CN115856994B - Efficiency calibration method, device and system of gamma detector - Google Patents
Efficiency calibration method, device and system of gamma detector Download PDFInfo
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Abstract
The embodiment of the invention provides a method, a device and a system for calibrating the efficiency of a gamma detector, which relate to the field of radiation detection, and the method comprises the following steps: acquiring the full-energy peak detection efficiency of a gamma detector for detecting a reference radioactive source; according to the method for calculating the total detection probability of the radioactive source, which is provided by the invention, the reference total detection probability of the reference radioactive source and the sample total detection probability of the sample radioactive source are calculated respectively; and determining the full-energy peak detection efficiency of the gamma detector for detecting the sample radioactive source according to the total detection probability of the sample, the reference total detection probability and the full-energy peak detection efficiency of the reference radioactive source. The method can improve the accuracy of efficiency calibration, has simple calibration process, does not need strict characterization of the detector, and is suitable for radioactive sources with any shape.
Description
Technical Field
The present invention relates to the field of radiation detection, and in particular, to a method, apparatus, and system for calibrating efficiency of a gamma detector.
Background
Gamma detectors (also known as gamma spectrometers) are one of the most widely used instruments in radiation detection. In radionuclide activity measurements, efficiency calibration (efficiency calibration) of the gamma detection system used is required. The method for calibrating the efficiency of the gamma detector mainly comprises the following steps:
1, typically, the efficiency calibration of a gamma detector is determined using standard source energy spectrum measurements of known activity. However, when the geometry and material of the sample source (i.e., the radiation source to be measured) is very different from that of the standard source, it is not a simple matter for most of the relevant workers to re-find the appropriate standard source for calibration. If the measurement is made directly without recalibration, a large error is caused.
2, efficiency calibration is performed using the monte carlo method. This requires a knowledge of the Monte Carlo procedure and a detailed description of the detector and sample source. However, the accuracy of this method is low due to the difficulty in precisely describing the crystalline dead layer and the like.
And 3, performing efficiency calibration in a passive efficiency calibration mode. For example, the detection efficiency of any sample source is calculated using passive efficiency calibration software such as LabSOCS and Gamma Calib. However, the gamma detector used for measurement must pass rigorous characterization, and uncharacterized gamma detectors cannot use these passive efficiency calibration software.
And 4, detecting an efficiency transfer method. For example, the efficiency transfer method proposed by L.Moens et al. The method is suitable for efficiency calibration of various gamma detectors, has the characteristics of high accuracy, no need of strict factory characterization of the detectors, and the like, and can only calculate a point source and a cylinder source with the radius of the radioactive source smaller than that of the detectors by the initial version SOLANG, and calculate a cylinder source and a Ma Linbei source with any radius by the advanced version ANGLE. ANGEL assumes that the source is a point source, a cylinder source, or Ma Linbei source placed directly above the detector, etc. coaxial with the detector, and its calculation method is based on the concept of an effective solid angle. The calculation method needs to describe the solid angle of a certain volume element in the radioactive source to a certain micro element on the surface of the detector, and then multiple integration is carried out on the surface of the detector and the volume of the radioactive source to obtain the geometric solid angle of the radioactive source to the detector. And adding an attenuation factor and an efficiency factor into the multiple integral expression, so as to obtain the multiple integral expression of the effective solid angle. The effective solid angle of the radiation source to the detector is then calculated using Gao Sile let-down integration, and finally the ratio of the effective solid angles of the two radiation sources to the detector is used to shift the full-energy peak detection efficiency. This method well describes the geometry of the point source, cylinder source and Ma Linbei source and the photon attenuation and detector response, but its latest version ANGLE4 has so far been applicable only to point source, cylinder source and Ma Linbei source, because of the limitations of the mathematical method used. In other words, this method is not yet suitable for efficiency calibration of any shape of radiation source.
Thus, existing methods of efficiency calibration suffer from one or more of the following problems: the calibration process is complex, the accuracy is low, the detector cannot be calibrated when not subjected to strict characterization, and the method is not suitable for efficiency calibration of radioactive sources with any shape.
Disclosure of Invention
In view of the above, the present invention aims to provide a method, an apparatus and a system for calibrating efficiency of a gamma detector, which can improve accuracy of efficiency calibration, and has a simple calibration process, and the detector does not need to be precisely characterized, and is suitable for any shape of radioactive source.
