Method for calibrating ocular lens evaluation values of beta standard field orientation dose equivalent rate

Abstract

The present application relates to the eye lens evaluation value calibration method of beta standard field orientation dose equivalent rate, including the following steps: measuring the absorption dose rate and its uniformity distribution in the beta radiation field; measuring the energy spectrum of Sr / Y-90 beta radiation field; establishing the conversion coefficient database of corresponding absorption dose rate-orientation dose equivalent rate when the energy spectrum regional distribution of Sr / Y-90 beta radiation field changes, obtaining the regional distribution measurement result of orientation dose equivalent rate in the beta radiation field; determining the orientation dose equivalent rate uniformity region of Sr / Y-90 beta radiation field. The method provided by the present application can solve the problem that when measuring the uniform region of the orientation dose equivalent rate H'(3) reflecting the eye lens of the personnel in the beta radiation field of the BSS 2 standard device, due to the deformation and aging of the flattening filter after long-term use and other factors, the uniform region of the orientation dose equivalent rate in the beta radiation field changes, resulting in a certain difference between the orientation dose equivalent rate at the measurement point and the PC end indicated value.

Description

Technical Field

[0001] This invention belongs to the field of metrology and testing technology, specifically relating to a calibration method for the ocular lens evaluation value of β standard field directional dose equivalent rate. Background Technology

[0002] Absorbed radiation dose is a physical quantity used to represent the amount of ionizing radiation energy absorbed per unit mass of irradiated material when ionizing radiation interacts with matter. The absorbed radiation dose is the quotient obtained by dividing the average energy imparted by ionizing radiation deposited in an infinitesimally small volume element by the mass of the material in that volume element.

[0003] Beta absorbed dose is an indispensable part of ionizing radiation metrology. In my country, beta absorbed dose reference radiation is mostly provided by the Beta Secondary Standard Type 2 (BSS2) standard device, which is based on beta radioisotopes. 90 Sr- 90 Y、 85 Kr、 147 The emitted beta rays, after being bundled by the flattened filter, can provide a radiation field with a uniform dose rate within a range of tens of centimeters in diameter at the measurement point, and provide a corresponding reference value at the PC end.

[0004] In workplace or environmental monitoring, dose equivalent values ​​are measured under "receptor-free" conditions. This means the location of interest is a potential human dwelling location, but no person or model is actually present there; various other objects far from the receptor, along with their absorption and scattering, are present. The directional dose equivalent rate of beta radiation... This refers to the dose equivalent produced per unit time at a point in the radiation field, within a radius of Ω and a depth of 3 mm in a specified direction within the IRCU sphere, in the corresponding extended field. The unit is Sv / h. Typically, It is used to reflect the radiation dose level of the lens of a person's eye in the presence of environmental beta radiation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a calibration method for evaluating the directional dose equivalent rate of the eye lens in the β standard field. This method addresses the issue that factors such as deformation and aging of the flattened filter after long-term use cause changes in the uniform region of the directional dose equivalent rate in the β radiation field, leading to variations in the directional dose equivalent rate of the eye lens at the measurement point. The problem is that there is a certain difference between the values ​​displayed on the PC and the values ​​displayed on the PC.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate, the method comprising the following steps:

[0007] S1. Measure the absorbed dose rate in the β radiation field. and its uniform distribution;

[0008] S2. Measure the energy spectrum of the Sr / Y-90β radiation field;

[0009] S3. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes, and obtain the directional dose equivalent rate in the β radiation field. Regional distribution measurement results;

[0010] S4. Determine the directional dose equivalent rate of the Sr / Y-90β radiation field. Uniform region.

[0011] Furthermore, step S1 includes the following specific steps:

[0012] S11. Place the sensitive volume center of the ionization chamber at the measurement point at the center of the normal of the Sr / Y-90β radiation field to ensure that the β rays are incident perpendicularly into the ionization chamber.

[0013] S12. Based on the accumulated charge J fed back by the electrometer connected to the ionization chamber. a The absorbed dose rate at the measurement point is calculated by taking the reading and combining it with formulas (1) to (3).

[0014]

[0015]

[0016]

[0017] in:

[0018] J a : Cumulative charge, C;

[0019] The average ionization energy of air, eV;

[0020] The ratio of the average mass blocking power of the entrance window of the ionization chamber to that of the air is a constant without dimensions.

