Lu-177 activity direct measurement method, device and processor

Abstract

The invention relates to a Lu-177 activity direct measurement method, a Lu-177 activity direct measurement device and a processor. The method comprises the following steps: constructing a first calculation model for calculating the detection efficiency of a Lu-177 sample; the Lu-177 sample and the blank sample corresponding to the Lu-177 sample are measured, and the counting rate of the Lu-177 sample under different coincidence conditions is obtained; calculating detection efficiency based on the counting rate and a first calculation model; and calculating the activity of the Lu-177 sample based on the detection efficiency, the counting rate and an activity calculation model. Compared with the prior art that the low uncertainty level can be achieved only by carrying out dilution measurement in a laboratory or the high uncertainty level of field direct measurement is achieved, the method has the advantage that the accurate activity of the Lu-177 sample can be obtained by carrying out direct measurement and calculation in the laboratory or the field on the premise that dilution is not carried out. The method meets the requirements of simple and convenient sample preparation, recoverable nuclide and low uncertainty.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive material activity measurement, and in particular to a Lu-177 activity direct measurement method, device and processor. Background Art

[0002] Lu-177 is a short-lived decay nuclide with a half-life of 6.647 days. It decays to the excited state or ground state of Hf-177 through a β-transition. When Lu-177 decays to the excited state of Hf-177, Hf-177 undergoes a γ transition to de-excite to a lower energy level or ground state of Hf-177 by emitting γ rays or internal conversion electrons. The process of Lu-177 decaying to the ground state of Hf-177 includes 7 decay paths.

[0003] With the development of radiopharmaceuticals in clinical diagnosis and treatment, synthetic drugs of Lu-177 have been widely used in the treatment of diseases such as advanced prostate cancer and neuroendocrine tumors in recent years. In clinical medication, in order to ensure that the attending physician or nursing staff can accurately assess the patient's dosage, it is necessary to accurately measure the activity of Lu-177 drugs. The usual process is as follows: a Lu-177 solution is divided into two batches for sample preparation. After dilution, the first batch of solution is prepared and measured according to the requirements of the liquid scintillation method or the method to determine the specific activity and uncertainty of the batch of solution before dilution. At the same time, the other batch of solution is prepared into a sample form suitable for the activity meter (such as an ampoule or vial) under undiluted conditions and measured. According to the specific activity measured by the liquid scintillation method or the method, the total activity of the sample used for the activity meter is determined, and the activity meter is calibrated using the known sample activity value and its uncertainty, so as to obtain the calibration factor of Lu-177 in the sample form.

[0004] The calibrated activity meter can be used to calibrate or calibrate other working-level activity meters, so that the activity meter in the workplace can also measure the activity of Lu-177 solution. In the above process, the value of Lu-177 is transferred through three steps: first, it is determined by the absolute measurement method of the reference, then it is calibrated by the standard-level activity meter, and finally it is transferred to the scale of the working-level activity meter. Because the uncertainty accumulates in the step-by-step transfer, the uncertainty of the activity measurement of Lu-177 solution using the activity meter in the general medical field is usually not less than 3%.

[0005] At present, for the activity measurement of radiopharmaceutical Lu-177, the mainstream methods in the laboratory include the liquid scintillation triple-tube double-tube coincidence ratio (TDCR) method, the liquid scintillation efficiency tracer method and the 4πβ-γ coincidence method, while in medical sites or isotope production sites, the commonly used method is to use a medical activity meter to measure the high-activity Lu-177 solution. However, both in the laboratory and in the medical field, the above methods have significant technical defects, which limit the efficiency and accuracy of their application.

[0006] In the laboratory, when the activity of Lu-177 is measured based on liquid scintillation or composite methods, the total activity of the sample to be tested usually needs to be strictly controlled within 10,000 Bq. This is because high-activity samples will lead to excessively high counting rates, causing channel blockage and pulse accumulation, which will seriously interfere with the accuracy of the measurement results. Therefore, the laboratory must dilute the Lu-177 solution sent for measurement before preparing samples for measurement, which not only increases the operating steps, but also introduces additional sources of error. In addition, since such samples are usually prepared as liquid scintillation samples or thin film source samples, the Lu-177 cannot be recovered after the measurement is completed, and the samples can only be treated as radioactive waste, resulting in waste of resources and environmental pollution.

[0007] At medical sites or isotope production sites, although medical activity meters can directly measure high-activity Lu-177 solutions, and the measured solutions can continue to be used, this method has two significant defects. First, the activity meter must be calibrated with a Lu-177 solution of known activity before use. This process is not only time-consuming, but also depends on the accuracy of standard samples, which increases the complexity and cost of the measurement. Second, the uncertainty of the measurement results of medical activity meters is usually not less than 3% (k = 2). Especially in scenarios where high-precision activity data is required, this large uncertainty limits its application in precise measurements.

