Beta nuclide double-label identification method based on TDCR

Abstract

The invention discloses a beta nuclide double-label identification method based on TDCR, and the method employs the principle of the unique shape of a quenching curve of the TDCR to identify different beta nuclides and accurately calculate the activity. The TDCR is used as a quenching indication parameter, has a linear relation with the counting efficiency of the nuclide, and is commonly represented by a second-order polynomial fitting function in practical application, and the curve is also called a quenching correction curve. The TDCR value of the known nuclide can be used for reversely deducing the counting efficiency of the corresponding nuclide so as to solve the activity of the sample.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactivity measurement, and in particular to a β-nuclide double-labeling identification method based on TDCR. Background Art

[0002] Liquid scintillation spectrometers (also known as liquid scintillation counters) are widely used in customs, nuclear power plants, the nuclear industry, environmental monitoring, nuclear medicine, life science research, and radiation protection. They are primarily used to measure the activity of low-energy beta radionuclides such as H-3 and C-14. They primarily consist of a detector, a multichannel pulse amplitude analyzer, a high-voltage module, a transmission system, a shielding system, and a computer. Beta particles released by the radioactive sample collide with solvent molecules in the scintillation fluid, transferring energy to the solvent molecules and exciting them to produce fluorescent photons. These photons pass through a transparent sample vial and enter a photomultiplier tube (PMT). They are converted into photoelectrons on the photocathode surface. After multiplication, they form electrical pulse signals. After amplification by a preamplifier, a multichannel analyzer (MCA) divides the channels according to energy thresholds to generate a beta spectrum. The beta spectrum is a continuous spectrum, and it is generally believed that the maximum energy, Emax, of the electrons emitted by the nuclide is linearly related to the end position of the spectrum.

[0003] The triple-to-double coincidence ratio (TDCR) method is an absolute measurement method used in liquid scintillation spectrometers. Based on a free parameter model, it uses experimentally measured coincidence counts and a theoretical efficiency calculation model to directly determine the activity of the radioactive sample being measured. The TDCR method is based on coincidence counting technology. The TDCR value is a quenching indicator parameter that can be used to characterize changes in the quenching degree of the sample. It has the advantages of a unique quenching curve shape, good stability, and few influencing factors. The specific calculation is as follows (1):

[0004]

[0005] Among them, N t is the coincidence counting rate of the three sample tubes, N d The counting rates for the two tubes of sample match.

[0006] Dual-label measurement technology in liquid scintillation spectrometry involves the simultaneous detection of the activity of two different radionuclides (such as H-3 / C-14 and H-3 / P-32) through multi-channel pulse amplitude analysis and quenching correction algorithms. Currently, one method of dual-label measurement involves the external standard source method. This involves introducing an external standard source (such as Ba-133 or Cs-137) to measure the sample's quenching parameter (tSIE or external standard channel ratio ESCR), establishing quenching correction curves for each nuclide in different energy windows, and then performing a polynomial fit to determine the activity. This method is complex and time-consuming, and requires the use of a gamma-ray external standard source, which poses a risk to personnel. Another polynomial solution method for the cardan energy window requires the preparation of a known activity solution (also known as an efficiency calibration sample) with the same ratio as the sample to obtain and replace the sample's quenching degree for activity calculation. The entire process is cumbersome to operate and is subject to issues such as error accumulation during chemical operations and the reuse of quenching indicator parameters that only consider the influence of the ratio. This results in poor overall dual-label measurement accuracy.

[0007] Therefore, how to improve the measurement accuracy of dual-nuclide labeling is a technical problem that needs to be solved urgently. Summary of the Invention

[0008] To address the shortcomings of the existing technology, the present invention provides a dual-label β-nuclides identification method based on TDCR. This method utilizes the unique shape of the TDCR quenching curve to identify different β-nuclides and accurately calculate their activity. TDCR, as a quenching indicator parameter, exhibits a linear relationship with the counting efficiency of the nuclide. In practical applications, a second-order polynomial fit function is often used to represent this curve, also known as a quenching correction curve. The TDCR value of a known nuclide can be inferred from the corresponding nuclide counting efficiency, thereby determining the sample activity.