In order to achieve the above object, the technical scheme adopted by the embodiment of the invention is as follows:
in a first aspect, the present invention provides a method for calibrating efficiency of a gamma detector. The method of the first aspect comprises the following steps: acquiring the full-energy peak detection efficiency of the target energy gamma rays emitted by the gamma detector detection reference radioactive source; respectively acquiring the reference total detection probability of the reference radioactive source and the sample total detection probability of the sample radioactive source according to the calculation method of the total detection probability of the radioactive source; determining the total peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source according to the total detection probability of the sample, the reference total detection probability and the total peak detection efficiency of the reference radioactive source; the method for calculating the total detection probability of the radioactive source comprises the following steps: dividing the radiation source into a plurality of point sources; the radioactive source comprises a reference radioactive source or a sample radioactive source; determining a plurality of gamma rays emitted by each point source in the plurality of point sources to obtain a gamma ray set; determining the detection probability of each gamma ray in the gamma ray set detected by the gamma detector to obtain a plurality of detection probabilities; and determining the total detection probability of gamma rays emitted by the radioactive source detected by the gamma detector according to the detection probabilities.
In a second aspect, the present invention provides an efficiency calibration apparatus for a gamma detector, comprising: the device comprises a measurement module, an input module and a processing module; the measuring module is used for collecting energy spectrums of the reference radioactive source and the sample radioactive source, and analyzing and calculating the full-energy peak detection efficiency of the reference radioactive source. The input module is used for receiving model information of the gamma detector, the reference radioactive source and the sample radioactive source; the input module is also used for receiving the full-energy peak detection efficiency of the target energy gamma rays emitted by the gamma detector detection reference radioactive source; the processing module is used for respectively acquiring the reference total detection probability of the reference radioactive source and the sample total detection probability of the sample radioactive source according to the calculation method of the total detection probability of the radioactive source; the processing module is also used for determining the total peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source according to the total detection probability of the sample, the reference total detection probability and the total peak detection efficiency of the reference radioactive source; the method for calculating the total detection probability of the radioactive source comprises the following steps: the processing module is also used for dividing the radioactive source into a plurality of point sources; the radioactive source comprises a reference radioactive source or a sample radioactive source; the processing module is also used for determining a plurality of gamma rays emitted by each point source in the plurality of point sources to obtain a gamma ray set; the processing module is also used for determining the detection probability of each gamma ray in the gamma ray set detected by the gamma detector to obtain a plurality of detection probabilities; and the processing module is also used for determining the total detection probability of gamma rays emitted by the radioactive source detected by the gamma detector according to the detection probabilities.
In a third aspect, the present invention provides a gamma detection system, comprising a gamma detector and a host computer, the gamma detector being connected to the host computer, the host computer comprising a processor connected to a memory, the processor being configured to execute a computer program in the memory, such that the method of the first aspect is performed.
In a fourth aspect, the invention provides a computer readable storage medium comprising a computer program which, when run on a computer, causes the method of the first aspect to be performed.
Compared with the existing efficiency calibration method, in the efficiency calibration method of the gamma detector provided by the embodiment of the invention, the radioactive source is divided into a plurality of point sources, then the detection probability of each gamma ray emitted by each point source is determined, and the total detection probability of the radioactive source is determined according to the detection probability of each gamma ray. In other words, the method starts from a single gamma ray to perform efficiency calibration, avoids multiple integral of the three angles, simplifies the efficiency calibration process and reduces the calculated amount. In the scheme, the total energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source is determined according to the total detection probability of the sample, the reference total detection probability and the total energy peak detection efficiency of the reference radioactive source. In other words, the efficiency of detecting the full-energy peak of the sample radioactive source is calculated in an efficiency transfer mode, so that efficiency calibration is realized, strict factory characterization is not needed in the process, and the method is suitable for calibrating the efficiency of batch gamma detectors. In addition, the method is not limited to the shape of the radioactive source, so that the method can rapidly and accurately calculate the total detection probability of gamma photons of specific energy of the radioactive source with any shape by the gamma detector, further realize the efficiency transfer calculation of the radioactive source with any shape, and has the characteristics of no limitation of the geometric shape and the position of the radioactive source, high calculation speed, high accuracy and the like.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments of the present invention will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and should not be considered as limiting the scope, and other related drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a gamma detection system according to an embodiment of the present invention;
fig. 2 is a flow chart of a method for calibrating efficiency of a gamma detector according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a specific flow of S120 in FIG. 2;
FIG. 4 is a simplified two-dimensional geometric model schematic of a gamma detector and a radiation source according to an embodiment of the present invention;
FIG. 5 is a schematic view of the source of FIG. 4 divided into cells;
FIG. 6 is a schematic diagram of L line segments extending uniformly around a certain cell in FIG. 5;
FIG. 7 is a schematic diagram illustrating the distance between two adjacent intersections of a gamma ray in FIG. 6;
fig. 8 is a functional block diagram of an efficiency calibration device for a gamma detector according to an embodiment of the present invention.