[0008] For example, CN102671219A discloses a radioactive anion resin microsphere and a preparation method thereof. The radioactive anion resin microsphere of the invention is a radioactive microsphere formed by solidifying a cationic radionuclide in an anion resin with a diameter of 5 μm to 200 μm and a cross-linking degree of 1% to 20% in the form of a precipitate. The preparation method includes exchanging a non-radioactive anion precipitant into the anion resin; adding the obtained anion resin to a solution containing a cationic radionuclide, so that the cationic radionuclide in the solution reacts with the anion precipitant adsorbed inside the resin to form a precipitate, and solidifying the radionuclide inside the resin to prepare a radioactive anion resin microsphere. The cationic radionuclide in the technical scheme is Y-90 or Lu-177, and the radioactivity of the cationic radionuclide loaded in each gram of anion resin is 370MBq to 37GBq. The method of using the radioactive anion resin microsphere is to dissolve it to form a solution and then measure the activity, which has the above-mentioned defects: time-consuming, dependent on the accuracy of the standard sample, complex measurement and high cost.

[0009] As mentioned above, the current Lu-177 activity measurement method requires sample dilution in the laboratory and cannot be recycled, while in the medical field there are problems of complex efficiency scale and large measurement uncertainty. To solve these technical defects, the present invention proposes a method for directly measuring Lu-177 activity, aiming to improve the efficiency and accuracy of measurement while reducing resource waste and operational complexity.

[0010] In addition, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making the present invention, but due to space limitations, not all details and contents are listed in detail. However, this does not mean that the present invention does not have the characteristics of these prior arts. On the contrary, the present invention already has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art to the background technology. Summary of the invention

[0011] The main measurement methods widely used at present include liquid scintillation counting, coincidence counting and ionization chamber method. A significant limitation of liquid scintillation counting and coincidence counting is that in order to ensure the accuracy of measurement and avoid oversaturation, the sample to be measured usually needs to be diluted to a total activity of no more than 10,000 becquerels (Bq). In addition, once the sample is prepared and mixed with the scintillation fluid, the radionuclides are tightly bound to the liquid medium, making it extremely difficult or impossible to recover these nuclides from the scintillation fluid.

[0012] In contrast, the main challenge of the ionization chamber method, that is, measurement by using an activity meter, is that the measurement results are affected by large statistical fluctuations. This fluctuation will lead to poor repeatability of the measurement results, thus affecting the accuracy of the final measurement results. Statistical fluctuations refer to the phenomenon that the number of particles observed in a certain period of time changes over time, which is caused by the inherent random nature of the radiation detection process. Therefore, in the case of low activity or low dose rate, the measurement uncertainty of the ionization chamber method will be relatively large, which poses a limitation to measurement tasks requiring high precision.

[0013] In view of the shortcomings of the prior art, the present invention provides a method for directly measuring the activity of Lu-177 from a first aspect, the method comprising: measuring a Lu-177 sample and a corresponding blank sample to obtain the counting rate of the Lu-177 sample under different matching conditions; constructing a first calculation model for calculating the detection efficiency of the Lu-177 sample; calculating the detection efficiency based on the counting rate and the first calculation model; and calculating the activity of the Lu-177 sample based on the detection efficiency, the counting rate and the activity calculation model.

[0014] Compared to the prior art, which has the limitation that dilution measurement must be performed in the laboratory to achieve a low uncertainty level or direct measurement on-site has a high uncertainty level, the present invention can directly measure and calculate the accurate activity of the Lu-177 sample in the laboratory or on-site without dilution. According to a preferred embodiment, the method for calculating the detection efficiency also includes: calculating the free parameters of the photomultiplier tube of the measuring device for measuring the count rate based on the second calculation model and the count rate, and calculating the detection efficiency of the Lu-177 sample based on the free parameters and the first calculation model. The present invention associates the free parameters of the photomultiplier tube of the measuring device with the detection efficiency, and can directly calculate the detection efficiency of the Lu-177 sample.

[0015] According to a preferred embodiment, the method further comprises: calculating the total detection efficiency based on the first calculation model, the total detection efficiency being only related to the beta particles and gamma rays emitted when the matrix of Lu-177 decays in the sample bottle; the calculation formula of the total detection efficiency is:

[0016]

[0017] Where ε represents the total detection efficiency, P 1 , P 3 and P 4 Respectively represent γ 3 , β 3 and β 4 The branching ratio; Represents γ 3 Escape probability in the sample matrix; Represents γ 3The detection efficiency of transitions; and Respectively represent β 3 and β 4 The detection efficiency of the transition.

