A medical cyclotron beam measurement signal protection method and system

Abstract

The present application relates to the technical field of particle radiation measurement, and specifically to a medical cyclotron beam measurement signal protection method and system, the method comprising: using a signal decomposition algorithm to obtain each current decomposition signal at each moment from the probe current vector at each moment; analyzing the correlation between each filtered current decomposition signal and the probe position vector at the corresponding moment, obtaining the distance current similarity of each current decomposition signal at each moment; analyzing the center frequency of the deflection magnetic field vector at each moment and the center frequency of each current decomposition signal, as well as the difference from the fixed frequency, determining the noise frequency domain characteristics of each current decomposition signal at each moment; determining the denoising threshold of each current decomposition signal at each moment according to the discrete degree of each current decomposition signal at each moment; and obtaining the protected beam measurement signal. Thus, the accuracy of the beam measurement signal is improved.

Description

Technical Field

[0001] The present application relates to the technical field of particle radiation measurement, and in particular to a medical cyclotron beam measurement signal protection method and system. Background Art

[0002] The medical small negative hydrogen cyclotron is a particle accelerator used to produce radioactive drugs. It bombards the target material with accelerated particles, changes the nuclear structure of the target material, and produces radioactive substances. Since the cyclotron particle accelerator uses high-frequency current to form a high-frequency electric field to accelerate the particles, and the radial probe, as a metal material, will form interference current due to the coupling effect of the high-frequency electric field, this part of the current is a noise current when measuring the beam intensity, which interferes with the beam measurement signal. Therefore, it is necessary to adopt noise filtering and other methods to protect the beam measurement signal and improve the cyclotron beam measurement accuracy.

[0003] An invention with publication number CN110737016A discloses a main radial probe signal calibration system and method for a cyclotron accelerator. When the method uses two-dimensional surface fitting to process data, the abstract mathematical model constructed assumes that when the probe position and the high-frequency signal power are determined, the background noise is constant, which means that the beam measurement signal is subject to a stable interference current. However, since the interference current generated by the high-frequency electric field in the particle cyclotron accelerator is generated through coupling, the interference current has high-frequency fluctuations. When the measurement resolution is low, the fluctuations of the interference current can be ignored. However, in order to further ensure the stability of the particle beam intensity, when the measurement resolution requirement is improved, ignoring the high-frequency fluctuations of the interference current will have a greater impact on the protection of the beam measurement signal and reduce the accuracy of the beam measurement signal. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a medical cyclotron beam measurement signal protection method and system, and the technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for protecting a medical cyclotron beam measurement signal, the method comprising the following steps:

[0006] After placing the radial probe into the medical cyclotron, the probe is started to collect the induced current of the radial probe at each time, and the distance between the center of the radial probe and the center of the cyclotron at each time; the magnetic field strength of the deflection magnetic field in the cyclotron at each time, and the fixed frequency of the high-frequency electric field in the cyclotron;

[0007] The induced current, the distance, and the magnetic field strength at each moment and its adjacent moments are respectively formed into a probe current vector, a probe position vector, and a deflection magnetic field vector;

[0008] The probe current vector at each moment is used to obtain each current decomposition signal at each moment by using a signal decomposition algorithm; the correlation between each filtered current decomposition signal and the probe position vector at the corresponding moment is analyzed to obtain the distance current similarity of each current decomposition signal at each moment; the center frequency of the deflection magnetic field vector at each moment and the center frequency of each current decomposition signal, as well as the difference with the fixed frequency, are analyzed, and the noise frequency domain characteristics of each current decomposition signal at each moment are determined in combination with the distance current similarity;

[0009] According to the discrete degree of each current decomposition signal at each moment, combined with the noise frequency domain characteristics, the denoising threshold of each current decomposition signal at each moment is determined; combined with the denoising threshold and each current decomposition signal at each moment, the protected beam current measurement signal is obtained.

[0010] In one embodiment, the filtering step is:

[0011] The absolute value of each element in each current decomposition signal is taken and then filtered using a filtering algorithm to obtain a smoothed current decomposition signal of each current decomposition signal.

[0012] In one embodiment, the determination of the distance current similarity includes:

[0013] The cosine similarity between the probe position vector at each moment and each smoothed current decomposition signal is calculated and determined as the distance current similarity.

