A calibration method for the magnetic measurement system of a medical cyclotron

Abstract

The present invention relates to the technical field of cyclotron calibration, and provides a calibration method for a magnetic measurement system of a medical cyclotron, including: collecting the radii of all detection coils of the medical cyclotron, as well as the magnetic induction intensity data and temperature data of all detection coils at different heights, to obtain a longitudinal magnetic induction intensity sequence and a transverse magnetic induction intensity sequence; obtaining the anomaly coefficient of the target detection coil, and determining the standard detection coil and the non-standard detection coil; constructing a temperature-magnetic relationship point set, determining the weight of each point in the temperature-magnetic relationship point set, and further determining the temperature-magnetic relationship curve; calibrating the magnetic induction intensity data of the non-standard detection coils at each height according to the temperature-magnetic relationship curve, so as to realize the calibration of the magnetic measurement system of the medical cyclotron. The purpose of the present invention is to solve the problem that the internal resistances of different detection coils in the detection coil disk are different and will change, resulting in deviation of the calibration result of the magnetic measurement system and poor performance of the medical cyclotron.

Description

Technical Field

[0001] The present invention relates to the technical field of cyclotron calibration, and particularly to a calibration method for the magnetic measurement system of a medical cyclotron. Background Art

[0002] A cyclotron is a device that uses magnetic and electric fields to make charged particles move in a circular motion and is repeatedly accelerated by a high-frequency electric field during the motion. In the field of modern medicine, a medical cyclotron can be used to accelerate charged particles to a high-energy state for cancer radiotherapy. A superconducting cyclotron provides a magnetic field through a room-temperature main magnet and superconducting coils. The magnetic field has a great impact on the final state of the particles. Therefore, during the process of using a medical cyclotron to accelerate charged particles, it is necessary to accurately control the magnetic field. Generally, the electromagnetic induction principle of a detection coil is used to measure and calibrate the magnetic field of the superconducting coil to reduce the errors of the magnetic measurement system and the detection coil.

[0003] In the prior art, the magnetic measurement system is generally calibrated according to the magnetic field strength changes of different detection coils in the detection coil disk. However, the resistances of different detection coils in the detection coil disk are different and will change. The different and changeable internal resistances of the detection coils will affect the magnetic field strength changes of the detection coils, resulting in deviations in the calibration results of the magnetic measurement system and affecting the performance of the medical cyclotron. Summary of the Invention

[0004] The present invention provides a calibration method for the magnetic measurement system of a medical cyclotron to solve the problem that the internal resistances of different detection coils in the detection coil disk are different and will change, which will affect the magnetic field strength changes of the detection coils, resulting in deviations in the calibration results of the magnetic measurement system and poor performance of the medical cyclotron. The specific technical solutions adopted are as follows:

[0005] An embodiment of the present invention provides a calibration method for the magnetic measurement system of a medical cyclotron, and the method includes the following steps:

[0006] Collect the radii of all different detection coils in the detection coil disk of the medical cyclotron, as well as the magnetic induction intensity data and temperature data of all detection coils at different heights in the detection coil disk, and obtain the longitudinal magnetic induction intensity sequence of the same detection coil and the transverse magnetic induction intensity sequence at the same height;

[0007] Denote any one detection coil in the detection coil disk as the target detection coil, obtain the abnormal coefficient of the target detection coil, and determine the standard detection coil and the non-standard detection coil according to the abnormal coefficients of all detection coils in the detection coil disk;

[0008] According to the relationship between the difference in the radii of the non-standard detection coil and the standard detection coil and the difference in the magnetic induction intensity data at the same height, and the relationship between the difference in the temperature data of the non-standard detection coil and the standard detection coil at the same height and the difference in the magnetic induction intensity data at the same height, obtain the second fitting curve at the same height. According to the difference in the magnetic induction intensity data corresponding to the same radius difference value of any two different second fitting curves, construct a temperature-magnetic relationship point set. According to the two different second fitting curves corresponding to each point in the temperature-magnetic relationship point set, and the difference in the temperature data of the non-standard detection coil corresponding to each point in the temperature-magnetic relationship point set at all heights, determine the weight of each point in the temperature-magnetic relationship point set. According to the weight of each point in the temperature-magnetic relationship point set, the temperature data of the non-standard detection coil and the standard detection coil, and the magnetic induction intensity data of the non-standard detection coil and the standard detection coil, obtain the temperature-magnetic relationship curve;

[0009] Calibrate the magnetic induction intensity data of the non-standard detection coil at each height according to the temperature-magnetic relationship curve, so as to realize the calibration of the magnetic measurement system of the medical cyclotron.

[0010] Furthermore, the specific method for obtaining the longitudinal magnetic induction intensity sequence of the same detection coil and the transverse magnetic induction intensity sequence at the same height includes:

[0011] Arrange all the magnetic induction intensity data of the same detection coil in the detection coil disk in ascending order of the height at which the magnetic induction intensity data is collected to obtain the longitudinal magnetic induction intensity sequence of the same detection coil;

[0012] Arrange the magnetic induction intensity data of all the detection coils collected at the same height in descending order of the radius of the detection coil to obtain the transverse magnetic induction intensity sequence at the same height.

