A motion information detection method and device based on beat pilot tone under magnetic resonance

Abstract

The present invention discloses a motion information detection method and device based on a beat pilot tone under magnetic resonance imaging, which relates to the field of magnetic resonance imaging. The detection method includes the following steps: generating two signals through a signal source, wherein the two signals are high-frequency signals with adjustable amplitudes; filtering and amplifying the two signals separately to synthesize them into one output signal, transmitting the output signal through an antenna, and causing the output signal to carry motion state information after propagation; receiving and processing the beat pilot tone signal to obtain motion state information; and utilizing the motion state information to fuse MR data according to different imaging sequences to achieve image reconstruction. The present invention overcomes the problem of PT detection sensitivity, extending the non-contact, easy-to-install motion detection system to magnetic resonance systems of any field strength, eliminating the limitation of field strength on motion detection accuracy, significantly improving the sensitivity of motion detection, and having higher applicability.

Description

Technical Field

[0001] The present invention relates to the field of magnetic resonance imaging, and in particular to a motion information detection method and device based on beat pilot tone under magnetic resonance. Background Art

[0002] Magnetic resonance imaging (MRI) is one of the most commonly used medical imaging techniques today, capable of non-invasively examining the clear anatomical structure of living tissue, reflecting images of organic lesions, and providing physiological information that meets diverse diagnostic needs. When MRI is used to examine the chest and abdomen, motion artifacts often arise from normal physiological phenomena such as cardiac and respiratory movements. This complicates image analysis and diagnosis, potentially leading to misdiagnosis or repeated image acquisition. Therefore, accurate motion detection is crucial for resolving the imaging artifacts caused by human motion across multiple spatial and temporal dimensions.

[0003] However, traditional motion detection methods require the placement of multiple, complex, contact-based hardware devices (such as electrodes) on the patient, along with specialized MRI navigation sequences. These parameters often require adjustment for individual patients. The complex hardware installation not only prolongs MRI scan times, but also requires the use of female physicians for female patients.

[0004] Recently, it has been proposed to obtain motion information by inducing radio frequency (RF) signals close to, but not within, the signal band used for MR imaging (i.e., the Larmor frequency). These RF signals are called pilot tone (PT) signals. PT does not require additional hardware placed on the patient. The frequency of the transmitted signal is outside the operating band of the MRI system to avoid interference with imaging, but close enough to be modulated by patient motion and received by the receiving coil. This signal, which contains a certain degree of respiratory and cardiac motion information, can be separated from the image signal using a specific algorithm. Currently, integrated, small-scale PT devices are available. The PT transmitter transmits a single frequency signal that exceeds the imaging bandwidth but is within the oversampled readout band. The amplitude of the received pilot signal is modulated by patient motion and detected by the RF coil during readout along with the conventional MRI signal, providing a real-time motion reference.

[0005] The frequency of existing PT technology is limited by the Larmor frequency of the magnetic resonance system, and its accuracy in detecting human motion is limited. The Larmor frequency of a high-field MRI system corresponds to a wavelength of 1-4.7m (corresponding to a magnetic field strength of 7T-1.5T), which barely meets its detection accuracy. However, if used in a magnetic resonance system with a lower magnetic field strength, the wavelength will be longer, reaching over 27m at 0.25T, for example. Therefore, PT cannot sensitively detect body motion in medium- and low-field MRI. In addition, current PT technology is only effective in detecting respiratory motion in medium- and high-field conditions. Its detection capability for cardiac motion is limited, making it difficult to demodulate this tiny physiological motion. In actual imaging applications, ECG signals are still required. Furthermore, the frequency of the signal from existing PT devices on the market cannot be adjusted; it only has a fixed offset to the Larmor frequency of the magnetic resonance system. This signal is generated by harmonics of a standard clock oscillator and cannot be adjusted according to imaging parameters, resulting in poor universality.

