CN115856994A - Efficiency calibration method, device and system for gamma detector - Google Patents
Efficiency calibration method, device and system for gamma detector Download PDFInfo
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Abstract
The embodiment of the invention provides an efficiency calibration method, a device and a system of a gamma detector, relating to the field of radiation detection, wherein 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, 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 respectively calculated; and determining the full-energy peak detection efficiency of the gamma detector for detecting the sample radioactive source according to the total sample detection probability, 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 representation of the detector, and is suitable for radioactive sources with any shapes.
Description
Technical Field
The invention relates to the field of radiation detection, in particular to an efficiency calibration method, device and system of a gamma detector.
Background
Gamma detectors (also known as gamma spectrometers) are one of the most widely used instruments in radiation detection. In the measurement of the activity of radionuclides, efficiency calibration (efficiency calibration) of the gamma detection system used is required. The efficiency calibration method of the gamma detector mainly comprises the following steps:
1, generally, the efficiency calibration of a gamma detector is determined using standard source spectral measurements of known activity. However, when the geometry and material of the sample source (i.e. the radioactive source to be measured) are very different from those of the standard source, it is not a simple matter for most relevant workers to re-search for the appropriate standard source for calibration. If the measurement is made directly without recalibration, significant errors can be introduced.
2, efficiency calibration is performed using the monte carlo method. This requires mastering the monte carlo procedure and a detailed description of the detector and sample source. However, this method is less accurate due to the difficulty in accurately describing the crystal dead layer, and the like.
And 3, carrying out efficiency calibration in a passive efficiency calibration mode. For example, passive efficiency calibration software such as LabSOCS and GammaCalib is used to calculate the detection efficiency of any sample source. However, the gamma detectors used for the measurements must be characterized rigorously, and uncharacterized gamma detectors cannot use these passive efficiency calibration software.
And 4, detecting 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 representation of the detectors and the like, the initial version SOLANG can only calculate a point source and a cylinder source with the radius of a radioactive source smaller than that of the detector, and the advanced version ANGLE can calculate the cylinder source with any radius and a Ma Linbei source. ANGEL assumes that the radioactive source is a point source, a cylinder source or a Ma Linbei source and the like which are arranged right above the detector and are coaxial with the detector, and the calculation method is based on the concept of an effective solid angle. The calculation method needs to describe a 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 volume of the surface of the detector and the volume of the radioactive source to obtain a geometric solid angle of the radioactive source to the detector. After the attenuation factor and the efficiency factor are added in the multiple integral expression, the multiple integral expression of the effective solid angle can be obtained. Then, the effective solid angle of the radiation source to the detector is calculated by utilizing Gaussian Legendre integral, and finally, the ratio of the effective solid angles of the two radiation sources to the detector is used for carrying out the transfer of the full energy peak detection efficiency. This method describes well the geometry of the point source, cylinder source and Ma Linbei source, as well as the photon attenuation and detector response, but its latest version of ANGLE4 is so far only applicable to point sources, cylinder sources and Ma Linbei sources, because of the limitations of the mathematical methods used. In other words, this method is not suitable for the efficiency calibration of any shape of radioactive source.
Therefore, the existing efficiency calibration method has one or more of the following problems: the calibration process is complex, the accuracy is low, the detector cannot be calibrated when not being strictly characterized, and the method is not suitable for the efficiency calibration of radioactive sources with any shapes.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method, an apparatus and a system for calibrating efficiency of a gamma detector, which can improve accuracy of efficiency calibration, and have a simple calibration process, and the gamma detector does not need to be subjected to strict characterization, and is suitable for any shape of radioactive source.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
in a first aspect, the present invention provides a method for calibrating the efficiency of a gamma detector. The method of the first aspect comprises: acquiring the full-energy peak detection efficiency of a gamma ray of target energy emitted by a gamma detector detection reference radioactive source; respectively acquiring the reference total detection probability of a reference radioactive source and the sample total detection probability of a sample radioactive source according to the calculation method of the total detection probability of the radioactive source; determining the full-energy peak detection efficiency of a gamma ray of target energy emitted by a gamma detector to detect a sample radioactive source according to the sample total detection probability, the reference total detection probability and the full-energy peak detection efficiency of a reference radioactive source; the method for calculating the total detection probability of the radioactive source comprises the following steps: dividing a radioactive 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 a 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 the gamma rays emitted by the radioactive source detected by the gamma detector according to the plurality of detection probabilities.
