JP2004129689A - Radio frequency receiving coil and magnetic resonance imaging unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a radio frequency receiving coil and a magnetic resonance imaging unit which generate even heat. <P>SOLUTION: The first capacitor 206 positioned at a feeder part of a receiving loop 200 is provided with the first parallel resonance circuit 201, and the second parallel resonance circuit 202 is constituted of the second capacitor 205 adjacent thereto. The second parallel resonance circuit 202 is turned ON or OFF with a diode 209 through the first parallel resonance circuit 201 to make the impedance at the resonation of the second parallel resonance circuit 202 almost equal that of a parallel resonance circuit 208. This equalizes the heat generated in the radio frequency transmission thereby, realizing the even generation of heat by the radio frequency receiving coil 110. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an RF receiving coil having a magnetic coupling prevention circuit and a magnetic resonance imaging apparatus.
[0002]
[Prior art]
In recent years, in transmitting and receiving RF signals in a magnetic resonance imaging apparatus, an RF receiving coil may be used separately from an RF transmitting coil. At this time, a plurality of magnetic coupling prevention circuits for preventing magnetic coupling with the RF transmission coil at the time of transmitting an RF signal, for example, a parallel resonance circuit having a built-in cross diode are mounted on the RF reception coil. (For example, see Non-Patent Document 1).
[0003]
The parallel resonance circuit is also mounted on the power supply unit of the RF receiving coil, and enhances the effect of preventing magnetic coupling with the RF transmitting coil.
[0004]
[Non-patent document 1]
W. Edelstein, et al., "Electronic Decoupling of Surface-Coil Receivers for NMR Imaging and Spectroscopy, Journal of Magnetics and Spectroscopy". Magnetic Resonance), USA, 1986, 67, p. 156-161)
[0005]
[Problems to be solved by the invention]
However, according to the above-described related art, at the time of transmission, the heat-generating portion of the RF receiving coil becomes non-uniform, and the temperature may be locally increased. That is, since the impedance of the parallel resonance circuit of the power supply unit is different from the impedance of the other parallel resonance circuits, the amount of heat generated when current flows becomes non-uniform.
[0006]
In particular, it is not preferable from the viewpoint of safety when the subject is placed near the RF receiving coil to perform imaging when the heat generation amount becomes uneven depending on the location and the temperature may be locally high. .
[0007]
For these reasons, it is important how to realize an RF receiving coil and a magnetic resonance imaging apparatus that generate uniform heat.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the related art, and has as its object to provide an RF receiving coil and a magnetic resonance imaging apparatus that generate uniform heat.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, an RF receiving coil according to a first aspect of the present invention includes a magnetic coupling preventing circuit for preventing magnetic coupling with an RF transmitting coil in a capacitive coupling power supply unit. An RF receiving coil, wherein the power supply unit includes a first parallel resonance circuit for an RF signal in the first capacitor of the capacitive coupling, and a magnetic coupling prevention in a second capacitor adjacent to the first capacitor. And a switching means for turning on and off the magnetic coupling prevention circuit via the first parallel resonance circuit.
[0010]
According to the invention according to the first aspect, the power supply unit includes the first parallel resonance circuit for the RF signal in the first capacitor of the capacitive coupling unit, and the magnetic coupling prevention circuit in the first capacitor. Since the switching circuit turns on and off the magnetic coupling prevention circuit via the first parallel resonance circuit by the switching means, the first parallel resonance circuit has a high impedance when the RF signal is transmitted. Thus, the magnetic coupling prevention circuit does not cause an impedance change at the time of resonance via the power supply unit, and thus the impedance of the magnetic coupling prevention circuit in the power supply unit can be controlled to realize uniform heat generation.
[0011]
The RF receiving coil according to the second aspect of the present invention is characterized in that the first parallel resonance circuit is connected in parallel to the first capacitor.
[0012]
According to the second aspect of the invention, since the first parallel resonance circuit is connected in parallel to the first capacitor, a power supply line connected to the power supply unit and a reception line connected to the power supply line are provided. It is possible to prevent the influence of impedance caused by the circuit from exerting on the magnetic coupling prevention circuit.
[0013]
Further, in the RF receiving coil according to the third aspect of the present invention, the magnetic coupling prevention circuit includes a second parallel resonance circuit including the second capacitor and an inductor connected in parallel to the second capacitor. It is characterized by.
