Magnetic resonance imaging device

Abstract

To provide a magnetic resonance imaging device capable of saving power of the drive of a decoupling circuit and detecting a failure.SOLUTION: A magnetic resonance imaging device includes: a plurality of decoupling circuits 210 being the plurality of decoupling circuits 210 which are respectively connected to a plurality of receiver coils, and have a field effect transistors (FETs) 1 and 2 as switches of switching each receiver coil between a resonance state and a detuned state; and an FET switch control unit 242 which applies a drive voltage to gates (G) of the FET 1 and the FET 2 to control ON / OFF. The magnetic resonance imaging device includes a first detection circuit 220A and a second detection circuit 220B which supply the current to the FET 1 and the FET 2 from a reference voltage source, detects whether the current has flowed to the FET 1 and / or the FET 2 via the first detection circuit 220A and / or the second detection circuit 220B, and determines whether the FET 1 and / or the FET 2 are normal or abnormal on the basis of the detection result and the state of the drive voltage applied to the gates (G) of the FET 1 and the FET 2.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a decoupling circuit that switches a receiving coil between a resonant state and a detuned state. [Background technology]

[0002] Conventionally, a decoupling circuit has been proposed that uses a current-driven PIN diode as a changeover switch (Patent Document 1).

[0003] However, decoupling circuits using PIN diodes have a problem in that the power required increases with the recent trend toward multi-channel receiving coils.

[0004] In response to this, Patent Document 2 proposes a decoupling circuit (also called a "detune circuit") that uses a voltage-driven field effect transistor (FET) as a low-loss switch. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-68008 A [Patent Document 2] Special Publication No. 2017-509413 Summary of the Invention [Problem to be solved by the invention]

[0006] The decoupling circuit described in Patent Document 2 is capable of saving power by using a voltage-driven FET, but does not take into consideration measures to be taken in the event of a breakdown, such as a break or short circuit, related to the FET.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a magnetic resonance imaging apparatus capable of reducing power consumption for driving a decoupling circuit and detecting a failure. [Means for solving the problem]

[0008] The invention according to a first aspect is a magnetic resonance imaging apparatus including a plurality of receiving coils each having a plurality of coils and adjusted to resonate at a specific frequency and receiving a nuclear magnetic resonance signal from a subject, a plurality of decoupling circuits each having a field effect transistor connected to the plurality of receiving coils, the plurality of decoupling circuits switching each receiving coil to a resonant state or a detuned state depending on a driving voltage applied to the gate of the field effect transistor, and a control unit controlling the driving voltage applied to the gate of the field effect transistor of the plurality of decoupling circuits, the magnetic resonance imaging apparatus including: a detection circuit for passing a current from a reference voltage source to the field effect transistor, the detection unit detecting whether or not a current has passed through the field effect transistor via the detection circuit; and a judgment unit for judging whether the field effect transistor is normal or abnormal based on the state of the driving voltage applied to the gate of the field effect transistor and the detection result of the detection unit.

[0009] According to the first aspect of the present invention, a field effect transistor that is turned on / off by a drive voltage applied to the gate is used as a changeover switch of the decoupling circuit, so that the power consumption of the decoupling circuit can be reduced. Also, a detection circuit is provided for passing a current from a reference voltage source to the field effect transistor, and whether or not a current has flowed to the field effect transistor is detected via the detection circuit, and the normality or abnormality of the field effect transistor can be determined based on the detection result and the state of the drive voltage applied to the gate of the field effect transistor. That is, a fault such as a break or short circuit related to the field effect transistor can be properly determined.

[0010] A magnetic resonance imaging apparatus according to a second aspect of the present invention is preferably such that, in the first aspect, the detection circuit includes a resistor for current detection, and the detection unit detects whether or not a current has flowed through the field effect transistor based on the potential difference across the resistor.

[0011] A magnetic resonance imaging apparatus according to a third aspect of the present invention is the magnetic resonance imaging apparatus of the second aspect, wherein the detection circuit preferably includes an inductor.

[0012] In the magnetic resonance imaging apparatus according to a fourth aspect of the present invention, in any one of the first to third aspects, it is preferable that one end of the detection circuit is connected to a reference voltage source and the other end of the detection circuit is connected to a drain of the field effect transistor.

[0013] A magnetic resonance imaging apparatus according to a fifth aspect of the present invention is preferably configured in any one of the first to fourth aspects, wherein the detection circuit is provided between the source of the field effect transistor and ground.

[0014] A magnetic resonance imaging apparatus according to a sixth aspect of the present invention, in any of the first to fifth aspects, preferably comprises a field effect transistor of the decoupling circuit comprising a first field effect transistor and a second field effect transistor whose sources are connected to each other, and the detection unit comprises a first detection unit having a first detection circuit for flowing a current from a reference voltage source to the first field effect transistor and detecting whether or not a current has flowed to the first field effect transistor via the first detection circuit, and a second detection unit having a second detection circuit for flowing a current from the reference voltage source to the second field effect transistor and detecting whether or not a current has flowed to the second field effect transistor via the second detection circuit.

[0015] In the magnetic resonance imaging apparatus according to the seventh aspect of the present invention, in the sixth aspect, it is preferable that the judgment unit judges whether at least one of the first field effect transistor and the second field effect transistor is normal or abnormal based on the state of the driving voltage applied to the gate of the first field effect transistor and the gate of the second field effect transistor, the detection result by the first detection unit, and the detection result by the second detection unit.