In a second aspect, the present invention provides an efficiency calibration apparatus for a gamma detector, comprising: the device comprises a measuring 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 gamma rays of the target energy 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 full-energy peak detection efficiency of the gamma ray of the target energy emitted by the gamma detector according to the sample total detection probability, the reference total detection probability and the full-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: 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 a plurality of point sources to obtain a gamma ray set; the processing module is further 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 the gamma rays emitted by the radioactive source detected by the gamma detector according to the plurality of detection probabilities.
In a third aspect, the present invention provides a gamma detection system, including a gamma detector and an upper computer, where the gamma detector is connected to the upper computer, and the upper computer includes a processor connected to a memory, and the processor is configured to execute a computer program in the memory, so that the method of the first aspect is executed.
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 conventional efficiency calibration method, in the efficiency calibration method for 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 carry out efficiency calibration, avoids multiple integration of a stereo angle, simplifies the efficiency calibration process and reduces the calculation amount. In addition, in the scheme, the full-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 sample total detection probability, the reference total detection probability and the full-energy peak detection efficiency of the reference radioactive source. In other words, the full-energy peak detection efficiency of the sample radioactive source is calculated in an efficiency transfer mode, so that efficiency calibration is realized, strict factory representation is not needed in the process, and the method is suitable for efficiency calibration of batch gamma detectors. In addition, the shape of the radioactive source is not limited, so that the total detection probability of the gamma detector for gamma photons with specific energy of the radioactive source in any shape can be quickly and accurately calculated, the efficiency transfer calculation of the radioactive source in any shape is further realized, and the method has the characteristics of no limitation of the geometric shape and position of the radioactive source, high calculation speed, high accuracy and the like.
In order to make the aforementioned objects, features and advantages of the present invention 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 needed to be used 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 therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic diagram of a gamma detection system according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a method for calibrating the efficiency of a gamma detector according to an embodiment of the present invention;
FIG. 3 is a schematic view of a detailed process of S120 in FIG. 2;
FIG. 4 is a simplified two-dimensional geometric model of a gamma detector and a radiation source according to an embodiment of the present invention;
FIG. 5 is a schematic view of the radiation source of FIG. 4 uniformly divided into a plurality of cells;
FIG. 6 is a schematic diagram of L segments extending uniformly around a certain cell in FIG. 5;
FIG. 7 is a schematic diagram showing the distance between two adjacent intersections on a gamma ray of FIG. 6;
fig. 8 is a functional block diagram of an efficiency calibration apparatus for a gamma detector according to an embodiment of the present invention.
Description of reference numerals: 100-gamma detection system; 110-gamma detector; 120-an upper computer; 130-a radioactive source; 200-an efficiency calibration device of a gamma detector; 210-an input module; 220-a processing module; 230-an output module; 240-measurement module.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of 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 present invention, 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 obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined or explained in subsequent figures.
Furthermore, the appearances of the terms "first," "second," and the like, if any, are used solely to distinguish one from another and are not to be construed as indicating or implying 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 is explained in the following with reference to the accompanying drawings.
First, a gamma detection system according to an embodiment of the present invention is described. Referring to fig. 1, fig. 1 is a schematic view 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 an upper computer 120. The gamma detector 110 is connected to the upper computer 120. The upper computer 120 is installed with efficiency calibration software, and can be used to execute the efficiency calibration method of the gamma detector provided by the embodiment of the invention. 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 multichannel analyzer.
The gamma detector 110 may include a semiconductor detector or a scintillator detector, but is not limited thereto. The upper computer 120 may include a processor connected to a memory, and the processor is configured to execute a computer program in the memory, so that the efficiency calibration method for the gamma detector (see below in detail) provided by the embodiment of the present invention is executed.
In an alternative embodiment, the host computer 120 includes, but is not limited to: personal computers, servers, laptops, desktops, tablets, etc.
On the basis of the gamma detection system 100 shown in fig. 1, an embodiment of the present invention further provides an efficiency calibration method for a gamma detector, which can be applied to the gamma detection system 100 and can be executed by the upper computer 120 of the gamma detection system 100. Referring to fig. 2, fig. 2 is a schematic flowchart illustrating an efficiency calibration method for a gamma detector according to an embodiment of the present invention.
