CN116250822A

CN116250822A - Motion information detection method and device based on beat pilot tone under magnetic resonance

Info

Publication number: CN116250822A
Application number: CN202310279735.1A
Authority: CN
Inventors: 张志勇; 孙浩宇; 陈素恩; 陈浩
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2023-03-21
Filing date: 2023-03-21
Publication date: 2023-06-13

Abstract

The invention discloses a motion information detection method and a motion information detection device based on beat pilot frequency tones under magnetic resonance, which relate to the field of magnetic resonance imaging, wherein the detection method comprises the following steps: generating two paths of signals through a signal source, wherein the two paths of signals are high-frequency signals with adjustable amplitudes; respectively filtering and amplifying the two paths of signals to synthesize one path of output signal, transmitting the output signal through an antenna, and carrying the motion state information after the output signal is transmitted; receiving and processing beat pilot frequency sound signals to obtain motion state information; and according to different imaging sequences, carrying out fusion processing on MR data by utilizing the motion state information to realize image reconstruction. The invention overcomes the problem of PT detection sensitivity, promotes a contactless motion detection system convenient to install to a magnetic resonance system with any field intensity, gets rid of the limitation of the field intensity on motion detection precision, can greatly improve the sensitivity of motion detection, and has higher applicability.

Description

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

Technical Field

The invention relates to the field of magnetic resonance imaging, in particular to a motion information detection method and device based on beat pilot tones under magnetic resonance.

Background

Magnetic resonance imaging (Magnetic Resonance Imaging, MRI) is one of the most commonly used medical detection means today, which is capable of detecting clear anatomical structures of tissue in vivo without damage, reflecting images of organic lesions, and providing physiological information meeting different diagnostic needs. When examining the chest and abdomen with MRI, motion artifacts caused by normal physiological phenomena such as heart and respiratory motion are often generated, which increases the difficulty of image analysis diagnosis and may lead to medical misdiagnosis or repeated image acquisition processes. Thus, accurate motion detection is critical to solving imaging artifacts created by motion in multiple spatial and temporal dimensions of the human body.

However, conventional motion detection methods require placing multiple contact-type complex hardware devices (e.g., electrode pads) on the patient for motion detection in conjunction with a dedicated magnetic resonance navigator sequence, and often require adjusting parameters for different patients. The hardware devices are cumbersome to install, not only to further extend the MRI examination time, but also to install contact devices requires configuration of the female physician for the female patient.

Recently, it has been proposed to obtain information about motion by inducing Radio Frequency (RF) signals that are close in Frequency but not in the signal band used for MR imaging (i.e. larmor Frequency), these Radio Frequency signals being referred to as Pilot Tone (PT) signals. PT does not require the placement of additional hardware devices on the patient, the frequency of the transmitted signal is outside the operating band of the MRI system to avoid interfering with the imaging, but it is close enough that it can be modulated by patient motion information and received by the receiving coil, separated from the image signal by a specific algorithm, which contains some degree of respiratory and cardiac motion information. Currently there are integrated small PT devices, PT transmitters transmit signals at a single frequency that exceeds the imaging bandwidth but is within the oversampling readout band. The received pilot signal amplitude is modulated by the patient's motion and detected by the radio frequency coil along with conventional magnetic resonance signals during readout to provide a real-time motion reference.

The existing PT technology frequency is limited by the Larmor frequency of the magnetic resonance system, and the accuracy of detecting human body movement is limited. The larmor frequency of the high-field MRI system is 1-4.7m (corresponding to the magnetic field strength of 7T-1.5T) corresponding to the wavelength, and the detection accuracy is barely achieved. However, when used in a magnetic resonance system with a relatively low magnetic field strength, the wavelength is longer, for example, 0.25T, and is up to 27m or more. PT therefore cannot sensitively detect body movement in low-and-medium-field MRI. In addition, the current PT technology has obvious effect only on detecting respiratory motion in medium-high fields, has limited detection capability on cardiac motion, and is difficult to demodulate the tiny physiological motion. Electrocardiographic signal assistance is also required in practical imaging applications. In addition, the frequency of the existing PT equipment signal in the market cannot be adjusted, only the Larmor frequency of the magnetic resonance system is subjected to fixed offset, the signal is generated by the harmonic wave of the standard clock oscillator, adjustment cannot be performed according to imaging parameters, and universality is poor.