Reference numerals illustrate: a 100-gamma detection system; a 110-gamma detector; 120-an upper computer; 130-a radioactive source; an efficiency calibration device of the 200-gamma detector; 210-an input module; 220-a processing module; 230-an output module; 240-measurement module.
Description of the embodiments
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
Furthermore, the terms "first," "second," and the like, if any, are used merely for distinguishing between descriptions and not for indicating or implying a relative importance.
It should be noted that the features of the embodiments of the present invention may be combined with each other without conflict.
The embodiment of the invention provides a technical scheme, which comprises a method, a device and a system for calibrating the efficiency of a gamma detector. The technical scheme provided by the invention will be described below with reference to the accompanying drawings.
First, a gamma detection system provided by the embodiment of the present invention is described. Referring to fig. 1, fig. 1 is a schematic diagram of a gamma detection system according to an embodiment of the invention. The gamma detection system 100 includes a radiation source 130, a gamma detector 110, and a host computer 120. The gamma detector 110 is connected to the host computer 120. The upper computer 120 is provided with efficiency calibration software, which can be used to execute the efficiency calibration method of the gamma detector provided by the embodiment of the invention. The radiation source 130 may include a reference radiation source or a sample radiation source. In an alternative embodiment, the gamma detection system 100 further comprises a multi-channel analyzer.
The gamma detector 110 may include a semiconductor detector or a scintillator detector, which is not limited thereto. The upper computer 120 may include a processor connected to a memory for executing a computer program in the memory, so that an efficiency calibration method (see below for details) of the gamma detector provided by the embodiment of the present invention is performed.
In alternative embodiments, the host computer 120 includes, but is not limited to: personal computers, servers, notebook computers, desktop computers, tablet computers, and the like.
On the basis of the gamma detection system 100 shown in fig. 1, the embodiment of the present invention further provides an efficiency calibration method of a gamma detector, which can be applied to the gamma detection system 100 and can be executed by the host computer 120 of the gamma detection system 100. Referring to fig. 2, fig. 2 is a flow chart of a method for calibrating efficiency of a gamma detector according to an embodiment of the invention.
The method for calibrating the efficiency of the gamma detector may include the following steps S110 to S130, which are respectively described below.
S110, acquiring the full-energy peak detection efficiency of the target energy gamma rays emitted by the gamma detector detection reference radioactive source.
The global peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the reference radioactive source can be determined through experimental measurement, for example, the global peak detection efficiency of the specific energy gamma rays of the reference radioactive source is obtained through experimental measurement. In other words, the total peak detection efficiency of the reference radiation source may be a value obtained by performing experimental measurement on the reference radiation source in advance.
In alternative embodiments, the gamma detector comprises a semiconductor detector or a scintillator detector.
S120, respectively acquiring the reference total detection probability of the reference radioactive source and the sample total detection probability of the sample radioactive source according to the calculation method of the total detection probability of the radioactive source.
In an alternative embodiment, the method for calculating the total detection probability of the radiation source includes the following steps 1.1 to 1.4:
step 1.1, dividing a radioactive source into a plurality of point sources; the radiation source includes a reference radiation source or a sample radiation source.
And 1.2, determining a plurality of gamma rays emitted by each point source in the plurality of point sources to obtain a gamma ray set.
And 1.3, determining the detection probability of each gamma ray in the gamma ray set detected by the gamma detector, and obtaining a plurality of detection probabilities.
And 1.4, determining the total detection probability of gamma rays emitted by the radioactive source detected by the gamma detector according to the detection probabilities.
The following describes the steps 1.1 to 1.4 in detail with reference to fig. 3. Referring to fig. 3, fig. 3 is a specific flowchart of S120 in fig. 2. S120 includes the following steps S121A-S124B:
S121A, dividing the sample radioactive source into N 1 Point sources of samples, N 1 Is a positive integer.
It will be appreciated that in embodiments of the present invention, the sample radiation source is divided into N 1 Means for providing a point source of each sample include, but are not limited to: evenly dividing the sample radioactive source into N 1 The sample point sources or the sample radioactive sources are randomly divided into N 1 Sample point sources, etc.
