JPH10262949A - Magnetic resonance imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging(MRI) device small in sized and equipped with a non-magnetic balance/imbalance converting circuit and a QD adder. SOLUTION: Two coils 31 and 32 are high frequency coils for reception for detecting an NMR signal from a subject and they are quadrature coils. The signal voltages detected by the respective coils are transmitted through coaxial cables 35 and 36 to preamplifiers 9A and 9B and amplified by balance/ imbalance conversion at balance/imbalance converting circuits 33 and 34. The outputs of preamplifiers 9A and 9B are inputted to a QD adder 37. When the phase of signal from the coil 32 is delayed at 90 deg. from the signal from the coil 31, at the QD adder 37, the received signal from the coil 31 is added with the received signal from the coil 32 after its phase is delayed at 90 deg., and that signal is transmitted to a receiver. Both the balance/imbalance converting circuits 33 and 34 and the QD adder 37 are provided with π type low-pass filters composed of L and C as centralized constant components, and these low-pass filters consist a phase shifter of single or multistage connection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging apparatus (hereinafter, referred to as "MRI apparatus"), and more particularly to a signal detecting means for detecting a nuclear magnetic resonance signal (hereinafter, referred to as "NMR signal").

[0002]

2. Description of the Related Art As a high-frequency coil for reception, which is a signal detecting means in an MRI apparatus, a multiple element type having good uniformity of current distribution is used for photographing the entire head and abdomen according to a target part of a subject. For imaging a specific part, various shapes such as a surface coil are used.

[0003] A signal received by a high-frequency coil for reception is amplified by a preamplifier and transmitted to a receiver. For this signal transmission, a coaxial cable with little signal loss and less susceptible to inductive noise is used. A coaxial cable is an unbalanced circuit because it has a structure in which a central conductor is covered with a dielectric and its periphery is surrounded by an outer conductor. Also, the preamplifier is desirably an amplifier with as low noise as possible, and therefore is usually an unbalanced circuit whose ground potential is definitely determined.

On the other hand, a receiving high-frequency coil is a balanced circuit in which any part of the circuit is not grounded. Therefore, connecting the receiving high-frequency coil and the preamplifier with a coaxial cable directly connects the balanced circuit and the unbalanced circuit. In this case, since current flows through the outer conductor of the coaxial cable, the vibration of the coaxial cable affects the characteristics of the receiving high-frequency coil, and the characteristics become unstable. Also, it becomes easier to pick up noise. Therefore, when connecting a balanced circuit and an unbalanced circuit, the two circuits are connected via a balanced-unbalanced conversion circuit called a balun.

[0005] Baluns are generally used in the field of wireless communication, and there are LC baluns based on lumped constants and baluns based on distributed constants. LC baluns with lumped constants utilize toroidal cores. However, the MRI apparatus generates a strong magnetic field having a static magnetic field strength of 1.5 T or more. In this strong magnetic field, the toroidal core causes magnetic saturation and cannot be used. In addition, the magnetic material disturbs the distribution of the static magnetic field and the high-frequency magnetic field,
It cannot be used because it distorts the reconstructed image.

The balun based on the distributed constant includes a supertop, a branch conductor balun, a U-shaped balun, and the like. In any of these, when the receiving end of the coaxial cable is opened or short-circuited, the impedance from the transmitting end of the coaxial cable becomes zero or infinite at a certain length corresponding to the wavelength of the desired frequency, or It utilizes the property of the wavelength matching cable that the phases of the voltages at the transmitting end and the receiving end are opposite. For example, in the case of a U-shaped balun, a wavelength matching cable having a length of λ / 2 (λ is a wavelength) is used. In the case of an MRI apparatus with a static magnetic field strength of 1.5 T, the received NM
The frequency of the R signal is about 64 MHz, and λ / 2
Has a length of about 1.6 m. In an MRI apparatus having a smaller static magnetic field strength, the length of the wavelength matching cable of λ / 2 increases in inverse proportion to the static magnetic field strength.
When this balun is used, for each high-frequency coil for reception,
It is necessary to provide a cable of this length. For example,
In the case of a single quadrature (hereinafter abbreviated as QD) coil, two for each receiving port,
In the case of a coil composed of a plurality of coils such as an array coil, it is necessary to provide the same number of coils as the number of coils, resulting in a very complicated structure. Therefore, it is required that the balun to be connected to the receiving high-frequency coil be as small as possible and made up of only non-magnetic components without using a toroidal core or the like.

