Calibration Method for Detector Detection Efficiency
Through the combination of Monte Carlo simulation and K fluorescence radiation device, the detector parameters are adjusted, and the problem of large deviation of the detector detection efficiency scale in the prior art is solved, and a fast and accurate detector scale is achieved.
Patent Information
- Application Number
- CN202211268905.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-17
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2042-10-17
AI Technical Summary
In the prior art, the standard source experimental scale method is limited by the radiation source itself and the environment, and the Monte Carlo simulation scale method cannot obtain accurate detector parameters, resulting in a large deviation of the detector detection efficiency scale.
The detection efficiency of the detector on different energy X-rays was calculated by using the Monte Carlo simulation method, and combined with the K fluorescence radiation device to measure the intensity ratio of the characteristic X-rays of Kα and Kβ. By adjusting the crystal size and dead zone thickness of the detector until the error is less than the preset value, the accurate scale of the detector detection efficiency is achieved.
The detection efficiency of the scale detector is quickly and accurately avoids the environmental dependence of the standard source experimental scale method and the parameter inaccuracy of the Monte Carlo simulation scale method, and improves the accuracy and efficiency of the scale.
Smart Images
Figure CN115755154B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of monoenergetic X-rays, and in particular to a method for calibrating the detection efficiency of a detector. Background Art
[0002] X-rays are widely used in the fields of medical diagnosis, industrial non-destructive testing, and scientific research, and their role is becoming increasingly important, especially in the fields of space science observation, dark matter search, and gravitational wave detection. The X-rays generated by an X-ray machine originate from bremsstrahlung that occurs when a high-speed electron beam bombards the anode target. The bremsstrahlung X-rays are a continuous spectrum with a large energy range. Compared with the continuous-spectrum X-rays of bremsstrahlung, monoenergetic X-rays have unique advantages. The monoenergetic X-ray digital subtraction technology is applied in medical diagnosis and industrial non-destructive testing, and clearer, more accurate, and higher-resolution images can be obtained than those of continuous-spectrum X-rays.
[0003] As a standard radiation source, a monoenergetic X-ray radiation device can conduct research on the energy linearity, energy resolution, detection efficiency, and energy response matrix of various nuclear radiation detectors. Among them, the detection efficiency, as a key performance parameter of the detector, directly determines the measurement accuracy of the detector in practical applications. The accurate measurement of the monoenergetic X-ray fluence is the key to realizing the calibration of the detection efficiency of the detector. Without accurate fluence measurement, the absolute number of photons cannot be obtained, and the detection efficiency of the detector to be calibrated cannot be given. The fluence is obtained by measuring the number of photons passing through a unit area of a monoenergetic X-ray source with a standard detector with a known detection efficiency. Therefore, it is necessary to obtain the detection efficiency curve of the standard detector to obtain accurate fluence.
[0004] Currently, the commonly used methods for calibrating the detection efficiency of detectors are: standard source experimental calibration method and Monte Carlo simulation calibration method.
[0005] The standard source experimental calibration method refers to obtaining the detection efficiency of the detector for the characteristic energy at a certain specific detection position by measuring a radionuclide with a known radioactivity and properties. The standard source experimental calibration method is relatively accurate and reliable, but this method requires that the geometric shape, density, composition, measurement state, calculation method of the γ peak area, and self-absorption effect of the standard source are basically the same as those of the object to be measured. In practical applications, due to the short half-life of the radionuclide and the high requirement for the uniformity of the composition of the standard body source, the preparation and storage of the calibration standard source are difficult, and it is easily affected by the environment and requires repeated calibration as the environment changes. The most common is to use a radioactive point source for the experimental calibration of the detector. Since the activity of the radioactive point source is low and it is not a parallel beam, the experiment generally takes a long time and has a large uncertainty, and the feasibility is poor.
[0006] The Monte Carlo simulation calibration method refers to simulating the activity process of γ-rays in the detector by the Monte Carlo method, so as to obtain the detection efficiency of the detector for characteristic energies. Although this method avoids the complex preparation and management processes of standard sources, has a wider application range, a large energy interval, and strong quantitative analysis ability, the parameters of the detector model are easily restricted by the manufacturer, and accurate and comprehensive detector parameters cannot be obtained, resulting in a large difference between the simulated detection efficiency and the experimental value. Therefore, parameters such as crystal size, dead layer thickness, and the distance between the aluminum layer and the crystal need to be corrected. Summary of the Invention
[0007] Based on this, in view of the problems of the existing method for calibrating the detection efficiency of detectors, namely, the large deviation in efficiency calibration caused by the limitations of the radioactive source itself and the environment in the standard source experimental calibration method, and the inability to obtain accurate detector parameters in the Monte Carlo simulation calibration method, it is necessary to provide a calibration method for the detection efficiency of detectors.
