Method, apparatus, system and storage medium for reducing radio frequency interference

Abstract

An embodiment of the present invention discloses a method, apparatus, system and storage medium for reducing radio frequency interference. Among them, the method includes: for an interference signal with a known and stable interference frequency falling within the system application bandwidth, if the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, obtaining a set number of sampling point data of the interference signal within one synchronous period of the acquisition; obtaining reference interference data within one synchronous period based on the set number of sampling point data; within each synchronous period, obtaining a system signal with the interference signal, obtaining system sampling data; using the system sampling data to subtract the reference interference data correspondingly to obtain system data with reduced interference. The technical solution in the embodiment of the present invention can reduce the interference falling within the system application bandwidth.

Description

Technical Field

[0001] The present invention relates to the medical field, and in particular to a method, device, system and storage medium for reducing radio frequency interference in the digital domain. Background Art

[0002] Some systems, such as magnetic resonance imaging (MRI) systems, are very sensitive to radio frequency interference. Taking the MRI system as an example, with the increase in the complexity of the magnetic resonance system, it is easy to introduce noise from other components. The interference sources can be divided into external interference and internal interference. External interference is quite complex, such as from non-magnetic resonance devices like mobile phones and FM radios. Internal interference generally comes from MRI system components. For example, the clock for driving digital chips, the communication data stream between components, etc.

[0003] There are different methods for dealing with different types of interference. For external interference, a shielded room can be used to provide a clean environment for the MRI system; filters can also be added at the joints connecting the inside and outside (filter board). For internal interference, components can be shielded; filters can be appropriately added in the design; dedicated frequency planning can be used to limit the possible interference frequencies to 2.5 MHz and its multiple frequencies; narrowband filters can also be constructed in the digital domain.

[0004] However, if the noise is within the system application bandwidth of the MRI (i.e., the frequency band used to acquire MRI image data), it will affect the image quality, and the above methods will be ineffective. For this reason, those skilled in the art are still working on finding other interference cancellation techniques. Summary of the Invention

[0005] In view of this, on the one hand, an embodiment of the present invention proposes a method for reducing radio frequency interference, and on the other hand, a device, system and computer-readable storage medium for reducing radio frequency interference are proposed to reduce the interference falling within the system application bandwidth.

[0006] A method for reducing radio frequency interference proposed in an embodiment of the present invention includes: for an interference signal with a known and stable interference frequency falling within the system application bandwidth, if the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, acquiring a set number of sampling point data of the interference signal within one synchronous period of the acquisition; obtaining reference interference data within one synchronous period based on the set number of sampling point data; within each synchronous period, acquiring the system signal with the interference signal to obtain system sampling data; and using the system sampling data to subtract the reference interference data correspondingly to obtain system data with reduced interference.

[0007] In one embodiment, the set quantity = (system sampling rate / interference frequency) * (interference frequency / synchronous clock) * m; where, sampling rate / interference frequency refers to: the number of samplings in one interference period at the system sampling rate; interference frequency / synchronous clock refers to: the number of complete interference periods in one synchronous clock; m is an integer greater than or equal to 1.

[0008] In one embodiment, obtaining the reference interference data within one synchronous period based on the sampling point data of the set quantity includes: directly using the sampling point data of the set quantity as the reference interference data within one synchronous period.

[0009] In one embodiment, obtaining the reference interference data within one synchronous period based on the sampling point data of the set quantity includes: calculating the phase and amplitude of the sampling point data of the set quantity; fitting an ideal sine wave signal with the same phase, amplitude and frequency according to the phase, amplitude and the interference frequency, and using the ideal sine wave signal as the reference interference data within one synchronous period.

[0010] In one embodiment, calculating the phase and amplitude of the sampling point data of the set quantity includes: calculating the real part Real and the imaginary part Imag of the sampling point data of the set quantity according to the following formula;

[0011]

[0012]

[0013] where, K is the number of interference signal sampling periods, N is the total number of samplings, n is an integer between 1 and N, and Xn is the value of the sampling point data;

[0014] After obtaining the real part Real and the imaginary part Imag, calculate the phase θ and amplitude A of the sampling point data of the set quantity according to the following formula;

[0015]

[0016]

[0017] In one embodiment, the cos() value used for calculating the real part and the sin() value used for calculating the imaginary part are obtained by looking up a pre-stored first table with the value of 2 * π * K * n / N as the index.

[0018] In one embodiment, the phase θ is obtained by the following method: obtaining an initial angle within 90 degrees by looking up a pre-stored second table with the value of as the index According to the sign relationship between the real part Real and the imaginary part Imag, convert the initial angle to the corresponding angle θ within 360 degrees.

[0019] In one embodiment, the system is a magnetic resonance imaging system.

[0020] The device for reducing radio frequency interference proposed in the embodiments of the present invention includes: an interference data determination module, configured to, for an interference signal with a known and stable frequency falling within the system application bandwidth, if the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, obtain the set number of sampling point data of the interference signal within one synchronous period of the acquisition; obtain the reference interference data within one synchronous period based on the set number of sampling point data; an interference reduction module, configured to, within each synchronous period, obtain the system signal with the interference signal collected to obtain system sampling data; and use the system sampling data to subtract the reference interference data correspondingly to obtain the system data with reduced interference.

