A method and system for radiation testing of a medical cyclotron

Abstract

The present application relates to the technical field of radiation measurement with ionization chamber, and particularly relates to a radiation test method and system for a medical cyclotron. The present application firstly analyzes the change characteristics of the output current curve under the condition of the change of the polarization voltage, evaluates the saturation voltage probability coefficient of the output current curve segment corresponding to the ideal polarization voltage, then combines the ionization interference factors such as the ionization chamber environment and the change of the beam intensity of the particle beam, evaluates the radiation confidence of each output current accurately reflecting the radiation intensity, then screens and corrects the to-be-corrected current, obtains the ideal output current correction curve, and further improves the radiation test accuracy of the medical cyclotron.

Description

Technical Field

[0001] This invention relates to the field of radiation measurement technology using ionization chambers, and specifically to a radiation testing method and system for medical cyclotrons. Background Technology

[0002] Medical cyclotrons are key equipment for producing radiopharmaceuticals required for PET / CT imaging. They accelerate charged particles to bombard a target material using magnetic and electric fields to produce radioactive substances. However, the process of accelerating charged particles to the target material generates a large amount of ionizing radiation that is harmful to the human body. Therefore, radiation testing of cyclotrons is of paramount importance.

[0003] In existing technologies, ionization chambers are commonly used to test the ionizing radiation of medical cyclotrons during operation. When the particle beam generated by the medical cyclotron enters the ionization chamber, it collides with gas molecules inside the chamber, generating a large number of ions. These ions move toward the electrodes to form an electric current, which can then be used to reflect the radiation intensity. However, during the testing process, factors such as unreasonable polarization voltage inside the ionization chamber, the diffusion rate of gas molecules, and the instability of the particle beam can all lead to unstable output current in the ionization chamber, resulting in low accuracy in radiation testing of medical cyclotrons. Summary of the Invention

[0004] To address the technical problem of low accuracy in radiation testing of medical cyclotrons in existing technologies, the present invention aims to provide a radiation testing method and system for medical cyclotrons, the specific technical solution of which is as follows:

[0005] This invention proposes a radiation testing method for medical cyclotrons, the method comprising:

[0006] Acquire the beam intensity curve of the medical cyclotron and the environmental parameter curve of the ionization chamber during the radiation test, and acquire the output current curve under the condition of polarization voltage change in the ionization chamber;

[0007] Based on the variation characteristics of the output current curve, the output current curve is segmented, and the saturation voltage probability coefficient of each current curve segment is obtained; at each acquisition time, based on the local fluctuation of the beam intensity in the beam intensity curve and the deviation of the environmental parameters in the environmental parameter curve from the preset environmental parameters, the ionization interference coefficient at each acquisition time is obtained; at each acquisition time, based on the saturation voltage probability coefficient and the ionization interference coefficient of the current curve segment to which the acquisition time belongs, the radiation confidence coefficient is obtained.

[0008] All currents to be corrected in the output current curve are obtained based on the radiation confidence coefficient; based on the radiation confidence coefficient at the acquisition time corresponding to each current to be corrected, and the radiation confidence coefficients at the acquisition time corresponding to other non-currents to be corrected in the local neighborhood, combined with the deviation of each current to be corrected relative to other non-currents to be corrected in the local neighborhood, the output current correction curve is obtained; the radiation intensity of the medical cyclotron is obtained based on the output current correction curve.

[0009] Furthermore, the method for obtaining the environmental parameter curve includes:

[0010] At each acquisition time, the product of the temperature and air pressure data in the ionization chamber is used as the environmental parameter; the environmental parameter is used as the data point at the corresponding acquisition time and mapped to the two-dimensional coordinate system; the data points at adjacent acquisition times are connected sequentially to fit the environmental parameter curve.

[0011] Furthermore, the method for obtaining the output current curve includes:

[0012] The polarization voltage of the ionization chamber increases uniformly and rapidly. The output current of the ionization chamber at each acquisition time is used as a data point and mapped to a two-dimensional coordinate system. The data points at adjacent acquisition times are connected sequentially to fit the output current curve.

[0013] Furthermore, the method for segmenting the output current curve includes:

[0014] In the output current curve, the absolute value of the difference between each output current and the adjacent previous output current is taken as the rate of change of each output current; the absolute value of the difference between the rate of change of each output current and the rate of change of the adjacent previous output current is taken as the abrupt change coefficient of the rate of change of each output current.

[0015] Sort all the mutation coefficients in descending order, and use the output current corresponding to a preset number of mutation coefficients before sorting as segmentation points; use the segmentation points to segment the output current curve to obtain all current curve segments.

[0016] Furthermore, the method for obtaining the saturation voltage probability coefficient includes:

[0017] Obtain the best-fit line for each current curve segment; calculate the deviation between the output current at each acquisition time in each current curve segment and the fitted output current at the same acquisition time in the corresponding best-fit line; and use the negative correlation mapping result of the sum of the deviations at all acquisition times as the linear coefficient of the corresponding current curve segment.

