JP2007181615A - Mri apparatus and power unit for mri apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce S/N deterioration of MR signal caused by noise arising from the switching power supply. <P>SOLUTION: A trap filter 512 and 513 having a certain center frequency and cut-off band are provided at the input and output terminals of the switching power supply 511. If the direct-current power source line 531 connecting the output terminal of the switching power supply 511 with the receiving circuit for MR signal or the alternate-current power supply line 521 connected to the switching power supply 511 has an equivalent wave length of MR signal longer than 1/4 of λx, a trap filter 532 which has an almost similar characteristic as stated above is inserted into almost the same position of λx/4 from the output terminal of the direct-current power supply line 531. Similarly, the trap filter 522 is inserted into the almost the same position of λx/4 from the input terminal of the alternate-current power supply line 521. The center wavelength and the cut-off band are set from the center wavelength (Larmor frequency) and its signal band of the MR signal received in the receiving circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an MRI apparatus and an MRI power supply apparatus, and more particularly to an MRI apparatus and an MRI power supply apparatus that improve S / N of image data by blocking power supply noise.

  In magnetic resonance imaging (MRI), a nuclear spin in a subject tissue placed in a static magnetic field is excited by a high-frequency signal (RF pulse) having the Larmor frequency, and a magnetic resonance signal ( This is an imaging method for reconstructing image data from MR signals.

  An MRI apparatus is an image diagnostic apparatus that generates image data based on MR signals detected from within a living body, and obtains a lot of diagnostic information such as biochemical information and functional diagnostic information as well as anatomical diagnostic information. Therefore, it has become indispensable in the field of diagnostic imaging today.

  In this MRI apparatus, a subject is irradiated with an RF pulse having a frequency component of a predetermined band (eg, ± 250 KHz) centered on a Larmor frequency f0 (eg, 63.9 MHz), and an MR signal having the same frequency component is irradiated. Received from the subject and generates image data. Since this MR signal is a very small signal, it is necessary to eliminate noise having the same frequency component as much as possible. For this reason, a transmitting / receiving coil for detecting an MR signal and a receiving circuit for amplifying the MR signal detected by the transmitting / receiving coil to a predetermined amplitude are usually installed in a shield room.

  A digital circuit or switching circuit that can be a broadband noise source including the signal band of the MR signal is installed outside the shield room or stopped during collection of the MR signal, thereby mixing noise into the MR signal. Avoid.

  On the other hand, a so-called dropper power supply having a very small noise component in the signal band of the MR signal is used as an MRI power supply for supplying a DC voltage / current to the above receiving circuit, and this dropper power supply is used together with the above receiving circuit in a shielded room. The method of installing inside has been taken.

  However, since this dropper power supply is extremely large compared to the switching power supply, it requires a large installation area when installed in a shielded room, and also has a large amount of magnetic material such as a transformer. In such cases, there is a high risk that an accident due to a static magnetic field of the MRI apparatus will occur. For this reason, there is a case in which a dropper power supply is installed outside the shield room and a desired DC voltage / current is supplied to the receiving circuit via a long DC power cable.

  FIG. 6 shows a conventional installation method of a DC power supply unit having a dropper power supply. FIG. 6A shows a DC power supply unit 51A installed inside a shield room, and FIG. ) Shows the DC power supply unit 51B installed outside the shield room.

  That is, in FIG. 6A, the DC power supply unit 51A installed in the shield room converts the AC voltage / current supplied from the outside of the shield room via the AC power cable 52A into a predetermined DC voltage / current. To the receiving circuit 313. At this time, a line filter 120A for blocking external noise entering from the outside of the shield room via the AC power cable 52A is provided on the wall of the shield room through which the AC power cable 52A passes.

  On the other hand, in FIG. 6B, the DC power supply unit 51B installed outside the shield room converts the AC voltage / current supplied via the AC power supply cable 52B into a predetermined DC voltage / current, and the DC power supply. The signal is supplied to the receiving circuit 313 in the shield room via the cable 53B. Also in this case, a line filter 120B is provided on the wall of the shield room through which the DC power cable 53B passes to block external noise that enters from the outside of the shield room via the DC power cable 53B. Further, at the input / output ends of the DC power supply unit 51A and the DC power supply unit 51B, a π-type that blocks propagation of power supply noise generated by these DC power supply units to the AC power supply cables 52A and 52B and the DC power supply cables 53A and 53B. A filter circuit such as a filter is attached.

