JP2011019565A - Magnetic resonance imaging apparatus and rf coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce time for adjusting an RF coil. <P>SOLUTION: The RF coil includes an adjustment signal receiving part for receiving an adjustment signal for adjusting capacitance of a capacitor. Then, the capacitor adjusts the capacitance in accordance with the adjustment signal received by the adjustment signal receiving part. For example, the RF coil adjusts the capacitance of the capacitor by switching a plurality of switches between on and off in accordance with the adjustment signal by connecting a plurality of electric paths, having capacitor with prescribed capacitance and a switch which are serially connected, in parallel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus and an RF coil.

  2. Description of the Related Art Conventionally, a magnetic resonance imaging apparatus (Magnetic Resonance Imaging apparatus, hereinafter referred to as “MRI apparatus”) uses an RF (Radio Frequency) coil to detect MR signals (Patent Documents 1 and 2, etc.). FIG. 6 is a diagram showing an equivalent circuit of a conventional RF coil. As shown in FIG. 6, the RF coil is a resonance circuit, and when the resonance frequency matches the resonance frequency of the MR signal, the MR signal is output. To detect.

  For this reason, the RF coil may be delivered after “matching” for matching the impedance of the RF coil to 50Ω, for example, and “tuning” for matching the resonance frequency to the Larmor frequency. It is common. Specifically, an engineer such as a service engineer adjusts the capacity of the two variable capacitors shown in FIG. 6 by manually operating a trimmer rotation operation while looking at a dedicated measuring instrument (spectrum analyzer, etc.). Tune with. At this time, since the measuring instrument cannot be brought into the examination room, which is a magnetic shield room, the engineer adjusts while reciprocating the inside and outside of the examination room.

JP-A-6-285036 Japanese Patent Laid-Open No. 4-141146

  However, in the above-described conventional technique, adjustment is performed while reciprocating between the inside and outside of the examination room, so that there is a problem that the load on the technician in the adjustment work of the RF coil is high.

  The present invention has been made in view of the above, and an object thereof is to provide a magnetic resonance imaging apparatus and an RF coil capable of simplifying the adjustment work of the RF coil.

  In order to solve the above-described problems and achieve the object, the magnetic resonance imaging apparatus according to claim 1 receives an adjustment signal for adjusting the capacitance of the capacitor, and an RF coil for adjusting the capacitance of the capacitor according to the adjustment signal. It is characterized by having.

  According to a sixth aspect of the present invention, the RF coil includes an adjustment signal receiving unit that receives an adjustment signal for adjusting the capacitance of the capacitor, and a capacitor that adjusts the capacitance according to the adjustment signal received by the adjustment signal receiving unit. It is characterized by.

  According to the first or sixth aspect of the present invention, there is an effect that the adjustment work of the RF coil can be simplified.

FIG. 1 is a diagram for explaining the outline of the RF coil according to the first embodiment. FIG. 2 is a block diagram illustrating the configuration of the MRI apparatus according to the first embodiment. FIG. 3 is a diagram for explaining the abdominal RF coil. FIG. 4 is a block diagram showing the configuration of the abdominal RF coil. FIG. 5 is a diagram for explaining a case where there are a plurality of channels. FIG. 6 is a diagram showing an equivalent circuit of a conventional RF coil.

  Examples of the magnetic resonance imaging apparatus and the RF coil according to the present invention will be described below. In addition, this invention is not limited by the following examples.

[Outline of RF Coil in Example 1]
First, the outline of the RF coil according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining the outline of the RF coil according to the first embodiment.

  As shown in the equivalent circuit of FIG. 1, the RF coil in the first embodiment includes a coil and a capacitor. Here, the capacitor | condenser in Example 1 can adjust the capacity | capacitance by electrical control.

  Specifically, as shown in FIG. 1, the RF coil includes an adjustment signal receiving unit that receives an adjustment signal for adjusting the capacitance of the capacitor. The capacitor adjusts the capacitance according to the adjustment signal received by the adjustment signal receiving unit.

  As described above, the capacitance of the capacitor included in the RF coil according to the first embodiment can be adjusted by electrical control. Therefore, an engineer can remotely transmit an electrical adjustment signal for adjusting the capacitance of the capacitor. It only needs to be transmitted, eliminating the need to reciprocate inside and outside the examination room. As a result, according to the RF coil in the first embodiment, the adjustment work of the RF coil can be simplified.

[Configuration of MRI Apparatus According to Embodiment 1]
The RF coil according to the first embodiment has been described so far, but the MRI apparatus according to the first embodiment includes the above-described RF coil. Then, next, the structure of the MRI apparatus which concerns on Example 1 is demonstrated using FIGS. FIG. 2 is a block diagram illustrating the configuration of the MRI apparatus according to the first embodiment.