[0021] In one embodiment, the set number = (system sampling rate / interference frequency) * (interference frequency / synchronous clock) * m; where, sampling rate / interference frequency refers to: the number of samplings in one interference period at the system sampling rate; interference frequency / synchronous clock refers to: the number of complete interference periods under one synchronous clock; m is an integer greater than or equal to 1.

[0022] In one embodiment, the interference data determination module directly uses the set number of sampling point data as the reference interference data within one synchronous period.

[0023] In one embodiment, the interference data determination module obtains the reference interference data within one synchronous period based on the set number of sampling point data according to the following process: calculate the phase and amplitude of the set number of sampling point data; fit an ideal sine wave signal with the same phase, amplitude and frequency according to the phase, amplitude and the interference frequency, and use the ideal sine wave signal as the reference interference data within one synchronous period.

[0024] In one embodiment, the interference data determination module calculates the phase and amplitude of the set number of sampling point data according to the following process:

[0025] Calculate the real part Real and the imaginary part Imag of the set number of sampling point data according to the following formula;

[0026]

[0027]

[0028] Wherein, K is the number of sampling periods of the interference signal, N is the total number of samplings, n is an integer between 1 and N, and Xn is the value of the sampling point data;

[0029] After obtaining the real part Real and the imaginary part Imag, the phase of the set number of sampling point data is calculated according to the following formula and the amplitude A;

[0030]

[0031]

[0032] In one embodiment, the cos() value used to calculate the real part and the sin() value used to calculate the imaginary part are obtained by looking up a pre-stored first table with the value of 2*π*K*n / N as the index.

[0033] In one embodiment, the interference data determination module obtains the phase θ according to the following process: by using the value of as the index to look up a pre-stored second table to obtain an initial angle within 90 degrees According to the positive and negative sign relationship between the real part Real and the imaginary part Imag, the initial angle is converted into the corresponding angle θ within 360 degrees.

[0034] In one embodiment, the system is a magnetic resonance imaging system.

[0035] The device for reducing radio frequency interference proposed in the embodiments of the present invention includes: at least one memory and at least one processor, wherein: the at least one memory is used to store a computer program; the at least one processor is used to call the computer program stored in the at least one memory and execute the method for reducing radio frequency interference described in any of the above embodiments.

[0036] A magnetic resonance imaging system proposed in the embodiments of the present invention includes the device for reducing radio frequency interference described in any of the above embodiments.

[0037] The computer-readable storage medium proposed in the embodiments of the present invention stores a computer program thereon; the computer program can be executed by a processor and implement the method for reducing radio frequency interference described in any of the above embodiments.

[0038] As can be seen from the above solution, in the embodiments of the present invention, based on the digital cancellation technology, for interference signals with known and stable frequencies falling within the system application bandwidth, when the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, a set number of sampling point data of the interference signal within one synchronous period is obtained, and the reference interference data within one synchronous period is obtained based on the set number of sampling point data; then within each synchronous period, in the digital domain, the system sampling data with the interference signal collected is correspondingly subtracted from the reference interference data, thereby reducing the interference in the system data.

[0039] Among them, by directly using the set number of sampling point data as the reference interference data within one synchronous period, system resources can be saved. Although other interferences will be introduced outside the system application bandwidth, it has no impact on applications that do not pay attention to the non-system application bandwidth. For applications that need to pay attention to the non-system application bandwidth, subsequent filtering can be performed using traditional bandwidth filtering. For the application of fitting the corresponding ideal sine wave signal based on the set number of sampling point data, although it consumes more system resources, it will not introduce additional interference and has a better cancellation effect.

[0040] In addition, during the process of fitting the corresponding ideal sine wave signal based on the set number of sampling point data, by pre-storing the corresponding look-up table, the computing resources of the system can be further saved and the computing efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The following will make the above and other features and advantages of the present invention clearer to those of ordinary skill in the art by describing the preferred embodiments of the present invention in detail with reference to the accompanying drawings, in which:

[0042] Figure 1 It is a schematic diagram of the interference transmission path between a current clock structure and a radio frequency link.

[0043] Figure 2 It is an exemplary flowchart of the method for reducing radio frequency interference in the embodiments of the present invention.

[0044] Figure 3 It is a time-domain waveform diagram of the 12.5 MHz interference signal Is in a magnetic resonance imaging system in an example of the present invention.

[0045] Figure 4 It is an exemplary structural diagram of the device for reducing radio frequency interference in the embodiments of the present invention.

[0046] Figure 5 It is a schematic flowchart of the method for reducing radio frequency interference in a magnetic resonance imaging system in an example of the present invention.

[0047] Figure 6Schematic structural diagram of a device for reducing radio frequency interference in a magnetic resonance imaging system in an example of the present invention.

[0048] Figure 7 Schematic diagram for comparing frequency domain effects after radio frequency interference reduction processing in an example of the present invention.

[0049] Figure 8 Comparison graph between the fast Fourier transform (FFT) of reference interference data and the FFT of an ideal sine wave in an example of the present invention.

