JP2009240526A - Mri apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MRI apparatus can produce an electric source part with a small setting area. <P>SOLUTION: An electric storage part 32 includes a volume can store the same electric power as all power consumption APtotal that DC/AC power conversion means 34 and gradient coils 14 consume or more. Then, the maximum power consumption Pmax can be supplied to the AC/DC power conversion part 31 by supplying electric power from the electric storage part 32 even if AC/DC power conversion part 31 can output only the same direct current power Pdc_ave as the average power consumption Pave. Therefore, the rated power of an insulating transformer 31a and a commutator 31b can be diminished. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an MRI apparatus having a power supply unit for supplying gradient coil AC power to a gradient coil.

MRI (Magnetic
The Resonance Imaging system includes a converter that converts AC power into DC power in a power supply unit (see Patent Document 1).
Table 2005-08814

  In the method of the above literature, a converter having the same rated power as the maximum value of power consumption (maximum power consumption) or a converter having a rated power larger than the maximum power consumption is required. Therefore, a large converter with a large rated power is required, and there is a problem that the installation area of the power supply unit becomes large.

  An object of this invention is to provide the MRI system which can implement | achieve a power supply part with a small installation area in view of said situation.

The MRI apparatus of the present invention that solves the above problems is
An MRI apparatus having a gradient coil and a power supply unit for supplying gradient coil AC power to the gradient coil at each repetition time of a data collection period,
The power supply unit is
A first power converter that converts input AC power from an AC power supply source into DC power and outputs the DC power;
A power storage unit that stores the DC power; and a second power conversion unit that extracts DC power from the power storage unit and converts the extracted DC power into the gradient coil AC power;
Have
The power storage unit has a capacity necessary to store the power consumed by the second power conversion unit and the gradient coil during the repetition time,
The second power conversion unit extracts DC power from the power storage unit during the repetition time,
The first power conversion unit replenishes the power storage unit with the DC power extracted from the power storage unit during the repetition time during the repetition time.

  In the present invention, the power storage unit has a capacity necessary for storing the power consumed by the second power conversion unit and the gradient coil during the repetition time. Therefore, a small power converter having a small rated power can be used as the first power conversion unit, and the installation area of the power supply unit can be reduced.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention.

1. First Embodiment FIG. 1 is a perspective view of an MRI (Magnetic Resonance Imaging) system 100 according to a first embodiment of the present invention.

  The MRI system 100 includes an MRI apparatus 11 and a control device 21 that controls the MRI apparatus 11. The MRI apparatus 11 is installed in the MRI room 10, and the control apparatus 21 is installed in the monitor room 20.

  The MRI apparatus 11 has a gradient coil group 14. The gradient coil group 14 includes three gradient coils 14X, 14Y, and 14Z (see FIG. 2 described later).

  The control device 21 includes an operation unit 22 and a cabinet 23.

  The cabinet 23 supplies power to the MRI apparatus 11 and processes MR signals received by a receiving coil (not shown). The cabinet 23 includes a gradient coil power supply unit 24 and a power supply control unit 40.

  The gradient coil power supply unit 24 supplies power to the gradient coil group 14 of the MRI apparatus 11. The gradient coil power supply unit 24 receives AC power from the AC power supply source 20 a of the monitor room 20, and converts the received AC power into gradient coil AC power for driving the gradient coil group 14. The power supply control unit 40 controls the operation of the gradient coil power supply unit 24. A specific role of the power control unit 40 will be described later.

  FIG. 2 is a diagram specifically showing the gradient coil power supply unit 24, the power supply control unit 40, and the gradient coil group 14.

  The gradient coil group 14 includes an X-axis gradient coil 14X, a Y-axis gradient coil 14Y, and a Z-axis gradient coil 14Z.

  The gradient coil power supply 24 includes an AC / DC power conversion unit 31, a power storage unit 32, a discharge unit 33, and DC / AC power conversion means 34.

