Methods for analyzing alpha-ray spectra obtained from radiation sources

Abstract

This invention relates to a method for analyzing alpha-ray spectra obtained from a radiation source, wherein the radiation source comprises a first nuclide and a second nuclide that are different from each other. The method comprises the following steps: obtaining a simulated spectrum of alpha rays emitted from the first nuclide and the second nuclide by simulating the radioactivity functions of the first nuclide and the second nuclide; measuring the alpha rays emitted from the radiation source to obtain an alpha-ray spectrum; and decomposing the alpha-ray spectrum into a first alpha-ray spectrum emitted from the first nuclide and a second alpha-ray spectrum emitted from the second nuclide based on the simulated spectrum.

Description

Technical Field

[0001] This invention relates to a method for analyzing α-ray spectra obtained from a radiation source. Background Technology

[0002] Radiotherapy using nuclides that emit alpha rays (targeted alpha therapy: TAT) has recently attracted attention.

[0003] For TAT, when the corresponding nuclide (parent nuclide) decays to produce a daughter nuclide, the daughter nuclide is also present at the site of treatment.

[0004] A planned amount of daughter nuclides that emit alpha rays can maximize the therapeutic effect, but an excessive amount of daughter nuclides leads to increased toxicity.

[0005] Therefore, it is necessary to determine whether the corresponding daughter nuclide is produced by the parent nuclide at the site to be treated, or by a parent nuclide at another site that is introduced to that site through its physiological action. Summary of the Invention

[0006] Technical issues

[0007] Therefore, the purpose of this disclosure is to provide a method for analyzing alpha-ray spectra obtained from a radiation source.

[0008] Technical solution

[0009] To achieve the above-mentioned objectives of this disclosure, a method for analyzing alpha-ray spectra obtained from a radiation source, wherein the radiation source comprises a first nuclide and a second nuclide that are different from each other, the method comprising: obtaining a simulated spectrum of alpha-rays emitted from the first nuclide and the second nuclide by simulating the radioactivity functions of the first nuclide and the second nuclide; obtaining an alpha-ray spectrum by measuring the alpha-rays emitted from the radiation source; and decomposing the alpha-ray spectrum into a first alpha-ray spectrum of alpha-rays emitted from the first nuclide and a second alpha-ray spectrum of alpha-rays emitted from the second nuclide based on the simulated spectrum.

[0010] The second nuclide can be a daughter nuclide of the first nuclide.

[0011] The combination of the first nuclide and the second nuclide can be [ 225 Ac, 213 Bi]、[ 211 At, 212 Po]、[ 212 Bi, 212 Po]、[ 213 Bi, 213 Po]、[ 212 Pb, 212 Po]、[223 Ra, 212 Bi] and [ 227 Th, 211 Any combination of [Bi].

[0012] The radiation source may include a first radiation source and a second radiation source, and the first radiation source and the second radiation source may have different distributions of the first nuclide and the second nuclide.

[0013] In the measurement, the first radiation source and the second radiation source may be spaced apart from each other.

[0014] The method may further include, after the decomposition, deriving the ratio of alpha rays from the first radiation source to alpha rays from the second radiation source at a specific measurement location.

[0015] The measurements can be taken on replicas of human body parts.

[0016] The radioactivity function can be obtained based on information about the half-life and emission probability of the first and second nuclides.

[0017] The decomposition of the measured spectrum may include the step of obtaining the coefficient ratio between the first α-ray spectrum and the second α-ray spectrum at a specific measurement location.

[0018] To achieve the above-mentioned objectives of this disclosure, a method for analyzing alpha-ray spectra obtained from a radiation source, wherein the radiation source comprises a first radiation source containing a parent nuclide and a second radiation source spaced apart from the first radiation source and containing a daughter nuclide of the parent nuclide, the method comprising: obtaining a simulated spectrum of alpha-rays emitted from the parent nuclide and the daughter nuclide by simulating the radioactivity functions of the parent nuclide and the daughter nuclide; obtaining an alpha-ray spectrum by measuring the alpha-rays emitted from the radiation source; decomposing the alpha-ray spectrum into a first alpha-ray spectrum of alpha-rays emitted from the parent nuclide and a second alpha-ray spectrum of alpha-rays emitted from the daughter nuclide based on the simulated spectrum; and classifying alpha-rays measured at specific locations as alpha-rays from the parent nuclide and alpha-rays from the daughter nuclide.