[0021] Sensitive volume air mass, m 3 / kg;

[0022] k PT Temperature and pressure correction factor, where P is the ambient air pressure (kPa) and T is the ambient temperature (°C).

[0023] t: Measurement time, in seconds;

[0024] D: Absorbed dose, J / kg;

[0025] Absorbed dose rate, J / (kg·h);

[0026] S13. Using the measurement point as the center, on the vertical plane where the sensitive volume center of the ionization chamber is located, move the sensitive volume center of the ionization chamber 20.0 cm in each of the four directions: up, down, left, and right. Set the movement step size to 1.0 cm to 2.0 cm, and obtain the cumulative charge J at each moving point. a The absorbed dose rate at each moving point was calculated. Thus, the absorbed dose rate in the β radiation field is obtained. The uniform distribution.

[0027] Furthermore, the ionization chamber is a thin-window ionization chamber.

[0028] Furthermore, the energy spectrum of the Sr / Y-90β radiation field was measured using a SiPIN detector; the SiPIN detector is connected to a matching preamplifier, main amplifier, and digital multichannel.

[0029] Furthermore, when performing energy spectrum measurements of the Sr / Y-90β radiation field using the SiPIN detector, a 3 mg·cm⁻¹ area is placed in front of the SiPIN detector window. 2 Aluminized polyester film.

[0030] Furthermore, when using the SiPIN detector to perform energy spectrum measurements of the Sr / Y-90β radiation field, the absorbed dose rate in step S1 is compared with that in step S1. The method for measuring the uniformity distribution is the same as that for the SiPIN detector, which is placed at the same position as the sensitive volume center of the ionization chamber. After each set of cumulative charge readings is measured in the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum distribution of the Sr / Y-90β radiation field at the current position.

[0031] Furthermore, step S3 includes the following specific steps:

[0032] S31. Using MCNP simulation to establish an ICRU tissue sphere model, a method for calculating the conversion coefficient of absorbed dose rate to directional dose equivalent rate is obtained.

[0033] S32. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes.

[0034] S33. Combining the measurement points obtained in step S1 with the absorbed dose rate at each moving point. Targeted dose equivalent rate in Sr / Y-90β radiation field was obtained The regional distribution of.

[0035] Furthermore, step S32 includes the following specific steps:

[0036] S321. Based on the results of measuring the energy spectrum region distribution of the Sr / Y-90β radionuclide using the SiPIN detector and the matching BSS2 standard device, the conversion coefficient H′(3,T) / D corresponding to the change in the energy spectrum region distribution of the β radiation field of the Sr / Y-90β radionuclide is calculated according to formula (5). T ;

[0037]

[0038] Wherein, H′(3,T) is the small volume element directional dose equivalent at a surface depth of 3 mm in the ICRU tissue sphere model under Sr / Y-90β radionuclide irradiation, and Sv;

[0039] Φ E The energy E of the Sr / Y-90β radionuclide, m -3 ;

[0040] Q is the β-particle quality factor, taken as Q = 1Sv / Gy;

[0041] Energy deposition per unit mass within a small volume element, J / kg;

[0042] D T,E For the injection volume Φ E The deposition energy of Sr / Y-90β radionuclides with energy E in a small volume element, J / kg;

[0043] D T The deposition energy of the Sr / Y-90β radionuclide in a small volume element, J / kg;

[0044] S322. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes.

[0045] Furthermore, step S33 includes the following specific steps: calculating the absorbed dose rate at each measurement point and moving point obtained in step S1. The measurement result is multiplied by the corresponding absorption dose rate-directional dose equivalent rate conversion factor H′(3,T) / D from the absorption dose rate-directional dose equivalent rate conversion factor database. T The directional dose equivalent rate at the measurement point and at each moving point was calculated. Thus, the directional dose equivalent rate in the β radiation field is obtained. The regional distribution of.

[0046] Furthermore, in step S4, the area where the deviation of the directional dose equivalent rate from the measurement point does not exceed ±5% is selected and identified as the directional dose equivalent rate of the β radiation field. Uniform region.

