Magnetic field measurement verification method of medical cyclotron

Abstract

The invention relates to the technical field of magnetic field measurement, in particular to a magnetic field measurement verification method for a medical cyclotron, and the method comprises the steps: obtaining the temperature deviation value of each measurement region in any two times of measurement, and obtaining the temperature deviation value of each measurement region based on the numerical relationship between the temperature value measured each time and the working temperature; according to the temperature change condition and the magnetic field value change condition of the two times of measurement corresponding to the minimum temperature deviation value, whether measurement correction needs to be conducted on the corresponding measurement area or not is judged; then, a correction coordinate system is established by combining distribution of temperature deviation values, temperature changes and magnetic field changes between any two times of measurement in each measurement area; polynomial curved surface fitting is carried out on the correction coordinates of all the measurement areas in the correction windows of each measurement area and the symmetrical area of each measurement area, and a fitting curved surface equation is obtained; and determining the corrected magnetic field value of each measurement area and carrying out comparison verification. The invention aims to improve the magnetic field measurement verification precision of the medical cyclotron.

Description

Technical Field

[0001] The present application relates to the field of magnetic field measurement technology, and in particular to a magnetic field measurement and verification method for a medical cyclotron accelerator. Background Art

[0002] A small medical negative hydrogen cyclotron is a device specifically designed for producing radioisotopes. Its core function is to utilize negatively charged hydrogen ions (negative hydrogen ions) as accelerating particles. After high-energy acceleration, they bombard various targets (liquid, gas, or solid) to produce specific radionuclides. These devices are characterized by their compact size, high efficiency, and flexibility, making them widely used in medicine, particularly in nuclear medicine. Compared to traditional large cyclotrons, small negative hydrogen cyclotrons have a smaller footprint, are simpler to operate, and have lower operating costs, making them ideal for use in small and medium-sized medical institutions. Furthermore, they support the switching of multiple target materials, allowing for flexible adjustments to production plans based on actual needs, significantly enhancing the device's practicality and adaptability.

[0003] Small medical negative hydrogen cyclotrons utilize a compact structure and a deep-valley design at the magnetic poles, achieving greater axial focusing and effectively compressing the axial beam envelope. This allows for an extremely narrow magnetic air gap, minimizing power consumption in the magnet coils. However, the deep-valley design of the magnetic poles results in significant magnetic field gradients, which are further increased by the small size of the small medical negative hydrogen cyclotron. Small magnetic field deviations significantly impact the isochronism of the magnetic field, necessitating high precision in magnetic field measurement for medical cyclotrons.

[0004] During magnetic field measurements of medical cyclotrons, changes in ambient temperature can affect the results. On the one hand, temperature deviations from the cyclotron's operating temperature can cause fluctuations in its magnetic field values. On the other hand, temperature fluctuations can also affect the performance of the magnetic field measurement equipment, introducing systematic errors that can reduce measurement accuracy and affect the accuracy of medical cyclotron magnetic field verification. Summary of the Invention

[0005] In view of the above, it is necessary to provide a magnetic field measurement verification method for a medical cyclotron to solve the above problems.

[0006] One embodiment of the present application provides a method for measuring and verifying the magnetic field of a medical cyclotron, the method comprising: Obtain the magnetic field value and temperature value of each preset measurement area in each measurement; Analyze the difference between the temperature values of each measurement area at any two measurements and the preset operating temperature to obtain the temperature deviation value of each measurement area between any two measurements. Based on the numerical relationship between each measured temperature value and the operating temperature, combined with the temperature change and magnetic field value change corresponding to the minimum temperature deviation value between the two measurements, determine whether the corresponding measurement area needs measurement correction; For measurement areas that require measurement correction, the difference between the temperature obtained from each measurement in each measurement area and the preset operating temperature is analyzed to obtain a temperature deviation value. The distribution of the temperature deviation values, temperature changes, and magnetic field changes between any two measurements in each measurement area are combined to establish a correction coordinate system to obtain several correction coordinates for each measurement area. Based on the distribution of the sector-shaped magnetic poles of the medical cyclotron, peak areas and valley areas are set. Based on the distance between the measurement areas and the peak areas or valley areas where they are located, the correction window and symmetric areas of each measurement area are determined. Polynomial surface fitting is used for the correction coordinates of all measurement areas in the correction window of each measurement area and its symmetric areas. The fitting deviation of each correction coordinate is determined based on the temperature deviation value corresponding to each correction coordinate and the distance distribution characteristics of the points between the measurement areas. The fitting surface equation is obtained based on the fitting deviation. The magnetic field value is screened according to the numerical value of the temperature deviation value measured each time in each measurement area, and the correction value is obtained by combining the fitting surface equation, and the corrected magnetic field value of each measurement area is determined and compared and verified.

