JP2010253097A - Magnetic resonance imaging machine, and method for processing received signal in magnetic resonance imaging machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging machine which includes a radio transmitter to be connected to an element coil inside a receiving coil and a receiver of a signal processing system to be the pair with the radio transmitter, and increases received signal intensity and suppresses noise by appropriately synthesizing the respective received signals of the receiving coil, in imaging. <P>SOLUTION: The magnetic resonance imaging machine includes: a receiving coil 30 for receiving a nuclear magnetic resonance signal from a subject as a coil received signal; at least one coil received signal transmission means 31 for transmitting the received signal of the receiving coil 30 by radio transmission; a plurality of coil received signal receiving means 32 for receiving coil received signal transmitted from the coil received signal transmission means 31 by radio transmission; a signal synthesizing means 33 for adding and synthesizing the respective coil received signals received by the plurality of coil received signal receiving means 32; and a received data processing means 34 for reconstituting an image of the subject from the coil received signal synthesized by the signal synthesizing means 33. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus for magnetically exciting a nuclear spin of a subject with a radio frequency (RF) signal of a Larmor frequency and reconstructing an image from a nuclear magnetic resonance signal generated along with the excitation, In particular, the present invention relates to a received signal processing method in a magnetic resonance imaging apparatus, and more particularly, to a magnetic resonance imaging apparatus that wirelessly transmits a received signal received by a high frequency receiving coil to a signal processing system, and a received signal processing method in the magnetic resonance imaging apparatus. .

  Conventionally, a magnetic resonance imaging (MRI) device has been used as a monitoring device in a medical field. The MRI apparatus forms a gradient magnetic field in the X-axis, Y-axis, and Z-axis directions with a gradient magnetic field coil in an imaging region of a subject set inside a cylindrical static magnetic field magnet that forms a static magnetic field, and a high-frequency transmission coil A device that resonates an image of a subject using a nuclear magnetic resonance (NMR) signal that is generated by exciting a nuclear spin in the subject by magnetic resonance by transmitting a high-frequency signal from is there.

  In such an MRI apparatus, a receiving coil composed of a plurality of element coils for receiving NMR signals is used, and the number of element coils constituting the receiving coil is increasing in recent years. With the increase in the number of elements in the receiving coil, cable wiring for transmitting the reception signal obtained by the element coil to the signal processing system is also increasing. Since these element coils are moved during photographing, various restrictions are imposed on the cable wiring connected to the element coils.

  In addition, attempts have been made to secure SNR (Signal to Noise Ratio) by using techniques such as AM signal suppression / restoration (Compressor / Expander) technology, ACSB (Amplitude Compressed Single Side Band), and linear modulation. However, in these techniques, there is a problem that not only deterioration of the received signal due to signal suppression is unavoidable with respect to the dynamic range required in the MRI apparatus, but also the circuit becomes more complicated.

  In addition, in the conventional wireless coil system, there is no means for making the spatial distance uniform between the transmitter of the receiving element coil whose arrangement varies depending on the imaging region and the receiver provided in the signal processing system. If the SNR varies, the image quality may be deteriorated. Therefore, in order to suppress the SNR variation, it is necessary to limit the arrangement of the element coils.

  Thus, a magnetic resonance imaging apparatus has been proposed that can improve the reduction in signal-to-noise ratio due to signal attenuation associated with spatial propagation of the received signal when the received signal is transmitted wirelessly (see Patent Document 1). The magnetic resonance imaging apparatus includes: a reception coil that receives a nuclear magnetic resonance signal from a subject as a reception signal; at least one reception signal transmission antenna that wirelessly transmits the reception signal from the reception coil; and a reception signal transmission antenna A plurality of reception signal receiving antennas for receiving transmitted reception signals, a signal selection means for selecting a reception signal received at a specific reception signal reception antenna among the plurality of reception signal reception antennas, and a signal selection means Reception data processing means for reconstructing an image of the subject from the selected reception signal.

JP 2007-203036 A

  The magnetic resonance imaging apparatus of Patent Document 1 reconstructs an image of a subject by selecting only one signal from a plurality of signals received by a plurality of coil reception signal reception functions based on the intensity thereof. There is a possibility that the signal strength is not sufficiently obtained, and noise may be increased.

  The present invention has been made in view of such a problem, and includes a wireless transmitter connected to an element coil in a receiving coil, and a signal processing system receiver paired with the wireless transmitter. Provided are a magnetic resonance imaging apparatus and a reception signal processing method in a magnetic resonance imaging apparatus capable of increasing received signal intensity and suppressing noise by appropriately synthesizing reception signals of respective reception coils at the time of imaging. For the purpose.

