A method for measuring amplitude and phase stability of medical cyclotron

Abstract

The present application relates to the technical field of cyclotron accelerators, and specifically to a method for measuring the amplitude and phase stability of a medical cyclotron accelerator, the method comprising: obtaining the high-frequency voltage of the high-frequency resonant cavity at each moment in each monitoring cycle during the operation of the medical cyclotron accelerator, as well as the control frequency, control amplitude, and control phase of the high-frequency power source in each monitoring cycle; calculating the frequency deviation of each monitoring cycle; obtaining the main frequency interval to obtain the frequency estimation value and estimated phase of each monitoring cycle; determining the first evaluation value and the second evaluation value of each monitoring cycle; evaluating the amplitude and phase stability state of the medical cyclotron accelerator in each monitoring cycle, and judging the amplitude and phase stability of the medical cyclotron accelerator based on the amplitude and phase stability states of different monitoring cycles. The present application can comprehensively and accurately evaluate the amplitude and phase stability of the medical cyclotron accelerator, and improve the measurement credibility of the amplitude and phase stability of the medical cyclotron accelerator.

Description

Technical Field

[0001] The present application relates to the technical field of cyclotron accelerators, and in particular to a method for measuring the amplitude and phase stability of a medical cyclotron accelerator. Background Art

[0002] The medical small negative hydrogen cyclotron is a device specifically used to produce radioactive isotopes. Its core function is to use negatively charged hydrogen ions as accelerated particles, and it is widely used in the medical field. Its core principle is to use negatively charged hydrogen ions to bombard the target material after acceleration to produce specific radioactive nuclides. Among them, the stable operation of the medical cyclotron depends on the precise matching of the frequency of the electromagnetic waves generated by the high-frequency power source with the natural frequency of the high-frequency resonant cavity, forming a standing wave in the cavity of the high-frequency resonant cavity to efficiently store and transfer energy. However, in the actual operation of the medical cyclotron, due to the influence of factors such as thermal effects and mechanical vibrations, the natural frequency of the high-frequency resonant cavity will change, causing the natural frequency of the resonant cavity to shift. The automatic tuning system must monitor and adjust the frequency of the high-frequency power source in real time to maintain consistency between the two and ensure the stable operation of the accelerator.

[0003] However, when the automatic tuning system is tuned, it mainly relies on the ratio of reflected power to incident power to determine the degree of detuning. However, this method has a response lag when the high-frequency frequency changes, which will cause phase offset distortion and deviation error in the measured voltage amplitude. In addition, there is a lack of a dynamic compensation mechanism for phase changes, resulting in incomplete and inaccurate amplitude and phase stability assessment results, making the measurement of amplitude and phase stability of medical cyclotrons unreliable. Summary of the Invention

[0004] In order to solve the above technical problems, a method for measuring the amplitude and phase stability of a medical cyclotron is provided to solve the existing problems.

[0005] The solution to the technical problem of this application is to provide a method for measuring the amplitude and phase stability of a medical cyclotron, comprising the following steps:

[0006] Obtaining the high-frequency voltage of the high-frequency resonant cavity at each moment in each monitoring cycle during the operation of the medical cyclotron accelerator, as well as the control frequency, control amplitude and control phase of the high-frequency power source in each monitoring cycle;

[0007] Analyze the change trend of the control frequency in each monitoring cycle and the previous monitoring cycles, as well as the extreme changes, and calculate the frequency deviation of each monitoring cycle;

[0008] The main frequency range of the high-frequency voltage amplitude distribution in the frequency domain within each detection cycle is used to obtain the main frequency interval. Based on the frequencies corresponding to the left and right endpoints in the main frequency interval and the frequency offset, the frequency estimation value of each monitoring cycle is obtained. The phase of the high-frequency voltage in each detection cycle at the frequency estimation value is extracted in the frequency domain to obtain the estimated phase of each monitoring cycle.

[0009] Analyze the difference between the estimated phase and the control phase in each monitoring period and the previous monitoring periods to determine a first evaluation value for each monitoring period;

[0010] Analyze the difference between the high-frequency voltage and the control amplitude in each monitoring period and the previous monitoring periods, and determine the second evaluation value of each monitoring period in combination with the frequency deviation;

[0011] The amplitude and phase stability of the medical cyclotron in each monitoring period is evaluated based on the first evaluation value and the second evaluation value, and the amplitude and phase stability of the medical cyclotron is determined according to the amplitude and phase stability in different monitoring periods.

