Magnetic resonance imaging apparatus

Abstract

The present invention addresses the problem of providing a magnetic resonance imaging device capable of achieving power saving and failure detection of decoupling circuit driving. A magnetic resonance imaging device is provided with: a plurality of decoupling circuits (210) which are connected to a plurality of reception coils, respectively, and which have FET1 and FET2 as switching switches for switching the respective reception coils to a resonant state or a detuning state; and an FET switch control unit (242) that performs ON / OFF control by applying a drive voltage to the gates (G) of the FET1 and FET2. The magnetic resonance imaging apparatus includes a first detection circuit (220A) and a second detection circuit (220B) for flowing a current from a reference voltage source to the FET1 and the FET2, the first detection circuit (220A) and / or the second detection circuit (220B) detects whether or not the current flows through the FET1 and / or the FET2, and determines whether or not the FET1 and / or the FET2 is normal on the basis of the detection result and the state of the drive voltage applied to the gates (G) of the FET1 and the FET2.

Description

Technical Field

[0001] The present invention relates to a magnetic resonance imaging device, and in particular to a decoupling circuit for switching a receiving coil to a resonance state or a detuning state. Background Art

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

[0003] However, the decoupling circuit using the PIN diode has a problem that the required power increases as the number of channels of the receiving coil increases in recent years.

[0004] On the other hand, Patent Document 2 proposes a decoupling circuit (also referred to as a “detuning circuit”) using a voltage-driven field effect transistor (FET) as a low-loss switch.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-68008

[0006] Patent Document 2: Japanese Patent Application No. 2017-509413 Summary of the invention

[0007] The decoupling circuit described in Patent Document 2 can achieve power saving by using a voltage-driven FET, but does not take into account countermeasures when a failure such as disconnection or short circuit occurs in the FET.

[0008] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic resonance imaging apparatus capable of realizing power saving and failure detection in driving a decoupling circuit.

[0009] The invention involved in the first aspect is a magnetic resonance imaging device, which includes: a plurality of receiving coils, which have a plurality of coils and are adjusted to resonate at a specific frequency and receive nuclear magnetic resonance signals from a subject; a plurality of decoupling circuits, which are respectively connected to the plurality of receiving coils and have field effect transistors, and each receiving coil is switched to a resonant state or a detuned state according to a driving voltage applied to the gate of the field effect transistor; and a control unit, which controls the driving voltage applied to the gate of the field effect transistor of the plurality of decoupling circuits, the magnetic resonance imaging device including: a detection unit, which has a detection circuit for passing a current from a reference voltage source to the field effect transistor, and detects whether the current flows in the field effect transistor by the detection circuit; and a determination unit, which determines whether the field effect transistor is normal or abnormal according to the state of the driving voltage applied to the gate of the field effect transistor and the detection result of the detection unit.

[0010] According to the first embodiment of the present invention, as a switching switch of the decoupling circuit, a field effect transistor that is turned on / off by a driving voltage applied to the gate is used, so that power saving of the decoupling circuit drive can be achieved. In addition, a detection circuit for flowing current from a reference voltage source to the field effect transistor is provided, and the detection circuit detects whether the current flows in the field effect transistor. Based on the detection result and the state of the driving voltage applied to the gate of the field effect transistor, it is possible to determine whether the field effect transistor is normal or abnormal. That is, it is possible to accurately determine faults such as disconnection and short circuit related to the field effect transistor.

[0011] Preferably, in the magnetic resonance imaging apparatus according to the second aspect of the present invention, in the first aspect, the detection circuit includes a current detection resistor, and the detection unit detects whether the current flows in the field effect transistor based on a potential difference between both ends of the resistor.

[0012] Preferably, in the magnetic resonance imaging apparatus according to the third aspect of the present invention, in the second aspect, the detection circuit includes an inductor.

[0013] Preferably, in the magnetic resonance imaging apparatus according to the fourth aspect of the present invention, in the first to third aspects, 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.

[0014] Preferably, in the magnetic resonance imaging apparatus according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the detection circuit is provided between the source of the field effect transistor and the ground.

[0015] Preferably, in the magnetic resonance imaging apparatus involved in the sixth aspect of the present invention, in any one of the first to fifth aspects, the field effect transistor of the decoupling circuit is composed of a first field effect transistor and a second field effect transistor respectively connected to source electrodes, the detection unit is composed of a first detection unit and a second detection unit, the first detection unit has a first detection circuit for passing current from a reference voltage source to the first field effect transistor, and detects whether current is flowing in the first field effect transistor through the first detection circuit, and the second detection unit has a second detection circuit for passing current from the reference voltage source to the second field effect transistor, and detects whether current is flowing in the second field effect transistor through the second detection circuit.

[0016] Preferably, in the magnetic resonance imaging apparatus according to the seventh aspect of the present invention, in the sixth aspect, 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 a driving voltage applied to a gate of the first field effect transistor and a gate of the second field effect transistor, a detection result based on the first detection unit, and a detection result based on the second detection unit.