[0008] 1. A calibration method for the detection efficiency of a detector, characterized by comprising the following steps:
[0009] Using the Monte Carlo simulation method, obtain the detection efficiency of the detector for X-rays with different energies;
[0010] Using the Monte Carlo simulation method, calculate the intensity ratio L of the K characteristic X-rays generated by the radiator in the K fluorescence radiation device. α K β K mc ;
[0011] Experimentally measure the intensities of the K and K characteristic X-rays of the radiator, and obtain the intensity ratio L through the correction of the detection efficiency. α K β K mea ;
[0012] Replace the radiator in the K fluorescence radiation device, and calculate multiple groups of intensity ratios L and intensity ratios L according to the above steps. mc L mea ;
[0013] Judge whether the error between the intensity ratio L of each group and the intensity ratio L is less than a preset value; mc L mea ;
[0014] If not, adjust the crystal size and dead zone thickness of the detector;
[0015] Repeat the above steps in a loop until the error between the intensity ratio L of each group and the intensity ratio L is less than the preset value. mc L mea ;
[0016] The calibration method for the detection efficiency of the above detector, by comparing the K α and K β intensity ratio L mc of characteristic X-rays obtained by the Monte Carlo simulation method with the intensity ratio L mea after experiment and correction, verifies the accuracy of the detection efficiency of the detector for parallel beam X-rays with different energies obtained by the Monte Carlo simulation method, and then obtains the detection efficiency of the detector for parallel beam X-rays with different energies, which can quickly and accurately calibrate the detection efficiency of the detector, and can avoid the disadvantages of large efficiency calibration deviation caused by the limitations of the radioactive source itself and the environment in the standard source experimental calibration method and the inability to obtain accurate detector parameters in the Monte Carlo simulation calibration method.
[0017] In one embodiment, the steps of obtaining the detection efficiency of the detector for X-rays with different energies by using the Monte Carlo simulation method are specifically as follows:
[0018] According to the crystal size and dead layer thickness parameters of the detector, the detection efficiency of the detector for X-rays with different energies is calculated by using the Monte Carlo simulation method.
[0019] In one embodiment, the steps of calculating the intensity ratio L α and L β of K mc characteristic X-rays generated by the radiator in the K fluorescence radiation device by using the Monte Carlo simulation method are specifically as follows:
[0020] Provide a K fluorescence radiation device, and use the Monte Carlo simulation method to calculate the intensities I α and I β of K α and K β characteristic X-rays generated by the radiator, and obtain the intensity ratio L mc , where L mc =I α / I β .
[0021] In one embodiment, the steps of experimentally measuring the intensities of K α and K β characteristic X-rays of the radiator are specifically as follows:
[0022] Experimentally measure the energy spectra of K α and K β characteristic X-rays generated by the radiator in the K fluorescence radiation device, and calculate the intensities i α and i β of K α and K β characteristic X-rays obtained from the experiment according to the experimentally measured energy spectra.
[0023] In one embodiment, the step of obtaining the intensity ratio L by correcting the detection efficiency is as follows: mea Specifically:
[0024] Divide the intensities i of the characteristic X-rays of K α and K β obtained from the experiment by the detection efficiency of the detector at the corresponding energy to obtain the corrected intensities i of the characteristic X-rays of K α and K β and calculate the intensity ratio L α where L β = i α修正 / i β修正 . mea mea α修正 β修正
[0025] In one embodiment, the radiation body replaced by the K-fluorescence radiation device can generate characteristic X-rays of different energies.
[0026] In one embodiment, the K-fluorescence radiation device includes:
[0027] An X-ray machine for generating X-rays;
[0028] A K-fluorescence generating device including a support and a radiation body provided on the support, the radiation body receiving the X-rays and exciting characteristic X-rays; and
[0029] A detection device for measuring the energy spectrum of the characteristic X-rays.
[0030] In one embodiment, the K-fluorescence radiation device further includes a shielding box, the X-ray machine and the K-fluorescence generating device are housed in the shielding box, the shielding box is provided with a light hole for the characteristic X-rays to pass through, and the detection device is disposed opposite to the light hole.
[0031] In one embodiment, the K-fluorescence radiation device further includes a collimator, the collimator is installed outside the shielding box, the collimator is coaxially arranged with the light hole, and a diaphragm is provided at the light outlet of the collimator.