[0014] In one embodiment, the process of determining the center frequency of the deflection magnetic field vector is as follows:

[0015] The deflection magnetic field vector at each moment is converted into frequency domain, the product of each frequency and the normalized value of the corresponding amplitude is calculated, and the sum of all the products corresponding to the deflection magnetic field vector is determined as the central frequency of the deflection magnetic field vector at each moment.

[0016] In one embodiment, the process of determining the center frequency of the current decomposition signal is as follows:

[0017] The same calculation method as that for the center frequency of the deflection magnetic field vector is used to obtain the center frequency of the current decomposition signal.

[0018] In one embodiment, the determination of the noise frequency domain characteristics includes:

[0019] Calculate the absolute value of the difference between the center frequency of each current decomposition signal at each moment and the center frequency of the deflection magnetic field vector at the corresponding moment, and the absolute value of the difference with the fixed frequency, and record them as the first absolute value of the difference and the second absolute value of the difference respectively; determine the noise frequency domain feature based on the first absolute value of the difference, the second absolute value of the difference, and the distance current similarity;

[0020] The noise frequency domain feature is positively correlated with the first difference absolute value, and negatively correlated with the second difference absolute value and the distance current similarity.

[0021] In one embodiment, the denoising threshold is the product of the discreteness of each current decomposition signal at each moment and the normalized value of the noise frequency domain feature.

[0022] In one embodiment, the protected beam current measurement signal includes:

[0023] Based on the denoising threshold, a threshold suppression operation is performed on each current decomposition signal to obtain a noise-filtered current decomposition signal of each current decomposition signal. All noise-filtered current decomposition signals at each moment are subjected to an inverse transformation algorithm of signal decomposition to obtain a filtered probe current vector at each moment. The element value corresponding to the induced current at each moment in the filtered probe current vector is used as the beam measurement signal value after protection at each moment.

[0024] In one embodiment, the performing a threshold suppression operation on each current decomposition signal based on the denoising threshold comprises:

[0025] If the absolute value of the corresponding value of the induced current at each moment in each current decomposition signal is less than the corresponding denoising threshold, the corresponding value is set to 0, otherwise, no processing is performed.

[0026] In a second aspect, an embodiment of the present application further provides a medical cyclotron beam measurement signal protection system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned methods when executing the computer program.

[0027] This application has at least the following beneficial effects:

[0028] The present application aims at the problem that the existing medical cyclotron accelerator cannot accurately filter the interference of high-frequency field leakage from the beam measurement signal in the face of high-resolution measurement requirements when protecting the beam measurement signal. A radial probe is placed in the medical cyclotron and started, and the induced current of the radial probe at each moment and the distance between the center of the radial probe and the center of the cyclotron at each moment are collected; the magnetic field strength of the deflection magnetic field in the cyclotron at each moment and the fixed frequency of the high-frequency electric field in the cyclotron are collected; the induced current, the distance, and the magnetic field strength at each moment and its adjacent moments are respectively formed into a probe current vector, a probe position vector, and a deflection magnetic field vector; the probe current vector at each moment is used The signal decomposition algorithm obtains each current decomposition signal at each moment, reflecting the frequency domain characteristics of the probe current vector; the correlation between each filtered current decomposition signal and the probe position vector at the corresponding moment is analyzed to obtain the distance current similarity of each current decomposition signal at each moment, characterizing the interference current content caused by high-frequency field leakage in different current decomposition signals; further, the center frequency of the deflection magnetic field vector at each moment and the center frequency of each current decomposition signal, as well as the difference with the fixed frequency, are analyzed, and the noise frequency domain characteristics of each current decomposition signal at each moment are determined in combination with the distance current similarity, reflecting the noise content in different current decomposition signals at different moments, thereby improving the accuracy of current decomposition signal noise extraction. Finally, according to the discrete degree of each current decomposition signal at each moment, combined with the noise frequency domain characteristics, the denoising threshold of each current decomposition signal at each moment is determined; the determination of the denoising threshold improves the denoising accuracy of the current decomposition signal, and the beam measurement signal after protection is obtained by combining the denoising threshold and each current decomposition signal at each moment, thereby reducing the measurement error of the beam measurement signal, and protecting the beam measurement signal from the influence of high-frequency field leakage noise under the requirement of high measurement resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A flowchart of a medical cyclotron beam measurement signal protection method provided in one embodiment of the present application;

[0031] Figure 2 Get a flow chart for denoising thresholding. DETAILED DESCRIPTION

[0032] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of a medical cyclotron beam measurement signal protection method and system proposed in accordance with the present application, its specific implementation, structure, features and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0033] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0034] The following is a detailed description of a medical cyclotron beam measurement signal protection method and system provided by the present application in conjunction with the accompanying drawings.