[0017] Preferably, in the magnetic resonance imaging apparatus according to the eighth aspect of the present invention, in any of the first to seventh aspects, when the driving voltage is changed to switch the field effect transistor from the OFF state to the ON state and when the field effect transistor is switched from the ON state to the OFF state, the determination unit stops determining whether the field effect transistor is normal or abnormal for at least a certain period of time from the time when the driving voltage is changed. This is to prevent erroneous determination due to a time lag between the time when the driving voltage changes and the time when the detection result of the detection unit changes.

[0018] Preferably, in the magnetic resonance imaging apparatus according to the ninth aspect of the present invention, in any one of the first to eighth aspects, a Zener diode is provided on the gate side of the field effect transistor to prevent an abnormal voltage from being applied to the gate of the field effect transistor. This is to prevent a malfunction of the field effect transistor (a malfunction caused by an abnormal voltage being applied to the gate).

[0019] Preferably, the magnetic resonance imaging apparatus according to the tenth aspect of the present invention comprises, in any one of the first to ninth aspects, a determination receiving unit that receives determination results of the determination units provided corresponding to each of the plurality of decoupling circuits, the determination receiving unit being connected in parallel to the plurality of determination units and acquiring determination results from the plurality of determination units, respectively. Thus, it is possible to acquire determination results indicating the presence or absence of a failure related to the field effect transistor for each of the decoupling circuits corresponding to each of the multi-channel receiving coils, and in the case of a failure of the field effect transistor, its failure location can be identified.

[0020] Preferably, in the magnetic resonance imaging apparatus according to the eleventh aspect of the present invention, in the tenth aspect, the determination receiving unit adds a unique address of each determination unit to the received plurality of determination results.

[0021] Preferably, in the magnetic resonance imaging apparatus according to the twelfth aspect of the present invention, in the tenth aspect, the plurality of determination units have unique addresses for the respective determination units, and each determination result is transmitted to the determination receiving unit in association with the address.

[0022] Preferably, the magnetic resonance imaging apparatus according to the 13th aspect of the present invention comprises, in any one of the first aspect to the ninth aspect, a determination receiving unit that receives determination results from a plurality of determination units provided corresponding to each of the plurality of decoupling circuits, the plurality of determination units being connected in series, the plurality of determination units being set to 1 to n, and the last connected determination unit being set to the nth determination unit, the nth determination unit sends its own determination result to the (n-1)th determination unit, the (n-1)th determination unit connects the received determination result of the nth determination unit with its own determination result, and sends the connected determination result to the (n-2)th determination unit, and this process is repeated, whereby the first determination unit sends a determination result obtained by sequentially connecting the determination results of the plurality of determination units to the determination receiving unit. Thus, the number of signal cables for sending the determination results of the respective determination units back to the determination receiving unit can be reduced.

[0023] Preferably, in the magnetic resonance imaging apparatus according to the fourteenth aspect of the present invention, in the thirteenth aspect, the plurality of determination units have respective unique addresses of the determination units, and when the determination results are linked, the addresses of the determination units are linked together.

[0024] Effects of the Invention

[0025] According to the present invention, a field effect transistor that is turned on / off by a driving voltage applied to a gate is used as a switching switch of a decoupling circuit, thereby achieving power saving in driving the decoupling circuit. In addition, 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 it is possible to accurately determine faults such as disconnection and short circuit related to the field effect transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a perspective view showing the appearance of a magnetic resonance imaging apparatus (MRI apparatus) according to the present invention.

[0027] Figure 2 Yes means Figure 1 A diagram showing a schematic structure of the interior of an MRI apparatus.

[0028] Figure 3 This is a schematic diagram showing the main structure of the receiving coil device.

[0029] Figure 4 : is a circuit diagram showing an embodiment of a decoupling circuit according to the present invention.

[0030] Figure 5 It is a diagram showing an embodiment of a detection unit and a determination unit (error determination circuit) provided for each decoupling circuit.

[0031] Figure 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.

[0032] Figure 7 (A)~ Figure 7 (D) means Figure 5 The timing diagram of the T-ON signal A, detection signals B, C and error detection signal D is shown.

[0033] Figure 8 This is a block diagram showing a first embodiment of a transmission and reception unit for error determination results.

[0034] Fig. 9 This is a block diagram showing a second embodiment of a transmission and reception unit for error determination results.

[0035] Fig.10 It means from Fig. 9 FIG. 1 is a diagram showing an example of transmission data such as determination results transmitted by each determination unit.

[0036] Fig.11 This is a block diagram showing a third embodiment of a transmission and reception unit for error determination results.

[0037] Fig.12 This is a diagram showing an example of transmission data of a determination result transmitted from a determination unit connected to a determination receiving unit to the determination receiving unit.