The efficiency calibration method of the gamma detector may include the following steps S110 to S130, which are described below.
And S110, acquiring the full energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the reference radioactive source.
The full-energy 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 full-energy peak detection efficiency of the gamma rays with specific energy of the reference radioactive source is obtained through experimental measurement. In other words, the full-energy peak detection efficiency of the reference radiation source may be a value obtained in advance through experimental measurement of the reference radiation source.
In alternative embodiments, the gamma detector comprises a semiconductor detector or a scintillator detector.
And 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 optional embodiment, the method for calculating the total detection probability of the radioactive source comprises the following steps 1.1-1.4:
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.
Step 1.2, determining a plurality of gamma rays emitted by each point source in a plurality of point sources to obtain a gamma ray set.
Step 1.3, 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 step 1.4, determining the total detection probability of the gamma rays emitted by the radioactive source detected by the gamma detector according to the plurality of 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 detailed flowchart of S120 in fig. 2. S120 includes the following steps S121A-S124B:
S121A, dividing the sample radioactive source into N 1 Individual sample point source, N 1 Is a positive integer.
It is to be understood that in embodiments of the present invention, the sample radiation source is divided into N 1 The manner of individual sample point sources includes, but is not limited to: uniformly dividing a sample radiation source into N 1 Individual sample point sources, or randomly dividing the sample radiation source into N 1 A sample point source, etc.
In an alternative embodiment, S121A, the sample radiation source is divided into N 1 A sample point source comprising: uniformly dividing sample radioactive sources into N 1 A sample point source. Specifically, the Monte Carlo sampling method may be used to randomly divide the sample radiation sources into N 1 A sample point source.
S122A, determining N 1 Obtaining N by L gamma rays emitted by each sample point source in each sample point source 1 * L gamma rays, wherein L is a positive integer.
Wherein the sample point source may emit gamma photons spatially centered on itself, each gamma photon pair being understood to be a gamma ray. Thus, a sample point source emits multiple gamma rays all around. In alternative embodiments, the gamma ray may be directed in a point-wise manner (i.e., a point-wise manner)
) Where the endpoint coordinates (i.e., the location coordinates of the sample point source) are (x) 0 ，y 0 ，z 0 ) Direction 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 L gamma rays detected by the gamma detector is obtained to obtain N 1 * L detection probabilities.
Wherein, N is 1 * The ith gamma ray (i is more than 0 and less than or equal to N) in the L gamma rays 1 * Integer of L), the probability of detection of the ith gamma ray by a gamma detector and whether it passes through gamma detectionThe working medium in the detector, and the medium that passes through 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, the attenuation coefficient of the jth non-working medium passing through the ith gamma ray, and the path length of the ith gamma ray passing 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 L gamma rays detected by the gamma detector comprises the following steps: determining N using the following formula 1 * The detection probability of each gamma ray in the L gamma rays detected by the gamma detector is as follows:
wherein,
is N 1 * The detection probability of the ith gamma ray detected by the gamma detector in the L gamma rays is that i is more than 0 and less than or equal to N 1 * An integer of L->
Is the attenuation coefficient of the working medium of the gamma detector, D is the path length of the ith gamma ray passing through the working medium in the gamma detector, and is greater than or equal to>
For the attenuation coefficient of the jth non-working medium through which the ith gamma ray passes, < '> or <' >>
The path length of the ith gamma ray passing through the jth non-working medium is shown, and j is a positive integer.
It should be noted that, in the following description,
the path length of the ith gamma ray passing through the jth non-working medium specifically comprises the following steps:
is the path length of one or more non-working media through which the ith gamma ray passes before passing through the working media in the gamma detector.
It can be understood that in the above S121A to S123A, the efficiency calibration is performed from a single gamma ray (which may also be considered as a single gamma photon), so that multiple integration of the solid angle 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 gamma rays emitted by the sample radioactive source detected by the gamma detector according to the L detection probabilities.
Wherein, after S124A, the detection probability of each gamma ray detected by the gamma detector is calculated. The total probability of detection of the sample (denoted as P) can then be determined according to the following equation:
. In other words, the total detection probability of the sample is the sum of the detection probabilities of all gamma rays detected by the gamma detectors and then the average value is obtained.
