阅读说明：本技术 呼吸检测装置、方法及磁共振成像系统 (Respiration detection device and method and magnetic resonance imaging system ) 是由 汪坚敏 张秋艺 于 2019-08-21 设计创作，主要内容包括：本公开提供了呼吸检测装置、呼吸检测方法以及磁共振成像系统。该呼吸检测装置包括：发射线圈,被配置为发射用于检测受检体的呼吸运动的射频信号；接收线圈,被配置为接收呼吸接收信号,其中,所接收的呼吸接收信号包括射频干扰信号和呼吸调制信号,所述射频干扰信号为所述射频信号通过空间耦合直接到达所述接收线圈的信号,所述呼吸调制信号为所述射频信号经过所述受检体后被所述受检体的呼吸调制后又到达所述接收线圈的信号；去耦合模块,被配置为在磁共振系统扫描时生成与所述射频干扰信号相应的抵消信号,利用所述抵消信号抵消所述呼吸接收信号中的所述射频干扰信号并得到所述呼吸调制信号,以用于检测所述受检体的呼吸运动。(The present disclosure provides a respiration detection apparatus, a respiration detection method, and a magnetic resonance imaging system. The breath detection device includes: a transmit coil configured to transmit a radio frequency signal for detecting respiratory motion of a subject; the receiving coil is configured to receive a respiration receiving signal, wherein the received respiration receiving signal comprises a radio frequency interference signal and a respiration modulation signal, the radio frequency interference signal is a signal which directly reaches the receiving coil through spatial coupling, and the respiration modulation signal is a signal which reaches the receiving coil after the radio frequency signal passes through the subject and is modulated by the respiration of the subject; a decoupling module configured to generate a cancellation signal corresponding to the radio frequency interference signal when the magnetic resonance system scans, and cancel the radio frequency interference signal in the respiration receiving signal with the cancellation signal and obtain the respiration modulation signal for detecting the respiratory motion of the subject.)

1. A breath detection device comprising:

a transmit coil configured to transmit a radio frequency signal for detecting respiratory motion of a subject;

the receiving coil is configured to receive a respiration receiving signal, wherein the received respiration receiving signal comprises a radio frequency interference signal and a respiration modulation signal, the radio frequency interference signal is a signal which directly reaches the receiving coil through spatial coupling, and the respiration modulation signal is a signal which reaches the receiving coil after the radio frequency signal passes through the subject and is modulated by the respiration of the subject;

a decoupling module configured to generate a cancellation signal corresponding to the radio frequency interference signal when the magnetic resonance system scans, and cancel the radio frequency interference signal in the respiration receiving signal with the cancellation signal and obtain the respiration modulation signal for detecting the respiratory motion of the subject.

2. The apparatus of claim 1, wherein the decoupling module comprises:

a power splitter configured to split a signal generated by a signal generator into a first signal and a second signal, wherein the first signal is used to generate a cancellation signal and the second signal is used to provide the radio frequency signal to the transmit coil;

a phase shift attenuation module configured to perform phase shift and attenuation on the first signal according to a master control signal to obtain the cancellation signal;

an adder configured to add the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

3. The apparatus of claim 1, wherein the decoupling module comprises:

a first direct digital synthesizer configured to generate the radio frequency signal fed to the transmit coil according to a reference clock;

a second direct digital synthesizer configured to generate the cancellation signal from the reference clock and a master signal;

an adder configured to add the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

4. The apparatus of claim 3, wherein the first and second direct digital synthesizers are configured with output signal phase and amplitude adjustment functionality, respectively.

5. The apparatus of any of claims 1-4, wherein the decoupling module further comprises a communication interface configured to receive the master instructions from a master control system of a magnetic resonance imaging system, wherein the master instructions are generated by the master control system according to a pre-acquired amplitude and phase of a radio frequency interference signal received by the receive coil and are used to instruct generation of the cancellation signal having the same amplitude and opposite phase as the pre-acquired radio frequency interference signal.

6. The apparatus of any one of claims 1 to 4, wherein the decoupling module is disposed on a receive coil, the receive coil being a coil for detecting respiratory motion of the subject or a coil sensitive to respiratory modulation.