[0032] In one embodiment, a trap is further included, the trap is disposed behind the radiation body along the irradiation direction of the X-ray beam to trap the rays leaking through the radiation body. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 is a flowchart of the calibration method for the detection efficiency of the detector of the present invention;
[0034] Figure 2 It is a schematic structural diagram of a K fluorescence radiation device in an embodiment.
[0035] In the accompanying drawings, the list of components represented by each reference numeral is as follows:
[0036] 10. X-ray machine; 20. K fluorescence generating device; 21. Support; 22. Radiator; 30. Detection device; 40. Shielding box; 50. Collimator; 60. Diaphragm; 70. Trap. Specific Embodiments
[0037] To make the above objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the specific details described below are only some embodiments of the present invention, and the present invention can also be implemented in many other embodiments different from those described herein. 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.
[0038] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiment.
[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.
[0040] Please refer to Figure 1 , in an embodiment, a method for calibrating the detection efficiency of a detector includes the following steps:
[0041] Step S110: Using the Monte Carlo simulation method, obtain the detection efficiency of the detector for X-rays of different energies.
[0042] Specifically, the Monte Carlo simulation method can simulate the activity process of γ-rays in the detector, thereby obtaining the detection efficiency of the detector for characteristic energies. The detection efficiency of the detector obtained by the Monte Carlo simulation method is affected by the parameters of the detector.
[0043] In one embodiment, according to the crystal size and dead layer thickness parameters of the detector, the Monte Carlo simulation method can be used to calculate the detection efficiency of the detector for X-rays with different energies.
[0044] On the basis of the above embodiments, further, the parameters of the detector can be selected as the crystal size, dead layer thickness, beryllium window thickness, and the distance between the crystal and the beryllium window. The parameters calculated by the Monte Carlo simulation method are more comprehensive, which can further ensure the accuracy of the detection efficiency.
[0045] Step S120: Using the Monte Carlo simulation method, calculate the intensity ratio L of the K α , K β characteristic X-rays generated by the radiator 22 in the K fluorescence radiation device. mc .
[0046] Please refer to Figure 2 ,, the K fluorescence radiation device includes an X-ray machine 10, a K fluorescence generating device 20, and a detection device 30. The X-ray machine 10 is used to generate X-rays, and the K fluorescence generating device 20 is arranged on the optical path of the X-rays. The K fluorescence generating device 20 includes a support 21 and a radiator 22 arranged on the support 21. The radiator 22 can receive the X-rays emitted by the X-ray machine 10 and excite characteristic X-rays. The detection device 30 is used to measure the energy spectrum of the excited characteristic X-rays.
[0047] Therefore, according to the above K fluorescence radiation device, using the Monte Carlo simulation method, calculate the intensity I of the K α , K β characteristic X-rays, α , I β , and obtain the intensity ratio L mc , where L mc = I α / I β . Among them, K fluorescence has the advantages of large fluence, many energy points, good stability, low production cost, etc., which can facilitate the calibration of the detection efficiency of the detector and reduce the calibration cost.
[0048] In one embodiment, the radiator 22 is the core component for generating fluorescence. Different materials are excited to emit corresponding characteristic X-rays. The minimum purity of the material of the radiator 22 should be 99.9% to prevent fluorescence secondary pollution caused by impurities. The radiator 22 can be a metal sheet or a powdered compound dispersed in a plastic binder, such as an oxide, carbonate, or sulfate. The binder only contains substances with an atomic number lower than that of the fluorescent element (i.e., Zeff ≤ 8). The support 21 of the radiator 22 should also be composed of substances with an atomic number lower than that of the element of the radiator 22. The parameters of the radiator 22 used for the low-energy K fluorescence reference radiation recommended by ISO-4037 are shown in Table 1.