[0013] Furthermore, the specific method for obtaining the anomaly coefficient of the target detection coil includes:

[0014] Taking the radii of all the detection coils in the detection coil disk as independent variables and the magnetic induction intensity data of each detection coil at the same height as dependent variables, use the polynomial curve fitting algorithm to obtain the first fitting curve at the same height; calculate the curvature of the points corresponding to the radii of all the detection coils in each first fitting curve respectively, and arrange the curvatures of all the calculated points of the first fitting curve at the same height in ascending order of the radius of the detection coil corresponding to the curvature to obtain the curvature sequence at the same height;

[0015] Denote any detection coil in the detection coil disk as the target detection coil, and denote the number of non-positive curvatures corresponding to the target detection coil in all the curvature sequences at the same height as the number of non-positive curvatures of the target detection coil;

[0016] Denote the variance of all data included in the first-order difference sequence of the curvature sequence at the same height as the first difference variance at the same height.

[0017] Delete the difference values calculated from the curvatures of the points corresponding to the radii of all target detection coils in the curvature difference sequence at the same height, and denote the variance of all remaining difference values in the curvature difference sequence at the same height as the second difference variance of the target detection coil at the same height.

[0018] Obtain the anomaly coefficient of each detection coil in the detection coil disk according to the number of non-positive curvatures of the detection coil, the first difference variance at the same height, the second difference variance at the same height, and the correlation between the longitudinal magnetic induction intensity sequences of all detection coils.

[0019] Furthermore, the specific method for obtaining the anomaly coefficient of each detection coil in the detection coil disk according to the number of non-positive curvatures of the detection coil, the first difference variance at the same height, the second difference variance at the same height, and the correlation between the longitudinal magnetic induction intensity sequences of all detection coils is as follows:

[0020]

[0021] In the formula, represents the anomaly coefficient of the th detection coil in the detection coil disk; represents the number of non-positive numbers included in the first-order difference sequence of the longitudinal magnetic induction intensity sequence of the th detection coil in the detection coil disk; represents the number of non-positive curvatures of the th detection coil in the detection coil disk; represents the mean value of all first difference variances at the same height; represents the mean value of all second difference variances at the same height of the th detection coil in the detection coil disk; represents a preset first parameter; represents the mean value of the absolute values of the correlation coefficients between the longitudinal magnetic induction intensity sequence of the th detection coil in the detection coil disk and the longitudinal magnetic induction intensity sequences of all other detection coils.

[0022] Furthermore, the specific method for determining the standard detection coil and the non-standard detection coil is as follows:

[0023] Denote the detection coil with the smallest anomaly coefficient as the standard detection coil, and denote the detection coils that are not the standard detection coil as non-standard detection coils.

[0024] Further, the specific method for obtaining the second fitting curve at the same height is as follows:

[0025] Taking the differences in temperature data between the non-standard detection coil and the standard detection coil at the same height in the detection coil disk, and the differences in radius between the non-standard detection coil and the standard detection coil as independent variables, and taking the difference in magnetic induction intensity data between the non-standard detection coil and the standard detection coil at the same height as the dependent variable, and using multiple nonlinear regression analysis to obtain the second fitting curve at the same height.

[0026] Further, the specific method for constructing the temperature-magnetic relationship point set is as follows:

[0027] Recording the function values calculated from the second fitting curves at all heights as the first intensity differences, and recording the difference in radius between the non-standard detection coil and the standard detection coil corresponding to the first intensity difference as the first radius difference of the first intensity difference;

[0028] Taking the difference between the first intensity differences corresponding to every two identical first radius differences in any two different second fitting curves as the ordinate, and taking the difference between the temperature data of the detection coils corresponding to every two identical first radius differences in any two different second fitting curves as the abscissa, establishing a plane rectangular coordinate system, marking the points corresponding to every two identical first radius differences in the plane rectangular coordinate system, and recording the set composed of all points in the plane rectangular coordinate system as the temperature-magnetic relationship point set.

[0029] Further, the specific method for obtaining the weight of each point in the temperature-magnetic relationship point set is as follows:

[0030] Calculating the goodness of fit of each second fitting curve;

[0031] The calculation formula for the weight of the points in the temperature-magnetic relationship point set is:

[0032]

[0033] In the formula, represents the weight of the th point in the temperature-magnetic relationship point set; represents the minimum value of the goodness of fit of the two different second fitting curves corresponding to the th point in the temperature-magnetic relationship point set; represents a preset second parameter; represents the temperature standard deviation of the non-standard detection coil corresponding to the th point in the temperature-magnetic relationship point set.

[0034] Further, the specific method for obtaining the temperature-magnetic relationship curve is as follows:

[0035] Taking the difference between the temperature data of the non-standard detection coil and the standard detection coil as the independent variable, taking the weight of the point as the weight of the independent variable corresponding to the non-standard detection coil corresponding to the point, and taking the difference between the magnetic induction intensity data of the non-standard detection coil and the standard detection coil as the dependent variable, performing weighted curve fitting to obtain the temperature-magnetic relationship curve.

[0036] Further, the method for calibrating the magnetic induction intensity data of the non-standard detection coil at each height according to the temperature-magnetic relationship curve specifically includes:

[0037] Directly multiplying or dividing the magnetic induction intensity data of the standard detection coil numerically to make the collected magnetic induction intensity data of the standard detection coil equal to the theoretical value of the magnetic induction intensity data of the standard detection coil at the same height, and obtaining the adjustment multiple for directly multiplying or dividing the magnetic induction intensity data of the standard detection coil numerically at each height; at each height, calibrating the magnetic induction intensity data of all non-standard detection coils using the adjustment multiple corresponding to the numerical multiplication or division at that height to obtain the calibrated magnetic induction intensity data of the non-standard detection coil at each height;

[0038] At each height, according to the difference in temperature data between the non-standard detection coil and the standard detection coil and the temperature-magnetic relationship curve, calculate the difference in magnetic induction intensity data between the non-standard detection coil and the standard detection coil at each height and record it as the first difference at each height, and take the sum of the first difference at each height and the calibrated magnetic induction intensity data of the non-standard detection coil at each height as the calibrated value of the magnetic induction intensity data of the non-standard detection coil at that height.

