JP6956597B2 - Magnetic resonance imaging device - Google Patents

Description

Embodiments of the present invention relate to a magnetic resonance imaging apparatus.

The magnetic resonance imaging (MRI) device has a gradient magnetic field power supply, the number of outputs from the power supply used as the power supply for the amplifier, depending on the number of output channels that power the gradient magnetic field coil from the amplifier. To set. At this time, in the conventional gradient magnetic field power supply, the output current from the power supply is allocated by hardware control.

However, the gradient magnetic field power supply that performs hardware control has a complicated configuration because there are many analog signals to be controlled.

Japanese Unexamined Patent Publication No. 2013-173 JP-A-2017-35305

The problem to be solved by the present invention is to control the allocation of the output current from the power supply by using software.

The magnetic resonance imaging apparatus according to the embodiment includes a plurality of gradient magnetic field coils that receive power supply to generate a gradient magnetic field of a plurality of axes, and a gradient magnetic field power supply that supplies power. The gradient magnetic field power supply includes a plurality of amplifiers connected to a plurality of gradient magnetic field coils, a power supply device that supplies current to the plurality of amplifiers, a measuring instrument that measures the voltage applied to the plurality of amplifiers, and a voltage. Based on this, it has a power control circuit that controls the current supplied from the power supply to the amplifier. The power control circuit is composed of a comparison unit that compares the voltage applied to the plurality of amplifiers with the threshold voltage, the comparison result by the comparison unit, and the current supplied to each of the plurality of amplifiers corresponding to the plurality of gradient magnetic field coils. It includes a memory having correspondence information that associates with the ratio of the currents supplied to the plurality of amplifiers to the total sum.

FIG. 1 is a diagram showing a configuration of an MRI apparatus according to an embodiment. FIG. 2 is a diagram showing a configuration of a gradient magnetic field power supply and the like in one embodiment. FIG. 3 is a diagram showing a circuit configuration of a gradient magnetic field power supply in one embodiment. FIG. 4 is a diagram showing a software configuration related to the power control circuit in one embodiment. FIG. 5 is a flowchart showing a process executed by the power control circuit in one embodiment. FIG. 6 is a diagram showing a look-up table in one embodiment.

Hereinafter, embodiments of the MRI apparatus will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of an MRI apparatus according to an embodiment. For example, as shown in FIG. 1, the MRI apparatus 100 according to the embodiment includes a static magnetic field magnet 101, a gradient magnetic field coil 103, a gradient magnetic field power supply 105, a sleeper 107, a sleeper control circuit 109, and a transmission circuit 113. A transmission coil 115, a reception coil 117, a reception circuit 119, an image pickup control circuit 121, an interface 123, a display 125, a storage device 127, and a processing circuit 129 are provided.

The static magnetic field magnet 101 is, for example, a magnet formed in a hollow substantially cylindrical shape. The static magnetic field magnet 101 generates a uniform static magnetic field in the internal space. As the static magnetic field magnet 101, for example, a superconducting magnet or the like is used. The static magnetic field magnet 101 may be configured in an open shape.

The gradient magnetic field coil 103 is a coil formed in a hollow cylindrical shape. The gradient magnetic field coil 103 is arranged inside the static magnetic field magnet 101. The gradient magnetic field coil 103 is formed by combining three coils corresponding to the X, Y, and Z axes that are orthogonal to each other. It is assumed that the Z-axis direction is the same as the direction of the static magnetic field. Further, the Y-axis direction is a vertical direction, and the X-axis direction is a direction perpendicular to the Z-axis and the Y-axis. The three coils in the gradient magnetic field coil 103 are individually supplied with electric power from the gradient magnetic field power supply 105 to generate a gradient magnetic field in which the magnetic field strength changes along the X, Y, and Z axes.

The gradient magnetic fields of the X, Y, and Z axes generated by the gradient magnetic field coil 103 form, for example, a gradient magnetic field for frequency encoding (also referred to as a lead-out gradient magnetic field), a gradient magnetic field for phase encoding, and a gradient magnetic field for slice selection. .. The gradient magnetic field for frequency encoding is used to change the frequency of the MR signal according to the spatial position. The gradient magnetic field for phase encoding is used to change the phase of a magnetic resonance (hereinafter referred to as MR) signal according to a spatial position. The gradient magnetic field for slice selection is used to determine the imaging cross section.

The gradient magnetic field power supply 105 is a power supply device that supplies a current to the gradient magnetic field coil 103 under the control of the imaging control circuit 121. A detailed description of the gradient magnetic field power supply 105 will be described later.

The bed 107 is a device provided with a top plate 107a on which the subject P is placed. The bed 107 inserts the top plate 107a on which the subject P is placed into the bore 111 under the control of the bed control circuit 109. The sleeper 107 is installed, for example, in the examination room where the MRI apparatus 100 is installed so that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 101.

The bed control circuit 109 is a circuit that controls the bed 107, and moves the top plate 107a in the longitudinal direction and the vertical direction by driving the bed 107 according to the instruction of the operator via the interface 123. The bed control circuit 109 is an example of a means for realizing the bed control unit.

The transmission circuit 113 supplies a high-frequency pulse (RF (Radio Frequency) pulse) corresponding to a Larmor frequency or the like to the transmission coil 115 under the control of the image pickup control circuit 121. The transmission circuit 113 is an example of a means for realizing the transmission unit.

The transmission coil 115 is an RF coil arranged inside the gradient magnetic field coil 103. The transmission coil 115 receives the supply of RF pulses from the transmission circuit 113 and generates a transmission RF wave corresponding to a high-frequency magnetic field. The transmission coil is, for example, a whole body coil (WHole body coil: WB coil). The WB coil may be used as a transmission / reception coil.