[0047] The beneficial effects of this invention are as follows: The eye lens assessment calibration method for β-standard field directional dose equivalent rate provided by this invention can be used to measure the absorbed dose rate in the β-radiation field. Its uniform distribution; measuring the energy spectrum of the Sr / Y-90β radiation field; establishing a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes, and obtaining the directional dose equivalent rate in the β radiation field. The regional distribution measurement results were used to determine the directional dose equivalent rate of the Sr / Y-90β radiation field. Uniform region. The method provided by this invention enables the measurement of the directional dose equivalent rate of the human eye lens in the β-radiation field of a BSS2 standard device. When considering a uniform region, this addresses the issue of changes in the uniformity of the directional dose equivalent rate in the β-radiation field caused by factors such as deformation and aging of the flattened filter after long-term use, which leads to variations in the directional dose equivalent rate at the measurement point. The problem is that there is a certain difference between the values ​​displayed on the PC and the values ​​displayed on the PC. Attached Figure Description

[0048] Figure 1 A schematic flowchart illustrating the method for calibrating the ocular lens assessment value of β standard field directional dose equivalent rate provided in an embodiment of the present invention;

[0049] Figure 2 Absorbed dose rate provided for embodiments of the present invention Measurement diagram;

[0050] Figure 3 A schematic diagram of a unit mass ICRU tissue sphere model established using MCNP, provided for an embodiment of the present invention. Detailed Implementation

[0051] The technical solutions in the embodiments of the present invention will be further clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0052] It should be noted that in the description of the embodiments of the present invention, the terms "upper," "lower," "front," "rear," "front," "back," "left," "right," "horizontal," "vertical," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They 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, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] The inventors discovered that flattened filters are prone to deformation and aging after long-term use, causing changes in the uniformity of the beta radiation dose rate at the reference point. However, the reference value at the PC only corrects for the decay of the radiation source itself and environmental factors at the measurement point, which also leads to a difference between the actual value at the measurement point and the reference value at the PC. This change is mainly reflected in two aspects: absorbed dose rate and dose equivalent rate. The uniformity change of absorbed dose rate can be directly measured using a thin-window ionization chamber, but the measurement of dose equivalent rate depends on the energy of beta rays and cannot directly measure the uniformity change.

[0054] Due to the directional dose equivalent rate It is used to reflect the radiation dose level at a depth of 3 mm equivalent thickness in human tissue. In the β standard radiation field of the BSS2 standard device, only the energy of Sr / Y-90 is relevant to the directional dose equivalent rate. It makes a contribution, but other nuclides do not have enough energy and therefore do not make a contribution.

[0055] like Figure 1-3 As shown, this embodiment provides a method for calibrating the ocular lens assessment value of the directional dose equivalent rate in a β standard field, namely, in a Sr / Y-90β radiation field, calibrating the directional dose equivalent rate... A method for measuring a uniform region, the method comprising the following steps:

[0056] S1. Measure the absorbed dose rate in the β radiation field. and its uniform distribution;

[0057] like Figure 2 In the experiment shown, the sensitive volume center of the ionization chamber was placed at the measurement point at the center of the normal to the Sr / Y-90β radiation field, ensuring that the β rays were incident perpendicularly into the ionization chamber; then, the accumulated charge J was fed back from the electrometer connected to the ionization chamber. a The absorbed dose rate at the measurement point can be calculated by referring to formulas (1) to (3).

[0058]

[0059]

[0060]

[0061] in:

[0062] J a : Cumulative charge, C;

[0063] The average ionization energy of air, eV;

[0064] The ratio of the average mass blocking power of the entrance window of the ionization chamber to that of the air is a constant without dimensions.

[0065] Sensitive volume air mass, m 3 / kg;

[0066] k PT Temperature and pressure correction factor, where P is the ambient air pressure (kPa) and T is the ambient temperature (°C).

[0067] t: Measurement time, in seconds;

[0068] D: Absorbed dose, J / kg;

[0069] Absorbed dose rate, J / (kg·h);

[0070] The ionization chamber is a thin-window ionization chamber, and the PTW34045 type thin-window ionization chamber can be selected.

[0071] Specifically, the accumulated charge J reported by the electrometer connected to the ionization chamber. a The reading is obtained by recording the electrometer reading (i.e., current I) at the measurement point, and combining this reading with the residence time of the sensitive volume center of the ionization chamber at the measurement point to obtain the cumulative charge J at the measurement point. a .