[0019] The simulated spectrum can be stored in the form of a library before the measurement, and during the measurement, the simulated spectrum in the library can be used to decompose the α-ray spectrum.

[0020] The measurements can be taken on replicas of human body parts.

[0021] Beneficial effects

[0022] This disclosure provides a method for analyzing alpha-ray spectra obtained from a radiation source. Attached Figure Description

[0023] Figure 1 This is a flowchart of a method for analyzing α-ray spectra according to an embodiment of this disclosure.

[0024] Figure 2 The simulated spectrum obtained from the experimental examples of this disclosure is shown.

[0025] Figure 3 and Figure 4 A replica of a human body part and a radiation source are shown in the experimental examples used in this disclosure.

[0026] Figure 5 This is a two-dimensional image of the α-ray distribution obtained from the experimental examples of this disclosure.

[0027] Figure 6 The α-ray spectrum in region 2 of the experimental example of this disclosure is shown.

[0028] Figures 7A to 7D The first α-ray spectrum and the second α-ray spectrum in each region of the experimental examples of this disclosure are shown.

[0029] Figure 8A and Figure 8B This is from the experimental examples disclosed in this publication. 225 Ac's alpha rays and from 213 Image of Bi's α-rays.

[0030] Figure 9 The test examples shown in this disclosure are from 225 Images of Ac's α-rays and from 213 A combination of images of Bi's α-rays.

[0031] Figure 10 A comparison is shown between the radioactivity of the actually injected nuclide and the radioactivity of the expected nuclide in the test example of this disclosure. Detailed Implementation

[0032] The present disclosure will be described in more detail below with reference to the accompanying drawings.

[0033] Because the accompanying drawings are merely examples shown to illustrate the technology of this disclosure more specifically, the technology of this disclosure is not limited to the technology shown in the drawings. Furthermore, in the drawings, to illustrate the relationships between components, the dimensions, spacing, etc., of each component may be exaggerated.

[0034] In the following description, the difference between the parent and daughter nuclides in radiotherapy using alpha-emitting nuclides will be described as an example, but this disclosure is not limited thereto. This disclosure can be used to monitor alpha-emitting nuclides required for the safety of nuclear power plants, control the quality of alpha-emitting nuclide extraction systems (a system that produces radioactive isotopes by separating daughter nuclides from parent nuclides), etc.

[0035] Reference Figure 1 A method for analyzing α-ray spectra according to this disclosure is described.

[0036] First, at S100, the radiation source to be analyzed can be identified.

[0037] The radiation source may include a first nuclide and a second nuclide.

[0038] The first and second nuclides may have a parent-daughter relationship, but are not limited to it. They may be selected from [ 225 Ac, 213 Bi]、[ 211 At, 212 Po]、[ 212 Bi, 212 Po]、[ 213 Bi, 213 Po]、[ 212 Pb, 212 Po]、[ 223 Ra, 212 Bi] and [ 227 Th, 211 The combination of [Bi].

[0039] Next, in S200, the simulated spectrum can be obtained.

[0040] The simulated spectrum can be obtained using the radioactivity functions of the first and second nuclides. The radioactivity functions can be obtained based on the half-life and emission information of each nuclide, and can be obtained by inputting the information into the Bateman equation in Equation 1 below, but is not limited thereto. The radioactivity function of the first nuclide can reflect information about the first nuclide and its daughter nuclides, and the radioactivity function of the second nuclide can reflect information about the second nuclide and its daughter nuclides.

[0041] <Equation 1>

[0042]

[0043]

[0044]

[0045] Where t represents a specific time, λ i and N i Let N represent the decay constant and the amount of the i-th nuclide on the decay curve of the selected nuclide, respectively, and N. n (t) represents the amount of the nth nuclide present at a specific time t.

[0046] By using simulations of the obtained radioactivity function, information about the initial radioactivity of the first nuclide (e.g., 10 kBq), and information about the initial radioactivity of the second nuclide (e.g., 10 kBq), a simulated spectrum (simulated energy spectrum) of α-rays emitted from the first and second nuclides can be obtained.