  By the way, with the recent development of the parallel imaging method, the scale of the receiving circuit is increased, and a DC power supply unit having a large power supply capacity is required to supply a DC voltage / current to such a receiving circuit. When installing a DC power supply unit consisting of a dropper power supply that has become larger due to an increase in capacity inside a shield room, the installation area increases, the difficulty of installation work, and the danger of suction accidents, etc. Sex is a serious problem.

  On the other hand, when the DC power supply unit is installed outside the shield room, a DC power cable having a thick core wire (power line) is required to reduce voltage drop caused by a large current flowing through the long DC power cable. . The size of the line filter attached to the wall of the shield room increases as the DC current increases, and more than one or more line filters and DC power cables are provided for each of various DC voltages. It is necessary to provide a book.

  In order to deal with such problems, a method is conceivable in which a DC power supply unit constituted by a switching power supply that is small and can obtain a large power supply capacity is installed in a shield room. According to this method, the switching power supply does not require a large installation area in the shield room, but also has an extremely small amount of magnetic material compared to a conventional dropper power supply having a large transformer, so that an attraction accident due to a static magnetic field is not caused. Occurrence can be prevented.

  However, the switching power supply generates a large switching noise (power supply noise), and the switching noise generated from the switching power supply becomes radiation noise or conduction noise and enters the above receiving circuit, so that the S / N of the MR signal is remarkably increased. It has the problem of deteriorating.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an MR signal excellent in S / N by providing a trap filter at the input / output end of a DC power supply unit having a switching power supply. An object of the present invention is to provide an MRI apparatus capable of detection and a power supply apparatus for MRI.

  In order to solve the above problems, an MRI power supply device according to the present invention according to claim 1 is a switching power supply for converting alternating current into direct current by a switching method, an alternating current power line connected to an input terminal of the switching power supply, A DC power supply line connected to the output end of the switching power supply and supplying a DC voltage / current to the receiving circuit of the MRI apparatus, and a predetermined center frequency attached at at least one of the input end and the output end of the switching power supply And a first trap filter having a band, wherein the center frequency and the band of the first trap filter are set based on an MR signal received by the receiving circuit.

  On the other hand, the MRI apparatus of the present invention according to claim 9 generates image data by receiving an MR signal generated by irradiating an RF pulse to a subject to which a static magnetic field and a gradient magnetic field are applied, by a receiving circuit. An MRI apparatus comprising the MRI power supply apparatus according to any one of claims 1 to 8 as means for supplying a DC voltage / current to the receiving circuit.

  The MRI apparatus of the present invention according to claim 10 generates image data by receiving an MR signal generated by irradiating a subject to which a static magnetic field and a gradient magnetic field are applied with an RF pulse by a receiving circuit. In the MRI apparatus, a trap filter having a center frequency and a band set based on an MR signal received by the receiving circuit is attached to at least one of an input end and an output end, and a DC voltage is applied to the receiving circuit. / MRI power supply device for supplying current is provided.

  According to the present invention, by providing a trap filter at the input / output end of a DC power supply unit having a switching power supply, it is possible to reduce the outflow of switching noise generated in the DC power supply unit. MR signals can be detected.

  Embodiments of the present invention will be described below with reference to the drawings.

  The first feature of the embodiment of the present invention described below is that the receiving circuit includes a DC power supply unit having a switching power supply for supplying DC voltage / current to the receiving circuit provided in the transmitting / receiving coil section of the MRI apparatus. The object is to provide a trap filter (first trap filter) having a predetermined center frequency and a cutoff band at an input end and an output end of the DC power supply unit. The center frequency and cutoff band of the trap filter are set based on the center frequency (Larmor frequency) of the MR signal received by the receiving circuit and the signal band.

  The second feature of the present embodiment is that the DC power supply line connecting the output terminal of the DC power supply unit and the MR signal receiving circuit or the AC power supply line connected to the input terminal of the DC power supply unit has an MR signal effective wavelength λx. Is approximately equal to the above characteristic at a position of approximately λx / 4 from the output end of the DC power supply line or a position of approximately λx / 4 from the input end of the AC power supply line. Is to insert a trap filter (second trap filter).