[0012] Preferably, the calculating of the frequency deviation of each monitoring period includes:

[0013] Perform linear fitting on the control frequencies corresponding to each monitoring period and the previous monitoring periods, and calculate the slope of the fitting line;

[0014] Calculate the range of the control frequency corresponding to each monitoring period and the multiple monitoring periods before it, and perform negative mapping on the range;

[0015] The frequency offset is a normalized result of the ratio of the slope to the result of the negative mapping.

[0016] Preferably, the further acquisition process of the main frequency interval is:

[0017] Perform frequency domain analysis on the high-frequency voltage at all times within each monitoring cycle to obtain a spectrum diagram;

[0018] Performing curve fitting on the amplitudes of all frequency components in the spectrum, obtaining the maximum values ​​of all peaks on the fitting curve, and extending the curve toward both sides along the maximum value until the amplitudes on both sides drop to the frequency components corresponding to preset multiples of the maximum value, which are recorded as the left frequency and the right frequency;

[0019] The frequency range between the left frequency and the right frequency is determined as the main frequency interval.

[0020] Preferably, Frequency estimate for each monitoring period The calculation formula is: ,in, For the The left endpoint of the main frequency interval corresponding to the monitoring period, that is, the left frequency, For the The right endpoint of the main frequency interval corresponding to the monitoring period, that is, the right frequency, For the The frequency deviation of a monitoring period.

[0021] Preferably, obtaining the estimated phase of each monitoring cycle includes: performing frequency domain analysis on the high-frequency voltage at all times in each monitoring cycle to obtain a complex spectrum, and based on the complex spectrum, extracting the phase at the frequency estimation value as the estimated phase of each monitoring cycle.

[0022] Preferably, determining the first evaluation value of each monitoring period includes:

[0023] Calculating the difference between the estimated phase and the controlled phase in each monitoring period, and recording it as a phase difference;

[0024] The first evaluation value is an average of the phase differences in each monitoring period and a plurality of monitoring periods before the monitoring period.

[0025] Preferably, determining the second evaluation value of each monitoring period includes:

[0026] The difference between the maximum value of the high-frequency voltage at all times in each monitoring period and the control amplitude is recorded as the amplitude difference;

[0027] The ratio of the amplitude difference to the control amplitude is recorded as a relative ratio, and the average value of the squares of the relative ratios in each monitoring period and the previous monitoring periods is calculated;

[0028] The frequency deviation degree of each monitoring period is fused with the average value to obtain a second evaluation value of each monitoring period.

[0029] Preferably, the specific process of the fusion is: taking the product of the absolute value of the frequency deviation in each monitoring period and the average value as the second evaluation value of each monitoring period.

[0030] Preferably, the step of evaluating the amplitude and phase stability of the medical cyclotron in each monitoring cycle includes:

[0031] By collecting data from medical cyclotrons that have been operating normally and stably in historical periods, the first evaluation value and the second evaluation value of all historical periods are calculated, and the maximum value of the first evaluation value of all historical periods and the maximum value of the second evaluation value of all historical periods are recorded as the phase stability threshold and the amplitude stability threshold, respectively;

[0032] If the first evaluation value of each monitoring cycle is less than the phase stability threshold, and the second evaluation value is less than the amplitude stability threshold, the monitoring cycle is in an amplitude and phase stable state; otherwise, the monitoring cycle is in an amplitude and phase unstable state.

[0033] Preferably, the determining of the amplitude and phase stability of the medical cyclotron includes:

[0034] Counting the number of monitoring cycles in an amplitude and phase unstable state, and calculating the ratio of the number to the number of all monitoring cycles, which is recorded as the instability ratio;

[0035] If the instability ratio is greater than a preset ratio, then the amplitude and phase stability of the medical cyclotron is abnormal; otherwise, the amplitude and phase stability of the medical cyclotron is normal.