  The AC / DC power conversion unit 31 receives the input AC power Pac_in from the AC power supply source 20a, and converts the input AC power Pac_in into DC power Pdc. The AC / DC power conversion unit 31 includes an insulating transformer 31a and a rectifier 31b. The insulating transformer 31a receives the input AC power Pac_in from the AC power supply source 20a, and converts the input AC power Pac_in into output AC power Pac_t. The rectifier 31b converts the output AC power Pac_t from the insulating transformer 31a into DC power Pdc.

  The DC power Pdc output from the rectifier 31 b is stored in the power storage unit 32 or supplied to the DC / AC power conversion means 34.

  The power storage unit 32 stores the DC power Pdc output from the rectifier 31b. In the present embodiment, the power storage unit 32 uses a capacitor having a capacitance C of several farads. As a capacitor having a capacitance C of several farads, for example, an electric double layer capacitor can be used.

  The discharge part 33 is for discharging the electric charge accumulated in the power storage part 32 during the shutdown period Tsd (see FIG. 3A). The discharge unit 33 includes a discharge resistor 33a and a switch 33b. When the switch 33b is turned on, the discharge resistor 33a is connected to the power storage unit 32 in parallel, so that the charge accumulated in the power storage unit 32 is discharged.

  The DC / AC power conversion means 34 receives the DC power Pdc from the rectifier 31 b and / or the DC power Pdc_cap from the power storage unit 32, and the received DC power Pdc and / or DC power Pdc_cap is supplied to the gradient coil group 14. Convert to AC power. The DC / AC power conversion means 34 has three DC / AC power conversion units 35X, 35Y, and 35Z.

  The DC / AC power converter 35X converts the DC power Pdc and / or the DC power Pdc_cap into X-axis gradient coil AC power Pac_Gx supplied to the X-axis gradient coil 14X. The DC / AC power conversion unit 35Y converts the DC power Pdc and / or the DC power Pdc_cap into Y-axis gradient coil AC power Pac_Gy supplied to the Y-axis gradient coil 14Y. The DC / AC power conversion unit 35Z converts the DC power Pdc and / or the DC power Pdc_cap into the Z-axis gradient coil AC power Pac_Gz supplied to the Z-axis gradient coil 14Z.

  The DC / AC power conversion unit 35 </ b> X includes an inverter 36 and a filter 37. The inverter 36 receives the DC power Pdc and / or DC power Pdc_cap, and converts the received DC power Pdc and / or DC power Pdc_cap into AC power Pac_inv. The filter 37 filters the AC power Pac_inv from the inverter 36, and outputs the filtered AC power Pac_inv as the X-axis gradient coil AC power Pac_Gx. The X-axis gradient coil 14X generates a gradient magnetic field in the X-axis direction by being supplied with the X-axis gradient coil AC power Pac_Gx. The combination SetX of the DC / AC power converter 35X and the gradient coil 14X is provided for generating a gradient magnetic field in the X-axis direction.

  The structure of the DC / AC power conversion units 35Y and 35Z is the same as that of the DC / AC power conversion unit 35X, and a detailed description of the DC / AC power conversion units 35Y and 35Z will be omitted. A combination SetY of the DC / AC power converter 35Y and the Y-axis gradient coil 14Y is provided to generate a gradient magnetic field in the Y-axis direction. The combination SetZ of the DC / AC power converter 35Z and the Z-axis gradient coil 14Z is provided for generating a gradient magnetic field in the Z-axis direction.

  The power supply control unit 40 controls the timing at which the DC / AC power conversion means 34 extracts power from the rectifier 31 b and / or the power storage unit 32. Further, the power supply control unit 40 controls on / off of the switch 33b of the discharge unit 33.

  FIG. 3 is a diagram illustrating an example of a time schedule of the MRI system 100.

  The MRI system 100 has a power-on period Tpo, an imaging period Tim, and a shutdown period Tsd (see FIG. 3A).