7. A breath detection method, comprising:

transmitting a radio frequency signal for detecting respiratory motion of a subject;

receiving a respiration receiving signal, wherein the received respiration receiving signal comprises a radio frequency interference signal and a respiration modulation signal, the radio frequency interference signal is a signal which directly reaches a receiving coil through spatial coupling, and the respiration modulation signal is a signal which reaches the receiving coil after the radio frequency signal passes through the subject and is modulated by the respiration of the subject;

and generating a cancellation signal corresponding to the radio frequency interference signal during scanning of a magnetic resonance system, and canceling the radio frequency interference signal in the respiration receiving signal by using the cancellation signal to obtain the respiration modulation signal so as to be used for detecting the respiratory movement of the detected body.

8. The method of claim 7, wherein generating a cancellation signal corresponding to the radio frequency interference signal during the magnetic resonance system scan, and using the cancellation signal to cancel the radio frequency interference signal in the respiration reception signal and obtain the respiration modulation signal comprises:

splitting a signal generated by a signal generator into a first signal and a second signal, wherein the first signal is used for generating a cancellation signal and the second signal is used for providing the radio frequency signal;

performing phase shift and attenuation on the first signal according to the main control signal to obtain the offset signal;

and adding the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

9. The method of claim 7, wherein generating a cancellation signal corresponding to the radio frequency interference signal during the magnetic resonance system scan, and using the cancellation signal to cancel the radio frequency interference signal in the respiration reception signal and obtain the respiration modulation signal comprises:

a first direct digital synthesizer generating said radio frequency signal fed to a transmit coil from a reference clock;

the second direct digital synthesizer generates the counteracting signal according to the reference clock and the main control signal;

and the adder adds the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

10. Magnetic resonance imaging system, wherein the magnetic resonance imaging system comprises a respiration detection apparatus according to any one of claims 1 to 6.

Technical Field

The present disclosure relates to the field of medical magnetic resonance, and in particular, to a respiration detection apparatus, a respiration detection method, and a magnetic resonance imaging system.

Background

Magnetic Resonance Imaging (MRI) is one of tomographic Imaging that obtains electromagnetic signals from a subject such as a human body using a Magnetic Resonance phenomenon and reconstructs human body information. Specifically, MRI generates a magnetic resonance phenomenon by applying a radio-frequency pulse of a certain frequency to a human body in a static magnetic field to excite hydrogen protons in the human body. After stopping the pulse, the protons produce a Magnetic Resonance (MR) signal during relaxation. Human body information is reconstructed through the processing processes of receiving the MR signals, encoding the MR signals, reconstructing images and the like.

In magnetic resonance imaging, respiratory motion of a subject degrades the quality of magnetic resonance images of a portion of the subject, such as the abdomen, which is affected by respiratory motion. In order to eliminate motion artifacts in magnetic resonance images caused by respiratory motion, respiratory motion of a subject is typically detected using a respiratory detection apparatus.

In an MRI system, in order to have a better scanning experience, real-time acquisition is required for respiration detection, which brings about a problem that when the MRI system is excited by magnetic resonance radio frequency, a radio frequency signal coupled from an MR receiving antenna heats an electronic device of a low noise amplifier, which causes a change in signal gain of a receiving link (a change in LNA gain caused by heating of radio frequency power), thereby affecting electronic components on a receiving link of the respiration detection, and further causing the real-time acquisition of a respiration curve to be affected to cause a respiration curve drift or so-called radio frequency pulse interference.

Fig. 1 is a schematic structural view of a respiration detection apparatus in an MRI system according to the related art, which includes a signal generator 10, a transmission coil 12, a reception coil 14, and an amplifier 16, as shown in fig. 1.

The radio frequency signal generated by the signal generator 10 is transmitted by the transmitting coil 12. The rf signal transmitted from the transmitting coil 12 reaches the receiving coil 14 through two paths, one path is the rf signal directly reaching the receiving coil 14 through spatial coupling, and the rf signal reaching the receiving coil 14 through the path is labeled as S1 in fig. 1 and is called an rf interference signal; the other path is the rf signal S2 passing through the subject 18, modulated by the respiration of the subject 18, and returning to the receive coil 14. the rf signal passing through this path to the receive coil 14 is labeled S3 in fig. 1 and is referred to as a respiration modulation signal. The respiration modulation signal S3 is a modulation signal with respiration required by the MRI system.