[0036] This application has at least the following beneficial effects:

[0037] The present application calculates the frequency deviation of each monitoring cycle through the changes in the control frequency and the extreme change range of the high-frequency power source under multiple monitoring cycles. The beneficial effect of this application is that it takes into account the changing trend of the frequency of the high-frequency power source when the automatic tuning system adjusts the frequency in real time to reflect the frequency offset of the high-frequency resonant cavity, and then explains the possibility of amplitude and phase instability of the voltage under this monitoring cycle; and then obtains the main frequency interval, obtains the frequency estimation value of each monitoring cycle, and obtains the estimated phase of each monitoring cycle. The beneficial effect of this application is that the frequency of the high-frequency resonant cavity is estimated by the distribution range of the main frequency of the high-frequency voltage, combined with the frequency offset, so as to determine the actual operating frequency, and then determine the phase under the actual working conditions, thereby improving the accuracy of phase extraction during the tuning process of the automatic tuning system, so as to enhance the credibility of subsequent amplitude and phase stability measurements; determining the first evaluation value of each monitoring cycle, and the beneficial effect of this application is that The deviation between the estimated phase and the controlled phase in multiple monitoring cycles is taken into account to evaluate the phase stability of each monitoring cycle; the second evaluation value of each monitoring cycle is determined, which has the beneficial effect of taking into account the amplitude and phase instability of the voltage caused by the degree of adjustment of the high-frequency power source voltage by the automatic tuning system of the medical cyclotron in the monitoring cycle with a large frequency offset, as well as the deviation between the high-frequency voltage and the control amplitude, to evaluate the amplitude stability of each monitoring cycle; the amplitude and phase stability of the medical cyclotron is evaluated in each monitoring cycle, and the amplitude and phase stability of the medical cyclotron is judged according to the amplitude and phase stability status of different monitoring cycles. The beneficial effect is that the amplitude and phase stability of the medical cyclotron is evaluated through the amplitude and phase stability status of each monitoring cycle, which can comprehensively and accurately evaluate the amplitude and phase stability of the medical cyclotron, thereby improving the measurement credibility of the amplitude and phase stability of the medical cyclotron. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The following is a detailed description of a method for measuring amplitude and phase stability of a medical cyclotron according to the present application in conjunction with the accompanying drawings.

[0039] Figure 1 A flowchart of the steps of a method for measuring the amplitude and phase stability of a medical cyclotron provided in an embodiment of the present application;

[0040] Figure 2 A flowchart of the steps of the method for obtaining the first evaluation value provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of this application more clearly understood, the following, in conjunction with the accompanying drawings and implementation examples, further describes in detail a method for measuring amplitude and phase stability of a medical cyclotron proposed in this application. It should be understood that the specific embodiments described herein are merely intended to explain this application and are not intended to limit this application.

[0042] 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.

[0043] See also Figure 1 , which shows a flowchart of a method for measuring amplitude and phase stability of a medical cyclotron provided by one embodiment of the present application, the method comprising the following steps:

[0044] Step 1: Obtain the high-frequency voltage of the high-frequency resonant cavity at each moment in each monitoring cycle during the operation of the medical cyclotron, as well as the control frequency, control amplitude and control phase of the high-frequency power source in each monitoring cycle.

[0045] Medical cyclotrons are used to generate high-energy particle beams for radiotherapy or isotope production. Their core component is a high-frequency resonant cavity, which accelerates charged particles using a high-frequency electric field. If the voltage amplitude is unstable, the energy acquired by particles during each acceleration interval will be inconsistent, increasing the energy dispersion of the particle beam, affecting the acceleration effect and even preventing some particles from reaching the required energy level. Furthermore, particle acceleration depends on the phase matching of the high-frequency electric field and the phase of the particle motion. Phase instability can cause the phase relationship between the particles and the electric field to deviate during acceleration, thus affecting acceleration efficiency. Furthermore, fluctuations in amplitude or phase can cause lateral and longitudinal instabilities in the particle beam, leading to increased beam divergence. This beam divergence can expand the distribution of particles upon impacting the target, affecting the uniformity and accuracy of the generated radiation dose distribution. Therefore, to ensure the efficiency, stability, and safety of the particle acceleration process, the amplitude and phase stability of the high-frequency system must be maintained.