[0072] Similarly, taking the measurement point as the center, on the vertical plane where the sensitive volume center of the ionization chamber is located, move the sensitive volume center of the ionization chamber 20.0 cm in each of the four directions: up, down, left, and right. The step size can be set to 1.0 cm to 2.0 cm. Record the electrometer reading at each moving point, and combine it with the dwell time at each moving point to obtain the cumulative charge J at each moving point. a Then, the absorbed dose rate at each moving point is calculated according to formulas (1) to (3). Therefore, the absorbed dose rate in the β radiation field can be obtained. The uniformity of the distribution.

[0073] S2. Measure the energy spectrum of the Sr / Y-90β radiation field;

[0074] Based on absorbed dose rate To determine the uniformity of the distribution, in order to further obtain the directional dose equivalent rate... In addition to obtaining a uniform region, it is also necessary to measure and provide the energy spectrum of the Sr / Y-90β radiation field (i.e., the energy spectrum region distribution of the Sr / Y-90β radiation field, or the energy spectrum region distribution of the β radiation field of the Sr / Y-90β radionuclides).

[0075] The energy spectrum of the Sr / Y-90β radiation field was measured using a SiPIN detector. In one specific embodiment, the SiPIN detector can be a BA-016-025-1500 type.

[0076] Specifically, when using a SiPIN detector to measure the energy spectrum of the Sr / Y-90β radiation field, the SiPIN detector is connected to a matching 142A preamplifier, a 575A main amplifier, and an MCA digital multichannel amplifier. The PC connected to the MCA digital multichannel amplifier can directly acquire the energy spectrum of the Sr / Y-90β radiation field through the matching software.

[0077] Specifically, when using a SiPIN detector to measure the energy spectrum of the Sr / Y-90β radiation field, a 3 mg·cm³ layer is placed in the front window of the SiPIN detector. 2 The aluminized polyester film is used to shield the light; when measuring the energy spectrum of the Sr / Y-90β radiation field using a SiPIN detector, the absorbed dose rate in step S1 is compared with that in step S1. The method for measuring the uniformity distribution is the same as that for the SiPIN detector, which is placed at the same position as the sensitive volume center of the ionization chamber. After each set of cumulative charge readings is measured in the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum distribution of the Sr / Y-90β radiation field at the current position.

[0078] In one specific embodiment, the energy spectrum distribution of the Sr / Y-90β radionuclide associated with the BSS2 standard device was measured using a SiPIN detector.

[0079] S3. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes, and obtain the directional dose equivalent rate in the β radiation field. Regional distribution measurement results;

[0080] Based on the above steps S1 and S2, the absorbed dose rate can be obtained. While the overall distribution of the spectral density in the Sr / Y-90β radiation field is known, the conversion from absorbed dose rate to directional dose equivalent rate requires appropriate conversion factors. Although ISO 6980-3 provides conversion factors for Sr / Y-90β nuclides at specified distances with and without flattening filters, these factors become inapplicable when the β-spectrum changes due to filter aging. Therefore, to obtain the distribution of directional dose equivalent rate in the Sr / Y-90β radiation field, a database of absorption dose rate-directional dose equivalent rate conversion factors is needed to account for changes in the spectral density distribution of the Sr / Y-90β radiation field.

[0081] Specifically, step S3 includes the following steps:

[0082] S31. Using MCNP simulation to establish an ICRU tissue sphere model, a method for calculating the conversion coefficient of absorbed dose rate to directional dose equivalent rate is obtained.

[0083] like Figure 3 As shown, an ICRU tissue sphere model with a unit mass (1 kg) is established using MCNP, which is the equivalent sphere used to simulate human tissue. A monoenergetic β particle with a fluence Φ and energy E is incident on the tissue sphere model from a specified orientation d at an incident angle θ (θ corresponds to the angle between the line d connecting the detector center to the radiation source and the horizontal normal during the movement of the SiPIN detector when measuring the energy spectrum. If the orientation d is horizontal with the β ray, θ = 0). According to the definition of directional dose equivalent, a small volume element with a surface depth of 3 mm is taken along the direction of orientation d. The energy deposition dε and mass dm within the small volume element are simulated and obtained. Combined with the β particle quality factor Q (for weakly penetrating β particles irradiated externally, Q = 1Sv / Gy is usually taken), the directional dose equivalent H0′(3,T) is calculated according to formula (4).