[0006] Therefore, technicians in this field are committed to developing a motion information detection method and device based on beat pilot tone under magnetic resonance imaging, so as to achieve non-contact, high-sensitivity and simple detection of small movements of the patient's body during MRI scanning, including but not limited to normal physiological activities such as breathing movements and limb movements of the human body, thereby solving motion artifacts in imaging, improving imaging quality, and helping doctors better diagnose and treat patients. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to overcome the detection sensitivity problem of PT and detect small movements of the patient's body during MRI scanning with high sensitivity, thereby more thoroughly solving the motion artifacts in imaging.

[0008] To achieve the above object, the present invention provides a motion information detection method based on beat pilot tone under magnetic resonance, characterized in that the method comprises the following steps:

[0009] S101: Generate two signals through a signal source, wherein the two signals are high-frequency signals with adjustable amplitudes;

[0010] S103: filtering and amplifying the two signals respectively and synthesizing them into one output signal;

[0011] S105: transmitting the output signal through an antenna, and causing the output signal to carry motion state information after propagation;

[0012] S107: Receive and process the beat pilot tone signal to obtain the motion state information;

[0013] S109: According to different imaging sequences, the motion state information is used to perform fusion processing on the MR data to achieve image reconstruction.

[0014] Furthermore, in step S101, the two signals are high-frequency signals with an interval frequency equal to the desired pilot frequency, the interval frequency being outside the imaging bandwidth of the MRI system but still within the oversampling readout band, and the frequencies of the two signals are divided into f T and f T +f BPT , where f BPT =f larmor +f offset , f larmor is the Larmor frequency of the MRI system, f offset Used to adjust the frequency of the transmitted signal.

[0015] Furthermore, the frequency of the first signal of the two signals is set to 2.4 GHz, the frequency of the second signal is adjustable within the range of 2.4 GHz to 2.8 GHz, and the interval frequency of the two signals can be adjusted.

[0016] Furthermore, in step S103, after the two signals are synthesized, unnecessary spurs are filtered out by a low-pass filter, and a sinusoidal signal meeting a predetermined purity index is output.

[0017] Furthermore, in step S107, the processing of the beat pilot tone signal includes digital processing, filtering, and extracting the motion state information.

[0018] Furthermore, in step S109 , the MR data is fused in the image domain or in the k-space to reduce artifacts in the reconstructed image.

[0019] On the other hand, the present invention provides a motion information detection device based on beat pilot tone under magnetic resonance, characterized in that the device outputs the beat pilot tone signal according to any one of claims 1 to 6, and the device includes a signal generating device, an SMA female hole, a battery and an installation box, wherein,

[0020] The signal generating device includes a low-frequency control component and a radio frequency signal component, wherein the low-frequency control component and the radio frequency signal component communicate via the SPI protocol, and the radio frequency signal component generates two output signals, wherein the radio frequency signal component includes an attenuator, a power amplifier, and a combiner;

[0021] The SMA female hole is installed on the side of the installation box and is connected to an external antenna via an SMA cable to transmit the output signal;

[0022] The battery is a non-magnetic lithium battery, which supplies power to the device;

[0023] The housing of the installation box is an aluminum alloy housing, and the signal generating device and the battery are fixed in the installation box to achieve magnetic compatibility.

[0024] Furthermore, the device is configured to receive commands from a host computer, wherein the commands are used to modify the frequency and amplitude of the output signal.

[0025] Furthermore, among the two signals generated by the signal generating device, the frequency of the first signal is 2.4 GHz, the frequency of the second signal is 2.4 GHz to 2.8 GHz, the frequency of the second signal is adjustable, and the minimum step of the frequency adjustment of the second signal is 100 Hz. The amplitudes of the two signals are adjustable, and the adjustment range of the amplitude is -20 dBm to 20 dBm, and the minimum adjustment step is 0.5 dBm. The two signals share a common reference clock.

[0026] Furthermore, the second harmonic of the output signal is less than -50dB, the third harmonic is less than -70dB, the single-tone spurious is less than 60dBc, and the dual-tone 0dBm output is greater than 50dBc.