  The power-on period Tpo is a period for starting up the MRI system 100. The imaging period Tim is a period during which the subject 12 (see FIG. 1) is imaged. The shutdown period Tsd is a period for shutting down the MRI system 100.

  The imaging period Tim has a pulse sequence period Tps in which the pulse sequence is executed. Each pulse sequence period Tps has a preparation period Tprep and a data collection period Tdata (see FIG. 3B). The preparation period Tprep is a period for transmitting a preceding pulse to the subject 12 before collecting data from the subject 12. The data collection period Tdata is a period for collecting data from the subject 12.

  In the data collection period Tdata, data is collected for each repetition time TR (see FIG. 3C). In each repetition time TR, a data collection pulse sequence for collecting data is executed. An example of a data acquisition pulse sequence executed at each repetition time TR is shown in FIG.

  FIG. 4 is a graph showing an example of a time change of the power consumption Pc consumed by the DC / AC power conversion means 34 and the gradient coil group 14 during each repetition time TR.

  In the present embodiment, the DC / AC power conversion means 34 extracts power from the rectifier 31b and / or the power storage unit 32 during the repetition time TR, and converts the extracted power into gradient coil AC power Pac_Gx, Pac_Gy, and Pac_Gz. To do. The gradient coils 14X, 14Y, and 14Z apply gradient pulses by being supplied with gradient coil AC power Pac_Gx, Pac_Gy, and Pac_Gz. Therefore, power is consumed by the DC / AC power conversion means 34 and the gradient coil group 14 during each repetition time TR.

  The total power consumption APtotal consumed by the DC / AC power conversion means 34 and the gradient coil group 14 during the repetition time TR is the area of the hatched portion. The total power consumption APtotal is expressed by the following equation.

APtotal = APx + APy + APz (1)
Here, APx is the power consumed by the DC / AC power converter 35X and the gradient coil 14X during the repetition time TR. APy is the power consumed by the DC / AC power converter 35Y and the gradient coil 14Y during the repetition time TR. APz is power consumed by the DC / AC power converter 35Z and the gradient coil 14Z during the repetition time TR.

  The power consumption Pc does not have a constant value during the repetition time TR, but varies greatly with time t. In periods T1, T3, T5, and T7, power consumption Pc is smaller than the average value of power consumption Pc (hereinafter referred to as “average power consumption”) Pave, but in periods T2, T4, and T6, power consumption Pc is larger than the average power consumption Pave. During the period T6, the power consumption Pc reaches a maximum value (hereinafter referred to as “maximum power consumption”) Pmax. The power storage unit 32 has a capacity capable of storing the same power as the total power consumption APtotal or more. The DC / AC power conversion means 34 takes out the power Etotal corresponding to the total power consumption APtotal from the rectifying unit 31b and / or the power storage unit 32 during the repetition time TR. This electric power Etotal is expressed by the following equation.

Etotal = Ex + Ey + Ez (2)
Here, Ex is the total power that the DC / AC power conversion unit 35X extracts from the rectification unit 31b and / or the power storage unit 32 during the repetition time TR. Ey is the total power that DC / AC power conversion unit 35Y takes out from rectification unit 31b and / or power storage unit 32 during repetition time TR. Ez is the total power that the DC / AC power conversion unit 35Z extracts from the rectification unit 31b and / or the power storage unit 32 during the repetition time TR.