[0039] The beneficial effects of the present invention are:

[0040] First, according to the characteristics that the magnetic field generated by the detection coil closer to the center of the detection coil disk is stronger, and when the distance between the detection coil disk and the detection coil is closer, the magnetic induction intensity data collected by the detection coil is larger, this application evaluates the characteristics that the magnetic induction intensity data in the horizontal magnetic induction intensity sequence at the same height is monotonically increasing and the magnetic induction intensity data in the vertical magnetic induction intensity sequence of the same detection coil is monotonically increasing, and obtains the anomaly coefficient of each detection coil in the detection coil disk. The anomaly coefficient is an evaluation of the possibility of the detection coil being affected by the resistance on the magnetic induction intensity data. Then, according to the anomaly coefficients of all detection coils in the detection coil disk, the standard detection coil and the non-standard detection coil are determined. The standard detection coil is the detection coil in the detection coil disk that is closest to the ideal state.

[0041] Calibrate the non-standard detection coil using the standard detection coil as the calibration standard to avoid magnetic measurement errors caused by various factors and improve the accuracy of calibration. Specifically, according to the relationship between the difference in magnetic induction intensity data at the same height and the difference in the radii of the non-standard detection coil and the standard detection coil and the difference in temperature data at the same height, obtain the second fitting curve at the same height to eliminate the influence of height on the change in magnetic induction intensity of the detection coil. Then, according to the difference in magnetic induction intensity data corresponding to the same radius difference value of any two different second fitting curves, construct a temperature-magnetic relationship point set, which reflects the relationship between magnetic induction intensity data and temperature data, and eliminates the influence of height and the radius of the detection coil on the relationship between magnetic induction intensity data and temperature data.

[0042] Furthermore, through the process of quantitatively characterizing the weight of each point in the temperature-magnetic relationship point set, use the weight to reflect the corresponding relationship between temperature change and magnetic induction intensity change. Then, according to the weight of each point in the temperature-magnetic relationship point set, the temperature data of the non-standard detection coil and the standard detection coil, and the magnetic induction intensity data of the non-standard detection coil and the standard detection coil, obtain the temperature-magnetic relationship curve, making the relationship between more reliable magnetic induction intensity data and temperature data have a greater impact on the fitting curve, and making the obtained temperature-magnetic relationship curve more accurate. Finally, calibrate the magnetic induction intensity data of the non-standard detection coil at each height according to the temperature-magnetic relationship curve to achieve the calibration of the magnetic measurement system of the medical cyclotron. During the calibration process of the magnetic measurement system of the medical cyclotron, exclude the influence of the change in the internal resistance of different detection coils on the magnetic induction intensity data, and solve the problem that the internal resistances of different detection coils in the detection coil disk are different and will change, which will affect the change in the magnetic field intensity of the detection coil, resulting in deviation in the calibration result of the magnetic measurement system and poor performance of the medical cyclotron. Brief Description of the Drawings

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0044] Figure 1 Schematic flow chart of a method for calibrating a magnetic measurement system of a medical cyclotron provided by an embodiment of the present invention;

[0045] Figure 2 Flow chart for obtaining a standard detection coil and a non-standard detection coil provided by an embodiment of the present invention. Detailed Embodiments

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Please refer to Figure 1 , which shows a flowchart of a calibration method for a magnetic measurement system of a medical cyclotron provided by an embodiment of the present invention. The method includes the following steps:

[0048] Step S001: Collect the radii of all different detection coils in the detection coil disk of the medical cyclotron, as well as the magnetic induction intensity data and temperature data of all detection coils in the detection coil disk at different heights, and obtain the longitudinal magnetic induction intensity sequence of the same detection coil and the transverse magnetic induction intensity sequence at the same height.

[0049] Use a position encoder to measure the radius of each detection coil in the detection coil disk.

[0050] Fix a fiber optic temperature sensor on each detection coil in the detection coil disk, fix the detection coil disk on the calibration device for measuring the magnetic field of the cyclotron, and use a motor to control the detection coil disk to move vertically upward at a constant speed of 1 mm / s, so that the detection coil disk gradually approaches the energized electric coil disk. Take 1 second as the time interval, and use a fluxmeter to collect the magnetic induction intensity data of each detection coil in the detection coil disk during the movement of the detection coil disk. Take 1 second as the time interval, and use the fiber optic temperature sensor to collect the temperature data of each detection coil in the detection coil disk during the movement of the detection coil disk.

[0051] Since the magnetic field is generated by the energized electric coil disk, when the detection coil disk moves vertically upward at a constant speed, the distance between the detection coil disk and the energized electric coil disk becomes closer and closer.

[0052] Arrange all the magnetic induction intensity data of the same detection coil in the detection coil disk in ascending order of the height at which the magnetic induction intensity data is collected to obtain the longitudinal magnetic induction intensity sequence of the same detection coil.

[0053] Arrange the magnetic induction intensity data of all detection coils collected at the same height in descending order of the radius of the detection coil to obtain the transverse magnetic induction intensity sequence at the same height.