With continued reference to FIG. 3, S121B, the reference radiation sources are divided into N 2 A reference point source, N 2 Is a positive integer.
S122B, determining N 2 Obtaining N gamma rays emitted by each reference point source in the reference point sources 2 * L gamma rays, L is a positive integer.
S123B, determining N 2 * The detection probability of each gamma ray in the L gamma rays detected by the gamma detector is obtained to obtain N 2 * L detection probabilities.
S124B, according to N 2 * Determining the detection probability of L gamma rays emitted by the reference radioactive source to be detected by the gamma detectorThe measured reference total detection probability.
The implementation principle of S121B to S124B is similar to that of S121A to S124A, and details about the specific implementation process and effect of S121B to S124B and with reference to S121A to S124A are not repeated herein.
In an alternative embodiment, the reference radiation source is an arbitrary shaped radiation source. Specifically, the reference radiation source is a point source. Therefore, the calculation amount of S121B-S124B can be reduced, and the efficiency calibration efficiency is improved.
S130, determining the full-energy peak detection efficiency of the gamma ray of the target energy emitted by the gamma detector according to the sample total detection probability, the reference total detection probability and the full-energy peak detection efficiency of the reference radioactive source.
After S130, the method further comprises: and (4) carrying out efficiency calibration on the gamma detector by utilizing the full-energy peak detection efficiency of the sample radioactive source.
It can be understood that S130 is equivalent to calculating the full energy peak detection efficiency of the sample radiation source by using an efficiency transfer method, thereby simplifying the efficiency calibration process and reducing the calculation amount.
Optionally, in S130, determining the full-energy peak detection efficiency of the gamma detector for detecting the gamma rays with the target energy emitted by the sample radiation source according to the sample total detection probability, the reference total detection probability, and the full-energy peak detection efficiency of the reference radiation source, including: determining the full-energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source by using the following formula:
wherein,
efficiency of full energy peak detection for the sample radiation source>
In order to refer to the full energy peak detection efficiency of the radioactive source,
for the total detection probability of the sample, is>
Is a reference total detection probability.
In S110 to S130, the energy of the gamma ray emitted by the reference radiation source is the same as the energy of the gamma ray emitted by 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, wherein M is a positive integer and is less than N 1 And N 2 . The radiation source may be a reference radiation source or a sample radiation source.
Optionally, 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 x L gamma rays, wherein L is a positive integer.
And 2.3, 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.
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 x L detection probabilities.
The implementation principle of steps 2.1 to 2.4 is similar to that of steps S121A to S124A, and details about the specific implementation process and effect of steps 2.1 to 2.4 are not repeated herein with reference to 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 detection probabilities, and determining a second total detection probability that the gamma rays emitted by the radioactive source are detected by the gamma detector according to the 2M detection probabilities;
it can be understood that in step 2.1 to step 2.5, since 2M is twice M, it is equivalent to further finely divide the radiation source, and calculate the total detection probability of the radiation source (i.e. calculate 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.
And 2.8, if the relative error is greater than or equal to the preset threshold value, increasing the value of M, and returning to execute the step 2.1.
In the above step 2.6 to step 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 probability of probing of the sample calculated for the second time may be: P-P/| P. In this example, assuming that the preset threshold is 0.01, if | P-P |/P is less than 0.01, step 2.7 is performed to determine a second total detection probability as the total detection probability, i.e., the output P = P ″; if | P-P |/P is greater than or equal to 0.01, step 2.8 is performed, the value of M is incremented, and execution returns to step 2.1. In this way, the relative error of the total detection probability of the radiation source can be made smaller, resulting in better accuracy. Wherein, optionally, increasing the value of M may include: each time step 2.8 is performed, M is magnified by a factor of 2.
In order to more clearly illustrate the above method embodiments, the following further describes the above method embodiments with reference to specific implementation principles. In one example, the above method embodiment may include the following steps:
step 3.1, please refer to fig. 4, and 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. Firstly, geometric models of a gamma detector (including a detector crystal, a dead layer, a cold finger and a detector shell) and a radioactive source (which can be a reference radioactive source or a sample radioactive source) and the like can be respectively created in a space rectangular coordinate system. Optionally, other absorbers, containers, etc. may be added (i.e., disposed) between the radiation source and the gamma detector.