(Device configuration)
The configuration of the MRI apparatus in the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the MRI apparatus in this embodiment, and FIG. 3 explains an MRI power supply apparatus (hereinafter referred to as a power supply apparatus) provided in the MRI apparatus. FIG.

  The MRI apparatus 100 shown in FIG. 1 transmits / receives an RF pulse to the subject 150 and receives an MR signal, and a static magnetic field generator 1 and a gradient magnetic field generator 2 that generate a magnetic field for the subject 150. A power supply device 5 for supplying a DC voltage / current to a transmission / reception coil unit 31 (to be described later) of the transmission / reception unit 3;

  Furthermore, the MRI apparatus 100 includes an image data generation unit 6 that reconstructs MR signals received by the transmission / reception unit 3 to generate image data, a display unit 7 that displays the generated image data, and MR signal collection. An input unit 8 for setting conditions and display conditions for image data, inputting various command signals, and the like, and a control unit 9 for controlling each unit in the MRI apparatus 100 are provided.

  The static magnetic field generation unit 1 includes a superconducting magnet 11 and a static magnetic field power source 12 that supplies current to the superconducting magnet 11, and forms a strong static magnetic field around the subject 150.

  The gradient magnetic field generating unit 2 includes a gradient magnetic field coil 21 that forms gradient magnetic fields in the X, Y, and Z axis directions orthogonal to each other, and a gradient magnetic field power supply 22 that supplies a current to each of the gradient magnetic field coils 21. .

  A gradient magnetic field control signal is supplied to the gradient magnetic field power source 22 by the control unit 9, and the space in which the subject 150 is placed is encoded. That is, by controlling the pulse current supplied from the gradient magnetic field power supply 22 to the gradient magnetic field coil 21 in the X, Y, and Z axis directions based on the gradient magnetic field control signal, the gradient magnetic fields in the X, Y, and Z axis directions are synthesized. Thus, the slice selection gradient magnetic field Gs, the phase encoding gradient magnetic field Ge, and the readout (frequency encoding) gradient magnetic field Gr orthogonal to each other are formed in an arbitrary direction. The gradient magnetic field in each direction is superimposed on the static magnetic field formed by the superconducting magnet 11 and applied to the subject 150.

  The transmission / reception unit 3 irradiates the subject 150 with an RF pulse and detects an MR signal generated in the subject 150, and a transmission unit 32 and a reception signal connected to the transmission / reception coil unit 31. A processing unit 33 is provided. The transmission / reception coil unit 31 includes a transmission / reception coil (not shown) and a reception circuit disposed in the vicinity of the transmission / reception coil in order to amplify an MR signal detected by the transmission / reception coil at high S / N. However, when the transmission coil and the reception coil are provided separately in the transmission / reception coil unit 31, the above-described reception circuit is connected to the reception coil and disposed in the vicinity of the reception coil.

  On the other hand, the transmission unit 32 supplies an RF pulse current having the same frequency as the magnetic resonance frequency determined by the static magnetic field strength of the superconducting magnet 11 and modulated with a predetermined selective excitation waveform to the transmission / reception coil of the transmission / reception coil unit 31. The subject 150 is irradiated with an RF pulse. On the other hand, the reception signal processing unit 33 performs A / D conversion after performing signal processing such as intermediate frequency conversion, phase detection, and filtering on the electrical signal received as the MR signal by the transmission / reception coil unit 31.

  The superconducting magnet 11, the gradient magnetic field coil 21, and the transmission / reception coil unit 31 described above are provided in a gantry (frame) (not shown) of the MRI apparatus, and an imaging field is formed in the center of the gantry.

  On the other hand, the power supply device 5 is a power supply device for supplying a DC voltage / current to a receiving circuit provided in the transmission / reception coil unit 31, and is capable of supplying a large amount of current with a small power supply size. Has a power supply. The power supply device 5 is installed inside the shield room together with the gantry and the bed 4 described above.

  FIG. 2 shows a power supply device 5 installed in a shield room. The power supply device 5 includes a DC power supply unit 51 that converts an AC voltage / current of 100 V or 200 V into a desired DC voltage / current, An AC power cable 52 for supplying an AC voltage / current to the DC power supply unit 51 and a predetermined DC voltage / current generated by the DC power supply unit 51 to the receiving circuit 313 of the transmission / reception coil unit 31 housed in the gantry 110 A DC power supply cable 53 is provided. However, the wall part of the shield room through which the AC power cable 52 passes is provided with a line filter 120 for blocking noise entering from the outside via the AC power cable 52.