[0016] In the magnetic resonance imaging apparatus according to an eighth aspect of the present invention, in any one of the first to seventh aspects, when the driving voltage is changed to switch the field effect transistor from an OFF state to an ON state and when the field effect transistor is switched from an ON state to an OFF state, it is preferable that the determination unit suspends determination of normality or abnormality of the field effect transistor for at least a certain period from the time point when the driving voltage is changed, in order to prevent erroneous determination due to a time lag between the timing when the driving voltage changes and the timing when the detection result of the detection unit changes.

[0017] In the magnetic resonance imaging apparatus according to a ninth aspect of the present invention, in any one of the first to eighth aspects, a Zener diode is preferably provided on the gate side of the field effect transistor to prevent application of an abnormal voltage to the gate of the field effect transistor in order to prevent failure of the field effect transistor (failure due to application of an abnormal voltage to the gate).

[0018] A magnetic resonance imaging apparatus according to a tenth aspect of the present invention is any one of the first to ninth aspects, further comprising a judgment receiving unit for receiving judgment results of the judgment units provided corresponding to each of the plurality of decoupling circuits, and the judgment receiving unit is preferably connected in parallel to the plurality of judgment units and acquires judgment results from each of the plurality of judgment units. This makes it possible to acquire judgment results indicating the presence or absence of a failure in the field effect transistor for each decoupling circuit corresponding to each of the multi-channel receiving coils, and if the field effect transistor is faulty, to identify the location of the failure.

[0019] An eleventh aspect of the present invention relates to a magnetic resonance imaging apparatus according to the tenth aspect, wherein the determination receiving section preferably adds a unique address for each determination section to the received plurality of determination results.

[0020] A magnetic resonance imaging apparatus according to a twelfth aspect of the present invention is the tenth aspect, wherein each of the plurality of determination units has a unique address, and each determination unit transmits a determination result in association with the address to the determination receiving unit.

[0021] A magnetic resonance imaging apparatus according to a thirteenth aspect of the present invention, in any one of the first to ninth aspects, preferably includes a judgment receiving unit that receives judgment results from a plurality of judgment units provided corresponding to the plurality of decoupling circuits, the plurality of judgment units being connected in series, the plurality of judgment units being numbered 1 to n, and the last connected judgment unit being the nth judgment unit, the nth judgment unit transmits its own judgment result to the (n-1)th judgment unit, the (n-1)th judgment unit concatenates the judgment result received from the nth judgment unit with its own judgment result, and transmits the concatenated judgment result to the (n-2)th judgment unit, and by repeating this, the first judgment unit transmits a judgment result in which the judgment results of the plurality of judgment units are sequentially concatenated to the judgment receiving unit. This makes it possible to reduce the number of signal cables that return the judgment results of each judgment unit to the judgment receiving unit.

[0022] A magnetic resonance imaging apparatus according to a fourteenth aspect of the present invention is the thirteenth aspect, wherein each of the plurality of determination units has a unique address, and when the determination results are linked, the determination results are linked together with their own addresses. Effect of the Invention

[0023] According to the present invention, a field effect transistor that is turned on / off by a drive voltage applied to the gate is used as a change-over switch for the decoupling circuit, thereby making it possible to reduce the power consumption of the decoupling circuit. Furthermore, by providing a detection circuit for passing a current from a reference voltage source to the field effect transistor, it is possible to determine whether the field effect transistor is normal or abnormal, and to properly determine faults such as open circuit and short circuit related to the field effect transistor. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a perspective view showing the appearance of a magnetic resonance imaging apparatus (MRI apparatus) according to the present invention. [Diagram 2] FIG. 2 is a diagram showing a schematic internal configuration of the MRI apparatus shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram showing the configuration of the main part of the receive coil device. [Figure 4] FIG. 4 is a circuit diagram showing an embodiment of a decoupling circuit according to the present invention. [Diagram 5] FIG. 5 is a diagram showing an embodiment of a detection section and a determination section (error determination circuit) provided for each decoupling circuit. [Figure 6] FIG. 6 is a truth table showing the relationship between the T-ON signal A, the detection signal B of the current I1, the detection signal C of the current I2, and the error detection signal D output from the error determination circuit. [Figure 7] 7(A) to 7(D) are timing charts showing the T-ON signal A, the detection signals B and C, and the error detection signal D shown in FIG. 5, respectively. [Figure 8] FIG. 8 is a block diagram showing a first embodiment of a transmission / reception unit for transmitting and receiving an error determination result. [Figure 9] FIG. 9 is a block diagram showing a second embodiment of the transmission and reception unit for the error determination result. [Figure 10] FIG. 10 is a diagram showing an example of transmission data such as a determination result transmitted from each determination unit shown in FIG. [Figure 11]FIG. 11 is a block diagram showing a third embodiment of the transmission and reception unit for the error determination result. [Figure 12] FIG. 12 is a diagram showing an example of transmission data of the determination result transmitted from a determination unit connected to the determination receiving unit to the determination receiving unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, preferred embodiments of a magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings.

[0026] [External appearance of MRI device] FIG. 1 is a perspective view showing the appearance of a magnetic resonance imaging apparatus according to the present invention.