  As shown in FIG. 2, the MRI apparatus 100 mainly includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power source 3, a bed 4, a bed control unit 5, a transmission RF coil 6, and a transmission. Unit 7, reception RF coil 8, reception unit 9, sequence control unit 10, computer system 20, and abdominal RF coil 30.

  The static magnetic field magnet 1 is formed in a hollow cylindrical shape and generates a uniform static magnetic field in an internal space. For example, a permanent magnet or a superconducting magnet is used as the static magnetic field magnet 1.

  The gradient coil 2 is formed in a hollow cylindrical shape and generates a gradient magnetic field in the internal space. Specifically, the gradient magnetic field coil 2 is arranged inside the static magnetic field magnet 1 and receives a current supplied from the gradient magnetic field power supply 3 to generate a gradient magnetic field. The gradient magnetic field coil 2 is formed by combining three coils corresponding to the X, Y, and Z axes orthogonal to each other, and the three coils are individually supplied with current from the gradient magnetic field power supply 3, A gradient magnetic field is generated in which the magnetic field strength varies along the X, Y, and Z axes. The Z-axis direction is the same direction as the static magnetic field.

  Here, the gradient magnetic fields of the X, Y, and Z axes generated by the gradient magnetic field coil 2 correspond to, for example, the slice selection gradient magnetic field Gs, the phase encoding gradient magnetic field Ge, and the readout gradient magnetic field Gr, respectively. Yes. The slice selection gradient magnetic field Gs is used to arbitrarily determine an imaging section. The phase encoding gradient magnetic field Ge is used to change the phase of the magnetic resonance signal in accordance with the spatial position. The readout gradient magnetic field Gr is used for changing the frequency of the magnetic resonance signal in accordance with the spatial position.

  The gradient magnetic field power supply 3 supplies a current to the gradient magnetic field coil 2. Specifically, the gradient magnetic field power supply 3 executes a sequence according to the sequence information received from the sequence control unit 10 under the control of the sequence control unit 10 and supplies a current to the gradient magnetic field coil 2.

  The bed 4 includes a top plate 4a on which the subject P is placed, and the top plate 4a is inserted into the cavity (imaging port) of the gradient magnetic field coil 2 with the subject P placed thereon. Usually, the bed 4 is installed such that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 1.

  The bed control unit 5 controls the bed 4. Specifically, the couch controller 5 drives the couch 4 in response to an instruction from the computer system 20, and moves the top 4a in the longitudinal direction and the vertical direction.

  The transmission RF coil 6 generates a high frequency magnetic field. Specifically, the transmission RF coil 6 is arranged inside the gradient magnetic field coil 2 and receives a supply of RF pulses from the transmission unit 7 to generate a high-frequency magnetic field.

  The reception RF coil 8 receives the MRI echo signal. Specifically, the reception RF coil 8 is disposed inside the gradient magnetic field coil 2 and receives an MRI echo signal radiated from the subject P due to the influence of the high-frequency magnetic field. The reception RF coil 8 transmits the received MRI echo signal to the reception unit 9.

  The transmission unit 7 transmits an RF pulse corresponding to the Larmor frequency to the transmission RF coil 6. The receiving unit 9 generates k-space data based on the MRI echo signal output from the reception RF coil 8. Specifically, the reception unit 9 digitally converts the MRI echo signal output from the reception RF coil 8 to generate k-space data, and transmits the generated k-space data to the sequence control unit 10.

  The sequence control unit 10 controls the gradient magnetic field power supply 3 and the transmission unit 7. Specifically, the sequence control unit 10 transmits the sequence information transmitted from the computer system 20 to the gradient magnetic field power supply 3 and the transmission unit 7. The sequence information is information for operating the gradient magnetic field power supply 3 and the transmission unit 7 according to a series of sequences.

  The computer system 20 performs overall control of the MRI apparatus 100 such as scan control by the sequence control unit 10 and image reconstruction based on instructions from the operator. Specifically, the computer system 20 includes an interface unit 21, an image reconstruction unit 22, a storage unit 23, an input unit 24, a display unit 25, and a control unit 26.

  The interface unit 21 controls input / output of various signals exchanged with the sequence control unit 10. Specifically, the interface unit 21 transmits the sequence information generated by the control unit 26 to the sequence control unit 10. The interface unit 21 receives k-space data from the sequence control unit 10 and stores the received k-space data in the storage unit 23 for each subject P.

  The image reconstruction unit 22 reconstructs an image of the subject P. Specifically, the image reconstruction unit 22 performs post-processing, that is, reconstruction such as Fourier transform, on the k-space data stored in the storage unit 23, so that the spectrum of the desired nuclear spin in the subject P is obtained. Data or image data is generated. Then, when generating the spectrum data and the image data, the image reconstruction unit 22 stores them in the storage unit 23.