  On the other hand, the rectifier 31b replenishes the power storage unit 32 with the power extracted from the power storage unit 32 in the power Etotal (see Expression (2)) during the repetition time TR. Therefore, since the stored energy of the power storage unit 32 returns to the original energy value during the repetition time TR, the power storage unit 32 supplies the power required by the DC / AC power conversion means 34 even during the next repetition time TR. Can be supplied. As described above, the power storage unit 32 has a capacity capable of storing the same power as the total power consumption APtotal consumed by the DC / AC power conversion means 34 and the gradient coil group 14 or more. . Therefore, the power storage unit 32 can supply the DC / AC power conversion means 34 with the power consumed by the DC / AC power conversion means 34 and the gradient coil group 14 during the repetition time TR. As a result, even if the power Pdc output from the AC / DC power converter 31 is smaller than the maximum power consumption Pmax, necessary power can be supplied to the DC / AC power converter 34 and the gradient coil group 14. Therefore, the small insulating transformer 31a and the rectifier 31b can be used, and the occupied area of the AC / DC power converter 31 can be reduced. In order to explain the reason why such an effect is obtained, a power supply unit that includes the AC / DC power conversion unit 31 but does not include the power storage unit 32 will be considered below.

  FIG. 5 is a diagram illustrating a power supply unit 24 ′ that includes the AC / DC power conversion unit 31 but does not include the power storage unit 32.

  Unlike the power supply unit 24 shown in FIG. 2, the power supply unit 24 ′ shown in FIG. 5 does not have the power storage unit 32, but the other components are the same as those of the power supply unit 24 shown in FIG. 2.

  In the power supply unit 24 ′ in FIG. 5, the DC power Pdc from the rectifier 31 b is directly supplied to the DC / AC power conversion means 34. Therefore, when the rectifier 31b can output only the DC power Pdc_ave having the same value as the average power consumption Pave (see the vertical axis Pdc on the right side of the graph in FIG. 4), the DC / AC power is output during the periods T2, T4, and T6. Sufficient power cannot be supplied to the conversion means 34 and the gradient coil group 14. Therefore, when the power supply unit 24 ′ shown in FIG. 5 is used, in order to supply sufficient power to the DC / AC power conversion unit 34 and the gradient coil group 14, the AC / DC power conversion unit 31 has a maximum power consumption. The DC power Pdc_max having the same value as Pmax (see the vertical axis Pdc on the right side of the graph of FIG. 4) needs to be configured. In order to realize such an AC / DC power conversion unit 31, it is conceivable to use an insulating transformer 31a and a rectifier 31b having a large rated power NPR. As the rated power NPR of the insulating transformer 31a and the rectifier 31b is increased, the AC / DC power converter 31 can supply a larger DC power Pdc to the DC / AC power converter 34. Therefore, by setting the rated power NPR of the isolation transformer 31a and the rectifier 31b to the rated power NPR_max having the same value as the DC power Pdc_max (see the vertical axis NPR on the right side of the graph in FIG. 4), the AC / DC power conversion unit 31 DC power Pdc_max can be output. However, the volume of the insulation transformer 31a and the rectifier 31b increases as the rated power value increases. Therefore, when the insulating transformer 31a and the rectifier 31b have the rated power NPR_max, there is a problem that the volumes of the insulating transformer 31a and the rectifier 31b are increased, and the power supply unit 24 'is increased in size.

  Therefore, in the present embodiment, the power supply unit 24 includes a power storage unit 32 so that the power supply unit 24 can be downsized (see FIG. 2). By providing such a power storage unit 32, the power supply unit 24 can be reduced in size. The reason for this will be described with reference to FIG.

The total power Eac that the DC / AC power conversion means 34 takes out from the rectifying unit 31b and / or the power storage unit 32 during the repetition time TR is expressed by the following equation.
Eac = APtotal (3)

On the other hand, the total power Ex output by the AC / DC power conversion unit 31 during the repetition time TR is expressed by the following equation.
Ex = Pdc · TR (4)

In the present embodiment, as described above, the AC / DC power conversion unit 31 replenishes the power storage unit 32 with the power extracted from the power storage unit by the DC / AC power conversion unit 34 during the repetition time TR. In order to be able to perform such replenishment, the total power Eac (see equation (3)) and Ex (see equation (4)) need only satisfy the following relational expression.
Ex = Eac (5)

