Main radial probe signal calibration method for medical cyclotron

Abstract

The invention relates to the technical field of signal calibration, in particular to a main radial probe signal calibration method for a medical cyclotron, and the method comprises the steps: collecting probe current data, and constructing a probe current data sequence; further obtaining a time domain amplitude fluctuation degree; calculating the time domain baseline stability degree of each period; obtaining the time domain noise interference degree of each probe position; obtaining the frequency domain bandwidth difference of each probe position; obtaining the frequency domain noise interference degree of each probe position; and acquiring an external noise interference degree based on the time domain noise interference degree and the frequency domain noise interference degree, and calibrating the main radial probe signal. According to the invention, the actual beam current intensity can be evaluated more accurately.

Description

Technical Field

[0001] The present application relates to the technical field of signal calibration, and in particular to a main radial probe signal calibration method for a medical cyclotron. Background Art

[0002] Medical cyclotron is a device used to produce radioactive isotopes. It is widely used in positron emission tomography (PET) and single photon emission computed tomography (SPECT). Its working principle is based on the repeated acceleration of charged particles under the action of magnetic field and alternating electric field until the required energy is reached, and then the particle beam is extracted through the system to bombard the target material to produce radioactive nuclides. The main radial probe is an important diagnostic tool for medical cyclotrons. It is used to measure beam current intensity and circle diagram. The precise calibration of the main radial probe signal can reduce the interference of the high-frequency electromagnetic field generated by the radio frequency unit on the measurement results.

[0003] The radio frequency unit in the medical cyclotron will generate a high-frequency electromagnetic field while accelerating the beam, thereby interfering with the measurement of the beam intensity. The existing main radial probe signal calibration method for medical cyclotrons only performs two-dimensional surface fitting on the actual power of the radio frequency unit, the real-time position of the probe and the background noise, and calibrates the beam intensity by combining the fitting result with the actual measurement value. This method has obvious limitations in considering independent variables and does not fully consider other factors that may affect the background noise, resulting in the inability to accurately reflect the actual beam intensity in the subsequent process, limiting the generalization ability of the calibration results, and may affect the auxiliary decision-making of relevant personnel. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a main radial probe signal calibration method for a medical cyclotron to solve the existing problems.

[0005] A main radial probe signal calibration method for a medical cyclotron in the present application adopts the following technical solution: An embodiment of the present application provides a method for calibrating a main radial probe signal of a medical cyclotron, the method comprising the following steps: Collecting probe current data of the main radial probe current signal at each probe position at each acquisition time, and constructing a probe current data sequence at each probe position; Based on the volatility and dispersion of each period of the probe current data sequence, the time domain amplitude fluctuation degree of each period of the probe current data sequence is obtained; based on the volatility and positive and negative changes of each period element in the probe current data sequence, the time domain baseline stability of each period is obtained; Based on the time domain amplitude fluctuation degree and the time domain baseline stability degree, the time domain noise interference degree of each probe position is obtained; The frequency domain bandwidth difference of each probe position is obtained based on the frequency domain characteristics of the probe current data sequence; the frequency domain noise interference degree of each probe position is obtained based on the frequency domain bandwidth difference and the difference between the frequency energy sequences between different cycles; The external noise interference degree is obtained based on the time domain noise interference degree and the frequency domain noise interference degree; and the main radial probe signal is calibrated based on the external noise interference degree.

[0006] Furthermore, the method for obtaining the time domain amplitude fluctuation degree is: A peak detection algorithm is used to obtain all the peaks and troughs in the probe current data sequence, and the corresponding amplitude values ​​of all the peaks and troughs in each cycle are respectively composed of a sequence in time sequence as the peak sequence and trough sequence of the probe current signal in each cycle; Calculate the approximate entropy of the probe current data sequence of each period; for each period, calculate the interquartile range of the peak sequence and the interquartile range of the trough sequence respectively, and take the sum of the interquartile range of the peak sequence and the interquartile range of the trough sequence as the first quartile sum; based on the approximate entropy and the first quartile sum, obtain the time domain amplitude fluctuation degree of each period, and the time domain amplitude fluctuation degree is positively correlated with the approximate entropy and the first quartile sum, respectively.