[0049] Table 1 Radiator and filter material parameters of low-energy K-fluorescent X-ray radiation device 1)
[0050]
[0051] Note: 1) For the radiator and secondary filter material of No. 1-9, the simple substances are active and difficult to store, and are replaced by appropriate compounds; 2) The optimal tube voltage for generating the purest reference radiation field. This tube voltage is approximately twice the energy of the K absorption edge of the corresponding radiator. If a higher air kerma rate is required, a higher tube voltage can be used, but this will result in lower radiation purity
[0052] On the basis of the above embodiments, further, the K-fluorescent radiation device further includes a shielding box 40. The X-ray machine 10 and the K-fluorescent generating device 20 are housed in the shielding box 40, and the shielding box 40 is used to shield external environmental interference. An optical hole is provided on the shielding box 40, and the characteristic X-rays excited by the radiator 22 of the K-fluorescent generating device 20 are emitted out of the shielding box 40 through the optical hole
[0053] On the basis of the above embodiments, further, the K-fluorescent radiation device further includes a collimator 50. The collimator 50 is installed outside the shielding box 40 and is coaxially arranged with the optical hole. The collimator 50 is used to collimate the characteristic X-rays emitted from the optical hole to form parallel light. A diaphragm 60 is provided at the light outlet of the collimator 50, and the diaphragm 60 can limit the beam of the characteristic X-rays collimated into parallel light
[0054] In one embodiment, the K-fluorescent radiation device further includes a catcher. The catcher 70 is arranged behind the radiator 22 along the irradiation direction of the X-ray beam, and the catcher 70 is used to capture the rays leaking through the radiator 22. Specifically, in this embodiment, the catcher 70 is arranged in the shielding box 40
[0055] It can be understood that in other embodiments, the K-fluorescent radiation device can also have other structures, as long as it has a radiator 22 and can generate characteristic X-rays
[0056] Step S130: Experimentally measure the K of the radiator 22 α and K β The intensities of the characteristic X-rays, and obtain the intensity ratio L through detection efficiency correction mea .
[0057] Specifically, use a detector to experimentally measure the K generated by the radiator 22 in the K-fluorescent radiation device α , K β The energy spectra of the characteristic X-rays, and calculate the experimentally obtained K according to the experimentally measured energy spectra α and Kβ The intensity i of the characteristic X-ray α 、i β 。
[0058] Then, the above experiment K α and K β The intensity i of the characteristic X-ray α 、i β , divided by the detection efficiency of the detector at the corresponding energy in step S110, to obtain the corrected K α and K β The intensity i of the characteristic X-ray α修正 、i β修正 , and the intensity ratio L mea , where L mea =i α修正 / i β修正 。
[0059] Step S140: Replace the radiator 22 in the K fluorescence radiation device, and calculate multiple groups of intensity ratios L mc and intensity ratio L mea 。
[0060] Specifically, the radiator 22 replaced in the K fluorescence radiation device can generate characteristic X-rays with different energies to obtain different intensity ratios L mea 。After replacing the radiator 22 in the K fluorescence radiation device, repeat step S120 to obtain a new intensity ratio L mc 。Then repeat step S130 to obtain a new intensity ratio L mea , so each radiator 22 corresponds to a group of intensity ratios L mc and intensity ratio L mea 。By replacing multiple radiators 22, multiple groups of intensity ratios L mc and intensity ratio L mea can be obtained. In one embodiment, the number of radiators 22 replaced can be specifically set according to the needs of the experiment, such as 3, 5, or 10, etc.
[0061] Step S150: Determine whether the error between each group of intensity ratios L mc and intensity ratio L mea is less than the preset value.
[0062] Specifically, compare the intensity ratio L mc with the intensity ratio L mea to determine whether the error meets the requirements, and it can verify the K α 、K βThe accuracy of the detector efficiency curve of the Monte Carlo simulation under the energy corresponding to the characteristic X-ray. In one embodiment, the specific selection of the preset value can be specifically set according to the accuracy that the detection efficiency needs to achieve. For example, the preset value can be the intensity ratio L mc 3%.
[0063] Step S160: If not, adjust the crystal size and dead zone thickness of the detector.
[0064] Specifically, if the intensity ratio L mc Ratio to intensity L mea If the error is not less than the preset value, it means that the detector efficiency curve of the Monte Carlo simulation is not accurate enough and the parameters of the detector need to be adjusted. In one embodiment, the crystal size and dead zone thickness of the detector are specifically adjusted.
[0065] Then, repeat the steps S110 to S160, re-perform the Monte Carlo simulation, obtain the detection efficiency of the new detector for parallel beam X-rays of different energies, and then obtain new sets of intensity ratios L mc and intensity ratio L mea , determine the new intensity ratio L mc Ratio to intensity L mea Is the error less than the preset value until each new set of experiments and the corrected intensity ratio L mea The intensity ratio L of the new Monte Carlo simulation mc The error is within the allowable range. At this point, the calculation is terminated, and the appropriate results of the detector's detection efficiency for parallel beam X-rays of different energies are obtained, completing the detector detection efficiency calibration.