[0046] Therefore, when the medical cyclotron is running, the high-frequency voltage of the high-frequency resonant cavity is collected in real time through a high-precision voltage sensor; wherein, the sampling frequency of the voltage sensor is 20 MHz. As other implementation methods, the implementer can set it according to actual conditions.

[0047] Thus, after filtering the collected high-frequency voltage, the high-frequency voltage at each moment is obtained; multiple moments are recorded as a monitoring cycle, and the high-frequency voltage at each moment in each monitoring cycle is obtained;

[0048] In this embodiment, a low-pass filter is used for filtering to remove the interference of high-frequency noise components. The low-pass filter is a well-known technology and will not be described in detail here. Secondly, the duration of a monitoring cycle is 100ms. As other implementation methods, the implementer can set it according to actual conditions.

[0049] Secondly, in medical cyclotron accelerators, the high-frequency power source is a key component that drives the high-frequency resonant cavity and is responsible for generating a high-frequency electromagnetic field to accelerate charged particles. Due to the high-frequency resonant cavity heating up due to long-term operation, the inherent resonant frequency of the high-frequency resonant cavity changes, and the frequency of the high-frequency resonant cavity shifts, causing the operating frequency of the high-frequency power source to mismatch the frequency of the high-frequency resonant cavity, breaking the resonant state, reducing the power fed into the high-frequency resonant cavity, and reducing the beam intensity, making it impossible to effectively exert the performance of the accelerator. Therefore, to ensure the stable operation of the medical cyclotron accelerator, an automatic tuning system is present in the medical cyclotron accelerator. By monitoring the frequency deviation in real time, it dynamically adjusts the operating frequency of the high-frequency power source to ensure that the operating frequency of the high-frequency power source is consistent with the frequency of the high-frequency resonant cavity, thereby maintaining efficient energy transfer and stable beam acceleration.

[0050] Therefore, the control frequency, control amplitude and control phase of the high-frequency power source at the beginning of each monitoring period are monitored in real time by the automatic tuning system in the medical cyclotron.

[0051] Thus, the high-frequency voltage at each moment in each monitoring cycle during the operation of the medical cyclotron is obtained, as well as the control frequency, control amplitude and control phase of each monitoring cycle.

[0052] Step 2: Analyze the change trend of the control frequency in each monitoring period and the previous monitoring periods, as well as the extreme change conditions, and calculate the frequency deviation of each monitoring period.

[0053] Taking into account that the frequency change direction of the high-frequency resonant cavity caused by factors such as thermal effects and mechanical vibrations is relatively random during the operation of the medical cyclotron, but the degree of change of factors such as thermal effects and mechanical vibrations is small in a short period of time, and the impact on the frequency of the high-frequency resonant cavity is small. Therefore, the tuning characteristics of the high-frequency power source are evaluated by the changes in the control frequency of the high-frequency power source under multiple monitoring cycles, indicating the frequency offset of the high-frequency resonant cavity, and then reflecting the amplitude and phase instability of the voltage in the medical cyclotron.

[0054] Based on the above analysis, the frequency deviation is calculated by analyzing the change trend and extreme change range of the control frequency in each monitoring period and the previous monitoring periods. Specifically,

[0055] Perform linear fitting on the control frequencies corresponding to each monitoring period and the previous monitoring periods, and calculate the slope of the fitting line;

[0056] In this embodiment, linear fitting is performed on the control frequencies corresponding to each monitoring cycle and the 100 monitoring cycles before it. As other implementation methods, the implementer can set them according to actual conditions. Secondly, the least squares method is used for linear fitting, wherein the least squares method and the calculation of the slope are both well-known technologies and will not be described in detail here.

[0057] Calculate the range of control frequencies corresponding to each monitoring period and the previous monitoring periods;

[0058] In this embodiment, the range of the control frequencies corresponding to each monitoring period and the 100 monitoring periods before it is calculated.

[0059] Performing negative mapping on the range, and normalizing the ratio of the slope to the negative mapping result as the frequency deviation of each monitoring period;

[0060] In this embodiment, the specific process of negative mapping is: negative mapping is performed through an exponential function, assuming that the range is recorded as ,Will The result of negative mapping is as follows, where is an exponential function with a natural constant as the base; secondly, the inverse tangent normalization function is used for normalization, so that the frequency offset range is , wherein the arctangent normalization function is a well-known technology and will not be described in detail here.