[0007] Furthermore, the method for obtaining the stability of the time domain baseline is: For the peak sequence and trough sequence of each period, the absolute value of the difference between each element with the same position in the peak sequence and the trough sequence is calculated as the first absolute value of the difference, and the Shannon entropy of all the first absolute values ​​of the difference is used as the baseline shift degree of each period; Based on the positive and negative changes of the elements in the probe current data sequence, the difference in the number of signal zero crossings in each cycle is obtained; The time domain baseline stability of each cycle is obtained based on the baseline offset degree and the difference in the number of signal zero crossings, and the time domain baseline stability is negatively correlated with the baseline offset degree and the difference in the number of signal zero crossings, respectively.

[0008] Further, the method for obtaining the difference in the number of times the signal crosses zero is: For each probe current data in the probe current data sequence of each cycle, when the value of the probe current data is greater than zero and the value of the next adjacent probe current data is less than zero, or when the value of the probe point pair data is less than zero and the value of the next adjacent probe current data is greater than zero, the value of the signal zero crossing times of each cycle is added with the number 1; The sequence composed of the number of signal zero crossings of the probe current signal amplitude in all cycles before each cycle in the periodic time sequence is taken as the historical zero crossing sequence of each cycle; the cumulative result of the absolute value of the difference between the number of signal zero crossings of each cycle and each data in the corresponding historical zero crossing sequence is calculated as the difference in the number of signal zero crossings of each cycle.

[0009] Furthermore, the method for obtaining the time domain noise interference degree is: The time domain interference coefficient is the ratio of the time domain amplitude fluctuation degree to the time domain baseline stability degree; The accumulated result of the time domain interference coefficients of all the cycles of each probe position during the probe movement is taken as the time domain noise interference degree of the probe at each probe position.

[0010] Furthermore, the method for obtaining the frequency domain bandwidth difference is: Obtain a spectrum diagram of the probe current signal in each cycle; The sequence of the 3 db bandwidth of the envelope of the fundamental frequency signal of the spectrum diagram corresponding to all periods of the probe current signal obtained by the probe at each probe position is composed in a periodic time sequence as the bandwidth sequence of the probe current signal at each probe position; Based on the frequency components and bandwidth sequence in the spectrum diagram of the probe current signal, the frequency component number difference and the fundamental bandwidth steady-state factor of each probe position are obtained; The frequency domain bandwidth difference of the probe current signal at each probe position is determined according to the difference in the number of frequency components of the probe current signal at each probe position and the baseband bandwidth steady-state factor. The frequency domain bandwidth difference is positively correlated with the difference in the number of frequency components and negatively correlated with the baseband bandwidth steady-state factor.

[0011] Furthermore, the method for obtaining the frequency component number difference and the baseband bandwidth steady-state factor is: For the spectrum diagram of the probe current signal at each probe position, the absolute value of the difference between the number of frequency components of any two periods is calculated as the second absolute value of the difference, and the accumulated result of all the second absolute values ​​of the difference is taken as the difference in the number of frequency components of the probe current signal at each probe position; the variance of all elements in the bandwidth sequence of the probe at each probe position is taken as the fundamental bandwidth steady-state factor of the probe current signal at each probe position.

[0012] Furthermore, the method for obtaining the frequency domain noise interference degree is: For each probe position, a sequence consisting of the maximum energy values ​​of all signal envelopes of the spectrum diagram in each period in ascending order of frequency is taken as the frequency energy sequence of each period; the distance between the frequency energy sequences of any two periods is calculated as the first distance, and the sum of all the first distances is taken as the peak frequency deviation degree of the probe current signal at each probe position; the product of the frequency domain bandwidth difference and the peak frequency deviation degree is calculated as the frequency domain noise interference degree of each probe position.

