above, it is important that the two coils can receive independently, and if the quadrature state collapses, not only the improvement amount decreases but also the same. Since it is tuned to the frequency, strong inductive coupling occurs and the S / N ratio deteriorates significantly. This state will be described with reference to the drawings. As shown in FIG. 9, the first coil 1 including the conductor loop L ₁ and the resonance capacitance C, the other conductor loop L ₂ and the resonance capacitance C are included. The second coil 2 is arranged so that the receiving sensitivity directions thereof are orthogonal to each other, and is tuned to the same frequency. The resonance characteristic of the receiving coil 3 formed by combining the coils 1 and 2 at this time can be known from the impedance Z seen from the output terminal 4. That is, as shown in FIG. 11A, the two coils 1 and 2 are in an orthogonal state, and for example, the first coil 1
When the magnetic flux φ ₁ due to is balanced without being passed through the second coil 2 and there is no inductive coupling between the two, the resonance characteristic thereof has a sharp peak as shown in FIG. Becomes On the other hand, as shown in FIG. 11B, the orthogonal state of the two coils 1 and 2 collapses due to the geometrical imbalance of the two coils 1 and 2 and the influence of an accompanying circuit. When the magnetic flux φ ₂ generated by the first coil 1 passes through the second coil 2, this becomes a coupled magnetic flux and the magnetic flux balance is lost, and inductive coupling occurs between the two. Then, when the degree is still small, the resonance characteristics deteriorate as shown in (b) of FIG. 10 because of mutual load, and when the coupling becomes larger, a valley occurs in the tuning frequency as shown in (c). Signal reception becomes impossible.

Therefore, conventionally, in order to prevent the above-mentioned inductive coupling, a conductive plate 5 is attached to a part of the receiving coil 3 as shown in FIG. 11 (b), and the conductive plate 5 acts as a high frequency shield. The above problem was addressed by reducing the coupling magnetic flux φ ₂ and balancing the magnetic fluxes of the two coils 1 and 2.

[0006]

However, in the conventional receiving coil 3 of the quadrature receiving system, in order to prevent the inductive coupling between the two coils 1 and 2, a part of the receiving coil 3 is used. Since the magnetic flux balance is adjusted by attaching the conductive plate 5 and changing the area and the mounting position of the conductive plate 5, it is difficult to find a delicate optimum point of the magnetic flux balance, and the adjustment is difficult. It was both time consuming and time consuming. Further, as described above, the conventional receiving coil 3 involves mechanical changes,
It was difficult to adjust from the outside by remote control. Therefore, originally, it is necessary to finely adjust the magnetic flux balance to the optimum point each time the receiving coil is attached to each subject, but in reality, the adjustment is almost impossible. In addition, the conductive plate 5 attached to the receiving coil 3
The mounting position and the area of can not be changed freely, and the quadrature receiving method cannot be applied to the flexible coil using the flexible conductor loop.

Therefore, the present invention addresses such a problem and makes it possible to electrically adjust the orthogonal axes of the coils of the two systems arranged so that the receiving sensitivity directions are orthogonal to each other, and appropriately perform the orthogonal adjustment. An object of the present invention is to provide a quadrature reception type reception coil and a magnetic resonance imaging apparatus using the reception coil as a reception coil in a reception system.

[0008]

In order to achieve the above object, a quadrature receiving type receiving coil according to the present invention uses three or more conductor loops each having a different receiving sensitivity direction and forming a resonance system. Are combined to form two systems of coils having one or more conductor loops, and the resonance frequency of each conductor loop of each system is adjusted so that the receiving sensitivity direction of the coils of the two systems is changed. This is so that they can be adjusted so as to be orthogonal to each other.

A magnetic resonance imaging apparatus as a related invention of the receiving coil of the quadrature receiving system is a static magnetic field generating means for applying a uniform static magnetic field to a subject and a gradient magnetic field generating means for applying a gradient magnetic field to the subject. A transmission system for irradiating a high frequency signal in order to cause nuclear magnetic resonance to the atomic nuclei of the biological tissue of the subject, and a reception system for detecting a high frequency signal emitted by the nuclear magnetic resonance,
In a magnetic resonance imaging apparatus including a signal processing system that performs an image reconstruction calculation using a high frequency signal detected by this reception system, a quadrature reception system configured as described above as a reception coil in the reception system. The receiver coil is used.