[0018] The negative correlation mapping result between the output current at the end point and the starting point of each current curve segment is used as the current stability coefficient of the corresponding current curve segment.

[0019] The normalized result of the product of the linear coefficient and the current stability coefficient is used as the saturation voltage probability coefficient for the corresponding current curve segment.

[0020] Furthermore, the method for obtaining the ionization interference coefficient includes:

[0021] The environmental parameters at the initial time in the environmental parameter curve are taken as preset environmental parameters; at each acquisition time, the absolute value of the difference between the environmental parameters in the environmental parameter curve and the preset environmental parameters is taken as the environmental interference coefficient at the corresponding acquisition time.

[0022] A local time domain is constructed with each acquisition moment as the center. Within the local time domain of each acquisition moment, the standard deviation of all beam intensities in the beam intensity curve is taken as the beam fluctuation parameter at the corresponding acquisition moment, and the mean of the beam fluctuation parameters at all acquisition moments is taken as the reference beam fluctuation parameter at the corresponding acquisition moment. At each acquisition moment, the absolute value of the difference between the beam fluctuation parameter and the reference beam fluctuation parameter is taken as the relative fluctuation parameter, and the product of the beam fluctuation parameter and the relative fluctuation parameter is taken as the beam interference coefficient at the corresponding acquisition moment.

[0023] At each acquisition time, the normalized result of the product of the environmental interference coefficient and the beam interference coefficient is used as the ionization interference coefficient at the corresponding acquisition time.

[0024] Furthermore, the method for obtaining the radiation confidence coefficient includes:

[0025] The negative correlation mapping result of the ionization interference coefficient at each acquisition time is used as the confidence weight; at each acquisition time, the saturation voltage probability coefficient of the current curve segment to which the acquisition time belongs is weighted using the confidence weight, and the normalized result of the weighted result is used as the radiation confidence coefficient of the corresponding acquisition time.

[0026] Furthermore, the method for obtaining the current to be corrected includes:

[0027] The output current at the acquisition time when the radiation confidence coefficient in the output current curve is less than a preset threshold is taken as the current to be corrected.

[0028] Furthermore, the method for obtaining the output current correction curve includes:

[0029] In the output current curve, a local neighborhood is constructed with each current to be corrected as the center; the product of the radiation confidence coefficient of each current to be corrected and the mean of the radiation confidence coefficients of all non-currents to be corrected in the local neighborhood is used as the correction weight; the difference between the mean of all non-currents to be corrected in the local neighborhood and each current to be corrected is used as the reference amplitude.

[0030] The reference amplitude is weighted using the correction weights, and the sum of the weighted result and the corresponding current to be corrected is used as the correction current for the current to be corrected; all currents to be corrected in the output current curve are modified to correction currents to obtain the output current correction curve.

[0031] The present invention also proposes a radiation testing system for a medical cyclotron, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the radiation testing method for a medical cyclotron.

[0032] The present invention has the following beneficial effects:

[0033] This invention first acquires the beam intensity curve of a medical cyclotron and the environmental parameter curve of the ionization chamber during radiation testing, and then acquires the output current curve under varying polarization voltage conditions in the ionization chamber, providing a basis for subsequent data analysis. Based on the variation characteristics of the output current curve, the output current curve is segmented, and the saturation voltage probability coefficient for each segment is obtained. The saturation voltage probability coefficient reflects the curve segment where the corresponding current curve segment corresponds to the output current at the ideal polarization voltage; the larger the saturation voltage probability coefficient, the more accurately the output current in the corresponding current curve segment reflects the radiation intensity. At each acquisition moment, based on the local fluctuations in beam intensity in the beam intensity curve and the deviation of environmental parameters in the environmental parameter curve relative to preset environmental parameters, the ionization interference coefficient at each acquisition moment is obtained. The ionization interference coefficient integrates environmental factors within the ionization chamber and the stability of the particle beam, assessing the impact of external interference on the output current of the ionization chamber. A smaller ionization interference coefficient indicates a higher probability that the output current accurately reflects the radiation intensity. At each acquisition time, a radiation confidence coefficient is obtained based on the saturation voltage probability coefficient and ionization interference coefficient of the current curve segment corresponding to that acquisition time. All currents to be corrected in the output current curve are obtained based on the radiation confidence coefficient. Based on the radiation confidence coefficient of each current to be corrected at the corresponding acquisition time, and the radiation confidence coefficients of other non-currents to be corrected within the local neighborhood at the corresponding acquisition times, combined with the deviation of each current to be corrected relative to other non-currents within the local neighborhood, an output current correction curve is obtained. The radiation intensity of the medical cyclotron is then obtained based on the output current correction curve. This invention analyzes the variation characteristics of the output current curve under varying polarization voltage, evaluates the saturation voltage probability coefficient of the output current curve segment corresponding to the ideal polarization voltage, and then, in conjunction with ionization interference factors such as the ionization chamber environment and changes in the beam current intensity of the particle beam, assesses the confidence level that each output current accurately reflects the radiation intensity. The current to be corrected is then screened and corrected, thereby improving the accuracy of radiation testing for medical cyclotrons. Attached Figure Description