  A magnetic resonance imaging apparatus according to the present invention includes a reception coil that receives a nuclear magnetic resonance signal from a subject as a coil reception signal, at least one coil reception signal transmission unit that wirelessly transmits a coil reception signal of the reception coil, A plurality of coil reception signal receiving means for receiving a coil reception signal wirelessly transmitted by the coil reception signal transmitting means, and a signal combining means for adding and synthesizing each coil reception signal received by the plurality of coil reception signal receiving means. And reception data processing means for reconstructing the image of the subject from the coil reception signal synthesized by the signal synthesis means.

  The received signal processing method in the magnetic resonance imaging apparatus according to the present invention includes: a received signal transmitting step of wirelessly transmitting a coil received signal of a receiving coil that receives a nuclear magnetic resonance signal from a subject as a coil received signal; A coil reception signal reception step for receiving the coil reception signal wirelessly transmitted in the reception signal transmission step by a plurality of coil signal reception functions and each coil reception signal received in the coil reception signal reception step are added and synthesized. A signal synthesis step and a reception data processing step for reconstructing an image of the subject from the coil reception signal synthesized in the signal synthesis step are performed.

  According to the magnetic resonance imaging apparatus and the reception signal processing method in the magnetic resonance imaging apparatus according to the present invention, the radio transmitter connected to the element coil in the reception coil and the signal processing paired with the radio transmitter It is possible to increase the received signal intensity and suppress noise by appropriately combining the received signals of the respective receiving coils at the time of shooting.

1 is a configuration diagram showing a magnetic resonance imaging apparatus according to the present invention. The block diagram which shows the radio | wireless signal synthetic | combination function in the magnetic resonance imaging apparatus which concerns on this invention. The block diagram which shows the coil reception signal transmission means of the magnetic resonance imaging apparatus which concerns on this invention. The block diagram which shows the coil reception signal receiving means of the magnetic resonance imaging apparatus which concerns on this invention. The flowchart which shows the procedure at the time of the magnetic resonance imaging apparatus which concerns on this invention processes a received signal. The figure for demonstrating the process of the received signal in the magnetic resonance imaging apparatus which concerns on this invention.

  Embodiments of a magnetic resonance imaging apparatus according to the present invention and a received signal processing method in the magnetic resonance imaging apparatus will be described with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention. As shown in FIG. 1, the magnetic resonance imaging apparatus 1 includes a static magnetic field magnet 2, a gradient magnetic field coil 3, a high frequency transmission coil 4, a high frequency reception coil 5, a gradient magnetic field power source 6, a high frequency amplifier 7, and a control device 8. It is provided as a component.

  Among the components described above, the static magnetic field magnet 2, the gradient magnetic field coil 3, the high frequency transmission coil 4, and the high frequency reception coil 5 are provided on a gantry (not shown). The static magnetic field magnet 2 is formed in a cylindrical shape, and a cylindrical gradient magnetic field coil 3 is provided inside the static magnetic field. Further, an imaging region is formed inside the gradient magnetic field coil 3, and a bed 9, a high frequency transmission coil 4, and a high frequency reception coil 5 are provided.

  The bed 9 is provided with a bed control unit 10 on which the subject P is held. The bed control unit 10 can move the bed 9 in the body axis direction of the subject P (Z direction shown in FIG. 1). The bed control unit 10 is controlled by a control signal from the control device 8, and notifies the control device 8 of position information of the bed 9. Further, the high-frequency transmission coil 4 and the high-frequency reception coil 5 are also configured to be movable together with the bed 9.

  A gradient magnetic field power source 6 is connected to the gradient magnetic field coil 3, and a target gradient magnetic field can be formed in an imaging region in the gradient magnetic field coil 3 by a current supplied from the gradient magnetic field power source 6. The high frequency transmission coil 4 receives the high frequency transmission signal amplified to a predetermined intensity from the high frequency amplifier 7 and transmits the high frequency transmission signal toward the imaging region of the subject P set in the imaging region.

  The high frequency receiving coil 5 receives an NMR (Nuclear Magnetic Resonance) signal generated by transmitting a high frequency transmission signal to the subject P in the gradient magnetic field, and notifies the control device 8 as a high frequency reception signal. Here, the high frequency received signal output from the high frequency receiving coil 5 is configured to be notified to the control device 8 by radio.