[0010]

The receiving coil of the quadrature receiving system configured as described above uses three or more conductor loops having different receiving sensitivity directions and forming a resonance system, and is formed by combining them. In a two-system coil having conductor loops, the resonance frequencies of the individual conductor loops of each system are adjusted so that the receiving sensitivity directions of the two system coils are orthogonal to each other. This electrically adjusts the orthogonal axes of the above two coils,
The orthogonal adjustment can be easily performed as appropriate.

Further, the magnetic resonance imaging apparatus configured as described above has a receiving coil in its receiving system,
By using a quadrature receiving type reception coil in which the quadrature axes of the coils of the above two systems are electrically adjusted and quadrature adjustment can be easily performed appropriately, the magnetic flux balance for each attachment of the reception coil to each subject. Can be finely adjusted to the optimum point, and a good diagnostic image can be obtained.

[0012]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory view showing the principle and basic configuration of a receiving coil 10 of the quadrature receiving system according to the present invention,
FIG. 2 is a circuit diagram showing a connection state of the receiving coil 10. This quadrature reception type reception coil 10 is used as a reception coil in a reception system of a magnetic resonance imaging apparatus, and as shown in FIG. 1, a coil 11, a coil 12, and a coil 13 having mutually different reception sensitivity directions. , And are combined to form a two-system coil as a whole.

The first coil 11 has a conductor loop L ₁
And the resonance capacitance C form a resonance system, which is tuned to the signal frequency by the resonance system and has a sensitivity direction in the direction indicated by an arrow P, for example. The coil 11 is formed. Second coil 1
Reference numeral ₂ is a resonance system composed of another conductor loop L ₂ and a variable resonance capacitance C ′. By finely adjusting the resonance frequency by the variable resonance capacitance C ′, for example, the sensitivity direction is indicated by the arrow R. Can be set. further,
The third coil 13 forms a resonance system with the other conductor loop L ₃ and the variable resonance capacitance C ′. By finely adjusting the resonance frequency by the variable resonance capacitance C ′,
For example, the sensitivity direction can be set in the direction indicated by arrow Q. The two coils 12 and 13 are combined to form the second coil 14 of the other system. In this case, the combined sensitivity direction of the second coil 14 as a whole is set to the direction indicated by the arrow S, for example.

In this state, the receiving coil 10 of the present invention is formed by using the first coil 11 as one system and the second coil 14 as two systems. Then, the resonance frequency of each of the conductor loops L ₂ and L ₃ of the second coil 14 is adjusted, and the combined sensitivity direction S is arbitrarily swung within a certain range, so that the combined sensitivity direction S is changed to the above-mentioned first direction. Sensitivity direction P of coil 11
Can be adjusted to be orthogonal to. Therefore, the combination of the first coil 11 and the second coil 14 can realize the receiving coil 10 in which the orthogonal axes can be electrically adjusted. However, the sensitivity directions P, Q, and R of the coils 11, 12, and 13 must be signal directions determined by the spin rotation plane.

FIG. 2 is a circuit diagram showing the connection of the quadrature receiving type receiving coil 10 configured as described above. In the figure, reference numeral 15 indicates a receiving circuit, which amplifies and outputs a high frequency signal detected by the receiving coil 10. First, the first coil 11 is tuned to the signal frequency by the conductor loop L ₁ and the resonance capacitance C and the capacitance between the junctions of the variable capacitance diode VD. The high frequency signal detected by the first coil 11 is input to the first preamplifier 16a via the DC blocking capacitance C ″ in the receiving circuit 15. At this time, the control unit of the magnetic resonance imaging apparatus (not shown). The first D / A converter 17a controlled by the control signal C ₁ sent from the device provides a tuning voltage, and the resistance R suppresses the influence on the receiving operation. From which an output signal S ₁ is obtained.