The receiving coil 117 is an RF coil arranged inside the gradient magnetic field coil 103. The receiving coil 117 receives the MR signal radiated from the subject P by the high frequency magnetic field. The receiving coil 117 outputs the received MR signal to the receiving circuit 119. The receiving coil 117 is, for example, a coil array having one or more, typically a plurality of coil elements. Although the transmission coil 115 and the reception coil 117 are described as separate RF coils in FIG. 1, the transmission coil 115 and the reception coil 117 may be implemented as an integrated transmission / reception coil. The transmission / reception coil corresponds to the image pickup target of the subject P, and is a local transmission / reception RF coil such as a head coil.

The reception circuit 119 generates a digital MR signal, which is digitized complex number data, based on the MR signal output from the reception coil 117 under the control of the image pickup control circuit 121. Specifically, the receiving circuit 119 performs various signal processing on the MR signal output from the receiving coil 117, and then analog / digital (A / D (Analog)) for the data subjected to the various signal processing. to Digital)) Perform the conversion. The receiving circuit 119 samples the A / D converted data. As a result, a digital MR signal (hereinafter referred to as MR data) is generated. The receiving circuit 119 outputs the generated MR data to the imaging control circuit 121. The receiving circuit 119 is an example of a means for realizing the receiving unit.

The image pickup control circuit 121 controls the gradient magnetic field power supply 105, the transmission circuit 113, the reception circuit 119, and the like according to the image pickup protocol output from the processing circuit 129, and performs an image pickup on the subject P. The imaging protocol has various pulse sequences depending on the examination. The imaging protocol includes a gradient magnetic field waveform indicating the magnitude of the current supplied to the gradient magnetic field coil 103 by the gradient magnetic field power supply 105, a timing when the current is supplied to the gradient magnetic field coil 103 by the gradient magnetic field power supply 105, and transmission by the transmission circuit 113. The magnitude of the RF pulse supplied to the coil 115, the timing at which the RF pulse is supplied to the transmitting coil 115 by the transmitting circuit 113, the timing at which the MR signal is received by the receiving coil 117, and the like are defined. The image pickup control circuit 121 is an example of a means for realizing the image pickup control unit.

The interface 123 has a circuit that receives various instructions and information inputs from the operator. The interface 123 has a circuit related to a pointing device such as a mouse or an input device such as a keyboard. The circuit of the interface 123 is not limited to circuits related to physical operating parts such as a mouse and a keyboard. For example, the interface 123 receives an electric signal corresponding to an input operation from an external input device provided separately from the MRI apparatus 100, and processes the electric signal so as to output the received electric signal to various circuits. It may have a circuit.

The display 125 displays various MR images generated by the image generation function, various information related to imaging and image processing, and the like under the control of the system control function 129a in the processing circuit 129. The display 125 is, for example, a display device such as a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display or monitor known in the art.

The storage device 127 stores MR data filled in the k-space via the image generation function 129b, image data generated by the image generation function 129b, and the like. The storage device 127 stores various imaging protocols, imaging conditions including a plurality of imaging parameters defining the imaging protocol, and the like. The storage device 127 stores programs corresponding to various functions executed by the processing circuit 129. The storage device 127 is, for example, a RAM (Random Access Memory), a semiconductor memory element such as a flash memory, a hard disk drive, a solid state drive, an optical disk, or the like. Further, the storage device 127 may be a drive device that reads and writes various information to and from a portable storage medium such as a CD-ROM drive, a DVD drive, and a flash memory. The storage device 127 is an example of a means for realizing the storage unit.

The processing circuit 129 has a processor (not shown), a memory such as a ROM (Read-Only Memory) or a RAM, and the like as hardware resources, and controls the MRI apparatus 100. The processing circuit 129 has a system control function 129a and an image generation function 129b. Various functions performed by the system control function 129a and the image generation function 129b are stored in the storage device 127 in the form of a program that can be executed by a computer. The processing circuit 129 is a processor that realizes the functions corresponding to each program by reading the programs corresponding to these various functions from the storage device 127 and executing the programs. In other words, the processing circuit 129 in the state where each program is read has a plurality of functions shown in the processing circuit 129 of FIG. The processing circuit 129 is an example of a means for realizing the processing unit.

Although it has been described in FIG. 1 that these various functions are realized by a single processing circuit 129, a processing circuit 129 is configured by combining a plurality of independent processors, and each processor executes a program. The function may be realized by. In other words, each of the above-mentioned functions may be configured as a program, and one processing circuit may execute each program, or a specific function may be implemented in a dedicated and independent program execution circuit. You may.

The term "processor" used in the above description refers to, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an integrated circuit for a specific application (Application Specific Integrated Circuit: ASIC), a programmable logic device (for example, a simple programmable logic device). Circuits such as programmable logic devices (Single Programmable Logical Devices: SPLDs), composite programmable logic devices (Complex Programmable Logic Devices: CPLDs), and field programmable gate arrays (field programmable gate arrays (FPGAs)).

The processor realizes various functions by reading and executing a program stored in the storage device 127. Instead of storing the program in the storage device 127, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit. Similarly, the sleeper control circuit 109, the transmission circuit 113, the reception circuit 119, the image pickup control circuit 121, and the like are also composed of electronic circuits such as the processor.

The processing circuit 129 controls the MRI apparatus 100 by the system control function 129a. Specifically, the processing circuit 129 reads the system control program stored in the storage device 127, expands it on the memory, and controls each circuit of the MRI apparatus 100 according to the expanded system control program. For example, the processing circuit 129 reads the imaging protocol from the storage device 127 based on the imaging conditions input from the operator via the interface 123 by the system control function 129a. The processing circuit 129 may generate an imaging protocol based on the imaging conditions. The processing circuit 129 transmits an imaging protocol to the imaging control circuit 121 to control imaging of the subject P. The processing circuit 129 that executes the system control function 129a is an example of a means for realizing the system control unit.