In an alternative embodiment, S121A, the sample radiation source is divided into N 1 A plurality of sample point sources comprising: evenly dividing the sample radioactive source into N 1 And (3) sample point sources. Specifically, the Monte Carlo sampling method can be utilized to randomly divide the sample radioactive source into N 1 And (3) sample point sources.
S122A, determining N 1 L gamma rays emitted by each sample point source in the sample point sources are obtained to obtain N 1 And X L gamma rays, wherein L is a positive integer.
The sample point source emits gamma photons to the space by taking the sample point source as a center, and each gamma photon can be correspondingly understood as a gamma ray. Thus, a single point source emits multiple gamma rays around. In alternative embodiments, gamma rays may be directed through a point-to-point (i.e.
) Is described, wherein the end point coordinates (i.e., the position coordinates of the sample point source) are (x) 0 ，y 0 ，z 0 ) The direction is v= (a, b, c).
In an alternative embodiment, L is an integer multiple of 1000.
S123A, determining N 1 The detection probability of each gamma ray in the X L gamma rays detected by the gamma detector is obtained to obtain N 1 X L detection probabilities.
Wherein, N is 1 The ith gamma ray (i is greater than 0 and less than or equal to N) 1 X L) is an integer, the detection probability of the ith gamma ray detected by the gamma detector is related to whether it passes through the working medium in the gamma detector and the medium passed before passing through the working medium in the gamma detector. Therefore, the detection probability of the ith gamma ray detected by the gamma detector is determined by the attenuation coefficient of the working medium of the gamma detector, the path length of the ith gamma ray passing through the working medium of the gamma detector, and the jth non-working path of the ith gamma ray passing throughThe attenuation coefficient of the medium, the path length of the ith gamma ray through the jth non-working medium.
It can be understood that if the ith gamma ray does not pass through the working medium in the gamma detector, the detection probability of the ith gamma ray detected by the gamma detector is 0.
Optionally, in S123A, N is determined 1 The detection probability of each gamma ray in the x L gamma rays detected by the gamma detector includes: n is determined using the following formula 1 Detection probability of each gamma ray in the x L gamma rays detected by the gamma detector:
wherein, the liquid crystal display device comprises a liquid crystal display device,
is N 1 The detection probability of the ith gamma ray in the X L gamma rays detected by the gamma detector is that i is more than 0 and less than or equal to N 1 X L integer>
For the attenuation coefficient of the working medium of the gamma detector, D is the path length of the ith gamma ray through the working medium in the gamma detector, +.>
Attenuation coefficient of j-th non-working medium for passing the ith gamma ray, +.>
The path length of the ith gamma ray passing through the jth non-working medium is j, and j is a positive integer.
It should be noted that the number of the substrates,
the path length of the ith gamma ray passing through the jth non-working medium specifically comprises:
is the ith gamma ray onThe path length of one or more non-working media previously passed by the working media in the overgamma detector.
It can be understood that in S121A to S123A, efficiency calibration is performed from a single gamma ray (also referred to as a single gamma photon), so that multiple integral of the three angles is avoided, the efficiency calibration process is simplified, and the calculation amount is reduced.
S124A, according to N 1 And determining the total detection probability of the sample, which is detected by the gamma detector, of the gamma rays emitted by the sample radioactive source.
Wherein, after S124A, a detection probability of each gamma ray detected by the gamma detector is calculated. The total detection probability of the sample (denoted as P) can be determined according to the following formula:
. In other words, the total detection probability of the sample is a value obtained by summing the detection probabilities of all gamma rays detected by the gamma detector and averaging them.
With continued reference to FIG. 3, S121B, the reference radiation source is divided into N 2 Reference point sources, N 2 Is a positive integer.
S122B, determining N 2 L gamma rays emitted by each reference point source in the reference point sources are obtained to obtain N 2 And X L gamma rays, wherein L is a positive integer.
S123B, determining N 2 The detection probability of each gamma ray in the X L gamma rays detected by the gamma detector is obtained to obtain N 2 X L detection probabilities.
S124B, according to N 2 And determining the reference total detection probability of gamma rays emitted by the reference radioactive source detected by the gamma detector.
The implementation principle of S121B to S124B is similar to that of S121A to S124A, and detailed implementation process and effect of S121B to S124B and reference to S121A to S124A are not repeated here.
In alternative embodiments, the reference radiation source is an arbitrarily shaped radiation source. Specifically, the reference radiation source is a point source. Therefore, the calculated amount of S121B-S124B can be reduced, and the efficiency calibration efficiency is improved.