From equation (5), Pdc is the following value of the DC power output by the AC / DC power converter 31.
Pdc = APtotal / TR
= Pave (Pave: average power consumption (see FIG. 4))
= Pdc_ave (6)

  From equation (6), if the AC / DC power conversion unit 31 can output the same DC power Pdc_ave as the average power consumption Pave, the AC / DC power conversion unit 31 calculates the total power extracted from the power storage unit 32. It can be seen that the power storage unit 32 can be replenished. The power storage unit 32 has a capacity capable of storing the same power as the total power consumption APtotal consumed by the DC / AC power conversion means 34 and the gradient coil group 14 or more. Therefore, even if the AC / DC power conversion unit 31 can output only the same DC power Pdc_ave as the average power consumption Pave, by supplying power from the power storage unit 32, the AC / DC power conversion unit 31 has the maximum power. The power consumption Pmax can be supplied. For this reason, the insulated transformer 31a and the rectifier 31b only have to have the same rated power NPR_ave as the average power consumption Pave, and the rated power NPR_max is unnecessary. Therefore, the rated power of the insulation transformer 31a and the rectifier 31b can be reduced, and the insulation transformer 31a and the rectifier 31b can be downsized. Further, since the rated power of the insulating transformer 31a can be reduced, the power capacity necessary for the AC power supply source 20a that supplies AC power to the insulating transformer 31a can also be reduced.

  Next, how the stored energy of the power storage unit 32 changes during the repetition time TR when the AC / DC power conversion unit 31 outputs the DC power Pdc_ave will be described.

  FIG. 6 is an explanatory diagram showing how the stored energy of the power storage unit 32 changes during the repetition time TR when the AC / DC power conversion unit 31 outputs the DC power Pdc_ave.

  FIG. 6A is a diagram schematically showing the power-on period Tpo, the imaging period Tim, and the shutdown period Tsd in FIG. FIG. 6B is a graph of the power consumption Pc shown in FIG. FIG. 6C shows a curve EC <b> 1 representing the time change of the energy Ecap stored in the power storage unit 32. In FIG. 6C, it is assumed that the maximum energy that can be stored by the power storage unit 32 is Emax, and the storage energy Ecap of the power storage unit 32 is Ecap = E1 at the start time ts of the repetition time TR.

  In the periods T2, T4, and T6, the DC power Pdc_ave output from the AC / DC power converter 31 is smaller than the power consumption Pc (see FIG. 6B). Therefore, in periods T2, T4, and T6, the stored energy Ecap of the power storage unit 32 decreases (see FIG. 6C).

  On the other hand, in the periods T1, T3, T5, and T7, the DC power Pdc_ave output from the AC / DC power converter 31 is larger than the power consumption Pc (see FIG. 6B). Therefore, in the periods T1, T3, T5, and T7, the stored energy Ecap of the power storage unit 32 increases (see FIG. 6C).

  However, since Pdc_ave · TR = APtotal (see equation (6)), the total power extracted from the power storage unit 32 and the total power replenished to the power storage unit 32 are equal during the repetition time TR. Therefore, in the repetition time TR, the increase amount of the stored energy Ecap of the power storage unit 32 is equal to the decrease amount of the stored energy Ecap of the power storage unit 32. For this reason, the stored energy Ecap of the power storage unit 32 at the end time te of the repetition time TR becomes Ecap = E1 similarly to the start time ts. Therefore, during the repetition time TR, the AC / DC power conversion unit 31 can replenish the power taken out from the power storage unit 32 by the DC / AC power conversion unit 34, and the power storage unit also in the next repetition time TR. 32 can supply power to the DC / AC power conversion means 31 and the gradient coil group 14. In the above description, the AC / DC power conversion unit 31 supplements the power storage unit 32 with the same power as the power extracted from the power storage unit 32 during the repetition time TR. However, the AC / DC power conversion unit 31 may supplement the power storage unit 32 with power larger than the power extracted from the power storage unit 32.