[0009] The embodiment of the present invention provides the following solutions:

[0010] An embodiment of the present invention provides a β-nuclides dual-labeling identification method based on TDCR, the method comprising:

[0011] S1. For a mixed sample with known quenching degree and activity, measure the background sample corresponding to the mixed sample;

[0012] S2. Measure the series of quenching sources corresponding to the two nuclides to obtain the counting efficiency of each quenching source in the series, and find the maximum channel address H of the energy spectrum through Gaussian filtering;

[0013] S3. drawing quenching correction curves of the two nuclides based on counting efficiency, and fitting quenching correction curve functions of the two nuclides;

[0014] S4. Draw the H&TDCR relationship diagram of the two nuclides and fit the maximum address function of the two nuclides;

[0015] S5. Test the sample containing two nuclides with unknown quenching degree and activity, and obtain the two-tube coincidence count rate Nd of the full composite spectrum of the two nuclides. T And the TDCR value of the composite spectrum TDCR T ;

[0016] S6. Perform energy spectrum analysis, perform Gaussian filtering on the energy spectrum, and find the maximum channel address H of the energy spectrum. T Substitute the value into the maximum channel address function expression of the high-energy nuclide in the two nuclides to obtain the TDCR value R of the high-energy nuclide H ;

[0017] S7, R H Substitute the quenching correction curve function of the high-energy nuclide in the two nuclides to obtain the counting efficiency Eff of the high-energy nuclide H ;

[0018] S8. Calculate the maximum channel address H of the low-energy nuclide based on the maximum emission energy relationship of the two nuclides. L ;

[0019] S9, the maximum address of low energy nuclides H L Substitute the maximum address function of the low-energy nuclide to obtain the TDCR value R of the low-energy nuclide L ;

[0020] S10, R L Substitute the quenching correction curve function of the low-energy nuclide in the two nuclides to obtain the counting efficiency Eff of the low-energy nuclide L ;

[0021] S11. Calculate the coincidence counting rate of the two tubes for the two nuclides using the following formula:

[0022]

[0023] Among them, Nd H and Nd L are the coincidence counting rates of the two tubes for the high-energy nuclide and the low-energy nuclide respectively, R T is the TDCR value of the composite spectrum of the two nuclides, Nd T The coincidence count rate of the two tubes of the full composite spectrum measured in step S4;

[0024] S12. Calculate the activity of the two nuclides using the following formula:

[0025]

[0026] Among them, A H and A L are the activities of the high-energy and low-energy nuclides in the two nuclides, respectively.

[0027] In an optional embodiment, the counting efficiency Eff of the i-th quenching source in the series of quenching sources in step S2 is j Calculated by the following formula:

[0028]

[0029] Among them, Nd j is the coincidence counting rate of the two tubes of the sample by the i-th quenching source, and A is the activity of the series quenching source.

[0030] In an optional embodiment, the quenching correction curve functions of the two nuclides in step S3 are respectively:

[0031] Eff H =a1R H 2 +b1R H +c1

[0032] Eff L =a2R L 2 +b2R L +c2

[0033] Among them, Eff H and Eff L are the counting efficiencies of high-energy and low-energy nuclides in the two nuclides, R H and R L are the TDCR values ​​of high-energy nuclides and low-energy nuclides, respectively. a1, a2, b1, b2, c1 and c2 are the parameters obtained by fitting calculation.

[0034] In an optional embodiment, the maximum address functions of the two nuclides in step S4 are respectively:

[0035] R H =a3H H 2 +b3H H +c3

[0036] R L =a4H L 2 +b4H L +c4

[0037] Among them, R H and R L are the TDCR values ​​of the high-energy nuclide and the low-energy nuclide in the two nuclides, respectively. H and H L are the maximum channel addresses of high-energy nuclides and low-energy nuclides, respectively. a3, a4, b3, b4, c3 and c4 are parameters obtained by fitting calculation.