[0054] So far, the radii of all different detection coils in the detection coil disk, the longitudinal magnetic induction intensity sequence of the same detection coil, and the transverse magnetic induction intensity sequence at the same height are obtained.

[0055] Step S002: record any one detection coil in the detection coil disk as a target detection coil, obtain the abnormal coefficient of the target detection coil according to the radius of all detection coils in the detection coil disk, the magnetic induction intensity data of all detection coils at the same height, and the correlation between the longitudinal magnetic induction intensity sequences of all detection coils, and determine the standard detection coil and the non-standard detection coil according to the abnormal coefficients of all detection coils in the detection coil disk.

[0056] The closer the detection coil is to the center of the detection coil disk, the stronger the magnetic field generated is. Therefore, the magnetic induction intensity data collected by the detection coil closer to the center of the detection coil disk is larger. Therefore, the magnetic induction intensity data in the transverse magnetic induction intensity sequence at the same height should increase monotonically. When the distance between the detection coil disk and the detection coil is closer, the magnetic induction intensity data collected by the detection coil is larger. Therefore, the magnetic induction intensity data in the longitudinal magnetic induction intensity sequence of the same detection coil should also increase monotonically.

[0057] However, the internal resistance of different detection coils in the detection coil disk is different, which will cause the magnetic induction intensity data of different detection coils to be affected by different resistances, destroying the monotonically increasing characteristics of the magnetic induction intensity data in the transverse magnetic induction intensity sequence at the same height and the longitudinal magnetic induction intensity sequence of the same detection coil, affecting the magnetic measurement system corresponding to the detection coil disk, and causing errors in the measurement results of the magnetic measurement system corresponding to the detection coil disk. Therefore, it is necessary to correct the magnetic induction intensity data according to the internal resistance of different detection coils, so that the magnetic induction intensity data in the transverse magnetic induction intensity sequence at the same height and the longitudinal magnetic induction intensity sequence of the same detection coil maintain a monotonically increasing characteristic, and eliminate the measurement result errors of the magnetic measurement system corresponding to the detection coil disk.

[0058] It should be noted that the detection coil in the magnetic measurement system will produce changes in internal resistance due to the influence of various factors. If the internal resistance of all the detection coils in the detection coil disk is measured directly, the detection coil needs to be taken out and professional instruments need to be used to measure the resistance. However, the detection coil disk of the magnetic measurement system is not suitable for measuring resistance in this way. Therefore, considering the changes in the internal resistance of the detection coil in the magnetic measurement system, this application reflects the internal resistance of all the detection coils in the detection coil disk through temperature data based on the characteristic that the temperature of the detection coil is positively correlated with the resistance.

[0059] Any detection coil in the detection coil disk is marked as the target detection coil. According to the radius of all detection coils in the detection coil disk and the magnetic induction intensity data of each detection coil at the same height, the first differential variance at the same height, the number of non-positive curvatures of the target detection coil and the second differential variance of the target detection coil at the same height are obtained.

[0060] Taking the radii of all the detection coils in the detection coil disk as independent variables and the magnetic induction intensity data of each detection coil at the same height as the dependent variable, the polynomial curve fitting algorithm is used to obtain the fitting curve of the radius of the detection coil and the magnetic induction intensity data at the same height, and the obtained fitting curve is denoted as the first fitting curve at the same height.

[0061] It can be understood that in the process of the detection coil disk gradually approaching the energized electric coil disk, each acquisition moment corresponds to a height, and each height has a corresponding first fitting curve.

[0062] Calculate the curvature of the points corresponding to the radii of all the detection coils in each first fitting curve respectively, and arrange the curvatures of all the calculated points of the first fitting curve at the same height in ascending order of the radii of the detection coils corresponding to the curvatures, so as to obtain the curvature sequence at the same height.

[0063] Denote any one of the detection coils in the detection coil disk as the target detection coil. In this embodiment, any one of the detection coils is taken as an example for illustration.

[0064] Denote the number of non-positive curvatures corresponding to the target detection coil in the curvature sequences at all the same heights as the non-positive curvature number of the target detection coil.

[0065] Denote the first-order difference sequence of the curvature sequence at the same height as the curvature difference sequence at the same height, and denote the variance of all the data included in the curvature difference sequence at the same height as the first difference variance at the same height.

[0066] Delete the difference values calculated from the curvatures of the points corresponding to the radii of all the target detection coils in the curvature difference sequence at the same height, and denote the variance of all the remaining difference values in the curvature difference sequence at the same height as the second difference variance of the target detection coil at the same height.

[0067] According to the same method, the non-positive curvature number of any one of the detection coils in the detection coil disk and the second difference variance of any one of the detection coils in the detection coil disk at the same height can be obtained. That is to say, for any one of the detection coils in the detection coil disk, there is a corresponding non-positive curvature number. At the same time, for any one of the detection coils in the detection coil disk at each height, there is a corresponding second difference variance.

[0068] Among them, obtaining the fitting curve using the polynomial curve fitting algorithm, calculating the curvature of the points on the curve, and calculating the first-order difference sequence of the sequence are all well-known technologies and will not be elaborated here.

[0069] Obtain the anomaly coefficient of each detection coil in the detection coil disk according to the number of non-positive curvatures of the detection coil, the first-difference variance at the same height, the second-difference variance at the same height, and the correlation between the longitudinal magnetic induction intensity sequences of all detection coils.