[0013] Furthermore, the method for obtaining the degree of interference from external noise is as follows: The product of the time domain noise interference degree and the frequency domain noise interference degree corresponding to the probe current signal at each probe position is taken as the second product, and the second products of all probe positions are normalized to obtain the external noise interference degree of each probe position.

[0014] Further, the calibration of the main radial probe signal based on the degree of external noise interference includes: Obtain the degree of external noise interference at each probe position, and perform two-dimensional surface fitting with the actual power of the radio frequency unit and the real-time position of the probe as independent variables and the degree of external noise interference at each probe position as the dependent variable; When measuring the beam intensity of a medical cyclotron, the external noise interference degree corresponding to the measured probe position and the power of the radio frequency unit in the fitting surface is used as the background noise value, and the difference between the actual measured value of the beam intensity and the background noise value is used as the calibration value of the beam intensity.

[0015] This application has at least the following beneficial effects: The present application obtains the degree of time domain noise interference according to the amplitude change characteristics of the probe current signal in the time domain, and adds analysis of the signal baseline fluctuation based on the analysis of the signal waveform law of the probe current signal in the time domain, which more accurately reflects the interference of the probe current signal by the external environmental noise in the time domain; the degree of frequency domain noise interference is obtained through the peak frequency and bandwidth characteristics of the probe current signal in the frequency domain, and the frequency components, peak frequency domain offset conditions and broadening prominence conditions introduced by the probe current signal in the frequency domain due to the external environmental noise interference are comprehensively considered, and the degree of external noise interference of the probe at each position is obtained based on the time domain noise interference degree and the frequency domain noise interference degree, and a two-dimensional surface fitting is performed with the actual power of the radio frequency unit to obtain the beam current intensity calibration value of the medical cyclotron, avoiding the limitation of only considering the electromagnetic interference noise generated by the radio frequency unit in the calibration process of the main radial probe signal of the medical cyclotron and ignoring other noise interferences in the external environment, and more accurately evaluating the actual beam current intensity, thereby realizing a main radial probe signal calibration method for a medical cyclotron. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 A flow chart of a method for calibrating a main radial probe signal for a medical cyclotron provided in the present application; Figure 2 Get the flow chart for the external noise interference level. DETAILED DESCRIPTION

[0018] 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 the main radial probe signal calibration method for a medical cyclotron 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.

[0019] 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.

[0020] A specific scheme of a main radial probe signal calibration method for a medical cyclotron provided by the present application is described in detail below in conjunction with the accompanying drawings.

[0021] An embodiment of the present application provides a method for calibrating a main radial probe signal for a medical cyclotron. Specifically, the following method for calibrating a main radial probe signal for a medical cyclotron is provided. Figure 1 , the method comprises the following steps: Step S1, obtaining current signal data during the movement of the probe, and preprocessing the obtained data.

[0022] First, connect the main radial probe unit, the radio frequency unit and the main control computer, move the probe to the minimum radius of the cyclotron, then adjust the incident power of the radio frequency unit, and synchronously record the probe position and the actual power of the radio frequency unit through the main radial probe signal calibration system of the medical cyclotron. Repeat the above process until the probe moves to the maximum radius of the medical cyclotron; wherein, the actual power is the incident power minus the reflected power, and the incident power and reflected power of the radio frequency unit are both obtained by the radio frequency unit control cabinet.

[0023] The current signal formed by the probe is acquired in real time through the main radial probe control cabinet, and the probe current data of each probe position at each moment is collected. In order to prevent the acquired current signal from having missing data, the median filling method is used to fill the missing values ​​of the probe current signal. Since the median filling method is a well-known technology, the specific acquisition process will not be described in detail.

[0024] At this point, the probe current data at each moment is arranged in chronological order to obtain a probe current data sequence based on the time sequence.