[0027] In a preferred embodiment of the present invention, the present invention has the following beneficial effects compared to the prior art:

[0028] 1. The present invention overcomes the problem of PT detection sensitivity and extends the contactless and easy-to-install motion detection system to magnetic resonance systems of any field strength, thus getting rid of the limitation of field strength on motion detection accuracy. It also has high sensitivity in medium and low field magnetic resonance systems and has higher applicability.

[0029] 2. The present invention can highly sensitively detect physiological and rigid body motion of the patient's body during MRI scanning, thereby more thoroughly resolving motion artifacts in imaging and significantly improving the sensitivity of motion detection;

[0030] 3. The present invention can finely adjust the frequency of the transmitted pilot signal to facilitate the adaptation of imaging parameters.

[0031] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of a motion information detection method according to a preferred embodiment of the present invention;

[0033] Figure 2 This is a principle block diagram of a circuit board of a motion information detection device according to a preferred embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the hardware link of a motion information detection device according to a preferred embodiment of the present invention;

[0035] Figure 4A schematic block diagram of a motion information detection device according to a preferred embodiment of the present invention;

[0036] Figure 5 Schematic diagram of the extraction and preprocessing process of BPT signals according to a preferred embodiment of the present invention;

[0037] Figure 6 A schematic diagram of image reconstruction using BPT signals according to a preferred embodiment of the present invention;

[0038] Figure 7 A schematic diagram showing a comparison of the rigid body motion correction effects of a preferred embodiment of the present invention;

[0039] Figure 8 Schematic diagram comparing the cardiac motion correction effects of a preferred embodiment of the present invention.

[0040] Among them: 1-ADF4350 chip, 2-HMC833 chip, 3-attenuator, 4-power amplifier, 5-combiner, 6-low-pass filter, 7-SMA female connector. DETAILED DESCRIPTION

[0041] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0042] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0043] like Figure 1 As shown, an embodiment of the present invention provides a motion information detection method based on beat pilot tone under magnetic resonance, which aims to achieve non-contact, high-sensitivity and simple detection of small movements of the patient's body during MRI scanning, including but not limited to normal physiological activities such as breathing movements and rigid body movements of the human limbs, thereby solving motion artifacts in imaging, improving imaging quality, and helping doctors to better diagnose and treat patients. At the transmitting end, by transmitting two high-frequency signals with an interval frequency of the required PT frequency, the interval frequency of the two transmitted signals is outside the imaging bandwidth but still within the oversampling readout band. The antenna position is adjusted so that the two transmitted signals are modulated by the patient's motion information after propagation, and because their frequencies are higher, the sensitivity to motion information detection is also stronger. Select the transmitting signal f TThe fundamental frequency is 2.4 GHz, and at this frequency, the wavelength is only 12.5 cm. Therefore, compared with PT, the Beat Pilot Tone (BPT) method has a much higher sensitivity to motion information (219 times). At the receiving end, due to the nonlinear characteristics of the preamplifier itself, the two high-frequency signals carrying motion modulation information will produce a second-order intermodulation effect, resulting in a beat pilot tone signal (i.e., f) with a frequency within the MR receiving bandwidth that carries motion modulation information. BPT ), which can be used to divide the continuously acquired MR data into different motion states in the image domain or k-space, and perform data fusion processing to reduce motion artifacts and improve the signal-to-noise ratio of the image.

[0044] The method for detecting motion information based on beat pilot tones under magnetic resonance provided by an embodiment of the present invention includes the following steps:

[0045] S101: Generate two signals through a signal source, wherein the two signals are high-frequency signals with adjustable amplitudes.