  Note that, as described with reference to FIG. 6, in the present embodiment, since the power storage unit 32 is replenished with power during each repetition time TR, the power storage is performed even at the end time te of the last repetition time TR. The stored energy Ecap of the unit 32 is Ecap = E1. Therefore, even when the pulse sequence period Tps ends, the stored energy E1 is stored in the power storage unit 32. After the end of the pulse sequence period Tps, the stored energy E1 stored in the power storage unit 32 becomes unnecessary, and the charge accumulated in the power storage unit 32 is discharged. In order to perform this discharge, a shutdown period Tsd (see FIG. 6A) is provided. In the shutdown period Tsd, the power storage unit 32 is discharged as follows.

  FIG. 7 is a graph showing changes in the stored energy Ecap of the power storage unit 32 during the shutdown period Tsd.

  At time t1 of the shutdown period Tsd, the power supply control unit 40 (see FIG. 2) sends a control signal Sc so that the DC / AC power conversion means 34 takes out the stored energy of the power storage unit 32. Therefore, the DC / AC power conversion means 34 converts the power from the power storage unit 32 into gradient coil AC power Pac_Gx, Pac_Gy, and Pac_Gz. The gradient coil AC powers Pac_Gx, Pac_Gy, and Pac_Gz are supplied to the gradient coils 14X, 14Y, and 14Z, respectively. Therefore, the coil currents Icoil_x, Icoil_y, and Icoil_z flow through the gradient coils 14X, 14Y, and 14Z, respectively, and as a result, the stored energy Ecap of the power storage unit 32 decreases. As the stored energy Ecap decreases, the voltage Vcap (see FIG. 2) across the power storage unit 32 gradually decreases, and Vcap reaches the operating limit voltage Vlimit of the inverter 36 (time t2). When the voltage Vcap of the power storage unit 32 reaches the operation limit voltage Vlimit of the inverter 36, the operation of the inverter 36 is stopped. Therefore, the inverter 36 cannot convert the stored energy Er remaining in the power storage unit 32 into the AC power Pac_inv. Therefore, in order to discharge the stored energy Er remaining in the power storage unit 32, the power supply control unit 40 supplies an ON signal Son to the switch 33b of the discharge unit 33 (see FIG. 2). The switch 33b is turned on in response to the on signal Son. Since the switch 33b is turned on, the discharge resistor 33a is connected to the power storage unit 32 in parallel. Therefore, the stored energy Er remaining in the power storage unit 32 is supplied to the discharge resistor 33a and consumed by the discharge resistor 33a (time t3). In this way, all the stored energy E1 of the power storage unit 32 can be discharged during the shutdown period Tsd.

  In the first embodiment, the combination SetX of the DC / AC power conversion unit 35X and the gradient coil 14X, the combination SetY of the DC / AC power conversion unit 35Y and the gradient coil 14Y, and the DC / AC power conversion unit 35Z. And a combination SetZ of the gradient coil 14Z. However, it is not necessary to provide these three combinations SetX, SetY, and SetZ, and it is possible to provide only one combination or only two of these three combinations.

2. Second Embodiment In describing the second embodiment, differences from the first embodiment will be described.

  FIG. 8 is a diagram showing the gradient coil power supply 24 and the gradient coil group 14 in the second embodiment.

  The gradient coil power supply 24 includes an insulating transformer 241, an X-axis conversion unit 242X, a Y-axis conversion unit 242Y, and a Z-axis conversion unit 242Z.

  The insulation transformer 241 receives the input AC power Pac_in from the AC power supply source 20a, and converts the input AC power Pac_in into an X-axis output AC power Pac_X, a Y-axis output AC power Pac_Y, and a Z-axis output AC power Pac_Z.