[0018] According to a preferred embodiment, the method further comprises: in the second calculation model, the calculation relationship between the count rate and the detection efficiency of each type of particles is:

[0019]

[0020] Among them, R T represents the count rate of T measured experimentally; R T,B Represents the T count rate of the background sample; R AB represents the AB counting rate measured experimentally; R AB,B Represents the AB count rate of the background sample; R BC represents the experimentally measured BC counting rate; R BC,B Represents the BC count rate of the background sample; R AC represents the experimentally measured AC count rate; R AC,B Represents the AC count rate of the background sample; ε T Indicates that the T to be solved meets the total detection efficiency; ε AB Indicates that the AB to be solved meets the total detection efficiency; ε BC Indicates that the BC to be solved meets the total detection efficiency; ε AC It means that the AC to be solved meets the total detection efficiency.

[0021] According to a preferred embodiment, the calculation formula of the activity calculation model is:

[0022]

[0023] Where A represents activity; R D represents the D count rate of Lu-177 sample; R D,B Indicates the D count rate of the background sample; T m Indicates the time point of Lu-177 sample measurement; T r represents the reference time point; k hc represents the half-life correction factor; T 1 / 2 Represents the half-life of the radionuclide; ε D Indicates that D meets the total detection efficiency; ε T It means that T corresponds to the total detection efficiency.

[0024] As described above, the method of the present invention meets the requirements of simple sample preparation, recyclable nuclides, and low uncertainty, and improves the capability and level of the existing Lu-177 measurement method. Specifically, the matrix mixed with Lu177 is water or 1 mol / L hydrochloric acid. Water and hydrochloric acid as matrices are both volatile substances, so they can be evaporated after the sample measurement is completed, so that Lu177 can continue to be used.

[0025] The present invention provides a Lu-177 activity direct measurement device from a second aspect, the device includes a three-tube coincident liquid scintillation counting device and a processor. The three-tube coincident liquid scintillation counting device is used to measure the Lu-177 sample and the corresponding blank sample to obtain the counting rate of the Lu-177 sample under different coincident conditions; the processor is internally constructed with a first calculation model for calculating the detection efficiency of the Lu-177 sample and an activity calculation model for calculating the activity; when the counting rate is input into the processor, the processor is configured to: calculate the detection efficiency based on the counting rate and the first calculation model; calculate the activity of the Lu-177 sample based on the detection efficiency, the counting rate and the activity calculation model. Compared with the prior art, which has the limitation that dilution measurement must be performed in the laboratory to achieve a low uncertainty level or a high uncertainty level of direct measurement on site, the present invention can directly measure and calculate the accurate activity of the Lu-177 sample in the laboratory or on site without dilution. According to a preferred embodiment, the processor is further configured to: calculate free parameters of a photomultiplier tube of a measuring device for measuring the count rate based on the second calculation model and the count rate, and calculate the detection efficiency of the Lu-177 sample based on the free parameters and the first calculation model.

[0026] According to a preferred embodiment, the processor is further configured to: calculate the total detection efficiency based on the first calculation model, the total detection efficiency is only related to the beta particles and gamma rays emitted when the matrix of Lu-177 decays in the sample bottle; the calculation formula of the total detection efficiency is:

[0027]

[0028] Where ε represents the total detection efficiency, which can be used to calculate the detection efficiency under different coincidence conditions (including T, D, AB, BC and AC coincidence), P 1 , P 3 and P 4 Respectively represent γ 3 , β 3 and β 4 The branching ratio; Represents γ 3 Escape probability in the sample matrix; Represents γ 3 The detection efficiency of transitions; and Respectively represent β 3 and β 4 The detection efficiency of the transition.

[0029] According to a preferred embodiment, the calculation formula of the activity calculation model is:

[0030]

[0031] Where A represents activity; R D represents the D count rate of Lu-177 sample; R D,B Indicates the D count rate of the background sample; T m Indicates the time point of Lu-177 sample measurement; T r represents the reference time point; k hc represents the half-life correction factor; T 1 / 2 Represents the half-life of the radionuclide; ε D Indicates that D meets the total detection efficiency; ε T It means that T corresponds to the total detection efficiency.

[0032] As described above, the device of the present invention meets the requirements of simple sample preparation, recoverable nuclides, and low uncertainty, and improves the capability and level of existing Lu-177 measurement devices.

[0033] The present invention provides a processor for direct measurement of Lu-177 activity from a third aspect, wherein a first calculation model for calculating the detection efficiency of Lu-177 samples and an activity calculation model for calculating the activity are constructed inside the processor; the processor is configured to: when a counting rate is input into the processor, calculate the detection efficiency based on the counting rate and the first calculation model; and calculate the activity of the Lu-177 sample based on the detection efficiency, the counting rate and the activity calculation model.