  Next, the configuration of the power supply device 5 will be described in more detail with reference to FIG. The DC power supply unit 51 of the power supply device 5 shown in FIG. 3 is attached to a switching power supply 511 that converts an AC voltage / current into a desired DC voltage / current by a switching method, and an input terminal (AC terminal) of the switching power supply 511. A trap filter 513 attached to the trap filter 512 and the output terminal (DC terminal), and a shield case 514 that covers the switching power supply 511 and the trap filters 512 and 513.

  The trap filter 512 suppresses the propagation of switching noise generated by the switching power supply 511 to the AC power supply cable 52 and prevents the switching noise from being emitted from the AC power supply cable 52 into the shielded room. Similarly, the trap filter 513 suppresses the propagation of the switching noise to the DC power cable 53, and prevents the switching noise from being emitted from the DC power cable 53 into the shield room. On the other hand, the shield case 514 prevents switching noise radiated directly from the switching power supply 511 from being emitted into the shield room.

  On the other hand, the AC power supply cable 52 of the power supply device 5 is connected to the input end of the switching power supply 511 and supplies an AC voltage / current from the outside of the shield room, and the AC power supply line 521 substantially from the input end of the AC power supply line 521. A trap filter 522 inserted at a position of λx / 4 (λx is an MR signal effective wavelength) and a braided wire such as a tinned annealed copper wire are formed so as to cover the AC power supply line 521 and the trap filter 522. It has a braided wire 523.

  The DC power supply cable 53 of the power supply device 5 is connected to the output terminal of the switching power supply 511 and supplies a desired DC voltage / current to the reception circuit 313 of the transmission / reception coil unit 31 and the DC power supply. The trap filter 532 inserted at a position of approximately λx / 4 from the output end of the line 531, and a braided wire formed by braiding the same wire as described above and attached so as to cover the DC power supply line 531 and the trap filter 532 533.

  One end of the braided wire 523 of the AC power supply cable 52 and the braided wire 533 of the DC power supply cable 53 is connected to the shield case 514 of the DC power supply unit 51 and is confined inside the AC power supply cable 52 and the DC power supply cable 53. Leakage of the generated radiation noise and radiation noise from the trap filters 512 and 513 into the shield room is prevented.

  The above-mentioned MR signal effective wavelength λx is a wavelength when switching noise having the same frequency as the Larmor frequency f0 propagates through the AC power supply line 521 or the DC power supply line 531, and electromagnetic waves of the same frequency are usually in the air. It can be obtained by multiplying the wavelength λ0 at the time of propagation by the cable shortening rate α. For example, the center frequency f0 of the MR signal detected from the subject 150 placed at a magnetic field intensity of 1.5 T by the superconducting magnet 11 is 63.9 MHz, and switching noise having the same frequency as this center frequency propagates through the air. In this case, the wavelength λ0 is λ0 = C0 / f0 = 4.7 m. Therefore, when the cable shortening rate α is 0.65, the effective MR signal wavelength λx is λx = αλ0 = 3.1 m.

  Next, the trap filter 522 and the knives line 523 are for reducing the influence of switching noise leaked to the AC power supply line 521 without being sufficiently suppressed by the trap filter 512. The trap filter 522 Resonance caused by outflow to the AC power supply line 521 is prevented and radiation noise from the AC power supply line 521 is reduced. Further, the braided wire 523 shields radiation noise from the AC power supply line 521 and enters the shielded room. Prevent radiation.

  Similarly, the trap filter 532 and the knitting line 533 are for reducing the influence of switching noise leaked from the trap filter 513 to the DC power supply line 531, and the trap filter 532 is a DC power supply line 531 for switching noise. Resonance caused by outflow to the DC power line 531 is prevented and radiation noise from the DC power supply line 531 is reduced. Further, the braided wire 533 shields radiation noise from the DC power supply line 531 to prevent radiation into the shielded room. .

  Next, the configuration of the trap filter 513 provided in the DC power supply unit 51 of the power supply device 5 and the trap filter 532 provided in the DC power supply cable 53 will be described with reference to FIG.

  In FIG. 4, one terminal of trap filters 513a and 513b in which a coil having an inductance L1 and a capacitor having a capacitance C1 are connected in parallel is connected to each output terminal of a switching power supply 511 having two terminals. DC power supply lines 531a and 531b are connected to the other terminals of 513b.