[0025] Step S2, obtaining the time domain noise interference degree according to the amplitude and baseline change characteristics of the probe current signal in the time domain; obtaining the frequency domain noise interference degree through the peak frequency and bandwidth characteristics of the probe current signal in the frequency domain; obtaining the external noise interference degree of the probe at each probe position based on the time domain noise interference degree and the frequency domain noise interference degree.

[0026] In addition to the high-frequency electromagnetic field introduced by the RF unit, external factors such as transmission lines, power supply systems, temperature fluctuations and vibrations will also cause noise interference to the probe current signal. The more serious the noise interference to the probe current signal, the more significant the irregularity or distortion of the probe current signal waveform, and the more obvious the baseline fluctuation of the current signal in the time domain due to noise interference; at the same time, the degree of external noise interference may also introduce new frequency components, thereby making the peak frequency offset or broadening in the spectrum diagram more prominent.

[0027] The probe current signal based on the timing is converted into the time domain to obtain the time domain waveform, and the period size of the probe current signal is obtained through the fundamental frequency of the probe current signal in the frequency domain. In order to more accurately evaluate the baseline offset of the probe current signal through the difference between the peaks and troughs, the probe current data sequence is used as input, and the AMPD (Automatic multiscale-based peak detection) peak detection algorithm is used to obtain all the peaks and troughs in the probe current data sequence. The sequence composed of the corresponding amplitude values ​​of all the peaks and troughs in each cycle in the timing order is used as the peak sequence and trough sequence of the probe current signal in each cycle. Among them, the AMPD peak detection algorithm is a well-known technology, and the specific acquisition process will not be described in detail.

[0028] The method for obtaining the time domain amplitude fluctuation degree of the probe current signal in each cycle is as follows: For the probe current data sequence of each period, the approximate entropy of the probe current data sequence is calculated; for each period, the interquartile ranges of the peak sequence and the trough sequence are calculated respectively, and the sum of the interquartile ranges of the peak sequence and the interquartile ranges of the trough sequence is taken as the first quartile sum; based on the approximate entropy and the first quartile sum, the time domain amplitude fluctuation degree of each period is obtained, and the time domain amplitude fluctuation degree is positively correlated with the approximate entropy and the first quartile sum.

[0029] It should be noted that the positive correlation means that the dependent variable increases as the independent variable increases, and decreases as the independent variable decreases.

[0030] Specifically, the present application proposes an embodiment, in which, for each period, the product of the approximate entropy of the probe current data sequence and the first quarter sum is used as the time domain amplitude fluctuation degree of each period.

[0031] Furthermore, the present application proposes another embodiment, in which, for each period, the sum of the approximate entropy of the probe current data sequence and the first quarter sum is calculated as the first sum, and the calculation result of an exponential function with a natural constant as the base and the first sum as the exponent is calculated as the degree of time domain amplitude fluctuation of each period.

[0032] When the interference of external environmental noise on the probe current signal is more serious, the amplitude waveform of the probe current signal in the time domain is more irregular. Furthermore, the greater the approximate entropy of the probe current data sequence of the probe current signal in each period, the greater the interquartile range of the peak sequence and the trough sequence corresponding to the probe current signal in each period.

[0033] Furthermore, in order to obtain the stability of the time domain baseline, the baseline offset degree and the difference in the number of signal zero crossings are constructed.

[0034] First, the baseline deviation degree of each cycle is obtained by: For the peak sequence and trough sequence of each period, the absolute value of the difference between all elements with the same position in the peak sequence and the trough sequence is calculated as the first absolute value of the difference, and the first absolute value of the difference is constructed by arranging them according to the position order of the first absolute value of the difference, and the Shannon entropy of the first absolute value of the difference is calculated as the baseline shift degree of each period; When the interference of external environmental noise on the probe current signal is more serious, the baseline fluctuation phenomenon of the probe current signal in the time domain period is more significant, the baseline offset is greater, and the Shannon entropy of the sequence composed of the absolute value of the amplitude difference of the same position of the peak sequence and the trough sequence corresponding to the period is greater.