[0047] For simulation, Monte Carlo simulation can be used, but is not limited to, using the Geant4 application (GATE) code for tomographic transmission. In other implementations, other codes such as FLUKA code, MCNPX code, or Geant4 code can be used.

[0048] In the simulation, the coefficient information of each energy of the first and second nuclides can be obtained, and the simulated spectrum can be obtained based on the obtained coefficient information of each energy.

[0049] Next, in S300, the alpha-ray spectrum can be obtained by measuring the alpha rays emitted from the radiation source.

[0050] In the measurement, the alpha spectrum of each two-dimensional pixel can be obtained by injecting a radiation source into the sample and taking pictures of it with an alpha-ray imaging device.

[0051] Alpha-ray imaging devices can be prepared by combining scintillators, optical sensors, and other components.

[0052] The sample can be a slice of a small animal or a replica of a human body part. The replica can be an organ such as a kidney, but is not limited to this.

[0053] In the measurement, multiple radiation sources spaced apart from each other can be provided, and the distribution of nuclides in each radiation source can be different. For example, the first radiation source may contain only the first nuclide, while the second radiation source may contain only the second nuclide, or the first radiation source may contain both the first and second nuclides, while the second radiation source contains only the second nuclide. Optionally, each of the first and second radiation sources may contain both the first and second nuclides, but the ratio of the first to the second nuclides in the first and second radiation sources can be different.

[0054] Then, in S400, the α-ray spectrum can be decomposed.

[0055] The alpha-ray spectrum can be decomposed into a first alpha-ray spectrum of alpha rays emitted from a first nuclide and a second alpha-ray spectrum of alpha rays emitted from a second nuclide.

[0056] The decomposition process is described in detail below.

[0057] The decomposition process can be based on simulated spectra, and specifically, it can be performed using a fundamental decomposition method.

[0058] The α-ray spectra at positions x and y can be decomposed by comparing the coefficients of the simulated spectra (A) of the first and second nuclides obtained from the simulated spectra. x，y For the decomposition step, the formula in Equation 2 below can be used, but is not limited to this.

[0059] <Equation 2>

[0060]

[0061] When using 10kBq 225 Ac was used as the first nuclide and 10 kBq was used. 213 When Bi is used as a second nuclide, w* x，y It can be used as the alpha-ray spectrum (b) to be photographed x，y The result is obtained by inserting b into the above formula. That is, when b x，y When represented as A, w* x，y It can be a coefficient. For example, when A is [3, 1] and the captured b x，y When the value is 19, the formula can be applied to satisfy b. x，y Given the constraints of w1×3 + w2×1, find w*. x，y When the answer is w* x，y When = [5, 4], 225 Ac can be 50 kBq at specific positions in x and y, which is 5 × 10 kBq, and 213 Bi can be 40 kBq at positions x and V, which is 4 × 10 kBq.

[0062] In other words, the decomposition process may include the step of obtaining the coefficient ratio between the first α-ray spectrum and the second α-ray spectrum at a specific location for measurement.

[0063] Finally, in S500, the ratio between alpha-ray nuclides can be derived.

[0064] In this step, it can be determined whether the alpha rays at a specific location are emitted from the first or the second nuclide, and the ratio between the two nuclides can be derived. That is, the radiation source emitting the alpha rays can be determined.

[0065] The above w* x，y This can be obtained using two values, one of which can be the coefficient ratio of the first α-ray spectrum and the other of the coefficient ratio of the second α-ray spectrum. As a result, the abundance ratio of the first and second nuclides at specific positions x and y can be determined.

[0066] Because the process of determining the abundance ratio of the first and second nuclides can be performed over the entire two-dimensional (2D) region, an image of the radioactive distribution of each nuclide can be obtained. As a result, the first and second nuclides can be additionally displayed in different colors and fused together to obtain a fused image, which can be used to visualize the distribution of alpha rays of each nuclide.

[0067] In another embodiment, information about nuclides at various locations can be provided without separate imaging operations.