Next, the second coil 14 has a variable resonance capacitance C'comprising a conductor loop L ₂ and a resonance capacitance C, and a variable capacitance diode for orthogonal axis adjustment connected to a part of the resonance capacitance C. And a coil 12 having another conductor loop L ₃ and a resonance capacitance C, and a variable resonance capacitance C ′ including a variable capacitance diode for orthogonal axis adjustment connected to a part of the resonance capacitance C. And the variable resonance capacitors C ′ of the coils 12 and 13 are connected in opposite directions, and in this state, the coils 12 and 13 are connected in parallel. Similar to the first coil 11, the second coil 14 is given a tuning voltage by the second D / A converter 17b controlled by the control signal C ₂ and is amplified by the second preamplifier 16b. Output signal S ₂
Is obtained. At this time, the second coil 14, the control signal C ₃ third D / A converter 17c is connected to be controlled by, is balanced controlled by the control signal C _3, the two coils 12, 13 Only the axis orthogonal to the first coil 11 can be changed without changing the tuning frequency as a whole.

Next, the tuning operation of the quadrature receiving type receiving coil 10 represented by the circuit diagram shown in FIG. 2 will be described with reference to FIG. First, at timing a shown in FIG. 3F, the first coil 11 alone is tuned. At this time, the coils 12 and 13 forming the second coil 14
It is necessary to eliminate the influence of the negative voltage of −V from the second D / A converter 17b to the second coil 14 by the control signal C ₂ shown in FIG. 2 (see FIG. 3D). Is applied,
This is realized by causing a forward current to flow through the variable capacitance diode VD to make it conductive, and performing sufficient detuning. In this state, the first D / A converter 17 is controlled by the control signal C ₁ shown in FIG.
By changing the output voltage of a, the tuning point α at which the maximum output is obtained from the output signal S ₁ of the first coil 11 as shown in FIG. In the control signal C ₁ for

Next, at the timing b shown in FIG. 3 (f), the tuning point β of the second coil 14 (see FIG. 3 (d)) with the first coil 11 detuned in the same manner as described above. )
To decide. At this time, the control signal C ₃ for adjusting the orthogonal axis shown in FIG. 2 is controlled by the voltage Vd (see FIG. 3 () in which the variable capacitance diodes forming the variable resonance capacitances C ′ of the coils 12 and 13 have the same capacitance. e)), the third D
It is set so as to be supplied from the / A converter 17c. In this state, the control signal C ₂ shown in FIG.
By changing the output voltage of the converter 17b, the tuning point β at which the maximum output can be obtained from the output signal S ₂ of the coil 14 as shown in FIG. 3 (b) is applied to the coil 14 as shown in FIG. 3 (d). Determined in control signal C ₂ .

Next, at the timing c shown in FIG. 3 (f), when the coil 11 and the coil 14 are simultaneously operated at their tuning points α and β, as described above in the state where the orthogonality is not sufficiently taken. Is observed as a decrease in reception sensitivity. Therefore, the control signal C for adjusting the orthogonal axis shown in FIG.
_The balanced voltage is changed by the third D / A converter 17c controlled by _{3, and the} maximum output of both the output signals S ₁ and S _{2 of the} coils 11 and 14 as shown in FIGS. 3 (a) and 3 (b). A point γ at which the following is obtained is determined in the control signal C ₃ as shown in FIG. This is a state in which the orthogonal state of the first coil 11 and the second coil 14 is realized,
When the high-frequency signal is received by each of the control signals C ₁ , C ₂ , and C ₃ determined as described above, the output signals S ₁ and S ₂ with the maximum sensitivity are output as shown at the timing d in FIG. Obtainable.