[0027] The magnetic resonance imaging apparatus (MRI apparatus) 100 shown in FIG. 1 includes a gantry 110 and a bed 130 having a table top 130A arranged on the front side of a bore 120, which is a cylindrical imaging space provided in the gantry 110.

[0028] [Internal structure of MRI device] FIG. 2 is a diagram showing a schematic internal configuration of the MRI apparatus shown in FIG.

[0029] As shown in FIG. 2, the MRI apparatus 100 includes a static magnetic field generating magnet 104 that generates a uniform static magnetic field in an imaging space in which a subject 102 is placed, a gradient magnetic field coil 106 that generates a gradient magnetic field in the imaging space, an RF (Radio Frequency) coil (transmitting coil) 108 that generates a high-frequency magnetic field that generates a nuclear magnetic resonance signal (NMR (Nuclear Magnetic Resonance) signal) (NMR signal) in the atomic nuclei of atoms that constitute the tissue of the subject 102, and a receiving coil device 200 that detects the NMR signal generated from the subject 102.

[0030] As shown in Figures 1 and 2, a subject 102 lying on his / her back on a top plate 130A of a bed 130 is moved to the bore 120 so that the examination area of ​​the subject 102 is positioned at the center of the static magnetic field within the bore 120 by moving the top plate 130A into the bore 120.

[0031] The sequencer 118 sends commands to the high frequency magnetic field generator 112 and the gradient magnetic field power supply 116 according to an imaging sequence (pulse sequence), causing them to generate a high frequency magnetic field and a gradient magnetic field, respectively. The generated high frequency magnetic field is applied to the subject 102 as a pulsed high frequency magnetic field (RF pulse) through the transmission coil 108. The NMR signal generated from the subject 102 is received by the receiving coil device 200 and detected by the receiver 114.

[0032] The gradient magnetic field coil 106 is composed of gradient magnetic field coils in three directions, X, Y, and Z, and generates gradient magnetic fields in response to signals from a gradient magnetic field power supply 116 .

[0033] The nuclear magnetic resonance frequency (detection reference frequency f0) used as the detection reference in the receiver 114 is set by the sequencer 118. The sequencer 118 controls each part so that it operates at pre-programmed timing and intensity. Among the programs, those that particularly describe the timing and intensity of the RF pulse, gradient magnetic field, and signal reception are called a pulse sequence.

[0034] There are various known pulse sequences depending on the purpose, but a detailed description thereof will be omitted here.

[0035] The control unit 140 controls the operation of the MRI apparatus 100 via the sequencer 118, receives the signal detected by the receiver 114, and performs various signal processing such as image reconstruction. The receiver 114 performs quadrature phase detection of the echo signal (NMR signal), which is an analog wave, using a set detection reference frequency f0, converts it into raw data, and transmits it to the control unit 140. This raw data is also called the echo signal or measurement data.

[0036] The control unit 140 can be configured using a computer. The computer applied to the control unit 140 may be a personal computer or a workstation.

[0037] The control unit 140 receives various instruction inputs from the operation unit 150, and controls each part of the MRI apparatus 100 in an integrated manner. It also performs processes such as converting the echo signals in the spatial frequency domain received via the sequencer 118 into images in real space by inverse Fourier transform, thereby generating an MRI image.

[0038] The operation unit 150 includes a mouse, a keyboard, and the like, and functions as a part of a GUI (Graphical User Interface) that receives input from an operator using a display operation window on a display (not shown).

[0039] That is, the operation unit 150 and the display function as a GUI for the operator to start and stop (pause) the MRI apparatus 100, select a pulse sequence, and input imaging conditions, processing conditions, and the like.

[0040] [Receiving coil device] FIG. 3 is a schematic diagram showing the configuration of the main part of the receive coil device.

[0041] The receive coil device 200 of this embodiment is flexible, thin, and lightweight, as shown in FIG. 2, and capable of covering a wide imaging range, and is capable of imaging various regions to be examined.

[0042] As shown in FIG. 3, the receiving coil device 200 includes a plurality of loop-shaped coils (receiving coils) 200-1, 200-2, ..., 200-n that function as antennas for receiving nuclear magnetic resonance signals (NMR signals), and decoupling circuits 210-1, 210-2, ..., 210-n are provided corresponding to the receiving coils 200-1, 200-2, ..., 200-n, respectively.

[0043] As described below, each of the multiple decoupling circuits 210-1, 210-2, ..., 210-n is provided with a voltage-driven field effect transistor (FET), and the FET in each decoupling circuit is ON / OFF controlled by a drive voltage supplied from a decoupling power supply 202.

[0044] [Decoupling circuit] FIG. 4 is a circuit diagram showing an embodiment of a decoupling circuit according to the present invention.

[0045] The decoupling circuit 210 shown in FIG. 4 is one of the multiple decoupling circuits 210-1, 210-2, . . . , 210-n shown in FIG.

[0046] In FIG. 4, capacitors C1, C2, and C3 are connected in series between two terminals PD1 and PD2, and a loop-shaped coil (the receiving coil shown in FIG. 3) functioning as an antenna (not shown) is connected to the other end.