[0050] Figure 9 Schematic flowchart of a method for reducing radio frequency interference in a magnetic resonance imaging system in another example of the present invention.

[0051] Figure 10 is Figure 9 Schematic flowchart of an implementation method for step S502 in

[0052] Figure 11 Schematic structural diagram of a device for reducing radio frequency interference in a magnetic resonance imaging system in another example of the present invention.

[0053] Figure 12 Schematic diagram for comparing frequency domain effects after radio frequency interference reduction processing in another example of the present invention.

[0054] Figure 13 Schematic structural diagram of yet another device for reducing radio frequency interference in an embodiment of the present invention.

[0055] Among them, the reference numerals are as follows:

[0056]

[0057] Detailed implementation manner

[0058] In an embodiment of the present invention, considering that in magnetic resonance imaging, for a 2.5 MHz synchronous clock, there are still some signals of n×2.5 MHz falling into the system application bandwidth. For example, Figure 1 is a schematic diagram of an interference transmission path between a current clock structure 2 and a radio frequency link 1. As Figure 1As shown in the figure, in lithium proton imaging under a 1.5T system, there is an interference signal of 12.5 MHz. The analog-to-digital conversion module (ADC) 12 samples the magnetic resonance signal processed by the analog processing module 11 and the 12.5 MHz interference signal together, and then transmits them to the field programmable gate array (FPGA) 13 for signal processing. Among them, the center frequency of the sampled signal is 12.22 MHz, the system application bandwidth is 12.22 MHz ± 500 KHz, the input frequency determined by the clock distribution module 21, that is, the sampling rate of the ADC 12, is 80 MHz, and all clocks, including the sampling clock of the ADC 12, are synchronized to the reference synchronization frequency of 2.5 MHz. The sampling rate of the ADC 12 and the interference frequency are both common multiples of 2.5 MHz, that is, the synchronization clock frequency is the greatest common divisor of the sampling rate of the ADC 12 and the interference frequency. 12.5 MHz is the fifth harmonic generated by the synchronization clock source 22 based on 2.5 MHz. It can be seen that the 12.5 MHz interference falls within the system application bandwidth of the MRI. In addition, in other systems, the numerically controlled oscillator (NCO) in the FPGA may also bring interference signals of n×2.5 MHz to the corresponding system signals. For such interference, it is very difficult to eliminate it through hardware measures, and the aforementioned known methods are all ineffective. However, considering that such interference is an interference with a known and stable frequency, and the frequency of the interference signal and the system sampling rate have the synchronization clock frequency as the greatest common divisor, and in the case of ignoring noise, the values of the corresponding sampling points in each synchronization period should remain unchanged. Therefore, it can be considered to reduce or even eliminate the interference signal in the digital domain.

[0059] To make the objectives, technical solutions, and advantages of the present invention clearer, the following embodiments are given to further elaborate on the present invention in detail.

[0060] Figure 2 It is an exemplary flowchart of the method for reducing radio frequency interference in the embodiments of the present invention. As Figure 2 shown, the method may include the following steps:

[0061] Step S210, for a known and stable interference signal with a frequency falling within the system application bandwidth, if the interference frequency of the interference signal and the system sampling rate have the synchronization clock frequency as the greatest common divisor, obtain the set number of sampling point data of the interference signal within one synchronization period of the acquisition; obtain the reference interference data within one synchronization period based on the set number of sampling point data.

[0062] In this step, the set number of sampling point data can be evenly distributed in the time domain, that is, collected at the same time interval. In one example, the set number = (system sampling rate / interference frequency) * (interference frequency / synchronization clock) * m; where, sampling rate / interference frequency refers to: the number of samplings in one interference period at the system sampling rate; interference frequency / synchronization clock refers to: the number of complete interference periods in one synchronization clock; m is an integer greater than or equal to 1.

[0063] Figure 3 Fig. shows the time-domain waveform diagram of the 12.5 MHz interference signal Is in a magnetic resonance imaging system in one example. In this example, the set number = (80 / 12.5) * (12.5 / 2.5) * 1 = 32, that is, 32 sampling point data of the interference signal are collected within one 2.5 MHz synchronization period (one synchronization period between two Ss) of the synchronization signal Ss. As shown in the positions of D1 to D32 in the figure, D33, D34, and D35 are the sampling point positions corresponding to D1, D2, and D3 respectively in the next synchronization period.

[0064] In practical applications, the system can collect the set number of sampling point data of the interference signal in each synchronization period within the first time period before loading the system signal. Then, in this step, the set number of sampling point data of the interference signal within one synchronization period can be intercepted, for example, the data within a few seconds after the system starts. Specifically, in Figure 1 the shown interference transmission path, data can be collected by ADC 12, and then the set number of sampling point data of the interference signal within one synchronization period can be intercepted by FPGA13. In addition, in other embodiments, this step is not limited to being implemented by FPGA13, and can also be implemented by a computer, etc.

[0065] In addition, in one embodiment, the set number of sampling point data of the interference signal within one synchronization period can be directly used as the reference interference data within one synchronization period.