[0038] Explanation of symbols

[0039] 100 - MRI device, 102 - subject, 108 - transmitting coil, 110 - gantry, 120 - cavity, 130 - bed, 200 - receiving coil device, 210, 210-1 to 210-n - decoupling circuit, 220A - first detection circuit, 220B - second detection circuit. DETAILED DESCRIPTION

[0040] Hereinafter, preferred embodiments of the magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings.

[0041] [Appearance of MRI device]

[0042] Figure 1 It is a perspective view showing the appearance of a magnetic resonance imaging apparatus according to the present invention.

[0043] Figure 1The illustrated magnetic resonance imaging apparatus (MRI (Magnetic Resonance Imaging) apparatus) 100 includes a gantry 110 and a bed 130 . The bed 130 includes an upper plate 130A disposed on the front side of a bore 120 which is a cylindrical imaging space provided in the gantry 110 .

[0044] [Internal structure of MRI device]

[0045] Figure 2 Yes means Figure 1 A diagram showing a schematic structure of the interior of an MRI apparatus.

[0046] like Figure 2 As shown, the MRI apparatus 100 comprises: a static magnetic field generating magnet 104 for generating a uniform static magnetic field in an imaging space where a subject 102 is arranged; a gradient magnetic field coil 106 for generating a gradient magnetic field in the imaging space; an RF (Radio Frequency) coil (transmitting coil) 108 for generating a high-frequency magnetic field for causing the nuclei of atoms constituting tissues of the subject 102 to generate nuclear magnetic resonance signals (NMR (Nuclear Magnetic Resonance) signals) (NMR signals); and a receiving coil device 200 for detecting the NMR signals generated from the subject 102.

[0047] like Figure 1 and Figure 2 As shown, the subject 102 lying supinely on the upper plate 130A of the bed 130 is moved so that the examination site of the subject 102 is located at the center of the static magnetic field in the cavity 120 by moving the upper plate 130A toward the cavity 120 .

[0048] The sequencer 118 sends commands to the high-frequency magnetic field generator 112 and the gradient magnetic field power supply 116 according to the imaging sequence (pulse sequence) 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 transmitting coil 108. The NMR signal generated from the subject 102 is received by the receiving coil device 200 and detected by the receiver 114.

[0049] The gradient magnetic field coil 106 is composed of gradient magnetic field coils in three directions, namely, X, Y, and Z, and generates gradient magnetic fields in each direction according to a signal from a gradient magnetic field power supply 116 .

[0050] In the receiver 114, the nuclear magnetic resonance frequency (detection reference frequency f0) serving as a detection reference is set by the sequencer 118. The sequencer 118 controls each unit so that it operates at a pre-programmed time point and intensity. Among the programs, the one that particularly records the RF pulse, the gradient magnetic field, the time point and intensity of signal reception is called a pulse sequence.

[0051] Various pulse sequences are known depending on the purpose, and their detailed description is omitted here.

[0052] The control unit 140 receives the signal detected by the receiver 114 and performs various signal processing such as image reconstruction while controlling the operation of the MRI apparatus 100 via the sequencer 118. In addition, the receiver 114 performs quadrature phase detection on the echo signal (NMR signal) as an analog wave based on the set detection reference frequency f0, converts it into raw data, and transmits it to the control unit 140. The raw data is also called an echo signal or measurement data.

[0053] The control unit 140 can be constituted by a computer. The computer used for the control unit 140 may be a personal computer or a workstation.

[0054] The control unit 140 receives various instruction inputs from the operation unit 150 , centrally controls each unit of the MRI apparatus 100 , and performs processing such as inverse Fourier transform of the echo signals in the spatial frequency domain received via the sequencer 118 to convert them into real-space images, thereby generating an MRI image.

[0055] 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 of a display (not shown).

[0056] That is, the operation unit 150 and the display function as a GUI for the operator to input start, stop (pause), selection of a pulse sequence, imaging conditions, processing conditions, and the like of the MRI apparatus 100 .

[0057] [Receiving coil device]

[0058] Figure 3 This is a schematic diagram showing the main structure of the receiving coil device.

[0059] like Figure 2 As shown, the receiving coil device 200 of this example is a flexible and thin receiving coil device that can cover a wide imaging range and can perform imaging of various examination sites.

[0060] like Figure 3As shown, the receiving coil device 200 is provided with a plurality of annular 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 respectively provided corresponding to each of the receiving coils 200-1, 200-2, ..., 200-n.

[0061] As described later, voltage-driven field effect transistors (FETs) are provided in the plurality of decoupling circuits 210 - 1 , 210 - 2 , . . . , 210 - n , and the FETs in the respective decoupling circuits are controlled to be on / off by a driving voltage supplied from the decoupling power supply 202 .

[0062] [Decoupling circuit]

[0063] Figure 4 : is a circuit diagram showing an embodiment of a decoupling circuit according to the present invention.

