Tissue Equivalent Conversion Method for Microdose Detectors Based on Fourier Scaling Transform Characteristics

Abstract

The present invention discloses a microdose detector tissue equivalent conversion method based on Fourier scale transformation characteristics, which belongs to the field of radiation dose measurement technology. The method comprises the following steps: obtaining the deposition energy distribution D(x) of incident radiation in the microdose detector under given conditions, and calculating the average deposition energy ratio of the incident radiation in the microdose detector and the biological tissue; performing scale transformation on D(x), and performing Fourier transformation on D(x) and H(x) obtained after the scale transformation, to obtain the modulus M of D(x) and H(x) in Fourier space respectively. D 、M H ; According to the average deposition energy comparison model M D 、M H The difference is corrected, and the corrected difference is then inverse Fourier transformed and normalized. Finally, the normalized result is convolved with H(x) to obtain the deposition energy spectrum T(x) in the biological tissue. The present invention can accurately and reliably convert the deposition energy spectrum measured by the microdose detector into the deposition energy spectrum in biological tissue, effectively improving the deviation problem of current tissue equivalent conversion methods when converting in the low-energy region, and achieving the measurement goal.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation dose measurement and radiation protection, and in particular to a microdose detector tissue equivalent conversion method based on Fourier scale transformation characteristics. Background Art

[0002] Solid-state microdose detectors have attracted widespread attention in recent years because they can directly scale the detector's sensitive volume to the size of biological tissue, accurately characterizing the interactions of incident radiation within this microscopic volume. However, due to differences between the detector materials (primarily silicon and diamond) and biological tissue materials, such as physical properties, density, and ionization energy, the energy distribution of radioactive particles or radiation deposited in a microdose detector differs from that in biological tissue. Therefore, to obtain the energy distribution of deposition within the microscopic volume of biological tissue, it is necessary to perform tissue-equivalent conversion on the microdose detector's measurements.

[0003] Currently, researchers have proposed a conversion method based on spectral distribution transformation to convert the deposition energy spectrum measured by microdose detectors to that of biological tissues of equivalent size. However, because the characteristics of low-energy deposition events are not taken into account during the conversion process, the conversion results in the low-energy region are not ideal. This means that the deposition energy spectrum measured by the microdose detector cannot be effectively converted to the deposition energy spectrum in biological tissues, and significant errors are particularly evident when converting in the low-energy region. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of the prior art and provide a microdose detector tissue equivalent conversion method based on Fourier scale transform characteristics.

[0005] The object of the present invention is achieved through the following technical solution: a microdose detector tissue equivalent conversion method based on Fourier scale transform characteristics, the method comprising the following steps:

[0006] Obtain the deposition energy distribution D(x) of the incident radiation in the microdose detector under given conditions (a certain energy ray particle irradiation field);

[0007] Calculate the average deposition energy ratio λ of the incident radiation in the microdose detector and biological tissue under current conditions;

[0008] The measured deposition energy distribution D(x) is scaled according to the average deposition energy ratio λ to obtain the scaled deposition energy distribution H(x);

[0009] Perform Fourier transform on D(x) and H(x) to obtain the modulus M of D(x) and H(x) in Fourier space respectively. D 、M H ;

[0010] Calculation modulus M D and M H The difference between them is corrected according to the average deposition energy ratio to obtain M E ;

[0011] The corrected difference M E Perform inverse Fourier transform to obtain the deposition energy distribution difference E(x), and then normalize E(x) to obtain C(x);

[0012] The normalized result C(x) is convolved with the scale-transformed deposition energy distribution H(x) to obtain the deposition energy spectrum T(x) in biological tissue of the same size as the microdose detector under the same conditions.

[0013] In one example, the calculation formula for the average deposition energy ratio λ is:

[0014]

[0015] Where ε represents the energy deposited by the incident radiation in the medium; ε(E in , microdose detector) indicates that the incident energy is E in When the deposition energy in the microdose detector is in , tissue) indicates that the incident energy is E in The deposited energy in biological tissues.

[0016] In one example, the average particle deposition energy ε is calculated as:

[0017]

[0018] ΔE=E i -E i+1

[0019] ε=E0-E n

[0020] Where L is the distance that the incident radiation travels in the medium (microdose detector or biological tissue); ΔE is the energy interval; E0 is the energy of the incident radiation before entering the medium; E n represents the energy of the incident radiation when it leaves the medium; i represents the i-th energy interval point; S(E i ) represents the energy size E i The linear stopping power of the medium for incident particles when .

[0021] In one example, the calculation formula for scaling the measured deposition energy distribution D(x) is:

[0022] H(x)=λD(λx)

[0023] Where x represents the particle deposition energy.

[0024] In one example, the calculation modulo M D and M H The difference between the two and the difference is corrected according to the average deposition energy ratio:

[0025]

[0026] In one example, the calculation formula for the deposition energy spectrum T(x) is:

[0027] T(x)=C(x)*H(x)

[0028] Where x represents the particle deposition energy.