[0066] In order to reduce the deviation caused by the sampling process and introduce unnecessary interference, in another embodiment, the phase and amplitude of the set number of sampling point data can be calculated based on the set number of sampling point data; then, an ideal sine wave signal with the same phase, amplitude, and frequency can be fitted according to the phase, amplitude, and the interference frequency. After that, the ideal sine wave signal is used as the reference interference data within one synchronization period. For example, this embodiment may include:

[0067] 1) Calculate the real part Real and the imaginary part Imag of the set number of sampling point data according to the following formulas (1) and (2);

[0068]

[0069]

[0070] Wherein, K is the number of sampling periods of the interference signal, N is the total number of samplings, n is an integer between 1 and N, and Xn is the value of the sampling point data.

[0071] In specific implementation, in order to reduce the system calculation amount, a correspondence table between the angle value α and the values of sin(α) and cos(α) can be set in advance, which is called the first table. Then, the value of α of 2*π*K*n / N is calculated, and α is used as an index to query the first table to directly obtain the values of sin(α) and cos(α). The values of Xn*cos(α) and -Xn*sin(α) corresponding to the current sampling point data Xn are calculated, and then the values of the real part Real and the imaginary part Imag can be calculated.

[0072] 2) After obtaining the values of the real part Real and the imaginary part Imag, the phase θ and the amplitude A of the set number of sampling point data can be calculated according to the following formulas (3) and (4);

[0073]

[0074]

[0075] In specific implementation, for the phase θ, in order to reduce the system calculation amount, different values and the initial angle can be pre-stored in a correspondence table, which is called the second table. Then, the value of is calculated to find the initial angle by looking up the second table with as the index. Since is an angle value within 90 degrees, in order to obtain the θ value, it is also necessary to convert the initial angle

[0076] 3) Fit an ideal sine wave signal with the same phase, amplitude and frequency according to the phase, amplitude and the interference frequency. For example, a unit sine wave signal with the same frequency as the interference signal can be constructed first; then, the unit sine wave signal is adjusted according to the phase and amplitude of the set number of sampling point data to obtain an ideal sine wave signal with the same frequency, phase and amplitude as the interference signal. Then, the ideal sine wave signal is used as the reference interference data within a synchronization period.

[0077] Subsequently, taking a magnetic resonance imaging system as an example, the above two implementation manners will be described in detail respectively.

[0078] Step S220: In each synchronization period, obtain the system signal with the interference signal collected to obtain system sampling data; use the system sampling data to subtract the reference interference data correspondingly to obtain interference-free system data.

[0079] In this step, the system can collect the system signal with the interference signal after loading the system signal to obtain corresponding system sampling data. For the system sampling data in each synchronization period, use the system sampling data to subtract the reference interference data correspondingly to obtain interference-free system data. Specifically, in the Figure 1 shown interference transmission path, data can be collected by ADC 12, and then the subtraction operation of the system sampling data and the reference interference data can be performed by FPGA13. In addition, in other implementation manners, this step is not limited to be implemented by FPGA13. For example, it can also be implemented by a computer or the like.

[0080] Figure 4 This is an exemplary structural diagram of the device for reducing radio frequency interference in the embodiments of the present invention. Figure 4 The shown device embodiment can implement Figure 2 the shown method embodiment. For the details not disclosed in detail in the Figure 4 shown device embodiment, reference can be made to the corresponding description in the Figure 2 shown method embodiment. As Figure 4 shown, the device includes: an interference data determination module 410 and an interference reduction module 420.

[0081] Among them, the interference data determination module 410 is used for the interference signal with a known and stable frequency falling within the system application bandwidth. If the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronization clock frequency, obtain the set number of sampling point data of the interference signal within one synchronization period collected; obtain the reference interference data within one synchronization period based on the set number of sampling point data.

[0082] The set number of sampling point data can be evenly distributed in the time domain, that is, collected at the same time interval. In an example, the set number = (system sampling rate / interference frequency) * (interference frequency / synchronization clock) * m; where, sampling rate / interference frequency refers to: the number of samplings in one interference period at the system sampling rate; interference frequency / synchronization clock refers to: the number of complete interference periods in one synchronization clock; m is an integer greater than or equal to 1.

[0083] The interference reduction module 420 is used to obtain the system signal with the interference signal collected in each synchronization period to obtain system sampling data; and use the system sampling data to subtract the reference interference data correspondingly to obtain interference-free system data.

[0084] In one example, the interference data determination module 410 can directly use the set number of sampling point data as the reference interference data in one synchronization period.

[0085] In another example, the interference data determination module 410 can obtain the reference interference data in one synchronization period based on the set number of sampling point data according to the following process: calculate the phase and amplitude of the set number of sampling point data; fit an ideal sine wave signal with consistent phase, amplitude and frequency according to the phase, amplitude and the interference frequency, and use the ideal sine wave signal as the reference interference data in one synchronization period. Specifically, in one example, the interference data determination module 410 can calculate the phase and amplitude of the set number of sampling point data according to the process described in step S22.

[0086] Taking the system as a magnetic resonance imaging system as an example below, the above solution will be illustrated by examples.