[0034] As described above, the activity data calculated by the processor of the present invention has the advantage of low uncertainty. Although both the liquid scintillation method and the method of the present invention need to rely on the decay outline of Lu-177 and related decay data when calculating the detection efficiency, the first calculation model proposed by the present invention can largely ignore the influence of multiple decay paths on the detection efficiency and the partial contribution of internal conversion electrons, thereby making the entire calculation process more concise and clear than the liquid scintillation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic flow chart of the method for direct measurement of Lu-177 activity provided by the present invention;

[0036] Figure 2 It is a schematic diagram of seven decay paths of the process of Lu-177 decaying to the Hf-177 ground state provided by the present invention;

[0037] Figure 3 It is a schematic diagram of the module connection relationship of the processor for direct measurement of Lu-177 activity provided by the present invention;

[0038] Figure 4 It is a logical schematic diagram of the Lu-177 activity direct measurement device provided by the present invention.

[0039] Reference numerals list

[0040] 100: three-tube liquid scintillation counting device; 200: processor; 210: first calculation model; 220: second calculation model; 230: activity calculation model. DETAILED DESCRIPTION

[0041] The following is a detailed description with reference to the accompanying drawings.

[0042] Example 1

[0043] Lu-177 is a short-lived decay nuclide with a half-life of 6.647 days. It decays to the excited state or ground state of Hf-177 through a β-transition. When Lu-177 decays to the excited state of Hf-177, Hf-177 undergoes a γ transition to de-excite in the form of emitting γ rays or internal conversion electrons and to a lower energy level or ground state of Hf-177. The decay diagram of Lu-177 is shown below. Figure 2 As shown, the process from Lu-177 decaying to the Hf-177 ground state includes 7 decay paths.

[0044] In the process of Lu-177 decaying to the Hf-177 ground state, multiple decay paths have a significant adverse effect on activity measurements. First, incomplete measurements are a key issue because some decay paths may release low-energy rays that may be filtered by the threshold of the detector or absorbed by the material, resulting in some decay events not being detected, thereby underestimating the activity. Second, differences in detection efficiency are also an important factor. Due to the different types and energies of rays released by different decay paths, the detector has different detection efficiencies for various rays, which leads to deviations in the measurement results. In addition, the increase in background noise is also a problem. Multiple decay paths may produce multiple rays, which increases background noise, reduces the signal-to-noise ratio of the measurement, and affects the measurement accuracy. The computational complexity of the decay constant is also a challenge because the branching ratios and decay constants of multiple paths need to be accurately determined, otherwise it will affect the accurate calculation of the activity. Finally, time dependence is also a consideration. If the half-lives of different paths are different, the change of activity over time may be more complicated, affecting the accuracy of the measurement. Therefore, multiple decay paths increase the complexity and uncertainty of activity measurements, affecting the accuracy and reliability of measurements.

[0045] At present, for the activity measurement of radiopharmaceutical Lu-177, the mainstream methods in the laboratory include the liquid scintillation triple-tube double-tube coincidence ratio (TDCR) method, the liquid scintillation efficiency tracer method and the 4πβ-γ coincidence method. In the medical field or the corresponding isotope production site, the commonly used measurement method is to use a medical activity meter to measure the activity of high-activity Lu-177 solution. However, whether in the measurement in the laboratory or in the medical field, the above measurement methods have some defects.

[0046] For example, in the methods mainly used in the laboratory, when the activity of Lu-177 samples is measured using such liquid scintillation or composite-based methods, the total activity of the sample to be measured generally needs to be controlled within 10,000 Bq to ensure that the sample is not affected by channel blockage or pulse accumulation due to excessive counting rate during the measurement process. Therefore, when measuring this nuclide, the Lu-177 solution to be tested needs to be diluted in the laboratory before sample preparation and measurement. At the same time, when measuring in the laboratory, since such samples are generally prepared as liquid scintillation samples or thin film source samples, the Lu-177 samples cannot be recovered after the measurement is completed, and the Lu-177 samples are generally treated as radioactive waste. On the other hand, when a medical activity meter used in a medical setting or an isotope production site measures Lu-177, although high activity level measurements can be made and the Lu-177 solution can continue to be used after the measurement, the activity meter must be calibrated for efficiency using a Lu-177 solution of known activity before measurement can be performed, and the uncertainty of the measurement result is generally not less than 3% (k=2).

[0047] In view of the deficiencies in the prior art, the present invention provides a method, device and processor for directly measuring Lu-177 activity.

[0048] The Lu-177 activity direct measuring device of the present invention is as follows: Figure 4 As shown, it includes a three-tube liquid scintillation counting device 100 and a processor 200. The processor 200 is used for data processing of the Lu-177 activity direct measurement method of the present invention. The processor 200 is connected to the three-tube liquid scintillation counting device 100 for communication and receives data. The communication connection mode includes a wired connection and a wireless connection mode. The wired connection mode refers to transmitting data through a connecting line. The wireless communication mode refers to transmitting data through a wireless communication signal.

[0049] The physical hardware of the processor 200 may be a dedicated integrated chip, a server, or a combination thereof. The processor 200 may also be a CPU. Preferably, the processor 200 may also be a remote cloud server.