Therefore, those skilled in the art have been working to develop a motion information detection method and apparatus based on beat pilot tone under magnetic resonance, which is to realize contactless, high sensitivity, and simple detection of small amplitude motion of the patient's body during MRI scanning, including but not limited to normal physiological activities such as respiratory motion and limb motion of the human body, so as to solve motion artifacts in imaging, improve imaging quality, and help doctors to better diagnose and treat the patient.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the present invention aims to overcome the problem of PT detection sensitivity, and detect small-amplitude motion of a patient's body during MRI scanning with high sensitivity, so as to more thoroughly solve motion artifacts in imaging.

In order to achieve the above object, the present invention provides a motion information detection method based on beat pilot tones under magnetic resonance, which is characterized in that the method comprises the following steps:

s101: generating two paths of signals through a signal source, wherein the two paths of signals are high-frequency signals with adjustable amplitudes;

s103: the two paths of signals are respectively filtered and amplified and then synthesized into one path of output signals;

s105: transmitting the output signal through an antenna, and enabling the output signal to carry motion state information after being transmitted;

s107: receiving and processing beat pilot frequency sound signals to obtain the motion state information;

s109: and according to different imaging sequences, carrying out fusion processing on MR data by utilizing the motion state information to realize image reconstruction.

Further, in the step S101, the two signals are high-frequency signals with an interval frequency of a desired pilot frequency, the interval frequency is 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 Wherein f _BPT ＝f _larmor +f _offset ，f _larmor Larmor frequency, f, for MRI system _offset For adjusting the frequency of the transmitted signal.

Further, the frequency of a first signal in the two paths of signals is set to be 2.4GHz, the frequency of a second signal is adjustable within 2.4 GHz-2.8 GHz, and the interval frequency of the two paths of signals can be adjusted.

Further, in step S103, the two paths of signals are combined and then filtered by a low-pass filter to remove unwanted spurious signals, so as to output sinusoidal signals meeting the predetermined index purity.

Further, in the step S107, the processing performed on the beat pilot tone signal includes digitizing, filtering, and extracting the motion state information.

Further, in the step S109, fusion processing is selected to be performed on the MR data in the image domain or k-space, so as to reduce artifacts in the reconstructed image.

In another aspect, the present invention provides a motion information detecting device based on beat pilot tones under magnetic resonance, characterized in that the device outputs beat pilot tone signals according to any one of claims 1-6, the device comprising signal generating means, SMA female holes, a battery and a mounting box, wherein,

the signal generating device comprises a low-frequency control component and a radio frequency signal component, wherein the low-frequency control component and the radio frequency signal component are communicated through an SPI protocol, the radio frequency signal component generates two paths of output signals, and the radio frequency signal component comprises an attenuator, a power amplifier and a combiner;

the SMA female hole is arranged on the side face of the installation box and is connected to an external antenna through an SMA wire to emit the output signal;

the battery is a non-magnetic lithium battery and is used for supplying power to the device;

the shell of the mounting box is an aluminum alloy shell, and the signal generating device and the battery are fixed in the mounting box to realize magnetic compatibility.

Further, the device is arranged to receive a command from the host computer, the command being used to modify the frequency and amplitude of the output signal.

Further, in the two paths of signals generated by the signal generating device, the frequency of the first path of signals is 2.4GHz, the frequency of the second path of signals is 2.4 GHz-2.8 GHz, the frequency of the second path of signals is adjustable, the minimum step of the frequency adjustment of the second path of signals is 100Hz, the amplitude of the two paths of signals is adjustable, the adjusting range of the amplitude is-20 dBm, the minimum step of the adjustment is 0.5dBm, and the two paths of signals share a reference clock.

Further, 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 60dBc, and the double-tone 0dBm output is greater than 50dBc.

In the preferred embodiment of the invention, compared with the prior art, the invention has the following beneficial effects:

1. the invention overcomes the problem of PT detection sensitivity, promotes a contactless motion detection system which is convenient to install to a magnetic resonance system with any field intensity, gets rid of the limit of the field intensity on motion detection precision, has higher sensitivity in a middle-low field magnetic resonance system and has higher applicability;

2. the invention detects the physiology and rigid motion of the patient body during MRI scanning with high sensitivity, thereby more thoroughly solving the motion artifact in imaging and greatly improving the sensitivity of motion detection;

3. the invention can finely adjust the frequency of the transmitted pilot signal, and is convenient for adapting the imaging parameters.