  Further, trap filters 532a and 532b, in which a coil having an inductance L2 and a capacitor having a capacitance C2 are connected in parallel, are inserted at positions separated from the trap filters 513a and 513b in the DC power supply lines 531a and 531b by about λx / 4, respectively.

That is, the trap filters 513a and 513b and the trap filters 532a and 532b are configured by parallel resonance circuits having resonance frequencies of 2π (L1 · C1) ^1/2 and 2π (L2 · C21) ^1/2. Is set to be substantially equal to the magnetic resonance frequency (Larmor frequency) fo determined by the static magnetic field strength of the superconducting magnet 11. For example, when the Larmor frequency f0 is 63.9 MHz and the inductance L1 is 100 nH, the capacitance C1 is 62 pF.

  The trap filters 513a and 513b and the trap filters 532a and 532b described above exhibit a large impedance characteristic with respect to the noise component of the switching noise having the same center frequency and bandwidth as the MR signal. Leakage to the lines 531a and 531b can be prevented and radiation noise caused by resonance of the DC power supply lines 531a and 531b can be reduced.

  The trap filters 513 and 532 attached to the output end side of the switching power supply 511 have been described above, but the trap filters 512 and 522 are also attached to the input end side of the switching power supply 511 by the same method.

  Next, the noise reduction effect of the trap filter 513 will be described with reference to FIG. FIG. 5A-1 shows an RF pulse irradiated from the transmission / reception coil of the transmission / reception coil unit 31 to the subject 150 based on the RF pulse current supplied from the transmission unit 32 of the transmission / reception unit 3. FIG. (A-2) shows the frequency spectrum of this RF pulse. That is, as shown in FIG. 5 (a-1), when an RF pulse having substantially the same frequency as the Larmor frequency f0 and modulated with a predetermined selective excitation waveform (for example, a sinc function) is used, The frequency spectrum is a rectangular frequency spectrum having a center frequency f0 and a bandwidth 2Δf as shown in FIG. The MR signal detected by the transmission / reception coil also has the same frequency spectrum as that shown in FIG.

  On the other hand, FIG. 5B-1 shows a frequency spectrum of switching noise generated from the switching power supply 511, and FIG. 5B-2 shows a frequency spectrum of switching noise that has passed through the trap filter 513.

  The switching power supply 511 normally performs a switching operation at a basic clock frequency of several tens to several hundreds KHz. For this reason, the switching noise generated from the switching power supply 511 becomes a line spectrum with the above-mentioned basic clock frequency as the interval of the adjacent spectrum, and this line spectrum is also in the signal band of the MR signal shown in FIG. 5 (a-2). It exists in an unacceptable size.

  On the other hand, the broken line in FIG. 5B-2 is the pass characteristic of the trap filter 513, and schematically shows that the switching noise in the range of the bandwidth 2Δf centered on fo is blocked by the trap filter 513. Yes. In this case, it is desirable to set the filter constant so that the component of switching noise fo ± Δf that has passed through the trap filter 513 is equal to or less than −80 dB with respect to the component before passing through the trap filter 513.

  Returning to FIG. 1, the top plate slidably provided on the upper surface of the bed 4 can move the subject 150 to an arbitrary position in the body axis direction in order to set the imaging position. It can be inserted into the photographing field 151 of the camera. Then, the superconducting magnet 11 of the static magnetic field generating unit 1, the gradient magnetic field coil 21 of the gradient magnetic field generating unit 2, the transmitting / receiving coil unit 31 of the transmitting / receiving unit 3, and the DC power supply device 5 are installed together with the bed 4 in the photographing room (shield room). The

  Next, the image data generation unit 6 includes a storage unit 61 and a high-speed calculation unit 62. The storage unit 61 includes an MR signal storage unit 611 that stores MR signals, and an image data storage unit 612 that stores image data. ing. The MR signal storage unit 611 stores the MR signal subjected to intermediate frequency conversion, phase detection, and further A / D conversion by the reception signal processing unit 33, and the image data storage unit 612 stores the MR signal described above. Image data obtained by the reconstruction process is stored.

  On the other hand, the high-speed calculation unit 62 of the image data generation unit 6 performs image reconstruction processing by two-dimensional Fourier transform on the MR signal once stored in the MR signal storage unit 611 to generate real space image data.