S130, determining the total peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source according to the total detection probability of the sample, the reference total detection probability and the total peak detection efficiency of the reference radioactive source.
After S130, the method further comprises: and (5) calibrating the efficiency of the gamma detector by utilizing the full-energy peak detection efficiency of the sample radioactive source.
It can be appreciated that S130 is equivalent to calculating the total energy peak detection efficiency of the sample radiation source by using the efficiency transfer method, thereby simplifying the efficiency calibration process and reducing the calculation amount.
Optionally, in S130, determining the total peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radiation source according to the total detection probability of the sample, the reference total detection probability and the total peak detection efficiency of the reference radiation source includes: the total energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source is determined by the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,
for the total peak detection efficiency of the sample radiation source, < >>
To reference the full energy peak detection efficiency of the radiation source,
for the total detection probability of the sample, +.>
Is the reference total detection probability.
In S110 to S130, the energy of the gamma rays emitted from the reference radiation source is the same as the energy of the gamma rays emitted from the sample radiation source.
The method for calculating the total detection probability of the radioactive source further comprises the following steps 2.1-2.8.
Step 2.1, dividing the radioactive source into M point sources, M being a positive integer and M being smaller than N 1 And N 2 . The radiation source may be a reference radiation source or a sample radiation source.
Alternatively, M may be set when step 2.1 is performed for the first time, such as m=500.
And 2.2, determining L gamma rays emitted by each point source in the M point sources to obtain M multiplied by L gamma rays, wherein L is a positive integer.
And 2.3, determining the detection probability of each gamma ray in the M multiplied by L gamma rays detected by the gamma detector, and obtaining M multiplied by L detection probabilities.
And 2.4, determining a first total detection probability that the gamma rays emitted by the radioactive source are detected by the gamma detector according to the M multiplied by L detection probabilities.
The implementation principle of the steps 2.1 to 2.4 is similar to that of the steps S121A to S124A, and the specific implementation process and effect of the steps 2.1 to 2.4 are not described herein again with reference to the steps S121A to S124A.
Step 2.5, dividing the radioactive source into 2M point sources, repeating the steps 2.1-2.4 to obtain 2M multiplied by L detection probabilities, and determining a second total detection probability of gamma rays emitted by the radioactive source detected by the gamma detector according to the 2M multiplied by L detection probabilities;
it will be appreciated that in steps 2.1-2.5, 2M is twice as large as M, and therefore, it is equivalent to further finely dividing the radiation source and calculating the total detection probability of the radiation source (i.e., calculating the second total detection probability).
And 2.6, determining the relative error of the second total detection probability according to the difference value of the first total detection probability and the second total detection probability.
And 2.7, if the relative error is smaller than a preset threshold value, determining the second total detection probability as the total detection probability of the radioactive source.
Step 2.8, if the relative error is greater than or equal to the preset threshold, increasing the value of M and returning to step 2.1.
In the above steps 2.6 to 2.8, for example, assuming that the total detection probability calculated for the first time is denoted as P (i.e., the first total detection probability), and the total detection probability calculated for the second time is denoted as P (i.e., the second total detection probability), the difference between the total detection probability calculated for the first time and the total detection probability calculated for the second time is |p-p|. The relative error of the total detection probability of the sample calculated for the second time can be: P-P/P. In this example, assuming that the preset threshold is 0.01, if |p-p|/P is smaller than 0.01, step 2.7 is performed to determine the second total detection probability as the total detection probability, that is, output p=p; if |P-P|/P| is greater than or equal to 0.01, then step 2.8 is performed, the value of M is increased, and step 2.1 is performed back. In this way, the relative error of the total detection probability of the radioactive source can be made smaller, thereby obtaining better accuracy. Wherein, optionally, increasing the value of M may include: m is amplified 2-fold each time step 2.8 is performed.
In order to more clearly illustrate the above method embodiments, the method embodiments are further described below in connection with specific implementation principles. In one example, the above method embodiment may include the following steps:
step 3.1 referring to fig. 4, fig. 4 is a simplified two-dimensional geometric model schematic diagram of a gamma detector and a radiation source according to an embodiment of the present invention. First, geometric models of gamma detectors (including detector crystals, dead layers, cold fingers, detector housings) and radioactive sources (which may be reference radioactive sources or sample radioactive sources) and the like, respectively, may be created in a spatial rectangular coordinate system. Optionally, other absorbers, containers, etc. may be added (i.e., positioned) between the radiation source and the gamma detector.