  The storage unit 23 stores various data. For example, the storage unit 23 stores k-space data received by the interface unit 21, spectrum data and image data generated by the image reconstruction unit 22, and the like.

  The input unit 24 receives various instructions and information input from the operator. Specifically, as the input unit 24, a pointing device such as a mouse or a trackball, a selection device such as a mode change switch, or an input device such as a keyboard can be used as appropriate.

  The display unit 25 displays various information such as spectrum data and image data generated by the image reconstruction unit 22. Specifically, as the display unit 25, a display device such as a liquid crystal display can be used as appropriate.

  The control unit 26 includes a CPU, a memory, and the like (not shown) and performs overall control of the MRI apparatus 100. For example, when an imaging condition is set by the operator via the input unit 24, the control unit 26 generates sequence information based on the set imaging condition, and the sequence information is sequenced via the interface unit 21. It transmits to the control part 10. In addition, when the k-space data is transferred from the sequence control unit 10 as a result of executing the scan of the subject P based on the transmitted sequence information, the control unit 26 reconstructs an image from the transmitted k-space data. The image reconstruction unit 22 is controlled to do so.

  The abdomen RF coil 30 is an imaging target of the abdomen of the subject P, receives the RF pulse from the transmission unit 7 and generates a high-frequency magnetic field, and from the subject P due to the influence of the high-frequency magnetic field. It consists of a receiving RF coil that receives the radiated MRI echo signal.

  Here, the abdominal RF coil 30 according to the first embodiment will be described in detail with reference to FIGS. FIG. 3 is a diagram for explaining an abdominal RF coil, FIG. 4 is a block diagram showing a configuration of the abdominal RF coil, and FIG. 5 is a diagram for explaining a case where there are a plurality of channels. It is.

  As shown in FIG. 3, the abdominal RF coil 30 according to the first embodiment includes an upper unit 31 and a lower unit 32. For example, the lower unit 32 is placed on the bed 4, the subject P is laid on the lower unit 32, the upper unit 31 is placed on the subject P, and the upper unit 31 is fixed to the lower unit 32 by the band 33. Use it.

  As shown in FIG. 3, the upper unit 31 and the lower unit 32 are coupled by a cable 34 and a connector 36. The MRI echo signal detected by the surface coil of the upper unit 31 is once transmitted to the lower unit 32 side via the cable 34 and the connector 36, and the cable 35 together with the MRI echo signal detected by the surface coil of the lower unit 32. And transmitted to the receiving unit 9 of the MRI apparatus 100 via the connector 37.

  Next, as shown in FIG. 4, the abdominal RF coil 30 according to the first embodiment includes a coil 30a, an adjustment signal receiving unit 30b, and a capacitor 30d.

The adjustment signal receiving unit 30b receives an adjustment signal for adjusting the capacitance of the capacitor, and adjusts the capacitor 30d with the received adjustment signal. Specifically, the adjustment signal receiving unit 30b includes a GPIO (General Purpose Input / Output) control unit 30c, and also includes, for example, an I ² C (Inter-Integrated Circuit) bus as an interface. The I ² C bus is a 2-wire synchronous serial communication interface. The adjustment signal receiving unit 30b receives an adjustment signal that is an SDA signal from an external device (such as a spectrum analyzer or other general-purpose computer) via the I ² C bus, for example, and the GPIO control unit 30c receives the adjustment signal received To adjust the capacitor 30d. The SCL signal is a clock signal. The interface is not limited to the I ² C bus, and may be another serial bus, for example.

  As shown in FIG. 4, the capacitor 30d is formed by connecting a plurality of electric circuits in which a switch and a capacitor having a predetermined capacity are connected in series. Here, the switch is turned on / off by electrical control, and is, for example, an FET (Field Effect Transistor). That is, when the switch is turned on / off by the adjustment signal, the number of capacitors connected to the coil 30a changes, and as a result, the capacitance of the capacitor is adjusted.

  Further, the capacitance adjustment of the capacitor 30d may be adjusted by a single adjustment signal, or may be gradually adjusted to an optimum capacitance by a plurality of adjustment signals. That is, although not shown in FIG. 4, information indicating the impedance and resonance frequency of the coil 30a corresponding to the adjustment result is transmitted to the external device through the adjustment receiving unit 30b each time, and the external device adjusts again. A technique of gradually adjusting to an optimum capacity by transmitting a signal may be used.

  Although FIG. 4 shows an example in which four capacitors are connected in parallel, the present invention is not limited to this. For example, the capacity and number of individual capacitors can be arbitrarily changed.

  Further, as shown in FIG. 5, when there are a plurality of channels, the adjustment signal receiving unit 30b includes GPIO control units 30c corresponding to the number of channels, and each GPIO control unit 30c has a capacitor 30d for each channel. Adjustments can be made. At this time, the adjustment signal can distribute channels by addressing.