[0068] According to the present disclosure, even when using a device with relatively low energy resolution for measurement, the radiation source emitting alpha rays can be identified.

[0069] Using the method according to this disclosure, an image of the nuclide distribution of each nuclide in the imaging system can be obtained.

[0070] In addition, by using corresponding images of the distribution of nuclides in preclinical trials of TAT, the production mechanism of daughter nuclides can be tracked, toxicity caused by excessive daughter nuclides can be prevented, and the therapeutic effect can be maximized.

[0071] This disclosure will be described in detail through the following experimental examples.

[0072] In the experimental example below, the α-ray spectrum to be decomposed is obtained by simulation rather than actual measurement.

[0073] The nuclide in the experimental example is the parent nuclide. 225 Ac and daughter nuclides 213 Bi.

[0074] As the parent nuclide 225 The decay curve of Ac can be as follows.

[0075] The simulated spectrum of the parent nuclide can include... 225 Ac and 225 All daughter nuclides of Ac, such as 221 Fr and 213 The energy spectrum emitted by Bi, and the simulated spectrum of the daughter nuclide can include only the energy spectrum emitted by Bi. 213 Bihe 213 All daughter nuclides of Bi, such as 213 Po and209 The energy spectrum emitted by Tl.

[0076]

[0077] like Figure 2 As shown, for the parent nuclide 225 Ac and daughter nuclides 213 By combining the two methods, a simulated spectrum under 10 kBq radioactivity was obtained. Figure 2 Show “A” in Equation 2 above.

[0078] The simulated spectrum was obtained based on the radioactivity information of each nuclide over time obtained through the Bateman equation and Monte Carlo simulation. In the Monte Carlo simulation, the alpha-ray imaging device was applied to the Geant4 application (GATE) code for tomographic emission.

[0079] The replica and radiation source used to obtain the alpha-ray spectrum were respectively located in... Figure 3 and Figure 4 As shown in the image.

[0080] Construct a thin, kidney-shaped mold with dimensions of 300×300×8 mm, and a width × length of 29.43×18.11 mm. 2 The phantom thickness was 28 μm for all eight slices. The material of the phantom was as follows: Figure 4 As shown in the diagram. Regions 2 and 3 are made of kidney material with a density of 1.05, and regions 4 and 5 are made of blood vessels or blood with a density of 1.06. The phantom was simulated using GATE on an alpha-ray imaging device.

[0081] In the simulation, nuclides that emit alpha rays will be... 225 Ac and 213 Bi is injected into such Figure 4 In regions 1 to 5 shown. For 225 Ac and 213 Bi is injected into region 2, only 225 Ac is injected into regions 3 and 5, and only... 213 The simulation was performed in Bi injection region 4. Because it is in radial equilibrium... 225 Ac and 213 Bi is injected considering the Bateman equation, so even if only injected... 225 Ac also includes 213 Bi daughter nuclides. Even if only injected 213 Bi also includes 213 daughter nuclides of Bi.

[0082] Measurements were taken immediately after the simulated injection, and for a total of 150 seconds. Because... 225 Nuclides on the decay curve of Ac sometimes emit beta and gamma rays. To reduce their influence, only those with energies exceeding 500 keV are counted (i.e., the threshold is set to 500 keV) to obtain the energy spectrum of each pixel. When all the Y values ​​(count values) of a pixel's spectrum are summed and represented as a single value, the intensity of that pixel is represented.

[0083] An image is obtained by measuring the intensity of pixels in two dimensions. The image size is 300×300, and the area of ​​each pixel is 100μm. 2 Therefore, the total size of the image is 30×30mm. 2 Because the resulting image is as follows: Figure 5 The image shown is a black and white image, so we can only know the radioactivity of each pixel from this image, but we cannot know the information about the distribution of each nuclide.

[0084] The α-ray spectrum in region 2 obtained through the above process is as follows: Figure 6 As shown in the image. Figure 6 The figure shows “b” in equation 2. x，y ".

[0085] For each region, the first α-ray spectrum (red) for the parent nuclide and the second α-ray spectrum (blue) for the daughter nuclide, obtained by deriving coefficients from Equation 2, are shown in [the diagram]. Figures 7A to 7D middle.