Step 3.2, as shown in fig. 5, the radiation source may 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 be uniformly extended around each point source as a center, where K should be greater than the distance of the point source from the far end of the gamma detector.
Wherein, the ith line segment in the L line segments can be in a straight line point direction type
To describe. Wherein, the coordinate of the endpoint of the ith line segment (i.e. the point source coordinate) is (x) 0 ，y 0 ，z 0 ) Direction v = (a, b, c). In addition, the geometric surfaces of the gamma detector and the radiation source can be represented by corresponding curved surface functions. Therefore, whether the ith line segment and the geometric surface have an intersection can be judged by judging whether the curved surface function and the straight line function where the ith line segment is located have an intersection.
Step 3.3, the ith line segment is taken as an example. If the ith line segment does not have any intersection point with the geometric interface of the working medium 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 geometric interface of the working medium of the gamma detector, the intersection point of the ith line segment with any other geometric interface is determined, and the distance between any two adjacent intersection points is calculated, wherein the formula is as follows:
. If the distance between two adjacent intersection points passes through the working medium of the gamma detector, the distance is recorded as D; if the distance between two adjacent points of intersection does not pass through the working medium, it is recorded as ^ 4>
。
Step 3.4, for a randomly emitted gamma photon in the radioactive sourceSaid, it is detected by the detector with a probability of
. Wherein it is present>
For the detection probability of the ith gamma ray detected by the gamma detector in the L X N gamma rays, i is an integer which is more than 0 and less than or equal to L X N, and/or the gamma ray detection probability of the ith gamma ray is greater than 0 and less than or equal to L X N>
Is the attenuation coefficient of the working medium of the gamma detector, D is the path length of the ith gamma ray passing through the working medium in the gamma detector, and is combined with the gamma ray attenuation coefficient>
For the attenuation coefficient of the jth non-working medium through which the ith gamma ray passes, < '> or <' >>
The path length of the ith gamma ray passing through the jth non-working medium is j, and j is an integer larger than 0.
And 3.5, calculating the probability of each gamma photon detected by the gamma detector through the steps 3.1 to 3.4 to obtain L × N detection probabilities. Then, summing these probabilities and taking an average to obtain the total detection probability that the gamma photons with specific energy emitted by the radioactive source are detected by the gamma detector:
. It will be appreciated that the 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.
And 3.6, firstly, uniformly dividing the radioactive source into 2N grid cells to obtain 2LN gamma photons, and repeating the calculation processes from the step 3.3 to the step 3.5 to obtain a new total detection probability P. Then, it is judged whether | P-P |/P is less than 0.01. Specifically, if | P-P |/P is less than 0.01, then the output P = P, at which time
(ii) a If | P-P |/P | > 0.01, the radiation source is further subdivided and step 3.6 is again carried out until | P-P |/P | < 0.01, after a number of repetitions (for example x times), then>
. In this way, better accuracy can be obtained.
Step 3.7, respectively calculating the total detection probability P of the gamma detector to the reference source and the sample source according to the steps Reference to P, and the detection efficiency epsilon of the gamma detector to the gamma photons with specific energy emitted by the reference radioactive source is measured through experiments Reference to Then, according to the efficiency transfer formula
The detection efficiency of the gamma detector for the gamma photons with specific energy emitted by the sample radioactive source can be calculated.
It should be understood that, in the above method embodiment, the total detection probability of the radiation source is determined by dividing the radiation source into a plurality of point sources, then determining the detection probability of each gamma ray emitted by each point source, and determining the total detection probability of the radiation source according to the detection probability of each gamma ray. In other words, the method starts from a single gamma ray to carry out efficiency calibration, avoids multiple integration of a stereo angle, simplifies the efficiency calibration process and reduces the calculation amount. In addition, in the scheme, the full-energy peak detection efficiency of the sample radioactive source for detecting the gamma rays emitted by the sample radioactive source by the gamma detector is determined according to the total sample detection probability, the reference total detection probability and the full-energy peak detection efficiency of the reference radioactive source. In other words, the full-energy peak detection efficiency of the sample radioactive source is calculated in an efficiency transfer mode, so that efficiency calibration is realized, strict factory representation is not needed in the process, and the method is suitable for efficiency calibration of batch gamma detectors. In addition, the shape of the radioactive source is not limited, so that the total detection probability of the gamma detector for gamma photons with specific energy of the radioactive source in any shape can be quickly and accurately calculated, the efficiency transfer calculation of the radioactive source in any shape is further realized, and the method has the characteristics of no limitation of the geometric shape and position of the radioactive source, high calculation speed, high accuracy and the like.