[0007] The specific process of obtaining the temperature deviation value of each measurement area between any two measurements is as follows: The difference between the temperature of each measurement area at any two measurements and the operating temperature is calculated and recorded as the first difference and the second difference respectively; the average of the first difference and the second difference is recorded as the temperature deviation value of each measurement area between the two measurements.

[0008] The determination of whether measurement correction is required for the corresponding measurement area is specifically as follows: For each measurement area, the temperature value change and the magnetic field value change are calculated based on the temperature value and magnetic field value obtained in any two measurements; For each measurement area, if the temperature value measured each time is equal to the operating temperature, then no subsequent measurement correction is required for the corresponding measurement area; otherwise, the temperature value change and magnetic field value change corresponding to the minimum temperature deviation value of each measurement area are recorded as the reference temperature value change and reference magnetic field value change; If the change in the reference magnetic field value of the measurement area is equal to zero, no subsequent measurement correction is required for the corresponding measurement area; if the change in the reference magnetic field value of the measurement area is not zero, measurement correction is required for the corresponding measurement area.

[0009] The temperature deviation value is specifically the difference between the temperature measured each time and the operating temperature.

[0010] The establishment of the correction coordinate system is specifically as follows: The average of the temperature deviation values obtained from any two measurements is taken as the average temperature deviation of each measurement area measured in the two arbitrary measurements; A correction coordinate system is constructed with the average temperature value deviation, temperature value change, and magnetic field value change as three orthogonal coordinate axes.

[0011] The setting of the peak area and the valley area specifically includes dividing the area corresponding to each sector-shaped magnetic pole into a peak area, and dividing the area corresponding to each non-sector-shaped magnetic pole into a valley area.

[0012] The determination of the fitting deviation of each correction coordinate is specifically as follows: The fitting deviation weight of each corrected coordinate is recorded as , its formula form is: Where, Indicates the temperature deviation value corresponding to each correction coordinate; represents an exponential function with a natural constant as its base; Indicates the Manhattan distance between the measurement area and its central area corresponding to each correction coordinate; Indicates the preset distance; Indicates the preset parameters; The difference between the magnetic field change value corresponding to each corrected coordinate and its coordinate value on the fitting surface is calculated, and forward fused with the fitting deviation weight to obtain the fitting deviation of each corrected coordinate.

[0013] The fitting surface equation obtained based on the fitting deviation is specifically: Adding the fitting deviations obtained from the correction coordinates of all measurement areas in the correction window of each measurement area and its symmetrical area to obtain the accumulated deviation value of the fitting surface equation; The surface is iterated for the highest number of times, and the condition for obtaining the fitting surface equation is either reaching the preset maximum number of iterations or the accumulated deviation value of the fitting surface equation no longer decreases.

[0014] The process of obtaining the correction value is specifically as follows: For each measurement area, the measured magnetic field value corresponding to the temperature deviation value with the smallest absolute value is obtained and recorded as the magnetic field value to be corrected; the temperature deviation value with the smallest absolute value is used as the coordinate value of the dimension corresponding to the average temperature value deviation and the temperature value change, and substituted into the fitting surface equation to obtain the correction value.

[0015] The determination of the corrected magnetic field value of each measurement area and the comparison and verification are specifically as follows: The sum of the magnetic field value to be corrected and the correction value of each measurement area is taken as the corrected magnetic field value of each measurement area; if the error between the corrected magnetic field values of all measurement areas and the corresponding theoretically designed magnetic field values is less than the preset value, the verification can be passed.

[0016] This application has at least the following beneficial effects: This application utilizes the symmetrical characteristics of the magnetic field distribution of a medical cyclotron to expand the temperature and magnetic field values involved in error estimation; through a limited number of repeated measurements, measurement correction of the magnetic field values is achieved, while improving measurement accuracy and avoiding the decrease in magnetic field measurement verification efficiency caused by too many repeated measurements.