[0047] The receiver coil is tuned to resonate at a specific frequency and receives the nuclear magnetic resonance (NMR) signal from the subject. The specific frequency is determined by the nuclei (usually hydrogen nuclei) of the biological tissue to be observed and the magnetic field strength.

[0048] The transmitting coil 108 shown in FIG. 2 applies an RF pulse to the subject 102, generating an NMR signal in the atomic nuclei of the atoms that make up the biological tissue of the subject 102. However, if the receiving coil is placed in a resonant state while the RF pulse is being applied, the highly sensitive receiving coil may receive an excessively large RF magnetic field, which may damage the peripheral circuits related to the receiving coil.

[0049] The decoupling circuit 210 is a circuit for sufficiently decoupling (detuning) the receiving coil from the transmitting coil 108 at least during the period in which an RF pulse is transmitted from the transmitting coil 108, switching the receiving coil to a detuned state (so as not to resonate), and switching the receiving coil to a resonant state when receiving an NMR signal generated from the biological tissue of the subject 102 after the transmission of the RF pulse.

[0050] In the decoupling circuit 210 shown in FIG. 4, a first circuit 211 having a capacitor C4, a diode D1, a capacitor C5 and an inductor L1, and a second circuit 212 having a capacitor C6, a first field effect transistor (FET1), a second field effect transistor (FET2) and a capacitor C7 are connected in parallel to the capacitor C2 of the receiving coil.

[0051] The decoupling circuit 210 switches the receiving coil to a detuned state or a resonant state by controlling ON / OFF of the FET1 and FET2.

[0052] That is, when FET1 and FET2 are turned ON, the second circuit 212 including the capacitors C6 and C7 is closed, and the second circuit 212 is connected in parallel to the diode D1 of the first circuit 211. As a result, the receiving coil including the first circuit 211 and the second circuit 212 is sufficiently detuned with respect to the frequency of the RF pulse.

[0053] On the other hand, when FET1 and FET2 are turned off, the second circuit 212 including the capacitors C6 and C7 is opened, and only the first circuit 211 is connected in parallel to the capacitor C2 of the receiving coil. As a result, the receiving coil including the second circuit 212 is switched to a resonant state, and becomes able to receive the NMR signal generated from the biological tissue.

[0054] The NMR signal received by the receiving coil switched to the resonant state is acquired from terminals PD3 and PD4 on both ends of the capacitor C1 via a preamplifier (not shown).

[0055] <ON / OFF control of FET that opens and closes the second circuit> Next, the ON / OFF control of FET1 and FET2 that open and close the second circuit 212 will be described.

[0056] In FIG. 4, a FET switch control unit 242 functioning as a control unit for FET1 and FET2 outputs a drive voltage (voltage signal T-ON) for controlling the ON / OFF of FET1 and FET2 from a logical negation circuit (NOT circuit) 243 in synchronization with a command (a command to generate an RF pulse from the transmitting coil 108) transmitted from the sequencer 118 shown in FIG. 2 to the high-frequency magnetic field generator 112.

[0057] The voltage signal T-ON when turning on FET1 and FET2 is an H level signal (e.g., 5V), and when turning off FET1 and FET2, is an L level signal (e.g., 0V). The voltage signal T-ON is output as an H level signal during the generation period of an RF pulse, and is output as an L level signal outside the generation period of an RF pulse. In this example, the H level signal and the L level signal of the voltage signal T-ON are also referred to as "1" and "0", respectively.

[0058] A voltage signal T-ON output from the FET switch control section 242 is applied to the gates (G) of FET1 and FET2 via an inductor L2 and a resistor R1. The sources (S) of FET1 and FET2 are connected to ground via an inductor L3, a resistor R3, and an inductor L4. A resistor R2 is disposed between the resistor R1 and the gates (G) of FET1 and FET2. The resistors R1 and R2 have a resistance value sufficiently larger than that of the resistor R3, and reduce the current flowing to ground.

[0059] In this example, when the voltage signal T-ON is at H level, a gate voltage exceeding the threshold voltage is applied between the gate (G) and source (S) of FET1 and FET2, and the drain (D) and source (S) are turned ON (FET1 and FET2 are turned ON). When the voltage signal T-ON is at L level, the gate voltage applied to the gate (G) of FET1 and FET2 is OV, and the drain (D) and source (S) are turned OFF (FET1 and FET2 are turned OFF).

[0060] In this example, a Zener diode ZD is provided between the gate (G) side of FET1 and FET2 and ground to prevent application of abnormal voltage to the gate (G) of FET1 and FET2. In other words, an abnormal voltage exceeding the Zener voltage of the Zener diode ZD is prevented from being applied to the gate (G) of FET1 and FET2.

[0061] As described above, the decoupling circuit 210 controls the ON / OFF of FET1 and FET2 by the voltage signal T-ON. Therefore, it is possible to reduce power consumption in the drive control of the decoupling circuits 210-1 to 210-n for each of the multi-channel receiving coils, as compared with a decoupling circuit that uses a current-driven PIN diode, for example.

[0062] <Error detection in decoupling circuits> Next, error detection in the decoupling circuit 210 will be described.

[0063] In FIG. 4, reference numerals 220A and 220 are circuit diagrams showing examples of error detection circuits (first detection circuit, second detection circuit) for detecting faults (errors) such as breaks and short circuits relating to FET1 and FET2, respectively.