The processing circuit 129 fills MR data along the lead-out direction in k-space according to the strength of the lead-out gradient magnetic field by the image generation function 129b. The processing circuit 129 generates an MR image by performing a Fourier transform on the MR data filled in the k-space. The processing circuit 129 outputs the MR image to the display 125 or the storage device 127. The processing circuit 129 that executes the image generation function 129b is an example of a means for realizing the image generation unit.

The above is the description of the overall configuration of the MRI apparatus 100 according to the embodiment. Next, the configuration of the gradient magnetic field power supply 105 will be described in detail with reference to FIG.

FIG. 2 is a diagram showing a configuration of a gradient magnetic field power supply and the like in one embodiment. For example, as shown in FIG. 2, the gradient magnetic field power supply 105 in one embodiment includes an internal power supply unit 10 and an amplifier 20. The internal power supply unit 10 includes a power supply device 11, a measuring instrument 12, and a power control circuit 13. The amplifier 20 includes a capacitor bank for an X-axis gradient magnetic field coil (hereinafter referred to as an X-axis capacitor bank) 21x, a capacitor bank for a Y-axis gradient magnetic field coil (hereinafter referred to as a Y-axis capacitor bank) 21y, and a Z-axis gradient magnetic field. Coil capacitor bank (hereinafter referred to as Z-axis capacitor bank) 21z, X-axis gradient magnetic field coil amplifier (hereinafter referred to as X-axis amplifier) 22x, and Y-axis gradient magnetic field coil amplifier (hereinafter referred to as Y-axis amplifier). It includes 22y (referred to as) and 22z for a Z-axis gradient magnetic field coil (hereinafter referred to as a Z-axis amplifier).

The power supply device 11 is a device having a role of a power source for supplying energy to the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z, respectively. Under the control of the power control circuit 13, the power supply 11 transfers the first current, the second current, and the third current to the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z. To supply each. The power supply 11 is composed of, for example, an AC / DC converter (not shown), a full bridge circuit, a pulse width modulation (PWM) control circuit, and the like. The AC / DC converter rectifies the AC output from the AC power supply. The full bridge circuit supplies power to the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z, respectively. The PWM control circuit controls a plurality of switching elements in each of the plurality of full bridge circuits using the correction amount received from the power control circuit 13 as a drive signal.

The power supply device 11 is, for example, a direct current power supply having CV (Constant Voltage) / CC (Constant Current) characteristics. In the case of a DC power supply having CV / CC characteristics, the power supply device 11 functions as a constant current source when the load in the subsequent stage is large, and functions as a constant voltage source when the load in the subsequent stage is small. However, in the situation described in the following embodiment, since the load in the subsequent stage is large, the power supply 11 functions as a constant current source.

The measuring instrument 12 is a measuring instrument that measures the current supplied to each of the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z and the voltage corresponding to the current. The measuring instrument 12 has a first voltage corresponding to the first current supplied to the X-axis amplifier 22x, a second voltage corresponding to the second current supplied to the Y-axis amplifier 22y, and a Z-axis amplifier. The third voltage corresponding to the third current supplied to 22z is measured, respectively.

Specifically, the measuring instrument 12 includes an X-axis measuring instrument 12x, a Y-axis measuring instrument 12y, and a Z-axis measuring instrument 12z. The X-axis measuring instrument 12x measures the first current supplied to the X-axis amplifier 22x and the first voltage corresponding to the first current. The Y-axis measuring instrument 12y measures the second current supplied to the Y-axis amplifier 22y and the second voltage corresponding to the second current. The Z-axis measuring instrument 12z measures a third current supplied to the Z-axis amplifier 22z and a third voltage corresponding to the third current. The X-axis measuring instrument 12x, the Y-axis measuring instrument 12y, and the Z-axis measuring instrument 12z output the measured current and voltage values to the power control circuit 13, respectively.

The power control circuit 13 has a processor (not shown), a memory such as a ROM or a RAM, or the like as hardware resources, and controls the power supply device 11. The power control circuit 13 receives measured current and voltage values from the X-axis measuring instrument 12x, the Y-axis measuring instrument 12y, and the Z-axis measuring instrument 12z. The power control circuit 13 uses the received current and voltage values to determine the ratio of the amount of current output from the power supply 11 to the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z (hereinafter referred to as the current ratio). It has a function of controlling (hereinafter referred to as a current ratio control function). The current ratio is the ratio of the target current to the total amount of current supplied by the power supply device 11 (hereinafter referred to as the total current amount). In other words, the power control circuit 13 uses the first voltage, the second voltage, and the third voltage measured by the measuring instrument 12 by the current ratio control function, and uses the X-axis amplifier 22x and the Y-axis. The first current, the second current, and the third current supplied to the amplifier 22y and the Z-axis amplifier 22z are controlled.

The current ratio control function is stored in a memory (or storage device 127) in the form of a program that can be executed by a computer. The power control circuit 13 is a processor that realizes the current ratio control function by reading a program corresponding to the current ratio control function from a memory or the like and executing the program. The power control circuit 13 is an example of a means for realizing the power control unit.

Generally speaking, the power control circuit 13 compares the measured voltage with the threshold voltage to determine whether or not the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z have been charged. To judge. The power control circuit 13 determines the current ratio corresponding to the combination of the above-mentioned determination results. The power control circuit 13 controls the full bridge circuit in the power supply device 11 by using feedback control such as PI (Proportional International) control or PID (Proportional International Differential) control with respect to the amount of current according to the current ratio. The amount of correction to be used is determined. The power control circuit 13 controls the power supply device 11 using the determined correction amount.