[0034] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart illustrating a radiation testing method for a medical cyclotron accelerator, provided as an embodiment of the present invention;

[0036] Figure 2 This is a flowchart illustrating a method for obtaining the ionization interference coefficient according to an embodiment of the present invention. Detailed Implementation

[0037] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a radiation testing method and system for a medical cyclotron accelerator proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0038] Unless otherwise defined, 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 invention pertains.

[0039] The following description, in conjunction with the accompanying drawings, details a specific scheme for a radiation testing method and system for a medical cyclotron accelerator provided by the present invention.

[0040] Please see Figure 1 The diagram illustrates a flowchart of a radiation testing method for a medical cyclotron accelerator according to an embodiment of the present invention, specifically including:

[0041] Step S1: Obtain the beam intensity curve of the medical cyclotron and the environmental parameter curve of the ionization chamber during the radiation test, and obtain the output current curve under the condition of polarization voltage change in the ionization chamber.

[0042] In one embodiment of the present invention, a radiation testing platform for a medical cyclotron is first constructed. This platform mainly includes a medical cyclotron, an ionization chamber, and some acquisition and control devices. The medical cyclotron generates a high-energy particle beam, which is transmitted to the ionization chamber via a vacuum pipe or beam guiding device. The ionization chamber must be precisely positioned within the beam path to ensure that the particle beam from the medical cyclotron can be received for subsequent radiation intensity measurement. The acquisition devices include a beam intensity acquisition device and an environmental acquisition device, and the sampling frequency of all acquisition devices is set to once per second. The control device is an adjustable power supply used to adjust the polarization voltage of the ionization chamber.

[0043] Install a beam intensity acquisition device, such as an electron beam monitor, at the vacuum tube or beam guiding device to monitor the beam intensity at each acquisition time. Then, map the beam intensity at each acquisition time as the data point at the corresponding acquisition time to a two-dimensional coordinate system, connect the data points at adjacent acquisition times in sequence, and fit the beam intensity curve.

[0044] An environmental sensor is installed in the ionization chamber, such as a temperature sensor to collect temperature data at each acquisition time and a pressure sensor to collect pressure data at each acquisition time. Then, at each acquisition time, the product of the temperature data and the pressure data is used as an environmental parameter. The environmental parameter is then mapped to the corresponding data point at the acquisition time onto a two-dimensional coordinate system. The data points at adjacent acquisition times are connected sequentially to fit the environmental parameter curve.

[0045] Simultaneously, an adjustable power supply is used to control the change in polarization voltage. The polarization voltage of the ionization chamber increases uniformly and at a rate of 1V per second, starting from 0V. For example, the polarization voltage at the first acquisition moment is 0V, at the second acquisition moment it is 1V, at the third acquisition moment it is 2V, and so on. Then, the weak current signal of the ionization chamber is amplified and processed using the ionization chamber data acquisition system to obtain the output current. The output current of the ionization chamber at each acquisition moment is used as a data point and mapped to a two-dimensional coordinate system. The data points at adjacent acquisition moments are connected sequentially to fit the output current curve. The output current curve is the curve of output current change over time, and also the curve of output current change over polarization voltage, in order to evaluate the radiation confidence coefficient of the output current in subsequent tests.

[0046] It should be noted that the acquisition of beam current intensity, environmental parameters and output current are all existing technologies well known to those skilled in the art, and will not be described in detail here. In other embodiments, the implementer may also set other sampling frequencies, but must ensure that the sampling frequencies of all acquisition devices are consistent. The polarization voltage change adjustment scheme may also be set, and other types or quantities of environmental data may be acquired, such as incorporating humidity data into the acquisition of environmental parameters, which will not be described in detail here.

[0047] Step S2: Based on the changing characteristics of the output current curve, the output current curve is segmented, and the saturation voltage probability coefficient of each current curve segment is obtained; at each acquisition time, based on the local fluctuation of the beam intensity in the beam intensity curve and the deviation of the environmental parameters in the environmental parameter curve from the preset environmental parameters, the ionization interference coefficient at each acquisition time is obtained; at each acquisition time, based on the saturation voltage probability coefficient and the ionization interference coefficient of the current curve segment to which the acquisition time belongs, the radiation confidence coefficient is obtained.