In step 3.2, as shown in fig. 5, the radioactive source can be uniformly divided into N cells, and each cell is treated as a point source (i.e., a reference point source or a sample point source). Then, as shown in fig. 6, L line segments (which may be considered as paths of gamma photons) of length K may extend uniformly around each point source, K should be greater than the distance of the point source to the far end of the gamma detector.
Wherein the ith line segment in the L line segments can use a straight line point direction type
To describe. Wherein the end point coordinates (i.e., point source coordinates) of the ith line segment are (x) 0 ，y 0 ，z 0 ) The direction is v= (a, b, c). In addition, the geometric surfaces of the gamma detector and the radiation source can be represented by corresponding curved functions. Therefore, whether the intersection point exists between the ith line segment and the geometric surface can be judged through whether the intersection point exists between the curved surface function and the linear function where the ith line segment exists.
Step 3.3, take the ith line segment as an example. If the ith line segment has no intersection point with the working medium geometric interface of the gamma detector, skipping the line segment and calculating the next line segment as shown in fig. 7; if the ith line segment has an intersection point with the working medium geometric interface of the gamma detector, determining the intersection point of the ith line segment and any other geometric interface, and calculating the distance between any two adjacent intersection points, wherein the calculation formula is as follows:
. If the distance between two adjacent intersection points passes through the working medium of the gamma detector, the distance is marked as D; if the distance between two adjacent crossing points does not pass through the working medium, it is marked +.>
。
Step 3.4, for a randomly emitted gamma photon in the radiation source, the probability of being detected by the detector is
. Wherein (1)>
The detection probability of the ith gamma ray in the L multiplied by N gamma rays detected by the gamma detector is represented by the formula, i is an integer which is more than 0 and less than or equal to L multiplied by N, and +.>
For the attenuation coefficient of the working medium of the gamma detector, D is the path length of the ith gamma ray through the working medium in the gamma detector, +.>
Attenuation coefficient of j-th non-working medium for passing the ith gamma ray, +.>
For the path length of the ith gamma ray through the jth non-working medium, j is an integer greater than 0.
And 3.5, calculating the probability of each gamma photon detected by the gamma detector through the steps 3.1-3.4, and obtaining L multiplied by N detection probabilities. These probabilities are then summed and averaged to obtain a total detection probability for a gamma photon of a particular energy emitted by the radiation source to be detected by the gamma detector:
. It will be appreciated that this expression is valid for any type of radiation source and gamma detector and can be used to determine the total detection probability calculation for any radiation source-gamma detector system.
Step 3.6, firstly, uniformly dividing the radioactive source into 2N cells to obtain 2LN gamma photons, and repeating the calculation process of step 3.3-step 3.5 to obtain a new total detection probability P. Then, it is judged whether or not |P-P|/P| is smaller than 0.01. Specifically, if |p-p|/P is less than 0.01, p=p is output at this time
The method comprises the steps of carrying out a first treatment on the surface of the If |P-P|/P > 0.01, the source is further subdivided and step 3.6 is performed again until |P-P|/P < 0.01, after repeating multiple times (e.g., x times), the source is further subdivided>
. In this way, better accuracy can be obtained.
Step 3.7, according to the above stepsRespectively calculating total detection probability P of the gamma detector on the reference source and the sample source Reference to And P, and experimentally measuring the detection efficiency epsilon of gamma photons of specific energy emitted by the gamma detector to the reference radioactive source Reference to Then, according to the efficiency transfer formula
The detection efficiency of the gamma detector for emitting gamma photons with specific energy to the sample radioactive source can be calculated.
It should be appreciated that in the above method embodiments, by dividing the radiation source into a plurality of point sources, then determining the probability of detection of each gamma ray emitted by each point source, and determining the total probability of detection of the radiation source based on the probability of detection of each gamma ray. In other words, the method starts from a single gamma ray to perform efficiency calibration, avoids multiple integral of the three angles, simplifies the efficiency calibration process and reduces the calculated amount. In addition, in the scheme, the total detection efficiency of the sample radiation source for detecting the gamma rays emitted by the sample radiation source by the gamma detector is determined according to the total detection probability of the sample, the total detection probability of the reference and the total peak detection efficiency of the reference radiation source. In other words, the efficiency of detecting the full-energy peak of the sample radioactive source is calculated in an efficiency transfer mode, so that efficiency calibration is realized, strict factory characterization is not needed in the process, and the method is suitable for calibrating the efficiency of batch gamma detectors. In addition, the method is not limited to the shape of the radioactive source, so that the method can rapidly and accurately calculate the total detection probability of gamma photons of specific energy of the radioactive source with any shape by the gamma detector, further realize the efficiency transfer calculation of the radioactive source with any shape, and has the characteristics of no limitation of the geometric shape and the position of the radioactive source, high calculation speed, high accuracy and the like.