[0035] See also Figure 1 , which shows a flowchart of a medical cyclotron beam measurement signal protection method provided by an embodiment of the present application, the method comprising the following steps:

[0036] S1, obtaining the fixed frequency of the high-frequency electric field in the medical cyclotron, and obtaining the probe current vector, probe position vector, and deflection magnetic field vector at each moment.

[0037] After placing the radial probe into the medical cyclotron, start the medical cyclotron and measure the induced current of the radial probe at each moment. Measure the distance between the center of the radial probe and the center of the cyclotron at each moment. The closer the distance, the deeper the radial probe goes into the medical cyclotron, and the more serious the interference caused by the high-frequency field leakage. Collect the magnetic field strength of the deflection magnetic field in the medical cyclotron at each moment. Obtain the fixed frequency of the high-frequency electric field in the medical cyclotron.

[0038] In this embodiment, the sampling period for collecting the induced current, the distance, and the magnetic field strength is 0.1 milliseconds. Taking the induced current at each moment as an example, TS-1 induced current data are obtained forward, and are arranged in time sequence together with the induced current at each moment to form a probe current vector with a length of TS at each moment; the same acquisition method as that of the probe current vector is adopted to obtain the probe position vector and the deflection magnetic field vector at each moment for the distance and the magnetic field strength.

[0039] In this embodiment, TS=200. The implementer can set the sampling period and the value of TS according to the actual situation, and this application does not impose any restrictions on this.

[0040] It should be noted that, in order to ensure the reliability of data analysis, the probe current vector, probe position vector, and deflection magnetic field vector at each moment are obtained in this embodiment 1 second after starting the medical cyclotron, wherein the interval time can be set by the implementer according to actual conditions, and this application does not impose any restrictions on this.

[0041] S2, using the signal decomposition algorithm to obtain each current decomposition signal at each moment by using the probe current vector at each moment; analyzing the correlation between each filtered current decomposition signal and the probe position vector at the corresponding moment, and obtaining the distance current similarity of each current decomposition signal at each moment.

[0042] When measuring beam intensity through a radial probe, the main source of interference to the beam measurement signal is the leaked high-frequency electric field. The leakage of the high-frequency electric field will generate coupling current in the probe, causing inaccurate beam measurement signals. Since the high-frequency electric field has a large power, other metal components in the cyclotron will also generate large coupling currents, which will also generate a changing magnetic field. Therefore, the interference current components in the radial probe are complex; however, the source of the coupling current is the high-frequency electric field, so the frequency of the main interference current component in the radial probe is similar to the high-frequency electric field, and other interference current components are also close to the frequency of the high-frequency electric field. Therefore, this embodiment extracts the frequency domain characteristics of the induced current in the radial probe from the frequency domain.

[0043] Therefore, this embodiment uses the probe current vector at each moment as input and uses the wavelet decomposition algorithm for calculation. The necessary parameters of the wavelet decomposition algorithm in this embodiment include: using Haar wavelet transform, the number of decompositions is M=5, and the output is M current decomposition signals. The number of decompositions can be set by the implementer according to the actual situation, and this application does not limit this.

[0044] It should be noted that the Haar wavelet transform algorithm is an existing well-known technology and will not be described in detail in this application. The implementer can choose other signal decomposition algorithms according to actual conditions and this application does not impose any restrictions on this.

[0045] The current decomposition signal contains probe current signals of different frequency components. The current decomposition signal with higher frequency and close to the high-frequency electric field noise frequency is more likely to be a noise signal. As for the current component caused by the beam in the current decomposition signal, its size should change with the beam intensity, because the stronger the beam intensity changes, the higher the corresponding current decomposition signal frequency.