[0086] Here, the parent nuclide refers to the parent nuclide and the daughter nuclide produced by the decay of the parent nuclide in the corresponding region. The daughter nuclide refers to the daughter nuclide introduced after it is produced in other regions.

[0087] Figure 8A and Figure 8B The examples shown in this disclosure are from... 225 Ac's alpha rays and from 213 Image of Bi's α-rays.

[0088] The images of the decomposition spectra of each region obtained by summing the decomposition results of each region are as follows: Figure 9 As shown in the image. Figure 9 The images in the image are in color.

[0089] get Figure 9 The method for obtaining the image is as follows. First, a complete two-dimensional image of the parent and daughter nuclides can be obtained (Figure 8).

[0090] 225An Ac image can be converted to an RGB image, and the R:G:B = 1:0:0 ratio can be applied. Pixels with high values ​​can be represented by dark red, while pixels with low values ​​can be represented by light red. Similarly, 213 An image of Bi can be converted to an RGB image, and the R:G:B = 0:1:0 ratio can be applied. Pixels with high values ​​can be represented by dark green, while pixels with low values ​​can be represented by light green. When these two images are combined, only pixels with high values ​​can be represented by red. 225 The region of Ac can be represented in green as where only Ac exists. 213 The region of Bi can be represented by a composite value of red and green (e.g., yellow). 225 Ac and 213 The area where Bi exists.

[0091] and Figure 5 different, Figure 9 This shows which radiation source produces the alpha rays in the region of interest.

[0092] Reference Figure 9 , 225 Ac and 213 Region 2, where Bi is present, is indicated in yellow, which is a mixture of red and green, and it can be qualitatively confirmed that the distribution of the injected radiation source can be well predicted.

[0093] The radioactivity of the actually injected nuclide is compared with the radioactivity of the nuclide expected according to this disclosure, according to Equation 3 below.

[0094] <Equation 3>

[0095]

[0096] Radioactivity of the expected nuclide in region r

[0097] I r The radioactivity of the nuclides actually injected into region r

[0098] As a result of the comparison, such as Figure 10 As shown, each region displays a relative error of less than 5%.

[0099] The above embodiments are examples used to describe this disclosure, and this disclosure is not limited thereto. Since those skilled in the art can make various modifications to this disclosure, the scope of this disclosure should be defined by the appended claims.

Claims

1. A method for analyzing alpha-ray spectra obtained from a radiation source, wherein, The radiation source comprises a first nuclide and a second nuclide that are different from each other, and the method includes: The simulated spectrum of α-rays emitted from the first and second nuclides was obtained by simulating the radioactivity functions based on the first and second nuclides. An alpha-ray spectrum is obtained by measuring the alpha rays emitted from the radiation source; and Based on the simulated spectrum, the α-ray spectrum is decomposed into a first α-ray spectrum of α-rays emitted from the first nuclide and a second α-ray spectrum of α-rays emitted from the second nuclide; Wherein, the second nuclide is a daughter nuclide of the first nuclide; The radioactivity function is obtained based on information about the half-life and emission probability of the first and second nuclides.

2. The method according to claim 1, wherein, The combination of the first nuclide and the second nuclide is [ 225 Ac, 213 Bi]、[ 211 At, 212 Po]、[ 212 Bi, 212 Po]、[ 213 Bi, 213 Po]、[ 212 Pb, 212 Po]、[ 223 Ra, 212 Bi] and [ 227 Th, 211 Any combination of [Bi].

3. The method according to claim 1, wherein, The radiation source includes a first radiation source and a second radiation source, and the first radiation source and the second radiation source have different distributions of the first nuclide and the second nuclide.

4. The method according to claim 3, wherein, In the measurement, the first radiation source and the second radiation source are spaced apart from each other.

5. The method of claim 4, further comprising, after the decomposition, deriving the ratio of alpha rays from the first radiation source to alpha rays from the second radiation source at a specific measurement location.

6. The method according to claim 1, wherein, The measurements were performed on replicas of human body parts.

7. The method according to claim 1, wherein, The decomposition of the measured spectrum includes the step of obtaining the coefficient ratio between the first α-ray spectrum and the second α-ray spectrum at a specific measurement location.

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