[0017] To address the issue of varying degrees of temperature influence in different electromagnetic environments, this application establishes a correction coordinate system and employs a surface fitting algorithm to estimate the error variation caused by temperature measurements in different measurement areas. Furthermore, based on the role of different correction coordinates in estimating the error variation in magnetic field measurements, fitting bias weights are calculated to enhance the reliability of error correction for magnetic field values, reduce the systematic error introduced by temperature variations in magnetic field measurements, and improve the accuracy of medical cyclotron magnetic field measurement verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart of the magnetic field measurement verification method for a medical cyclotron provided in this application; Figure 2 Schematic diagram of the magnetic field distribution of the medical cyclotron provided in this application. DETAILED DESCRIPTION

[0019] In the description of the embodiments of this application, words such as "exemplary," "or," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary," "or," and "for example" is intended to present the relevant concepts in a concrete manner.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the art of this application. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0021] It should also be noted that the terms "first" and "second" in this application and its accompanying drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. The methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the methods. Without departing from the scope of protection of this application, the order of execution of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0022] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0023] This application proposes a method for measuring and verifying the magnetic field of a medical cyclotron accelerator. The implementation process is as follows: Figure 1 As shown, the method includes the following steps: S1: Obtain the magnetic field value and temperature value of each preset measurement area in each measurement.

[0024] During the operation of the medical cyclotron, the temperature of the accelerator chamber is kept stable through its cooling system, thereby ensuring the normal operation of the medical cyclotron.

[0025] This application is aimed at measuring and verifying the magnetic field generated by a medical cyclotron in its normal working state, and the measurement environment temperature is maintained at the working temperature of the medical cyclotron through its internal cooling system. near, where the operating temperature of medical cyclotrons is 25℃.

[0026] Due to the instability of the heat source inside the accelerator and the lag of the cooling system in temperature control, the temperature of the accelerator chamber will Changes occur nearby.

[0027] Temperature changes in the measurement environment directly lead to thermal expansion of the medical cyclotron magnet material, changes in the resistance of the superconducting coils, and changes in the material's magnetic permeability. This can cause the magnetic field generated by the accelerator chamber to deviate from the value at operating temperature, affecting the magnetic field measurement and verification of the medical cyclotron. Furthermore, temperature changes can increase systematic errors introduced by temperature drift of electronic components within the magnetic field measurement device, reducing the accuracy of medical cyclotron magnetic field measurement and verification.

[0028] This application performs magnetic field measurement on a medical cyclotron accelerator, and installs a temperature sensor at the probe carried by the magnetic field measurement device to measure and obtain the temperature value at the same time.

[0029] The magnetic field measurement requirements of this application are: the radial range of the magnetic field is 0-50cm, the interval is 1cm; the angular range is 0-360°, the angular interval is 1°; the random error of the magnetic field value measurement is less than The radial motion error is less than 0.1 mm, and the angular motion error is less than 12 s. Each radial interval and each angular interval constitutes a measurement area. The above process divides the entire accelerator chamber into multiple measurement areas, and the magnetic field and temperature values of each measurement area are measured.

[0030] The specific measurement method implementer may adopt a cyclotron magnetic field measurement device disclosed in publication number CN103675720A, or a cyclotron magnet isochronous magnetic field measurement device and method disclosed in publication number CN116256676A, or other measurement devices or methods that meet the magnetic field measurement requirements of this application.

[0031] The above method is used to measure the acceleration chamber of the entire medical cyclotron N times, where N in this application is set to 5. Thus, the magnetic field value and temperature value of each measurement area during the N measurement processes are obtained.

[0032] S2: Analyze the degree of difference between the temperature values of any two measurements in each measurement area and the preset operating temperature to obtain the temperature deviation value of each measurement area between any two measurements. Based on the numerical relationship between the temperature value measured each time and the operating temperature, combined with the temperature change of the two measurements corresponding to the minimum temperature deviation value and the change of the magnetic field value, determine whether the corresponding measurement area needs measurement correction.

[0033] Due to the deep valley design of the sector-shaped magnetic poles of the medical cyclotron, the magnetic field values in different measurement areas vary greatly.

[0034] Taking into account the differences in interference caused by temperature changes under different magnetic field value ranges and different temperatures, for each measurement area, the temperature deviation value between any two measurements is determined based on the difference between the temperature under any two measurements and the operating temperature. Specifically, the difference between the temperature under any two measurements and the operating temperature of each measurement area is calculated, and recorded as the first difference and the second difference, respectively; the average of the first difference and the second difference is recorded as the temperature deviation value between the two measurements for each measurement area. In this embodiment, the difference between temperatures is calculated by the absolute value of the difference.