[0070]

[0071] In the formula, represents the anomaly coefficient of the th detection coil in the detection coil disk; represents the number of non-positive numbers contained in the first-order difference sequence of the longitudinal magnetic induction intensity sequence of the th detection coil in the detection coil disk; represents the number of non-positive curvatures of the th detection coil in the detection coil disk; represents the mean value of the first-difference variances at the same height; represents the mean value of the second-difference variances at the same height of the th detection coil in the detection coil disk; represents a preset first parameter, whose function is to prevent from taking 0, which would directly make the value of the anomaly coefficient 0. In this embodiment, the value of the preset first parameter is 1; represents the mean value of the absolute values of the correlation coefficients between the longitudinal magnetic induction intensity sequence of the th detection coil in the detection coil disk and the longitudinal magnetic induction intensity sequences of all other detection coils.

[0072] In this embodiment, the Pearson correlation coefficient is used as the correlation coefficient of the longitudinal magnetic induction intensity sequence. As other implementation manners, on the basis of achieving the purpose of measuring the correlation between two sequences, implementers can use other methods in the prior art to obtain the correlation between two sequences, and this application does not make special restrictions.

[0073] is the monotonicity evaluation of the longitudinal magnetic induction intensity sequence of the th detection coil, is the monotonicity evaluation of the longitudinal magnetic induction intensity sequence of the th detection coil. When the longitudinal magnetic induction intensity sequences of the th detection coil and the longitudinal magnetic induction intensity sequence both fully conform to the characteristics of monotonically increasing, and both take the value of 0. At this time, the th detection coil is less likely to be affected by the resistance on the magnetic induction intensity data. Since the th detection coil generates less magnetic measurement error, the degree of calibration for the th detection coil should be smaller. When the When the monotonic increasing characteristic presented by the longitudinal magnetic induction intensity sequence of a detection coil and the longitudinal magnetic induction intensity sequence becomes less obvious, and the larger the value of, at this time, the larger the abnormal coefficient value of the th detection coil, the greater the difference between the resistance of the target detection coil and the resistance of other detection coils, and the greater the possibility that the th detection coil is affected by the resistance on the magnetic induction intensity data. Since the th detection coil generates a larger magnetic measurement error, the degree of calibration for the th detection coil should be greater.

[0074] is the stability evaluation of the curvature included in the curvature sequence at the same height, is the stability evaluation of all the curvatures included in the curvature sequence at the same height, excluding the curvature corresponding to the radius of the target detection coil. When is smaller, after excluding the curvature corresponding to the radius of the target detection coil, the difference in the results of the stability evaluation of all curvatures is smaller, then the curvature corresponding to the radius of the target detection coil has a smaller difference relative to other curvatures. Therefore, the difference between the resistance of the target detection coil and the resistance of other detection coils is larger, and the possibility that the target detection coil is affected by the resistance on the magnetic induction intensity data is smaller. Since the th detection coil generates a smaller magnetic measurement error, the degree of calibration for the th detection coil should be smaller. At this time, the abnormal coefficient value of the th detection coil is smaller.

[0075] When the absolute value of the correlation coefficient between the longitudinal magnetic induction intensity sequences of the target detection coil and different detection coils is larger, the correlation between the longitudinal magnetic induction intensity sequences is more significant. At this time, the difference between the resistance of the target detection coil and the resistance of other detection coils is smaller, and the abnormal coefficient of the target detection coil is smaller.

[0076] Thus, the abnormal coefficient of each detection coil in the detection coil disk is obtained.

[0077] The magnetic induction intensity of the detection coil is affected by various factors such as manufacturing process, resistance, and operating environment. The smaller the abnormal coefficient of the detection coil, the less it is affected by various factors. Therefore, it is considered that the detection coil with the smallest abnormal coefficient is the detection coil in the detection coil disk that is closest to the ideal state. Using the detection coil closest to the ideal state as the calibration standard can, to a certain extent, avoid the magnetic measurement error caused by various factors and improve the calibration accuracy.

[0078] The detection coil with the smallest anomaly coefficient is denoted as the standard detection coil, and the detection coils that are not the standard detection coil are denoted as non-standard detection coils. The non-standard detection coils are calibrated according to the standard detection coil.

[0079] Thus, the standard detection coil and the non-standard detection coils are determined. The flowchart for obtaining the standard detection coil and the non-standard detection coils is as Figure 2 shown.

[0080] Step S003: According to the relationship between the difference in the radii of the non-standard detection coil and the standard detection coil and the difference in the magnetic induction intensity data at the same height, and the relationship between the difference in the temperature data of the non-standard detection coil and the standard detection coil at the same height and the difference in the magnetic induction intensity data at the same height, obtain the second fitting curve at the same height. According to the difference in the magnetic induction intensity data corresponding to different second fitting curves at the same radius difference value, construct a temperature-magnetic relationship point set. According to the two different second fitting curves corresponding to each point in the temperature-magnetic relationship point set, and the difference in the temperature data of the non-standard detection coil corresponding to each point in the temperature-magnetic relationship point set at all heights, determine the weight of each point in the temperature-magnetic relationship point set. According to the weight of each point in the temperature-magnetic relationship point set, the temperature data of the non-standard detection coil and the standard detection coil, and the magnetic induction intensity data of the non-standard detection coil and the standard detection coil, obtain the temperature-magnetic relationship curve.