As a known example in which the above U-shaped balun is made into a lumped constant, a QD plane coil for spectroscopy (SMRM (Society of Ma
genetic Response in Medic
ine) Proceedings, p. E. FIG. Lenkinsk
i, et al., QD planar coil for P-31 spectroscopy (A Quadrature Planar Co.)
il for P-31 MR Spectrosco
py)). In this example, a balun is formed by connecting two stages of λ / 4 impedance inverting circuits. In this case, a narrow band balun can be realized, but the cutoff frequency is relatively close to the desired signal frequency. for that reason,
When a resonance system circuit is used for a circuit connected to the output side of the balun, for example, a matching circuit of the preamplifier, the balun and the matching circuit may interfere with each other to cause performance degradation such as a decrease in noise figure (NF).

[0008] As in the case of the balun, a 90-degree phase shift adder (hereinafter referred to as a QD adder) which has conventionally been constituted by a wavelength matching cable and is desired to be miniaturized.
There is. The QD adder adds two signals to the signal A detected by the QD coil and the signal B whose phase is delayed by 90 degrees from the signal A after delaying only the signal A by 90 degrees by the phase shifter. is there. As a method of the QD adder, a transformer-coupled quadrature hybrid
Ring directional coupler (branched hybrid), 9
0 degree phase shifter + resistance adder.

A QD adder using a λ / 8 wavelength matching cable has been reported (SMRM (1991)
ociety of Magnetic Resona
nce in Medicine) Proceedings 124 pages, J
effrey R.E. Fitzsimmons et al., Double Resonance Quadrature Birdcage (A Double)
Resonant Quadrature Bird
cage)). This QD adder is useful because it has a small number of components and can be composed of non-magnetic components. Again, 2
A λ / 8 wavelength matching cable is used.

[0010]

As described above, in the prior art, a wavelength matching cable or the like is used for a balanced-unbalanced conversion circuit or a QD adder of a signal detecting means for detecting an NMR signal of an MRI apparatus. Therefore, it was difficult to reduce the size. Therefore, an object of the present invention is to provide an MRI apparatus including a small non-magnetic balanced-unbalanced conversion circuit and a QD adder.

[0011]

In order to achieve the above object, an MRI apparatus according to the present invention comprises a magnetic field generating means for generating each of a static magnetic field, a gradient magnetic field and a high-frequency magnetic field, and an NMR signal from an object to be inspected. Signal detecting means for detecting the NM
A receiver for receiving the R signal; signal processing means for performing signal processing and calculation for image reconstruction based on the NMR signal from the receiver; and output means for outputting a calculation result of the signal processing means. The MRI apparatus, wherein the signal detecting means comprises a receiving high-frequency coil for receiving a high-frequency signal from a test object, a balanced-unbalanced conversion circuit, and a QD adder. And / or Q
The D adder is composed of lumped components.

In this configuration, the balanced-unbalanced conversion circuit, Q
Since the D adder is constituted by lumped components without using a conventional wavelength matching cable, downsizing is achieved, and the signal detecting means can be integrated in the receiving high-frequency coil.

[0013] In the MRI apparatus of the present invention, the lumped component is non-magnetic. In this configuration, since the lumped constant components forming the balanced-unbalanced conversion circuit and the QD adder are non-magnetic, the signal detecting means including these components can be used in a static magnetic field.