[0029] In one example, the Fourier transform, the calculation formula for the modulus in Fourier space is:

[0030]

[0031]

[0032] Where 1≤k≤N represents the data point corresponding to the particle deposition energy data point x in Fourier space, N represents the data length, and x represents the particle deposition energy.

[0033] In one example, the inverse Fourier transform calculation formula is:

[0034]

[0035] Where 1≤k≤N represents the data point corresponding to the particle deposition energy data point x in Fourier space, N represents the data dimension, and x represents the particle deposition energy.

[0036] In one example, negative values ​​in the deposition energy distribution difference E(x) are eliminated.

[0037] In one example, the calculation formula for normalization after removing negative values ​​of E(x) is:

[0038]

[0039] Where E1(x) represents the distribution after removing the negative values ​​in the E(x) distribution; C(x) represents the normalized distribution, and x represents the particle deposition energy.

[0040] It should be further explained that the technical features corresponding to the various examples of the above methods can be combined or replaced with each other to form a new technical solution.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The method of the present invention can be widely applied to the tissue equivalent correction of solid microdose detectors, making the detector suitable for measurement within the full range of particles. Combined with simulation results, it can be seen that the method of the present invention can accurately and reliably convert the deposition energy spectrum measured by the microdose detector into the deposition energy spectrum in biological tissue, effectively improving the problem of deviation in the current tissue equivalent conversion method when converting in the low-energy region, and achieving the measurement goal. The whole process is simple to operate and reduces the measurement cost to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application.

[0044] Figure 1 This is the percentage depth dose curve of 50MeV protons in the bone membrane;

[0045] Figure 2 This is a flow chart of a microdose detector tissue equivalent conversion method based on Fourier scale transform characteristics disclosed in the present invention;

[0046] Figure 3 The figure is a comparison between the equivalent conversion result of the diamond microdose detector in the plateau area of ​​the percentage depth dose curve and the deposition energy spectrum in the bone;

[0047] Figure 4 This is a comparison diagram of the equivalent conversion result of the diamond microdose detector at the front end of the Bragg peak of the percentage depth dose curve and the deposition energy spectrum in the bone;

[0048] Figure 5 This is a comparison diagram of the equivalent conversion result of the diamond microdose detector at the rear end of the Bragg peak of the percentage depth dose curve and the deposition energy spectrum in the bone. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is described clearly and completely below with reference to the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the directions or positional relationships described in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the use of ordinal numbers (for example, "first and second", "first to fourth", etc.) is for the purpose of distinguishing objects and is not limited to this order, and cannot be understood as indicating or implying relative importance.

[0051] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention.

[0052] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0053] In this embodiment, 10×10×10 μm 3 Taking the energy spectrum measured by large and small diamond microdose detectors in a 50MeV proton irradiation field as an example, the energy deposition distribution measured by the diamond microdose detector in the plateau area, the front end of the Bragg peak, and the back end of the Bragg peak of the bone percentage depth dose curve as an example, the tissue equivalent conversion is performed on the energy deposition distribution measured by the diamond microdose detector in the plateau area, the front end of the Bragg peak, and the back end of the Bragg peak of the bone percentage depth dose curve. Figure 1 As shown, it represents the percentage of the absorbed dose of radiation particles (50MeV protons) at a certain depth in the bone to the absorbed dose at a reference depth. It is a physical quantity that describes the relative dose distribution at different depths of the central axis of the radiation.

[0054] At this time, if Figure 2 As shown, the present invention provides a microdose detector tissue equivalent conversion method based on Fourier scaling characteristics, comprising the following steps:

[0055] S1: Obtain the deposition energy distribution D1(x), D2(x), and D3(x) of the diamond microdose detector at the plateau area, the front end of the Bragg peak, and the back end of the Bragg peak of the percentage depth dose curve;

[0056] In this embodiment, the specific depth parameters of the three measurement points selected, namely, the Bragg curve plateau, the front end of the Bragg peak, and the back end of the Bragg peak, in the body membrane are shown in Table 1:

[0057] Table 1 Depth of selected measurement points in the bone membrane

[0058]

[0059] S2: Calculate the average deposition energy ratio between the diamond microdose detector and the bone at the incident energy at measurement point 1, measurement point 2, and measurement point 3, λ1, λ2, and λ3;

[0060] S3: Scale the deposition energy distributions D1(x), D2(x), and D3(x) measured at measurement points 1, 2, and 3 according to the calculated average deposition energy ratio to obtain H1(x), H2(x), and H3(x);

[0061] S4: Perform Fourier transform on the distributions D1(x), D2(x), D3(x) and H1(x), H2(x), H3(x) and obtain the modulus M of the transformed results in Fourier space D1 、M D2 、M D3 and M H1 、M H2 、M H3 ;

[0062] S5: Calculation module M D1 and M H1 、M D2 and M H2 、M D3 and M H3 The difference between them is corrected according to the average deposition energy ratio to obtain M E1 、M E2 、M E3 ;

[0063] S6: M E1 、M E2 、M E3 Perform inverse Fourier transform to obtain E1(x), E2(x), and E3(x), and normalize E1(x), E2(x), and E3(x) to obtain C1(x), C2(x), and C3(x);

[0064] S7: Convolve the normalized results C1(x), C2(x), and C3(x) with the scale-transformed deposition energy distributions H1(x), H2(x), and H3(x) to obtain the deposition energy distributions T1(x), T2(x), and T3(x) in the bones at measurement points 1, 2, and 3, respectively.