[0084]

[0085] Wherein, H0′(3,T) is the directional dose equivalent of a small volume element at a surface depth of 3 mm in the ICRU tissue sphere model under the condition of monoenergetic β particles with given fluence Φ and energy E, and Sv;

[0086] Q is the β-particle quality factor, taken as Q = 1Sv / Gy;

[0087] Energy deposition per unit mass within a small volume element, J / kg;

[0088] Subsequently, other structures in the tissue sphere model were removed, leaving only a small volume element at 3 mm. The deposition energy of monoenergetic β particles with fluence Φ and energy E within this small volume element was obtained, i.e., the absorbed dose D. T0Therefore, under the condition of monoenergetic β particles with a given flux Φ and energy E, the conversion coefficient H0′(3,T) / D of the absorbed dose-directed dose equivalent of a small volume element at a surface depth of 3 mm in the ICRU tissue sphere model is obtained. T0 This is the conversion coefficient between absorbed dose rate and directional dose equivalent rate.

[0089] S32. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes.

[0090] Combining the energy spectrum distribution of the Sr / Y-90β radionuclide obtained by measuring with a SiPIN detector in step S2, the conversion coefficient H′(3,T) / D corresponding to the change in the energy spectrum distribution of the β radiation field of the Sr / Y-90β radionuclide is calculated according to formula (5). T This allows us to obtain the conversion coefficient H′(3,T) / D of the absorbed dose rate minus the directional dose equivalent rate of a small volume element at a surface depth of 3 mm in the ICRU tissue sphere model when the distribution of the β-radiation field energy spectrum of the Sr / Y-90β radionuclide changes (due to factors such as deformation and aging of the flattened filter). T .

[0091]

[0092] Wherein, H′(3,T) is the small volume element directional dose equivalent at a surface depth of 3 mm in the ICRU tissue sphere model under Sr / Y-90β radionuclide irradiation, and Sv;

[0093] Φ E The energy E of the Sr / Y-90β radionuclide, m -3 ;

[0094] Q is the β-particle quality factor, taken as Q = 1Sv / Gy;

[0095] Energy deposition per unit mass within a small volume element, J / kg;

[0096] D T,E For the injection volume Φ E The deposition energy of Sr / Y-90β radionuclides with energy E in a small volume element, J / kg;

[0097] D T The deposition energy of the Sr / Y-90β radionuclide in a small volume element is expressed in J / kg.

[0098] Furthermore, based on the aforementioned variation in the β-radiation field energy spectrum region of the Sr / Y-90β radionuclide, the conversion coefficient H′(3,T) / D of the absorbed dose rate minus the directional dose equivalent rate of the small volume element at a surface depth of 3 mm in the ICRU tissue sphere model is calculated. T It is possible to establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes.

[0099] S33. Combining the measurement points obtained in step S1 with the absorbed dose rate at each moving point. Targeted dose equivalent rate in Sr / Y-90β radiation field was obtained Regional distribution measurement results;

[0100] According to formula (6), the absorbed dose rate at each measurement point and each moving point obtained in step S1 is calculated. The measurement result is multiplied by the corresponding absorption dose rate-directional dose equivalent rate conversion factor H′(3,T) / D from the absorption dose rate-directional dose equivalent rate conversion factor database. T The directional dose equivalent rate at the measurement point and each moving point can be directly calculated. Measurement results.

[0101]

[0102] Therefore, the directional dose equivalent rate in the β radiation field can be obtained. The regional distribution measurement results.

[0103] S4. Determine the directional dose equivalent rate of the Sr / Y-90β radiation field. Uniform region;

[0104] The area whose directional dose equivalent rate deviation from the measurement point (center location) does not exceed ±5% can be considered as the directional dose equivalent rate of the β radiation field. Uniform region.

[0105] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate, characterized in that, The method includes the following steps: S1. Measure the absorbed dose rate in the β radiation field. and its uniform distribution; S2. Measure the energy spectrum of the Sr / Y-90β radiation field; S3. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes, and obtain the directional dose equivalent rate in the β radiation field. Regional distribution measurement results; S4. Determine the directional dose equivalent rate of the Sr / Y-90β radiation field. Uniform region.

2. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 1, characterized in that, Step S1 includes the following specific steps: S11. Place the sensitive volume center of the ionization chamber at the measurement point at the center of the normal of the Sr / Y-90β radiation field to ensure that the β rays are incident perpendicularly into the ionization chamber. S12. Based on the accumulated charge J fed back by the electrometer connected to the ionization chamber. a The absorbed dose rate at the measurement point is calculated by taking the reading and combining it with formulas (1) to (3). in: J a : Cumulative charge, C; The average ionization energy of air, eV; The ratio of the average mass blocking power of the entrance window of the ionization chamber to that of the air is a constant without dimensions. Sensitive volume air mass, m 3 / kg; k PT Temperature and pressure correction factor, where P is the ambient air pressure (kPa) and T is the ambient temperature (°C). t: Measurement time, in seconds; D: Absorbed dose, J / kg; Absorbed dose rate, J / (kg·h); S13. Using the measurement point as the center, on the vertical plane where the sensitive volume center of the ionization chamber is located, move the sensitive volume center of the ionization chamber 20.0 cm in each of the four directions: up, down, left, and right. Set the movement step size to 1.0 cm to 2.0 cm, and obtain the cumulative charge J at each moving point. a The absorbed dose rate at each moving point was calculated. Thus, the absorbed dose rate in the β radiation field is obtained. The uniform distribution.

3. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 2, characterized in that, The ionization chamber is a thin-window ionization chamber.

4. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 2, characterized in that, The energy spectrum of the Sr / Y-90β radiation field was measured using a SiPIN detector; the SiPIN detector was connected to a matching preamplifier, main amplifier, and digital multichannel.

5. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 4, characterized in that, When performing energy spectrum measurements of the Sr / Y-90β radiation field using the SiPIN detector, a 3 mg·cm² coverage is applied to the front window of the SiPIN detector. 2 Aluminized polyester film.

6. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 4, characterized in that, When performing energy spectrum measurements of the Sr / Y-90β radiation field using the SiPIN detector, the absorbed dose rate in step S1 is compared with that in step S1. The method for measuring the uniformity distribution is the same as that for the SiPIN detector, which is placed at the same position as the sensitive volume center of the ionization chamber. After each set of cumulative charge readings is measured in the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum distribution of the Sr / Y-90β radiation field at the current position.

7. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 6, characterized in that, Step S3 includes the following specific steps: S31. Using MCNP simulation to establish an ICRU tissue sphere model, a method for calculating the conversion coefficient of absorbed dose rate to directional dose equivalent rate is obtained. S32. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes. S33. Combining the measurement points obtained in step S1 with the absorbed dose rate at each moving point. Targeted dose equivalent rate in Sr / Y-90β radiation field was obtained The regional distribution of.

8. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 7, characterized in that, Step S32 includes the following specific steps: S321. Based on the results of measuring the energy spectrum region distribution of the Sr / Y-90β radionuclide using the SiPIN detector and the matching BSS2 standard device, the conversion coefficient H′(3,T) / D corresponding to the change in the energy spectrum region distribution of the β radiation field of the Sr / Y-90β radionuclide is calculated according to formula (5). T ; Wherein, H′(3,T) is the small volume element directional dose equivalent at a surface depth of 3 mm in the ICRU tissue sphere model under Sr / Y-90β radionuclide irradiation, and Sv; Φ E The energy E of the Sr / Y-90β radionuclide, m -3 ; Q is the β-particle quality factor, taken as Q = 1Sv / Gy; Energy deposition per unit mass within a small volume element, J / kg; D T,E For the injection volume Φ E The deposition energy of Sr / Y-90β radionuclides with energy E in a small volume element, J / kg; D T The deposition energy of the Sr / Y-90β radionuclide in a small volume element, J / kg; S322. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate when the energy spectrum distribution of the Sr / Y-90β radiation field changes.

9. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 8, characterized in that, Step S33 includes the following specific steps: calculating the measurement points and absorbed dose rates at each moving point obtained in step S1. The measurement result is multiplied by the corresponding absorption dose rate-directional dose equivalent rate conversion factor H′(3,T) / D from the absorption dose rate-directional dose equivalent rate conversion factor database. T The directional dose equivalent rate at the measurement point and at each moving point was calculated. Thus, the directional dose equivalent rate in the β radiation field is obtained. The regional distribution of.

10. The method for calibrating the ocular lens assessment value of β-standard field directional dose equivalent rate according to claim 1, characterized in that, In step S4, the area where the deviation of the directional dose equivalent rate from the measurement point does not exceed ±5% is selected and identified as the directional dose equivalent rate of the β radiation field. Uniform region.

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