[0035] Secondly, obtain the difference in the number of signal zero crossings in each cycle. The acquisition method is: For each probe current data in the probe current data sequence of each period, when the value of the probe current data is greater than zero and the value of the subsequent adjacent probe current data is less than zero, or when the value of the probe point pair data is less than zero and the value of the subsequent adjacent probe current data is greater than zero, the value of the signal zero crossing times of each period increases by one, and so on, to obtain the signal zero crossing times of the probe current data sequence of each period.

[0036] The sequence of the number of zero crossings of the probe current signal amplitude in each cycle before any cycle in the order of the cycle time is taken as the historical zero crossing sequence of each cycle; the cumulative result of the absolute value of the difference between the number of signal zero crossings in each cycle and each data in the corresponding historical zero crossing sequence is calculated as the difference in the number of signal zero crossings in each cycle.

[0037] The more serious the interference of external environmental noise on the probe current signal, the greater the difference in the number of signal zero crossings of the probe current signal in the time domain period. Furthermore, the greater the cumulative result of the absolute value of the difference between the number of amplitude zero crossings of the probe current signal in the period and each data in its corresponding historical zero crossing sequence.

[0038] Furthermore, based on the baseline shift degree and the difference in the number of signal zero crossings, the time domain baseline stability of each cycle is obtained, and the time domain baseline stability is negatively correlated with the baseline shift degree and the difference in the number of signal zero crossings, respectively.

[0039] It should be noted that the negative correlation means that the dependent variable decreases as the independent variable increases, and increases as the independent variable decreases.

[0040] Specifically, the present application proposes an embodiment, in which, for each period, the product of the baseline offset degree and the difference in the number of signal zero crossings is calculated as the first product, and the inverse of the first product is used as the time domain baseline stability degree of each period.

[0041] Furthermore, the present application proposes another embodiment, in which, for each period, the sum of the baseline offset degree and the difference in the number of signal zero crossings is calculated as a second sum, and the calculation result of an exponential function with a natural constant as the base and the negative value of the second sum as the exponent is calculated as the time domain baseline stability of each period.

[0042] When the impact of external environmental noise on the probe current signal is more serious, the baseline fluctuation of the probe current signal in the time domain is more significant, the stability of the time domain baseline is smaller, that is, the greater the baseline offset of the probe current signal in all cycles, the greater the difference in the number of signal zero crossings in all cycles.

[0043] The time domain interference coefficient of the external environmental noise on the probe current signal in each cycle can be determined by the time domain amplitude fluctuation degree of the probe current signal and the stability of the time domain baseline. The time domain interference coefficient is the ratio of the time domain amplitude fluctuation degree to the time domain baseline stability. When the time domain baseline stability is 0, the time domain amplitude fluctuation degree is proportional to the adjustment parameter The ratio of is used as the time domain interference coefficient. In this embodiment, the adjustment parameters The value is 0.1.

[0044] When the interference of external environmental noise on the probe current signal is more serious, the amplitude waveform of the probe current signal in the time domain is more irregular, the amplitude baseline offset caused by noise interference is more significant, the time domain interference coefficient is larger, and further, the time domain amplitude fluctuation is stronger and the time domain baseline stability is smaller.

[0045] The accumulated result of the time domain interference coefficients of all the cycles of each probe position during the probe movement is taken as the time domain noise interference degree of the probe at each probe position.

[0046] At this point, the degree of time domain noise interference at each probe position during the probe movement process is obtained.

[0047] The probe current signal of each cycle is converted into the frequency domain through Fourier transform to obtain the spectrum diagram of the probe current signal of each cycle.