Optionally, the embodiment of the method provided by the invention can be further applied to the self-attenuation correction corresponding to any radiation source geometry in an expanding manner.
In order to perform the foregoing embodiments and the corresponding steps in each possible manner, an implementation manner of an efficiency calibration device for a gamma detector is given below, referring to fig. 8, fig. 8 is a functional block diagram of an efficiency calibration device 200 for a gamma detector according to an embodiment of the present invention. The gamma detector efficiency calibration apparatus 200 may be used to implement the method shown in fig. 2 and may be used to perform the steps that the upper computer 120 is capable of performing in the method embodiments described above. It should be noted that, the basic principle and the technical effects of the efficiency calibration device 200 for a gamma detector provided in this embodiment are the same as those of the above embodiment, and for brevity, reference should be made to the corresponding contents of the above embodiment. The efficiency calibration apparatus 200 of the gamma detector may include: a measurement module 240, an input module 210, a processing module 220, and an output module 230.
Alternatively, the above modules may be stored in a memory in the form of software or Firmware (Firmware) or be solidified in an Operating System (OS) of the upper computer 120 shown in fig. 1 and executed by a processor in the upper computer 120 shown in fig. 1. Meanwhile, data, codes of programs, and the like required to execute the above-described modules may be stored in the memory.
It will be appreciated that the measurement module 240, the input module 210, the processing module 220, and the output module 230 may be configured to support the upper computer 120 shown in fig. 1 to perform the steps associated with the method embodiments described above, and/or other processes for the techniques described herein, such as the method embodiments shown in fig. 2 and the various method embodiments described above, which are not limited thereto. In addition, the input module 210 is configured to receive model information of the gamma detector, the reference radiation source, and the sample radiation source. The output module 230 may also be used to output the sample radiation source detection efficiency. The measurement module 240 is used for collecting energy spectrums of the reference radioactive source and the sample radioactive source, and analyzing and calculating the full-energy peak detection efficiency of the reference radioactive source.
Based on the above method embodiments, the present invention further provides a computer readable storage medium, on which a computer program is stored, which when executed by a processor performs the steps of the above method for calibrating the efficiency of a gamma detector.
Specifically, the storage medium may be a general-purpose storage medium, such as a mobile magnetic disk, a hard disk, or the like, and when a computer program on the storage medium is executed, the method in the foregoing embodiment can be executed, so as to solve "the existing efficiency calibration method has one or more of the following problems: the calibration process is complex, the accuracy is low, the calibration cannot be performed without strict characterization, and the calibration method is not suitable for the efficiency calibration of the radioactive source with any shape, so that the accuracy of the efficiency calibration can be improved, the calibration process is simple, the strict characterization is not needed, and the calibration method is suitable for the radioactive source with any shape.
The above description is only an example of the present invention and is not intended to limit the scope of the present invention, and various modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A method of calibrating the efficiency of a gamma detector, the method comprising:
acquiring the full-energy peak detection efficiency of the target energy gamma rays emitted by the gamma detector detection reference radioactive source;
respectively acquiring the reference total detection probability of the reference radioactive source and the sample total detection probability of the sample radioactive source according to a calculation method of the total detection probability of the radioactive source;
determining the total energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source according to the total detection probability of the sample, the reference total detection probability and the total energy peak detection efficiency of the reference radioactive source;
the method for calculating the total detection probability of the radioactive source comprises the following steps:
dividing the radiation source into a plurality of point sources; the radiation source includes the reference radiation source or the sample radiation source;
determining a plurality of gamma rays emitted by each point source in the plurality of point sources to obtain a gamma ray set;
determining the detection probability of each gamma ray in the gamma ray set detected by the gamma detector to obtain a plurality of detection probabilities;
determining the total detection probability of gamma rays emitted by the radioactive source detected by the gamma detector according to the detection probabilities;
the determining the total energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source according to the total detection probability of the sample, the reference total detection probability and the total energy peak detection efficiency of the reference radioactive source comprises the following steps:
the total energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source is determined by the following formula:
wherein (1)>
Detection efficiency for the total peak of said sample radiation source,/->
For the full energy peak detection efficiency of the reference radiation source, and (2)>
For the total detection probability of the sample, +.>
And the reference total detection probability.
