CN112948747B - Method, device, terminal equipment and storage medium for finding center frequency - Google Patents

Abstract

The embodiment of the invention discloses a method, a device, terminal equipment and a storage medium for searching center frequency, wherein the method for searching the center frequency comprises the following steps: constructing a standard function; obtaining an analog signal of a human body scanning part under a magnetic resonance field intensity system according to the standard function; collecting a group of collected signals of a human body scanning part under a magnetic resonance field intensity system; and comparing the analog signal with the acquired signal, wherein the corresponding frequency position is the central frequency when the acquired signal and the analog signal are maximally superposed. The method for searching the center frequency is only related to a standard function in the calculation process, whether the actually acquired signal is influenced by the environment or noise is not required to be considered, the center frequency can be determined according to the maximum similarity between the acquired signal and the analog signal, manual auxiliary positioning and confirmation are not required, and the accuracy and the stability are greatly improved.

Description

Method, device, terminal equipment and storage medium for finding center frequency

technical field

The invention relates to the field of magnetic resonance systems, in particular to a method, device, terminal equipment and storage medium for finding a center frequency.

Background technique

The magnetic resonance imaging system mainly collects the signals of H protons in the human body. When the magnetic resonance system scans the human body, there are many complex water and fat signals mixed in. The human body signals include fat signals, water signals, and silica gel fillings in the human body. The human body signal presents multiple signal peaks distributed in different frequency ranges, and the performance in different scanning parts cannot be completely consistent.

The existing method of finding the center frequency is to use the fixed frequency difference between water and fat to calculate the frequency difference between the water signal and the fat signal of the collected signal, or add manual judgment to determine the water frequency position to obtain the center frequency value of the water signal. The existing center frequency search method is relatively single, unable to cope with the search of the center frequency of magnetic resonance with various field strengths, and cannot improve the accuracy when dealing with complex frequency distribution or interference situations, such as the signal intensity of fat frequency under different scanning site conditions Sometimes it will greatly exceed the water frequency signal, and it is mixed with interference signals, so it is difficult to accurately find the frequency position of the water signal. The frequency position of the water signal cannot be accurately judged by the human eye and the traditional water fat fixed frequency calculation method. If the position of the center frequency corresponding to the water signal cannot be accurately found, the scanned image during magnetic resonance will not be clear.

Contents of the invention

In view of the above technical problems, the embodiment of the present invention provides a method, device, terminal equipment and storage medium for finding the center frequency, which is not affected by variable factors such as the scanning location, the field strength of the magnetic resonance system, and environmental noise, and is aimed at interference Signals such as those generated by silica gel fillers and multiple fat frequencies can still be analyzed and calculated to calculate the center frequency position of the optimal water signal, and the accurate center frequency can be automatically and quickly found to improve the image quality during magnetic resonance.

The first aspect of the embodiments of the present invention provides a method for finding the center frequency, the steps include:

Construct a standard function;

According to the standard function, the analog signal of the human body scanning part under the magnetic resonance field strength system is obtained;

Acquiring a group of acquisition signals of the scanning parts of the human body under the magnetic resonance field strength system;

The analog signal is compared with the acquisition signal, and the corresponding frequency position when the acquisition signal and the analog signal reach a maximum coincidence is the center frequency.

Preferably, when the standard function is a Gaussian function, a described standard function is obtained as follows:

stdSignal＝GenerateSimSig(N,Δf _wf ,w) formula (1)

Among them, in formula (1), N represents the number of signal points, Δf _wf represents the frequency difference between water and fat; w represents the proportion of fat peak and water peak.

Preferably, the analog signal of the human body scanning part under the magnetic resonance field strength system is obtained according to the standard function, specifically:

Select a specific field strength system and human body scanning part, and determine the corresponding signal points, water-fat frequency difference and the proportion of fat peak and water peak;

The analog signal is obtained by substituting the number of signal points, the frequency difference between water and fat, and the proportion of fat peak and water peak into the standard function.