  Note that the high-frequency transmission coil 4 and the high-frequency reception coil 5 may be a common coil. It is also possible to transmit a high frequency transmission signal from the high frequency amplifier 7 to the high frequency transmission coil 4 wirelessly. Here, the case where the high frequency transmission coil 4 and the high frequency reception coil 5 are separate coils and the high frequency reception signal is transmitted wirelessly will be described.

  For this reason, the high frequency receiving coil 5 is provided with a plurality of received signal transmitting antennas 11. On the other hand, a plurality of reception signal reception antennas 14 are fixed to a position where radio waves from the reception signal transmission antenna 11 can be received on an indoor wall, floor, ceiling, or the like where the main components of the magnetic resonance imaging apparatus 1 are installed. Yes. At this time, the plurality of reception signal reception antennas 14 are preferably fixed at different positions.

  Each reception signal transmission antenna 11 transmits the reception signal received from the high frequency reception coil 5 to each reception signal reception antenna 14 by radio. On the other hand, the reception signal reception antenna 14 receives the reception signal transmitted from the reception signal transmission antenna 11. Here, the transmission frequency of each reception signal transmission antenna 11 is set so that the frequency bands do not overlap each other.

  An amplifier 17 is provided at the output destination of the reception signal receiving antenna 14, and a frequency filter 18 is provided at the output destination of the amplifier 17. The amplifier 17 has a function of amplifying the reception signal having the tuning frequency received from each reception signal reception antenna 14 and applying the amplification signal to the frequency filter 18. The output destination of the frequency filter 18 is the control device 8. The frequency filter 18 extracts a reception signal having a specific frequency tuned in advance from reception signals having various frequencies received from the amplifier 17 and outputs the extracted reception signal to the control device 8.

  That is, the frequency filter 18 has a function of selecting a reception signal having a tuning frequency from a plurality of reception signals having different frequencies for each received reception signal reception antenna 14 and outputting the reception signal to the control device 8. With the function of the frequency filter 18, only the frequency generated from each reception signal transmission antenna 11 can be given to the control device 8 from the reception signal reception antenna 14.

  As described above, since the high-frequency reception signal can be transmitted and received between the control device 8 and the high-frequency reception coil 5 wirelessly, even if the high-frequency reception coil 5 moves together with the bed 9, the cable moving mechanism such as complicated wiring of the cable or retractor is provided. Is no longer necessary.

  The control device 8 has a signal processing system 19 and a transmission system 20. The transmission system 20 of the control device 8 is connected to the gradient magnetic field power supply 6 and the high frequency amplifier 7. The transmission system 20 sets a pulse sequence as an imaging condition, and controls the gradient magnetic field power source 6 and the high-frequency amplifier 7 by supplying a control signal according to the set pulse sequence. Thereby, a gradient magnetic field corresponding to the imaging condition is formed in the imaging region, and a high-frequency transmission signal is transmitted to the subject P.

  The signal processing system 19 of the control device 8 has a reception data processing unit 23. The reception data processing unit 23 reconstructs the image data of the subject P by performing preprocessing and image reconstruction processing on the reception signal given through the frequency filter 18. Thereby, an image photographed by the magnetic resonance imaging apparatus 1 is reconstructed.

  FIG. 2 is a block diagram showing a wireless signal synthesis function in the magnetic resonance imaging apparatus 1. As shown in FIG. 2, the high-frequency receiving coil 5 of the magnetic resonance imaging apparatus 1 receives a nuclear magnetic resonance signal from the subject P, and receives the nuclear magnetic resonance signal from the receiving coil 30 and the control apparatus 8. Coil receiving signal transmitting means 31 (receiving signal transmitting antenna 11 or the like) for transmitting to the mobile system.

  In addition, the magnetic resonance imaging apparatus 1 includes a plurality of coil reception signal receiving means 32 (such as the reception signal receiving antenna 14) that receive a coil reception signal from the coil reception signal transmission means 31, and a plurality of signals received by the coil reception signal receiving means 32. Signal synthesizing means 33 for synthesizing the signals of the received data processing means 34 (reception data processing means 34 for performing preprocessing and image reconstruction processing on the basis of the received signal synthesized by the signal synthesizing means 33 to recalibrate the image data of the subject P ( The reception data processing unit 23 and the like are provided in the fixed system.