[0048] In traditional testing, the polarization voltage is usually fixed. However, an inappropriate polarization voltage may lead to insufficient energy for the ionization chamber electrodes to adsorb positive and negative ions, or cause a large number of ions to accumulate on a single electrode side, thus affecting the stability of the ionization chamber. An appropriate polarization voltage can not only optimize ion collection efficiency, but also avoid oversaturation of the ionization chamber, so as to ensure the accuracy of the linear relationship between the output current and the radiation intensity.

[0049] Considering that the polarization voltage is constantly increasing and changing, in the initial stage of polarization voltage growth, due to the weak polarization electric field, some positive and negative ions recombine into molecules. As the polarization voltage continues to increase, positive and negative ions begin to be polarized by the electric field, the recombination phenomenon gradually decreases, and the output current begins to rise rapidly. When the polarization voltage increases to the ideal voltage range, the recombination phenomenon basically disappears, and the output current increases nearly linearly and slightly and remains relatively stable. When the polarization voltage continues to increase, the electric field force strengthens, and the electrons generated by the initial ionization gain sufficient kinetic energy. During the process of being attracted to the electrode, they collide with other gas molecules, causing other gas molecules to ionize, thereby generating more positive and negative ions, and the output current will increase significantly. When the polarization voltage increases further, since the speed of electrons is much greater than that of positive ions, a large number of positive ions accumulate, resulting in a reverse electric field. The output current no longer increases linearly and enters a nonlinear rising stage.

[0050] Based on this, the main characteristics of the output current curve change are: from rapid rise to linear stable rise, then back to rapid rise, and finally to nonlinear rise. Therefore, in this embodiment of the invention, the output current curve will be segmented according to the characteristics of the output current curve change, and then the saturation voltage probability coefficient of each current curve segment will be obtained. The saturation voltage probability coefficient reflects the curve segment of the corresponding current curve segment that corresponds to the ideal polarization voltage and the corresponding output current. The larger the saturation voltage probability coefficient, the more accurate the radiation intensity reflected by the output current in the corresponding current curve segment.

[0051] Preferably, in one embodiment of the present invention, considering that the output current changes differently and the corresponding rates of change are also different at different stages of polarization voltage change; and considering that the change can be evaluated based on the difference in output current at adjacent acquisition times, and thus the segmentation points between different change trends can be determined to segment the output current curve; based on this, the method for segmenting the output current curve includes:

[0052] In the output current curve, the absolute value of the difference between each output current and the adjacent previous output current is taken as the rate of change of each output current; the absolute value of the difference between the rate of change of each output current and the rate of change of the adjacent previous output current is taken as the abrupt change coefficient of the rate of change of each output current.

[0053] Sort all mutation coefficients in descending order, and use the output current corresponding to a preset number of mutation coefficients before sorting as segmentation points; use the segmentation points to segment the output current curve and obtain all current curve segments.

[0054] As an example, considering that the change in output current can be divided into four stages during the polarization voltage change process, the preset quantity is set to 3. The rate of change can reflect the trend of output current change between adjacent acquisition times, while the abrupt change coefficient reflects the difference between the trends of output current change between adjacent acquisition times. The larger the abrupt change coefficient, the greater the change trend of output current between adjacent acquisition times, and the more likely it is to be the boundary point between different stages. Then, the output current corresponding to the three largest abrupt change coefficients is selected, and the data points corresponding to the output current at the corresponding acquisition times are respectively used as three segmentation points to segment the output current curve, obtaining a total of four current curve segments.

[0055] In other embodiments, the implementer may also acquire a large number of output current curves, manually analyze them to segment the output current curves, and assign each segment a corresponding stage label to construct a training sample set to train a neural network model. By inputting the currently acquired output current curve into the trained neural network model, all current curve segments can be obtained. It should be noted that the training and application of neural network models are existing technologies and will not be elaborated here.

[0056] Preferably, in one embodiment of the present invention, considering that the output current in the current curve segment corresponding to the ideal polarization voltage usually has a special linear small-amplitude rising characteristic, the linear characteristic in each current curve segment can be evaluated first, and then its small-amplitude stability characteristic can be evaluated based on its rising amplitude. Furthermore, both can be combined to evaluate whether the current curve segment has a linear small-amplitude rising characteristic, thus determining the probability that it is a curve segment corresponding to the output current of the ideal polarization voltage. The method for obtaining the saturation voltage probability coefficient includes:

[0057] Obtain the best-fit line for each current curve segment; calculate the deviation between the output current at each acquisition time in each current curve segment and the fitted output current at the same acquisition time in the corresponding best-fit line; and use the negative correlation mapping result of the sum of the deviations at all acquisition times as the linear coefficient of the corresponding current curve segment.

[0058] The negative correlation mapping result between the output current difference between the end point and the start point of each current curve segment is used as the current stability coefficient of the corresponding current curve segment.

[0059] The normalized product of the linear coefficient and the current stability coefficient is used as the saturation voltage probability coefficient for the corresponding current curve segment.