[0064] The first detection circuit 220A is a circuit for passing a current from a reference voltage source to the FET 1, and is configured by connecting an inductor L5, a resistor R4, a resistor R5 for current detection, and an inductor L6 in series, with a reference voltage Vref being applied to one end of the circuit from the reference voltage source, and the other end being connected to the drain (D) of the FET 1. The reference voltage Vref can be, for example, 15V.

[0065] When FET1 is in the ON state, a current I 1 However, the resistor R4 has a resistance value that is sufficiently larger than the resistance value of the current detection resistor 5 and the DC resistance of the inductor L6, so that the current I 1 In other words, the power required for error detection is reduced.

[0066] The second detection circuit 220B is a circuit for passing a current from a reference voltage source to FET2, and includes an inductor L7, a resistor R6, a resistor R7 for current detection, and an inductor L8 connected in series. A reference voltage Vref is applied to one end of the circuit from the reference voltage source, and the other end is connected to the drain (D) of FET2.

[0067] The second detection circuit 220B has the same circuit configuration as the first detection circuit 220A, and when FET2 is in the ON state, a current I 2 flows.

[0068] When FET1 and FET2 are in the ON state, the current I 1 , I 2 By reducing the current value, it is possible to reduce the power required for error detection in FET1 and FET2.

[0069] The first detection circuit 220A detects the voltage V 1+ , V 1- Similarly, the second detection circuit 220B is provided with a terminal for acquiring the voltage V across the resistor R7. 2+ , V 2-A terminal is provided for acquiring the signal.

[0070] <Detection section and determination section> Next, we will explain the detection unit that detects whether or not current has flowed through FET1 and FET2 from the first detection circuit 220A and the second detection circuit 220B shown in Figure 4, respectively, and the judgment unit that judges whether FET1 and FET2 are normal or abnormal based on the detection results of the detection unit.

[0071] FIG. 5 is a diagram showing an embodiment of a detection section and a determination section (error determination circuit) provided for each decoupling circuit.

[0072] In FIG. 5, the first detection unit 226 detects a current I 1 The second detection circuit 227 is a detection unit that detects whether a current I 2 This is a detection unit that detects whether or not a flow has occurred.

[0073] The first detection section 226 is composed of a differential amplifier 221 and a comparator 223 .

[0074] The positive and negative inputs of the differential amplifier 221 are connected to the voltage V across the resistor R5 of the first detection circuit 220A, respectively. 1+ , V 1- are applied, and the differential amplifier 221 divides these voltages V 1+ , V 1- The difference between these two is amplified and output to the positive input of the comparator 223. Here, the current I 1 When current flows, the voltage V 1+ , V 1- Between them, there is a current I 1 and the potential difference (I 1 ×R) is generated, and a detection voltage according to the potential difference is output from differential amplifier 221 to the positive input of comparator 223.

[0075] The negative input of the comparator 223 is connected to the first detection circuit 220A and the FET1. 1The threshold voltage V for determining whether current is flowing or not th is applied, and the comparator 223 detects whether the detection voltage is greater than or equal to the threshold voltage V th If it exceeds the current I 1 On the other hand, the comparator 223 outputs a detection signal B (H level signal (“1”)) indicating that the detection voltage has flowed. th In the following case, the current I 1 That is, the comparator 223 outputs a detection signal B (L level signal (“0”)) indicating that the current I 1 The detector outputs a detection signal B indicating whether or not a current has flowed.

[0076] Similarly, the second detection unit 227 is composed of a differential amplifier 222 and a comparator 224. The functions of the differential amplifier 222 and the comparator 224 of the second detection unit 227 are common to the differential amplifier 221 and the comparator 223 of the first detection unit 226, and therefore detailed description thereof will be omitted.

[0077] The comparator 224 of the second detection unit 227 outputs a current I 2 It outputs a detection signal C indicating whether or not a current has flowed.

[0078] The error determination circuit 225 is composed of two exclusive OR circuits (XOR circuits) 225A and 225B, and a logical OR circuit (OR circuit) 225C.

[0079] One input of each of the XOR circuits 225A and 225B is supplied with a T-ON signal A from a NOT circuit 245. The NOT circuit 245 is provided in the FET switch control section 242 shown in Fig. 4, and is provided in parallel with a NOT circuit 243 that outputs a voltage signal T-ON for controlling the ON / OFF of FET1 and FET2.

[0080] The T-ON signal A output from the NOT circuit 245 to the error determination circuit 225 is the same signal as the voltage signal T-ON output from the NOT circuit 243, and is a signal that is switched to an H level signal or an L level signal at the same timing. The reason why the NOT circuit 245 is provided separately from the NOT circuit 243 is to prevent the T-ON signal A output from the NOT circuit 245 from being affected by the decoupling circuit 210.

[0081] The other input of the XOR circuit 225A receives the current I 1 A detection signal B is added to the T-ON signal A, and the XOR circuit 225A outputs a determination result of H level or L level based on the T-ON signal A and the detection signal B. Here, the XOR circuit 225A outputs a determination result of L level ("0") when the FET1 of the decoupling circuit 210 is normal, and outputs a determination result of H level ("1") when an abnormality such as a break or short circuit occurs in the FET1.