Preferably, the analog signal is compared with the collected signal, and when the collected signal diagram and the analog signal diagram reach the maximum coincidence, the corresponding frequency position is the center frequency, specifically including:

Calculating a cross-correlation matrix [coef, pos] between the analog signal and the collected signal;

Find the pos value when the maximum value of coef is found;

Convert the pos value at the maximum value of coef to the center frequency f.

Preferably, the cross-correlation matrix [coef, pos] is:

[coef,pos]=cro_cor(stdSignal ₀ ,realSignal) formula (2)

Among them, in formula (2), stdSignal ₀ represents the analog signal, realSignal represents the collected signal, coef represents the correlation coefficient of the coincidence degree between the analog signal and the collected signal, and pos represents the relative distance that the analog signal moves relative to the collected signal.

The first aspect of the embodiments of the present invention provides a device for finding a center frequency, including:

A function construction module, used to construct a standard function;

The signal acquisition module is used to obtain the analog signal of the human body scanning part under the magnetic resonance field strength system according to the standard function;

A signal acquisition module, configured to acquire a group of acquisition signals of the human body scanning parts under the magnetic resonance field strength system;

The center frequency search module is used to compare the analog signal with the acquisition signal, and when the acquisition signal and the analog signal reach the maximum overlap, the corresponding frequency position is the center frequency.

Preferably, the signal acquisition module includes:

The system information acquisition unit is used to select a specific field strength system and human body scanning part, and determine the corresponding signal points, water-fat frequency difference and the proportion of fat peak and water peak;

The signal deriving unit is used for substituting the number of signal points, the frequency difference of water and fat, and the proportion of fat peak and water peak into the standard function to obtain an analog signal.

Preferably, the center frequency search module includes:

A correlation matrix calculation unit, configured to calculate a cross-correlation matrix [coef, pos] between the analog signal and the collected signal;

A value search unit, used to find the pos value when the coef is at its maximum value;

The frequency conversion unit is used to convert the pos value at the maximum value of coef to the center frequency f.

A third aspect of the embodiments of the present invention provides a terminal device, including: at least one processor and a memory; the memory stores a computer program; the at least one processor executes the computer program stored in the memory, so as to realize the above search center frequency method.

A fourth aspect of the embodiments of the present invention provides a computer-readable storage medium, which is characterized in that a computer program is stored in the computer-readable storage medium, and when the computer program is executed, the above-mentioned method for finding a center frequency is implemented.

The method for finding the center frequency in the technical solution provided by the embodiment of the present invention, compared with the prior art, the calculation process of the method for finding the center frequency is only related to the standard function, and it is not necessary to consider whether the actual collected signal is affected by the environment or noise , the center frequency can be determined according to the maximum similarity between the acquisition signal and the analog signal, and does not need to rely on manual auxiliary positioning and confirmation, which greatly improves the search accuracy and stability, thereby improving the image quality during magnetic resonance.

Description of drawings

FIG. 1 is a flowchart of a method for collecting product abnormalities in an embodiment of the present invention.

Fig. 2 is a display diagram of an analog signal according to an embodiment of the present invention.

FIG. 3 is a display diagram of collected signals according to an embodiment of the present invention.

Fig. 4 is a positional relationship diagram between the analog signal and the collected signal before searching in the present invention.

Fig. 5 is a positional relationship diagram between the analog signal and the collected signal after searching in the present invention.

FIG. 6 is a schematic structural diagram of a device for finding a center frequency in an embodiment of the present invention.

FIG. 7 is a schematic structural diagram of a terminal device in an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

The invention provides a method for finding the center frequency. The calculation process of the method for finding the center frequency is only related to the standard function, and it is not necessary to consider whether the actual collected signal is affected by the environment or noise. The center frequency is determined by the maximum similarity, and does not need to rely on manual auxiliary positioning and confirmation, which greatly improves the accuracy and stability.