Assuming that the gain of the amplifier 16 of the receiving chain of the MRI system is G and the gain variation of the receiving chain caused during MRI transmission is Δ G, the expression formula of the respiration signal finally entering the MRI system is: s (S1+ S3) ((G +. DELTA.g)) ═ S1 × G + S1 × Δ G + S3 × G + S3 × Δ G. Since S1> > S3, the influence of S1 × Δ G is large. In the case that some subjects themselves have weak respiratory modulation, S1 Δ G > S3 Δ G, i.e., the radio frequency interference signal is larger than the respiratory modulation signal, which makes the extraction of the subsequent respiratory modulation signal very difficult.

For the variation of the gain of the received respiration signal caused by the radio frequency interference, there are two common methods to solve the problem.

The method comprises the following steps: a dedicated breath detection channel is designed. Fig. 2 is another structural diagram of a respiration detection apparatus in an MRI system according to the related art, as shown in fig. 2, which includes a signal generator 10, a transmission coil 12, a first receiving coil 20, a filter 22, a first amplifier 24, a second receiving coil 26, and a second amplifier 28. The transmit coil 12 and the first receive coil 20 for respiration detection use frequencies that are far from the frequency band of the MRI system, so that the rf energy from the spatial coupling can be filtered out by adding a filter 22 behind the first receive coil 20, so that the value of Δ G is small, thus ensuring the stability of the signal gain of the respiration receive channel.

Scheme II: the transmitting coil used for respiration detection is made small enough, the coupling of the transmitting coil and the receiving coil is optimized, and the signal S1 directly coupled to the receiving coil is reduced, so that the purpose of improving the signal stability of the respiration receiving channel is achieved.

For the first scheme, an additional independent signal receiving system needs to be designed, and the additional independent signal receiving system comprises an additional receiving coil, an additional low-noise amplifier and the like; and for the second scheme, higher requirements are put forward on decoupling design of the coil, the difficulty of coil design is increased, and in addition, due to the difference of the structure of the detected body, decoupling which is adjusted in advance can not be suitable for all application scenes when the MRI system works on line.

Disclosure of Invention

The present disclosure provides a respiration detection device, a respiration detection method, and a magnetic resonance imaging system, which at least solve the problems of high manufacturing cost, large difficulty in coil design, and poor decoupling effect of the respiration detection device in the related art.

According to an aspect of an embodiment of the present disclosure, there is provided a respiration detection apparatus including a transmission coil configured to transmit a radio frequency signal for detecting a respiratory motion of a subject; the receiving coil is configured to receive a respiration receiving signal, wherein the received respiration receiving signal comprises a radio frequency interference signal and a respiration modulation signal, the radio frequency interference signal is a signal which directly reaches the receiving coil through spatial coupling, and the respiration modulation signal is a signal which reaches the receiving coil after the radio frequency signal passes through the subject and is modulated by the respiration of the subject; a decoupling module configured to generate a cancellation signal corresponding to the radio frequency interference signal when the magnetic resonance system scans, and cancel the radio frequency interference signal in the respiration receiving signal with the cancellation signal and obtain the respiration modulation signal for detecting the respiratory motion of the subject.

In the breath detection device provided by the embodiment of the disclosure, the decoupling module is arranged, so that online real-time signal cancellation is realized, and the device has the advantages of low cost, simple coil design and good decoupling effect.

In one exemplary embodiment, the decoupling module includes: a power splitter configured to split a signal generated by a signal generator into a first signal and a second signal, wherein the first signal is used to generate a cancellation signal and the second signal is used to provide the radio frequency signal to the transmit coil; a phase shift attenuation module configured to perform phase shift and attenuation on the first signal according to a master control signal to obtain the cancellation signal; an adder configured to add the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

Through the structure, signal cancellation is carried out in real time, mutual decoupling of a transmitting coil and a receiving coil for respiration detection is not needed, the position of the receiving coil can be placed at will, and the design flow of the coil and the debugging flow of production are simplified.