[0061] It should be noted that, by using an exponential function to negatively map the range, when the range is small, the slope change is used as the main factor to evaluate the offset, and when the range is large, the severity of the change in the control frequency of the high-frequency power source is increased; when the frequency offset is a positive number, it indicates that the control frequency of the high-frequency power source has an upward trend, and when the frequency offset is a negative number, it indicates that the control frequency of the high-frequency power source has a downward trend. Therefore, the larger the absolute value of the obtained frequency offset, the more significant the fluctuation of the control frequency output by the high-frequency power source, the greater the degree of adjustment of the high-frequency power source voltage by the automatic tuning system of the medical cyclotron, and the more significant the frequency offset of the high-frequency resonant cavity, and the greater the probability of amplitude and phase instability of the voltage during the monitoring period.

[0062] At this point, the frequency deviation of each monitoring period is obtained.

[0063] Step 3: Obtain the main frequency interval through the main frequency range of the amplitude distribution of the high-frequency voltage in the frequency domain within each detection cycle, and obtain the frequency estimation value of each monitoring cycle based on the frequencies corresponding to the left and right endpoints in the main frequency interval and the frequency offset; extract the phase at the frequency estimation value from the frequency domain of the high-frequency voltage within each detection cycle to obtain the estimated phase of each monitoring cycle.

[0064] Furthermore, in medical cyclotron accelerators, particle acceleration depends on the phase matching of the high-frequency electric field in the high-frequency resonant cavity with the phase of the particle motion. Only when the particle enters the acceleration gap at the appropriate phase can effective energy acceleration be achieved. The accuracy of the phase measurement directly affects the control of the acceleration process. By analyzing the distribution of the high-frequency voltage in the high-frequency resonant cavity in the frequency domain and combining the frequency offset to perform offset compensation, the frequency of the high-frequency resonant cavity is estimated, specifically:

[0065] Perform frequency domain analysis on the high-frequency voltage at all times within each monitoring cycle to obtain a spectrum diagram;

[0066] In this embodiment, fast Fourier transform is used to perform frequency domain analysis to obtain a spectrum diagram, wherein fast Fourier transform is a well-known technology and will not be described in detail here.

[0067] Performing curve fitting on the amplitudes of all frequency components in the spectrum graph, obtaining the maximum values ​​of all peaks on the fitting curve, extending along the maximum value to both sides until the amplitudes on both sides drop to the frequency components corresponding to preset multiples of the maximum value, which are recorded as left frequency and right frequency; and determining the frequency range between the left frequency and the right frequency as the main frequency interval;

[0068] In this embodiment, the least squares method is used for curve fitting, and the AMPD algorithm (Automatic multiscale-based peak detection) is used to obtain the peak, wherein the least squares method and the AMPD algorithm are both well-known technologies and are not described in detail here; the preset multiple is set to 0.707. In voltage signal processing, decibel (dB) is used to describe the relative change of the voltage signal, wherein 3dB corresponds to 0.707 times the amplitude change. When the amplitude drops to 0.707 times the maximum value, the corresponding power is halved. Therefore, the range of the main peak is usually defined by the amplitude drop to a certain proportion of the maximum value, and the 3dB point, that is, 0.707 times the maximum value, is a widely used reference standard in the voltage signal processing process.

[0069] It should be noted that the main frequency interval reflects the frequency range of the main peak distribution of the high-frequency voltage. Under ideal conditions, if the high-frequency voltage is a sine wave, the left frequency is equal to the right frequency in the spectrum, and the frequency component corresponding to the maximum value is equal to the average of the left frequency and the right frequency. Due to the change in the frequency of the high-frequency resonant cavity, the control frequency of the high-frequency power source is not adjusted in time, resulting in detuning of the two, causing the frequency of the high-frequency voltage to shift, making the left frequency unequal to the right frequency.

[0070] Therefore, the frequency estimate for each monitoring period is calculated as:

[0071]

[0072] in, For the Frequency estimate for a monitoring period, For the The left endpoint of the main frequency interval corresponding to the monitoring period, that is, the left frequency, For the The right endpoint of the main frequency interval corresponding to the monitoring period, that is, the right frequency, For the The frequency deviation of a monitoring period.