[0035] The temperature deviation value reflects the average deviation between the temperature value of a measurement area and the operating temperature during two measurements. The larger the temperature deviation value, the greater the degree of temperature interference on the magnetic field values obtained in the corresponding two measurements.

[0036] For each measurement area, the temperature value change and the magnetic field value change are calculated based on the temperature values and magnetic field values obtained in any two measurements. The temperature change value is specifically the difference between the temperatures obtained in the two measurements; the magnetic field change value is specifically the difference between the magnetic field values obtained in the two measurements. Both reflect the degree of change in the magnetic field value under different degrees of temperature change.

[0037] For each measurement area, if the measurement environment temperature value of a measurement area is equal to the operating temperature, then no subsequent measurement calibration is required for the corresponding measurement area.

[0038] If there is no measurement environment temperature value equal to the working temperature in the corresponding measurement area, the temperature value change and the magnetic field value change corresponding to the minimum temperature deviation value are recorded as the reference temperature value change and the reference magnetic field value change.

[0039] Furthermore, if the change in the reference magnetic field value of the measurement area is zero, it indicates that the change in the temperature value of the measurement environment has no effect on the magnetic field measurement, and no subsequent measurement correction is required for the corresponding measurement area.

[0040] If the variation of the reference magnetic field value in the measurement area is not zero, a subsequent measurement correction is performed for the measurement area.

[0041] S3: For the measurement areas that need to be corrected, analyze the difference between the temperature obtained from each measurement in each measurement area and the preset working temperature to obtain the temperature deviation value, and establish a correction coordinate system based on the distribution of the temperature deviation value, temperature change, and magnetic field change between any two measurements in each measurement area to obtain several correction coordinates for each measurement area; based on the distribution of the sector poles of the medical cyclotron, set the peak area and valley area, and determine the correction window and symmetric area of each measurement area based on the distance between the measurement areas and the peak area or valley area where they are located; use polynomial surface fitting to fit the correction coordinates of all measurement areas in the correction window of each measurement area and its symmetric area, and determine the fitting deviation of each correction coordinate based on the temperature deviation value corresponding to each correction coordinate and the distance distribution characteristics of the points between the measurement areas; obtain the fitting surface equation based on the fitting deviation.

[0042] For each measurement area, the difference between the temperature measured each time and the operating temperature is obtained and recorded as the temperature deviation value; the average value of the temperature deviation values obtained from any two measurements is taken as the average temperature deviation of each measurement area in the two measurements.

[0043] This application uses the average temperature deviation, temperature change, and magnetic field change as three orthogonal coordinate axes to construct a correction coordinate system; so far, each measurement area has a total of Corrected coordinates.

[0044] Considering the symmetrical distribution of the medical cyclotron magnetic field, the schematic diagram of the medical cyclotron magnetic field distribution is as follows: Figure 2 As shown in the figure, the sector-shaped magnetic pole corresponding to the shaded portion 1 represents the peak region; the non-sector-shaped magnetic pole corresponding to the unshaded portion 2 represents the valley region. The four sector-shaped magnetic poles are divided into peak regions, and the areas corresponding to the non-sector-shaped magnetic poles are divided into valley regions. Thus, each measurement area is divided into a corresponding peak region or valley region.

[0045] With each measurement area as the center, all measurement areas within the peak or valley region within that area whose Manhattan distance to each measurement area is less than a preset distance are obtained to form a correction window for each measurement area. The remaining measurement areas within the correction window are recorded as adjacent areas of each measurement area. In this embodiment, the preset distance is 5. Because the electromagnetic environments within the correction windows are similar, the magnetic field measurements are more uniformly affected by temperature changes. Using these as measurement data expansion can reduce the number of measurements, improve magnetic field measurement accuracy, and minimize the decline in measurement efficiency.

[0046] With respect to the position of each measurement area in its peak area or valley area, the measurement areas of each measurement area at the same position in the other three valley areas or peak areas are recorded as the symmetrical areas of each measurement area.

[0047] This application adopts a surface fitting algorithm to obtain the degree to which the magnetic field value in each measurement area is affected by the change of temperature value. Specifically: first, the maximum number of times the surface is fitted for the first time is 1. For each measurement area, the correction coordinates of itself and all symmetrical areas, as well as the correction coordinates of itself and the adjacent areas of the symmetrical area are used to form a reference correction coordinate set for each measurement area. All elements in the set are used as input, and a polynomial surface fitting algorithm is used to output the fitting surface equation.