[0087] Figure 5 It is a schematic flow chart of a method for reducing radio frequency interference in a magnetic resonance imaging system in an example of the present invention. As Figure 5 shown, the method includes the following steps:

[0088] Step S501, before loading the magnetic resonance signal MRs, collect the interference signal Is after band-pass filtering to obtain the set number of sampling point data of the interference signal Is in each synchronization period.

[0089] Step S210, intercept the set number of sampling point data of the interference signal Is in one synchronization period, and use the set number of sampling point data of the interference signal Is in the one synchronization period as the reference interference data in one synchronization period.

[0090] Step S502, load the magnetic resonance signal MRs, and collect the magnetic resonance signal with the interference signal Is after band-pass filtering to obtain the magnetic resonance system sampling data with the interference signal Is in each synchronization period.

[0091] Step S220, in each synchronization period, use the magnetic resonance system sampling data to subtract the reference interference data to obtain the magnetic resonance system data with reduced interference.

[0092] Figure 6 It is a schematic structural diagram of a device for reducing radio frequency interference in a magnetic resonance imaging system in an example of the present invention.Figure 6 The illustrated device embodiment can achieve Figure 5 the illustrated method embodiment. As Figure 6 shown, the device may include: switch K1, band-pass filtering module 601, acquisition module 602, interference data determination module 410, and interference reduction module 420.

[0093] The band-pass filtering module 601 is configured to perform band-pass filtering on the interference signal Is before the switch K1 is closed and the magnetic resonance signal MRs is loaded; and perform band-pass filtering on the magnetic resonance signal with the interference signal Is after the switch K1 is closed and the magnetic resonance signal MRs is loaded.

[0094] The acquisition module 602 is configured to acquire the interference signal Is after band-pass filtering, obtain the set number of sampling point data of the interference signal Is in each synchronization period and output it to the interference data determination module 410; and acquire the magnetic resonance signal with the interference signal Is after band-pass filtering, obtain the magnetic resonance system sampling data with the interference signal Is in each synchronization period and output it to the interference reduction module 420.

[0095] The interference data determination module 410 is configured to intercept the set number of sampling point data of the interference signal Is in one synchronization period from the set number of sampling point data of the interference signal Is in each synchronization period acquired by the acquisition module 602, and use the set number of sampling point data of the interference signal Is in the one synchronization period as the reference interference data in one synchronization period and output it to the interference reduction module 420.

[0096] The interference reduction module 420 is configured to, in each synchronization period, subtract the reference interference data from the interference data determination module 410 from the magnetic resonance system sampling data from the acquisition module 602 to obtain the magnetic resonance system data MRr with reduced interference.

[0097] Figure 7 shows a schematic diagram of the comparison of the frequency domain effects after reducing the radio frequency interference in the above example. Among them, Figure 7 the upper part in is the magnetic resonance signal before reducing the radio frequency interference. It can be seen that within the system application bandwidth, in addition to a magnetic resonance signal with an X-axis of 12.22 MHz and a Y-axis of 117.5 dB, there is also an interference signal with an X-axis of 12.5 MHz and a Y-axis of 110.4 dB. Figure 7 the lower part in is the magnetic resonance signal after reducing the radio frequency interference. It can be seen that the original interference signal with an X-axis of 12.5 MHz and a Y-axis of 110.4 dB becomes an interference signal with an X-axis of 12.5 MHz and a Y-axis of 51.34 dB, and the interference signal is reduced.

[0098] In addition, from Figure 7As can be seen from the figure in the lower middle, some 2.5 MHz harmonic interference signals will be introduced outside the system application bandwidth in this method. However, since these interference signals outside the system application bandwidth can be filtered out by a traditional band-pass filter, if it is necessary to eliminate these additional interferences, a digital band-pass filtering can be performed again after obtaining the magnetic resonance system data with reduced interference.

[0099] The reason for introducing the 2.5 MHz harmonic interference in the above method is that the period of the reference interference data is 2.5 MHz, and as Figure 8 shown in the comparison diagram of the fast Fourier transform (FFT) 81 of the reference interference data and the FFT 82 of the ideal sine wave, compared with the ideal sine wave, the reference interference data has a higher noise floor. Therefore, in the following example, it is considered to fit the corresponding ideal sine wave signal according to the set number of sampling point data in the above example as the reference interference data.

[0100] Figure 9 It is a schematic flowchart of a method for reducing radio frequency interference in a magnetic resonance imaging system in another example of the present invention. As Figure 9 shown, the method includes the following steps:

[0101] Step S501, before loading the magnetic resonance signal MRs, collect the interference signal Is after band-pass filtering to obtain the set number of sampling point data of the interference signal Is in each synchronization period.

[0102] Step S211, calculate the phase and amplitude of the set number of sampling point data according to the set number of sampling point data of the interference signal Is in one of the synchronization periods.

[0103] Step S212, construct a unit sine wave signal with the same frequency as the interference signal.

[0104] Step S213, adjust the unit sine wave signal according to the phase and amplitude of the set number of sampling point data to obtain an ideal sine wave signal with the same frequency, phase and amplitude as the interference signal, and use the ideal sine wave signal as the reference interference data in one synchronization period.

[0105] Step S502, load the magnetic resonance signal MRs, collect the magnetic resonance signal with the interference signal Is after band-pass filtering to obtain the magnetic resonance system sampling data with the interference signal Is in each synchronization period.