Fig. 1 is the flowchart of the method for searching center frequency of the present invention, as shown in Figure 1, the method for searching center frequency of the present invention, step comprises:

S1. Construct a standard function;

S2. According to the standard function, the analog signal of the human body scanning part under the magnetic resonance field strength system is obtained;

S3. Collect a group of collected signals of human body scanning parts under the magnetic resonance field strength system;

S4. Comparing the analog signal with the collected signal, when the collected signal and the analog signal reach a maximum coincidence, the corresponding frequency position is the center frequency.

The steps of the method for finding the center frequency are described in detail below:

First of all, it is necessary to construct a standard function to compare with the actual collected signal. The standard function can adopt Gaussian function or trigonometric function, but it is not limited to this. within the scope of protection. Step S1 specifically includes:

The present invention is illustrated by taking the standard function as a Gaussian function as an example. When the standard function is a Gaussian function, according to the prior knowledge that the fat frequency is less than the water frequency, the standard function can be drawn as follows:

stdSignal＝GenerateSimSig(N,Δf _wf ,w) formula (1)

Among them, in formula (1), stdSignal is a one-dimensional Gaussian curve, N represents the number of signal points, Δf _wf represents the frequency difference between water and fat; w represents the proportion of fat peak and water peak.

After completing the construction of the standard function, it is necessary to obtain the analog signal of the human body scanning part under the magnetic resonance field strength system according to the standard function, and the step S2 is specifically:

S21. Select a specific field strength system and human body scanning part, and determine corresponding signal points, water-fat frequency difference, and proportion of fat peak and water peak.

Δf _wf and w in this standard function can be flexibly adjusted according to the specific field strength system of magnetic resonance and the different parts of the human body to be scanned. For example, to scan the abdomen under the 3.0T system, then at this time, Δf _wf =450HZ, w= 1.5, and select N=2048, and ensure that the number of signal points is consistent with the collected signal during the selection process of N.

S22. Substituting the number of signal points, the frequency difference between water and fat, and the proportion of fat peak and water peak into the standard function to obtain an analog signal. At this time, the analog signal obtained according to the standard function:

stdSignal ₀ = GenerateSimSig(2048,450,1.5)

The display diagram of the analog signal is shown in FIG. 2 . As shown in FIG. 2 , the abscissa represents the data point, and the ordinate represents the frequency value. For convenience, the frequency value is normalized. The higher peak on the left is the fat signal, and the lower peak on the right is the water signal.

Further, before comparing the analog signal with the collected signal, it is necessary to collect a group of collected signals of the human body scanning part under the above-mentioned specific field strength system, and step S3 specifically includes:

What the present invention collects is the acquisition signal when scanning the abdomen of the human body under the 3.0T system. The display diagram of the analog signal is shown in Figure 3, wherein the abscissa represents the data point, and the ordinate represents the frequency value. For convenience, the frequency value is normalized treatment.

Further, the analog signal is compared with the acquisition signal, and the corresponding frequency position when the acquisition signal and the analog signal reach a maximum coincidence is the center frequency. In order to accurately distinguish the water signal and the fat signal of the collected signal, so as to accurately find out the center frequency, the present invention takes the collected signal as the goal, and by moving the analog signal, when the collected signal and the analog signal reach the maximum coincidence, the analog signal and the collected signal The correlation is highest for , while the relative distance that the analog signal moves relative to the acquired signal can be used to deduce the center frequency. Step S4 is specifically:

Step S41 , calculating a cross-correlation matrix [coef, pos] between the analog signal and the collected signal.

Among them, the cross-correlation matrix [coef, pos] is:

[coef,pos]=cro_cor(stdSignal ₀ ,realSignal) formula (2)

Among them, in the formula (2), stdSignal ₀ represents the analog signal; realSignal represents the acquisition signal; coef is a one-dimensional array, indicating the correlation coefficient of the coincidence degree between the analog signal and the acquisition signal; pos is a one-dimensional array, indicating that the analog signal is relative to the acquisition signal The relative distance the signal moves.