When the current is preferentially supplied to the X-axis amplifier 22x, the power control circuit 13 supplies, for example, a current having a current ratio of 92% to the X-axis amplifier 22x, and the Y-axis amplifier 22y and the Z-axis amplifier 22z. A current having a current ratio of 4% is supplied to each of them. The current supplied to the Y-axis amplifier 22y and the Z-axis amplifier 22z (here, the current ratio is 4%) is the current for operating the amplifier itself (hereinafter referred to as idling current), and depends on the performance of the amplifier. Set to an appropriate amount of current.

The X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z are connected between the power supply 11 and the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z. The X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z supply power to the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z together with the power supply device 11. That is, the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z are capacitors that act as batteries that bear the power supply that cannot be supplemented by the power supply device 11. Specifically, the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z temporarily store the power flowing in from the power supply device 11, and store the stored power in X as needed. Output to the axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z.

Here, the roles of the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z are as follows. For example, when it is necessary to pass a large current through all of the X-axis gradient magnetic field coil 103x, the Y-axis gradient magnetic field coil 103y, and the Z-axis gradient magnetic field coil 103z in a short time, the power supply device 11 temporarily supplies the electric current. The required power supply may exceed the power that can be produced. Even in such a case, by storing power in the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z, the gradient magnetic field power supply 105 can be the X-axis gradient magnetic field coil 103x and the Y-axis tilt. Stable power can be supplied to the magnetic field coil 103y and the Z-axis gradient magnetic field coil 103z.

The X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z amplify the gradient magnetic field waveform into a large current pulse. The X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z output the amplified large current pulse to the gradient magnetic field coil 103.

As described above, the gradient magnetic field power supply 105 supplies the current required for imaging to the gradient magnetic field coil 103. Hereinafter, the gradient magnetic field power supply 105 will be described in more detail.

FIG. 3 is a diagram showing a circuit configuration of a gradient magnetic field power supply in one embodiment. FIG. 3 shows a configuration relating to the X-axis gradient magnetic field coil 103x, and omits the configuration relating to the Y-axis gradient magnetic field coil 103y and the configuration relating to the Z-axis gradient magnetic field coil 103z for the sake of simplification of the description. For example, as shown in FIG. 3, the gradient magnetic field power supply 105 corresponding to the X-axis gradient magnetic field coil 103x includes a power supply device 11, an X-axis measuring instrument 12x, a power control circuit 13, and an X-axis capacitor bank 21x. It is equipped with an X-axis amplifier 22x.

The X-axis measuring instrument 12x measures the value of the current output from the power supply device 11 to the X-axis amplifier 22x and the value of the voltage corresponding to the current. For example, the X-axis measuring instrument 12x includes a voltmeter 12xa and an ammeter 12xb. The voltmeter 12xa measures the value of the voltage. The voltmeter 12xa outputs the measured voltage value to the power control circuit 13. The ammeter 12xb measures the value of the current. The ammeter 12xb outputs the measured current value to the power control circuit 13.

The power control circuit 13 receives a voltage (V _{out_x} ) value and a current (I _{out_x} ) value from the X-axis measuring instrument 12x. The power control circuit 13 controls the power supply 11 by software control described later using the voltage value and the current value.

The X-axis capacitor bank 21x is provided between the power supply 11 and the X-axis amplifier 22x. The X-axis capacitor bank 21x is connected in parallel to the output from the power supply 11. The X-axis capacitor bank 21x, together with the power supply device 11, supplies power to the gradient magnetic field coil 103.

The X-axis amplifier 22x amplifies the gradient magnetic field waveform received from the image pickup control circuit 121 into a large current pulse. The X-axis amplifier 22x outputs the amplified large current pulse to the X-axis gradient magnetic field coil 103x. The power supply voltage applied to the X-axis amplifier 22x is a DC voltage generated by the power supply device 11.

FIG. 4 is a diagram showing a software configuration related to the power control circuit 13 in one embodiment. For example, as shown in FIG. 4, the power control circuit 13 in one embodiment has a first comparison function 210x, a second comparison function 210y, and a third comparison function in order to realize the current ratio control function. It has 210z, a determination function 220, and a feedback control function 230.

The memory of the power control circuit 13 stores a look-up table (Look Up Table: LUT), a threshold voltage (V _th ), a reference voltage (V _ref ), etc., in which the value generated by the comparison function is associated with the current ratio. Remember. The threshold voltage is set lower than the reference voltage in consideration of ripple noise. The LUT will be described in detail later.

The various functions performed by the first comparison function 210x, the second comparison function 210y, the third comparison function 210z, the determination function 220, and the feedback control function 230 are power control circuits in the form of a program that can be executed by a computer. It is stored in the memory (or storage device 127) in 13. The power control circuit 13 is a processor that realizes the functions corresponding to each program by reading the programs corresponding to these various functions from the memory and executing the programs. In other words, the power control circuit 13 in the state where each program is read has a plurality of functions shown in the power control circuit 13 of FIG.

Although it has been described in FIG. 4 that these various functions are realized by a single power control circuit 13, a plurality of independent processors are combined to form a power control circuit 13, and each processor executes a program. The function may be realized by doing so. In other words, each of the above-mentioned functions may be configured as a program, and one processing circuit may execute each program, or a specific function may be implemented in a dedicated and independent program execution circuit. You may.

The power control circuit 13 receives _{the first voltage (V out_x} ) from the X-axis measuring instrument 12x by the first comparison function 210x. The power control circuit 13 produces a first comparison result (V _x ) by comparing the first voltage with the threshold voltage. The first comparison result is, for example, _{a signal corresponding to a truth value of 1 (V x} = 1) when the first voltage is equal to or higher than the threshold voltage, and a truth value when the first voltage is lower than the threshold voltage. Is a signal corresponding to 0 (V _{x = 0).} Note that "the first voltage is equal to or higher than the threshold voltage" corresponds to "a state in which charging of the X-axis capacitor bank 21x is completed (charging complete mode)", and "the first voltage is less than the threshold voltage" is It corresponds to "a state in which charging of the X-axis capacitor bank 21x is required (charging mode)". The power control circuit 13 that executes the first comparison function 210x is an example of a means for realizing the first comparison unit.