  FIG. 3 is a configuration diagram illustrating the coil reception signal reception device 31. As shown in FIG. 3, the coil reception signal transmission means 31 transmits a reference signal generation device 31 a that generates a reference signal, an output signal (reference signal) generated from the reference signal generation device 31 a and the coil reception signal transmission means 31. Transmitting means 31b for switching and wirelessly transmitting the received coil reception signal is provided.

  FIG. 4 is a configuration diagram showing the coil reception signal receiving means 32. As shown in FIG. 4, the coil reception signal receiving means 32 receives the reference signal and the coil reception signal from the coil signal receiving device 31, identifies the reference signal, and detects the delay time from the reference time. A delay time detection setting means 32b and a reception signal delay means 32c for delaying and outputting the coil reception signal according to the detected delay time are provided.

  As described above, the magnetic resonance imaging apparatus 1 of the present invention receives a coil reception signal by a plurality of coil reception signal reception functions (coil reception signal reception means 32) during imaging, and each coil received by these is received. By appropriately combining the received signals, the received signal strength is increased and noise is suppressed.

  FIG. 5 shows a procedure for performing reception signal processing for appropriately synthesizing coil reception signals received by a plurality of coil reception signal reception means 32 and reconstructing an image when imaging is performed by the magnetic resonance imaging apparatus 1. This will be described based on a flowchart. Hereinafter, “step S101” will be described as “S101” with the word “step” omitted.

  When imaging with the magnetic resonance imaging apparatus 1, the high-frequency transmission coil 4 receives a high-frequency transmission signal amplified to a predetermined intensity from the high-frequency amplifier 7 and is directed toward the imaging region of the subject P set in the imaging region. A high frequency transmission signal is transmitted. The receiving coil 30 receives a nuclear magnetic resonance signal (NMR signal) generated by transmitting a high-frequency transmission signal to the subject P in the gradient magnetic field (S101).

  The coil reception signal transmission unit 31 transmits the coil reception signal received by the reception coil 30 to the coil reception signal reception unit 32 (S103). At this time, a plurality of coil reception signal receiving means 32 are provided at predetermined positions on the control device side, and each coil reception signal receiving means 32 receives the coil reception signal.

  Whether the position of the high frequency receiving coil 5 has been moved in order to determine whether the coil reception signal transmission means 31 needs to update the delay time of the coil reception signal after receiving the previous coil reception signal. Is determined (S105). At this time, the coil reception signal transmission means 31 receives, for example, a signal indicating the movement amount or position information of the bed 9 from the bed control unit 10 and whether or not the position of the high-frequency reception coil 5 has been moved based on this signal. Determine whether.

  When the position of the high-frequency receiving coil 5 is moved (Yes in S105), the coil reception signal transmitting unit 31 generates a reference signal by the reference signal generating unit 31a and the coil receiving signal receiving unit 32 by the transmitting unit 31b. On the other hand, this reference signal is transmitted (S107). When the signal synthesizing unit 32 receives the coil reception signal transmitted in step S103 and the reference signal transmitted in step S107, the delay time detection setting unit for each coil reception signal based on the reference signal. The delay time is calculated by 32a (S109).

  For example, as shown in FIG. 6, when the magnetic resonance imaging apparatus 1 is provided with coil reception signal receiving means A, B, and C as the coil reception signal receiving means 32, the signal synthesizing means 32 is connected to each coil reception signal. A time difference with respect to a reference signal (indicated by a dotted line in FIG. 6) in the coil reception signals received by the receiving means A, B, and C is calculated as a delay time.

  The signal synthesis means 32 adds and synthesizes each coil reception signal transmitted in step S103 by delaying by the delay time calculated in step S109 so as to match the phases (S111). At this time, when the bed is not moved in step S105 (No in S105), the delay time used last time may be used. Then, the reception data processing unit 34 reconstructs an image based on the data synthesized in step S111 (S113).

  In this way, the magnetic resonance imaging apparatus 1 calculates the delay time for each coil reception signal received by the plurality of coil reception signal reception means 32 using the reference signal, and considers this delay time and phase. The image is reconstructed based on the synthesized signal. Thereby, at the time of imaging | photography with the magnetic resonance imaging apparatus 1, a received signal intensity | strength can be raised and a noise can be suppressed.