  The X-axis conversion unit 242X converts the X-axis output AC power Pac_X into X-axis gradient coil AC power Pac_Gx for driving the X-axis gradient coil 14X. The Y-axis conversion unit 242Y converts the Y-axis output AC power Pac_Y into Y-axis gradient coil AC power Pac_Gy for driving the Y-axis gradient coil 14Y. The Z-axis conversion unit 242Z converts the Z-axis output AC power Pac_Z into Z-axis gradient coil AC power Pac_Gz for driving the Z-axis gradient coil 14Z.

  The X-axis conversion unit 242X includes a rectifier 243, a power storage unit 244, a discharge unit 245, and a DC / AC power conversion unit 246.

  The rectifier 243 converts the X-axis output AC power Pac_X of the isolation transformer 241 into DC power Pdc_X. The DC power Pdc_X is supplied to the power storage unit 245 and the DC / AC conversion unit 246.

  The power storage unit 244 stores the DC power Pdc_X output from the rectifier 243. The power storage unit 244 has a sufficiently large capacitance C (capacitance of several farads) so that the total power consumption APtotal (see FIG. 4) can be stored.

  The discharge unit 245 is provided to discharge the electric charge accumulated in the power storage unit 244 during the shutdown period Tsd (see FIG. 7) of the MRI apparatus 11.

  The DC / AC power conversion unit 246 includes an inverter 247 and a filter 248. The inverter 247 receives the DC power Pdc_x and / or Pdc_cap from the rectifier 243 and / or the power storage unit 244, and converts the DC power Pdc_x and / or Pdc_cap into AC power Pac_inv. The filter 248 filters the AC power Pac_inv from the inverter 247 and outputs the filtered AC power Pac_inv as the X-axis gradient coil AC power Pac_Gx. The X-axis gradient coil 14X generates a gradient magnetic field in the X-axis direction by being supplied with the X-axis gradient coil AC power Pac_Gx. A combination SetX of the X-axis converter 242X and the gradient coil 14X is provided to generate a gradient magnetic field in the X-axis direction.

  Since the structures of the Y-axis conversion unit 242Y and the Z-axis conversion unit 242Z are the same as those of the X-axis conversion unit 242X, detailed description of the Y-axis conversion unit 242Y and the Z-axis conversion unit 242Z will be omitted. A combination SetY of the Y-axis converter 242Y and the gradient coil 14Y is provided to generate a gradient magnetic field in the Y-axis direction. The combination SetZ of the Z-axis conversion unit 242Z and the gradient coil 14Z is provided to generate a gradient magnetic field in the Z-axis direction.

  In the first embodiment (see FIG. 2), each of the rectifier 31b, the power storage unit 32, and the discharge unit 33 is provided, but in the second embodiment, the rectifier 243, the power storage unit 244, and The discharge unit 245 is provided for each of the gradient coils 14X, 14Y, and 14Z. As described above, the gradient coil power supply unit 24 is not limited to the structure shown in FIGS. 2 and 8 and can have various structures as long as power can be supplied to the power storage unit 244 (power storage unit 32). .

  In the second embodiment, the combination SetX of the X-axis conversion unit 242X and the gradient coil 14X, the combination SetY of the Y-axis conversion unit 242Y and the gradient coil 14Y, the Z-axis conversion unit 242Z and the gradient coil 14Z A combination SetZ is provided. However, it is not necessary to provide these three combinations SetX, SetY, and SetZ, and it is possible to provide only one combination or only two of these three combinations.

  In the first and second embodiments, the power storage units 32 and 244 have a capacitance of several farads. However, as long as the rectifier can replenish the total power extracted from power storage units 32 and 244 during repetition time TR, the capacitance of power storage units 32 and 244 may be larger or smaller than a few farads. Good.