[0106] Step S220, in each synchronization period, subtract the reference interference data from the magnetic resonance system sampling data to obtain the magnetic resonance system data with reduced interference.

[0107] In one embodiment, a specific implementation method of the above step S211 may be as follows Figure 10 and includes the following steps:

[0108] Step S1001: Perform digital band-pass filtering on the set number of sampled point data Xn of the interference signal Is within one synchronization period.

[0109] Step S1002: For each sampled point data Xn, obtain its corresponding sin() value and cos() value by looking up a pre-stored first table, and calculate the real part Real and the imaginary part Imag of the set number of sampled point data by using the foregoing formulas (1) and (2).

[0110] Step S1003: Calculate the amplitude of the set number of sampled point data by using the foregoing formula (4) according to the real part Real and the imaginary part Imag calculated in step S1002.

[0111] Step S1004: Calculate the ratio of the imaginary part Imag to the real part Real according to the real part Real and the imaginary part Imag calculated in step S1002, and look up a pre-stored second table according to the ratio to obtain the initial angle value corresponding to its arctan() value and determine whether the ratio is greater than or equal to 0 or less than 0? If the ratio is greater than or equal to 0, then execute step S1005; if the ratio is less than 0, then execute step S1006.

[0112] Step S1005: Determine the signs of the imaginary part Imag and the real part Real. If the imaginary part Imag is greater than or equal to 0 and the real part Real is greater than 0, then the phase of the set number of sampled point data If the imaginary part Imag is less than 0 and the real part Real is less than 0, then the phase of the set number of sampled point data

[0113] Step S1006: Determine the signs of the imaginary part Imag and the real part Real. If the imaginary part Imag is greater than or equal to 0 and the real part Real is less than 0, then the phase of the set number of sampled point data If the imaginary part Imag is less than 0 and the real part Real is greater than 0, then the phase of the set number of sampled point data

[0114] Figure 11 is a schematic structural diagram of a device for reducing radio frequency interference in another example of the present invention. Figure 11 The device embodiment shown can implement Figure 9 the method embodiment shown. AsFigure 11 As shown, the device may include: switch K1, band-pass filtering module 601, acquisition module 602, phase and amplitude calculation module 411, unit signal construction module 412, ideal sine wave fitting module 413, and interference reduction module 420. Among them, the phase and amplitude calculation module 411, unit signal construction module 412, and ideal sine wave fitting module 413 together constitute the interference data determination module 410.

[0115] The band-pass filtering module 601 is used to perform band-pass filtering on the interference signal Is before the switch K1 is closed and the magnetic resonance signal MRs is loaded; and perform band-pass filtering on the magnetic resonance signal with the interference signal Is after the switch K1 is closed and the magnetic resonance signal MRs is loaded.

[0116] The acquisition module 602 is used to acquire the interference signal Is after band-pass filtering, obtain the set number of sampling point data of the interference signal Is in each synchronization period and output it to the phase and amplitude calculation module 411; and acquire the magnetic resonance signal with the interference signal Is after band-pass filtering, obtain the magnetic resonance system sampling data with the interference signal Is in each synchronization period and output it to the interference reduction module 420.

[0117] The phase and amplitude calculation module 411 is used to calculate the phase and amplitude of the set number of sampling point data according to the set number of sampling point data of the interference signal Is in one synchronization period. Specifically, when implemented, the phase and amplitude calculation module 411 can calculate the phase and amplitude of the set number of sampling point data according to the process as Figure 10 shown.

[0118] The unit signal construction module 412 is used to construct a unit sine wave signal with the same frequency as the interference signal.

[0119] The ideal sine wave fitting module 413 is used to adjust the unit sine wave signal according to the phase and amplitude calculated by the phase and amplitude calculation module 411, obtain an ideal sine wave signal with the same frequency, phase, and amplitude as the interference signal, and use the ideal sine wave signal as the reference interference data in one synchronization period.

[0120] The interference reduction module 420 is used to subtract the reference interference data from the ideal sine wave fitting module 413 from the magnetic resonance system sampling data from the sampling module 602 in each synchronization period to obtain the magnetic resonance system data MRr with reduced interference.

[0121] Figure 12 The figure shows a schematic diagram of the comparison of the frequency domain effects after reducing radio frequency interference in the above another example. Among them, Figure 7In the upper middle part is the magnetic resonance signal before reducing radio frequency interference. It can be seen that within the system application bandwidth, in addition to a magnetic resonance signal with an X-axis of 12.22 MHz and a Y-axis of 117.5 dB, there is also an interference signal with an X-axis of 12.5 MHz and a Y-axis of 110.4 dB. Figure 7 In the lower middle part is the magnetic resonance signal after reducing radio frequency interference. It can be seen that the original interference signal with an X-axis of 12.5 MHz and a Y-axis of 110.4 dB becomes an interference signal with an X-axis of 12.5 MHz and a Y-axis of 51.34 dB, and the interference signal is reduced.

[0122] In addition, from Figure 12 the figure in the lower middle part, it can be seen that no other additional interference signals are introduced in this method, indicating that the cancellation effect is relatively good.