[0014]
According to the third aspect of the invention, the second parallel resonance circuit of the magnetic coupling prevention circuit includes the second capacitor and the inductor connected in parallel to the second capacitor. The second parallel resonance circuit serving as an impedance can be used as a magnetic coupling prevention circuit.
[0015]
Further, in the RF receiving coil according to a fourth aspect of the present invention, the switching means turns on and off the second parallel resonance circuit and simultaneously connects the first parallel resonance circuit and the first capacitor in parallel. It is characterized by turning on and off.
[0016]
According to the invention of the fourth aspect, the switching means turns on and off the second parallel resonance circuit and simultaneously turns on and off the parallel connection between the first parallel resonance circuit and the first capacitor. The first parallel resonance circuit can be turned off at the same time as the second parallel resonance circuit, which is the coupling prevention circuit, is turned off, so that the reception coil can operate normally.
[0017]
Further, the RF receiving coil according to the fifth aspect of the invention is characterized in that the switching means is turned on and off by a diode.
[0018]
According to the fifth aspect of the invention, since the switching means is turned on and off by the diode, the on / off operation can be performed electrically at a high speed.
[0019]
The RF receiving coil according to the invention of a sixth aspect is characterized in that the switching means includes a bias power supply for turning on and off the diode on a power supply line connected to the power supply unit.
[0020]
According to the invention of the sixth aspect, since the switching means includes the bias power supply for turning on and off the diode on the power supply line connected to the power supply unit, the power supply line for the bias power supply is not separately provided. Power can be supplied to the bias current without waste.
[0021]
An RF receiving coil according to a seventh aspect of the present invention is characterized in that the bias power supply includes a switch for switching a direction of an output current.
[0022]
According to the seventh aspect of the invention, the bias power supply switches the direction of the output current by the switch, so that the diode can be turned on and off.
[0023]
An RF receiving coil according to an eighth aspect of the present invention is characterized in that the power supply unit includes a balun in the first capacitor.
[0024]
According to the eighth aspect, since the power supply unit includes the balun in the first capacitor, the potential of the RF receiving coil can be stabilized, and the common mode noise can be reduced.
[0025]
A magnetic resonance imaging apparatus according to a ninth aspect of the present invention provides a static magnetic field forming means for forming a static magnetic field, a gradient magnetic field forming means for forming a gradient magnetic field, and transmitting a high-frequency magnetic field to a subject in the static magnetic field. Magnetic resonance imaging apparatus, comprising: an RF transmission coil for performing the control, an RF reception coil for receiving a magnetic resonance signal from the subject, and a control unit for controlling the gradient magnetic field forming unit, the RF transmission coil, and the RF reception coil. Wherein the RF receiving coil includes a magnetic coupling prevention circuit for preventing magnetic coupling with the RF transmitting coil in a capacitive coupling power supply unit, and the power supply unit includes a first capacitive coupling circuit. A first parallel resonance circuit of an RF signal in a capacitor; a magnetic coupling prevention circuit in a second capacitor adjacent to the first capacitor; and the magnetic coupling prevention circuit through the first parallel resonance circuit. Characterized in that it comprises a switching means for-off, the.
[0026]
According to the ninth aspect of the invention, the RF receiving coil has a magnetic coupling prevention circuit for preventing magnetic coupling with the RF transmitting coil in a capacitive coupling power supply unit, and the power supply unit supplies the RF signal with an RF signal. A first parallel resonance circuit is provided in a first capacitor of capacitive coupling, and a magnetic coupling prevention circuit is provided in a second capacitor adjacent to the first capacitor. Since this magnetic coupling prevention circuit is turned on and off via a circuit, the first parallel resonance circuit has a high impedance at the time of transmitting an RF signal, and the magnetic coupling prevention circuit detects the impedance change at the time of resonance via the power supply unit. This does not occur, and thus the impedance of the magnetic coupling prevention circuit in the power supply unit can be controlled to realize uniform heat generation.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of an RF receiving coil and a magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to this.
(Embodiment 1)
First, the overall configuration of the magnetic resonance imaging apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram showing the overall configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention. In FIG. 1, the magnetic resonance imaging apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106, an RF transmission coil 108, and an RF reception coil 110. In addition, the magnetic resonance imaging apparatus includes a gradient driving unit 130, a transmission driving unit 140, a data collection unit 150, a bias power supply unit 155, a scan controller unit 160, a data processing unit 170, a display unit 180, which drives and controls the magnet system 100. An operation unit 190 is provided.