In one exemplary embodiment, the decoupling module includes: a first direct digital synthesizer configured to generate the radio frequency signal fed to the transmit coil according to a reference clock; a second direct digital synthesizer configured to generate the cancellation signal from the reference clock and a master signal; an adder configured to add the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

Through the structure, the phase and the amplitude of an output signal can be simply adjusted by utilizing a Direct Digital Synthesizer (DDS), and online real-time decoupling is realized, so that the DDS has the advantages of simple structure and low cost.

In one illustrative embodiment, the first and second direct digital synthesizers are configured to have output signal phase and amplitude adjustment functions, respectively.

By configuring the DDS to have the function of adjusting the phase and the amplitude of the output signal, on-line decoupling can be realized more accurately, so that the DDS has the advantages of high precision and simple design.

In an exemplary embodiment, the decoupling module further includes a communication interface configured to receive the master instruction from a master control system of a magnetic resonance imaging system, wherein the master instruction is generated by the master control system according to an amplitude and a phase of a pre-acquired radio frequency interference signal received by the receiving coil, and is used to instruct generation of the cancellation signal with the same amplitude and opposite phase as the pre-acquired radio frequency interference signal.

Through the structure, the main control system acquires the amplitude and the phase of the radio frequency interference signal received by the receiving coil in advance before the MRI system starts scanning, and generates a main control instruction for adjusting the output amplitude and the phase of the offset signal, so that the effect of offsetting the radio frequency interference signal in real time on line is realized.

In an exemplary embodiment, the decoupling module is arranged on a receiving coil, wherein the receiving coil is a coil for detecting respiratory motion of the subject or a coil sensitive to respiratory modulation.

With the above-described structure, the decoupling module is provided on each of the plurality of receiving coils, and optimum decoupling can be achieved for each scanning object.

According to another aspect of an embodiment of the present disclosure, there is provided a respiration detection method including: transmitting a radio frequency signal for detecting respiratory motion of a subject; receiving a respiration receiving signal, wherein the received respiration receiving signal comprises a radio frequency interference signal and a respiration modulation signal, the radio frequency interference signal is a signal which directly reaches a receiving coil through spatial coupling, and the respiration modulation signal is a signal which reaches the receiving coil after the radio frequency signal passes through the subject and is modulated by the respiration of the subject; and generating a cancellation signal corresponding to the radio frequency interference signal during scanning of a magnetic resonance system, and canceling the radio frequency interference signal in the respiration receiving signal by using the cancellation signal to obtain the respiration modulation signal so as to be used for detecting the respiratory movement of the detected body.

In the method, the real-time on-line decoupling is realized by generating the counteracting signal corresponding to the radio frequency interference signal in real time on line, so that the decoupling effect is better.

In an exemplary embodiment, generating a cancellation signal corresponding to the radio frequency interference signal during a scan of a magnetic resonance system, and canceling the radio frequency interference signal in the respiration receiving signal and obtaining the respiration modulation signal using the cancellation signal includes: splitting a signal generated by a signal generator into a first signal and a second signal, wherein the first signal is used for generating a cancellation signal and the second signal is used for providing the radio frequency signal; performing phase shift and attenuation on the first signal according to the main control signal to obtain the offset signal; and adding the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

By the method, signal cancellation is carried out on line in real time without mutual decoupling of a transmitting coil and a receiving coil for respiration detection, and the position of the receiving coil can be randomly placed, so that the design flow and the debugging flow of production are simplified.

In an exemplary embodiment, generating a cancellation signal corresponding to the radio frequency interference signal during a scan of a magnetic resonance system, and canceling the radio frequency interference signal in the respiration receiving signal and obtaining the respiration modulation signal using the cancellation signal includes: a first direct digital synthesizer generating said radio frequency signal fed to a transmit coil from a reference clock; the second direct digital synthesizer generates the counteracting signal according to the reference clock and the main control signal; and the adder adds the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain the respiration modulation signal.