In the MRI apparatus of the present invention, the balance-
The unbalanced conversion circuit is configured by connecting at least one or more low-pass filters (claim 3). In this configuration, by employing a low-pass filter of one or more stages in the balanced-unbalanced conversion circuit, it is possible to replace the wavelength matching cable with a lumped constant circuit, increase the cutoff frequency, and increase the bandwidth. Also becomes wider.

[0015] In the MRI apparatus according to the present invention, the QD adder includes at least one or more low-pass filters. With this configuration, the same effect as in the case of the balanced-unbalanced conversion circuit can be obtained.

In the MRI apparatus of the present invention, the balance-
The unbalanced conversion circuit and / or the QD adder are mounted on a printed circuit board. Since the balanced-unbalanced conversion circuit and the QD adder are configured using lumped components such as an inductance and a capacitor, they can be mounted on a printed circuit board.

In the MRI apparatus of the present invention, the balance-
An unbalanced conversion circuit and / or a QD adder are built in the high-frequency receiving coil. The balanced-unbalanced conversion circuit and the QD adder have been miniaturized and can be mounted on a printed circuit board, so that they can be incorporated in a receiving high-frequency coil.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 shows an MRI to which the present invention is applied.
It is a block diagram of an apparatus. In FIG. 2, a static magnetic field coil for generating a static magnetic field in a measurement space in which a subject 4 is placed, a gradient magnetic field coil for generating gradient magnetic fields in X, Y, and Z directions orthogonal to each other, and irradiating the subject 4 An irradiation high-frequency coil 8 for generating a high-frequency magnetic field is provided, and a reception high-frequency coil 21 and a detected NMR signal as signal detection means for detecting an NMR signal generated from the subject 4 by the high-frequency magnetic field emitted from the irradiation high-frequency coil 8. A preamplifier 9 for amplifying the signal is provided, and the detected NM
The R signal is transmitted to the receiver 17.

The driving system for driving each of the coils includes a static magnetic field coil driving power supply 2 for driving the static magnetic field coil 1, a gradient magnetic field coil 3, and a magnetic field distribution in the measurement space where the subject 4 is placed. , A high-frequency pulse generator 6 for generating a high-frequency pulse for generating a high-frequency magnetic field from the high-frequency coil 8 for irradiation, a power amplifier 7 for amplifying the high-frequency pulse, and The control device 5 is connected to the gradient magnetic field coil drive power supply 14 and the high frequency pulse generator 6 and outputs various commands to each device at a fixed timing.

The receiver 17 is connected to the high-frequency pulse generator 6, and generates a detection signal generator 15 for generating two reference signals having phases different from each other by 90 degrees, and two detectors 10A and 10A.
10B, the detectors 10A and 10B receive the reception signal from the preamplifier 9 and the detection signal from the detection signal generator 15, perform quadrature detection, and output an analog signal including a real part and an imaginary part. I do.

The signal processing system includes two detectors 10A and 10A.
A / D converter 11 for converting an analog signal consisting of a real part and an imaginary part sent from B into a digital signal
A, 11B, a signal processing device 1 that performs arithmetic processing for image reconstruction from a real part digital signal and an imaginary part digital signal
2, and a display device 13 which is an output means for displaying the result of the arithmetic processing.

In this MRI apparatus, the output of the high-frequency pulse generator 6 is amplified by the power amplifier 7 to excite the high-frequency coil 8 for irradiation, and a high-frequency magnetic field is emitted from the high-frequency coil 8 to the subject 4. In addition, the gradient magnetic field coil 3 is driven by each drive power supply 14 of the gradient magnetic field coil 3 in the three-axis direction, so that the gradient magnetic field is superposed in a pulse shape on the static magnetic field. The application of the high-frequency magnetic field and the gradient magnetic field is repeated in a predetermined pulse sequence under the control of the control device 5. The NMR signal generated in the subject 4 based on such a pulse sequence is received by the receiving high-frequency coil 21 of the signal detecting means, and the signal component is amplified by the preamplifier 9 and then transmitted to the receiver 17. .