[0028]
Each coil of the magnet system 100 has a substantially cylindrical shape, omitting the RF receiving coil 110, and is arranged coaxially with each other. A subject 1 to be imaged is placed on a cradle 120 in a generally cylindrical internal space (bore) of the magnet system 100, and is carried in and out by a transport means (not shown).
[0029]
The main magnetic field coil unit 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is substantially parallel to the direction of the body axis of the subject 1. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. In addition, you may comprise using not only a superconducting coil but a normal conduction coil.
[0030]
The gradient coil unit 106 generates three gradient magnetic fields for imparting gradients to the static magnetic field strength in three axes perpendicular to each other, that is, in the directions of a slice axis, a phase axis, and a frequency axis.
[0031]
The RF transmission coil 108 forms a high-frequency magnetic field for exciting nuclear magnetic resonance in the body of the subject 1 in the static magnetic field space. In addition, the RF receiving coil 110 is placed on the cradle 120 and is arranged together with the subject 1 in the center of the magnet system 100. The RF receiving coil 110 receives a magnetic resonance signal excited in the body of the subject 1 by the RF transmitting coil 108.
[0032]
The gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 supplies a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient drive unit 130 has three drive circuits (not shown) corresponding to the three gradient coils in the gradient coil unit 106.
[0033]
A transmission driver 140 is connected to the RF transmission coil 108. A drive signal is supplied from the transmission driver 140 to the RF transmission coil 108 to transmit an RF pulse. The RF transmission coil 108 forms an RF magnetic field from the transmitted RF pulse in the center of the magnet system 100, and Set to the excited state of nuclear magnetic resonance.
[0034]
The data collection unit 150 is connected to the RF reception coil 110. The data collection unit 150 captures a reception signal received by the RF reception coil 110 by sampling, and collects the received signal as digital data.
[0035]
The bias power supply unit 155 has a function of flowing a bias current on a signal line of a cable connecting the RF reception coil 110 and the data collection unit 150. The direction of the bias current is controlled by the scan controller 160, and the diode included in the RF receiving coil 110 is turned on and off, so that the magnetic coupling prevention circuit is on and off.
[0036]
The scan controller 160 is connected to the gradient driver 130, the transmission driver 140, and the data collection unit 150. The scan controller 160 controls the gradient driving unit 130 to the data collection unit 150 to perform photographing.
[0037]
The output side of the data collection unit 150 is connected to the data processing unit 170. The data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 has a memory (not shown). The memory stores a program for the data processing unit 170 and various data.
[0038]
The data processing section 170 is connected to the scan controller section 160. The data processing unit 170 is above the scan controller unit 160 and controls it. The function of the present apparatus is realized by the data processing unit 170 executing a program stored in the memory.
[0039]
The data processing unit 170 stores the data collected by the data collection unit 150 in a memory. A data space is formed in the memory. This data space constitutes a two-dimensional Fourier space. The data processing unit 170 reconstructs an image of the subject 1 by performing two-dimensional inverse Fourier transform on the data in the two-dimensional Fourier space.
[0040]
The display section 180 and the operation section 190 are connected to the data processing section 170. The display unit 180 is configured by a graphic display or the like. The operation unit 190 is a pointing device (pointing device).
device).
[0041]
The display unit 180 displays the reconstructed image output from the data processing unit 170 and various information. The operation unit 190 is operated by a user, and inputs various commands and information to the data processing unit 170. The user operates the present apparatus interactively through the display unit 180 and the operation unit 190.
[0042]
Next, a specific configuration of the RF receiving coil 110 and peripheral devices will be described in detail with reference to FIG. FIG. 2 illustrates an electric circuit portion of the RF receiving coil 110 illustrated in FIG. The RF receiving coil 110 includes a receiving loop 200, a power supply unit 260, and a parallel resonance circuit 208 forming a magnetic coupling prevention circuit. The power supply unit 260 further includes a second parallel resonance circuit 202, a first parallel resonance circuit 201, a first capacitor (capacitor) 204, and a capacitor 206 that form a magnetic coupling prevention circuit.
[0043]
The receiving loop 200, which is an inductor, and the capacitors 204 to 207 constitute a resonance circuit having a resonance point at a magnetic resonance frequency, and receive a magnetic resonance signal excited by the subject 1. The first capacitor 204, the second capacitor 205, and the capacitor 206 constitute a power supply unit 260 of the RF receiving coil 110, and a λ / 2 cable 220 is connected to both ends of the first capacitor 204. Is done. Here, the capacitances of the first capacitor 204, the second capacitor 205, and the capacitor 206 are based on the impedance matching between the λ / 2 cable 220 and the RF receiving coil 110 and the stabilization of the potential by dividing the capacitance. Is determined.