[0050] Preferably, the present invention can also provide a three-tube liquid scintillation counting device 100, in which a processor 200 for performing the data processing operation of the present invention is installed. The present invention can also provide a processor 200 dedicated to calculating the activity of Lu-177. Figure 3 As shown, a first calculation model 210, a second calculation model 220 and an activity calculation model 230 are provided in the processor 200. The first calculation model 210, the second calculation model 220 and the activity calculation model 230 establish data connection relationships with each other in sequence.

[0051] like Figure 1 and Figure 4 As shown, the direct measurement method of Lu-177 activity of the present invention includes S1 to S3.

[0052] S1: Measure the Lu-177 sample and its corresponding blank sample to obtain the counting rate of the Lu-177 sample under different matching conditions.

[0053] S2: Constructing a first calculation model 210 for calculating the detection efficiency of the Lu-177 sample. The detection efficiency is calculated based on the count rate and the first calculation model 210.

[0054] S3: Calculate the activity of the Lu-177 sample based on the detection efficiency, the counting rate and the activity calculation model 230.

[0055] First, the Lu-177 sample needs to be prepared. In order to achieve the purpose of recovering the Lu-177 nuclide, the matrix of the Lu-177 sample can use volatile liquid materials such as pure water or dilute hydrochloric acid.

[0056] Both purified water and dilute hydrochloric acid are relatively volatile substances that can be removed by evaporation or heating under appropriate conditions, leaving the Lu-177 compound in solid form for subsequent separation and purification steps.

[0057] Compared with the prior art, the present invention uses pure water or dilute hydrochloric acid as the matrix of the Lu-177 sample, which not only helps to achieve effective recovery of the radioactive isotope, but also brings significant benefits in terms of environmental protection and cost-effectiveness.

[0058] In terms of environmental protection, the amount of radioactive waste can be significantly reduced through effective recycling methods, which greatly reduces the risk of long-term impact on the ecosystem and helps save resources because Lu-177, a valuable radioactive isotope resource, can be reused, reducing the demand for raw materials.

[0059] From a cost-effectiveness perspective, Lu-177 is an expensive medical isotope, and its effective recycling and reuse can significantly save the cost of purchasing new raw materials and at the same time reduce the high cost of radioactive waste disposal, including special packaging, transportation, and the selection of the final disposal site.

[0060] The steps for preparing Lu-177 samples include:

[0061] S01: Use a 20 mL sample bottle to fill 5-15 mL of matrix, and add undiluted Lu-177 solution to the matrix. After fully shaking and mixing, measure the mixture. Preferably, the sample bottle can be a plastic liquid scintillation counting bottle.

[0062] S02: Use a 20 mL sample bottle to fill it with the same volume of matrix, but do not add Lu-177 solution. Use it as a blank sample to deduct the background count.

[0063] S1: Measure the Lu-177 sample and the corresponding blank sample to obtain the count rate of the Lu-177 sample under different matching conditions, such as Figure 4 shown.

[0064] The Lu-177 sample and the corresponding blank sample are sequentially placed on a three-tube coincident liquid scintillation counting device 100 for measurement to obtain the counting rate of the blank sample under different coincident conditions.

[0065] The Lu-177 sample was placed in a liquid scintillation counting apparatus equipped with three photomultiplier tubes (three-tube liquid scintillation counting apparatus 100) for measurement.

[0066] Preferably, the three photomultiplier tubes are usually installed at an angle of 120 degrees to each other, that is, the relative position between them enables each photomultiplier tube to receive photon signals from different directions. When a radioactive nuclide decays, the generated beta particles will cause scintillation in the scintillation fluid, generating multiple photons. These photons will be detected by different photomultiplier tubes simultaneously or almost simultaneously. Only when the three photomultiplier tubes detect photon signals within the same time window will the coincidence liquid scintillation counting device record it as a valid count. This method is called "coincidence measurement".

[0067] S2: Construct a first calculation model 210 for calculating the detection efficiency of the Lu-177 sample, and calculate the detection efficiency based on the count rate and the first calculation model 210, such as Figure 4 shown.

[0068] S21: Construct a first calculation model 210 for calculating the detection efficiency of the Lu-177 sample.

[0069] When the matrix in the sample bottle decays, the Lu-177 sample emits beta particles and gamma rays. When the energy of these rays or particles is high enough, Cherenkov photons are generated in the matrix. The relationship between the number of Cherenkov photons generated, dk, and the distance dx traveled by the particle in the matrix is:

[0070]

[0071] In the above formula, z represents the charge carried by the electron, which is 1; α FS represents the fine structure constant, which is approximately 1 / 137; λ 1 Represents the lower limit of the wavelength of Cherenkov light; λ 2 represents the upper limit of the wavelength of Cherenkov light; β represents the phase velocity of the particle; n represents the refractive index of the matrix; ρ represents the density of the matrix, in g·cm -3 ; dE / dx represents the stopping power of the matrix for electrons, in MeV cm 2 g-1; E represents the initial energy of the emitted beta particle or secondary electron, in keV; E th The energy threshold of the Cherenkov effect is related to the refractive index of the matrix and is expressed in keV. For example, for a 1 mol / L hydrochloric acid matrix, E th is 256keV. k(E) represents the number of Cherenkov photons produced by a beta particle with energy E in the matrix.