[0038] In an optional embodiment, the maximum emission energy relationship between the two nuclides in step S7 is:

[0039]

[0040] Among them, H H and H L are the maximum addresses of the high-energy nuclide and the low-energy nuclide in the two nuclides respectively; E H and E L are the maximum energies of electrons emitted by high-energy nuclides and low-energy nuclides, respectively.

[0041] The beneficial effects of the present invention based on its technical solution are:

[0042] The present invention provides a TDCR-based dual-label identification method for β-nuclides. This method establishes a relationship between the maximum channel address of the energy spectrum and the maximum channel address of the energy spectrum, which changes with the degree of quenching of the sample. Due to energy linearity, when the degree of quenching is consistent, the maximum emission energy of electrons emitted by two different nuclides corresponds to the maximum channel address of the energy spectrum. Knowing the maximum channel address of one nuclide's energy spectrum makes it easier to determine the maximum channel address of the other nuclide's energy spectrum. In combination with the above principles, the TDCR value of one nuclide can be determined when the TDCR or maximum channel address of the energy spectrum of the other nuclide is known. The present invention has the advantage of not requiring the preparation of a known activity solution (efficiency calibration sample) with the same ratio as the sample, greatly simplifying the process, eliminating systematic errors in the preparation process, and significantly improving the accuracy of dual-label measurements. Furthermore, the series of quenching sources are all sealed sources, making their use and management safer and more convenient than operating high-activity standard solutions and gamma external standard sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 Schematic diagram of the quenching correction curve.

[0045] Figure 2 Schematic diagram of the relationship between the maximum address H and TDCR.

[0046] Figure 3 This is the H&TDCR relationship diagram of the two nuclides. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the embodiments of the present invention.

[0048] First, the principle of the present invention is explained.

[0049] The true two-tube coincidence count rate of either nuclide can be calculated using the TDCR values ​​of the two nuclides, the composite spectrum TDCR value, and the total two-tube coincidence count rate of the composite spectrum. According to the TDCR principle, in a composite spectrum of a mixture of two nuclides, the following equation generally exists:

[0050]

[0051] Among them TDCR H is the TDCR value of the higher energy nuclide of the two nuclides, referred to as R H ;Nt H is the actual three-tube coincidence counting rate corresponding to higher energy nuclides; Nd H is the actual coincidence counting rate of the two tubes corresponding to the higher energy nuclide;

[0052]

[0053] Among them TDCR L is the TDCR value of the higher energy nuclide of the two nuclides, referred to as R L ;Nt L The actual three-tube coincidence counting rate corresponding to the lower high-energy nuclide; Nd L is the actual coincidence counting rate of the two tubes corresponding to the lower energy nuclide;

[0054]

[0055] TDCRT is the TDCR value of the composite spectrum of two nuclides, referred to as R T ;Nt H is the three-tube coincidence count rate of the composite spectrum of the two nuclides; Nd H is the coincidence counting rate of the two tubes for the composite spectrum of the two nuclides;

[0056] Combining the above three equations (2), (3) and (4) we can get the following equation:

[0057]

[0058] According to the above relationship, Nd H and Nd L Finally, the corresponding counting efficiency is obtained through the quenching correction curve function relationship, and then the sample activity is calculated.

[0059] Based on the above principle, this embodiment provides a β-nuclides dual labeling identification method based on TDCR. Figure 1 , the method comprising:

[0060] First measure the background:

[0061] S1. For a mixed sample with known quenching degree and activity, measure the background sample with the corresponding proportion of the mixed sample.

[0062] Then the quenching series source is measured and four curves are obtained:

[0063] S2. Measure the series of quenching sources corresponding to the two nuclides to obtain the counting efficiency of each quenching source in the series of quenching sources, where the counting efficiency Eff of the i-th quenching source is j Calculated by the following formula:

[0064]

[0065] Among them, Nd j is the coincidence count rate of the two tubes of the sample by the i-th quenching source, A is the activity of the series quenching source, and the maximum channel address H of the energy spectrum is found by Gaussian filtering.