[0060] As an example, the formula for calculating the saturation voltage probability coefficient is: Where i is the segment number of the current curve; The saturation voltage probability coefficient for the i-th current curve segment; x is the sequence number of the acquisition time. This represents the total number of acquisition times in the i-th current curve segment; The output current at the x-th acquisition time in the segment of the i-th current curve; The fitted output current at the x-th acquisition time is the best-fit straight line for segmenting the i-th current curve. It is a minimal positive parameter; The deviation between the output current at the x-th acquisition time in the segment of the i-th current curve and the fitted output current at the same acquisition time in the corresponding best-fit line; The linear coefficients for segmenting the i-th current curve; The difference between the output current corresponding to the end point and the start point in the i-th current curve segment; The current stability coefficient for the segment of the i-th current curve; This is the standard normalization function.

[0061] In the formula for calculating the saturation voltage probability coefficient, the sum of deviations is added to a minimum positive parameter and then inversely calculated to perform a negative correlation mapping adjustment logic. The smaller the sum of deviations, the closer the current curve segment is to the corresponding best-fit line, and the larger the linear coefficient. The minimum positive parameter is set to 0.001 to avoid the denominator being meaningless without affecting the calculation result. The current difference is inversely calculated to perform a negative correlation mapping adjustment logic. The smaller the current difference, the smaller and more stable the change in output current in the current curve segment. Finally, the product of the linear coefficient and the current stability coefficient is linearly normalized to obtain the saturation voltage probability coefficient.

[0062] It should be noted that the best-fit line for each current curve segment is fitted using the least squares method, which is an existing technology and will not be elaborated here. In each current curve segment, the current difference between the output current corresponding to the endpoint and the starting point cannot be 0, that is, the current stability coefficient will not make the denominator meaningless when performing the reciprocal operation.

[0063] Considering that changes in environmental parameters within the ionization chamber may alter the diffusion rate of gas molecules, thereby affecting ionization and leading to low reliability of the output current; and considering that unstable beam intensity of the particle beam emitted by the medical cyclotron may complicate the frequency and energy distribution of ionization collisions within the ionization chamber, causing fluctuations in the output current and making it difficult to assess radiation intensity, this embodiment of the invention obtains the ionization interference coefficient at each acquisition time based on local fluctuations in beam intensity in the beam intensity curve and deviations of environmental parameters from preset environmental parameters in the environmental parameter curve. The ionization interference coefficient integrates environmental factors within the ionization chamber and the stability of the particle beam, assessing the impact of external interference on the output current of the ionization chamber; the smaller the ionization interference coefficient, the higher the likelihood that the output current accurately reflects the radiation intensity.

[0064] Preferably, in one embodiment of the present invention, the method for obtaining the ionization interference coefficient includes:

[0065] Please see Figure 2 The flowchart illustrates a method for obtaining the ionization interference coefficient according to an embodiment of the present invention, specifically including:

[0066] Step S201: Use the environmental parameters at the initial time in the environmental parameter curve as the preset environmental parameters; at each acquisition time, use the absolute value of the difference between the environmental parameters in the environmental parameter curve and the preset environmental parameters as the environmental interference coefficient at the corresponding acquisition time.

[0067] In one embodiment of the present invention, at each acquisition time, the environmental changes are first assessed based on the absolute value of the difference between the environmental parameters and the preset environmental parameters at the initial time. The larger the absolute value of the difference, the greater the changes in temperature and pressure, which in turn leads to changes in the velocity of gas molecules. Therefore, the greater the possibility of environmental changes affecting ionization, the greater the environmental interference coefficient. The environmental interference coefficient initially reflects the degree of interference of the environment on ionization, so that the ionization interference coefficient can be evaluated in combination with the beam intensity of the particle beam.

[0068] It should be noted that the preset environmental parameters, i.e. the environmental parameters at the initial moment, refer to the environmental parameters under ideal test conditions, which are conducive to normal ionization behavior so as to obtain accurate output current. At the initial moment, the implementer needs to control the environmental parameters according to the actual gas type in the ionization chamber, which is already existing technology and will not be elaborated here.

[0069] Step S202: Construct a local time domain centered on each acquisition moment. Within the local time domain of each acquisition moment, use the standard deviation of all beam intensities in the beam intensity curve as the beam fluctuation parameter at the corresponding acquisition moment, and use the mean of the beam fluctuation parameters at all acquisition moments as the reference beam fluctuation parameter at the corresponding acquisition moment. At each acquisition moment, use the absolute value of the difference between the beam fluctuation parameter and the reference beam fluctuation parameter as the relative fluctuation parameter, and use the product of the beam fluctuation parameter and the relative fluctuation parameter as the beam interference coefficient at the corresponding acquisition moment.