The output signal S of the receiving coil 10 is
₁ and S ₂ are input to the shifter 18 shown in FIG. The output signal S ₁ from the coil 11 shown in FIG. 2 is input to the first attenuator (ATT) 19a and adjusted to have a waveform as shown in FIG. Further, the output signal S ₂ from the coil 14 shown in FIG. 2 is input to the second attenuator (ATT) 19b and adjusted to have a waveform as shown in FIG. 5 (b). Then, the signal output from the first attenuator 19a is input to the next phase corrector (PS) 20 and the phase difference is corrected, and the waveform is as shown in FIG. 5C. afterwards,
The signal from the phase corrector 20 and the second attenuator 19
The signal from b is input to the adder 21 and is combined to form a waveform as shown in FIG. As a result, the signal voltage of the signal output from the shifter 18 is twice as high as that input from the receiving circuit 15 as is clear from FIG. 5, but the noise voltage has no correlation and thus is averaged. Therefore, the total S / N ratio can be improved by about 40%. However, this is the case where there is no difference in sensitivity between the two systems of coils 11 and 14.

FIG. 6 is an exploded perspective view showing another embodiment of the receiving coil 10 of the quadrature receiving system according to the present invention. In the case of the magnetic resonance imaging apparatus of the vertical magnetic field system, the rotation plane of the nuclear spins is the horizontal plane, and the sensitivity direction of the receiving coil 10 needs to be in the horizontal plane. Therefore, in general, the receiving coil 10 of the orthogonal receiving system is
A combination of a solenoid coil and a saddle coil is used. In FIG. 6, a solenoid type coil is used as the first coil 11, and a saddle type coil is used as the two coils 12 and 13 forming the second coil 14. Then, as shown in FIG. 6, the shapes of the conductor loops L ₂ and L ₃ of the coils 12 and 13 composed of the saddle type coil are changed to the intermediate members at both ends of a linear intermediate member extending in parallel. When the shape is such that the end members are orthogonal and project in semi-circular shapes in mutually opposite directions, the sensitivity directions of the conductor loops L ₂ and L ₃ are different, and the receiving coil 10 that can appropriately change the orthogonal axis is configured. .

FIG. 7 is a perspective view showing an embodiment in which the receiving coil 10 of the orthogonal receiving system according to the present invention is applied to the flexible coil 22. The flexible coil 22 is a coil that uses a flexible conductor loop, has the advantage that it can be deformed according to the body shape of the subject, has good wearability, and does not cause discomfort to the subject. In this embodiment, as the conductor loop of the flexible coil 22 as described above, two systems of coils 11 and 14 in which the orthogonal axes shown in FIG. 1 or 6 are electrically adjustable are used, and the base end of the coil conductor is used. A main connector 23 is provided at one end and a plurality of coil diameter adjusting connectors 24a, 2 are provided at the other end at appropriate intervals.
4b and 24c are provided, and the diameter of the flexible coil 22 is appropriately variable. Reference numeral 25 indicates an output connector. And generally, the sensitivity of the receiving coil is
It is known that the smaller the diameter is, the higher the diameter is. Therefore, the flexible coil 22 capable of selecting the optimum diameter according to the size of the subject can have good sensitivity according to the subject. Further, in the case of the present embodiment, the quadrature axis of the quadrature reception type reception coil 10 composed of two systems of coils can be adjusted each time the reception coil is attached to the subject, so that the reception coil which has been impossible in the past can be adjusted. It becomes possible to deform, and the sensitivity can be further improved. In particular, a receiving coil having the best sensitivity in the trunk region can be realized.

In the circuit diagram shown in FIG. 2, the adjustment of the orthogonal axes is electrically controlled by software using a variable resonance capacitance C'composed of variable capacitance diodes connected to the coils 12 and 13. However, the present invention is not limited to this, and a variable capacitor may be used as the variable resonance capacitor C ′ and may be manually adjusted.

FIG. 8 is a block diagram showing an embodiment of a magnetic resonance imaging apparatus using the receiving coil of the quadrature receiving system constructed as described above. This magnetic resonance imaging apparatus obtains a tomographic image of a subject by using a nuclear magnetic resonance (NMR) phenomenon, and as shown in FIG. 8, a static magnetic field generating magnet 26, a gradient magnetic field generating system 27, and a transmission magnetic field generating system 27. It comprises a system 28, a receiving system 29, a signal processing system 30, a sequencer 31, and a central processing unit (CPU) 32.