[0082] Similarly, the other input of the XOR circuit 225B receives the current I 2 A detection signal C is added to the T-ON signal A, and the XOR circuit 225B outputs a determination result of H level or L level based on the T-ON signal A and the detection signal C. Here, the XOR circuit 225B outputs a determination result of L level ("0") when the FET2 of the decoupling circuit 210 is normal, and outputs a determination result of H level ("1") when an abnormality occurs in the FET2.

[0083] The OR circuit 225C takes the OR condition of the judgment results of the two XOR circuits 225A and 225B, and outputs an error detection signal D indicating whether the decoupling circuit 210 is normal or abnormal. The error detection signal D output from the OR circuit 225C is at L level ("0") when the decoupling circuit 210 is normal, and is at H level ("1") when the decoupling circuit 210 is abnormal.

[0084] FIG. 6 shows a T-ON signal A and a current I corresponding to the FET control signal input to the error determination circuit 225.1 The detection signal B and the current I 2 11 is a truth table showing the relationship between the detection signal C and the error detection signal D output from the error determination circuit 225.

[0085] As shown in FIG. 6, when the error detection signal D is “0”, the decoupling circuit 210 (FET1 and FET2) is normal, and when the error detection signal D is “1”, it indicates that an abnormality has occurred in the decoupling circuit 210 (at least one of FET1 and FET2).

[0086] 7(A) to 7(D) are timing charts showing the T-ON signal A, the detection signals B and C, and the error detection signal D shown in FIG. 5, respectively.

[0087] The example shown in FIG. 7 shows each signal when the decoupling circuit 210 (FET1 and FET2) is normal.

[0088] However, if there is a time lag between the timing of switching between L level and H level of the T-ON signal A, which is synchronized with the ON / OFF control of FET1 and FET2 shown in FIG. 7(A), and the timing of the L level and H level changes of the detection signals B and C outputted from the comparators 223 and 224, during that time, the error detection signal D becomes H level, which indicates that an abnormality has occurred in the decoupling circuit 210.

[0089] Therefore, when the voltage signal T-ON is changed to switch FET1 and FET2 from the OFF state to the ON state and from the ON state to the OFF state, it is preferable to suspend the determination of the normality or abnormality of FET1 and FET2 for at least a certain period from the time when the voltage signal T-ON changes. That is, it is preferable to mask (not employ) the error detection signal D output from the error determination circuit 225 during the time lag period between the timing of switching the T-ON signal A synchronized with the voltage signal T-ON and the timing of the changes in the detection signals B and C.

[0090] [Transmitter / receiver of error detection results] Next, a description will be given of a transmission / reception section of an error determination result detected by a determination section (a determination section including first detection section 226, second detection section 227, and error determination circuit 225) provided for each decoupling circuit shown in FIG.

[0091] <First embodiment of the transmission / reception unit for error determination result> FIG. 8 is a block diagram showing a first embodiment of a transmission / reception unit for transmitting and receiving an error determination result.

[0092] As shown in FIG. 8, a plurality of receiving coils 200-1, 200-2, ..., 200-n functioning as antennas are provided with corresponding decoupling circuits 210-1, 210-2, ..., 210-n, and further provided with judgment units 231-1, 231-2, ..., 231-n each including a first detection unit 226, a second detection unit 227 and an error judgment circuit 225 shown in FIG. 5 corresponding to the decoupling circuits 210-1, 210-2, ..., 210-n.

[0093] Each of the determination units 231-1, 231-2, ..., 231-n acquires a determination result (error detection signal D) of whether the decoupling circuits 210-1, 210-2, ..., 210-n (FET1 and FET2) are normal or abnormal, and functions as a transmission unit that transmits the determination result.

[0094] In addition, in FIG. 8, the detuning function control section 240 includes an FET switch control section 242 and a decision receiving section 244.

[0095] The FET switch control unit 242 outputs a voltage signal T-ON for controlling the ON / OFF of FET1 and FET2 to the decoupling circuits 210-1, 210-2, ..., 210-n in response to a command from the sequencer 118 as described above, and also outputs a T-ON signal A synchronized with the ON / OFF control of FET1 and FET2 to the determination units 231-1, 231-2, ..., 231-n.

[0096] The decision receiving unit 244 is connected in parallel to the multiple decision units 231-1, 231-2, ..., 231-n in a one-to-multiple relationship, and functions as a receiving unit that receives the decision results transmitted from each of the decision units 231-1, 231-2, ..., 231-n.

[0097] The decision receiving unit 244 adds a unique address for each decision unit (a unique address assigned to each decision unit) to the multiple decision results in accordance with a certain rule, and returns the results to the sequencer 118.

[0098] When the sequencer 118 or the control unit 140 (FIG. 2) downstream of the sequencer 118 receives a determination result indicating an abnormality in FET1 and / or FET2, it can detect in which of the multiple decoupling circuits 210-1, 210-2, ..., 210-n the abnormality has occurred, based on the address added to the determination result.

[0099] In addition, instead of the judgment receiving unit 244 adding an address to the detection result, each judgment unit 231-1, 231-2, ..., 231-n may be configured to associate its own judgment result with the address assigned to it when transmitting it (by adding the address assigned to it to its own judgment result).

[0100] The transmission of the judgment results, etc. is not limited to electrical transmission using an electric signal cable, but may be optical transmission using an optical signal cable, or may use wireless or other communication means.