[0066] S3, such as Figure 2 As shown in the figure, the quenching correction curves of the two nuclides are drawn by counting efficiency, and the quenching correction curve functions of the two nuclides are fitted, which are:

[0067] Eff H =a1R H 2 +b1R H +c1

[0068] Eff L =a2R L 2 +b2R L +c2

[0069] Among them, Eff H and Eff L are the counting efficiencies of high-energy and low-energy nuclides in the two nuclides, R H and R L are the TDCR values ​​of high-energy nuclides and low-energy nuclides, respectively. a1, a2, b1, b2, c1 and c2 are the parameters obtained by fitting calculation.

[0070] S4, such as Figure 3 As shown, the H&TDCR relationship diagram of the two nuclides is drawn, and the maximum address functions of the two nuclides are fitted, which are:

[0071] RH =a3H H 2 +b3H H +c3

[0072] R L =a4H L 2 +b4H L +c4

[0073] Among them, R H and R L are the TDCR values ​​of the high-energy nuclide and the low-energy nuclide in the two nuclides, respectively. H and H L are the maximum channel addresses of high-energy nuclides and low-energy nuclides, respectively. a3, a4, b3, b4, c3 and c4 are parameters obtained by fitting calculation.

[0074] S5. Test the sample containing two nuclides with unknown quenching degree and activity, and obtain the two-tube coincidence count rate Nd of the full composite spectrum of the two nuclides. T And the TDCR value of the composite spectrum TDCR T .

[0075] The mixed sample is then measured and analyzed:

[0076] S6. Perform energy spectrum analysis, perform Gaussian filtering on the energy spectrum, and find the maximum channel address H of the energy spectrum. T Substitute the value into the maximum channel address function expression of the high-energy nuclide in the two nuclides to obtain the TDCR value R of the high-energy nuclide H ;

[0077] S7, R H Substitute the quenching correction curve function of the high-energy nuclide in the two nuclides to obtain the counting efficiency Eff of the high-energy nuclide H ;

[0078] S8. Calculate the maximum channel address H of the low-energy nuclide based on the maximum emission energy relationship of the two nuclides. L , the maximum emission energy relationship between the two nuclides is

[0079]

[0080] Among them, H H and H L are the maximum addresses of the high-energy nuclide and the low-energy nuclide in the two nuclides respectively; E H and E L are the maximum energies of electrons emitted by high-energy nuclides and low-energy nuclides, respectively.

[0081] S9, the maximum address of low energy nuclides H LSubstitute the maximum address function of the low-energy nuclide to obtain the TDCR value R of the low-energy nuclide L .

[0082] S10, R L Substitute the quenching correction curve function of the low-energy nuclide in the two nuclides to obtain the counting efficiency Eff of the low-energy nuclide L .

[0083] S11. Calculate the coincidence counting rate of the two tubes for the two nuclides using the following formula:

[0084]

[0085] Among them, Nd H and Nd L are the coincidence counting rates of the two tubes for the high-energy nuclide and the low-energy nuclide respectively, R T is the TDCR value of the composite spectrum of the two nuclides, Nd T It is the coincidence count rate of the two tubes of the full composite spectrum measured in step S4.

[0086] S12. Calculate the activity of the two nuclides using the following formula:

[0087]

[0088] Among them, A H and A L are the activities of the high-energy and low-energy nuclides in the two nuclides, respectively.