[0046] The signal source generates two signals with a high-frequency signal whose interval frequency is the pilot frequency. The interval frequency is outside the imaging bandwidth of the MRI system but still within the oversampling readout band. The frequencies of the two signals are divided into f T and f T +f BPT , where f BPT =f larmor +f offset , f larmor is the Larmor frequency of the MRI system, f offset Used to adjust the frequency of the transmitted signal. In a preferred embodiment of the present invention, to adapt to the Larmor frequency of magnetic resonance systems with different magnetic field strengths, the frequency of the first of the two signals is set to 2.4 GHz. For a magnetic resonance system with a magnetic field strength of 0.25 T, the frequency of the second signal is set to 2.41093 GHz, and the interval frequency between the two signals is 10.93 MHz. For a magnetic resonance system with a magnetic field strength of 1.5 T, the frequency of the second signal is set to 2.463534 GHz, and the interval frequency between the two signals is 63.534 MHz.

[0047] S103: filtering and amplifying the two signals respectively and synthesizing them into one output signal.

[0048] After the above two signals are synthesized, they are filtered out through a low-pass filter to remove unnecessary spurious signals and output a sinusoidal signal that meets the predetermined purity index.

[0049] S105: transmitting the output signal through an antenna, and causing the output signal to carry motion state information after propagation;

[0050] S107: Receive and process the beat pilot tone signal to obtain the motion state information.

[0051] The processing of the beat pilot tone signal includes digital processing, filtering, and extracting the motion state information, and finally obtaining the motion state information.

[0052] S109: According to different imaging sequences, the motion state information is used to perform fusion processing on the MR data to achieve image reconstruction.

[0053] Select to fuse the MR data in the image domain or k-space to reduce artifacts in the reconstructed image

[0054] In a preferred embodiment of the present invention, the present invention has the following beneficial effects compared to the prior art:

[0055] 1. The present invention overcomes the problem of PT detection sensitivity and extends the contactless and easy-to-install motion detection system to magnetic resonance systems of any field strength, thus getting rid of the limitation of field strength on motion detection accuracy. It also has high sensitivity in medium and low field magnetic resonance systems and has higher applicability.

[0056] 2. The present invention can highly sensitively detect physiological and rigid body motion of the patient's body during MRI scanning, thereby more thoroughly resolving motion artifacts in imaging and significantly improving the sensitivity of motion detection;

[0057] 3. The present invention can finely adjust the frequency of the transmitted pilot signal to facilitate the adaptation of imaging parameters.

[0058] like Figure 2 、 Figure 3 As shown, another embodiment of the present invention further provides a motion information detection device based on beat pilot tone under magnetic resonance, which outputs a beat pilot tone signal. The device includes a signal generating device, an SMA female hole 7, a battery and an installation box, wherein,

[0059] A signal generating device includes a low-frequency control component and a radio frequency signal component, which communicate via the SPI protocol. The radio frequency signal component generates two output signals and includes an attenuator 3, a power amplifier 4, and a combiner 5. Of the two signals generated by the signal generating device, the first signal has a frequency of 2.4 GHz, and the second signal has a frequency between 2.4 GHz and 2.8 GHz. The second signal frequency is adjustable with a minimum adjustment step of 100 Hz. The amplitudes of both signals are adjustable within a range of -20 dBm to 20 dBm with a minimum adjustment step of 0.5 dBm. The two signals share a common reference clock. The second harmonic of the output signal is less than -50 dB, the third harmonic is less than -70 dB, the single-tone spurious is less than 60 dBc, and the dual-tone 0 dBm output is greater than 50 dBc. The SMA female hole 7 is installed on the side of the installation box and is connected to the external antenna through an SMA wire to transmit the above-mentioned output signal; the battery is a non-magnetic lithium battery, which powers the motion information detection device; the shell of the installation box is an aluminum alloy shell, and the signal generating device and the battery are fixed in the installation box to achieve magnetic compatibility. The above-mentioned motion information detection device receives commands from the host computer through the serial port to modify the frequency and amplitude of the output signal.