[0066] The calibration method of the above detector detection efficiency is compared with the K calculated by Monte Carlo simulation method. α , K β The intensity ratio of characteristic X-rays L mc , and the experimental and corrected intensity ratio L mea , to verify the accuracy of the detection efficiency of the detector for parallel beam X-rays of different energies obtained by the Monte Carlo simulation method, thereby obtaining the detection efficiency of the detector for parallel beam X-rays of different energies. The detection efficiency of the detector can be calibrated quickly and accurately, avoiding the shortcomings of the standard source experimental calibration method due to the limitations of the radiation source itself and the environment, and the Monte Carlo simulation calibration method due to the inability to obtain accurate detector parameters, which leads to large efficiency calibration deviations.
[0067] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0068] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications, substitutions, and improvements can be made, and these should all be covered within the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the claims.
Claims
1. A calibration method for the detection efficiency of a detector, characterized in that, It includes the following steps: Using the Monte Carlo simulation method, obtain the detection efficiency of the detector for X-rays with different energies; Using the Monte Carlo simulation method, calculate the intensity ratio L of the K α , K β characteristic X-rays generated by the radiator in the K fluorescence radiation device mc ; Experimentally measure the K of the radiator α and K β of the characteristic X-ray intensity i α 、i β , and obtain the intensity ratio L through the correction of the detection efficiency mea , the step of obtaining the intensity ratio L through the correction of the detection efficiency mea is specifically as follows: Divide the K α and K β of the characteristic X-ray intensity i α 、i β obtained from the experiment by the detection efficiency corresponding to the energy of the detector to obtain the corrected K α and K β of the characteristic X-ray intensity i α修正 、i β修正 , and calculate to obtain the intensity ratio L mea , where L mea =i α修正 / i β修正 ; Replace the radiator in the K fluorescence radiation device to generate characteristic X-rays with different energies, and calculate multiple groups of intensity ratios L according to the above steps mc and the intensity ratio L mea ; Determine the intensity ratio L of each group mc and the intensity ratio L mea to check if the error is less than a preset value; If not, adjust the crystal size and dead layer thickness of the detector; Repeat the above steps until the error between each group of the intensity ratio L mc and the intensity ratio L mea is less than the preset value.
2. The calibration method for the detection efficiency of the detector according to claim 1, characterized in that, The step of using the Monte Carlo simulation method to obtain the detection efficiency of the detector for X-rays with different energies is specifically as follows: According to the crystal size and dead layer thickness parameters of the detector, use the Monte Carlo simulation method to calculate the detection efficiency of the detector for X-rays with different energies.
3. The calibration method for the detection efficiency of the detector according to claim 1, characterized in that The method using Monte Carlo simulation to calculate the intensity ratio L of K α and K β characteristic X-rays generated by the radiator in the K fluorescence radiation device is specifically as follows: mc Provide a K fluorescence radiation device, and use the Monte Carlo simulation method to calculate the K α and K β intensities I of characteristic X-rays α and I β to obtain an intensity ratio L mc where L mc = I α / I β .
4. The calibration method for the detection efficiency of the detector according to claim 1, characterized in that, The experiment measures K of the radiator α and K β The steps for measuring the intensity of characteristic X-rays are specifically as follows: Experimentally measure the K α , K β characteristic X-ray energy spectra generated by the radiator in the K fluorescence radiation device, and calculate the obtained K α and K β characteristic X-ray intensities i α , i β .
5. The calibration method for the detection efficiency of the detector according to claim 1, characterized in that, The K-fluorescence radiation device includes: An X-ray machine for generating X-rays; A K-fluorescence generating device, including a support and a radiator provided on the support, the radiator receiving the X-rays and exciting characteristic X-rays; and A detection device for measuring the energy spectrum of the characteristic X-rays.
6. The calibration method for the detection efficiency of the detector according to claim 5, characterized in that The K-fluorescence radiation device further includes a shielding box, the X-ray machine and the K-fluorescence generating device are housed in the shielding box, the shielding box is provided with a light hole for the characteristic X-rays to pass through, and the detection device is arranged opposite to the light hole.
7. The calibration method for the detection efficiency of the detector according to claim 6, characterized in that The K-fluorescence radiation device further includes a collimator, the collimator is installed outside the shielding box, the collimator is coaxially arranged with the light hole, and a diaphragm is provided at the light outlet of the collimator.
8. The calibration method for the detection efficiency of the detector according to claim 5, characterized in that, It further includes a trap, the trap is arranged behind the radiator along the irradiation direction of the X-ray beam to capture the rays leaking through the radiator.