The static magnetic field generating magnet 26 is for generating a strong and uniform static magnetic field around the subject 33 in the body axis direction or in the direction orthogonal to the body axis. A magnetic field generating means of permanent magnet type, normal conducting type or superconducting type is arranged in the space provided. The gradient magnetic field generation system 27 is composed of a gradient magnetic field coil 34 wound in three axial directions of X, Y and Z, and a gradient magnetic field power source 35 for driving each coil, and a sequencer 3 to be described later.
By driving the gradient magnetic field power supply 35 of each coil in accordance with the instruction from 1, the gradient magnetic fields Gx, Gy, Gz in the three axial directions of X, Y, Z are applied to the subject 33. Depending on how this gradient magnetic field is applied, the subject 33
You can set the slice plane for.

The transmission system 28 irradiates a high frequency signal in order to cause a magnetic resonance to the atomic nuclei of the atoms constituting the biological tissue of the subject 33 by the high frequency magnetic field pulse sent from the sequencer 31 described later, and the high frequency oscillator. 36, a modulator 37, a high-frequency amplifier 38, and an irradiation coil 39, the high-frequency pulse output from the high-frequency oscillator 36 is amplitude-modulated by the modulator 37 according to a command from the sequencer 31, and the amplitude-modulated high-frequency pulse is high-frequency-modulated. Amplifier 3
After being amplified in 8, the electromagnetic wave is applied to the subject 33 by supplying it to the irradiation coil 39 arranged close to the subject 33.

The receiving system 29 detects a high frequency signal (NMR signal) emitted by magnetic resonance of atomic nuclei of a living tissue of the subject 33, and the receiving coil 10 and the receiving circuit 15 are provided.
, Shifter 18, quadrature detector 40, and A / D converter 4
1 and a response electromagnetic wave (NMR signal) of the subject 33 due to the electromagnetic wave emitted from the irradiation coil 39 is detected by the receiving coil 10 arranged close to the subject 33, and the receiving circuit 15 and the shifter 18 are provided. In addition, it is input to the A / D converter 41 via the quadrature phase detector 40 to be converted into a digital amount, and is further converted into two series of collected data sampled by the quadrature phase detector 40 at the timing according to the instruction from the sequencer 31. The signal is sent to the signal processing system 30.

The signal processing system 30 includes a CPU 32, a recording device such as a magnetic disk 42 and an optical disk 43, and a C
The CPU 32 comprises a display 44 such as an RT
Fourier transform, calculation of correction coefficient, image reconstruction, etc. are performed, and the signal intensity distribution of an arbitrary cross section or the distribution obtained by performing appropriate calculation on a plurality of signals is imaged and displayed as a tomographic image on the display 44. It is like this.

The sequencer 31 serves as a control means for repeatedly applying a high frequency magnetic field pulse for causing magnetic resonance to atomic nuclei of the atoms constituting the biological tissue of the subject 33 in a predetermined pulse sequence, and is controlled by the CPU 32. It operates and sends various commands necessary for collecting data of a tomographic image of the subject 33 to the transmission system 28, the gradient magnetic field generation system 27, and the reception system 29.

Here, in the present invention, the receiving system 2 is used.
As the receiving coil 10 within 9, the receiving coil 10 shown in FIG.
It is assumed that the system consists of coils 11 and 14, and the receiving circuit 1
5 has the circuit configuration shown in FIG. 2, and the shifter 18 has the circuit configuration shown in FIG. With such a configuration, by using the receiving coil of the orthogonal receiving system as the receiving coil 10 in the receiving system 29, the orthogonal adjustment of the coils 11 and 14 of the two systems can be easily performed, and the individual subject 3
The magnetic flux balance can be finely adjusted to the optimum point each time the receiving coil 10 is attached to the No. 3, and a good diagnostic image can be obtained.