Step S42, looking for the pos value when the coef maximum value;

The maximum value in the array coef indicates that the correlation between the two signals is the largest, that is, the analog signal and the collected signal have the largest coincidence degree and the largest similarity. Fig. 4 is the position relationship diagram of analog signal and acquisition signal before the present invention searches, and Fig. 5 is the position relation diagram of analog signal and acquisition signal after the present invention searches, the analog signal in Fig. 4 is moved to the left the distance of a pos value, When moving the distance of the pos value at the maximum value of coef, the analog signal and the collected signal achieve the maximum degree of overlap, as shown in Figure 5.

Step S43, converting the pos value at the time of the maximum value of coef to the center frequency f.

Convert the pos value to the center frequency according to the following formula:

Among them, in the formula (3), f is the center frequency, T is the sampling time interval of the acquisition signal, and N ₀ is the number of sampling points of the acquisition signal.

Based on the above method for finding the center frequency, the present invention also provides a device for finding the center frequency, please refer to Figure 6, the device 100 for finding the center frequency of the present invention includes:

A function construction module 110, configured to construct a standard function;

The signal acquisition module 120 is used to obtain the analog signal of the human body scanning part under the magnetic resonance field strength system according to the standard function;

A signal acquisition module 130, configured to acquire a group of acquisition signals of the body scanning parts under the magnetic resonance field strength system;

The center frequency search module 140 is configured to compare the analog signal with the acquisition signal, and when the acquisition signal and the analog signal reach a maximum coincidence, the corresponding frequency position is the center frequency.

Preferably, the signal acquisition module 120 includes:

The system information acquisition unit 121 is used to select a specific field strength system and human body scanning part, and determine the corresponding signal points, water-fat frequency difference and the proportion of fat peak and water peak;

The signal deriving unit 122 is used for substituting the number of signal points, the frequency difference between water and fat, and the proportion of fat peak and water peak into the standard function to obtain an analog signal.

Preferably, the center frequency search module 140 includes:

A correlation matrix calculation unit 141, configured to calculate a cross-correlation matrix [coef, pos] between the analog signal and the collected signal;

Numerical search unit 142, used to find the pos value when the coef maximum value;

The frequency converting unit 143 is configured to convert the pos value when coef is at a maximum value into a center frequency f.

FIG. 7 is a schematic structural diagram of a terminal device according to the present invention. As shown in FIG. 7, the terminal device includes: at least one processor 701 and a memory 702;

The memory stores a computer program; the at least one processor executes the computer program stored in the memory, so as to implement the method for finding the center frequency provided in the above embodiment.

Still another embodiment of the present invention also provides a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed, the above-mentioned method for finding a center frequency is implemented.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, devices, or computer program products. Accordingly, embodiments of the invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, embodiments of the invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

Embodiments of the present invention are described with reference to flowcharts and/or block diagrams of methods, electronic devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general-purpose computer, special purpose computer, embedded processor, or processor of other programmable data-processing electronics to produce a machine such that instructions executed by the processor of the computer or other programmable data-processing electronics Produce means for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing electronic device to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the The instruction means implements the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be loaded into a computer or other programmable electronic device, causing a series of operational steps to be performed on the computer or other programmable electronic device to produce computer-implemented processing, thereby The instructions executed above provide steps for implementing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

Having described preferred embodiments of embodiments of the present invention, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, the appended claims are intended to be construed to cover the preferred embodiment and all changes and modifications which fall within the scope of the embodiments of the present invention.