[0073] It should be noted that Indicates the center frequency corresponding to the main peak in the spectrum, reflecting the main frequency components of the high-frequency voltage in the spectrum. Represents the frequency offset compensation term, which is used to correct the error caused by frequency offset. When the frequency offset is negative, it means that the control frequency of the high-frequency power source is decreasing, and the negative offset needs to be compensated. Therefore, by increasing the compensation term, it is offset toward the high frequency direction. When the frequency offset is positive, it means that the control frequency of the high-frequency power source is increasing, and the positive offset needs to be compensated. Therefore, by reducing the compensation term, it is offset toward the low frequency direction, thereby obtaining the true operating frequency.

[0074] Then, based on the frequency estimation value, the phase of the high-frequency voltage is extracted, specifically:

[0075] Performing frequency domain analysis on the high-frequency voltage at all times within each monitoring period to obtain a complex spectrum, and extracting the phase at the frequency estimate value based on the complex spectrum as the estimated phase for each monitoring period;

[0076] In this embodiment, fast Fourier transform is used for frequency domain analysis, wherein fast Fourier transform is a well-known technology and will not be described in detail here. Secondly, the real part and imaginary part are obtained by the complex form of the complex spectrum at the frequency estimate value, and the phase is calculated, wherein the process of extracting the phase at the frequency estimate value is a well-known technology and will not be described in detail here.

[0077] It should be noted that the estimated phase extracted by the frequency estimation value is closer to the actual working condition of the medical cyclotron, so as to more accurately evaluate the amplitude and phase stability of the medical cyclotron in the future.

[0078] At this point, the estimated phase of each monitoring period is obtained.

[0079] Step 4: Analyze the difference between the estimated phase and the control phase in each monitoring cycle and the multiple monitoring cycles before it, and determine the first evaluation value of each monitoring cycle; analyze the difference between the high-frequency voltage and the control amplitude in each monitoring cycle and the multiple monitoring cycles before it, and determine the second evaluation value of each monitoring cycle in combination with the frequency offset; based on the first evaluation value and the second evaluation value, evaluate the amplitude and phase stability of the medical cyclotron in each monitoring cycle, and judge the amplitude and phase stability of the medical cyclotron according to the amplitude and phase stability of different monitoring cycles.

[0080] Furthermore, a first evaluation value is calculated based on the deviation between the estimated phase and the controlled phase to evaluate the stability of the phase in different monitoring cycles during the operation of the medical cyclotron, specifically:

[0081] Calculating the difference between the estimated phase and the controlled phase in each monitoring period, and recording it as a phase difference;

[0082] In this embodiment, the absolute value of the difference between the estimated phase and the controlled phase is recorded as the phase difference.

[0083] Taking the average of the phase differences in each monitoring period and the previous monitoring periods as the first evaluation value of each monitoring period;

[0084] In this embodiment, the average of the phase differences in each monitoring period and the 100 monitoring periods before it is used as the first evaluation value of each monitoring period.

[0085] It should be noted that the larger the phase difference, the greater the deviation between the estimated phase and the controlled phase in the monitoring period, and the larger the first evaluation value, the worse the phase stability in the monitoring period during the operation of the medical cyclotron. The flowchart of the step of the method for obtaining the first evaluation value provided in the embodiment of the present application is as follows: Figure 2 shown.

[0086] During the operation of a medical cyclotron, the automatic tuning system is more likely to experience voltage amplitude control instability during the tuning process. Therefore, the difference between the maximum value of the high-frequency voltage and the control amplitude is combined with the frequency offset to calculate a second evaluation value to evaluate the stability of the voltage amplitude in different monitoring periods during the operation of the medical cyclotron. Specifically, the second evaluation value is:

[0087] The difference between the maximum value of the high-frequency voltage at all times in each monitoring period and the control amplitude is recorded as the amplitude difference;

[0088] In this embodiment, the absolute value of the difference between the maximum value of the high-frequency voltage at all times in each monitoring period and the control amplitude is recorded as the amplitude difference.

[0089] The ratio of the amplitude difference to the control amplitude is recorded as a relative ratio, and the average value of the squares of the relative ratios for each monitoring period and the multiple monitoring periods before it is calculated; the product of the absolute value of the frequency deviation in each monitoring period and the average value is used as the second evaluation value for each monitoring period;

[0090] In this embodiment, the average value of the square of the relative ratio of each monitoring period and the 100 monitoring periods before it is calculated.