[0070] As an example, firstly, taking each acquisition moment as the center, a preset first number of acquisition moments are acquired on both sides to construct a local time domain; for example, if the current acquisition moment is n and the preset first number is 8, then the constructed local time domain is {n-8, n-7, ..., n-1, n, n+1, ..., n+7, n+8}. The implementer can also set the preset number to construct the local time domain.

[0071] The formula for calculating the beam interference coefficient is: Where x is the sequence number of the acquisition time; is the beam interference coefficient at the x-th acquisition time in the beam intensity curve; The beam fluctuation parameter at the x-th acquisition time in the beam intensity curve; This refers to the reference beam fluctuation parameters at the x-th acquisition time in the beam intensity curve; This represents the relative fluctuation parameter at the x-th acquisition time in the beam intensity curve.

[0072] In the formula for calculating the beam interference coefficient, the larger the beam fluctuation parameter, the more severe the beam intensity fluctuation is in the local time domain. The reference beam fluctuation parameter reflects the average fluctuation level of the beam intensity at all acquisition times in the local time domain. If the beam fluctuation parameter deviates significantly from the average fluctuation level, it indicates that the beam intensity fluctuation at the corresponding acquisition time is relatively severe and deviates, and the relative fluctuation parameter is larger. The relative fluctuation parameter is then multiplied and fused with the beam fluctuation parameter to obtain the beam interference coefficient at the corresponding acquisition time.

[0073] Step S203: At each acquisition time, the normalized result of the product of the environmental interference coefficient and the beam interference coefficient is used as the ionization interference coefficient at the corresponding acquisition time.

[0074] As an example, the environmental interference coefficient and the beam interference coefficient at each acquisition time are multiplied and fused, and the product is linearly normalized to obtain the ionization interference coefficient at the corresponding acquisition time.

[0075] Since the output current in the current curve segment with a larger saturation voltage probability coefficient and the output current with less ionization interference reflects a higher confidence level of radiation intensity, this embodiment of the invention further obtains a radiation confidence coefficient based on the saturation voltage probability coefficient and ionization interference coefficient of the current curve segment to which the acquisition time belongs at each acquisition time.

[0076] Preferably, in one embodiment of the present invention, the method for obtaining the radiation confidence coefficient includes:

[0077] The negative correlation mapping result of the ionization interference coefficient at each acquisition time is used as the confidence weight; at each acquisition time, the saturation voltage probability coefficient of the current curve segment to which the acquisition time belongs is weighted using the confidence weight, and the normalized result of the weighted result is used as the radiation confidence coefficient of the corresponding acquisition time.

[0078] As an example, the ionization interference coefficient is specifically used as x in the exponential function exp(-x) with the natural constant e as the reciprocal, and the value of the exponential function is used as the confidence weight. Then, at each acquisition time, the product of the confidence weight and the saturation voltage probability coefficient of the current curve segment to which the acquisition time belongs is linearly normalized to obtain the radiation confidence coefficient at the corresponding acquisition time.

[0079] Step S3: Obtain all currents to be corrected in the output current curve based on the radiation confidence coefficient; obtain the output current correction curve based on the radiation confidence coefficient of each current to be corrected at the acquisition time, and the radiation confidence coefficients of other non-currents to be corrected in the local neighborhood at the acquisition time, combined with the deviation of each current to be corrected relative to other non-currents to be corrected in the local neighborhood; obtain the radiation intensity of the medical cyclotron based on the output current correction curve.

[0080] Considering that the higher the radiation confidence coefficient, the higher the confidence level of the radiation intensity reflected by the output current at the corresponding acquisition time, it is necessary to screen out the currents with lower confidence levels for correction in order to accurately assess the radiation intensity in the future.

[0081] In a preferred embodiment of the present invention, the output current at the acquisition time when the radiation confidence coefficient in the output current curve is less than a preset threshold is taken as the current to be corrected; wherein the preset threshold is set to 0.3, and the implementer may also set it himself.

[0082] Considering that the lower the radiation confidence coefficient at the acquisition time corresponding to each current to be corrected, the greater the correction adjustment range; and considering that when correcting each current to be corrected, other non-currents in its local neighborhood can be referenced for correction; therefore, in this embodiment of the invention, after obtaining all currents to be corrected in the output current curve, each current to be corrected will be corrected and adjusted according to the radiation confidence coefficient at the acquisition time corresponding to each current to be corrected, the radiation confidence coefficients at the acquisition time corresponding to other non-currents in the local neighborhood, and the deviation of each current to be corrected relative to other non-currents in the local neighborhood, in order to obtain the output current correction curve, thereby facilitating the subsequent evaluation of the radiation intensity of the medical cyclotron based on the output current correction curve.

[0083] Preferably, in one embodiment of the present invention, the method for obtaining the output current correction curve includes:

[0084] In the output current curve, a local neighborhood is constructed with each current to be corrected as the center; the product of the radiation confidence coefficient of each current to be corrected and the mean of the radiation confidence coefficients of all non-currents to be corrected in the local neighborhood is normalized, and the normalization result is used as the correction weight; the difference between the mean of all non-currents to be corrected in the local neighborhood and each current to be corrected is used as the reference amplitude.