By utilizing the DDS with the output signal phase and amplitude adjusting function, the on-line real-time decoupling can be realized very simply, so that the DDS has the advantages of simple design and low cost.

According to a further aspect of an embodiment of the present disclosure, there is provided a magnetic resonance imaging system comprising a respiration detection apparatus as described in any of the above aspects.

By including the breath detection device capable of being decoupled on line in the MRI system, the breath detection receiving channel in the MRI system has higher stability and is not influenced by the state change of the electronic devices on the receiving link.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and not to limit the disclosure. In the drawings:

fig. 1 is a schematic configuration diagram of a respiration detection apparatus in an MRI system according to the related art;

fig. 2 is another structural schematic diagram of a respiration detection apparatus in an MRI system according to the related art;

fig. 3 is a schematic structural diagram of a breath detection device in an MRI system according to an embodiment of the present disclosure;

FIG. 4 is a schematic structural diagram of another breath detection device in an MRI system according to an embodiment of the present disclosure;

FIG. 5 is a flow chart of a method of breath detection in an MRI system according to an embodiment of the present disclosure; and

fig. 6 is a schematic diagram of an example of a computing device 600 of a portion of a hardware configuration of a master control system of an MRI system according to an embodiment of the present disclosure.

Reference numerals: 10. a signal generator; 12. a transmitting coil; 14. a receiving coil; 16. an amplifier; 20. a first receiving coil; 22. a filter 22; 24. a first amplifier; 26. a second receiving coil; 28. a second amplifier; 30. a power divider; 32. a phase shifter; 34. an attenuator; 36. an adder; 40. a reference clock 40; 42. a first DDS 42; 44. a second DDS; 600. a computing device; 610. a CPU; 620. a ROM; 630. a RAM; 640. a storage unit; 650. an input/output unit; 660. a communication unit.

Detailed Description

In order that those skilled in the art will better understand the disclosure, embodiments of the disclosure will be described more clearly and completely in conjunction with the accompanying drawings of the disclosure, and it is to be understood that the described embodiments are only a part of the embodiments of the disclosure, not all of them. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without inventive step, are within the scope of the present disclosure.

Fig. 3 is a schematic structural diagram of a respiration detection apparatus in an MRI system according to an embodiment of the present disclosure, which includes a signal generator 10, a transmission coil 12, a reception coil 14, an amplifier 16, a power divider 30, a phase shifter 32, an attenuator 34, and an adder 36, as shown in fig. 3. Wherein the power divider 30, the phase shifter 32, the attenuator 34 and the adder 36 constitute a decoupling module.

Before the MRI system starts scanning, a main control system of the MRI system acquires the amplitude and the phase of a radio frequency interference signal received by each receiving coil for detecting respiration in advance. Thereafter, the MRI system starts a scan and the signal generator 10 generates radio frequency signals.

A power divider 30 connected to the signal generator 10 divides the power of the signal generator 10 into two parts, one part of the power being supplied to the phase shifter 32 and the other part of the power being supplied to the transmission coil 12, wherein the power supplied to the phase shifter 32 is much smaller than the power supplied to the transmission coil 12. The rf signal generated by the signal generator 10 is divided into two paths by the power divider 30, wherein one path is the first signal S1₁Is passed to a phase shifter 32 and an attenuator 34 for generating a cancellation signal and the other, second signal, is passed to the transmit coil 12 for providing the transmit coil 12 with a radio frequency signal for detecting respiration.

The transmit coil 12 transmits the radio frequency signal distributed by the power divider 30. The receiving coil 14 receives the respiration receiving signal transmitted by the transmitting coil 12. As shown in fig. 3, the rf signal transmitted from the transmitting coil 12 reaches the receiving coil 14 through two paths, one path is that the rf signal directly reaches the receiving coil 14 through spatial coupling, and the rf signal reaching the receiving coil 14 through the path is labeled as S1 in fig. 3 and is called as an rf interference signal; the other path is the rf signal S2 passing through the subject 18, modulated by the respiration of the subject 18, and returning to the receive coil 14. the rf signal passing through this path to the receive coil 14 is labeled S3 in fig. 3 and is referred to as a respiration modulation signal. That is, the respiration receiving signal received by the receiving coil 14 includes the radio frequency interference signal S1 and the respiration modulation signal S3, the radio frequency interference signal S1 is a signal directly reaching the receiving coil 14 through spatial coupling, and the respiration modulation signal is a signal in which the radio frequency signal reaches the receiving coil 14 after being modulated by the respiration of the subject 18 after passing through the subject 18. The receive coil 14 delivers the received respiration receive signal to the adder 36.