[0065] In order to verify the tissue equivalent conversion effect of the method of the present invention, the deposition energy distribution B1(x), B2(x), and B3(x) of protons in bones of the same size at each measurement point were obtained through software simulation. The deposition energy distribution T1(x), T2(x), and T3(x) obtained by the method proposed in the present invention were compared with B1(x), B2(x), and B3(x). The results are as follows: Figure 3-5 As shown, Figure 3-5 The horizontal axis ε represents the energy deposited in the bone, and the vertical axis F(ε) represents the probability distribution of the deposited energy. Figure 3 Comparison between the equivalent conversion result of the diamond microdose detector at measurement point 1 and the energy distribution in the bone; Figure 4 Comparison between the equivalent conversion of the diamond microdose detector at measurement point 2 and the energy distribution deposited in the bone; Figure 5 This is a comparison between the equivalent conversion result of the diamond microdose detector at measurement point 3 and the energy distribution in the bone. Figure 3-5 It can be seen that the deposition energy distribution obtained after tissue equivalent conversion of the microdose detector by the method of the present invention is consistent with the deposition energy distribution in the bone under the same conditions, especially in the low-energy areas at measurement points 1 and 2, where the overlap between the conversion result and the actual result is high, that is, the method of the present invention can accurately convert the deposition energy distribution measured by the detector into the deposition energy distribution in the biological tissue under the same conditions, and compared with the existing conversion method, this method can effectively eliminate the conversion deviation in the low-energy area and improve the consistency between the conversion result and the actual result.

[0066] The above specific implementation methods are detailed descriptions of the present invention. It cannot be considered that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions and substitutions without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics, characterized by: It includes the following steps: Obtain the deposition energy distribution D(x) of the incident radiation in the microdose detector under given conditions; Calculate the average deposition energy ratio λ of the incident radiation in the microdose detector and biological tissue under current conditions; The measured deposition energy distribution D(x) is scaled according to the average deposition energy ratio λ to obtain the scaled deposition energy distribution H(x); Perform Fourier transform on D(x) and H(x) to obtain the modulus M of D(x) and H(x) in Fourier space respectively. D 、M H ; Calculation modulus M D and M H The difference between them is corrected according to the average deposition energy ratio to obtain M E ; The corrected difference M E Perform inverse Fourier transform to obtain the deposition energy distribution difference E(x), and then normalize E(x) to obtain C(x); The normalized result C(x) is convolved with the scale-transformed deposition energy distribution H(x) to obtain the deposition energy spectrum T(x) in biological tissue of the same size as the microdose detector under the same conditions.

2. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The calculation formula of the average deposition energy ratio λ is: Where ε represents the average energy deposited by the incident radiation in the medium; ε(E in , microdose detector) indicates that the incident energy is E in When the deposition energy in the microdose detector is in , biological tissue) indicates that the incident energy is E in The deposited energy in biological tissues.

3. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The calculation formula of the average particle deposition energy ε is: ΔE=E i -E i+1 ε=E0–E n Where L is the distance that the incident radiation travels in the medium; ΔE is the energy interval; E0 is the energy of the incident radiation before it enters the medium; E n represents the energy of the incident radiation when it leaves the medium; i represents the i-th energy interval point; S(E i ) represents the energy size E i The linear stopping power of the medium for incident particles when .

4. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The calculation formula for scaling the measured deposition energy distribution D(x) is: H(x)=λD(λx) Where x represents the particle deposition energy.

5. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: Calculation modulus M D and M H The difference between the two and the difference is corrected according to the average deposition energy ratio:

6. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The calculation formula of deposition energy spectrum T(x) is: T(x)=C(x)*H(x) Where x represents the particle deposition energy.

7. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The calculation formula for the modulus in Fourier transform and Fourier space is: Where 1≤k≤N represents the data point corresponding to the particle deposition energy data point x in Fourier space, N represents the data length, and x represents the particle deposition energy.

8. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The inverse Fourier transform calculation formula is: Where 1≤k≤N represents the data point corresponding to the particle deposition energy data point x in Fourier space, N represents the data dimension, and x represents the particle deposition energy.

9. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 1, characterized in that: The negative values ​​in the deposition energy distribution difference E(x) are eliminated.

10. The method for converting microdose detector tissue equivalents based on Fourier scale transform characteristics according to claim 9, characterized in that: The calculation formula for normalization after removing the negative values ​​of E(x) is: Where E1(x) represents the distribution obtained by removing negative values ​​from the E(x) distribution; C(x) represents the normalized distribution, and x represents the particle deposition energy.

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