[0046] In a medical cyclotron, since the radial probe measures along the radius of the medical cyclotron and the charge of individual particles in the medical cyclotron is the same, the direct factor affecting the current generated by the beam in the radial probe is the angular velocity of the particles in the medical cyclotron. The greater the angular velocity of the particles, the greater the current generated by the beam in the probe.

[0047] In medical cyclotron accelerators, the main factor affecting the angular velocity of particles is the size of the deflection magnetic field. The deflection magnetic field and the angular velocity of particles are positively correlated. The larger the deflection magnetic field, the greater the angular velocity.

[0048] Therefore, this embodiment determines the frequency of the current generated by the beam in the radial probe according to the frequency of the deflection magnetic field vector at each moment. The more similar the frequency of the current decomposition signal is to the frequency of the deflection magnetic field vector, the more the corresponding current decomposition signal conforms to the frequency domain characteristics of the beam.

[0049] The deflection magnetic field vector at each moment is subjected to a fast Fourier transform algorithm to obtain a frequency spectrum of the deflection magnetic field vector at each moment, wherein the horizontal axis of the frequency spectrum is frequency and the vertical axis is amplitude. The product of each frequency and the normalized value of the corresponding amplitude in the frequency spectrum of the deflection magnetic field vector at each moment is calculated, and the sum of all the products corresponding to the deflection magnetic field vector is determined as the central frequency of the deflection magnetic field vector at each moment.

[0050] It should be understood that the fast Fourier transform algorithm is an existing well-known technology, and this application will not elaborate on it in detail. The implementer can choose other frequency domain conversion algorithms according to actual conditions, and this application does not limit it.

[0051] Since the magnitude of the deflection magnetic field corresponds to the magnitude of the beam signal in the radial probe, the center frequency of the deflection magnetic field vector at each moment can be recorded as the beam characteristic frequency at each moment.

[0052] Although in the current decomposition signal, the closer the center frequency is to the fixed frequency of the high-frequency electric field, the more noise it contains, the interference current component caused by the leakage of the high-frequency electric field is complex, and the high-frequency information may still contain part of the beam signal, and the low-frequency information will also contain the interference current caused by the high-frequency leakage electric field. Therefore, it is necessary to analyze the noise components in different current decomposition signals to accurately filter out the interference of the high-frequency electric field leakage.

[0053] Since the interference current components caused by high-frequency electric field leakage are complex, when the radial probe is measured at different distances in the cyclotron, the interference of the high-frequency electric field leakage is also different. The deeper the radial probe goes into the medical cyclotron, the more serious the interference from the high-frequency electric field leakage is. Therefore, it is necessary to analyze the relationship between the current decomposition signal intensity and the change of the radial probe position to determine the noise content in the current decomposition signal.

[0054] First, each current decomposition signal at each moment is filtered to eliminate the influence of signal fluctuation on the judgment of signal strength. Specifically, the absolute value of each element in each current decomposition signal at each moment is taken, and recorded as the current intensity decomposition signal of each current decomposition signal at each moment. Then, the current intensity decomposition signal at each moment is used as input and calculated using the mean filtering algorithm. In this embodiment, the filter window length is 5, and the implementer can set it according to the actual situation. This application does not impose any restrictions on this. The output of the mean filtering algorithm is the smoothed current decomposition signal of each current decomposition signal at each moment.

[0055] It should be noted that the mean filtering algorithm is an existing well-known technology, and this application will not elaborate on it in detail. The implementer can choose other filtering algorithms according to actual conditions, and this application does not impose any restrictions on this.

[0056] Furthermore, the similarity between the probe position vector at each moment and each smoothed current decomposition signal is calculated to determine the distance current similarity of each current decomposition signal at each moment.

[0057] In this embodiment, taking time t as an example, the cosine similarity between the probe position vector at time t and the smoothed current decomposition signal of the mth current decomposition signal at time t is calculated to determine the distance current similarity of the mth current decomposition signal at time t.

[0058] The value range of the distance current similarity is between -1 and 1. The closer the distance current similarity is to -1, the closer the radial probe is to the center of the cyclotron, the stronger the interference from the high-frequency electric field leakage is, the greater the current intensity of the mth current decomposition signal is, and the more likely the mth current decomposition signal is to be noise data.