The conception, specific structure, and technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, features, and effects of the present invention.

Drawings

FIG. 1 is a flow chart of a motion information detection method according to a preferred embodiment of the present invention;

FIG. 2 is a schematic block diagram of a circuit board of a motion information detection apparatus according to a preferred embodiment of the present invention;

FIG. 3 is a schematic diagram of a hardware link of the motion information detecting device according to a preferred embodiment of the present invention;

FIG. 4 is a schematic block diagram of a system of motion information detection apparatus according to a preferred embodiment of the present invention;

FIG. 5 is a schematic diagram of the process of extracting and preprocessing BPT signals according to a preferred embodiment of the present invention;

FIG. 6 is a schematic diagram of image reconstruction using BPT signals according to a preferred embodiment of the present invention;

FIG. 7 is a comparative schematic diagram of the correction effect on rigid motion according to a preferred embodiment of the present invention;

fig. 8 is a schematic diagram showing the correction effect on the heart beat motion according to a preferred embodiment of the present invention.

Wherein: 1-ADF4350 chip, 2-HMC833 chip, 3-attenuator, 4-power amplifier, 5-combiner, 6-low pass filter, 7-SMA mother hole.

Detailed Description

The following description of the preferred embodiments of the present invention refers to the accompanying drawings, which make the technical contents thereof more clear and easy to understand. The present invention may be embodied in many different forms of embodiments and the scope of the present invention is not limited to only the embodiments described herein.

In the drawings, like structural elements are referred to by like reference numerals and components having similar structure or function are referred to by like reference numerals. The dimensions and thickness of each component shown in the drawings are arbitrarily shown, and the present invention is not limited to the dimensions and thickness of each component. The thickness of the components is exaggerated in some places in the drawings for clarity of illustration.

As shown in fig. 1, the motion information detection method based on beat pilot tone under magnetic resonance provided by the embodiment of the invention is to realize contactless and high-sensitivity detection of small-amplitude motion of a patient body during MRI scanning, including but not limited to normal physiological activities such as respiratory motion and limb rigid motion of a human body, so as to solve motion artifacts in imaging, improve imaging quality and help doctors to better diagnose and treat the patient. At the transmitting end, by transmitting two high-frequency signals with the interval frequency being the required PT frequency, the interval frequency of the two paths of transmitted signals is outside the imaging bandwidth but still in the oversampling reading band. The antenna position is adjusted so that both signals transmitted are modulated by the motion information of the patient after being transmitted, and the sensitivity to motion information detection is stronger because of the higher frequency of the signals. Selecting the transmit signal f _T Is 2.4GHz, at which the wavelength is only 12.5cm. The sensitivity of the Beat Pilot Tone (BPT) method to motion information is greatly improved (219 times) compared to PT. At the receiving end, due to the nonlinear characteristic of the preamplifier, two paths of high-frequency signals carrying motion modulation information can generate second-order intermodulation effect to obtain a beat pilot tone signal (f _BPT ) The signal can be used for dividing the MR data which are continuously acquired into different motion states in an image domain or k space and carrying out data fusion processing, thereby reducing motion artifacts and improving the signal-to-noise ratio of the image.

The motion information detection method based on beat pilot frequency sound under magnetic resonance provided by the embodiment of the invention comprises the following steps:

s101: two paths of signals are generated through a signal source, and the two paths of signals are high-frequency signals with adjustable amplitude.

A high frequency signal with a pilot frequency as a spacing frequency of two signals generated by the signal source, the spacing frequency being outside the imaging bandwidth of the MRI system but still within the oversampled readout band, the two signals having frequencies divided into f _T And f _T +f _BPT Wherein f _BPT ＝f _larmor +f _offset ，f _larmor Larmor frequency, f, for MRI system _offset For adjusting the frequency of the transmitted signal. In a preferred embodiment of the invention, in order to adapt larmor frequency of magnetic resonance systems with different magnetic field strengths, the first signal frequency of the two signals is set to be 2.4GHz, and for a magnetic resonance system with a magnetic field strength of 0.25T, the second signal frequency is set to be 2.41093GHz, and the interval frequency of the two signals is 10.93MHz; for a magnetic resonance system with a magnetic field strength of 1.5T, the second signal frequency is set to 2.463534GHz, and the interval frequency of the two signals is 63.534MHz.