Meanwhile, the decoupling module generates and transmits radio frequency on lineCancellation signal S1 corresponding to interference signal S1₂Using the cancellation signal S1₂Cancels the radio frequency interference signal S1 in the respiration reception signal and obtains a respiration modulation signal for detecting the respiratory motion of the subject 18.

In particular, the decoupling module receives a master instruction from a master control system of the magnetic resonance imaging system through its communication interface (not shown in fig. 3) for generating the cancellation signal S1₂. As mentioned above, before the MRI system starts scanning, the main control system of the MRI system has previously acquired the amplitude and phase of the radio frequency interference signal received by each receiving coil for detecting respiration. After the MRI system starts scanning, i.e. after the transmit coil 12 transmits the radio frequency signal for detecting respiration, the decoupling module distributes the first signal S1 distributed by the power distributor 30 through the communication interface₁And sending the data to a master control system. The main control system transmits the first signal S1 in real time according to the amplitude and phase of the pre-acquired radio frequency interference signal and the decoupling module₁Calculates the phase and attenuation values to which the first signal S1 should be adjusted, and generates a master signal according to the calculation result.

After receiving the main control signal of the main control system, the phase shifter 32 and the attenuator 34 of the decoupling module couple the first signal S1 according to the main control signal₁Performing phase shift and attenuation to obtain a cancellation signal S1 with the same amplitude and opposite phase as the pre-acquired radio frequency interference signal₂I.e. S1₂-S1. The attenuator 34 will generate a cancellation signal S1₂To adder 36.

Adder 36 will cancel signal S1₂And the respiratory receiving signal are added to cancel the radio frequency interference signal S1 in the respiratory receiving signal and obtain a respiratory modulation signal. The direct coupled rf interference signal S1 (also referred to as the carrier signal) is thus significantly reduced.

To achieve a more precise adjustment, such phase and amplitude adjustments may be made several times in succession to achieve complete cancellation of the radio frequency interference signal so that the signal entering the low noise amplifier 16 is only the respiratory modulation signal S3 with a very small carrier baseline, i.e.: (S1+ S1)₂+ S3 (G +. DELTA.g) ═ S3 (G + S3 (G) ×.DELTA.G). ByThe signals at S3 and Δ G are small, so the resulting respiration modulation signal of the MRI system isSo that the respiratory modulation signal is not affected by gain variations on the receive chain.

Fig. 4 is a schematic structural diagram of another breath detection device in an MRI system according to an embodiment of the present disclosure. The primary difference between the breath detection device of fig. 4 and the breath detection device of fig. 3 is that a DDS capable of internal phase and amplitude adjustment is used to achieve on-line decoupling. As shown in fig. 4, the breath detection apparatus includes a reference clock 40, a first DDS 42, a second DDS 44, a transmit coil 12, a receive coil 14, an adder 36, and an amplifier 16. In an embodiment of the present disclosure, first DDS 42, second DDS 44 and adder 36 constitute a decoupling module.

A first DDS 42 generates a radio frequency signal for detecting breathing that is fed to the transmit coil 12 in accordance with a reference clock 40.

The transmit coil 12 transmits radio frequency signals generated by the first DDS 42 for detecting respiratory motion of the subject. The receiving coil 14 receives the respiration receiving signal transmitted by the transmitting coil 12. As described above, the respiration receiving signal received by the receiving coil 14 includes the radio frequency interference signal S1 and the respiration modulation signal S3, the radio frequency interference signal S1 is a signal in which the radio frequency signal directly reaches the receiving coil 14 through spatial coupling, and the respiration modulation signal is a signal in which the radio frequency signal reaches the receiving coil 14 after being modulated by the respiration of the subject 18 after passing through the subject 18. The receive coil 14 delivers the received respiration receive signal to the adder 36.