[0101] <Second embodiment of the transmission / reception unit for error determination result> Fig. 9 is a block diagram showing a second embodiment of the transmission / reception unit of the error determination result. In the transmission / reception unit of the second embodiment shown in Fig. 9, parts common to the transmission / reception unit of the first embodiment shown in Fig. 8 are given the same reference numerals, and detailed description thereof will be omitted.

[0102] The transmitting / receiving section of the second embodiment shown in FIG. 9 differs from the transmitting / receiving section of the first embodiment in the method of communicating the error determination result.

[0103] That is, the plurality of determining units 232-1, 232-2, ..., 232-n provided corresponding to the plurality of decoupling circuits 210-1, 210-2, ..., 210-n, respectively, are connected in series.

[0104] Here, the multiple judgment units 232-1, 232-2, ..., 232-n are defined as the first to nth judgment units, with the first judgment unit 232-1 connected to the judgment receiving unit 244 and the last judgment unit 232-n connected in series being defined as the nth judgment unit.

[0105] The nth judgment unit 232-n transmits its own judgment result to the (n-1)th judgment unit 232-(n-1), and the (n-1)th judgment unit 232-(n-1) concatenates the judgment result of the nth judgment unit 232-n it received with its own judgment result and transmits the concatenated judgment result to the (n-2)th judgment unit 232-(n-2). By repeating this process, the first judgment unit 232-1 transmits a judgment result (transmission data) in which the judgment results of the multiple judgment units 232-1, 232-2, ..., 232-(n-1), ..., 232-n are sequentially concatenated to the judgment receiving unit 244.

[0106] According to the transmission and reception unit of the error determination result of the second embodiment, it is possible to reduce the number of signal cables compared to the first embodiment.

[0107] In addition, when each of the judgment units 232-1, 232-2, ..., 232-(n-1), ..., 232-n concatenates its own judgment results, it is preferable that the judgment units also concatenate the addresses assigned to themselves at the same time.

[0108] FIG. 10 is a diagram showing an example of transmission data such as a determination result transmitted from each determination unit shown in FIG.

[0109] As shown in Fig. 10, the nth determination unit 232-n transmits transmission data of its own address n + determination result (0) to the (n-1)th determination unit 232-(n-1). In Fig. 10, the determination result in the transmission data is 1-bit data that is "0" if normal and "1" if abnormal (error).

[0110] The (n-1)th judgment unit 232-(n-1) transmits to the (n-2)th judgment unit 232-(n-2) transmission data that combines its own address (n-1) + judgment result (0) with the address n + judgment result (0) received from the nth judgment unit 232-n.

[0111] By each judgment unit repeating the above process in sequence, the first judgment unit 231-1 can transmit transmission data indicating the judgment results along with the addresses of all judgment units 232-1, 232-2, ... 232-(n-1), ... , 232-n to the judgment receiving unit 244.

[0112] <Third embodiment of the transmission / reception unit for error determination result> Fig. 11 is a block diagram showing a third embodiment of the transmission / reception unit of the error determination result. In the transmission / reception unit of the third embodiment shown in Fig. 11, parts common to the transmission / reception unit of the second embodiment shown in Fig. 9 are given the same reference numerals, and detailed description thereof will be omitted.

[0113] The transceiver unit of the third embodiment shown in FIG. 11 differs from the transceiver unit of the second embodiment in that each decoupling circuit is provided with a plurality of detection units (switch units) and each detection unit is provided with an independent judgment unit.

[0114] That is, the receiving coil 200-1 is provided with a plurality (two) of switch units 210-1a, 210-1b of a decoupling circuit, and is provided with judgment units 233-1a, 233-1b that individually judge whether each of the switch units 210-1a, 210-1b is normal or abnormal. Similarly, the other receiving coils 200-2 to 200-n are provided with two switch units and a judgment unit.

[0115] As shown in FIG. 11, all of the judgment units 233-1a, 233-1b, 233-2a, 233-2b, ..., 233-na, 233-nb are connected to the judgment unit 233-a, and the judgment unit 233-a transmits transmission data to the judgment receiving unit 244 that is a concatenation of the judgment results of all the judgment units 233-1a, 233-1b, 233-2a, 233-2b, ..., 233-na, 233-nb.

[0116] FIG. 12 is a diagram showing an example of transmission data of the determination result transmitted from a determination unit connected to the determination receiving unit to the determination receiving unit.

[0117] As shown in FIG. 12, the judgment unit 233-1a connected to the judgment receiving unit 244 transmits to the judgment receiving unit 244 transmission data that is a concatenation of the judgment results with addresses of all the judgment units 233-1a, 233-1b, 233-2a, 233-2b, ..., 233-na, and 233-nb.

[0118] According to the third embodiment, as in the second embodiment, the number of signal cables used to transmit transmission data can be reduced, and when multiple switch units are provided in one receiving coil, the normal / abnormal judgment result can be transmitted to the judgment receiving unit 244 for each switch unit.

[0119] [others] In this embodiment, two FETs, FET1 and FET2, are provided in one decoupling circuit, but one FET may be used.