[0044]
The RF signal received by the RF receiving coil 110 is sent to the λ / 2 cable 220 via the impedance-matched power supply unit. The λ / 2 cable 220 is a cable having a half wavelength length of the received RF signal. The data collection unit 150 is connected to the output end of the λ / 2 cable 220. The data collection unit 150 performs amplification, detection, and the like of the RF signal input to the λ / 2 cable 220.
[0045]
A bias power supply 155 is connected to the signal line of the λ / 2 cable 220. The bias power supply 155 includes an inductor 242, a switch 241, and a current source 240. Here, the current source 240 has two outputs, a forward current and a reverse current, and is connected to the signal line of the λ / 2 cable 220 after being selected by the switch 241. The selection of the switch 241 is switched according to an instruction from the scan controller unit 160 in accordance with transmission or reception of an RF signal. In addition, an inductor 242 is arranged at this connection part, and prevents an RF signal from flowing between the signal line of the λ / 2 cable 220 and the bias power supply part 155.
[0046]
The parallel resonance circuit 208 includes a capacitor 207, an inductor 211, and a cross diode 212. The capacitor 207 and the inductor 211 form a parallel resonance circuit having a resonance point at a magnetic resonance frequency. Here, the cross diode 212 has a role of a switch, is turned on at the time of RF transmission, and serves as a magnetic coupling prevention circuit with the parallel resonance circuit 208 having a high impedance. At the time of RF reception, the cross diode 212 is turned off, and the parallel resonance circuit 208 operates as a simple capacitor 207.
[0047]
Further, a first parallel resonance circuit 201 is connected in parallel to the first capacitor 204 of the RF receiving coil 110. The first parallel resonance circuit 201 also has a resonance point at the magnetic resonance frequency, has a high impedance during transmission and reception, and has a role of a filter that does not pass an RF signal. On the other hand, the first parallel resonance circuit 201 is turned on by a inductor for a DC electric signal.
[0048]
The second capacitor 205 of the RF receiving coil 110 includes a second parallel resonance circuit 202 serving as a magnetic coupling prevention circuit. The second parallel resonance circuit 202 includes a second capacitor 205, an inductor 210, and a diode 209. Here, the second capacitor 205 and the inductor 210 constitute a parallel resonance circuit having a resonance point at a magnetic resonance frequency. In addition, the second parallel resonance circuit 202 sets the parallel resonance circuit to a high impedance state when the diode 209 serving as the switching means is in an on state, and serves as a magnetic coupling prevention circuit. When the diode 209 is in an off state, the second parallel resonance circuit 202 merely operates. Operates as the second capacitor 205.
[0049]
The turning on / off of the diode 209 serving as the switching means is controlled by the forward current or the reverse current of the current source 240 input through the first parallel resonance circuit 201. In the case of a forward current, the diode 209 is turned on, and in the case of a reverse current, the diode 209 is turned off.
[0050]
Next, the operation of the RF receiving coil 110 will be described. This operation is divided into transmitting an RF signal and receiving an RF signal. First, transmission of an RF signal will be described.
[0051]
When transmitting the RF signal, the switch 241 of the current source 240 selects the forward current according to an instruction from the scan controller unit 160. As a result, the diode 209 is turned on, and the second parallel resonance circuit becomes a high impedance state as a resonance circuit. Further, the cross diode 212 is turned on by the RF signal input to the reception loop 200 in the parallel resonance circuit 208, and the resonance circuit becomes a high impedance state.
[0052]
FIG. 3 shows an equivalent circuit of the reception loop 200 at the time of RF transmission. In the receiving loop 200, the entire loop is in a high impedance state, and the mutual induction coefficient of the magnetic field with the RF transmitting coil 108 is substantially zero. However, since the second parallel resonance circuit 202 and the parallel resonance circuit 208 have a high but finite impedance, a slight current is induced in the reception loop 200.
[0053]
When the induced current is i, the heat generation amount P of the reception loop 200 is
P = ri ²
Is proportional to Here, r is the total resistance value of the receiving loop 200. Assuming that the resistance value of the second parallel resonance circuit 202 at resonance is r1 and the resistance value of the parallel resonance circuit 208 at resonance is r2, the total resistance value r is approximately r = r1 + r2.