Alternatively, the method embodiment provided by the invention can also be applied to self-attenuation correction corresponding to any radiation source geometry.
In order to implement the above embodiments and corresponding steps in various possible manners, an implementation manner of an efficiency calibration apparatus for a gamma detector is provided below, please refer to fig. 8, and fig. 8 shows a functional block diagram of an efficiency calibration apparatus 200 for a gamma detector according to an embodiment of the present invention. The efficiency calibration apparatus 200 of the gamma detector can be used to implement the method shown in fig. 2, and can be used to perform the steps that can be performed by the upper computer 120 in the above method embodiment. It should be noted that the basic principle and the resulting technical effect of the efficiency calibration apparatus 200 for a gamma detector provided in this embodiment are the same as those of the above embodiments, and for the sake of brief description, reference may be made to the corresponding contents in the above embodiments for parts that are not mentioned in this 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 modules may be stored in a memory in the form of software or Firmware (Firmware) or be fixed in an Operating System (OS) of the upper computer 120 shown in fig. 1 provided by the present invention, and may be 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 modules may be stored in the memory.
It is understood that the measurement module 240, the input module 210, the processing module 220, and the output module 230 may be used to support the upper computer 120 shown in fig. 1 to perform the relevant steps in the above method embodiments, and/or other processes for the technology described herein, such as the method embodiment shown in fig. 2 and the above-mentioned method embodiments, without limitation. 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 measuring 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 embodiment, the embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, performs the steps of the efficiency calibration method for a gamma detector.
Specifically, the storage medium may be a general-purpose storage medium, such as a removable disk, a hard disk, or the like, and when executed, the computer program on the storage medium can perform the method in the foregoing embodiments, so as to solve "one or more of the following problems of the existing efficiency calibration method exist: the calibration process is complex, the accuracy is low, calibration cannot be carried out when rigorous representation is not carried out, and the method is not suitable for efficiency calibration of radioactive sources in any shapes.
The above description is only an example of the present invention, and is not intended to limit the scope of the present invention, and it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for calibrating the efficiency of a gamma detector, the method comprising:
acquiring the full-energy peak detection efficiency of a gamma detector for detecting target energy gamma rays emitted by a 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 full-energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source according to the sample total detection probability, the reference total detection probability and the full-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 a radioactive source into a plurality of point sources; the radiation source comprises the reference radiation source or the sample radiation source;
determining a plurality of gamma rays emitted by each of the 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 the gamma rays emitted by the radioactive source detected by the gamma detector according to the plurality of detection probabilities.
2. The method of claim 1, wherein dividing the radiation source into a plurality of point sources comprises:
partitioning the sample radiation source into N 1 Individual sample point source, N 1 Is a positive integer; and, dividing said reference radiation source into N 2 A reference point source, N 2 Is a positive integer;
determining a plurality of gamma rays emitted by each of the plurality of point sources, resulting in a set of gamma rays, comprising:
determining the N 1 Obtaining N gamma rays emitted by each sample point source in each sample point source 1 * L gamma rays, wherein L is a positive integer; and, determining said N 2 Obtaining N gamma rays emitted by each reference point source in each reference point source 2 * L gamma rays, wherein L is a positive integer;
determining a detection probability of each gamma ray in the gamma ray set detected by the gamma detector to obtain a plurality of detection probabilities, including:
determining the N 1 * The detection probability of each gamma ray in the L gamma rays detected by the gamma detector is obtained to obtain N 1 * L detection probabilities; and, determining said N 2 * L-shaped gammaDetecting probability of each gamma ray in the gamma rays detected by the gamma detector to obtain N 2 * L detection probabilities;
determining a total detection probability that the gamma rays emitted by the radiation source are detected by the gamma detector according to the plurality of detection probabilities, comprising:
according to said N 1 * L detection probabilities, determining the total detection probability of the gamma rays emitted by the sample radioactive source detected by the gamma detector; and according to said N 2 * L detection probabilities, determining the reference total detection probability that the gamma ray emitted by the reference radioactive source is detected by the gamma detector.