[0120] In addition, a current I flowing from the source (S) of FET1 and FET2 to the ground through a resistor R3 of the circuit section 220C between the source (S) of FET1 and FET2 and the ground, which is indicated by a dashed line in FIG. SHUNT It may be used as a resistor for current detection to detect the voltage V across resistor R3. 0+ , V 0- Based on the current I SHUNT may be detected, and thereby the normality or abnormality of FET1 and FET2 may be detected.

[0121] Furthermore, the current I SHUNT includes a current flowing through resistor R2, but the resistor R2 has a resistance value sufficiently large compared to resistor R3 so that the current can be ignored. SHUNT When the normality or abnormality of FET1 and FET2 is not to be determined by this, the circuit section 220C indicated by the dashed line may be omitted.

[0122] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0123] 100...MRI device 102...Subject 108…Transmitting coil 110…Gantry 120…Bore 130…Bed 200...Receiving coil device 210, 210-1 to 210-n... Decoupling circuit 220A…First detection circuit 220B...Second detection circuit

Claims

1. a plurality of receiving coils each having a plurality of coils and each being adjusted to resonate at a particular frequency and receiving a nuclear magnetic resonance signal from a subject; a plurality of decoupling circuits each having a field effect transistor connected to the plurality of receiving coils, the decoupling circuits switching each receiving coil to a resonant state or a detuned state in response to a drive voltage applied to a gate of the field effect transistor; a control unit for controlling the driving voltage applied to gates of field effect transistors of the plurality of decoupling circuits, a detection section having a detection circuit for causing a current to flow from a reference voltage source to the field effect transistor and detecting whether or not a current has flowed through the field effect transistor via the detection circuit; a determination unit that determines whether the field effect transistor is normal or abnormal based on a state of the drive voltage applied to a gate of the field effect transistor and a detection result of the detection unit; A magnetic resonance imaging apparatus comprising:

2. the detection circuit includes a resistor for current detection; the detection unit detects whether or not a current flows through the field effect transistor based on a potential difference between both ends of the resistor.

2. A magnetic resonance imaging apparatus according to claim 1.

3. the detection circuit includes an inductor; 3. A magnetic resonance imaging apparatus according to claim 2.

4. one end of the detection circuit is connected to the reference voltage source, and the other end of the detection circuit is connected to the drain of the field effect transistor; 4. A magnetic resonance imaging apparatus according to claim 1.

5. The detection circuit is provided between the source of the field effect transistor and ground.

4. A magnetic resonance imaging apparatus according to claim 1.

6. the field effect transistor of the decoupling circuit includes a first field effect transistor and a second field effect transistor whose sources are connected to each other; the detection unit includes a first detection circuit for causing a current to flow from the reference voltage source to the first field effect transistor, and a first detection unit for detecting whether or not a current has flowed through the first field effect transistor via the first detection circuit; and a second detection unit for causing a current to flow from the reference voltage source to the second field effect transistor, and a second detection unit for detecting whether or not a current has flowed through the second field effect transistor via the second detection circuit.

4. A magnetic resonance imaging apparatus according to claim 1.

7. the determination unit determines whether at least one of the first field effect transistor and the second field effect transistor is normal or abnormal based on a state of the drive voltage applied to the gate of the first field effect transistor and the gate of the second field effect transistor, a detection result by the first detection unit, and a detection result by the second detection unit.

7. A magnetic resonance imaging apparatus according to claim 6.

8. When the driving voltage is changed to switch the field effect transistor from an OFF state to an ON state and when the field effect transistor is switched from an ON state to an OFF state, the determination unit stops determining whether the field effect transistor is normal or abnormal for at least a certain period from the time point when the driving voltage is changed.

4. A magnetic resonance imaging apparatus according to claim 1.

9. a Zener diode is provided on the gate side of the field effect transistor to prevent application of an abnormal voltage to the gate of the field effect transistor; 4. A magnetic resonance imaging apparatus according to claim 1.

10. a determination receiving unit that receives a determination result of the determination unit provided corresponding to each of the plurality of decoupling circuits; the determination receiving unit is connected in parallel to the plurality of determination units and receives the determination results from each of the plurality of determination units; 4. A magnetic resonance imaging apparatus according to claim 1.

11. the determination receiving unit adds a unique address for each of the determination units to the received multiple determination results; 11. A magnetic resonance imaging apparatus according to claim 10.

12. Each of the plurality of determination units has a unique address, and each of the determination units transmits the determination result and the address to the determination receiving unit in association with each other.

11. A magnetic resonance imaging apparatus according to claim 10.

13. a determination receiving unit that receives determination results from a plurality of the determination units provided corresponding to the plurality of decoupling circuits, The plurality of determination units are connected in series, If the multiple judgment units are numbered 1 to n, and the last connected judgment unit is the nth judgment unit, the nth judgment unit transmits its own judgment result to the (n-1)th judgment unit, the (n-1)th judgment unit concatenates the judgment result of the nth judgment unit it received with its own judgment result, and transmits the concatenated judgment result to the (n-2)th judgment unit, and by repeating this process, the first judgment unit transmits the judgment result, in which the judgment results of the multiple judgment units are sequentially concatenated, to the judgment receiving unit.

4. A magnetic resonance imaging apparatus according to claim 1.

14. Each of the plurality of determination units has a unique address, and when the determination results are linked, the unique address is linked together with the address of the determination unit.

14. A magnetic resonance imaging apparatus according to claim 13.

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