[0060] The motion information detection device based on a metronomic pilot tone, provided in an embodiment of the present invention, utilizes non-magnetic components to create a metronomic pilot tone transmitter, and is integrated and miniaturized. This motion information detection device is equipped with a non-magnetic rechargeable battery and utilizes an aluminum alloy housing for magnetic compatibility, allowing it to be placed outside the magnet of an MRI system or within the magnet compartment.

[0061] The present invention will be described in detail below in conjunction with the preferred embodiments of the present invention.

[0062] Example 1

[0063] A motion information detection method based on beat pilot tone (BPT) under magnetic resonance is proposed, which transmits two high-frequency signals with an interval frequency of the required PT frequency: f T and f T +f BPT , where f BPT =f larmor +f offset , f larmor is the Larmor frequency of the MRI system, f offset Used to adjust and control the frequency of the transmitted signal so that the interval frequency of the two transmitted signals is outside the imaging bandwidth but still within the oversampling readout band. Adjust the antenna position so that both transmitted signals are modulated by the patient's motion information after propagation, and because their frequencies are higher, the sensitivity to motion information detection is also stronger. For example, at 0.25T, the corresponding Larmor frequency is 10.95MHz and the wavelength is 27.4m. Select the transmitted signal fT The fundamental frequency is 2.4 GHz, and at this frequency, the wavelength is only 12.5 cm. Therefore, compared with PT, the Beat Pilot Tone (BPT) method has a much higher sensitivity to motion information (219 times). At the receiving end, due to the nonlinear characteristics of the preamplifier itself, the two high-frequency signals carrying motion modulation information will produce a second-order intermodulation effect, resulting in a beat pilot tone signal (i.e., f) with a frequency within the MR receiving bandwidth that carries motion modulation information. BPT ), which can be used to divide the continuously acquired MR data into different motion states in the image domain or k-space, and perform data fusion processing to reduce motion artifacts and improve the signal-to-noise ratio of the image.

[0064] The motion information detection method based on the beat pilot tone BPT specifically includes the following steps:

[0065] 1) Two signal sources, one generates a GHz-level amplitude-adjustable signal, and the other generates an equivalent GHz-level frequency and amplitude-adjustable signal;

[0066] 2) The two signals are separately calibrated and controlled through attenuators;

[0067] 3) The two signals are amplified by power amplifiers respectively;

[0068] 3) Combine the two signals into one output through a combiner;

[0069] 4) Filter out unwanted spurious signals through a low-pass filter and output a sinusoidal signal that meets the purity requirements;

[0070] 5) Transmit the signal through the antenna and adjust the antenna position so that both transmitted signals carry the patient's movement information after propagation;

[0071] 6) Process the received BPT signal, perform filtering and other operations on it to obtain motion state information;

[0072] 7) According to different imaging sequences, the motion state information is used to choose to fuse the MR data in the image domain or k-space, ultimately reducing the artifacts of the reconstructed image.

[0073] like Figure 4 As shown, in a preferred embodiment of the present invention, a two-channel abdominal coil is used in a 0.25T MRI system, with the signal source frequencies set to 2.4 GHz on one channel and 2.41093 GHz on the other, for a difference frequency of 10.93 MHz. A 1.5T MRI system uses a 15-channel body coil, with the signal source frequencies set to 2.4 GHz on one channel and 2.463534 GHz on the other, for a difference frequency of 63.534 MHz.

[0074] like Figure 5 Figure 2 illustrates the BPT signal extraction and preprocessing process in a preferred embodiment of the present invention. A 10.93 MHz beat frequency ensures that the BPT signal is within the MR oversampling bandwidth while remaining outside the image signal bandwidth, preventing imaging. This ensures sufficient frequency separation from the image signal, allowing for easy frequency domain extraction of the signal. Subsequently, mean filtering with a window size of 10 is applied, and the DC component is removed by the filter, resulting in a smooth signal carrying motion information.