[0059] The same calculation method as that of the distance current similarity of the mth current decomposition signal at time t is used to obtain the distance current similarity of each current decomposition signal at each time.

[0060] It should be understood that the calculation of cosine similarity is a known technique and will not be described in detail in this application. In another embodiment, the cosine similarity may be replaced by the Pearson correlation coefficient to calculate the distance current similarity.

[0061] S3, analyzing the center frequency of the deflection magnetic field vector at each moment and the center frequency of each current decomposition signal, as well as the difference with the fixed frequency, and combining the distance current similarity to determine the noise frequency domain characteristics of each current decomposition signal at each moment.

[0062] Firstly, the same calculation method as that for the center frequency of the deflection magnetic field vector at each moment is used to obtain the center frequency of each current decomposition signal at each moment, which is recorded as the characteristic frequency of the decomposed signal.

[0063] The more similar the characteristic frequency of the sub-signals of the current decomposition signal at each moment is to the characteristic frequency of the beam at the corresponding moment, the more beam signal information there is in the current decomposition signal;

[0064] Respectively calculating the absolute value of the difference between the center frequency of each current decomposition signal at each moment and the center frequency of the deflection magnetic field vector at the corresponding moment, recorded as the first absolute value of the difference, and the absolute value of the difference with the fixed frequency, recorded as the second absolute value of the difference, and determining the noise frequency domain characteristics of each current decomposition signal at each moment based on the first absolute value of the difference, the second absolute value of the difference, and the distance current similarity;

[0065] The noise frequency domain feature is positively correlated with the first difference absolute value, and negatively correlated with the second difference absolute value and the distance current similarity.

[0066] It should be noted that a positive correlation means that the dependent variable will increase as the independent variable increases, and the dependent variable will decrease as the independent variable decreases. A negative correlation means that the dependent variable will decrease as the independent variable increases, and the dependent variable will increase as the independent variable decreases.

[0067] In this embodiment, the noise frequency domain characteristics of the mth current decomposition signal at time t are The expression can be:

[0068] ; In the formula, is the characteristic frequency of the sub-signal of the mth current decomposition signal at time t, is the characteristic frequency of the beam at time t, is the fixed frequency of the high-frequency electric field, is the distance current similarity of the mth current decomposition signal at time t, z is a very small value to prevent the denominator from being 0, in this embodiment z is 0.01, the implementer can set it according to the actual situation, and this application does not limit it. Recorded as the absolute value of the first difference, Recorded as the second difference absolute value.

[0069] The greater the difference between the characteristic frequency of the sub-signals of the mth current decomposition signal and the characteristic frequency of the beam at the corresponding moment, the fewer beam measurement signal components the mth current decomposition signal contains; the smaller the difference between the characteristic frequency of the sub-signals of the mth current decomposition signal and the fixed frequency of the high-frequency electric field, the more high-frequency electric field leakage interference information the mth current decomposition signal contains; the larger the value of 1 minus the distance current similarity is, the closer the distance current similarity is to -1, which means that the mth current decomposition signal contains more interfering current components caused by high-frequency field leakage; the larger the final noise frequency domain characteristics are, the more interference information of high-frequency field leakage the mth current decomposition signal contains.

[0070] S4, determining the denoising threshold of each current decomposition signal at each moment according to the discrete degree of each current decomposition signal at each moment in combination with the noise frequency domain characteristics; combining the denoising threshold and each current decomposition signal at each moment to obtain the protected beam measurement signal.

[0071] Finally, the current decomposition signal is denoised according to the noise frequency domain characteristics. The current decomposition signal with a larger noise frequency domain characteristic should have a greater noise filtering strength to eliminate the interference current caused by high-frequency field leakage. This embodiment uses a threshold-suppressed wavelet denoising method to complete the correction protection of the beam measurement signal, specifically:

[0072] First, the denoising threshold is set for different current decomposition signals according to the noise frequency domain characteristics. The denoising threshold calculation method is:

[0073] Taking the mth current decomposition signal at time t as an example, in this embodiment, the standard deviation of all elements in the mth current decomposition signal at time t is calculated and recorded as the local standard deviation , the maximum and minimum normalization method is used to normalize the noise frequency domain characteristics of all current decomposition signals at time t, and the normalized noise frequency domain characteristics of the mth current decomposition signal at time t are obtained. , then the calculation method of the denoising threshold of the mth current decomposition signal at time t is: ,in, It represents the denoising threshold of the mth current decomposition signal at time t. The denoising threshold acquisition flow chart is as follows: Figure 2 shown.