  The display unit 7 includes a display data generation circuit, a conversion circuit, and a monitor (not shown). The display data generation circuit is connected to the image data supplied from the image data storage unit 612 of the image data generation unit 6 and the control unit 9. The display data is generated by synthesizing the incidental information such as the subject information supplied from the input unit 8, and the conversion circuit converts the display data into a predetermined display format. Further, the D / A conversion and the television format are performed. The video signal generated by the conversion is displayed on the monitor made of CRT or liquid crystal.

  Next, the input unit 8 includes various input devices such as a switch, a keyboard, and a mouse, and a display panel on the console, and inputs subject information, MR signal collection conditions and image data display conditions, A movement instruction signal for the plate 4 and a photographing start command signal are input.

  The control unit 9 includes a main control unit 91 and a sequence control unit 92. The main control unit 91 includes a CPU and a storage circuit (not shown) and has a function of controlling the MRI apparatus 100 in an integrated manner. The storage circuit of the main control unit 91 stores object information input or set by the input unit 8, MR signal acquisition conditions, image data display conditions, image display format information, and the like.

  Further, the CPU of the main control unit 91 uses the pulse sequence information based on the above-mentioned information input from the input unit 8 (for example, the magnitude of the pulse current applied to the transmission / reception coils of the gradient magnetic field coil 21 and the transmission / reception coil unit 31 and the application time) , Information relating to application timing and the like) is generated and supplied to the sequence control unit 92.

  The sequence control unit 92 of the control unit 9 includes a CPU and a storage circuit (not shown). After the pulse sequence information sent from the main control unit 91 is temporarily stored in the storage circuit, a gradient magnetic field is generated according to the pulse sequence information. The gradient magnetic field power source 22 of the generation unit 2 and the transmission unit 32 and reception signal processing unit 33 of the transmission / reception unit 3 are controlled.

  According to the embodiment of the present invention described above, switching noise having a frequency component in a predetermined band centered on the Larmor frequency is provided by providing the first trap filter at the input / output end of the DC power supply unit having the switching power supply. Outflow can be reduced.

  Also, the propagation of switching noise leaking through the first trap filter is blocked by inserting a second trap filter into the AC power line or the DC power line connected to the input / output terminal of the DC power unit. Further, by inserting the second trap filter at the λx / 4 position of the AC power supply line or the DC power supply line, the resonance of the power supply line due to the switching noise of the wavelength λx can be suppressed.

  Further, by covering the switching power supply and the first trap filter with a shield case and covering the second trap filter, the AC power cable and the DC power cable with a braided wire, the switching noise radiated from these components can be shielded. it can.

  For the above reasons, the receiving circuit of the MRI apparatus can detect an MR signal excellent in S / N without being affected by the switching noise generated by the switching power supply.

  On the other hand, since the DC power supply unit in the above-described embodiment does not require a large installation area because of its small size, even if it is installed in a shield room, it does not interfere with medical practice by the operator of the MRI apparatus. Furthermore, since the switching power supply provided in the DC power supply unit does not have a large transformer circuit, the amount of magnetic material is extremely small as compared with a conventional dropper power supply. Accordingly, it is possible to prevent a suction accident that occurs when the DC power supply unit is replaced, and the DC power supply unit is light in weight due to the use of the switching power supply, so that the installation work is facilitated.

  In addition, since the trap filter in the above-described embodiment can efficiently eliminate switching noise in the MR signal band with a simple circuit configuration, it does not require a large filter such as a line filter and is small and low cost. A DC power supply unit or a power supply device can be realized.

  Furthermore, since the above-described DC power supply unit can be installed close to the receiving circuit in the shield room, voltage drop is reduced, and therefore a DC power cable with a thin core wire (power supply line) can be used. . In addition, the use of this DC power supply unit reduces the size of the line filter provided on the wall of the shield room, and can greatly reduce the quantity of the line filter.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified. For example, in the above-described embodiment, the case where the first trap filter is provided at the input end and the output end of the switching power supply has been described. However, the first trap filter is provided for either the input end or the output end. It may be provided. Similarly, the case where the second trap filter is inserted into the AC power supply line and the DC power supply line has been described. However, the second trap filter is provided for either the AC power supply line or the DC power supply line. May be.