At the same time, second DDS 44 generates a cancellation signal from the same reference clock and master control signal. The second DDS 44 generates a basic signal, i.e., a first signal, having the same frequency as the radio frequency signal transmitted by the transmitting coil 12 according to the reference clock, and sends the first signal to the master control system. As described above in the description of the breath detection device of fig. 3, the amplitude and phase of the radio frequency interference signal have been previously acquired by the master control system. At this time, after receiving the first signal, the main control system interferes according to the radio frequency acquired in advanceThe amplitude and phase of the signal and the first signal sent by the second DDS 44 calculate the phase and attenuation value to which the output signal of the second DDS 44 should be adjusted, and generate the master control signal according to the calculation result and send to the second DDS 44. Second DDS 44 adjusts output signal S1 of second DDS 44 according to the master control instruction₂To achieve the effect of canceling the S1 signal. In an exemplary embodiment of the present application, the second DDS 44 communicates with the host system via a two-wire Serial bus (I2C) or Serial Peripheral Interface (SPI) protocol.

The adder 36 adds the cancellation signal S1 sent by the second DDS 44₂And the respiratory receiving signal sent by the receiving coil 14 are added to cancel the radio frequency interference signal S1 in the respiratory receiving signal and obtain the respiratory modulation signal. In an exemplary embodiment of the present application, the adder may be implemented with a synthesizer or a coupler, for example.

The function of the present disclosure can be implemented very simply using a DDS having an output signal phase and amplitude adjustment function. There are many commercially available DDS chips that support arbitrary adjustment of the phase and amplitude of the output signal, such as AD9911, AD9914 of ADI.

In one embodiment of the disclosure, the decoupling module is arranged on a receiving coil, which is a coil for detecting respiratory motion of the subject or a coil sensitive to respiratory modulation. In this way, the coupling of the transmit coil and the receive coil for detecting breathing can be adjusted online. "on-line" in this disclosure refers to the MRI system beginning to scan while in a scanning state, as opposed to "off-line" which refers to the MRI system being in a non-scanning state.

Fig. 5 is a flowchart of a respiration detection method in an MRI system according to an embodiment of the present disclosure, as shown in fig. 5, the method including the steps of:

step S502, a radio frequency signal for detecting respiratory motion of the subject is transmitted.

The transmit coil transmits a radio frequency signal for detecting respiratory motion of the subject. The radio frequency signal of the transmitting coil is from a radio frequency signal of a signal generator or from a radio frequency signal generated by the DDS.

In step S504, a respiration reception signal is received.

The receiving coil receives a respiration receiving signal. The received respiration receiving signal is a mixed signal which comprises at least two types of signals, wherein one type of signal is a radio frequency interference signal which is directly reached to a receiving coil by a radio frequency signal transmitted from a transmitting coil through spatial coupling, and the other type of signal is a respiration modulation signal which is returned to the receiving coil after the radio frequency signal transmitted from the transmitting coil is modulated by the respiration of a detected body after passing through the detected body.

Step S506, a cancellation signal corresponding to the radio frequency interference signal is generated during the scanning of the magnetic resonance system, so as to cancel the radio frequency interference signal in the respiration receiving signal and obtain a respiration modulation signal.

Before the MRI system starts scanning, the main control system of the MRI system has previously acquired the amplitude and phase of the radio frequency interference signal received by each receiving coil for detecting respiration. After the MRI system starts scanning, that is, after the transmitting coil transmits the radio frequency signal for detecting respiration, the main control system of the MRI system calculates the phase and attenuation value to which the basic signal, that is, the first signal should be adjusted according to the amplitude and phase of the radio frequency interference signal acquired in advance, and generates the main control signal according to the calculation result. The base signal and the radio-frequency signal transmitted by the transmitting coil are derived from the same signal generator or generated according to the same reference clock signal, so that the base signal and the radio-frequency signal transmitted by the transmitting coil have the same frequency.