[0064] Figure 4 The decoupling circuit 210 shown in FIG. Figure 3 One of a plurality of decoupling circuits 210 - 1 , 210 - 2 , . . . , 210 - n is shown.

[0065] exist Figure 4 In the embodiment, capacitors C1, C2, and C3 are connected in series between two terminals PD1 and PD2, and a loop coil (not shown) serving as an antenna is connected to the other end. Figure 3 receiving coil shown).

[0066] The receiving coil is a part that is adjusted to resonate at a specific frequency and receives nuclear magnetic resonance signals (NMR signals) 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.

[0067] Figure 2 The transmitting coil 108 shown applies RF pulses to the subject 102, causing the nuclei of atoms constituting the biological tissue of the subject 102 to generate NMR signals. However, when the receiving coil is placed in a resonant state during the application of the RF pulses, there is a possibility that the highly sensitive receiving coil will receive an excessively large RF magnetic field, causing damage to peripheral circuits related to the receiving coil.

[0068] The decoupling circuit 210 is a circuit for performing the following switching: at least during the period when the RF pulse is transmitted from the transmitting coil 108, the receiving coil is fully decoupled (detuned), and the receiving coil is switched to a detuned state (non-resonant), and when the NMR signal generated from the biological tissue of the subject 102 is received after the RF pulse is transmitted, the receiving coil is switched to a resonant state.

[0069] Figure 4 In the decoupling circuit 210 shown, a first circuit 211 including a capacitor C4, a diode D1, a capacitor C5 and an inductor L1 and a second circuit 212 including 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.

[0070] Furthermore, by performing ON / OFF control on FET1 and FET2 , the decoupling circuit 210 switches the receiving coil to a detuned state or a resonant state.

[0071] That is, when FET1 and FET2 are turned on, the second circuit 212 including capacitors C6 and C7 is disconnected and connected in parallel to the diode D1 of the first circuit 211. Thus, 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.

[0072] On the other hand, when FET1 and FET2 are turned off, the second circuit 212 including 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 can receive NMR signals generated from biological tissue.

[0073] In addition, the NMR signal received by the receiving coil switched to the resonant state is acquired from the terminals PD3 and PD4 at both ends of the capacitor C1 via a preamplifier (not shown).

[0074] <ON / OFF Control of FET for Opening and Closing the Second Circuit>

[0075] Next, the ON / OFF control of the FET1 and FET2 of the second opening and closing circuit 212 will be described.

[0076] exist Figure 4 In the embodiment, the FET switch control unit 242 which functions as the control unit of FET1 and FET2 is connected to the control unit 242 of the FET switch. Figure 2 The command (command for causing the transmitting coil 108 to generate RF pulses) sent by the sequencer 118 to the high-frequency magnetic field generator 112 is synchronously output from the NOT circuit 243 to output a driving voltage (voltage signal T-ON) for ON / OFF control of FET1 and FET2.

[0077] The voltage signal T-ON is an H level signal (e.g., 5V) when FET1 and FET2 are turned on, and is an L level signal (e.g., 0V) when FET1 and FET2 are turned off. The voltage signal T-ON is output as an H level signal during the RF pulse generation period, and is output as an L level signal except during the RF pulse generation period. In addition, 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.

[0078] The voltage signal T-ON output from the FET switch control unit 242 is applied to the gates (G) of FET1 and FET2 via the inductor L2 and the resistor R1. The sources (S) of FET1 and FET2 are connected respectively and connected to the ground via the inductor L3, the resistor R3 and the inductor L4. In addition, a resistor R2 is provided between the resistor R1 and the gates (G) of FET1 and FET2. In addition, the resistance values ​​of the resistors R1 and R2 are sufficiently larger than the resistor R3, so that the current flowing through the ground becomes smaller.

[0079] In this example, when the voltage signal T-ON is at an H level, a gate voltage exceeding the threshold voltage is applied between the gate (G) and the source (S) of FET1 and FET2 to turn on the drain (D) and the source (S) (FET1 and FET2 are turned on). Furthermore, when the voltage signal T-ON is at an L level, the gate voltage applied to the gate (G) of FET1 and FET2 becomes 0V, and the drain (D) and the source (S) are disconnected (FET1 and FET2 are turned off).

[0080] Furthermore, in this example, a Zener diode ZD is provided between the gate (G) side of FET1 and FET2 and the ground to prevent an abnormal voltage from being applied to the gate (G) of FET1 and FET2. That is, an abnormal voltage exceeding the Zener voltage of the Zener diode ZD is not applied to the gate (G) of FET1 and FET2.

[0081] As described above, the decoupling circuit 210 performs ON / OFF control of FET1 and FET2 by the voltage signal T-ON, so that, for example, compared with a decoupling circuit using a current-driven PIN diode, it is possible to achieve power saving in driving control of the decoupling circuits 210-1 to 210-n for each multi-channel receiving coil.