[0081] According to the relationship between the difference in the radii of the non-standard detection coil and the standard detection coil and the difference in the temperature data at the same height, and the difference in the magnetic induction intensity data at the same height, obtain the second fitting curve at the same height. Specifically: Take the difference in the temperature data of the non-standard detection coil and the standard detection coil at the same height in the detection coil disk, and the difference in the radii of the non-standard detection coil and the standard detection coil in the detection coil disk as independent variables, and take the difference in the magnetic induction intensity data of the non-standard detection coil and the standard detection coil at the same height in the detection coil disk as the dependent variable, and use multiple nonlinear regression analysis to obtain the second fitting curve at the same height. At the same time, obtain the goodness of fit of each second fitting curve.

[0082] It can be understood that during the process of the detection coil disk gradually approaching the energized electric coil disk, each acquisition moment corresponds to a height, and there is a corresponding second fitting curve for each height. The second fitting curve at the same height evaluates the relationship between the difference in the temperature data at the same height and the difference in the radii at the same height and the difference in the magnetic induction intensity data at the same height respectively. Therefore, the influence of height on the change in the magnetic induction intensity of the detection coil is eliminated.

[0083] Among them, obtaining the fitting curve and calculating the goodness of fit using multiple nonlinear regression analysis are both well-known techniques and will not be elaborated here. The goodness of fit is an index for evaluating the fitting degree of the fitting curve to the fitting data.

[0084] When calculating the second fitting curve at the same height, take the difference between the radius of each non-standard detection coil and the standard detection coil as the independent variable value to obtain the corresponding function value. It can be understood that the corresponding function value is the difference in magnetic induction intensity data at the same height.

[0085] Construct a temperature-magnetic relationship point set based on the differences between the magnetic induction intensity data differences corresponding to any two different second fitting curves when taking the same radius difference value.

[0086] Record the function values calculated from the second fitting curves at all heights as the first intensity differences, and record the difference between the radius of the non-standard detection coil and the standard detection coil corresponding to the first intensity difference as the first radius difference of the first intensity difference.

[0087] For any two different second fitting curves, calculate the difference between the first intensity differences corresponding to every two identical first radius differences. At the same time, calculate the difference between the temperature data of the detection coils corresponding to every two identical first radius differences. Take the difference between the first intensity differences as the ordinate and the difference between the temperature data as the abscissa to establish a plane rectangular coordinate system. Mark the points corresponding to every two identical first radius differences in the plane rectangular coordinate system, and record the set composed of all points in the plane rectangular coordinate system as the temperature-magnetic relationship point set.

[0088] It can be understood that each two different second fitting curves can determine a point in the temperature-magnetic relationship point set. At the same time, when determining a point in the temperature-magnetic relationship point set, it is determined according to every two identical first radius differences. Therefore, every two identical first radius differences correspond to a point in the temperature-magnetic relationship point set, that is, each non-standard detection coil corresponds to a point in the temperature-magnetic relationship point set.

[0089] The points in the temperature-magnetic relationship point set reflect the relationship between the magnetic induction intensity data and the temperature data, eliminating the influence of height and the radius of the detection coil on the relationship between the magnetic induction intensity data and the temperature data. The temperature-magnetic relationship point set is determined based on all the second fitting curves at the same height. Therefore, when the fitting effect of the second fitting curve at the same height is better, the relationship between the magnetic induction intensity data and the temperature data reflected by the points in the temperature-magnetic relationship point set is more accurate.

[0090] Record the standard deviation of the temperature data of the same detection coil at all heights as the temperature standard deviation of the detection coil.

[0091] Determine the weight of each point in the temperature-magnetic relationship point set according to the goodness of fit of two different second fitting curves corresponding to each point in the temperature-magnetic relationship point set, and the temperature standard deviation of the non-standard detection coil corresponding to each point in the temperature-magnetic relationship point set.

[0092]

[0093] In the formula, represents the weight of the th point in the temperature-magnetic relationship point set; represents the minimum value of the goodness of fit of two different second fitting curves corresponding to the th point in the temperature-magnetic relationship point set; represents a preset second parameter, whose function is to avoid the denominator being zero and making the fraction meaningless. In this embodiment, the value of the preset second parameter is 1; represents the temperature standard deviation of the non-standard detection coil corresponding to the th point in the temperature-magnetic relationship point set.

[0094] In order to more accurately reflect the corresponding relationship between temperature change and magnetic induction intensity change, a larger weight is given to the points with better fitting effects of the second fitting curves corresponding in the temperature-magnetic relationship point set, and a smaller weight is given to the points with poor fitting effects of the second fitting curves corresponding in the temperature-magnetic relationship point set. Therefore, when the goodness of fit of two different second fitting curves corresponding to a point is larger, the weight of the point in the temperature-magnetic relationship point set is larger.

[0095] When the temperature change of the non-standard detection coil is larger, the performance of the detection coil itself is more unstable, and the relationship between the magnetic induction intensity data and temperature data obtained from the detection coil is less reliable. At this time, the temperature standard deviation of the detection coil is larger, the weight of the corresponding point in the temperature-magnetic relationship point set is smaller, and the corresponding relationship between the temperature change and magnetic induction intensity change reflected by the corresponding point in the temperature-magnetic relationship point set is less accurate.

[0096] Take the difference between the temperature data of the non-standard detection coil and the standard detection coil as the independent variable, take the weight of the point in the temperature-magnetic relationship point set as the weight of the independent variable corresponding to the non-standard detection coil corresponding to the point, take the difference between the magnetic induction intensity data of the non-standard detection coil and the standard detection coil as the dependent variable, and use the weighted least squares polynomial fitting algorithm to obtain the temperature-magnetic relationship curve.