[0123] Figure 13 This is a schematic structural diagram of another device for reducing radio frequency interference in an embodiment of the present invention. As Figure 13 shown, the system may include: at least one memory 1301 and at least one processor 1302. In addition, some other components may also be included, such as communication ports, etc. These components communicate through a bus 1303.

[0124] Among them, at least one memory 1301 is used to store computer programs. In one implementation, the computer program can be understood to include Figure 4 , Figure 8 or Figure 11 each module of the device for reducing radio frequency interference shown. In addition, at least one memory 1301 may also store an operating system, etc. The operating system includes but is not limited to: Android operating system, Symbian operating system, Windows operating system, Linux operating system, etc.

[0125] At least one processor 1302 is used to call the computer program stored in at least one memory 1301 and execute the method for reducing radio frequency interference described in the embodiment of the present invention. The processor 1302 can be a CPU, a processing unit / module, an ASIC, a logic module, or a programmable gate array, etc. It can receive and send data through the communication port.

[0126] An embodiment of the present invention also provides a magnetic resonance imaging system, which includes the device for reducing radio frequency interference in any of the above embodiments.

[0127] It should be noted that not all steps and modules in the above-mentioned processes and structure diagrams are necessary, and some steps or modules can be ignored according to actual needs. The execution order of each step is not fixed and can be adjusted according to needs. The division of each module is only for the convenience of description in terms of functions. In actual implementation, a module can be implemented by multiple modules, and the functions of multiple modules can also be implemented by the same module. These modules can be located in the same device or in different devices.

[0128] It can be understood that the hardware modules in the above-mentioned embodiments can be implemented in a mechanical or electronic manner. For example, a hardware module can include a specially designed permanent circuit or logic device (such as a dedicated processor, such as an FPGA or ASIC) for performing specific operations. A hardware module can also include a programmable logic device or circuit temporarily configured by software (such as including a general-purpose processor or other programmable processors) for performing specific operations. As for whether to specifically adopt a mechanical manner, a dedicated permanent circuit, or a temporarily configured circuit (such as configured by software) to implement the hardware module, it can be determined according to cost and time considerations.

[0129] In addition, an embodiment of the present invention also provides a computer-readable storage medium, on which a computer program is stored, and the computer program can be executed by a processor and implement the method for reducing radio frequency interference in the embodiments of the present invention. Specifically, a system or device equipped with a storage medium can be provided, and software program codes for implementing the functions of any one of the above embodiments are stored on the storage medium, and the computer (or CPU or MPU) of the system or device is made to read and execute the program codes stored in the storage medium. In addition, part or all of the actual operations can also be completed by an operating system operating on the computer based on instructions of the program code. The program code read from the storage medium can also be written to the memory provided in an expansion board inserted into the computer or to the memory provided in an expansion unit connected to the computer, and then based on the instructions of the program code, the CPU etc. installed on the expansion board or expansion unit are made to execute part and all of the actual operations, so as to implement the functions of any one of the above embodiments. Embodiment modes of the storage medium for providing program codes include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Optionally, the program code can be downloaded from a server computer through a communication network.

[0130] As can be seen from the above solution, in the embodiments of the present invention, based on the digital cancellation technology, for interference signals with known and stable frequencies falling within the system application bandwidth, when the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, a set number of sampling point data of the interference signal within a synchronous period is obtained, and reference interference data within a synchronous period is obtained based on the set number of sampling point data; then within each synchronous period, in the digital domain, the system sampling data with the interference signal collected is correspondingly subtracted from the reference interference data, thereby reducing the interference in the system data.

[0131] Among them, by directly using the set number of sampling point data as the reference interference data within a synchronous period, system resources can be saved. Although other interferences will be introduced outside the system application bandwidth, it has no impact on applications that do not care about the non-system application bandwidth. For applications that need to care about the non-system application bandwidth, subsequent filtering can be performed using traditional bandwidth filtering. For the application of fitting the corresponding ideal sine wave signal based on the set number of sampling point data, although it consumes more system resources, it will not introduce additional interference and has a better cancellation effect.

[0132] In addition, during the process of fitting the corresponding ideal sine wave signal based on the set number of sampling point data, by pre-storing the corresponding look-up table, the computing resources of the system can be further saved and the computing efficiency can be improved.

[0133] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing radio frequency interference, characterized in that, Including: For an interference signal with a known and stable frequency falling within the system application bandwidth, if the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, obtain the set number of sampling point data of the interference signal within one synchronous period of the acquisition; obtain the reference interference data within one synchronous period based on the set number of sampling point data (S210); Within each synchronous period, obtain the system signal with the interference signal acquired, and obtain the system sampling data; use the system sampling data to subtract the reference interference data correspondingly to obtain the system data with reduced interference (S220).

2. The method for reducing radio frequency interference according to claim 1, wherein The set number = (system sampling rate / interference frequency) * (interference frequency / synchronous clock) * m; where Sampling rate / interference frequency means: the number of samplings in one interference period at the system sampling rate; Interference frequency / synchronous clock means: the number of complete interference periods under one synchronous clock; m is an integer greater than or equal to 1.