[0048] For each probe position, a sequence composed of the maximum energy values ​​in all signal envelopes in each period in the spectrum diagram in ascending order of frequency is used as the frequency energy sequence of each period; a sequence composed of the 3db bandwidth of the fundamental frequency signal envelope of the spectrum diagram of all periods corresponding to the probe current signal obtained by the probe at each probe position in a periodic time sequence is used as the bandwidth sequence of the probe current signal at each probe position; wherein Fourier transform and 3db bandwidth calculation methods are both well-known technologies, and the specific acquisition process will not be elaborated in detail.

[0049] For the probe current signal at each probe position, the absolute value of the difference between the number of frequency components of any two periods is calculated as the second absolute value of the difference, and the accumulated result of all the second absolute values ​​of the difference is taken as the difference in the number of frequency components of the probe current signal at each probe position; the variance of all elements in the bandwidth sequence of the probe at each probe position is taken as the fundamental bandwidth steady-state factor of the probe current signal at each probe position.

[0050] When the probe current signal is more seriously interfered by the external environmental noise, the greater the difference in the number of frequency components of the probe current signal between all cycles in the frequency domain, the greater the difference in the 3db bandwidth corresponding to the baseband signal envelope between all cycles.

[0051] The frequency domain bandwidth difference of the probe current signal at each probe position is determined according to the difference in the number of frequency components of the probe current signal at each probe position and the baseband bandwidth steady-state factor. The frequency domain bandwidth difference is positively correlated with the difference in the number of frequency components and negatively correlated with the baseband bandwidth steady-state factor.

[0052] Specifically, in one embodiment of the present application, the frequency domain bandwidth difference is the ratio between the difference in the number of frequency components and the baseband bandwidth steady-state factor.

[0053] Furthermore, the present application proposes another embodiment, in which a calculation result of an exponential function with a natural constant as the base and the negative value of the baseband bandwidth steady-state factor as the exponent is calculated as the first exponent, and the product of the difference in the number of frequency components and the first exponent is calculated as the frequency domain bandwidth difference of each probe position.

[0054] When the probe current signal is more seriously disturbed by the external environmental noise, the frequency domain bandwidth difference of the probe current signal at each probe position is more obvious, the number of frequency components of the probe current signal in each cycle is more different, and the baseband bandwidth steady-state factor of each cycle is smaller.

[0055] For each probe position, the distance between any two cycles of the frequency energy sequence is calculated as the first distance, and the sum of all the first distances is used as the peak frequency deviation degree of the probe current signal at each probe position. This application uses the DTW distance as the metric distance, and the implementer can use other metric distances according to actual conditions.

[0056] When the probe current signal is more seriously disturbed by the external environmental noise, the peak frequency offset phenomenon of the probe current signal is more significant, the greater the degree of peak frequency deviation, the greater the difference in signal envelope frequency between all cycles corresponding to the probe current signal, and further, the greater the DTW distance between all periodic frequency energy sequences corresponding to the probe current signal at each probe position.

[0057] For each probe position, the product of the frequency domain bandwidth difference and the peak frequency deviation degree is calculated as the frequency domain noise interference degree of each probe position.

[0058] When the interference degree of external environmental noise on the probe current signal is greater, the probe current signal has more frequency components in the frequency domain, the peak frequency offset and broadening phenomenon in the spectrum diagram is more prominent, the frequency domain bandwidth difference is greater, and the peak frequency deviation is greater.

[0059] At this point, the frequency domain noise interference degree of the probe current signal at each probe position of the probe can be obtained according to the above method.

[0060] The product of the time domain noise interference degree and the frequency domain noise interference degree corresponding to the probe current signal at each probe position is taken as the second product, and the second product of all probe positions is normalized to obtain the external noise interference degree of each probe position. The external noise interference degree acquisition flow chart is as follows: Figure 2 shown.

[0061] At this point, the degree of external interference at each probe position is obtained. The above method can be used to more accurately evaluate and quantify the external environmental noise interference to the probe at each position based on the signal characteristics of the probe current signal in the time domain and frequency domain of the external environmental noise at each probe position.