[0097] Using the weight of the point in the temperature-magnetic relationship point set as the weight of the independent variable corresponding to the non-standard detection coil corresponding to the point to weight the difference between the temperature data of the non-standard detection coil and the standard detection coil can make the relationship between the more reliable magnetic induction intensity data and temperature data have a greater impact on the fitting curve, and make the obtained temperature-magnetic relationship curve more accurate.

[0098] Thus, the temperature-magnetic relationship curve is obtained.

[0099] Step S004: Calibrate the magnetic induction intensity data of the non-standard detection coils at each height according to the temperature-magnetic relationship curve, so as to calibrate the magnetic measurement system of the medical cyclotron.

[0100] According to the Biot-Savart law, the relationship between the excitation current and the theoretical value of the magnetic induction intensity of the standard detection coil can be determined. Among them, the excitation current is the current value provided to the energized electric coil disk, so the excitation current is a known constant value.

[0101] Therefore, according to the excitation current, the theoretical value of the magnetic induction intensity data of the standard detection coil at each height can be obtained.

[0102] Calibrate the measured value of the magnetic induction intensity data of the non-standard detection coil according to the theoretical value of the magnetic induction intensity data of the standard detection coil at each height. Specifically: directly multiply or divide the magnetic induction intensity data of the standard detection coil numerically, so that the collected magnetic induction intensity data of the standard detection coil is equal to the theoretical value of the magnetic induction intensity data of the standard detection coil at the same height, and obtain the adjustment multiple for directly multiplying or dividing the magnetic induction intensity data of the standard detection coil numerically at each height. At each height, calibrate the magnetic induction intensity data of all non-standard detection coils using the adjustment multiple corresponding to the numerical multiplication or division at that height to obtain the calibrated magnetic induction intensity data of the non-standard detection coil at each height. Then, at each height, according to the difference between the temperature data of the non-standard detection coil and the standard detection coil and the temperature-magnetic relationship curve, calculate the difference between the magnetic induction intensity data of the non-standard detection coil and the standard detection coil at each height and record it as the first difference at each height, and use the sum of the first difference at each height and the calibrated magnetic induction intensity data of the non-standard detection coil at each height as the calibration value of the magnetic induction intensity data of the non-standard detection coil at that height.

[0103] At different height positions, the change of the magnetic induction intensity data of the non-standard detection coil is not linear. At the same time, the magnetic induction intensity data of the non-standard detection coil is affected by physical properties such as the resistance, temperature, and radius of the non-standard detection coil. Therefore, calibrating the magnetic induction intensity data of the non-standard detection coil at each height separately can ensure the accuracy of error calibration.

[0104] Thus, the calibration of the magnetic measurement system of the medical cyclotron is achieved.

[0105] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calibrating a medical cyclotron magnetic measurement system, characterized in that: The method comprises the following steps: Collect the radii of all different detection coils in the detection coil disk of the medical cyclotron, as well as the magnetic induction intensity data and temperature data of all detection coils in the detection coil disk at different heights, and obtain the longitudinal magnetic induction intensity sequence of the same detection coil and the transverse magnetic induction intensity sequence at the same height; Any detection coil in the detection coil disk is recorded as a target detection coil, an abnormal coefficient of the target detection coil is obtained, and a standard detection coil and a non-standard detection coil are determined according to the abnormal coefficients of all detection coils in the detection coil disk; According to the relationship between the difference in radius between the non-standard detection coil and the standard detection coil and the difference in magnetic induction intensity data at the same height, and the relationship between the difference in temperature data between the non-standard detection coil and the standard detection coil at the same height and the difference in magnetic induction intensity data at the same height, a second fitting curve at the same height is obtained; The function values ​​calculated by the second fitting curves at all heights are recorded as the first intensity difference, and the difference in radius between the non-standard detection coil and the standard detection coil corresponding to the first intensity difference is recorded as the first radius difference of the first intensity difference; the difference between the first intensity differences corresponding to every two identical first radius differences in any two different second fitting curves is used as the ordinate, and the difference between the temperature data of the detection coils corresponding to every two identical first radius differences in any two different second fitting curves is used as the abscissa, a plane rectangular coordinate system is established, points corresponding to every two identical first radius differences are marked in the plane rectangular coordinate system, and a set consisting of all points in the plane rectangular coordinate system is recorded as a temperature-magnetic relationship point set; Calculate the goodness of fit of each second fitting curve; calculate the weight of the point in the temperature-magnetic relationship point concentration, the calculation formula is: In the formula, Indicates the concentration of temperature-magnetic relationship points The weight of each point; Indicates the concentration of temperature-magnetic relationship points The minimum goodness of fit of two different second fitting curves corresponding to points; Indicates the preset second parameter; Indicates the concentration of temperature-magnetic relationship points The temperature standard deviation of the non-standard detection coil corresponding to each point; According to the weight of each point in the temperature-magnetism relationship point set, the temperature data of the non-standard detection coil and the standard detection coil, and the magnetic induction intensity data of the non-standard detection coil and the standard detection coil, a temperature-magnetism relationship curve is obtained; The magnetic induction intensity data of the non-standard detection coil at each height are calibrated according to the temperature-magnetism relationship curve to realize the calibration of the medical cyclotron magnetic measurement system.

2. A method for calibrating a medical cyclotron magnetic measurement system according to claim 1, characterized in that: The specific method of obtaining the longitudinal magnetic induction intensity sequence of the same detection coil and the transverse magnetic induction intensity sequence at the same height includes: Arrange all magnetic induction intensity data of the same detection coil in the detection coil disk in order from low to high according to the height of the magnetic induction intensity data collection, and obtain the longitudinal magnetic induction intensity sequence of the same detection coil; The magnetic induction intensity data of all detection coils collected at the same height are sorted in descending order of the radius of the detection coils to obtain a transverse magnetic induction intensity sequence at the same height.