[0082] <Error detection of decoupling circuit>

[0083] Next, error detection of the decoupling circuit 210 will be described.

[0084] exist Figure 4In the figure, reference numerals 220A and 220A are circuit diagrams showing examples of error detection circuits (first detection circuit and second detection circuit) for detecting failures (errors) such as disconnection and short circuit related to FET1 and FET2, respectively.

[0085] The first detection circuit 220A is a circuit for passing current from a reference voltage source to FET1, and an inductor L5, a resistor R4, a current detection resistor R5, and an inductor L6 are connected in series, and 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 FET1. The reference voltage Vref can be set to 15V, for example.

[0086] When FET1 is in the ON state, current I1 flows from the reference voltage source to the first detection circuit 220A, and resistor R4 has a resistance value sufficiently larger than the resistance value of current detection resistor R5 and the DC resistance of inductor L6, so the current value of current I1 becomes small. That is, power saving is achieved in error detection.

[0087] Furthermore, the second detection circuit 220B is a circuit for passing current from a reference voltage source to FET2, inductor L7, resistor R6, current detection resistor R7 and inductor L8 are connected in series, a reference voltage Vref is applied from the reference voltage source to one end of the circuit, and the other end is connected to the drain (D) of FET2.

[0088] The second detection circuit 220B has the same circuit configuration as the first detection circuit 220A. When the FET 2 is in the ON state, the current I2 flows from the reference voltage source to the second detection circuit 220B.

[0089] When FET1 and FET2 are in the ON state, by reducing the current values ​​of currents I1 and I2 flowing through the first detection circuit 220A and the second detection circuit 220B, it is possible to save power required for error detection of FET1 and FET2.

[0090] The first detection circuit 220A is provided with a circuit for obtaining the voltage V across the resistor R5. 1+ 、V 1- Similarly, a terminal for obtaining the voltage V across the resistor R7 is provided in the second detection circuit 220B. 2+ 、V 2- Terminals.

[0091] <Detection Unit and Judgment Unit>

[0092] Next, Figure 4The first detection circuit 220A and the second detection circuit 220B shown are detection units that detect whether current flows through FET1 and FET2, respectively, and determination units that determine whether FET1 and FET2 are normal or abnormal based on the detection results of the detection units.

[0093] Figure 5 It is a diagram showing an embodiment of a detection unit and a determination unit (error determination circuit) provided for each decoupling circuit.

[0094] exist Figure 5 Among them, the first detection unit 226 is a detection unit that detects whether the current I1 flows from the first detection circuit 220A to the FET1, and the second detection unit 227 is a detection unit that detects whether the current I2 flows from the second detection circuit 220B to the FET2.

[0095] The first detection unit 226 is composed of a differential amplifier 221 and a comparator 223 .

[0096] The voltage V across the resistor R5 of the first detection circuit 220A is applied to the positive input terminal and the negative input terminal of the differential amplifier 221, respectively. 1+ 、V 1- , the differential amplifier 221 amplifies these voltages V 1+ 、V 1- The difference is output to the positive input terminal of the comparator 223. Here, when the current I1 flows from the first detection circuit 220A to the FET1, the voltage V 1+ 、V 1- A potential difference (I1×R) corresponding to the current I1 and the resistance value R of the resistor R5 is generated therebetween, and a detection voltage corresponding to the potential difference is output from the differential amplifier 221 to the positive input terminal of the comparator 223.

[0097] A threshold voltage V is applied to the negative input terminal of the comparator 223 to determine whether the current I1 flows from the first detection circuit 220A to the FET 1. th , the detection voltage exceeds the threshold voltage V th When the detection voltage is the threshold voltage V th When the current I1 is below 0, the comparator 223 outputs the detection signal B (L level signal (“0”)) indicating that the current I1 is not flowing. That is, the comparator 223 outputs the detection signal B indicating whether the current I1 is flowing in the first detection circuit 220A.

[0098] Similarly, the second detection unit 227 is composed of a differential amplifier 222 and a comparator 224. The differential amplifier 222 and the comparator 224 of the second detection unit 227 have the same functions as the differential amplifier 221 and the comparator 223 of the first detection unit 226, and thus detailed description thereof is omitted.

[0099] The comparator 224 of the second detection unit 227 outputs a detection signal C indicating whether the current I2 flows through the second detection circuit 220B.

[0100] The error determination circuit 225 is composed of two exclusive OR circuits (XOR circuits) 225A and 225B and an OR circuit (OR circuit) 225C.

[0101] A T-ON signal A is applied from the NOT circuit 245 to one input terminal of each of the XOR circuits 225A and 225B. The NOT circuit 245 is provided at Figure 4 The FET switch control unit 242 is shown in the figure, and is provided in parallel with a NOT circuit 243 which outputs a voltage signal T-ON for performing ON / OFF control on FET1 and FET2.