[0062] Step S3, performing two-dimensional surface fitting according to the external noise interference degree of the probe at each probe position and the actual power of the radio frequency unit, and obtaining the beam current calibration value of the medical cyclotron based on the fitting surface.

[0063] The degree of external noise interference at each probe position is obtained, and two-dimensional surface fitting is performed with the actual power of the RF unit and the real-time position of the probe as independent variables and the degree of external noise interference at each probe position as the dependent variable. Since two-dimensional surface fitting is a well-known technology, the specific acquisition process will not be described in detail.

[0064] When measuring the beam intensity of a medical cyclotron, the position of the probe and the power of the radio frequency unit are measured simultaneously, and then the value of the background noise is obtained by fitting the surface. The calibrated value of the beam intensity is obtained by subtracting the value of the background noise from the actual measured value of the beam intensity.

[0065] It should be noted that the above-mentioned sequence of the embodiments of the present application is only for description and does not represent the advantages and disadvantages of the embodiments. The above-mentioned specific embodiments of the present application are described. 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.

[0066] The various embodiments in the present application 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.

[0067] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Modifications to the technical solutions recorded in the aforementioned embodiments, or equivalent replacement of some of the technical features therein, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for calibrating the main radial probe signal of a medical cyclotron, characterized in that: The method comprises the following steps: Collecting probe current data of the main radial probe current signal at each probe position at each acquisition time, and constructing a probe current data sequence at each probe position; Based on the volatility and dispersion of each period of the probe current data sequence, the time domain amplitude fluctuation degree of each period of the probe current data sequence is obtained; based on the volatility and positive and negative changes of each period element in the probe current data sequence, the time domain baseline stability of each period is obtained; Based on the time domain amplitude fluctuation degree and the time domain baseline stability degree, the time domain noise interference degree of each probe position is obtained; The frequency domain bandwidth difference of each probe position is obtained based on the frequency domain characteristics of the probe current data sequence; the frequency domain noise interference degree of each probe position is obtained based on the frequency domain bandwidth difference and the difference between the frequency energy sequences between different cycles; The external noise interference degree is obtained based on the time domain noise interference degree and the frequency domain noise interference degree; and the main radial probe signal is calibrated based on the external noise interference degree.

2. A method for calibrating main radial probe signals for a medical cyclotron according to claim 1, characterized in that: The method for obtaining the time domain amplitude fluctuation degree is: A peak detection algorithm is used to obtain all the peaks and troughs in the probe current data sequence, and the corresponding amplitude values ​​of all the peaks and troughs in each cycle are respectively composed of a sequence in time sequence as the peak sequence and trough sequence of the probe current signal in each cycle; Calculate the approximate entropy of the probe current data sequence of each cycle; for each cycle, calculate the interquartile range of the peak sequence and the trough sequence respectively, and take the sum of the interquartile range of the peak sequence and the interquartile range of the trough sequence as the first quartile sum; The time domain amplitude fluctuation degree of each period is obtained based on the approximate entropy and the first quartile sum value, and the time domain amplitude fluctuation degree is positively correlated with the approximate entropy and the first quartile sum value respectively.

3. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 2, characterized in that: The method for obtaining the stability of the time domain baseline is: For the peak sequence and trough sequence of each period, the absolute value of the difference between each element with the same position in the peak sequence and the trough sequence is calculated as the first absolute value of the difference, and the Shannon entropy of all the first absolute values ​​of the difference is used as the baseline shift degree of each period; Based on the positive and negative changes of the elements in the probe current data sequence, the difference in the number of signal zero crossings in each cycle is obtained; The time domain baseline stability of each cycle is obtained based on the baseline offset degree and the difference in the number of signal zero crossings, and the time domain baseline stability is negatively correlated with the baseline offset degree and the difference in the number of signal zero crossings, respectively.

4. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 3, characterized in that: The method for obtaining the difference in the number of times the signal crosses zero is: For each probe current data in the probe current data sequence of each cycle, when the value of the probe current data is greater than zero and the value of the next adjacent probe current data is less than zero, or when the value of the probe point pair data is less than zero and the value of the next adjacent probe current data is greater than zero, the value of the signal zero crossing times of each cycle is added with the number 1; The sequence composed of the number of signal zero crossings of the probe current signal amplitude in all cycles before each cycle in the periodic time sequence is taken as the historical zero crossing sequence of each cycle; the cumulative result of the absolute value of the difference between the number of signal zero crossings of each cycle and each data in the corresponding historical zero crossing sequence is calculated as the difference in the number of signal zero crossings of each cycle.

5. A method for calibrating main radial probe signals for a medical cyclotron according to claim 1, characterized in that: The method for obtaining the time domain noise interference degree is: The time domain interference coefficient is the ratio of the time domain amplitude fluctuation degree to the time domain baseline stability degree; The accumulated result of the time domain interference coefficients of all the cycles of each probe position during the probe movement is taken as the time domain noise interference degree of the probe at each probe position.

6. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 1, characterized in that: The method for obtaining the frequency domain bandwidth difference is: Obtain a spectrum diagram of the probe current signal in each cycle; The sequence of the 3 db bandwidth of the envelope of the fundamental frequency signal of the spectrum diagram corresponding to all periods of the probe current signal obtained by the probe at each probe position is composed in a periodic time sequence as the bandwidth sequence of the probe current signal at each probe position; Based on the frequency components and bandwidth sequence in the spectrum diagram of the probe current signal, the frequency component number difference and the fundamental bandwidth steady-state factor of each probe position are obtained; The frequency domain bandwidth difference of the probe current signal at each probe position is determined according to the difference in the number of frequency components of the probe current signal at each probe position and the baseband bandwidth steady-state factor. The frequency domain bandwidth difference is positively correlated with the difference in the number of frequency components and negatively correlated with the baseband bandwidth steady-state factor.

7. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 6, characterized in that: The method for obtaining the frequency component number difference and the baseband bandwidth steady-state factor is: For the spectrum diagram of the probe current signal at each probe position, the absolute value of the difference between the number of frequency components of any two periods is calculated as the second absolute value of the difference, and the accumulated result of all the second absolute values ​​of the difference is taken as the difference in the number of frequency components of the probe current signal at each probe position; the variance of all elements in the bandwidth sequence of the probe at each probe position is taken as the fundamental bandwidth steady-state factor of the probe current signal at each probe position.

8. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 6, characterized in that: The method for obtaining the frequency domain noise interference degree is: For each probe position, a sequence consisting of the maximum energy values ​​of all signal envelopes of the spectrum diagram in each period in ascending order of frequency is taken as the frequency energy sequence of each period; the distance between the frequency energy sequences of any two periods is calculated as the first distance, and the sum of all the first distances is taken as the peak frequency deviation degree of the probe current signal at each probe position; the product of the frequency domain bandwidth difference and the peak frequency deviation degree is calculated as the frequency domain noise interference degree of each probe position.

9. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 1, characterized in that: The method for obtaining the degree of external noise interference is: The product of the time domain noise interference degree and the frequency domain noise interference degree corresponding to the probe current signal at each probe position is taken as the second product, and the second products of all probe positions are normalized to obtain the external noise interference degree of each probe position.

10. A method for calibrating main radial probe signals for a medical cyclotron as claimed in claim 1, characterized in that: The calibrating of the main radial probe signal based on the degree of external noise interference includes: Obtain the degree of external noise interference at each probe position, and perform two-dimensional surface fitting with the actual power of the radio frequency unit and the real-time position of the probe as independent variables and the degree of external noise interference at each probe position as the dependent variable; When measuring the beam intensity of a medical cyclotron, the external noise interference degree corresponding to the measured probe position and the power of the radio frequency unit in the fitting surface is used as the background noise value, and the difference between the actual measured value of the beam intensity and the background noise value is used as the calibration value of the beam intensity.

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