2. The method of claim 1, wherein dividing the radiation source into a plurality of point sources comprises:
dividing the sample radiation source into N 1 Point sources of samples, N 1 Is a positive integer; and dividing the reference radiation source into N 2 Reference point sources, N 2 Is a positive integer;
determining a plurality of gamma rays emitted by each of the plurality of point sources to obtain a gamma ray set, including:
determining the N 1 L gamma rays emitted by each sample point source in the sample point sources are obtained to obtain N 1 X L gamma rays, L being a positive integer; and determining the N 2 L gamma rays emitted by each reference point source in the reference point sources are obtained to obtain N 2 X L gamma rays, L being a positive integer;
determining the detection probability of each gamma ray in the gamma ray set detected by the gamma detector to obtain a plurality of detection probabilities, wherein the method comprises the following steps:
determining the N 1 The detection probability of each gamma ray in the X L gamma rays detected by the gamma detector is obtained to obtain N 1 X L detection probabilities; and determining the N 2 The detection probability of each gamma ray in the X L gamma rays detected by the gamma detector is obtained to obtain N 2 X L detection probabilities;
determining, from the plurality of detection probabilities, a total detection probability of gamma rays emitted by the radiation source detected by the gamma detector, including:
according to the N 1 The X L detection probabilities determine the total detection probability of the sample, which is detected by the gamma detector, of gamma rays emitted by the sample radiation source; and, according to the N 2 And determining the reference total detection probability of gamma rays emitted by the reference radioactive source detected by the gamma detector.
3. The method of claim 2, wherein the sample radiation source is divided into N 1 A plurality of sample point sources; and dividing the reference radiation source into N 2 A reference point source comprising:
uniformly dividing the sample radioactive source into N 1 -the sample point sources; and, uniformly dividing the reference radiation source into N 2 And each reference point source.
4. The method of claim 3, wherein the sample radiation source is uniformly divided into N 1 -the sample point sources; and, uniformly dividing the reference radiation source into N 2 Each of the reference point sources comprises:
randomly dividing the sample radioactive source into N by using Monte Carlo sampling method 1 -the sample point sources; and randomly dividing the reference radioactive source into N by using a Monte Carlo sampling method 2 And each reference point source.
5. The method of claim 2, wherein the method of calculating the total detection probability of the radiation source further comprises the steps of:
a, dividing the radioactive source into M point sources, wherein M is a positive integer and M is smaller than N 1 And N 2 The method comprises the steps of carrying out a first treatment on the surface of the The radioactive source comprises a reference radioactive source or a sample radioactive source;
b, determining L gamma rays emitted by each point source in the M point sources to obtain M multiplied by L gamma rays;
c, determining the detection probability of each gamma ray in the M X L gamma rays detected by the gamma detector to obtain M X L detection probabilities;
d, determining a first total detection probability that gamma rays emitted by the radioactive source are detected by the gamma detector according to the M multiplied by L detection probabilities;
e, dividing the radioactive source into 2M point sources, and obtaining 2M multiplied by L detection probabilities according to the steps B-C;
f, determining a second total detection probability of gamma rays emitted by the radioactive source detected by the gamma detector according to the 2M multiplied by L detection probabilities;
g, determining a relative error of the second total detection probability according to a difference value between the first total detection probability and the second total detection probability;
h, if the relative error is smaller than a preset threshold value, determining the second total detection probability as the total detection probability of the radioactive source;
and I, if the relative error is greater than or equal to a preset threshold value, increasing the value of M, and returning to execute the step A.
6. The method of any one of claims 2-5, wherein the N is determined 1 The detection probability that each gamma ray in the x L gamma rays is detected by the gamma detector comprises:
the N is determined using the following formula 1 Detection probability of each gamma ray in the x L gamma rays detected by the gamma detector:
wherein (1)>
For the N 1 The detection probability of the ith gamma ray in the X L gamma rays detected by the gamma detector is that i is more than 0 and less than or equal to N 1 X L integer>
For the attenuation coefficient of the gamma detector working medium, D is the path length of the ith gamma ray passing through the gamma detector working medium, < >>
Attenuation coefficient of j-th non-working medium through which the i-th gamma ray passes,/->
And j is a positive integer for the path length of the ith gamma ray passing through the jth non-working medium.
7. An efficiency calibration apparatus for a gamma detector, comprising means for performing the method of any one of claims 1-6.
8. The gamma detection system is characterized by comprising a gamma detector and an upper computer, wherein the gamma detector is connected with the upper computer; wherein the upper computer comprises a processor connected to a memory for executing a computer program in the memory such that the method according to any of claims 1-6 is performed.
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