[0091] It should be noted that, the larger the amplitude difference, the larger the relative contrast obtained, indicating that the greater the deviation between the maximum amplitude of the high-frequency voltage in the monitoring period and the control amplitude, the larger the absolute value of the obtained frequency offset, indicating that the monitoring period is in a period in which the automatic tuning system of the medical cyclotron adjusts the high-frequency power source voltage to a greater extent, and the greater the probability that the voltage has amplitude and phase instability problems in the monitoring period, and the larger the second evaluation value, indicating that the voltage amplitude stability in the monitoring period during the operation of the medical cyclotron is relatively low.

[0092] Furthermore, based on the first evaluation value and the second evaluation value, the amplitude and phase stability of the medical cyclotron in each monitoring cycle is evaluated, specifically:

[0093] By collecting data from medical cyclotrons that have been operating normally and stably in historical periods, the first evaluation value and the second evaluation value of all historical periods are calculated, and the maximum value of the first evaluation value of all historical periods and the maximum value of the second evaluation value of all historical periods are recorded as the phase stability threshold and the amplitude stability threshold, respectively;

[0094] In this embodiment, when the medical cyclotron is operating normally and stably during the historical period, the maximum value of the first evaluation value of 10,000 historical cycles and the maximum value of the second evaluation value of all historical cycles are selected and recorded as the phase stability threshold and the amplitude stability threshold. As other implementation methods, the implementer can set them according to actual conditions.

[0095] It should be noted that the phase stability threshold and the amplitude stability threshold reflect that the first evaluation value and the second evaluation value of the medical cyclotron in the historical period are respectively below the phase stability threshold and the amplitude stability threshold, both indicating that the medical cyclotron is in an amplitude and phase stable state.

[0096] If the first evaluation value of each monitoring period is less than the phase stability threshold, and the second evaluation value is less than the amplitude stability threshold, then the monitoring period is in an amplitude-phase stable state; otherwise, the monitoring period is in an amplitude-phase unstable state;

[0097] Counting the number of monitoring cycles in an amplitude and phase unstable state, and calculating the ratio of the number to the number of all monitoring cycles, which is recorded as the instability ratio;

[0098] If the instability ratio is greater than a preset ratio, then the amplitude and phase stability of the medical cyclotron is abnormal; otherwise, the amplitude and phase stability of the medical cyclotron is normal;

[0099] In this embodiment, the preset ratio is 0.1. For other implementations, the implementer may set it according to actual conditions.

[0100] It should be understood that although Figure 1The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. In addition, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0101] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the present application. It should be noted that a person skilled in the art can make various modifications and improvements without departing from the spirit of the present application. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments made in accordance with the technical essence of the present application without departing from the content of the present application's technical solution fall within the scope of protection of the present application's technical solution.