Next, a first embodiment of the signal detecting means of the present invention will be described with reference to FIG. FIG. 1 shows a first embodiment of the signal detecting means of the present invention. In FIG. 1, two coils 31 and 32 are NM from the subject 4.
A receiving high-frequency coil for detecting the R signal, which is a quadrature coil. The signal voltage detected by each coil is balanced-unbalanced by baluns 33 and 34, and then transmitted to preamplifiers 9A and 9B by coaxial cables 35 and 36.
Amplified. Outputs of the preamplifiers 9A and 9B are input to a QD adder 37. Assuming that the phase of the signal from the coil 32 is delayed by 90 degrees with respect to the signal from the coil 31, the QD adder 37 delays the phase of the received signal from the coil 31 by 90 degrees and receives the signal from the coil 32. The signal is added. The added signal is transmitted to the receiver 17.

FIG. 3 shows a second embodiment of the signal detecting means of the present invention. In the first embodiment shown in FIG. 1, the signal voltage is amplified by the preamplifier and then QD-added. In this embodiment, as shown in FIG.
After the D addition, the preamplifier 9 amplifies the signal voltage. In this configuration, the effect that the number of the preamplifiers 9 is half that of the first embodiment can be obtained.

In FIGS. 1 and 3, baluns 33 and 34 are shown.
Is a cable in which the cable portion of a U-shaped balun using a λ / 2 wavelength matching cable is replaced by a lumped constant circuit. λ /
The role of the second wavelength matching cable is to make the voltage phase difference between the balanced terminals 180 degrees. Thus, this cable can be replaced by a 180 degree phase shifter at the desired signal frequency.

The phase shifter in the lumped constant circuit is shown in FIG.
This can be realized by using a constant-K low-pass filter shown in FIG. Assuming that the cutoff frequency fc and the characteristic impedance of the constant K type low-pass filter (hereinafter abbreviated as filter) 41 are Z ₀ , C = 1 / (2π · fc · Z ₀ ) L = Z ₀ / (π · fc), a desired filter 41 can be formed using the capacitor C and the inductance L. For example, the cutoff frequency fc is 90 MHz, the characteristic impedance Z ₀ is 5
When 0Ω is set, C = 35.4 pF and L = 177 nH are obtained. The phase shift amount of this filter 41 at 64 MHz (the NMR signal frequency of the MRI apparatus with a static magnetic field strength of 1.5 T) is 90 degrees. This means that the filter 41 is 64 MHz
It shows that there is a 90-degree phase shifter, which is equivalent to a λ / 4 wavelength matching cable. Therefore, as shown in FIG. 4B, if the filter 41 of FIG. 4A, which is a 90-degree phase shifter, is connected in two stages, a 180-degree phase shifter can be obtained.
Corresponds to a 180-degree phase shifter.

Similarly, the cut-off frequency fc is set to 170M
Hz and the characteristic impedance is 50Ω, C = 1
8.7 pF, L = 94 nH are obtained. This filter 4
The phase shift amount at 64 MHz of 1A is about 45 degrees. This indicates that the filter 41A is a 45-degree phase shifter at 64 MHz and has properties equivalent to a λ / 8 wavelength matching cable. Therefore, this filter 41
If A is connected in four stages as shown in FIG. 4C, a 180-degree phase shifter (filter 43) can be realized. In the case of this filter 43, the number of components increases, but the cutoff frequency becomes higher than in the case of the filter 42 in which the 90-degree phase shifters of FIG. 4B are connected in two stages.
This means that the balun's bandwidth has increased,
As a circuit connected to the output of the balun, for example, when a resonance circuit is used as a matching circuit of the preamplifier, it is possible to prevent the balun and the matching circuit from interfering with each other and causing performance deterioration such as a decrease in noise figure (NF). .