[0075] like Figure 6 As shown in FIG, a schematic diagram of image reconstruction using BPT signals in a preferred embodiment of the present invention. For abdominal examination, the imaging field of view is selected to be 192×192 mm. 2 The excitation slice thickness is 8mm, TR is 30ms, and TE is 12.5ms. The motion states corresponding to different times are obtained based on the BPT signal, and the k-space data corresponding to the same motion state are weighted and combined to reconstruct an image with a higher signal-to-noise ratio and fewer motion artifacts.

[0076] like Figure 7 As shown, the image on the left provided by the preferred embodiment of the present invention is an image reconstructed by using the head rigid body motion information extracted by the present invention, performing motion state phase separation, and data rearrangement. The image on the right is an image reconstructed by direct accumulation without using motion information. The motion artifacts in the image on the left are greatly reduced. Both images were obtained using a 0.25T magnetic resonance imaging device. Figure 8 As shown, the image on the left, provided by a preferred embodiment of the present invention, is reconstructed using heartbeat information extracted by the present invention, motion phase separation, and data rearrangement. The image on the right is reconstructed using heartbeat information extracted from an ECG. Both images are of comparable quality, and both were acquired using a 1.5T MRI machine.

[0077] Example 2

[0078] A motion information detection device based on beat pilot tones under magnetic resonance. The device's circuitry consists of a low-frequency control component and a radio frequency signal component, with the two hardware components being two circuit boards. The low-frequency control component includes an STM32F103C8T6 single-chip microcomputer with a serial port. It can receive commands from a host computer via the RS485 protocol and then send these commands to the radio frequency signal component's attenuator via the SPI protocol, thereby modifying the output signal frequency and amplitude. The radio frequency signal plane generates two frequency and amplitude adjustable signals using the ADF4350 chip 1 and the HMC833 chip 2: one at 2.4 GHz and one adjustable between 2.4 GHz and 2.8 GHz, with a minimum frequency adjustment step of 100 Hz. The amplitude adjustment range is -20 dBm to 20 dBm, with a minimum adjustment step of 0.5 dBm. Both signals share a common reference clock. After the output power of the two signals is controlled by attenuator 3, they are amplified by power amplifier 4 and then combined into one output through combiner 5. After final processing, the sinusoidal signal is output through SMA female connector 7. The second harmonic of the output signal is guaranteed to be less than -50dB, the third harmonic is less than -70dB, the single-tone spurious is less than 60dBc, the dual-tone 0dBm output is greater than 50dBc, and the output reaches -110dBm below 1GHz without considering intermodulation. This invention uses a non-magnetic lithium polymer battery to power the hardware circuit. The two hardware circuit boards and the non-magnetic lithium battery are fixed in a 10cm×5cm×2cm aluminum alloy shielding box to achieve magnetic compatibility. It can be placed outside the MRI scanner or inside the scanner room. An SMA female connector is reserved on the side of the aluminum alloy shielding box, which can be connected to an external antenna via an SMA cable to transmit a pilot signal into space. The output signal frequency and amplitude can be modified by receiving commands from the host computer via serial communication.

[0079] The output signal is connected to an antenna, which is fixed parallel to the surface of the body being scanned. The two transmitted signals accurately modulate subtle body motion information (such as breathing and heartbeat) during transmission. At the receiving end, second-order intermodulation occurs, resulting in a signal that can be received by the MR coil and carries high-precision human motion information. Finally, the receiving chain performs digitization, filtering, motion information extraction, motion state phase separation, and image reconstruction, resulting in images with a higher signal-to-noise ratio and reduced motion artifacts.

[0080] like Figure 2 The figure shows a principle block diagram of a motion information detection device according to a preferred embodiment of the present invention. Instructions are sent to the low-frequency plane processor via the host computer serial port, thereby controlling the power of the radio frequency plane signal.

[0081] like Figure 3Figure 2 shows a physical diagram of the hardware link of a preferred embodiment of the present invention. In the preferred embodiment of the present invention, the device has a size of 10 cm × 5 cm × 2 cm, can output a pure BPT signal with adjustable amplitude and frequency, and achieve magnetic compatibility. The ADF4350 chip 1 and the HMC833 chip 2 are used to generate two signal sources.