S103: and respectively filtering and amplifying the two paths of signals to synthesize one path of output signal.

The two paths of signals are synthesized and then are filtered by a low-pass filter to remove unwanted spurious signals, and sinusoidal signals meeting the purity of preset indexes are output

s107: and receiving and processing the beat pilot tone signal to obtain the motion state information.

The processing of the beat pilot frequency sound signal comprises digital processing, filtering and extracting the motion state information, and finally the motion state information is obtained.

Selecting to fusion process the MR data in image domain or k-space to reduce artifacts in reconstructed images

As shown in fig. 2 and 3, another embodiment of the present invention further provides a motion information detecting device based on beat pilot tones under magnetic resonance, which outputs beat pilot tone signals, the device comprising a signal generating device, an SMA female hole 7, a battery and a mounting box, wherein,

the signal generating device comprises a low-frequency control part and a radio frequency signal part, wherein the low-frequency control part and the radio frequency signal part are communicated through an SPI protocol, the radio frequency signal part generates two paths of output signals, and the radio frequency signal part comprises an attenuator 3, a power amplifier 4 and a combiner 5. The frequency of the first path of signals is 2.4GHz, the frequency of the second path of signals is 2.4 GHz-2.8 GHz, the frequency of the second path of signals is adjustable, the minimum step of the frequency adjustment of the second path of signals is 100Hz, the amplitude of the two paths of signals is adjustable, the adjustment range of the amplitude is-20 dBm, the minimum step of the adjustment is 0.5dBm, the two paths of signals share a reference clock, the second harmonic of the output signals is less than-50 dB, the third harmonic is less than-70 dB, the single-tone spurious is less than 60dBc, and the output of the double-tone 0dBm is greater than 50dBc. The SMA female hole 7 is arranged on the side surface of the mounting box and is connected to an external antenna through an SMA wire to emit the output signal; the battery is a non-magnetic lithium battery and is used for supplying power to the motion information detection device; the shell of the mounting box is an aluminum alloy shell, the signal generating device and the battery are fixed in the mounting box, magnetic compatibility is realized, and the motion information detecting device receives a command from the upper computer through the serial port to modify the frequency and the amplitude of an output signal.

The motion information detection device based on the beat pilot frequency sound provided by the embodiment of the invention uses the non-magnetic device to manufacture the beat pilot frequency sound emission device and is integrated into a small size. The motion information detection device is provided with a non-magnetic rechargeable battery, realizes magnetic compatibility by using an aluminum alloy shell, and can be placed outside or in a magnet of a magnetic resonance imaging system.

The present invention will be described in detail with reference to preferred embodiments thereof.

Example 1

A motion information detection method based on beat pilot frequency sound BPT under magnetic resonance is characterized by transmitting two high-frequency signals with interval frequency of required PT frequency: f (f) _T And f _T +f _BPT Wherein f _BPT ＝f _larmor +f _offset ，f _larmor Larmor frequency, f, for MRI system _offset For adjusting the control transmit signal frequency such that the spacing frequency of the two transmit signals is outside the imaging bandwidth but still within the oversampled readout band. The antenna position is adjusted so that both signals transmitted are modulated by the motion information of the patient after being transmitted, and the sensitivity to motion information detection is stronger because of the higher frequency of the signals. For example, at 0.25T, the corresponding Larmor frequency is 10.95MHz and the wavelength is 27.4m. Selecting the transmit signal f _T Is 2.4GHz, at which the wavelength is only 12.5cm. The sensitivity of the Beat Pilot Tone (BPT) method to motion information is greatly improved (219 times) compared to PT. At the receiving end, due to the nonlinear characteristic of the preamplifier, two paths of high-frequency signals carrying motion modulation information can generate second-order intermodulation effect to obtain a beat pilot tone signal (f _BPT ) The signal can be used for dividing the MR data which are continuously acquired into different motion states in an image domain or k space and carrying out data fusion processing, thereby reducing motion artifacts and improving the signal-to-noise ratio of the image.