The constant-K low-pass filter shown in FIG. 4A is of a π type, but is composed of a capacitor C 'and two inductances L' as shown in FIG. 4D. Equivalent properties can be obtained with the T-shaped filter 44 described below. In the case of the T-type filter 44, the cutoff frequency is f
c, if the characteristic impedance is Z ₀ , C ′ = 1 / (π · fc · Z ₀ ) L ′ = Z ₀ / (2π · fc · Z ₀ ) If a capacitor C ′ and an inductance L ′ are used, A filter 44 can be configured.

As with the balun described above, a QD adder has conventionally been constituted by a wavelength matching cable, and further downsizing is desired. FIG. 5 shows a conventional QD adder using a λ / 8 wavelength matching cable. As shown in FIG. 5, coaxial cables 51 and 52 wavelength-matched to λ / 8 are used. In this QD adder, the length of this coaxial cable is about 40c.
m and a frequency of about 21 cm for a reception signal having a frequency of 21 MHz, which is a problem when the cable is compactly mounted.

Therefore, the technique applied to the above balun is
We decided to apply to D adder. FIG. 6 shows an application example as a third embodiment of the present invention. In FIG. 6, QD
The wavelength matching cable of the adder is replaced by L and C lumped constant circuits. That is, the coaxial cables 51 and 52 which play the role of the wavelength matching cable in FIG. 5 are formed into a lumped constant circuit of the inductances 61 and 62 and the capacitors 65, 66, 67 and 68 which play the role of the phase shifter in FIG. Has been replaced. The values of the inductance and the capacitor of the lumped constant circuit may be determined in the same manner as in the case of the balun. For example, when a reception signal having a frequency of 64 MHz is targeted, the values of the inductances 61 and 62 are 94 nH, the values of the capacitors 63 and 64 are 47 pF, and the values of the capacitors 65 to 68 are 18 pF. Can be realized. Similarly, frequency 2
When a 1 MHz reception signal is targeted, the values of the inductances 61 and 62 are 282 nH, the values of the capacitors 63 and 64 are 150 pF, and the values of the capacitors 65 to 68 are 56 pF.
By doing so, a QD adder can be realized.

The inductance and capacitor used above are preferably small and non-magnetic. In particular, when a balun, a QD adder, and the like are directly connected to the receiving high-frequency coil 21, the receiving high-frequency coil 21 is inserted into the static magnetic field space of the MRI apparatus, so that the balun and the QD adder are configured. It is desirable that the inductance and the capacitor are small and non-magnetic. Taking the inductance used in the third embodiment of the present invention as an example, an inductance of 94 nH can be obtained by winding a copper wire having a wire diameter of about 0.7 mm for about 4 turns with an inner diameter of 5 mm, and an inductance of 282 nH is similarly obtained. It can be obtained by winding about 9 turns. If a capacitor having this inductance and the above-mentioned capacitance, for example, a ceramic capacitor, is used, a small size and non-magnetic property can be achieved.

By using a combination of the inductance and the capacitor as described above, small-sized mounting is facilitated, and mounting on a printed circuit board is possible. The embodiment will be described below.

FIG. 7 is a view showing the balun of the present invention formed on a printed circuit board. In FIG. 7, the printed circuit board 71 has a 40 μm copper foil conductor pattern (not shown because it is the back side in the figure) attached to a glass epoxy resin plate having a length of 3 cm, a width of 6 cm and a thickness of 1.6 mm. Input terminal 7
The output voltage of the receiving high-frequency coil is applied to 2, 73. Four coil elements 74 to 77 on printed circuit board 71
And the five capacitor elements 78 to 82 represent the respective lumped components illustrated in FIG. Here, the coil elements 74 to 77 are arranged such that their axes intersect perpendicularly with the adjacent coil elements so that mutual interference in the lines of magnetic force generated by the coils is minimized. Further, by changing the inductance value of the coil element and the gap between the windings, desired characteristics of the balun are obtained. Therefore, after the adjustment, the coil elements 74 to 77 are replaced with the silicon resin 8 so that the inductance value does not change due to mechanical vibration or the like.
Fixed at 3 to 86 on the printed circuit board 71. The output terminal of the circuit is a high-frequency coaxial connector (for example, MSS-L manufactured by Hirose Electric Co., Ltd.) so that an unbalanced coaxial cable can be connected.
(P-PC type) 87 is attached.