1 is a perspective view of an MRI (Magnetic Resonance Imaging) system 100 according to a first embodiment of the present invention. 4 is a diagram illustrating a connection relationship among a gradient coil power supply unit 24, a power supply control unit 40, and a gradient coil group 14. FIG. It is a figure which shows an example of the time schedule of the MRI system. It is a graph showing an example of the time change of the power consumption Pc consumed by the DC / AC power conversion means 34 and the gradient coil group 14 between each repetition time TR. It is a figure which shows the power supply part 24 'provided with the AC / DC power conversion part 31, but not provided with the electrical storage part 32. When AC / DC power conversion part 31 outputs direct-current power Pdc_ave, it is explanatory drawing about how the electrical storage energy of electrical storage part 32 changes during repetition time TR. It is a graph which shows the change of the electrical storage energy Ecap of the electrical storage part 32 in the shutdown period Tsd. It is a figure which shows the gradient coil power supply 24 and the gradient coil group 14 in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 MRI room 11 MRI apparatus 12 Subject 14 Gradient coil group 20 Monitor room 21 Control apparatus 22 Operation part 23 Cabinet 24 Gradient coil power supply part 31 AC / DC power conversion part 31a, 241 Insulation transformer 31b, 243 Rectifier 32, 244 Power storage part 33, 245 Discharge unit 33a Discharge resistor 33b Switch 34 DC / AC power conversion means 36, 247 Inverter 37, 248 Filter 40 Power supply control unit

Claims (12)

An MRI apparatus having a gradient coil and a power supply unit for supplying gradient coil AC power to the gradient coil at each repetition time of a data collection period,
The power supply unit is
A first power converter that converts input AC power from an AC power supply source into DC power and outputs the DC power;
A power storage unit that stores the DC power; and a second power conversion unit that extracts DC power from the power storage unit and converts the extracted DC power into the gradient coil AC power;
Have
The power storage unit has a capacity necessary to store the power consumed by the second power conversion unit and the gradient coil during the repetition time,
The second power conversion unit extracts DC power from the power storage unit during the repetition time,
The MRI apparatus, wherein the first power conversion unit replenishes the power storage unit with DC power extracted from the power storage unit during the repetition time during the repetition time.   The MRI apparatus according to claim 1, comprising a plurality of combinations of the second power converter and the gradient coil. A first set of the plurality of sets is provided to generate a gradient magnetic field in the X-axis direction,
A second set of the plurality of sets is provided to generate a gradient magnetic field in the Y-axis direction,
The MRI apparatus according to claim 2, wherein a third set of the plurality of sets is provided to generate a gradient magnetic field in the Z-axis direction.   The MRI apparatus according to any one of claims 1 to 3, wherein the power supply unit includes a discharge unit for consuming DC power stored in the power storage unit. The discharge part has a discharge resistor and a switch,
5. The MRI apparatus according to claim 1, wherein the switch electrically connects the discharge resistance to the power storage unit in response to an ON signal. 6. The first power converter is
An insulating transformer that converts the input AC power into output AC power; and a rectifier that converts the output AC power into DC power;
The MRI apparatus according to any one of claims 1 to 5, comprising:   The MRI apparatus according to claim 1, comprising a plurality of combinations of the first power conversion unit, the power storage unit, the second power conversion unit, and the gradient coil. A first set of the plurality of sets is provided to generate a gradient magnetic field in the X-axis direction,
A second set of the plurality of sets is provided to generate a gradient magnetic field in the Y-axis direction,
The MRI apparatus according to claim 7, wherein a third set of the plurality of sets is provided to generate a gradient magnetic field in the Z-axis direction.   The isolation transformer outputs, from the input AC power, output AC power supplied to the first power conversion unit of the first set and output supplied to the first conversion unit of the second set. The MRI apparatus according to claim 7, wherein the MRI apparatus generates AC power and output AC power supplied to the first conversion unit of the third set.   The MRI apparatus according to claim 1, further comprising a control unit that controls a timing at which the second power conversion unit extracts power from the power storage unit.   The MRI apparatus according to any one of claims 1 to 10, wherein the power storage unit is a capacitor.   The MRI apparatus according to claim 11, wherein the capacitor is an electric double layer capacitor.

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