[0074] It should be noted that, in another embodiment, the standard deviation of the standard deviations of all elements may be replaced by the variance to perform subsequent calculation of the denoising threshold. The maximum and minimum normalization method is a known technique, which is not described in detail in this application, and the implementer may choose other normalization methods at will, which is not limited in this application.

[0075] Further, a threshold suppression operation is performed on the mth current decomposition signal, specifically: when the absolute value of the element value corresponding to the induced current measured at time t in the mth current decomposition signal is less than When , the corresponding element value is set to 0, otherwise, the mth current decomposition signal is not processed. The mth current decomposition signal after the threshold suppression operation is recorded as the noise-filtered current decomposition signal, and the noise-filtered current decomposition signal of all current decomposition signals at time t is obtained by the same acquisition method as that of the noise-filtered current decomposition signal of the mth current decomposition signal at time t.

[0076] Finally, the noise-filtered current decomposition signal of all current decomposition signals at time t is used as input, and the inverse wavelet decomposition algorithm is used for calculation. The output of the inverse wavelet decomposition algorithm is a vector, which is recorded as the probe current filtering vector. The last element value in the probe current filtering vector is used as the beam measurement signal data after the beam measurement signal is corrected and protected at time t, representing the size of the beam measurement signal at time t. It can eliminate the influence of high-frequency field leakage on the beam measurement signal under high-resolution requirements and reduce the measurement error of the beam measurement signal. The inverse wavelet decomposition algorithm is an existing well-known technology, and this application will not be described in detail.

[0077] The same calculation method as that for the corrected and protected beam current measurement signal data at time t is adopted to obtain the corrected and protected beam current measurement signal data at each time.

[0078] Based on the same inventive concept as the above method, an embodiment of the present application also provides a medical cyclotron beam measurement signal protection system, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above-mentioned medical cyclotron beam measurement signal protection methods are implemented.

[0079] In summary, the present application aims at the problem that the existing medical cyclotron cannot accurately filter the interference of high-frequency field leakage from the beam measurement signal when protecting the beam measurement signal due to the requirement of high-resolution measurement. The radial probe is placed in the medical cyclotron and started up to collect the induced current of the radial probe at each moment and the distance between the center of the radial probe and the center of the cyclotron at each moment; collect the magnetic field strength of the deflection magnetic field in the cyclotron at each moment and the fixed frequency of the high-frequency electric field in the cyclotron; respectively form the probe current vector, probe position vector and deflection magnetic field vector with the induced current, distance and magnetic field strength at each moment and its adjacent moments; and calculate the probe current vector at each moment. The signal decomposition algorithm is used to obtain the current decomposition signals at each moment, which reflects the frequency domain characteristics of the probe current vector; the correlation between the filtered current decomposition signals and the probe position vector at the corresponding moment is analyzed to obtain the distance current similarity of the current decomposition signals at each moment, which characterizes the interference current content caused by the high-frequency field leakage in different current decomposition signals; further, the center frequency of the deflection magnetic field vector at each moment and the center frequency of each current decomposition signal, as well as the difference with the fixed frequency, are analyzed, and the noise frequency domain characteristics of each current decomposition signal at each moment are determined in combination with the distance current similarity, which reflects the noise content in different current decomposition signals at different moments and improves the accuracy of noise extraction of current decomposition signals. Finally, according to the discrete degree of each current decomposition signal at each moment and the noise frequency domain characteristics, the denoising threshold of each current decomposition signal at each moment is determined; the determination of the denoising threshold improves the denoising accuracy of the current decomposition signal, and the beam measurement signal after protection is obtained by combining the denoising threshold and the current decomposition signals at each moment, which reduces the measurement error of the beam measurement signal and protects the beam measurement signal from the influence of high-frequency field leakage noise under the requirement of high measurement resolution.