[0102] 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 switches to an H level signal or an L level signal at the same time point. The reason for providing the NOT circuit 245 different 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.

[0103] A detection signal B of the current I1 is applied to the other input terminal of the XOR circuit 225A from the comparator 223, and the XOR circuit 225A outputs a determination result of an H level or an L level according to the T-ON signal A and the detection signal B. Here, the XOR circuit 225A outputs a determination result of an L level ("0") when the FET1 of the decoupling circuit 210 is normal, and outputs a determination result of an H level ("1") when an abnormality such as a disconnection or a short circuit occurs in the FET1.

[0104] Similarly, a detection signal C of the current I2 is applied to the other input terminal of the XOR circuit 225B from the comparator 224, and the XOR circuit 225B outputs a determination result of an H level or an L level according to the T-ON signal A and the detection signal C. Here, the XOR circuit 225B outputs a determination result of an L level ("0") when the FET2 of the decoupling circuit 210 is normal, and outputs a determination result of an H level ("1") when an abnormality occurs in the FET2.

[0105] The OR circuit 225C takes the OR condition of the determination 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. In addition, the error detection signal D output from the OR circuit 225C becomes an L level ("0") when the decoupling circuit 210 is normal, and becomes an H level ("1") when the decoupling circuit 210 is abnormal.

[0106] Figure 6 It is a truth table showing the relationship between the T-ON signal A corresponding to the FET control signal input to the error judgment circuit 225 , 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 judgment circuit 225 .

[0107] like Figure 6 As shown, 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 the decoupling circuit 210 (at least one of FET1 and FET2) is abnormal.

[0108] Figure 7 (A)~ Figure 7 (D) means Figure 5 The timing diagram of the T-ON signal A, detection signals B, C and error detection signal D is shown.

[0109] Figure 7 The example shown shows each signal when the decoupling circuit 210 (FET1 and FET2) is normal.

[0110] However, in Figure 7 When there is a time lag between the switching time of the L level and H level of the T-ON signal A synchronized with the ON / OFF control of FET1 and FET2 shown in (A) and the change time of the L level and H level of the detection signals B and C output from the comparators 223 and 224, during this period, the error detection signal D becomes an H level indicating that an abnormality has occurred in the decoupling circuit 210.

[0111] Therefore, it is preferable that 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, the determination of the normality or abnormality of FET1 and FET2 is stopped for at least a certain period from the time of the change of the voltage signal T-ON. That is, it is preferable to shield (not use) the error detection signal D output from the error determination circuit 225 during the time lag between the switching time point of the T-ON signal A synchronized with the voltage signal T-ON and the change time point of the detection signals B and C.

[0112] [Error judgment result transmission and reception unit]

[0113] Next, the Figure 5 The transmission and reception section of the error determination result detected by the determination section (including the first detection section 226, the second detection section 227, and the determination section of the error determination circuit 225) of each decoupling circuit shown will be described.

[0114] <First Embodiment of the Error Determination Result Transmission and Reception Unit>

[0115] Figure 8 This is a block diagram showing a first embodiment of a transmission and reception unit for error determination results.

[0116] like Figure 8 As shown, corresponding decoupling circuits 210-1, 210-2, ..., 210-n are respectively provided on the plurality of receiving coils 200-1, 200-2, ..., 200-n functioning as antennas, and corresponding to the decoupling circuits 210-1, 210-2, ..., 210-n, a circuit including Figure 5 The first detection unit 226, the second detection unit 227, and the determination units 231-1, 231-2, ..., 231-n of the error determination circuit 225 are shown.

[0117] Each determination unit 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.

[0118] And, in Figure 8 In the embodiment, the detuning function control unit 240 includes a FET switch control unit 242 and a determination receiving unit 244 .

[0119] As described above, the FET switch control unit 242 outputs the voltage signal T-ON for ON / OFF control of FET1 and FET2 to the decoupling circuits 210-1, 210-2, ..., 210-n according to the instructions of the sequencer 118, and outputs the T-ON signal A synchronized with the ON / OFF control of FET1 and FET2 to the determination units 231-1, 231-2, ..., 231-n.

[0120] The determination receiving unit 244 functions as a receiving unit that is connected in parallel to the plurality of determination units 231 - 1 , 231 - 2 , . . . , 231 - n in a one-to-many manner and receives determination results transmitted from the determination units 231 - 1 , 231 - 2 , . . . , 231 - n .

[0121] The determination receiving unit 244 adds the unique address of each determination unit (the unique number assigned to each determination unit) to the plurality of determination results according to a certain rule, and sends the result back to the sequencer 118 .

[0122] The sequencer 118 or the subsequent control unit 140 of the sequencer 118 ( Figure 2 ) When receiving a determination result indicating an abnormality in FET1 and / or FET2, it is possible to detect which of the multiple decoupling circuits 210-1, 210-2, ..., 210-n has an abnormality based on the address attached to the determination result.