The power control circuit 13 receives _{the second voltage (V out_y} ) from the Y-axis measuring instrument 12y by the second comparison function 210y. The power control circuit 13 produces a second comparison result (V _y ) by comparing the second voltage with the threshold voltage. The second comparison result is, for example, _{a signal corresponding to a truth value of 1 (V y} = 1) when the second voltage is equal to or higher than the threshold voltage, and a truth value when the second voltage is lower than the threshold voltage. Is a signal corresponding to 0 (V _{y = 0).} "The second voltage is equal to or higher than the threshold voltage" corresponds to "a state in which charging of the Y-axis capacitor bank 21y is completed (charging complete mode)", and "the second voltage is less than the threshold voltage" is It corresponds to "a state in which charging of the Y-axis capacitor bank 21y is required (charging mode)". The power control circuit 13 that executes the second comparison function 210y is an example of a means for realizing the second comparison unit.

The power control circuit 13 receives a _{third voltage (V out_z} ) from the Z-axis measuring instrument 12z by the third comparison function 210z. The power control circuit 13 produces a third comparison result ( _Vz ) by comparing the third voltage with the threshold voltage. The third comparison result is, for example, _{a signal corresponding to a truth value of 1 (V z} = 1) when the third voltage is equal to or higher than the threshold voltage, and a truth value when the third voltage is lower than the threshold voltage. Is a signal corresponding to 0 (V _{z = 0).} Note that "the third voltage is equal to or higher than the threshold voltage" corresponds to "a state in which charging of the Z-axis capacitor bank 21z is completed (charging completion mode)", and "the third voltage is less than the threshold voltage" is It corresponds to "a state in which charging of the Z-axis capacitor bank 21z is required (charging mode)". The power control circuit 13 that executes the third comparison function 210z is an example of a means for realizing the third comparison unit.

The power control circuit 13 determines the current ratio by the determination function 220 based on the combination of the first comparison result, the second comparison result, and the third comparison result and the LUT. The power control circuit 13 generates three target currents (I _{limit_x} , I _{limit_y} , and I _{limit_z} ) according to the determined current ratio. The power control circuit 13 that executes the determination function 220 is an example of a means for realizing the determination unit.

The LUT is a correspondence table that associates the first combination with the second combination. The first combination is three output values (signals corresponding to each truth value) generated by the first comparison function 210x, the second comparison function 210y, and the third comparison function 210z. The second combination is the first ratio of the first current to the sum of the first current, the second current, and the third current output from the power supply 11, and the second of the second current to the sum. It is a combination of two ratios and a third ratio of the third current to the sum. As an alternative to the LUT, the memory is used for the comparison result by the comparison unit (the first comparison unit, the second comparison unit, and the third comparison unit) and for each of the plurality of amplifiers corresponding to the plurality of gradient magnetic field coils. Correspondence information corresponding to the ratio of the supplied current to the total current supplied to the plurality of amplifiers may be stored.

The power control circuit 13 uses the feedback control function 230 to generate a first current and a second current output from the power supply 11 using _{three target currents (I limit_x} , I _{limit_y} , and I _{limit_z).} , Performs feedback control for the third current. The power control circuit 13 that executes the feedback control function 230 is an example of a means for realizing the feedback control unit.

The feedback control function 230 includes a first PID control function 231x, a second PID control function 231y, a third PID control function 231z, a fourth comparison function 232x, a fifth comparison function 232y, and a third. It has a comparison function 232z, a fourth PID control function 233x, a fifth PID control function 233y, and a sixth PID control function 233z.

Hereinafter, in the power supply device 11, feedback processing relating to the output to the X-axis amplifier 22x (X-axis feedback processing), feedback processing relating to the output to the Y-axis amplifier 22y (Y-axis feedback processing), and output to the Z-axis amplifier 22z. Feedback processing (Z-axis feedback processing) will be described.

(X-axis feedback processing)
The power control circuit 13 receives _{the first voltage (V out_x} ) from the X-axis measuring instrument 12x by the first PID control function 231x. The power control circuit 13 executes feedback control regarding the first voltage by using the reference voltage and the first voltage. The power control circuit 13 generates a _{first correction current (I ref_x} ) as a result of the feedback control.

The power control circuit 13 generates a first reference current (i _{ref_x} ) by comparing the first correction current with the first target current (I _{limit_x) by the fourth comparison function 232x.} The first reference current becomes, for example, the first correction current (that is, i _{ref_x} = I _{ref_x} fourth PID control function 233x) when the first correction current is equal to or less than the first target current. When the correction current is larger than the first target current, the first target current (that is, _{iref_x} = I _{limit_x} ) is obtained.

The power control circuit 13 receives _{the first current (I out_x} ) from the X-axis measuring instrument 12x by the fourth PID control function 233x. The power control circuit 13 executes feedback control regarding the first current by using the first reference current and the first current. The power control circuit 13 generates a first correction amount for controlling the full bridge circuit as a result of the feedback control. The first correction amount is, for example, a drive signal to each of a plurality of switching elements in a full bridge circuit for supplying power to the X-axis amplifier 22x.

(Y-axis feedback processing)
The power control circuit 13 receives a _{second voltage (V out_y} ) from the Y-axis measuring instrument 12y as the second PID control function 231y. The power control circuit 13 executes feedback control regarding the second voltage by using the reference voltage and the second voltage. The power control circuit 13 generates a _{second correction current (I ref_y} ) as a result of the feedback control.