The motion information detection method based on the beat pilot tone BPT specifically comprises the following steps:

1) Two signal sources, one of which generates GHz level amplitude adjustable signals and the other of which generates GHz level frequency and amplitude adjustable signals;

2) The two paths of signals are respectively subjected to power calibration control through an attenuator;

3) The two paths of signals are respectively amplified by the power amplifier;

3) Synthesizing two paths of signals into one path of signal to be output through a combiner;

4) Filtering unnecessary strays through a low-pass filter, and outputting sinusoidal signals conforming to index purity;

5) Transmitting signals through an antenna, and adjusting the position of the antenna so that the transmitted two paths of signals carry the motion information of the patient after being transmitted;

6) Processing the received BPT signal, filtering the BPT signal and other operations to obtain motion state information;

7) And according to different imaging sequences, the motion state information is utilized to select to fuse MR data in an image domain or k space, and finally, the artifact of a reconstructed image is reduced.

In the preferred embodiment of the present invention, as shown in fig. 4, a two-channel abdominal coil is used under a 0.25T magnetic resonance system, with one signal source frequency set at 2.4GHz and one 2.41093GHz, and the difference frequency set at 10.93MHz. Under a 1.5T magnetic resonance system, a 15-channel body coil is adopted, one path of signal source frequency is set to be 2.4GHz, the other path is set to be 2.463534GHz, and the difference frequency is 63.534MHz.

As shown in fig. 5, the process of extracting and preprocessing BPT signals according to the preferred embodiment of the present invention is shown. The difference frequency of 10.93MHz ensures that the BPT signal is within the MR oversampling bandwidth and outside the image signal bandwidth without affecting imaging. While maintaining a sufficient frequency separation from the image signal, the signal can be conveniently extracted in the frequency domain. And then filtering by adopting an average value with the window number of 10, and removing a direct current component through the filter to obtain a smooth signal carrying motion information.

As shown in fig. 6, a preferred embodiment of the present invention uses BPT signals for image reconstruction. For abdominal examinations, an imaging field of view of 192X 192mm was selected ² The excitation layer thickness was 8mm, TR 30ms and TE 12.5ms. And obtaining motion states corresponding to different times according to the BPT signals, and weighting and combining k-space data corresponding to the same motion state, so as to finally reconstruct an image with higher signal-to-noise ratio and fewer motion artifacts.

As shown in fig. 7, the left image provided by the preferred embodiment of the present invention is an image reconstructed after the motion state phase separation and the data rearrangement is performed by using the head rigid motion information extracted by the present invention, and the right image is an image reconstructed by directly accumulating without using the motion information. The motion artifact of the left image is greatly reduced. Both images were obtained under a 0.25T magnetic resonance apparatus. As shown in fig. 8, the left image provided by the preferred embodiment of the present invention is an image reconstructed by performing motion state phase separation and data rearrangement using the heartbeat information extracted by the present invention, and the right image is an image reconstructed by extracting the heartbeat information using ECG. The quality of the left image and the right image is equivalent, and both images are obtained under 1.5T magnetic resonance equipment.