3. The method of claim 2, wherein the radiation source is a point source.
4. The method of claim 2, wherein the sample radiation source is divided into N 1 A sample point source; and, dividing said reference radiation source into N 2 A reference point source comprising:
uniformly dividing the sample radiation source into N 1 A sample point source; and, uniformly dividing the reference radiation source into N 2 The reference point source.
5. The method of claim 4, wherein the sample radiation source is evenly divided into N 1 A sample point source; and, uniformly dividing the reference radiation source into N 2 The reference point source comprising:
randomly partitioning the sample radiation sources into N using a Monte Carlo sampling method 1 A sample point source; and, randomly partitioning the reference radiation source into N using a Monte Carlo sampling method 2 The reference point source.
6. The method of claim 2, wherein the method of calculating the total probability of detection 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 is less than N 1 And N 2 (ii) a The radiation source comprises a reference radiation source or a sample radiation source;
b, determining L gamma rays emitted by each of the M point sources to obtain M x 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 the gamma rays emitted by the radioactive source are detected by the gamma detector according to the M x L detection probabilities;
e, dividing the radioactive source into 2M point sources;
repeating the step A to the step E to obtain 2M L detection probabilities;
f, determining a second total detection probability that the gamma rays emitted by the radioactive source are detected by the gamma detector according to the 2M x L detection probabilities;
g, 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;
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;
i, if the relative error is larger than or equal to a preset threshold value, increasing the value of M, and returning to execute the step A.
7. The method of any of claims 2-6, wherein the N is determined 1 * The detection probability of each gamma ray in the L gamma rays detected by the gamma detector comprises the following steps:
determining said N using the formula 1 * The detection probability of each gamma ray in the L gamma rays detected by the gamma detector is as follows:
wherein,
is said N 1 * The detection probability of the ith gamma ray in the L gamma rays detected by the gamma detector is that i is more than 0 and less than or equal to N 1 * An integer of L->
Is the attenuation coefficient of the working medium of the gamma detector, D is the path length of the ith gamma ray passing through the working medium of the gamma detector, and is greater than or equal to>
An attenuation coefficient for a jth non-working medium through which said ith gamma ray passes, <' > based on a predetermined attenuation coefficient>
The path length of the ith gamma ray passing through the jth non-working medium is shown, and j is a positive integer.
8. The method of any one of claims 1-6, wherein determining the full-energy peak detection efficiency of the gamma detector for detecting gamma rays of target energy emitted by the sample radiation source based on the total probability of detection of the sample, the total probability of detection of the reference, and the full-energy peak detection efficiency of the reference radiation source comprises:
determining the full energy peak detection efficiency of the gamma detector for detecting the target energy gamma rays emitted by the sample radioactive source by using the following formula:
wherein,
for the full energy peak detection efficiency of the sample radiation source, based on the measured value>
Detecting an efficiency for the full energy peak of the reference radiation source->
For the total detection probability of the sample, < > is>
Is the reference total detection probability.
9. The efficiency calibration device of the gamma detector is characterized by comprising a measuring module, an input module and a processing module; wherein,
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 gamma rays of the target energy 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 further configured to determine, according to the sample total detection probability, the reference total detection probability, and the full-energy peak detection efficiency of the reference radioactive source, the full-energy peak detection efficiency of the gamma detector for detecting gamma rays with target energy emitted by the sample 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 radiation source comprises the reference radiation source or the sample radiation source;
the processing module is further configured to determine a plurality of gamma rays emitted by each of the plurality of point sources to obtain a gamma ray set;
the processing module is further configured to determine a detection probability that each gamma ray in the gamma ray set is detected by the gamma detector, so as to obtain a plurality of detection probabilities;
the processing module is further configured to determine, according to the plurality of detection probabilities, a total detection probability that the gamma rays emitted by the radiation source are detected by the gamma detector.
10. A 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 with a memory for executing a computer program in the memory such that the method according to any of claims 1-8 is performed.
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