Claims

1. A method for measuring the amplitude and phase stability of a medical cyclotron, characterized in that: The method comprises the following steps: Obtaining the high-frequency voltage of the high-frequency resonant cavity at each moment in each monitoring cycle during the operation of the medical cyclotron accelerator, as well as the control frequency, control amplitude and control phase of the high-frequency power source in each monitoring cycle; Analyze the change trend of the control frequency in each monitoring cycle and the previous monitoring cycles, as well as the extreme changes, and calculate the frequency deviation of each monitoring cycle; The main frequency range of the high-frequency voltage amplitude distribution in the frequency domain within each detection cycle is used to obtain the main frequency interval. Based on the frequencies corresponding to the left and right endpoints in the main frequency interval and the frequency offset, the frequency estimation value of each monitoring cycle is obtained. The phase of the high-frequency voltage in each detection cycle at the frequency estimation value is extracted in the frequency domain to obtain the estimated phase of each monitoring cycle. Analyze the difference between the estimated phase and the control phase in each monitoring period and the previous monitoring periods to determine a first evaluation value for each monitoring period; Analyze the difference between the high-frequency voltage and the control amplitude in each monitoring period and the previous monitoring periods, and determine the second evaluation value of each monitoring period in combination with the frequency deviation; evaluating the amplitude and phase stability of the medical cyclotron in each monitoring period based on the first evaluation value and the second evaluation value, and determining the amplitude and phase stability of the medical cyclotron according to the amplitude and phase stability in different monitoring periods; The calculating of the frequency deviation of each monitoring period includes: Perform linear fitting on the control frequencies corresponding to each monitoring period and the previous monitoring periods, and calculate the slope of the fitting line; Calculate the range of the control frequency corresponding to each monitoring period and the multiple monitoring periods before it, and perform negative mapping on the range; The frequency offset is a normalized result of the ratio of the slope to the result of the negative mapping; No. Frequency estimate for each monitoring period The calculation formula is: ,in, For the The left endpoint of the main frequency interval corresponding to the monitoring period, For the The right endpoint of the main frequency interval corresponding to the monitoring period, For the Frequency deviation of each monitoring period; Determining the second evaluation value of each monitoring period includes: The difference between the maximum value of the high-frequency voltage at all times in each monitoring period and the control amplitude is recorded as the amplitude difference; The ratio of the amplitude difference to the control amplitude is recorded as a relative ratio, and the average value of the squares of the relative ratios in each monitoring period and the previous monitoring periods is calculated; The frequency deviation degree of each monitoring period and the average value of the square of the relative ratio are fused to obtain a second evaluation value of each monitoring period.

2. The method for measuring amplitude and phase stability of a medical cyclotron according to claim 1, wherein: The further acquisition process of the main frequency interval is as follows: Perform frequency domain analysis on the high-frequency voltage at all times within each monitoring cycle to obtain a spectrum diagram; Performing curve fitting on the amplitudes of all frequency components in the spectrum, obtaining the maximum values ​​of all peaks on the fitting curve, and extending the curve toward both sides along the maximum value until the amplitudes on both sides drop to the frequency components corresponding to preset multiples of the maximum value, which are recorded as the left frequency and the right frequency; The frequency range between the left frequency and the right frequency is determined as the main frequency interval.

3. The method for measuring amplitude and phase stability of a medical cyclotron according to claim 1, wherein: Obtaining the estimated phase of each monitoring cycle includes: performing frequency domain analysis on the high-frequency voltage at all times in each monitoring cycle to obtain a complex spectrum, and extracting the phase at the frequency estimation value based on the complex spectrum as the estimated phase of each monitoring cycle.

4. The method for measuring amplitude and phase stability of a medical cyclotron according to claim 1, wherein: Determining the first evaluation value of each monitoring period includes: Calculating the difference between the estimated phase and the controlled phase in each monitoring period, and recording it as a phase difference; The first evaluation value is an average of the phase differences in each monitoring period and a plurality of monitoring periods before the monitoring period.

5. The method for measuring amplitude and phase stability of a medical cyclotron according to claim 1, wherein: The specific process of the fusion is: taking the product of the absolute value of the frequency deviation in each monitoring period and the average value of the square of the relative ratio as the second evaluation value of each monitoring period.

6. The method for measuring amplitude and phase stability of a medical cyclotron according to claim 1, wherein: The evaluation of the amplitude and phase stability of the medical cyclotron in each monitoring cycle includes: By collecting data from medical cyclotrons that have been operating normally and stably in historical periods, the first evaluation value and the second evaluation value of all historical periods are calculated, and the maximum value of the first evaluation value of all historical periods and the maximum value of the second evaluation value of all historical periods are recorded as the phase stability threshold and the amplitude stability threshold, respectively; If the first evaluation value of each monitoring cycle is less than the phase stability threshold, and the second evaluation value is less than the amplitude stability threshold, the monitoring cycle is in an amplitude and phase stable state; otherwise, the monitoring cycle is in an amplitude and phase unstable state.

7. The method for measuring amplitude and phase stability of a medical cyclotron according to claim 6, wherein: The determining of the amplitude and phase stability of the medical cyclotron includes: Counting the number of monitoring cycles in an amplitude and phase unstable state, and calculating the ratio of the number to the number of all monitoring cycles, which is recorded as the instability ratio; If the instability ratio is greater than a preset ratio, then the amplitude and phase stability of the medical cyclotron is abnormal; otherwise, the amplitude and phase stability of the medical cyclotron is normal.

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