Finally, it should also be noted that in this text, relational terms such as first and second etc. are only used to distinguish one entity or operation from another, and do not necessarily require or imply that these entities or operations, any such actual relationship or order exists. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or electronic device that includes a set of elements includes not only those elements, but also includes elements not expressly listed. other elements identified, or also include elements inherent in such a process, method, article, or electronic device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or electronic device comprising said element.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be described in the foregoing embodiments Modifications are made to the recorded technical solutions, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. A method for finding center frequency, characterized in that the steps comprise: Construct a standard function; According to the standard function, the analog signal of the human body scanning part under the magnetic resonance field strength system is obtained; Acquiring a group of acquisition signals of the scanning parts of the human body under the magnetic resonance field strength system; Comparing the analog signal with the acquisition signal, when the acquisition signal and the analog signal reach the maximum overlap, the corresponding frequency position is the center frequency; The standard functions are as follows: stdSignal＝GenerateSimSig(N,△f _wf ,w) formula (1) The specific form of expression is: S _std (n,△f _wf ,w)=g(n)+w g(n-△f _wf /△f _p )n=1,2,...N Among them, in formula (1), g(n) is a Gaussian function, N represents the number of signal points, △f _wf represents the frequency difference between water and fat; △f _p represents the frequency difference between two signal points, and w represents the fat peak and water peak proportion. 2. the method for searching center frequency according to claim 1, is characterized in that, described according to described standard function draws the analog signal of human body scan position under a magnetic resonance field strength system, specifically: Select a specific field strength system and human body scanning part, and determine the corresponding signal points, water-fat frequency difference and the proportion of fat peak and water peak; The analog signal is obtained by substituting the number of signal points, the frequency difference between water and fat, and the proportion of fat peak and water peak into the standard function. 3. The method for finding the center frequency according to claim 1, wherein the analog signal is compared with the acquisition signal, and when the acquisition signal diagram and the analog signal diagram reach the maximum coincidence The corresponding frequency position is the center frequency, including: Calculating a cross-correlation matrix [coef, pos] between the analog signal and the collected signal; Find the pos value when the maximum value of coef is found; Convert the pos value at the maximum value of coef to the center frequency f. 4. the method for searching central frequency according to claim 3, is characterized in that, described cross-correlation matrix [coef, pos] is: [coef,pos]=cro_cor(stdSignal ₀ ,realSignal) formula (2) Among them, in formula (2), stdSignal ₀ represents the analog signal, realSignal represents the collected signal, coef represents the correlation coefficient of the coincidence degree between the analog signal and the collected signal, pos represents the relative distance that the analog signal moves relative to the collected signal, and cro_cor is the standard Find the signal correlation function. 5. A device for finding the center frequency, comprising: A function construction module, used to construct a standard function; The signal acquisition module is used to obtain the analog signal of the human body scanning part under the magnetic resonance field strength system according to the standard function; A signal acquisition module, configured to acquire a group of acquisition signals of the human body scanning parts under the magnetic resonance field strength system; The center frequency search module is used to compare the analog signal with the acquisition signal, and when the acquisition signal and the analog signal reach the maximum overlap, the corresponding frequency position is the center frequency. 6. The device for searching center frequency according to claim 5, said signal acquisition module comprising: The system information acquisition unit is used to select a specific field strength system and human body scanning part, and determine the corresponding signal points, water-fat frequency difference and the proportion of fat peak and water peak; The signal deriving unit is used for substituting the number of signal points, the frequency difference of water and fat, and the proportion of fat peak and water peak into the standard function to obtain an analog signal. 7. The device for searching center frequency according to claim 5, wherein said center frequency search module comprises: A correlation matrix calculation unit, configured to calculate a cross-correlation matrix [coef, pos] between the analog signal and the collected signal; A value search unit, used to find the pos value when the coef is at its maximum value; The frequency conversion unit is used to convert the pos value at the maximum value of coef to the center frequency f. 8. A terminal device, characterized in that it comprises: at least one processor and a memory; the memory stores a computer program; and the at least one processor executes the computer program stored in the memory, so as to implement claims 1-4. The method for finding the center frequency described in any one. 9. A computer-readable storage medium, characterized in that, a computer program is stored in the computer-readable storage medium, and when the computer program is executed, the method of searching the central frequency according to any one of claims 1-5 is realized. method.

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