The power control circuit 13 generates a second reference current (i _{ref_y} ) by comparing the second correction current with the second target current (I _{limit_y) as the fifth comparison function 232y.} The second reference current is, for example, a second correction current (that is, i _{ref_y} = I _{ref_y} ) when the second correction current is equal to or less than the second target current, and the second correction current is the second target. When it is larger than the current, it becomes the second target current (that is, _{iref_y} = I _{limit_y} ).

The power control circuit 13 receives a _{second current (I out_y} ) from the Y-axis measuring instrument 12y by the fifth PID control function 233y. The power control circuit 13 executes feedback control regarding the second current by using the second reference current and the second current. The power control circuit 13 generates a second correction amount for controlling the full bridge circuit as a result of the feedback control. The second correction amount is, for example, a drive signal to each of the plurality of switching elements in the full bridge circuit for supplying power to the Y-axis amplifier 22y.

(Z-axis feedback processing)
The power control circuit 13 receives a _{third voltage (V out_z} ) from the Z-axis measuring instrument 12z as the third PID control function 231z. The power control circuit 13 executes feedback control regarding the third voltage by using the reference voltage and the third voltage. The power control circuit 13 generates a _{third correction current (I ref_z} ) as a result of the feedback control.

The power control circuit 13 generates a third reference current (i _{ref_z} ) by comparing the third correction current with the third target current (I _{limit_z) as the sixth comparison function 232z.} The third reference current is, for example, when the third correction current is equal to or less than the third target current, the third correction current is the third correction current (that is, i _{ref_z} = I _{ref_z} ), and the third correction current is the third target. When it is larger than the current, it becomes the third target current (that is, _{iref_z} = I _{limit_z} ).

The power control circuit 13 receives a _{third current (I out_z} ) from the Z-axis measuring instrument 12z by the sixth PID control function 233z. The power control circuit 13 executes feedback control regarding the third current by using the third reference current and the third current. The power control circuit 13 generates a third correction amount for controlling the full bridge circuit as a result of the feedback control. The third correction amount is, for example, a drive signal to each of a plurality of switching elements in the full bridge circuit for supplying power to the Z-axis amplifier 22z.

The power supply device 11 controls the full bridge circuit corresponding to the X-axis amplifier 22x by using the first correction amount by the PWM control circuit. Further, the power supply device 11 controls the full bridge circuit corresponding to the Y-axis amplifier 22y by using the second correction amount by the PWM control circuit. Further, the power supply device 11 controls the full bridge circuit corresponding to the Z-axis amplifier 22z by the PWM control circuit using the third correction amount. The power supply device 11 supplies current to the X-axis amplifier 22x, the Y-axis amplifier 22y, and the Z-axis amplifier 22z, respectively, by each of the above controls.

FIG. 5 is a flowchart showing a process executed by the power control circuit in one embodiment. Hereinafter, the processing of the current ratio control function by the power control circuit 13 will be described.

First, the magnetic resonance imaging device 100 reads the imaging protocol from the storage device 127 based on the imaging conditions input from the operator by the system control function 129a. The magnetic resonance imaging device 100 transmits an imaging protocol to the imaging control circuit 121 to control imaging of the subject P. At this time, the power control circuit 13 of the gradient magnetic field power supply 105 starts the operation of step S501 at the same time as the start of imaging of the subject P.

(Step S501)
_{The power control circuit 13 acquires the value of the first voltage (V out_x} ) from the X-axis measuring instrument 12x _{, acquires the value of the second voltage (V out_y} ) from the Y-axis measuring instrument 12y, and acquires the value of the second voltage (V out_y) from the Z-axis measuring instrument. The value of the third voltage (V _{out_z} ) is acquired from 12z.

(Step S502)
The power control circuit 13 determines whether or not a value is input to the first comparison result (V _{x ) (V x} = null?). If no value is entered in V _x , the process proceeds to step S503. If a _{value is input to V x} , the process proceeds to step S507.

(Step S503)
The power control circuit 13 substitutes x for the variable j, and the process proceeds to step S504. Due to this substitution, during the subsequent steps S504 to S506, the power control circuit 13 performs processing with _{V out_j} = V _{out_x} and V _j = V _x.

(Step S504)
The power control circuit 13 determines whether or not _{the first voltage (V out_x} ) is equal to _{or higher than the threshold voltage (V th} ) by the first comparison function 210x. If the first voltage is equal to or higher than the threshold voltage, the process proceeds to step S505. If the first voltage is less than the threshold voltage, the process proceeds to step S506.

When y is assigned to the variable j, the power control circuit 13 determines whether or not _{the second voltage (V out_y} ) is equal to _{or higher than the threshold voltage (V th) by the second comparison function 210y.} If the second voltage is equal to or higher than the threshold voltage, the process proceeds to step S505. If the second voltage is less than the threshold voltage, the process proceeds to step S506.

When z is assigned to the variable j, the power control circuit 13 determines whether or not _{the third voltage (V out_z} ) is equal to _{or higher than the threshold voltage (V th) by the third comparison function 210z.} If the third voltage is equal to or higher than the threshold voltage, the process proceeds to step S505. If the third voltage is less than the threshold voltage, the process proceeds to step S506.

(Step S505)
Since the first voltage is equal to or higher than the threshold voltage, the power control circuit 13 generates the first comparison result (V _x ) as “1”.

When y is assigned to the variable j, since the second voltage is equal to or higher than the threshold voltage, the power control circuit 13 generates the second comparison result (V _y ) as “1”.

When z is assigned to the variable j, since the third voltage is equal to or higher than the threshold voltage, the power control circuit 13 generates the third comparison result (V _z ) as “1”. After step S505, the process returns to step S502.