[0072] The calculation formula for the first calculation model 210 to calculate the detection efficiency of any emitted particle under different matching conditions is as follows.

[0073]

[0074] In the above formula, S(E) represents the shape spectrum of β particles emitted by Lu-177 or the secondary electron energy distribution spectrum generated by γ rays in the matrix; E max Indicates the maximum endpoint energy of the β-shaped spectrum or secondary electron energy distribution spectrum, in keV; α 1 , α 2 and α 3 They represent the anisotropy coefficients of Cherenkov light in the light chamber; q A ,q B and q C They represent the free parameters of the photomultiplier tube. n (α m ,E) represents the energy of the β particle E in the tube n and the anisotropy coefficient α m The detection efficiency under the premise of ε T Indicates that T meets the total detection efficiency; ε ABIndicates that AB meets the detection efficiency; ε BC Indicates that BC meets the detection efficiency; ε AC Indicates AC compliance detection efficiency; ε D It means that D meets the total detection efficiency. By constructing the first calculation model 210, the detection efficiency contribution of multiple decay paths and the part of internal conversion electrons can be ignored to the greatest extent, making the entire calculation process more concise and convenient compared with the liquid scintillation method.

[0075] Preferably, according to the analysis of the Lu-177 decay diagram and the refractive index of the matrix of the commonly used Cherenkov sample (generally 1 mol / L HCl or pure water), E th is 256keV (1mol / L HCl) or 262keV (pure water), so it can be seen that when the detection efficiency of the Lu-177 sample is calculated using the first calculation model 210, only some of the β particles and γ rays emitted by it need to be considered. When the matrix is ​​1mol / L HCl, the detection efficiency of the Lu-177 sample only needs to consider two β particles and one γ ray.

[0076] Preferably, the calculation formula of the total detection efficiency in the first calculation model 210 is used to calculate the total detection efficiency of the Lu-177 sample, such as Figure 4 shown.

[0077] For example, the calculation formula for the total detection efficiency of Lu-177 sample in hydrochloric acid matrix can be expressed as:

[0078]

[0079] In this formula, ε can be used to calculate the total detection efficiency corresponding to the situation using the detection efficiency formulas of formulas (3) to (7), where P 1 , P 3 and P 4 Respectively represent γ 3 , β 3 and β 4 The branching ratio; Represents γ 3 Escape probability in the sample matrix. It can be calculated by theoretical methods or Monte Carlo methods. Represents γ 3 The detection efficiency of transitions; and Respectively represent β 3 and β 4 The detection efficiency of the transition.

[0080] Preferably, for the first calculation model 210, considering the quantum efficiency asymmetry of the photomultiplier tube, the weighted combination β 3 and β4 The shape spectrum of the transition and the γ 3 The secondary electron energy distribution spectrum generated by the radiation in the matrix is ​​used to obtain the weighted total electron emission spectrum, which can be used as S(E) and substituted into formulas (3) to (7) to calculate the detection efficiency.

[0081]

[0082] Among them, SES is γ 3 The energy distribution spectrum of secondary electrons generated by the radiation in the matrix, and β 3 and β 4 The shape spectrum of the transition.

[0083] S22 : Calculate the detection efficiency based on the count rate and the first calculation model 210 .

[0084] S221: Calculate the free parameters of the photomultiplier tube of the measuring device for measuring the count rate based on the second calculation model 220 and the count rate, such as Figure 4 shown.

[0085] The second calculation model 220 is as follows, that is, the relationship between the count rate and the formula (3) to the formula (7) in the first calculation model 210 is:

[0086]

[0087] In the above formula, R T It represents the experimentally measured count rate of T, in s -1 ; R T,B Represents the T count rate of the background sample, in s -1 ; R AB Indicates the experimentally measured AB count rate, in s -1 ; R AB,B Indicates the AB count rate of the background sample, in s -1 ; R BC Indicates the experimentally measured BC count rate, in s -1 ; R Bc,B Indicates the BC count rate of the background sample, in s -1 ; R AC Indicates the experimentally measured AC count rate in s -1 ; R AC,B Indicates the AC count rate of the background sample, in s -1 .

[0088] The obtained count rate is input into the second calculation model 220 to solve for the free parameter q of the photomultiplier tube. A ,qB and q C .