After receiving the master control signal sent by the master control system, the respiration detection device performs phase shifting and attenuation on the basic signal according to the master control signal to obtain a cancellation signal which has the same amplitude and opposite phase with the pre-acquired radio frequency interference signal. And adding the cancellation signal and the respiration receiving signal to cancel the radio frequency interference signal in the respiration receiving signal and obtain a respiration modulation signal.

In order to achieve more precise adjustment, the above steps S502 to S504 may be performed several times in succession, and adjustment of the phase and amplitude of the cancellation signal is performed to achieve complete cancellation of the radio frequency interference signal, so that the signal entering the low noise amplifier of the receiving link is only a respiratory modulation signal with a small carrier baseline. Thus, the analyzed respiration modulation signal and the signal of the gain change Δ G on the receiving link are both small, so that the respiration modulation signal finally obtained by the MRI system is not affected by the gain change on the receiving link.

Fig. 6 is a schematic diagram of an example of a computing device 600 of a portion of a hardware configuration of a master control system of an MRI system according to an embodiment of the present disclosure. As shown in fig. 6, the computing apparatus 600 may include a CPU 610 for performing overall control, a Read Only Memory (ROM) 620 for storing system software, a Random Access Memory (RAM) 630 for storing write/Read data, a storage unit 640 for storing various programs and data, an input/output unit 650 as an interface for input and output, and a communication unit 660 for implementing a communication function. Alternatively, the CPU 610 may be replaced by a processor such as a microprocessor MCU or a programmable logic device FPGA. The input/output unit 650 may include various interfaces such as an input/output interface (I/O interface), a Universal Serial Bus (USB) port (which may be included as one of the ports of the I/O interface), a network interface, and the like. It will be understood by those skilled in the art that the structure shown in fig. 6 is only an illustration, and does not limit the hardware configuration of the master control system. For example, computing device 600 may also include more or fewer components than shown in FIG. 6, or have a different configuration than shown in FIG. 6.

It should be noted that the CPU 610 described above may include one or more processors, and the one or more processors and/or other data processing circuitry may be referred to generally in this disclosure as a "master control system. The data processing circuitry may be embodied in whole or in part in software, hardware, firmware, or any combination thereof. Further, the data processing circuitry may be a single, stand-alone processing module, or incorporated, in whole or in part, into any of the other components in the computing device 600.

The storage unit 640 may be used to store software programs and modules of application software, such as program instructions/data storage devices corresponding to the master control instruction calculation method described in the present disclosure, and the CPU 610 may implement the above-described master control instruction calculation method by running the software programs and modules stored in the storage unit 640. The storage unit 640 may include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, storage unit 640 may further include memory located remotely from CPU 610, which may be connected to computing device 600 over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The communication unit 660 is used to receive or transmit data via a network. Specific examples of such networks may include wireless networks provided by a communications provider of computing device 600. In one example, the communication unit 660 includes a Network adapter (NIC) that can be connected to other Network devices through a base station so as to communicate with the internet. In one example, the communication unit 660 may be a Radio Frequency (RF) module for communicating with the internet in a wireless manner.

Embodiments of the present disclosure also provide a magnetic resonance imaging system comprising a breath detection device that can be decoupled online, for example the breath detection device described above with respect to fig. 3 or 4.

According to the respiration detection device, the respiration detection method and the magnetic resonance imaging system, the decoupling module or the on-line decoupling function is added, so that a receiving channel for respiration detection has high stability, is not influenced by the change of the state of an electronic device on a receiving link, and can be adjusted in real time for each receiving coil, so that the optimal decoupling can be realized for each scanning object. In addition, because real-time signal cancellation is used, mutual decoupling of a transmitting coil and a receiving coil for detecting respiration is not required, the position of the receiving coil can be placed at will, and the design flow and the debugging flow of production are simplified.

The foregoing is merely a preferred embodiment of the present disclosure, and it should be noted that modifications and embellishments could be made by those skilled in the art without departing from the principle of the present disclosure, and these should also be considered as the protection scope of the present disclosure.