[0123] Furthermore, not only when the determination receiving unit 244 adds an address to the detection result, but also when each determination unit 231-1, 231-2, ..., 231-n sends its own determination result, its own determination result can be associated with the address assigned to it (the address assigned to its own determination result is attached) and sent.

[0124] Furthermore, the transmission of the determination results and the like is not limited to the case where an electric signal cable is used for electrical transmission, and an optical signal cable may be used for optical transmission, or wireless or other communication means may be used.

[0125] <Second Embodiment of the Transceiver of Error Judgment Result>

[0126] Fig. 9 is a block diagram showing a second embodiment of a transceiver unit for showing an error determination result. Fig. 9 In the transceiver unit of the second embodiment shown in FIG. Figure 8 The same parts as those of the transmission and reception unit of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0127] Fig. 9 The method of communicating the error determination result of the transmission and reception unit of the second embodiment shown is different from that of the transmission and reception unit of the first embodiment.

[0128] That is, the plurality of determination 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.

[0129] Here, the plurality of determination units 232-1, 232-2, ..., 232-n are referred to as the first to nth determination units, the first determination unit 232-1 is connected to the determination receiving unit 244, and the last determination unit 232-n connected in series is referred to as the nth determination unit.

[0130] The nth determination unit 232-n sends its own determination result to the (n-1)th determination unit 232-(n-1), and the (n-1)th determination unit 232-(n-1) connects the received determination result of the nth determination unit 232-n with its own determination result, and sends the connected determination result to the (n-2)th determination unit 232-(n-2). This process is repeated, whereby the first determination unit 232-1 sends the determination result (transmission data) obtained by sequentially connecting the determination results of multiple determination units 232-1, 232-2, ..., 232-(n-1), ..., 232-n to the determination receiving unit 244.

[0131] According to the error determination result transmitting and receiving unit of the second embodiment, the number of signal cables can be reduced compared with the first embodiment.

[0132] Furthermore, when each of the determination units 232-1, 232-2, ..., 232-(n-1), ..., 232-n concatenates its own determination results, it is preferable that each of the determination units 232-1, 232-2, ..., 232-(n-1), ..., 232-n also concatenates the address assigned to itself at the same time.

[0133] Fig.10 It means from Fig. 9 FIG. 1 is a diagram showing an example of transmission data such as determination results transmitted by each determination unit.

[0134] like Fig.10 As shown, the nth determination unit 232-n sends the transmission data of its own address n+determination result (0) to the (n-1)th determination unit 232-(n-1). Fig.10 In the example, the determination result in the transmission data is set to 1-bit data, which becomes "0" in a normal state and "1" in an abnormal state (error).

[0135] The (n-1)th determination unit 232-(n-1) concatenates its own address (n-1) + determination result (0) with the address n + determination result (0) received from the nth determination unit 232-n and transmits the transmission data to the (n-2)th determination unit 232-(n-2).

[0136] By sequentially repeating the above-described processing in each determination unit, the first determination unit 231 - 1 can transmit the addressed transmission data indicating the determination results of all the determination units 232 - 1 , 232 - 2 , . . . , 232 -(n−1) , . . . , 232 - n to the determination receiving unit 244 .

[0137] <Third Embodiment of the Transceiver of Error Judgment Result>

[0138] Fig.11 is a block diagram showing a third embodiment of a transceiver unit for showing an error determination result. Fig.11In the transceiver unit of the third embodiment shown in FIG. Fig. 9 The same parts as the transmitting and receiving unit of the second embodiment shown are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0139] Fig.11 The transceiver of the third embodiment shown is different from the transceiver of the second embodiment in that a plurality of detection units (switch units) are provided in each decoupling circuit, and a determination unit is independently provided in each detection unit.

[0140] That is, the receiving coil 200-1 is provided with a plurality of (two) switch units 210-1a and 210-1b of the decoupling circuit, and is provided with determination units 233-1a and 233-1b for respectively determining whether the switch units 210-1a and 210-1b are normal or abnormal. The other receiving coils 200-2 to 200-n are also provided with two switch units and determination units.

[0141] like Fig.11 As shown, all determination units 233-1a, 233-1b, 233-2a, 233-2b, ..., 233-na, 233-nb are connected to the determination unit 233-a, and the determination unit 233-a sends the sending data of the determination results connected to all determination units 233-1a, 233-1b, 233-2a, 233-2b, ..., 233-na, 233-nb to the determination receiving unit 244.

[0142] Fig.12 This is a diagram showing an example of transmission data of a determination result transmitted from a determination unit connected to a determination receiving unit to the determination receiving unit.

[0143] like Fig.12 As shown, the determination unit 233-1a connected to the determination receiving unit 244 transmits the transmission data of the determination results with addresses connected to all the determination units 233-1a, 233-1b, 233-2a, 233-2b, . . . , 233-na, and 233-nb to the determination receiving unit 244.