According to this embodiment, it is possible to easily adjust the characteristics of the circuit at low cost. Further, it is possible to minimize the mutual interference of the lumped components and to stabilize the characteristics after adjustment permanently. FIG. 7 illustrates the embodiment of the balun formed on the printed circuit board. However, the QD adder can be similarly configured, and the same effect can be expected.

As described above, the balun and the QD adder are miniaturized and can be mounted on a printed circuit board. As a result, the balun and the QD adder can be built in the high-frequency coil for reception. The embodiment will be described below.

FIG. 8 is an external view of a high-frequency coil for a head incorporating a balun according to the present invention. In FIG. 8, a high frequency coil unit 91 incorporates a multi-element type QD coil called a bird cage type (the details are described in Japanese Patent Application No. 6-51917 by the same inventor). The inner diameter of the high-frequency coil unit 91 has a cylindrical shape with a length of 28 cm and a length of 30 cm, and is large enough to receive a human head. After the head of the subject is placed on the head receiver 92, a mechanism for moving the high-frequency coil unit 91 along the guide rail 94 on the base 93 is incorporated. With such a configuration, the center of the high-frequency coil unit 91 can be accurately aligned with the examination region of the subject. Here, the NMR signal detected by the high-frequency coil is applied to a balun 95 disposed in a space provided below the high-frequency coil unit 91. The balun 95 is preferably the printed circuit board type described with reference to FIG.

With such a configuration, the balun 95 also moves in accordance with the movement of the high-frequency coil unit 91. Therefore, the NMR signal detected by the high-frequency coil is converted into an external signal processing system by a coaxial cable which is an unbalanced transmission line. Can be told. As a result, the NMR signal detected by the high-frequency coil is stable without induction of external noise, compared to the inspection method of selecting the optimal high-frequency coil according to the inspection site of the subject in order to obtain high-quality test results. Transmitted.

FIG. 8 illustrates the case where the balun is incorporated in the high-frequency coil assembly.
An additional D adder can be incorporated. In this case, since the number of coaxial cables for transmitting the NMR signal is one, the operation of arranging the high-frequency coil at the examination site of the subject is facilitated and the appearance is improved. It is also possible to incorporate the preamplifier shown in FIG. In this case, the weak signal of several μV detected by the high-frequency coil is converted to about several hundred millivolts (approximately 40 dB) and applied to the transmission line before being applied to the transmission line. It can be further reduced.

When a detector composed of a plurality of high-frequency receiving coils called a phased array coil or a multiple coil is used as the signal detecting means, the miniaturization of the balun is more effective in mounting and operability. It is. This is because even if the number of coils connecting the balun increases, the balun itself can be directly connected to the coil terminal portion and built into the coil because the balun itself is downsized. Also, Q
When a D-type phased array coil or multiple coils is used, miniaturization of the QD adder is as effective as miniaturization of the balun.

If a variable-capacity type capacitor such as a trimmer capacitor is used as the balun or QD coil capacitor of the present invention, the replacement of elements can be performed with respect to variations in inductance characteristics and variations in characteristics due to stray capacitance of the substrate. Can be fine-tuned without. Further, the present invention can be applied to an MRI apparatus having any static magnetic field strength by selecting L and C values corresponding to the NMR signal frequency.