  According to the magnetic resonance imaging apparatus 1 and the reception signal processing method in the magnetic resonance imaging apparatus 1 according to the present invention, a wireless transmitter (coil reception signal transmission means 31 and the like) connected to an element coil in the reception coil; A signal processing system receiver (coil reception signal receiving means 32 and the like) paired with this wireless transmitter is provided, and at the time of photographing, the reception signal of each reception coil is appropriately combined to receive the signal. The strength can be increased and noise can be suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Magnetic resonance imaging apparatus, 2 ... Static magnetic field magnet, 3 ... Gradient magnetic field coil, 4 ... High frequency transmission coil, 5 ... High frequency reception coil, 6 ... Gradient magnetic field power supply, 7 ... High frequency amplifier, 8 ... Control apparatus, 9 ... Bed , 10 ... Sleeper control unit, 11 ... Reception signal transmission antenna, 14 ... Reception signal reception antenna, 17 ... Amplifier, 18 ... Frequency filter, 19 ... Signal processing system, 20 ... Transmission system, 23 ... Reception data processing unit, 30 ... Receiving coil, 31 ... Coil signal receiving device, 31a ... Reference signal generating means, 31b ... Transmitting means, 32 ... Coil received signal receiving means, 32a ... Receiving means, 32b ... Delay time detection setting means, 32c ... Received signal delay means, 33: Signal combining means, 34: Received data processing means, P: Subject.

Claims (7)

A receiving coil for receiving a nuclear magnetic resonance signal from the subject as a coil reception signal;
At least one coil reception signal transmission means for wirelessly transmitting a coil reception signal of the reception coil;
A plurality of coil reception signal reception means for receiving a coil reception signal wirelessly transmitted by the coil reception signal transmission means;
Signal combining means for adding and synthesizing the respective coil reception signals received by the plurality of coil reception signal receiving means; and reception data processing means for reconstructing the image of the subject from the coil reception signals combined by the signal combining means When,
A magnetic resonance imaging apparatus comprising: When the coil reception signal transmission means wirelessly transmits the coil reception signal, the coil reception signal transmission means wirelessly transmits the reference signal together,
The coil reception signal reception means receives a reference signal when receiving the coil reception signal wirelessly transmitted by the coil reception signal transmission means, and each of the coil reception signals has a delay time with respect to the reference signal. To calculate
The signal synthesizing unit synthesizes each coil reception signal received by the coil reception signal reception unit so as to match the phase based on the delay time calculated by the coil reception signal reception unit. The magnetic resonance imaging apparatus according to claim 1. A detection means for detecting the movement of the bed,
The coil reception signal transmission means wirelessly transmits a reference signal when movement of the bed is detected by the detection means,
The coil reception signal reception means calculates a delay time when a reference signal is transmitted by the coil reception signal transmission means,
3. The magnetic resonance imaging apparatus according to claim 2, wherein when the delay time is calculated by the coil reception signal reception unit, the signal synthesis unit synthesizes each of the coil reception signals in phase.   The reception coil and the coil reception signal transmission unit are installed in a moving system, and the coil reception signal reception unit, the signal synthesis unit, and the reception data processing unit are installed in a fixed system. The magnetic resonance imaging apparatus according to 1. A reception signal transmission step of wirelessly transmitting a coil reception signal of a reception coil that receives a nuclear magnetic resonance signal from a subject as a coil reception signal;
A coil reception signal reception step for receiving the coil reception signal wirelessly transmitted in the reception signal transmission step with a plurality of coil signal reception functions;
A signal synthesis step of adding and synthesizing each coil reception signal received in the coil reception signal reception step; and a reception data processing step of reconstructing the image of the subject from the coil reception signal synthesized in the signal synthesis step When,
A method for processing a received signal in a magnetic resonance imaging apparatus. In the coil reception signal transmission step, when the coil reception signal is wirelessly transmitted, the reference signal is wirelessly transmitted together,
In the coil reception signal reception step, when receiving the coil reception signal wirelessly transmitted in the coil reception signal transmission step, a reference signal is also received, and each of the coil reception signals with respect to the reference signal Calculate the delay time,
In the signal synthesis step, the respective coil reception signals received in the coil reception signal reception step are synthesized so as to match the phases based on the delay time calculated in the coil reception signal reception step. The method of processing a received signal in a magnetic resonance imaging apparatus according to claim 5. Before performing the coil reception signal transmission step, perform a detection step of detecting the movement of the bed,
In the coil reception signal transmission step, when movement of the bed is detected in the detection step, a reference signal is wirelessly transmitted,
In the coil reception signal reception step, when a reference signal is transmitted in the coil reception signal transmission step, a delay time is calculated,
7. The magnetic resonance imaging apparatus according to claim 6, wherein when the delay time is calculated in the coil reception signal reception step in the signal combination step, the respective coil reception signals are combined in phase. Processing method of received signal in.

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