[0048] Secondly, for each measurement area, the reference correction coordinate set obtained by curve fitting is used to calculate the fitting deviation weight of each correction coordinate. The formula is: Where, Indicates the temperature deviation value corresponding to each correction coordinate; It represents an exponential function with a natural constant as the base, which aims to reflect the quantitative change relationship between the temperature deviation value and the fitting deviation weight, and to limit the numerical value of the fitting deviation weight; Indicates the Manhattan distance between the measurement area and its central area corresponding to each correction coordinate; Indicates the preset distance, which is 5 in this embodiment; Indicates the preset parameter, the value is 1, the purpose is to prevent the denominator from being zero; Represents the fitting bias weight of the corrected coordinates.

[0049] It should be understood that the larger the temperature deviation value, the less reliable the temperature difference compensation for the magnetic field value near the operating temperature, and a smaller weight is set. The larger the Manhattan distance, the greater the magnetic field variation in the adjacent area, the less reliable the error correction for the measurement area, and the smaller the weight is set.

[0050] Furthermore, the fitting deviation of each correction coordinate is calculated. Specifically, the difference between the magnetic field change value corresponding to each correction coordinate and its coordinate value on the fitting surface is calculated, and forward fused with the fitting deviation weight to obtain the fitting deviation of each correction coordinate; in this embodiment, the difference between the variables is calculated by the square of the difference between the variables; the forward fusion between multiple variables adopts the multiplication calculation method.

[0051] Finally, the fitting deviations of all corrected coordinates are accumulated and recorded as the cumulative deviation value of the fitted surface equation. Iterations are performed for the maximum number of iterations, increasing the maximum number of iterations by 1, and setting the maximum number of iterations to 6 to avoid overfitting. When the maximum number of iterations is reached or the cumulative deviation value of the fitted surface equation no longer decreases, the final fitted surface equation is output, reflecting the impact of temperature changes in the current measurement area on the magnetic field measurement.

[0052] S4: Filter the magnetic field value according to the numerical value of the temperature deviation value measured each time in each measurement area, obtain the correction value by combining the fitting surface equation, determine the corrected magnetic field value of each measurement area, and compare and verify.

[0053] For each measurement area, the measured magnetic field value corresponding to the temperature deviation value with the smallest absolute value is obtained and recorded as the magnetic field value to be corrected; the temperature deviation value with the smallest absolute value is used as the coordinate value of the dimension corresponding to the average temperature value deviation and the temperature value change in the final correction coordinate, and the magnetic field change of the final correction coordinate at the fitting surface is obtained and recorded as the correction value; the sum of the magnetic field value to be corrected and the correction value of each measurement area is used as the corrected magnetic field value of each measurement area.

[0054] Compare the corrected magnetic field values for each measurement area with the corresponding theoretically designed magnetic field values. If the error between the magnetic field values for all measurement areas and the theoretically designed magnetic field values is less than 50 Gs, the verification is passed. This completes the magnetic field measurement verification of the medical cyclotron.

[0055] The flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the systems, methods and computer program products according to the embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the part of the module, program segment or code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in an order different from that disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified function or action, or may be implemented by a combination of dedicated hardware and computer instructions.

[0056] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for measuring and verifying the magnetic field of a medical cyclotron, characterized in that: The method comprises the following steps: Obtain the magnetic field value and temperature value of each preset measurement area in each measurement; Analyze the difference between the temperature values of each measurement area at any two measurements and the preset operating temperature to obtain the temperature deviation value of each measurement area between any two measurements. Based on the numerical relationship between each measured temperature value and the operating temperature, combined with the temperature change and magnetic field value change corresponding to the minimum temperature deviation value between the two measurements, determine whether the corresponding measurement area needs measurement correction; For measurement areas that require measurement correction, the difference between the temperature obtained from each measurement in each measurement area and the preset operating temperature is analyzed to obtain a temperature deviation value. The distribution of the temperature deviation values, temperature changes, and magnetic field changes between any two measurements in each measurement area are combined to establish a correction coordinate system to obtain several correction coordinates for each measurement area. Based on the distribution of the sector-shaped magnetic poles of the medical cyclotron, peak areas and valley areas are set. Based on the distance between the measurement areas and the peak areas or valley areas where they are located, the correction window and symmetric areas of each measurement area are determined. Polynomial surface fitting is used for the correction coordinates of all measurement areas in the correction window of each measurement area and its symmetric areas. The fitting deviation of each correction coordinate is determined based on the temperature deviation value corresponding to each correction coordinate and the distance distribution characteristics of the points between the measurement areas. The fitting surface equation is obtained based on the fitting deviation. The magnetic field value is screened according to the numerical value of the temperature deviation value measured each time in each measurement area, and the correction value is obtained by combining the fitting surface equation, and the corrected magnetic field value of each measurement area is determined and compared and verified.

2. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 1, wherein: The specific process of obtaining the temperature deviation value of each measurement area between any two measurements is as follows: The difference between the temperature of each measurement area at any two measurements and the operating temperature is calculated and recorded as the first difference and the second difference respectively; the average of the first difference and the second difference is recorded as the temperature deviation value of each measurement area between the two measurements.

3. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 1, wherein: The determination of whether measurement correction is required for the corresponding measurement area is specifically as follows: For each measurement area, the temperature value change and the magnetic field value change are calculated based on the temperature value and magnetic field value obtained in any two measurements; For each measurement area, if the temperature value measured each time is equal to the operating temperature, no subsequent measurement correction is required for the corresponding measurement area; Otherwise, the temperature value change and the magnetic field value change corresponding to the minimum temperature deviation value of each measurement area are recorded as the reference temperature value change and the reference magnetic field value change; If the change in the reference magnetic field value of the measurement area is zero, no subsequent measurement correction is required for the corresponding measurement area; if the change in the reference magnetic field value of the measurement area is not zero, measurement correction is required for the corresponding measurement area.

4. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 1, wherein: The temperature deviation value is specifically the difference between the temperature measured each time and the operating temperature.

5. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 3, wherein: The establishment of the correction coordinate system is specifically as follows: The average of the temperature deviation values obtained from any two measurements is taken as the average temperature deviation of each measurement area measured in the two arbitrary measurements; A correction coordinate system is constructed with the average temperature value deviation, temperature value change, and magnetic field value change as three orthogonal coordinate axes.

6. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 1, wherein: The setting of the peak area and the valley area specifically includes dividing the area corresponding to each sector-shaped magnetic pole into a peak area, and dividing the area corresponding to each non-sector-shaped magnetic pole into a valley area.

7. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 3, wherein: The determination of the fitting deviation of each correction coordinate is specifically as follows: The fitting deviation weight of each corrected coordinate is recorded as , its formula form is: Where, Indicates the temperature deviation value corresponding to each correction coordinate; represents an exponential function with a natural constant as its base; Indicates the Manhattan distance between the measurement area and its central area corresponding to each correction coordinate; Indicates the preset distance; Indicates the preset parameters; The difference between the magnetic field change value corresponding to each corrected coordinate and its coordinate value on the fitting surface is calculated, and forward fused with the fitting deviation weight to obtain the fitting deviation of each corrected coordinate.

8. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 1, wherein: The fitting surface equation is obtained based on the fitting deviation, specifically: Adding the fitting deviations obtained from the correction coordinates of all measurement areas in the correction window of each measurement area and its symmetrical area to obtain the accumulated deviation value of the fitting surface equation; The surface is iterated for the highest number of times, and the condition for obtaining the fitting surface equation is either reaching the preset maximum number of iterations or the accumulated deviation value of the fitting surface equation no longer decreases.

9. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 1, wherein: The process of obtaining the correction value is specifically as follows: For each measurement area, the measured magnetic field value corresponding to the temperature deviation value with the smallest absolute value is obtained and recorded as the magnetic field value to be corrected; the temperature deviation value with the smallest absolute value is used as the coordinate value of the dimension corresponding to the average temperature value deviation and the temperature value change, and substituted into the fitting surface equation to obtain the correction value.

10. The method for measuring and verifying the magnetic field of a medical cyclotron according to claim 9, wherein: The determination of the corrected magnetic field value of each measurement area and the comparison and verification are specifically as follows: The sum of the magnetic field value to be corrected and the correction value of each measurement area is taken as the corrected magnetic field value of each measurement area; if the error between the corrected magnetic field values of all measurement areas and the corresponding theoretically designed magnetic field values is less than the preset value, the verification can be passed.

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