[0089] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0090] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (modules, systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0091] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0092] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0093] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0094] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A β-nuclides dual-labeling identification method based on TDCR, characterized in that: The method comprises: S1. For a mixed sample with known quenching degree and activity, measure the background sample corresponding to the mixed sample; S2. Measure the series of quenching sources corresponding to the two nuclides to obtain the counting efficiency of each quenching source in the series, and find the maximum channel address H of the energy spectrum through Gaussian filtering; S3. drawing quenching correction curves of the two nuclides based on counting efficiency, and fitting quenching correction curve functions of the two nuclides; S4. Draw the H&TDCR relationship diagram of the two nuclides and fit the maximum address function of the two nuclides; S5. Test the sample containing two nuclides with unknown quenching degree and activity, and obtain the two-tube coincidence count rate Nd of the full composite spectrum of the two nuclides. T And the TDCR value of the composite spectrum TDCR T ; S6. Perform energy spectrum analysis, perform Gaussian filtering on the energy spectrum, and find the maximum channel address H of the energy spectrum. T Substitute the value into the maximum channel address function expression of the high-energy nuclide in the two nuclides to obtain the TDCR value R of the high-energy nuclide H ; S7, R H Substitute the quenching correction curve function of the high-energy nuclide in the two nuclides to obtain the counting efficiency Eff of the high-energy nuclide H ; S8. Calculate the maximum channel address H of the low-energy nuclide based on the maximum emission energy relationship of the two nuclides. L ; S9, the maximum address of low energy nuclides H L Substitute the maximum address function of the low-energy nuclide to obtain the TDCR value R of the low-energy nuclide L ; S10, R L Substitute the quenching correction curve function of the low-energy nuclide in the two nuclides to obtain the counting efficiency Eff of the low-energy nuclide L ; S11. Calculate the coincidence counting rate of the two tubes for the two nuclides using the following formula: Among them, Nd H and Nd L are the coincidence counting rates of the two tubes for the high-energy nuclide and the low-energy nuclide respectively, R T is the TDCR value of the composite spectrum of the two nuclides, Nd T The coincidence count rate of the two tubes of the full composite spectrum measured in step S4; S12. Calculate the activity of the two nuclides using the following formula: Among them, A H and A L are the activities of the high-energy and low-energy nuclides in the two nuclides, respectively.

2. The TDCR-based β-nuclides dual-labeling identification method according to claim 1, characterized in that: The counting efficiency Eff of the i-th quenching source in the series of quenching sources described in step S2 is j Calculated by the following formula: Among them, Nd j is the coincidence counting rate of the two tubes of the sample by the i-th quenching source, and A is the activity of the series quenching source.

3. The TDCR-based β-nuclides dual-labeling identification method according to claim 1, characterized in that: The quenching calibration curve functions of the two nuclides described in step S3 are: Eff H =a1R H 2 +b1R H + c1 Eff L =a2R L 2 +b2R L +c2 Among them, Eff H and Eff L are the counting efficiencies of high-energy and low-energy nuclides in the two nuclides, R H and R L are the TDCR values ​​of high-energy nuclides and low-energy nuclides, respectively. a1, a2, b1, b2, c1 and c2 are the parameters obtained by fitting calculation.

4. The TDCR-based β-nuclides dual-labeling identification method according to claim 1, characterized in that: The maximum address functions of the two nuclides described in step S4 are: <h2 style=";text-align:left;direction:ltr">R<h2 style=";text-align:left;direction:ltr"> H <h2 style=";text-align:left;direction:ltr"> =a3H<h2 style=";text-align:left;direction:ltr"> H <h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +b3H<h2 style=";text-align:left;direction:ltr"> H <h2 style=";text-align:left;direction:ltr"> +c3 R L =a4H L 2 +b4H L +c4 Among them, R H and R L are the TDCR values ​​of the high-energy nuclide and the low-energy nuclide in the two nuclides, respectively. H and H L are the maximum channel addresses of high-energy nuclides and low-energy nuclides, respectively. a3, a4, b3, b4, c3 and c4 are parameters obtained by fitting calculation.

5. The TDCR-based β-nuclides dual-labeling identification method according to claim 1, characterized in that: The maximum emission energy relationship between the two nuclides in step S7 is: Among them, H H and H L are the maximum addresses of the high-energy nuclide and the low-energy nuclide in the two nuclides respectively; E H and E L are the maximum energies of electrons emitted by high-energy nuclides and low-energy nuclides, respectively.

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