[Effect of Example 1]
As described above, the RF coil according to the first embodiment includes the adjustment signal receiving unit that receives the adjustment signal for adjusting the capacitance of the capacitor, and the capacitor that adjusts the capacitance according to the adjustment signal received by the adjustment signal receiving unit. The engineer only needs to remotely transmit an electrical adjustment signal for adjusting the capacitance of the capacitor, and does not need to reciprocate between the inside and outside of the examination room. As a result, according to the RF coil in the first embodiment, the adjustment work of the RF coil can be simplified.

  In addition, as a result of the adjustment by electrical control, for example, when there are a plurality of channels in the RF coil, the adjustment time, compared to the conventional manual adjustment operation performed while reciprocating inside and outside the examination room, for example. Can be shortened.

  In addition, since it is possible to remotely adjust the capacitance of the capacitor, for example, it is also possible to remotely confirm the current adjustment state. If necessary, auto calibration can be performed by a control program provided by the external device itself. Can also be realized. As a result, it is also possible to realize new applications that are not constrained by existing clinical applications.

  In addition, the RF coil according to the first embodiment connects a plurality of electric circuits in which a capacitor having a predetermined capacity and a switch are connected in series, and switches the on / off of the plurality of switches according to the adjustment signal, thereby reducing the capacitance of the capacitor. adjust. For this reason, it becomes possible to implement | achieve simply and flexibly.

Furthermore, RF coils in the first embodiment has an interface for the I ² C bus, receives an adjustment signal via an interface I ² C bus. Further, even when a plurality of channels are provided, an adjustment signal designating a predetermined channel is received via the I ² C bus interface. For this reason, even if the number of channels increases, the number of signal lines for control can be suppressed.

  Although the first embodiment has been described so far, the present invention may be implemented in various different forms other than the above-described embodiments.

[RF coil]
In Example 1, the example which applies this invention to RF coil for abdomen has been demonstrated. However, the present invention is not limited to this, and can be similarly applied to a transmission RF coil, a reception RF coil, a head RF coil, a spinal RF coil, a surface coil, and the like included in the MRI apparatus main body. it can.

  In the first embodiment, a plurality of electric circuits in which a capacitor having a predetermined capacity and a switch are connected in series are connected in parallel, and the capacitance of the capacitor is adjusted by switching the plurality of switches on and off in accordance with an adjustment signal. I have explained the technique. However, the present invention is not limited to this. That is, any other method may be used as long as the capacitance can be adjusted by electrical control.

  In the first embodiment, a method has been described in which an RF coil and an external device (such as a spectrum analyzer or other general-purpose computer) transmit and receive adjustment signals. However, the present invention is not limited to this. According to the present invention, since adjustment by electrical control is possible, a control program for adjustment is incorporated in the computer system of the MRI apparatus, and the RF coil and the control program incorporated in the computer system transmit and receive adjustment signals. The technique to do may be used. For example, the control unit 26 illustrated in FIG. 2 transmits an adjustment signal.

  In this case, the adjustment work is not necessarily limited to delivery, and can be performed at the time of photographing. For example, it is possible for an imaging engineer to perform adjustment work such as matching and tuning for each shooting using an adjustment control program incorporated in the computer system, and in an optimum state according to the shooting target. It is also possible to shoot.

100 MRI apparatus 30 RF coil for abdomen 30a Coil 30b Adjustment signal receiving unit 30c GPIO control unit 30d Capacitor

Claims (6)

  A magnetic resonance imaging apparatus comprising: an RF coil that receives an adjustment signal for adjusting a capacitance of a capacitor and adjusts the capacitance of the capacitor according to the adjustment signal. The RF coil is
A plurality of electric circuits in which a capacitor having a predetermined capacity and a switch are connected in series are connected in parallel, and the capacitance of the capacitor is adjusted by switching on and off the plurality of switches according to the adjustment signal. 2. The magnetic resonance imaging apparatus according to 1. The RF coil is
Has a serial bus interface,
The magnetic resonance imaging apparatus according to claim 1, wherein the adjustment signal is received via a serial bus interface. The RF coil has a plurality of channels,
4. The magnetic resonance imaging apparatus according to claim 3, wherein the adjustment signal designating a predetermined channel is received via a serial bus interface. An adjustment signal transmitting unit for transmitting the adjustment signal;
The magnetic resonance imaging apparatus according to claim 1, wherein the RF coil receives an adjustment signal transmitted by the adjustment signal transmission unit. Adjustment signal receiving means for receiving an adjustment signal for adjusting the capacitance of the capacitor;
An RF coil comprising: a capacitor that adjusts the capacitance according to the adjustment signal received by the adjustment signal receiving means.

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