3. A method for calibrating a medical cyclotron magnetic measurement system according to claim 1, characterized in that: The specific method of obtaining the abnormal coefficient of the target detection coil includes: Taking the radius of all detection coils in the detection coil disk as the independent variable and the magnetic induction intensity data of each detection coil at the same height as the dependent variable, a polynomial curve fitting algorithm is used to obtain a first fitting curve at the same height; respectively calculating the curvature of the points corresponding to the radius of all detection coils in each first fitting curve, arranging the curvatures of all calculated points of the first fitting curve at the same height in the order from small to large according to the radius of the detection coil corresponding to the curvature, and obtaining the curvature sequence at the same height; Any detection coil in the detection coil disk is recorded as the target detection coil, and the number of non-positive numbers in the curvature corresponding to the target detection coil in all curvature sequences at the same height is recorded as the number of non-positive curvatures of the target detection coil; The variance of all data contained in the first-order difference sequence of the curvature sequence at the same height is recorded as the first difference variance at the same height; The difference values ​​calculated from the curvatures of the points corresponding to the radius of all target detection coils in the curvature difference sequence at the same height are deleted, and the variances of all the remaining difference values ​​in the curvature difference sequence at the same height are recorded as the second difference variance of the target detection coil at the same height; According to the number of non-positive curvatures of the detection coils, the first differential variance at the same height, the second differential variance at the same height, and the correlation between the longitudinal magnetic induction intensity sequences of all the detection coils, the abnormal coefficient of each detection coil in the detection coil disk is obtained.

4. A method for calibrating a medical cyclotron magnetic measurement system according to claim 3, characterized in that: The method of obtaining the abnormal coefficient of each detection coil in the detection coil disk according to the number of non-positive curvatures of the detection coil, the first differential variance at the same height, the second differential variance at the same height, and the correlation between the longitudinal magnetic induction intensity sequences of all the detection coils includes: In the formula, Indicates the number of detection coils in the disk The anomaly coefficient of the detection coil; Indicates the number of detection coils in the disk The number of non-positive numbers contained in the first-order difference sequence of the longitudinal magnetic induction intensity sequence of the detection coils; Indicates the number of detection coils in the disk The number of non-positive curvatures of the detection coils; represents the mean of all first difference variances of the same height; Indicates the number of detection coils in the disk The mean of the variances of the second differences of all detection coils at the same height; represents the first parameter of the preset; Indicates the number of detection coils in the disk The average of the absolute values ​​of the correlation coefficients between the longitudinal magnetic induction intensity sequences of a detection coil and all other detection coils.

5. A medical cyclotron magnetic measurement system calibration method according to claim 1, characterized in that: The specific method of determining the standard detection coil and the non-standard detection coil includes: The detection coil with the smallest abnormal coefficient is recorded as the standard detection coil, and the detection coil that is not the standard detection coil is recorded as the non-standard detection coil.

6. A medical cyclotron magnetic measurement system calibration method according to claim 1, characterized in that: The specific method for obtaining the second fitting curve at the same height is: The difference in temperature data between the non-standard detection coil and the standard detection coil in the detection coil disk at the same height and the difference in radius between the non-standard detection coil and the standard detection coil in the detection coil disk are used as independent variables, and the difference in magnetic induction intensity data between the non-standard detection coil and the standard detection coil in the detection coil disk at the same height is used as the dependent variable. Multiple nonlinear regression analysis is used to obtain the second fitting curve at the same height.

7. A medical cyclotron magnetic measurement system calibration method according to claim 1, characterized in that: The specific method for obtaining the temperature-magnetic relationship curve is as follows: The difference in temperature data between the non-standard detection coil and the standard detection coil is taken as the independent variable, the weight of the point is taken as the weight of the independent variable corresponding to the non-standard detection coil corresponding to the point, and the difference in magnetic induction intensity data between the non-standard detection coil and the standard detection coil is taken as the dependent variable. Weighted curve fitting is performed to obtain the temperature-magnetism relationship curve.

8. A method for calibrating a medical cyclotron magnetic measurement system according to claim 1, characterized in that: The specific method of calibrating the magnetic induction intensity data of the non-standard detection coil at each height according to the temperature-magnetic relationship curve is as follows: Directly multiply or subtract the magnetic induction intensity data of the standard detection coil so that the collected magnetic induction intensity data of the standard detection coil is equal to the theoretical value of the magnetic induction intensity data of the standard detection coil at the same height, and obtain the adjustment multiple of directly multiplying or subtracting the magnetic induction intensity data of the standard detection coil at each height; at each height, calibrate the magnetic induction intensity data of all non-standard detection coils using the adjustment multiple of the numerical multiplication or subtraction corresponding to the height, and obtain the calibrated magnetic induction intensity data of the non-standard detection coils at each height; At each altitude, based on the difference in temperature data and the temperature-magnetic relationship curve between the non-standard detection coil and the standard detection coil, the difference in magnetic induction intensity data between the non-standard detection coil and the standard detection coil at each altitude is calculated and recorded as the first difference at each altitude, and the sum of the first difference at each altitude and the calibrated magnetic induction intensity data of the non-standard detection coil at each altitude is used as the calibration value of the magnetic induction intensity data of the non-standard detection coil at that altitude.

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