[0144] According to the third embodiment, similarly to the second embodiment, the number of signal cables for transmitting data can be reduced, and when a plurality of switch units are provided on one receiving coil, the normal or abnormal determination result can be transmitted to the determination receiving unit 244 for each switch unit.

[0145] [other]

[0146] In the present embodiment, two FETs 1 and FET 2 are provided in one decoupling circuit, but one FET may be used.

[0147] Also, you can Figure 4 The resistor R3 of the circuit portion 220C between the source (S) of FET1 and FET2 and the ground indicated by the dotted line is used to detect the current I flowing from the source (S) of FET1 and FET2 to the ground. SHUNT The current detection resistor is used. That is, the voltage V across the resistor R3 can be used to detect the current. 0+ 、V 0- , detection current I SHUNT , thereby detecting the normality or abnormality of FET1 and FET2.

[0148] In addition, the current I SHUNT The current flowing through the resistor R2 is included, but the resistor R2 has a resistance value larger than that of the resistor R3 so that the current can be ignored. SHUNT When the determination of whether FET1 and FET2 are normal or abnormal is not performed, the circuit portion 220C indicated by the dotted line can be omitted.

[0149] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

Claims

1. A magnetic resonance imaging device comprising: a plurality of receiving coils having a plurality of coils and being adjusted to resonate at a specific frequency and receive nuclear magnetic resonance signals from the subject; a plurality of decoupling circuits, respectively connected to the plurality of receiving coils and having field effect transistors, for switching each receiving coil to a resonant state or a detuned state according to a driving voltage applied to a gate of the field effect transistor; and a control unit that controls the driving voltage applied to the gates of the field effect transistors of the plurality of decoupling circuits, The magnetic resonance imaging apparatus comprises: a detection unit including a detection circuit for causing a current to flow from a reference voltage source to the field effect transistor, and detecting whether the current flows through the field effect transistor by the detection circuit; and The determination unit determines whether the field effect transistor is normal or abnormal based on the state of the drive voltage applied to the gate of the field effect transistor and the detection result of the detection unit.

2. The magnetic resonance imaging apparatus according to claim 1, wherein: The detection circuit includes a current detection resistor. The detection unit detects whether current flows through the field effect transistor based on a potential difference between both ends of the resistor.

3. The magnetic resonance imaging apparatus according to claim 2, wherein: The detection circuit includes an inductor.

4. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: 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.

5. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: The detection circuit is arranged between the source of the field effect transistor and the ground.

6. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: The field effect transistor of the decoupling circuit is composed of a first field effect transistor and a second field effect transistor, each of which has a source connected thereto. The detection unit is composed of a first detection unit and a second detection unit, the first detection unit has a first detection circuit for passing current from the reference voltage source to the first field effect transistor, and the first detection circuit is used to detect whether the current is flowing in the first field effect transistor, and the second detection unit has a second detection circuit for passing current from the reference voltage source to the second field effect transistor, and the second detection circuit is used to detect whether the current is flowing in the second field effect transistor.

7. The magnetic resonance imaging apparatus according to claim 6, wherein: 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 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 based on the first detection unit, and the detection result based on the second detection unit.

8. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: When the driving voltage is changed to switch the field effect transistor from the 0FF state to the ON state and when the field effect transistor is switched from the ON state to the OFF state, the determination unit stops determining whether the field effect transistor is normal or abnormal for at least a certain period of time from the moment the driving voltage changes.

9. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: A Zener diode is provided on the gate side of the field effect transistor to prevent an abnormal voltage from being applied to the gate of the field effect transistor.

10. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, comprising: 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 acquires determination results from each of the plurality of determination units.

11. The magnetic resonance imaging apparatus according to claim 10, wherein: The determination receiving unit adds the unique address of each of the determination units to the received plurality of determination results.

12. The magnetic resonance imaging apparatus according to claim 10, wherein: The plurality of determination units have respective unique addresses of the determination units, and the determination results are associated with the addresses and transmitted to the determination receiving unit.

13. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, comprising: a determination receiving unit that receives determination results from the plurality of determination units provided corresponding to each of the plurality of decoupling circuits, A plurality of the determination sections are connected in series, respectively. When the plurality of determination units are set to 1 to n respectively, and the last connected determination unit is set to the nth determination unit, the nth determination unit sends its own determination result to the (n-1)th determination unit, the (n-1)th determination unit connects the received determination result of the nth determination unit with its own determination result, and sends the connected determination result to the (n-2)th determination unit, and this process is repeated, whereby the first determination unit sends the determination result obtained by sequentially connecting the determination results of the plurality of determination units to the determination receiving unit.

14. The magnetic resonance imaging apparatus according to claim 13, wherein: The plurality of determination units have their own unique addresses, and when the determination results are linked, their own addresses are linked together.

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