  Moreover, although the case where the first trap filter and the second trap filter are configured by parallel connection of inductance and capacitance has been described, the present invention is not limited to this. For example, in order to secure a desired band In addition, a resistor may be connected in parallel or in series with each of the above-described elements. The first trap filter may have a configuration different from that of the second trap filter.

  Further, in the above-described embodiment, the case where the DC voltage / current is supplied to the receiving circuit has been described. However, the case where the DC voltage / current required for driving the bed installed in the same shield room is supplied. It does not matter.

1 is a block diagram showing the overall configuration of an MRI apparatus in an embodiment of the present invention. The figure which shows the installation method of the power supply device in the Example. The figure which shows the structure of the power supply device in the Example. The figure for demonstrating the trap filter provided in the DC power unit and DC power cable of the Example. The figure which shows typically the noise reduction effect of the trap filter used for the Example. The figure which shows the installation method of the conventional DC power supply unit which has a dropper power supply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation part 11 ... Superconducting magnet 12 ... Static magnetic field power supply 2 ... Gradient magnetic field generation part 21 ... Gradient magnetic field coil 22 ... Gradient magnetic field power supply 3 ... Transmission / reception part 31 ... Transmission / reception coil part 313 ... Reception circuit 32 ... Transmission part 33 ... Received signal processing unit 4 ... Sleeper (top)
DESCRIPTION OF SYMBOLS 5 ... Power supply device 51 ... DC power supply unit 511 ... Switching power supply 512, 513 ... Trap filter 514 ... Shield case 52 ... AC power supply cable 521 ... AC power supply line 522, 532 ... Trap filter 523, 533 ... Braided wire 53 ... DC power supply cable 531 ... DC power supply line 6 ... image data generation unit 61 ... storage unit 611 ... MR signal storage unit 612 ... image data storage unit 62 ... high speed calculation unit 7 ... display unit 8 ... input unit 9 ... control unit 91 ... main control unit 92 ... Sequence control unit 110 ... Gantry 120 ... Line filter 100 ... MRI apparatus

Claims (10)

A switching power supply that converts alternating current to direct current by a switching method;
An AC power supply line connected to the input end of the switching power supply;
A DC power supply line connected to the output terminal of the switching power supply and supplying a DC voltage / current to the receiving circuit of the MRI apparatus;
A first trap filter having a predetermined center frequency and band attached at at least one of an input end and an output end of the switching power supply;
The MRI power supply apparatus, wherein the center frequency and the band of the first trap filter are set based on an MR signal received by the receiving circuit.   The power supply apparatus for MRI according to claim 1, wherein the center frequency of the first trap filter is set based on a Larmor frequency of the MR signal.   2. The MRI power supply apparatus according to claim 1, further comprising a shield case, wherein the shield case is attached so as to cover a part or the whole of the first trap filter and the switching power supply.   2. A second trap filter having a center frequency and a band substantially equal to those of the first trap filter is inserted at a predetermined position of at least one of the AC power line and the DC power line. The power supply apparatus for MRI as described.   5. The MRI power supply apparatus according to claim 4, wherein the second trap filter is inserted at a position of a quarter wavelength corresponding to the center frequency with respect to the input end.   5. The MRI power supply apparatus according to claim 4, wherein the second trap filter is inserted at a position of a quarter wavelength corresponding to the center frequency with respect to the output end.   5. The MRI power supply apparatus according to claim 4, wherein at least one of the second trap filter and an AC power line or a DC power line into which the second trap filter is inserted is covered with a braided wire. .   The MRI power supply apparatus according to claim 1, wherein the switching power supply is installed in a shield room together with the receiving circuit. In an MRI apparatus for generating image data by receiving an MR signal generated by irradiating an RF pulse to a subject to which a static magnetic field and a gradient magnetic field are applied, by a receiving circuit,
9. An MRI apparatus comprising the MRI power supply apparatus according to claim 1 as means for supplying a DC voltage / current to the receiving circuit. In an MRI apparatus for generating image data by receiving an MR signal generated by irradiating an RF pulse to a subject to which a static magnetic field and a gradient magnetic field are applied, by a receiving circuit
A trap filter having a center frequency and a band set based on the MR signal received by the receiving circuit is attached to at least one of the input end and the output end, and supplies a DC voltage / current to the receiving circuit. An MRI apparatus comprising a power supply device for MRI.

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