It becomes.
[0054]
The impedance r1 of the second parallel resonance circuit 202 at the time of resonance substantially includes a resistance component.
r1 = L / RC
Is represented by Here, L is the inductance of the inductor 210, C is the capacitance value of the second capacitor, and R is the resistance value including the winding resistance of the inductor and the on-resistance value of the diode 209. The same relational expression holds true for the parallel resonance circuit 208 as well.
[0055]
Here, by setting the values of the second capacitor 205 and the capacitor 207 of the second parallel resonance circuit 202 and the parallel resonance circuit 208 to be substantially the same, the inductor 210 and the inductor 211 can be also substantially matched from the resonance condition. . In addition, since the on-resistances of the diode 209 and the cross diode 212 are substantially the same,
r1 = r2
It becomes. As a result, the heat value P1 of the second parallel resonance circuit 202 and the heat value P2 of the parallel resonance circuit 208 are:
P1 ≒ P2
, And generate substantially even heat.
[0056]
In the conventional example, an inductor is provided at the position of the first parallel resonance circuit 201, and forms a second parallel resonance circuit together with the first capacitor 204. Then, the input impedance of the data collection unit 150 influences via the λ / 2 cable 220 in parallel with the resistance R of the resonance circuit, and a decrease in r1 occurs. As a result,
r1 <r2
And P1 <P2
Thus, the heat generated in the second parallel resonance circuit and the parallel resonance circuit 208 in the reception loop 200 was unavoidably non-uniform.
[0057]
When receiving the RF signal, the switch 241 of the current source 240 selects the reverse current according to an instruction from the scan controller unit 160. As a result, the diode 209 is turned off, and the second parallel resonance circuit operates only as the second capacitor 205. Further, since the parallel resonance circuit 208 also has no RF transmission signal input to the reception loop 200, the cross diode 212 is turned off, and operates as a simple capacitor 207.
[0058]
The reception loop 200 forms a resonance circuit together with the capacitors 204 to 207, receives an RF signal from the subject 1, and transmits the RF signal to the data collection unit 150 via the λ / 2 cable 220.
[0059]
As described above, in the first embodiment, the first parallel resonance circuit 201 is provided in the first capacitor 206 located at the power supply unit of the reception loop 200, and the second parallel resonance circuit 201 is provided by the adjacent second capacitor 205. Since the resonance circuit 202 is configured to be turned on and off by the diode 209 via the first parallel resonance circuit 201, the impedance of the second parallel resonance circuit 202 at the time of resonance is formed. Can be made substantially equal to the parallel resonance circuit 208, and the heat generated during RF transmission can be made equal, so that the RF receiving coil 110 can generate heat evenly.
[0060]
In the present embodiment, the main magnetic field coil unit 102 forms a horizontal static magnetic field using a superconducting coil. However, the main magnetic field coil unit 102 generates a vertical static magnetic field using a permanent magnet or a superconducting coil. A magnetic field coil unit can also be used.
[0061]
In this embodiment, the RF receiving coil 110 uses a loop coil. Can be similarly used.
(Embodiment 2)
In the first embodiment, the λ / 2 cable 220 is directly connected to the power supply unit 260 of the RF receiving coil 110. However, the λ / 2 cable 220 may be connected via a balun (balanced unbalanced transformer). Therefore, in the second embodiment, a case where a λ / 4 cable is connected to the power supply unit via a balun will be described.
[0062]
FIG. 4 is a diagram illustrating a specific configuration of the power supply unit 430, the balun 440, the λ / 4 cable 420, the data collection unit 150, and the bias power supply unit 155 of the RF reception coil 410 according to the second embodiment. The balun 440 and the λ / 4 cable 420 correspond to the λ / 2 cable 220 in FIG. 2, and the other configuration is the same as that shown in FIG. 2. Detailed description is omitted.
[0063]
The balun 440 is connected between the first capacitor 204 and the λ / 4 cable 420. The balun 440 includes an inductor connected in series to the signal line and the ground line, and a capacitor cross-connecting these connection terminals. Here, the λ / 4 cable 420 is a cable having a length of １ ／ wavelength of the received RF signal, and the balun 440 delays the phase of the RF signal by λ / 4 wavelength. By connecting the 420 and the balun 440, the data collection unit 150 has the same electrical characteristics as the λ / 2 cable 220.