(Step S506)
Since the first voltage is less than the threshold voltage, the power control circuit 13 generates the first comparison result (V _x ) as “0”.

When y is assigned to the variable j, the second voltage is less than the threshold voltage, so the power control circuit 13 generates the second comparison result (V _y ) as “0”.

When z is assigned to the variable j, since the third voltage is less than the threshold voltage, the power control circuit 13 generates the third comparison result (V _z ) as “0”. After step S506, the process returns to step S502.

(Step S507)
The power control circuit 13 determines whether or not a value is input to the second comparison result (V _{y ) (V y} = null?). If no value is entered in V _y , the process proceeds to step S508. If a _{value is input to V y} , the process proceeds to step S509.

(Step S508)
The power control circuit 13 substitutes y for the variable j, and the process proceeds to step S504. Due to this substitution, during the subsequent steps S504 to S506, the power control circuit 13 performs processing with _{V out_j} = V _{out_y} and V _j = V _y.

(Step S509)
The power control circuit 13 determines whether or not a value is input to the third comparison result (V _{z ) (V z} = null?). If no value is entered in V _z , the process proceeds to step S510. _If a value is input to V z, the process proceeds to step S511.

(Step S510)
The power control circuit 13 substitutes z for the variable j, and the process proceeds to step S504. Due to this substitution, during the subsequent steps S504 to S506, the power control circuit 13 performs processing with _{V out_j} = V _{out_z} and V _j = V _z.

(Step S511)
The power control circuit 13 uses the determination function 220 to output an output corresponding to the first combination of the first _{comparison result (V x} ), the second comparison result (V _y ), and the third comparison result (V _{z). Read} the modes (I limit_x, I _{limit_y} and I _{limit_z} ) from the LUT.

After step S511, the values of the first comparison result (V _x ), the second comparison result (V _y ), and the third comparison result (V _z ) are reset, and the process ends. "The value of the first comparison result is reset _{" corresponds to "V x} = null", and "the value of the second comparison result is reset _{" corresponds to "V y} = null". "The value of the third comparison result is reset _{" corresponds to "V z} = null". The above processing is repeatedly executed until all of the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z are in the charge completion mode.

The processes from step S502 to step S510 may be processed in parallel. Further, step S511 is performed by the determination function 220 when the first combination of the first _{comparison result (V x} ), the second comparison result (V _y ), and the third comparison result (V _{z) is prepared.} Processing is performed.

FIG. 6 is a diagram showing a LUT in one embodiment. For example, as shown in FIG. 6, in the LUT 600 according to one embodiment, the first combination of _{V x} , V _y , and V _{z corresponds to the second combination of I limit_x} , I _{limit_y} , and I _{limit_z} . It is attached. The first combination is three output values (signals corresponding to each truth value) generated by the first comparison function 210x, the second comparison function 210y, and the third comparison function 210z, respectively. The second combination is the first ratio of the first current to the sum (total current amount) of the first current, the second current, and the third current output from the power supply 11, and the second with respect to the transmission flow rate. The second ratio of the current of 2 and the third ratio of the third current to the transmission flow rate are represented by an integer percentage (%), respectively.

Since the combination 601 is (V _x , V _y , V _z ) = (1, 1, 1), the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z are all in the charge completion mode. It means that there is. Since the combination 602 corresponding to the combination 601 is (I _{limit_x} , I _{limit_y} , I _{limit_z} ) = (33, 33, 33), the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z On the other hand, it means that almost the same amount of current is allocated to each.

Since the combination 603 is (V _x , V _y , V _z ) = (1,1,0), it means that the X-axis capacitor bank 21x and the Y-axis capacitor bank 21y are in the charge completion mode, and the Z-axis. It means that the capacitor bank 21z is in the charging mode. The combination 604 corresponding to the combination 603 is (I _{limit_x} , I _{limit_y} , I _{limit_z} ) = (4,4,92), which means that the amount of current is preferentially allocated to the Z-axis capacitor bank 21z.

Since the combination 605 is (V _x , V _y , V _z ) = (1, 0, 1), it means that the X-axis capacitor bank 21x and the Z-axis capacitor bank 21z are in the charge completion mode, and the Y-axis. It means that the capacitor bank 21y is in the charging mode. The combination 606 corresponding to the combination 605 is (I _{limit_x} , I _{limit_y} , I _{limit_z} ) = (4,92,4), which means that the amount of current is preferentially allocated to the Y-axis capacitor bank 21y.

Since the combination 607 is (V _x , V _y , V _z ) = (1,0,0), it means that the X-axis capacitor bank 21x is in the charge completion mode, and the Y-axis capacitor banks 21y and the Z-axis. It means that the capacitor bank 21z is in the charging mode. The combination 608 corresponding to the combination 607 has (I _{limit_x} , I _{limit_y} , I _{limit_z} ) = (4,48,48), and preferentially sets the current amount to the Y-axis capacitor bank 21y and the Z-axis capacitor bank 21z. Means to allocate.

In the combination 609, (V _x , V _y , V _z ) = (0, 0, 0), so that the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z are all in the charging mode. Means that. Since the combination 610 corresponding to the combination 609 is (I _{limit_x} , I _{limit_y} , I _{limit_z} ) = (33, 33, 33), the X-axis capacitor bank 21x, the Y-axis capacitor bank 21y, and the Z-axis capacitor bank 21z On the other hand, it means that almost the same amount of current is allocated to each.