[0089] S222: Calculate the detection efficiency of the Lu-177 sample based on the free parameters and the first calculation model 210. The detection efficiency includes T and the total detection efficiency ε T and D are consistent with the total detection efficiency ε D .

[0090] The free parameter q of the photomultiplier tube is A ,q B and q C Substituting into formula (6) and formula (7) in the first calculation model 210, the total detection efficiency ε of T can be calculated. T and D are consistent with the total detection efficiency ε D .

[0091] The calculated T is consistent with the total detection efficiency ε T and D are consistent with the total detection efficiency ε D The following conditions should be met:

[0092]

[0093] In the above formula, R D It represents the experimentally measured count rate of T, in s -1 ; R D,B Represents the T count rate of the background sample, in s -1 .

[0094] S3: Calculate the activity of the Lu-177 sample based on the detection efficiency, counting rate and activity calculation model 230, such as Figure 4 shown.

[0095] The calculated T is matched to the total detection efficiency ε T , D complies with the total detection efficiency ε D The counting rate obtained by using the three-tube liquid scintillation counting device 100 is substituted into the activity calculation model 230 to obtain the activity of the measured Lu-177 sample at the reference time.

[0096] The activity calculation model 230 is shown as follows:

[0097]

[0098] In the above formula, A represents activity; R D Indicates the D count rate of the sample, in s -1 ; R DB Indicates the D count rate of the background sample, in s -1 ; T m Indicates the time point of sample measurement; T rrepresents the reference time point; k hc represents the half-life correction factor, which is a function of the measurement time t meas and the half-life of the nuclide being measured, T 1 / 2 Function of T 1 / 2 Indicates the half-life of a radionuclide, in units of T m and T r The unit of determination; t meas Indicates the total time of sample measurement in seconds.

[0099] Compared with the liquid scintillation method, coincidence method and ionization chamber measurement method in the prior art, the method of the present invention has the following advantages:

[0100] First, compared with the liquid scintillation and coincidence methods, the present invention can increase the total activity of the sample to be tested by two orders of magnitude. In addition, the Lu-177 solution to be tested can be recycled, and the sample preparation process is simple, which is suitable for on-site measurement.

[0101] Second, although both the liquid scintillation method and the method of the present invention need to rely on the decay scheme and related decay data of Lu-177 when calculating the detection efficiency, the first calculation model 210 proposed by the method of the present invention can largely ignore the impact of multiple decay paths on the detection efficiency and the partial contribution of internal conversion electrons, thereby making the entire calculation process more concise and clear than the liquid scintillation method.

[0102] Third, when the sample preparation method is the same, compared with the ionization chamber measurement method, the uncertainty of the measurement result of the present invention is one order of magnitude lower, providing higher measurement accuracy.

[0103] Example 2

[0104] This embodiment is a further description of Embodiment 1, and repeated contents will not be repeated here.

[0105] This example provides a set of exemplary experimental data for the implementation of the present invention.

[0106] For example, a Lu-177 sample with 1 mol / L hydrochloric acid as the matrix and a corresponding blank sample are prepared. The two types of samples are placed in a three-tube liquid scintillation counting device 100 for measurement to obtain the corresponding counting rates. The counting rates are shown in the following table.

[0107]

[0108] Substituting each count rate obtained by measurement into the second calculation model 220 to solve for free parameters, we obtain: A =0.01834,q B =0.01566,q C=0.01752.

[0109] Calculation is performed based on the first calculation model 210 to obtain the data detection efficiency ε D =0.004600 and target detection efficiency ε T =0.000396.

[0110] At this time, ε T / ε D It is equal to the count rate ratio of T to D, which satisfies formula (11).

[0111] The D of the Lu-177 sample obtained is consistent with the total detection efficiency ε D , T meets the total detection efficiency ε T The experimental data such as the counting rate are substituted into the activity calculation model 230 for calculation, and the activity of the prepared Lu-177 sample is obtained to be 3.25(3)×10 5 Bq, the mass of Lu177 sample added is 0.08446g, so the specific activity of Lu177 sample is 3.76(3)MBq / g, and the reference time is November 28, 2024. To verify the reliability of the results, the same batch of Lu177 samples were measured for activity using the liquid scintillation method, and the specific activity calculation result was 3.75(2)MBq / g. The result deviation between the two methods was less than 0.3%, which was consistent within the uncertainty range.

[0112] It should be noted that the above-mentioned specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the present invention specification and its drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of the present invention is defined by the claims and their equivalents. The present invention specification contains multiple inventive concepts, such as "preferably" and "according to a preferred embodiment", which means that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to file a divisional application based on each inventive concept.

Claims

1. A method for directly measuring Lu-177 activity, characterized in that: The method comprises: The Lu-177 sample and the corresponding blank sample are measured to obtain the counting rate of the Lu-177 sample under different coincidence conditions; Constructing a first calculation model (210) for calculating the detection efficiency of the Lu-177 sample; calculating the detection efficiency based on the count rate and the first calculation model (210); The activity of the Lu-177 sample is calculated based on the detection efficiency, the counting rate and the activity calculation model (230).