3. The method for reducing radio frequency interference according to claim 1, wherein The obtaining the reference interference data within one synchronous period based on the set number of sampling point data includes: directly using the set number of sampling point data as the reference interference data within one synchronous period.

4. The method for reducing radio frequency interference according to claim 1, characterized in that The obtaining the reference interference data within one synchronous period based on the set number of sampling point data includes: Calculating the phase and amplitude of the set number of sampling point data; Fitting an ideal sine wave signal with the same phase, amplitude and frequency according to the phase, amplitude and the interference frequency, and using the ideal sine wave signal as the reference interference data within one synchronous period.

5. The method for reducing radio frequency interference according to claim 4, wherein The calculating the phase and amplitude of the set number of sampling point data includes: Calculating the real part Real and the imaginary part Imag of the set number of sampling point data according to the following formula; where K is the number of interference signal sampling periods, N is the total number of samplings, n is an integer between 1 and N, and Xn is the value of the sampling point data; After obtaining the real part Real and the imaginary part Imag, calculating the phase θ and amplitude A of the set number of sampling point data according to the following formula; 6. The method for reducing radio frequency interference according to claim 5, characterized in that, The cos() value used for calculating the real part and the sin() value used for calculating the imaginary part are obtained by looking up a pre-stored first table with the value of 2 * π * K * n / N as the index.

7. The method for reducing radio frequency interference according to claim 5, wherein The phase θ is obtained by the following method: By using the value of as an index to look up a pre-stored second table, an initial angle within 90 degrees is obtained According to the sign relationship between the real part Real and the imaginary part Imag, convert the initial angle to the corresponding angle θ within 360 degrees.

8. The method for reducing radio frequency interference according to any one of claims 1 to 7, characterized in that, The system is a magnetic resonance imaging system.

9. Device for reducing radio frequency interference, characterized in that, Including: An interference data determination module (410), configured to, for an interference signal with a known and stable frequency falling within the system application bandwidth, if the interference frequency of the interference signal and the system sampling rate have a common divisor with the synchronous clock frequency, obtain the set number of sampling point data of the interference signal within one synchronous period of the acquisition; obtain the reference interference data within one synchronous period based on the set number of sampling point data; An interference reduction module (420), configured to, within each synchronous period, obtain the system signal with the interference signal acquired, and obtain the system sampling data; use the system sampling data to subtract the reference interference data correspondingly to obtain the system data with reduced interference.

10. The device for reducing radio frequency interference according to claim 9, wherein the set number = (system sampling rate / interference frequency) * (interference frequency / synchronization clock) * m; where sampling rate / interference frequency means: the number of samples in one interference period at the system sampling rate; interference frequency / synchronization clock means: the number of complete interference periods in one synchronization clock; m is an integer greater than or equal to 1.

11. The device for reducing radio frequency interference according to claim 9, characterized in that, The interference data determination module (410) directly uses the sampled point data of the set number as the reference interference data within one synchronization period.

12. The device for reducing radio frequency interference according to claim 9, wherein The interference data determination module (410) obtains the reference interference data within one synchronization period based on the sampled point data of the set number according to the following process: Calculate the phase and amplitude of the sampled point data of the set number; Fit an ideal sine wave signal with the same phase, amplitude and frequency according to the phase, amplitude and the interference frequency, and use the ideal sine wave signal as the reference interference data within one synchronization period.

13. The device for reducing radio frequency interference according to claim 12, wherein The interference data determination module (410) calculates the phase and amplitude of the sampled point data of the set number according to the following process: Calculate the real part Real and the imaginary part Imag of the sampled point data of the set number according to the following formula: where K is the number of sampling periods of the interference signal, N is the total number of samples, n is an integer between 1 and N, and Xn is the value of the sampled point data; After obtaining the real part Real and the imaginary part Imag, calculate the phase of the data of the set number of sampling points according to the following formula and the amplitude A; 14. The device for reducing radio frequency interference according to claim 13, wherein The cos() value used to calculate the real part and the sin() value used to calculate the imaginary part are obtained by looking up a pre-stored first table with the value of 2 * π * K * n / N as the index.

15. The device for reducing radio frequency interference according to claim 13, wherein The interference data determination module (410) obtains the phase θ according to the following process: By using the value of as an index to look up a pre-stored second table to obtain an initial angle within 90 degrees According to the sign relationship between the real part Real and the imaginary part Imag, convert the initial angle to the corresponding angle θ within 360 degrees.

16. The device for reducing radio frequency interference according to any one of claims 9 to 15, characterized in that The system is a magnetic resonance imaging system.

17. Device for reducing radio frequency interference, characterized in that, Comprising: at least one memory (1301) and at least one processor (1302), wherein: the at least one memory (1301) is used for storing computer programs; the at least one processor (1302) is used for calling the computer programs stored in the at least one memory (1301) and executing the method for reducing radio frequency interference according to any one of claims 1 to 8.

18. A magnetic resonance imaging system, characterized in that, Comprising the device for reducing radio frequency interference according to any one of claims 9 to 16.

19. A computer-readable storage medium having a computer program stored thereon; characterized in that, The computer program can be executed by a processor and implement the method for reducing radio frequency interference according to any one of claims 1 to 8.

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