As described above, the magnetic resonance imaging apparatus 100 according to the embodiment includes a plurality of gradient magnetic field coils that receive power supply to generate a gradient magnetic field of a plurality of axes, and a gradient magnetic field power supply that supplies power. The gradient magnetic field power supply includes a plurality of amplifiers connected to a plurality of gradient magnetic field coils, a power supply device that supplies current to the plurality of amplifiers, a measuring instrument that measures the voltage applied to the plurality of amplifiers, and a voltage. Based on this, it has a power control circuit that controls the current supplied from the power supply to the amplifier. The power control circuit is composed of a comparison unit that compares the voltage applied to the plurality of amplifiers with the threshold voltage, the comparison result of the comparison unit, and the current supplied to each of the plurality of amplifiers corresponding to the plurality of gradient magnetic field coils. It includes a memory having correspondence information that associates with the ratio of the currents supplied to the plurality of amplifiers to the total sum. As a result, the magnetic resonance imaging apparatus 100 can control the allocation of the output current from the power supply using software.

Further, the magnetic resonance imaging apparatus 100 according to the present embodiment includes an X-axis gradient magnetic field coil, a Y-axis gradient magnetic field coil, a Z-axis gradient magnetic field coil, and a gradient magnetic field power supply. The gradient magnetic field power supply includes a power supply device, a measuring instrument, and a power control circuit. The power supply supplies the first current, the second current, and the third to three amplifiers connected to the X-axis gradient magnetic field coil, the Y-axis gradient magnetic field coil, and the Z-axis gradient magnetic field coil, respectively. Supply current and each. The measuring instrument measures the first voltage corresponding to the first current, the second voltage corresponding to the second current, and the third voltage corresponding to the third current, respectively. The power control circuit uses the first voltage, the second voltage, and the third voltage to control the first current, the second current, and the third current. The power control circuit includes a first comparison unit, a second comparison unit, a third comparison unit, a memory, and a determination unit. The first comparison unit produces a first comparison result by comparing the first voltage with the threshold voltage. The second comparison unit produces a second comparison result by comparing the second voltage with the threshold voltage. The third comparison unit produces a third comparison result by comparing the third voltage with the threshold voltage. The memory is a first combination of three comparison results generated by the first comparison unit, the second comparison unit, and the third comparison unit, respectively, and the first current, the second current, and the third. A lookup table that associates the first ratio of the first current to the sum of the currents, the second ratio of the second current to the sum, and the second combination of the third ratio of the third current to the sum. Remember. The determination unit determines the second combination based on the combination of the first comparison result, the second comparison result, and the third comparison result and the look-up table. The power control circuit controls the power supply according to the determined second combination. As a result, the magnetic resonance imaging apparatus 100 can control the allocation of the output current from the power supply using software.

Further, the magnetic resonance imaging apparatus 100 executes feedback control on the first current, the second current, and the third current by using the determined second combination in the power control circuit. It further has a feedback control unit. As a result, the magnetic resonance imaging apparatus 100 can control the allocation of the output current from the power supply using software.

According to at least one embodiment described above, the allocation of output current from the power supply can be controlled by using software.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

12 Measuring instrument 100 Magnetic resonance imaging device 101 Static magnetic field magnet 103 Tilt magnetic field coil 105 Tilt magnetic field power supply 107 Sleeper 115 Transmit coil 117 Receive coil 210 x First comparison function 210y Second comparison function 210z Third comparison function 230 Feedback control function 232x 4th comparison function 232y 5th comparison function 232z 6th comparison function 600 LUT

Claims (3)

Multiple gradient magnetic field coils that receive power to generate a multi-axis gradient magnetic field,
It is equipped with a gradient magnetic field power supply that supplies the power.
The gradient magnetic field power supply
A plurality of amplifiers connected to the plurality of gradient magnetic field coils, respectively,
A power supply that supplies current to the plurality of amplifiers,
A measuring instrument that measures the voltage applied to the amplifier,
It has a power control circuit that controls the current supplied from the power supply device to the amplifier based on the voltage.
The power control circuit
A comparison unit that compares the voltage applied to the amplifier with the threshold voltage,
A memory having correspondence information for associating the comparison result by the comparison unit with the ratio of the current supplied to each of the plurality of amplifiers corresponding to the plurality of gradient magnetic field coils to the total current supplied to the plurality of amplifiers. When,
A magnetic resonance imaging device equipped with. It includes an X-axis gradient magnetic field coil, a Y-axis gradient magnetic field coil, a Z-axis gradient magnetic field coil, and a gradient magnetic field power supply.
The gradient magnetic field power supply
The first current, the second current, and the third current are applied to the three amplifiers connected to the X-axis gradient magnetic field coil, the Y-axis gradient magnetic field coil, and the Z-axis gradient magnetic field coil, respectively. With a power supply that supplies each
A measuring instrument that measures a first voltage corresponding to the first current, a second voltage corresponding to the second current, and a third voltage corresponding to the third current, respectively.
A power control circuit that controls the first current, the second current, and the third current by using the first voltage, the second voltage, and the third voltage. And have
The power control circuit
A first comparison unit that generates a first comparison result by comparing the first voltage and the threshold voltage.
A second comparison unit that generates a second comparison result by comparing the second voltage with the threshold voltage.
A third comparison unit that generates a third comparison result by comparing the third voltage with the threshold voltage.
The first combination of the three comparison results generated by the first comparison unit, the second comparison unit, and the third comparison unit, and the first current, the second current, and the second current. With a second combination of the first ratio of the first current to the sum of the third currents, the second ratio of the second current to the sum, and the third ratio of the third current to the sum. The memory that stores the lookup table associated with
It has a determination unit that determines the second combination based on the combination of the first comparison result, the second comparison result, and the third comparison result and the look-up table.
The power control circuit is a magnetic resonance imaging device that controls the power supply according to the determined second combination. The power control circuit uses the determined second combination to provide a feedback control unit that executes feedback control on the first current, the second current, and the third current. The magnetic resonance imaging apparatus according to claim 2, further comprising.

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