[0080] It should be noted that the above sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above is a description of a specific embodiment of this specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0081] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0082] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A medical cyclotron beam measurement signal protection method, characterized in that: The method comprises the following steps: After placing the radial probe into the medical cyclotron, the probe is started to collect the induced current of the radial probe at each time, and the distance between the center of the radial probe and the center of the cyclotron at each time; the magnetic field strength of the deflection magnetic field in the cyclotron at each time, and the fixed frequency of the high-frequency electric field in the cyclotron; The induced current, the distance, and the magnetic field strength at each time and its adjacent time are respectively formed into a probe current vector, a probe position vector, and a deflection magnetic field vector; The probe current vector at each moment is used to obtain each current decomposition signal at each moment by using a signal decomposition algorithm; the correlation between each filtered current decomposition signal and the probe position vector at the corresponding moment is analyzed to obtain the distance current similarity of each current decomposition signal at each moment; the difference between the center frequency of the deflection magnetic field vector at each moment and the center frequency of each current decomposition signal, as well as the difference between the center frequency of each current decomposition signal at each moment and the fixed frequency are analyzed, and the noise frequency domain characteristics of each current decomposition signal at each moment are determined in combination with the distance current similarity; Determine the denoising threshold of each current decomposition signal at each moment according to the discrete degree of each current decomposition signal at each moment in combination with the noise frequency domain characteristics; obtain the protected beam current measurement signal by combining the denoising threshold and each current decomposition signal at each moment; The process of determining the center frequency of the deflection magnetic field vector is as follows: Performing frequency domain conversion on the deflection magnetic field vector at each moment, calculating the product of each frequency and the normalized value of the corresponding amplitude, and determining the sum of all the products corresponding to the deflection magnetic field vector as the central frequency of the deflection magnetic field vector at each moment; The process of determining the center frequency of the current decomposition signal is as follows: The same calculation method as that for the center frequency of the deflection magnetic field vector is adopted to obtain the center frequency of the current decomposition signal for the current decomposition signal.

2. A medical cyclotron beam measurement signal protection method as claimed in claim 1, characterized in that: The filtering steps are: The absolute value of each element in each current decomposition signal is taken and then filtered using a filtering algorithm to obtain a smoothed current decomposition signal of each current decomposition signal.

3. A medical cyclotron beam measurement signal protection method as claimed in claim 2, characterized in that: The determination of the distance current similarity includes: The similarity between the probe position vector at each moment and each smoothed current decomposition signal is calculated and determined as the distance current similarity.

4. A medical cyclotron beam measurement signal protection method as claimed in claim 1, characterized in that: The determination of the noise frequency domain characteristics includes: Calculate the absolute value of the difference between the center frequency of each current decomposition signal at each moment and the center frequency of the deflection magnetic field vector at the corresponding moment, and the absolute value of the difference with the fixed frequency, and record them as the first absolute value of the difference and the second absolute value of the difference respectively; determine the noise frequency domain feature based on the first absolute value of the difference, the second absolute value of the difference, and the distance current similarity; The noise frequency domain feature is positively correlated with the first difference absolute value, and negatively correlated with the second difference absolute value and the distance current similarity.

5. A medical cyclotron beam measurement signal protection method as claimed in claim 1, characterized in that: The denoising threshold is the product of the discreteness of each current decomposition signal at each moment and the normalized value of the noise frequency domain feature.

6. A medical cyclotron beam measurement signal protection method as claimed in claim 1, characterized in that: The protected beam current measurement signal comprises: Based on the denoising threshold, each current decomposition signal is denoised to obtain a filtered current decomposition signal of each current decomposition signal, and all the filtered current decomposition signals at each moment are decomposed using an inverse transformation algorithm of signal decomposition to obtain a filtered probe current vector at each moment, and the element value corresponding to the induced current at each moment in the filtered probe current vector is obtained, and the corresponding element value is used as the beam measurement signal value after protection at each moment.

7. A medical cyclotron beam measurement signal protection method as claimed in claim 6, characterized in that: The denoising of each current decomposition signal based on the denoising threshold comprises: The corresponding value of the induced current at each moment in each current decomposition signal is obtained. If the absolute value of the corresponding value is less than the corresponding denoising threshold, the corresponding value is set to 0, otherwise, no processing is performed.

8. A medical cyclotron beam measurement signal protection system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

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