[0085] The reference amplitude is weighted using correction weights, and the sum of the weighted result and the corresponding current to be corrected is used as the correction current for the current to be corrected. All current values ​​to be corrected in the output current curve are modified to the correction current to obtain the output current correction curve.

[0086] As an example, firstly, a local neighborhood is constructed by acquiring a preset second number of output currents on both sides of each current to be corrected as the center; where the preset second number is 30, the length of the constructed local neighborhood is 61. The implementer can also set the preset number to construct the local time domain. Since other currents to be corrected in the local neighborhood will affect the correction effect of the current to be corrected at the center, all non-currents to be corrected will be screened out in the local neighborhood.

[0087] The formula for calculating the corrected current is: Where r is the sequence number of the current to be corrected; Let be the correction current for the r-th current to be corrected; For standard normalized functions; Let be the radiation confidence coefficient of the r-th current to be corrected; Let be the mean of the radiation confidence coefficients of all non-currents in the local neighborhood of the r-th current to be corrected; Let r be the correction weight for the r-th current to be corrected; Let be the mean of all non-currents in the local neighborhood of the r-th current to be corrected; Let r be the r-th current to be corrected; The reference amplitude is the r-th current to be corrected.

[0088] In the formula for calculating the correction current, the lower the radiation confidence of the current to be corrected and the higher the radiation confidence of all non-currents to be corrected in the local neighborhood, the higher the corresponding correction weight. This also indicates that the reference value of all non-currents to be corrected in the local neighborhood for correcting the current to be corrected is higher. When the current to be corrected is lower than the average of other non-currents to be corrected in the local neighborhood, the current to be corrected should be increased. At this time, the reference amplitude is positive. Multiplying the correction weight by the reference amplitude and adding it to the current to be corrected yields the increased correction current. Conversely, when the current to be corrected is higher than the average of other non-currents to be corrected in the local neighborhood, the current to be corrected should be decreased. At this time, the reference amplitude is negative. Multiplying the correction weight by the reference amplitude and adding it to the current to be corrected yields the decreased correction current.

[0089] After obtaining the corrected current for each current to be corrected, the output current curve can be adjusted to obtain the output current correction curve. The output current correction curve is then used to evaluate the radiation intensity of the medical cyclotron, where the output current is proportional to the radiation intensity; the larger the output current, the greater the radiation intensity.

[0090] It should be noted that using the output current correction curve to evaluate the radiation intensity of medical cyclotrons is an existing technique well known to those skilled in the art, and will not be elaborated here.

[0091] The present invention also proposes a radiation testing system for a medical cyclotron, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the radiation testing method for a medical cyclotron described in steps S1-S3.

[0092] In summary, this invention first acquires the beam intensity curve, environmental parameter curve, and output current curve under varying polarization voltage conditions during radiation testing. It then segments the output current curve and obtains the saturation voltage probability coefficient for each segment. Next, it analyzes and obtains the ionization interference coefficient at each acquisition moment, and subsequently obtains the radiation confidence coefficient at each acquisition moment to filter out all currents to be corrected in the output current curve. Then, it adjusts the current to be corrected by combining all non-currents within the local neighborhood of each current to be corrected, obtaining the output current correction curve. Finally, it obtains the radiation intensity of the medical cyclotron based on the output current correction curve. This invention analyzes the variation characteristics of the output current curve under varying polarization voltage conditions, evaluates the saturation voltage probability coefficient of the output current curve segment corresponding to the ideal polarization voltage, and then, combined with ionization interference factors such as the ionization chamber environment and changes in the beam intensity of the particle beam, evaluates the confidence level that each output current accurately reflects the radiation intensity. Finally, it filters and corrects the currents to be corrected, thereby improving the accuracy of radiation testing of the medical cyclotron.