[0041]

According to the present invention, by replacing the wavelength matching cable conventionally used as a phase shifter with a low-pass filter having an inductance L and a capacitor C as components, a non-magnetic and small-sized filter is provided. Balun and QD
An adder can be realized. Further, by using a phase shifter having a configuration in which a plurality of low-pass filters are connected, a balun having a wide bandwidth can be realized.

When a detector composed of a plurality of high-frequency coils for reception such as a phased array coil or a multiple coil is used, miniaturization of the balun requires mounting.
This is an essential condition for operability. Also, in the case of a QD type phased array coil or multiple coils, miniaturization of the QD adder is similarly effective, and both can be constituted by non-magnetic components, so that they can be mounted on the same printed circuit board. It can also be built into a high-frequency coil for use. Further, if a variable capacitance type capacitor is used, the characteristics of the balun and the QD adder can be easily adjusted without replacement of elements, and the adjustment time can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of signal detection means of the present invention.

FIG. 2 is a block diagram of an MRI apparatus to which the present invention is applied.

FIG. 3 is a diagram showing a second embodiment of the signal detecting means of the present invention.

FIG. 4 is a schematic diagram of a phase shifter using a constant K-type low-pass filter.

FIG. 5 shows a conventional Q using a λ / 8 wavelength matching cable.
D adder.

FIG. 6 is a diagram showing a third embodiment of the signal detecting means of the present invention.

FIG. 7 is a diagram in which the balun of the present invention is configured on a printed circuit board.

FIG. 8 is an external view of a high-frequency coil for a head incorporating a balun according to the present invention.

[Explanation of symbols]

9, 9A, 9B Preamplifier 10A, 10B Detector 15 Detection signal generator 17 Receiver 21, 31, 32 High-frequency coil for reception 33, 34 Balun 35, 36, 51, 52 Coaxial cable 37 QD adder 41, 42 , 43, 44 Constant-K low-pass filter (filter) 61, 62 Inductance 53, 54, 63, 64, 65, 66, 67, 68 Capacitor 55, 69 Terminating resistor 71 Printed circuit board 72, 73 Input terminal 74, 75 , 76, 77 Coil element 78, 79, 80, 81, 82 Capacitor element 83, 84, 85, 86 Silicon resin 87 High frequency coaxial connector 91 High frequency coil part 92 Head support 93 Base 94 Guide rail 95 Balun (printed board type)

Claims (6)

[Claims] A magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field; a signal detecting means for detecting a nuclear magnetic resonance signal (hereinafter, referred to as an NMR signal) from a test object; A receiver for receiving a signal, signal processing means for performing signal processing and calculation for image reconstruction based on the NMR signal from the receiver, and output means for outputting a calculation result of the signal processing means. In the magnetic resonance imaging apparatus, the signal detecting means includes a receiving high-frequency coil for receiving a high-frequency signal from a test object, a balanced-unbalanced conversion circuit, and a 90-degree phase shift adder. A magnetic resonance imaging apparatus, wherein the unbalanced conversion circuit and / or the 90-degree phase shift adder are formed by lumped components. 2. The magnetic resonance imaging apparatus according to claim 1, wherein said lumped element is non-magnetic. 3. The magnetic resonance imaging apparatus according to claim 1, wherein said balanced-unbalanced conversion circuit is configured by connecting at least one stage of a low-pass filter. apparatus. 4. The magnetic resonance imaging apparatus according to claim 1, wherein said 90-degree phase shift adder includes at least one or more low-pass filters. 5. A magnetic resonance imaging apparatus according to claim 1, wherein said balanced-unbalanced conversion circuit and / or a 90-degree phase shift adder are mounted on a printed circuit board. Imaging device. 6. The magnetic resonance imaging apparatus according to claim 1, wherein the balanced-unbalanced conversion circuit and / or a 90-degree phase shift adder are built in the high-frequency coil for reception. Magnetic resonance imaging device.