[0064]
In addition, the balun 440 has a high impedance with respect to the common mode current, which is a current component flowing in the same direction, in the signal line and the ground line of the λ / 4 cable 420. Common mode current resulting from the electrical coupling of
[0065]
As described above, in Embodiment 2, the power supply unit 430 connects the RF reception coil 110 and the data collection unit 150 via the balun 440 and the λ / 4 cable 420. It is possible to reduce the electrical coupling between the 410 and the external device, and to stabilize the electrical characteristics of the RF receiving coil 410.
[0066]
【The invention's effect】
As described above, according to the present invention, the power supply unit includes the first parallel resonance circuit of the RF signal in the first capacitor of the capacitive coupling unit, and the magnetic coupling prevention circuit includes the first capacitor. And the switching means turns on and off the magnetic coupling prevention circuit via the first parallel resonance circuit. Therefore, when the RF signal is transmitted, the first parallel resonance circuit becomes high. The impedance becomes an impedance, and the magnetic coupling prevention circuit does not cause an impedance change at the time of resonance via the power supply unit. Consequently, the impedance of the magnetic coupling prevention circuit in the power supply unit can be controlled, and uniform heat generation can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of a magnetic resonance imaging apparatus.
FIG. 2 is a diagram illustrating an RF receiving coil and peripheral devices thereof according to the first embodiment.
FIG. 3 is a diagram showing an equivalent circuit of the RF receiving coil according to the first embodiment.
FIG. 4 is a diagram illustrating an RF receiving coil according to a second embodiment;
[Explanation of symbols]
1 subject 100 magnet system 102 main magnetic field coil unit 106 gradient coil unit 108 transmission coil 110, 410 reception coil 120 cradle 130 gradient drive unit 140 transmission drive unit 150 data collection unit 155 bias power supply unit 160 scan controller unit 170 data processing unit 180 Display section 190 Operation section 200 Receiving loop 201 First parallel resonance circuit 202 Second parallel resonance circuit 204 First capacitor 205 Second capacitor 206, 207 Capacitor 208 Parallel resonance circuit 209 Diodes 210, 211, 242 Inductor 212 Cross Diode 220 Cable 240 Current source 241 Switch 260, 430 Feed unit 420 Cable 440 Balun

Claims (9)

An RF receiving coil including a magnetic coupling preventing circuit for preventing magnetic coupling with an RF transmitting coil in a power supply unit of capacitive coupling,
The power supply unit,
A first parallel resonant circuit for an RF signal on a first capacitor of the capacitive coupling;
A magnetic coupling prevention circuit in a second capacitor adjacent to the first capacitor;
Switching means for turning on and off the magnetic coupling prevention circuit via the first parallel resonance circuit;
An RF receiving coil comprising: The RF receiving coil according to claim 1, wherein the first parallel resonance circuit is connected in parallel to the first capacitor. The RF receiving coil according to claim 1, wherein the magnetic coupling prevention circuit includes a second parallel resonance circuit including the second capacitor and an inductor connected in parallel to the second capacitor. 4. The switching device according to claim 2, wherein the switching unit turns on and off the second parallel resonance circuit and simultaneously turns on and off a parallel connection between the first parallel resonance circuit and the first capacitor. 5. RF receiving coil. 4. The RF receiving coil according to claim 1, wherein the switching unit is turned on and off by a diode. The RF receiving coil according to claim 5, wherein the switching unit includes a bias power supply for turning on and off the diode on a power supply line connected to the power supply unit. The RF receiving coil according to claim 6, wherein the bias power supply includes a switch that switches a direction of an output current. The RF receiving coil according to claim 1, wherein the power supply unit includes a balun in the first capacitor. Means for forming a static magnetic field,
Gradient magnetic field forming means for forming a gradient magnetic field,
An RF transmission coil for transmitting a high-frequency magnetic field to the subject in the static magnetic field,
RF receiving coil for receiving a magnetic resonance signal from the subject,
Control means for controlling the gradient magnetic field forming means, the RF transmission coil and the RF reception coil,
A magnetic resonance imaging apparatus comprising:
The RF reception coil has a magnetic coupling prevention circuit for preventing magnetic coupling with the RF transmission coil in a power supply unit of capacitive coupling,
The power supply unit includes a first parallel resonance circuit of an RF signal in a first capacitor of the capacitive coupling, a magnetic coupling prevention circuit in a second capacitor adjacent to the first capacitor, and a first capacitor. Switching means for turning on and off the magnetic coupling prevention circuit via a parallel resonance circuit;
An RF receiving coil comprising:

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