[0093] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0094] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A radiation testing method for a medical cyclotron, characterized by, The method comprises: Obtaining the beam intensity curve of the medical cyclotron in the radiation test process and the environmental parameter curve of the ionization chamber, and obtaining the output current curve under the polarization voltage variation of the ionization chamber; According to the variation characteristics of the output current curve, the output current curve is segmented, and the saturation voltage probability coefficient of each current curve segment is obtained; at each acquisition time, according to the local fluctuation variation of the beam intensity in the beam intensity curve and the deviation of the environmental parameter in the environmental parameter curve relative to the preset environmental parameter, the ionization interference coefficient at each acquisition time is obtained; at each acquisition time, according to the saturation voltage probability coefficient of the current curve segment to which the acquisition time belongs and the ionization interference coefficient, the radiation confidence coefficient is obtained; According to the radiation confidence coefficient, all the to-be-corrected currents in the output current curve are obtained; according to the radiation confidence coefficient at the acquisition time corresponding to each to-be-corrected current and the radiation confidence coefficient at the acquisition time corresponding to other non-to-be-corrected currents in the local neighborhood, and combining the deviation of each to-be-corrected current relative to other non-to-be-corrected currents in the local neighborhood, an output current correction curve is obtained; the radiation intensity of the medical cyclotron is obtained based on the output current correction curve; The method for obtaining the saturation voltage probability coefficient comprises: Obtaining the best fitting straight line of each current curve segment; calculating the deviation between the output current at each acquisition time in each current curve segment and the fitting output current at the same acquisition time corresponding to the best fitting straight line; the negative correlation mapping result of the sum of the deviations at all acquisition times is taken as the linear coefficient of the corresponding current curve segment; The negative correlation mapping result of the difference between the output currents corresponding to the end point and the starting point in each current curve segment is taken as the current smoothness coefficient of the corresponding current curve segment; The normalization result of the product of the linear coefficient and the current smoothness coefficient is taken as the saturation voltage probability coefficient of the corresponding current curve segment; The method for obtaining the ionization interference coefficient comprises: Taking the environmental parameter at the initial time in the environmental parameter curve as the preset environmental parameter; at each acquisition time, the absolute value of the difference between the environmental parameter in the environmental parameter curve and the preset environmental parameter is taken as the environmental interference coefficient at the corresponding acquisition time; A local time domain is constructed with each acquisition time as the center, in the local time domain at each acquisition time, the standard deviation of all beam intensities in the beam intensity curve is taken as the beam fluctuation parameter at the corresponding acquisition time, and the mean value of all beam fluctuation parameters at all acquisition times is taken as the reference beam fluctuation parameter at the corresponding acquisition time; at each acquisition time, the absolute value of the difference between the beam fluctuation parameter and the reference beam fluctuation parameter is taken as the relative fluctuation parameter, and the product of the beam fluctuation parameter and the relative fluctuation parameter is taken as the beam interference coefficient at the corresponding acquisition time; At each acquisition time, the normalized result of the product of the environmental interference coefficient and the beam interference coefficient is taken as the ionization interference coefficient at the corresponding acquisition time; The method for obtaining the radiation confidence coefficient comprises: Map the negative correlation of the ionization interference coefficient at each collection time as a confidence weight; at each collection time, use the confidence weight to weight the saturation voltage probability coefficient of the current curve segment to which the collection time belongs, and normalize the weighting result as the radiation confidence coefficient of the corresponding collection time; The method for obtaining the output current correction curve comprises: In the output current curve, a local neighborhood is constructed around each of the to-be-corrected currents; the product of the radiation confidence coefficient of each of the to-be-corrected currents and the mean of the radiation confidence coefficients of all non-to-be-corrected currents in the local neighborhood is taken as a correction weight; the difference between the mean of all non-to-be-corrected currents in the local neighborhood and each of the to-be-corrected currents is taken as a reference amplitude; The reference amplitude is weighted by using the correction weight, and the sum of the weighted result and the corresponding to-be-corrected current is taken as a corrected current of the to-be-corrected current; all the to-be-corrected currents in the output current curve are modified to the corrected currents, so that an output current correction curve is obtained.

2. A method for testing a medical cyclotron for radiation according to claim 1, wherein, The method for obtaining the environmental parameter curve comprises: At each collection time, the product of the temperature data and the pressure data in the ionization chamber is taken as an environmental parameter; the environmental parameter is mapped to a two-dimensional coordinate system as a data point at the corresponding collection time, and the data points at adjacent collection times are sequentially connected to fit an environmental parameter curve.

3. A method for testing a medical cyclotron for radiation according to claim 1, wherein, The method for obtaining the output current curve comprises: The output current of the ionization chamber at each collection time is mapped to a two-dimensional coordinate system as a data point, and the data points at adjacent collection times are sequentially connected to fit an output current curve.

4. The method of claim 1, wherein the method is used for a medical cyclotron. The method for segmenting the output current curve comprises: In the output current curve, the absolute value of the difference between each output current and the adjacent previous output current is taken as the change rate of each output current; the absolute value of the difference between the change rate of each output current and the change rate of the adjacent previous output current is taken as the mutation coefficient of the change rate of each output current; All the mutation coefficients are sorted in descending order, and the output currents corresponding to the top pre-set number of the mutation coefficients are taken as segmentation points; the output current curve is segmented by using the segmentation points to obtain all current curve segments.

5. The method of claim 1, wherein the method is used for a medical cyclotron. The method for obtaining the to-be-corrected current comprises: The output current at the collection time in the output current curve, at which the radiation confidence coefficient is less than a pre-set threshold, is taken as a to-be-corrected current.

6. A radiation testing system for a medical cyclotron, characterized by, The system comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the radiation test method for a medical cyclotron according to any one of claims 1-5 when executing the computer program.

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