[0082] like Figure 4 As shown, it is a schematic block diagram of the system of a preferred embodiment of the present invention. In a 0.25T magnetic resonance system, a two-channel abdominal coil is used, the signal source frequency is set to 2.4 GHz on one channel and 2.41093 GHz on the other channel, and the difference frequency is 10.93 MHz.

[0083] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A motion information detection method based on beat pilot tone under magnetic resonance, characterized in that: The method comprises the following steps: S101: Generate two signals through a signal source, wherein the two signals are high-frequency signals with adjustable amplitudes; S102: filtering and amplifying the two signals respectively and then synthesizing them into one output signal; S103: transmitting the output signal through an antenna, and causing the output signal to carry motion state information after propagation; S104: Receive and process the beat pilot tone signal to obtain the motion state information; S105: According to different imaging sequences, the motion state information is used to perform fusion processing on the MR data to achieve image reconstruction.

2. The method according to claim 1, wherein In step S101, the two signals are high-frequency signals with an interval frequency of the required pilot frequency, and the interval frequency is outside the imaging bandwidth of the MRI system but still within the oversampling readout band. The frequencies of the two signals are divided into f T and f T +f BPT , where f BPT =f larmor +f offset , f larmor is the Larmor frequency of the MRI system, f offset Used to adjust the frequency of the transmitted signal, f T is the signal frequency.

3. The method according to claim 2, wherein The frequency of the first signal of the two signals is set to 2.4 GHz, the frequency of the second signal is adjustable within the range of 2.4 GHz to 2.8 GHz, and the interval frequency of the two signals can be adjusted.

4. The method according to claim 1, wherein In step S102, after the two signals are synthesized, unnecessary spurs are filtered out by a low-pass filter, and a sinusoidal signal meeting a predetermined purity index is output.

5. The method according to claim 1, wherein In step S104, the processing of the beat pilot tone signal includes digital processing, filtering, and extracting the motion state information.

6. The method according to claim 1, wherein In step S105 , the MR data is fused in the image domain or in the k-space to reduce artifacts in the reconstructed image.

7. A motion information detection device based on beat pilot tone under magnetic resonance, characterized in that: The device outputs the motion information detection method based on beat pilot tone according to any one of claims 1 to 6, and the device includes a signal generating device, an SMA female hole, a battery and an installation box, wherein, The signal generating device includes a low-frequency control component and a radio frequency signal component, wherein the low-frequency control component and the radio frequency signal component communicate via the SPI protocol, and the radio frequency signal component generates two output signals, wherein the radio frequency signal component includes an attenuator, a power amplifier, and a combiner; The SMA female hole is installed on the side of the installation box and is connected to an external antenna via an SMA cable to transmit the output signal; The battery is a non-magnetic lithium battery, which supplies power to the device; The housing of the installation box is an aluminum alloy housing, and the signal generating device and the battery are fixed in the installation box to achieve magnetic compatibility.

8. The device according to claim 7, wherein The device is configured to receive commands from a host computer, wherein the commands are used to modify the frequency and amplitude of the output signal.

9. The device according to claim 8, wherein Of the two signals generated by the signal generating device, the frequency of the first signal is 2.4 GHz, and the frequency of the second signal is 2.4 GHz to 2.8 GHz. The frequency of the second signal is adjustable, and the minimum step for adjusting the frequency of the second signal is 100 Hz. The amplitudes of the two signals are adjustable, and the adjustment range of the amplitude is -20 dBm to 20 dBm, with a minimum adjustment step of 0.5 dBm. The two signals share a common reference clock.

10. The device according to claim 9, wherein The second harmonic of the output signal is less than -50dB, the third harmonic is less than -70dB, the single-tone spurious is less than 60dBc, and the dual-tone 0dBm output is greater than 50dBc.

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