2. The method according to claim 1, characterized in that The method for calculating the detection efficiency also includes: calculating free parameters of a photomultiplier tube of a measuring device for measuring the count rate based on a second calculation model (220) and the count rate, The detection efficiency of the Lu-177 sample is calculated based on the free parameters and the first calculation model (210).

3. The method according to claim 1 or 2, characterized in that: The method further comprises: calculating the total detection efficiency based on the first calculation model (210), The total detection efficiency is only related to the beta particles and gamma rays emitted when the Lu-177 decays in the matrix in the sample bottle; The calculation formula of the total detection efficiency is: Where ε represents the total detection efficiency, P1, P3, and P4 represent the branching ratios of γ3, β3, and β4, respectively; represents the escape probability of γ3 in the sample matrix; represents the detection efficiency of γ3 transition; and represent the detection efficiency of β3 and β4 transitions, respectively.

4. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: in the second calculation model (220), the calculation relationship between the counting rate and the detection efficiency of each type of particle is: Among them, R T represents the count rate of T measured experimentally; R T,B Represents the T count rate of the background sample; R AB represents the AB counting rate measured experimentally; R AB,B Represents the AB count rate of the background sample; R BC represents the experimentally measured BC counting rate; R BC,B Represents the BC count rate of the background sample; R AC represents the experimentally measured AC count rate; R AC,B Indicates the AC count rate of the background sample; Φ T Indicates that the T to be solved meets the total detection efficiency; Φ AB Indicates that the AB to be solved meets the total detection efficiency; ε BC Indicates that the BC to be solved meets the total detection efficiency; ε AC It means that the AC to be solved meets the total detection efficiency.

5. The method according to any one of claims 1 to 4, characterized in that: The calculation formula of the activity calculation model (230) is: Where A represents activity; R D represents the D count rate of Lu-177 sample; R D,B Indicates the D count rate of the background sample; T m Indicates the time point of Lu-177 sample measurement; T r represents the reference time point; k hc represents the half-life correction factor; T 1 / 2 Represents the half-life of the radionuclide; ε D Indicates that D meets the total detection efficiency; ε T It means that T corresponds to the total detection efficiency.

6. A Lu-177 activity direct measurement device, characterized in that: The device comprises: A three-tube coincident liquid scintillation counting device (100) is used to measure a Lu-177 sample and a blank sample corresponding thereto to obtain the counting rate of the Lu-177 sample under different coincident conditions; A processor (200) having a first calculation model (210) for calculating the detection efficiency of a Lu-177 sample and an activity calculation model (230) for calculating the activity constructed therein; In the case where the count rate is input to the processor (200), the processor (200) is configured to: Calculating the detection efficiency based on the count rate and the first calculation model (210); The activity of the Lu-177 sample is calculated based on the detection efficiency, the counting rate and the activity calculation model (230).

7. The device according to claim 6, characterized in that The processor (200) is also configured to: calculating free parameters of a photomultiplier tube of a measuring device for measuring the count rate based on the second calculation model (220) and the count rate, The detection efficiency of the Lu-177 sample is calculated based on the free parameters and the first calculation model (210).

8. The device according to claim 6 or 7, characterized in that The processor (200) is further configured to: calculate the total detection efficiency based on the first calculation model (210), The total detection efficiency is only related to the beta particles and gamma rays emitted when the Lu-177 decays in the matrix in the sample bottle; The calculation formula of the total detection efficiency is: Where ε represents the total detection efficiency, P1, P3, and P4 represent the branching ratios of γ3, β3, and β4, respectively; represents the escape probability of γ3 in the sample matrix; represents the detection efficiency of γ3 transition; and represent the detection efficiency of β3 and β4 transitions, respectively.

9. The device according to any one of claims 6 to 8, characterized in that: The calculation formula of the activity calculation model (230) is: Where A represents activity; R D represents the D count rate of Lu-177 sample; R D,B Indicates the D count rate of the background sample; T m Indicates the time point of Lu-177 sample measurement; T r represents the reference time point; k hc represents the half-life correction factor; T 1 / 2 Represents the half-life of the radionuclide; ε D Indicates that D meets the total detection efficiency; ε T It means that T corresponds to the total detection efficiency.

10. A processor for direct measurement of Lu-177 activity, characterized in that: The processor (200) has a first calculation model (210) for calculating the detection efficiency of the Lu-177 sample and an activity calculation model (230) for calculating the activity. The processor (200) is configured to: When a count rate is input to the processor (200), the detection efficiency is calculated based on the count rate and the first calculation model (210); The activity of the Lu-177 sample is calculated based on the detection efficiency, the counting rate and the activity calculation model (230).

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