[0031]

Since the receiving coil of the quadrature receiving system according to the present invention (see FIG. 1) is configured as described above, three or more conductor loops L ₁ having different receiving sensitivity directions and forming resonance systems are formed. L ₂ and L ₃ are used and are formed by combining them and have one or more conductor loops 2
In the coils 11 and 14 of the system, by adjusting the resonance frequencies of the individual conductor loops of each system, the receiving sensitivity directions of the coils 11 and 14 of the two systems can be adjusted to be orthogonal to each other. As a result, the orthogonal axes of the coils 11 and 14 of the two systems can be electrically adjusted, and the orthogonal adjustment can be easily performed appropriately. Further, according to the present invention, the quadrature reception method can be applied to the flexible coil using the flexible conductor loop.

Since the magnetic resonance imaging apparatus according to the present invention (see FIG. 8) is constructed as described above, the receiving coil 10 in the receiving system 29 has the orthogonal axes of the coils 11 and 14 of the above two systems. Fine adjustment of the magnetic flux balance to an optimum point each time the receiving coil 10 is attached to an individual subject by using a receiving coil of an orthogonal receiving system that is electrically adjusted so that orthogonal adjustment can be easily performed appropriately. Therefore, a good diagnostic image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle and basic configuration of a reception coil of a quadrature reception system according to the present invention,

FIG. 2 is a circuit diagram showing a connection state of the receiving coil,

3 is a timing diagram for explaining a tuning operation of a receiver coil of a quadrature receiving system represented by the circuit diagram shown in FIG.

FIG. 4 is a block diagram showing an internal configuration of a shifter that processes an output signal of the receiving coil.

FIG. 5 is a waveform diagram showing a signal waveform in the shifter,

FIG. 6 is an exploded perspective view showing another embodiment of a quadrature receiving type receiving coil according to the present invention;

FIG. 7 is a perspective view showing an embodiment in which a quadrature receiving type receiving coil according to the present invention is applied to a flexible coil;

FIG. 8 is a block diagram showing an embodiment of a magnetic resonance imaging apparatus using the above-described quadrature reception type receiving coil.

FIG. 9 is an explanatory view showing a conventional quadrature receiving system receiving coil;

FIG. 10 is a graph showing the resonance characteristic of the reception coil of the orthogonal reception system,

FIG. 11 is a perspective view illustrating a coping means when inductive coupling occurs between coils of two systems in a conventional quadrature receiving type receiving coil.

[Explanation of symbols]

10 ... Receiving coil, 11 ... First coil, 12, 1
3 ... coil, 14 ... second coil, 15 ... receiving circuit, 18 ... shifter, 22 ... flexible coil,
26 ... Static magnetic field generating magnet, 27 ... Gradient magnetic field generating system,
28 ... Transmission system, 29 ... Reception system, 30 ... Signal processing system,
31 ... Sequencer, 32 ... CPU, 33 ... Subject,
L ₁ , L ₂ , L ₃ ... Conductor loop, C ... Resonance capacitance,
C '... Variable resonance capacitance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 7621-2J G01R 33/22 P

Claims (2)

[Claims] 1. Use of three or more conductor loops having mutually different receiving sensitivity directions and forming respective resonance systems, and having one or two or more conductor loops by combining them.
A system coil is formed, and by adjusting the resonance frequency of each conductor loop of each system, the receiving sensitivity directions of the coils of the two systems can be adjusted so as to be orthogonal to each other. Quadrature receiver type receiving coil. 2. A static magnetic field generating means for applying a uniform static magnetic field to a subject, a gradient magnetic field generating means for applying a gradient magnetic field to the subject, and nuclear magnetic resonance in atomic nuclei of atoms constituting the biological tissue of the subject. To irradiate a high-frequency signal in order to wake up, a receiving system to detect the high-frequency signal emitted by the above-mentioned nuclear magnetic resonance, and a signal to perform image reconstruction operation using the high-frequency signal detected by this receiving system A magnetic resonance imaging apparatus comprising a processing system, wherein the receiving coil of the orthogonal receiving system according to claim 1 is used as a receiving coil in the receiving system.