Example 2

A motion information detection device based on beat pilot frequency sound under magnetic resonance is characterized in that a circuit part of the device is divided into a low-frequency control part and a radio frequency signal part, and the two hardware parts are two circuit boards. The low-frequency control part is provided with an STM32F103C8T6 singlechip, a serial port is led out, a command can be received from an upper computer through an RS485 protocol, and the command is sent to an attenuator of the signal emitting part through an SPI protocol, so that the frequency and the amplitude of an output signal are modified. The radio frequency signal surface generates two paths of frequency signals through the ADF4350 chip 1 and the HMC833 chip 2, and the amplitude of the signals is respectively adjustable: one path is 2.4GHz, the other path is adjustable at 2.4 GHz-2.8 GHz, and the minimum step of frequency adjustment is 100Hz. The amplitude adjusting range is-20 dBm, the minimum step is adjusted to be 0.5dBm, and the two paths of signals share the reference clock. The two paths of signals are respectively amplified by a power amplifier 4 after the output power is controlled by an attenuator 3, and then are synthesized into one path of output by a combiner 5, and finally are processed and output sinusoidal signals by an SMA female hole 7. The second harmonic of the output signal is ensured to be smaller than-50 dB, the third harmonic is ensured to be smaller than-70 dB, the single-tone spurious is smaller than 60dBc, the output of double tones of 0dBc is larger than 50dBc, and the intermodulation is not considered below 1GHz to reach-110 dBm. The invention adopts a non-magnetic lithium polymer battery to supply power to the hardware circuit. The two hardware circuit boards and the non-magnetic lithium battery are fixed in an aluminum alloy shielding box with the length of 10cm multiplied by 5cm multiplied by 2cm, so that magnetic compatibility is realized, and the two hardware circuit boards and the non-magnetic lithium battery can be placed outside an MRI scanner or in a scanner room. The side surface of the aluminum alloy shielding box is provided with an SMA female hole interface, and the SMA female hole interface can be connected to an external antenna through an SMA wire to transmit pilot signals to the space. The command can be received from the upper computer through serial communication mode, and the frequency and amplitude of the output signal can be modified.

The output signal is connected to the antenna, and the plane of the antenna is fixed above the scanned part of the human body in parallel. The two signals transmitted can correctly modulate the fine motion information (such as respiration and heartbeat motion) of the human body in the propagation process. And a second-order intermodulation effect occurs at the receiving end, so that a signal which can be received by the MR coil and carries high-precision human motion information is obtained. Finally, the receiving link is used for carrying out the treatments of digitalization, filtering, motion information extraction, motion state phase separation, image reconstruction and the like, and the image with higher signal to noise ratio and less motion artifact is obtained.

As shown in fig. 2, a schematic block diagram of a motion information detecting apparatus according to a preferred embodiment of the present invention is shown. And sending an instruction to the low-frequency surface processor through the serial port of the upper computer so as to control the power of the radio-frequency surface signal.

As shown in fig. 3, which is a hardware link physical diagram of a preferred embodiment of the present invention, in the preferred embodiment of the present invention, the device has a size of 10cm×5cm×2cm, and can output pure BPT signals with adjustable amplitude and frequency, and achieve magnetic compatibility, wherein an ADF4350 chip 1 and an HMC833 chip 2 are used to generate two signal sources.

As shown in fig. 4, which is a schematic block diagram of a system according to a preferred embodiment of the present invention, under a 0.25T magnetic resonance system, two-channel abdomen coils are used, the signal source frequency is set to 2.4GHz in one channel, 2.41093GHz in the other channel, and the difference frequency is 10.93MHz.

The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims

1. A method for detecting motion information based on beat pilot tones under magnetic resonance, the method comprising the steps of:

2. The method of claim 1, wherein in the step S101, the two signals are high frequency signals with an interval frequency of a desired pilot frequency, the interval frequency being outside an imaging bandwidth of the MRI system but still within an oversampled readout band, the frequencies of the two signals being divided into f _T And f _T +f _BPT Wherein f _BPT ＝f _larmor +f _offset ，f _larmor Larmor frequency, f, for MRI system _offset For adjusting the frequency of the transmitted signal.

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

4. The method of claim 1, wherein in step S103, the two signals are synthesized to further filter unwanted spurious signals by a low-pass filter, and a sinusoidal signal meeting a predetermined index purity is output.

5. The method of claim 1, wherein the processing of the beat pilot tone signal in step S107 includes digitizing, filtering, and extracting the motion state information.

6. Method according to claim 1, wherein in step S109 a fusion process of the MR data in the image domain or k-space is selected, reducing artifacts in the reconstructed image.

7. A motion information detecting device based on beat pilot tone under magnetic resonance, characterized in that the device outputs beat pilot tone signals according to any one of claims 1-6, the device comprising signal generating means, SMA female holes, a battery and a mounting box, wherein,

8. An apparatus as claimed in claim 7, wherein the apparatus is arranged to receive a command from a host computer, the command being used to modify the frequency and amplitude of the output signal.

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

10. The apparatus of claim 9, wherein the output signal has a second harmonic of less than-50 dB, a third harmonic of less than-70 dB, a single tone spur of less than 60dBc, and a double tone 0dBm output of greater than 50dBc.