Shield structure and design method of a thyroid counter

Abstract

The application mainly provides a shielding body structure of a thyroid counter and a design method, the shielding body structure is installed on a detector of the thyroid counter, a thyroid model is arranged on one side of the detector, and the shielding body structure comprises a front-end shielding body, a side shielding body, one end of the side shielding body is detachably connected with the front-end shielding body, and a rear-end shielding body is detachably connected with the other end of the side shielding body; wherein the front-end shielding body is arranged at one end of the detector close to the thyroid model, and the rear-end shielding body is arranged at one end of the detector away from the thyroid model. The application can effectively shield background interference in the measurement process under the condition of ensuring the measurement efficiency, and can be widely applied to thyroid measurement of people of different ages, and is suitable for a wide range of applications.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ionizing radiation monitoring, in particular to a shielding structure of a thyroid counter and a design method thereof. BACKGROUND

[0002] The thyroid counter is mainly used for measuring the thyroid region of the human body to obtain the content of radioactive iodine in the region, so as to analyze and evaluate the intake of radioactive iodine in the human body and the radiation dose caused thereby. The thyroid counter is mainly applied in the fields of nuclear accidents, nuclear emergencies and nuclear medicine, and the range of personnel involved is relatively large. Generally speaking, the thyroid counter mainly comprises a gamma detector, a digital multi-channel analyzer and a shielding body, wherein the gamma detector usually adopts a cylindrical sodium iodide detector, which has the advantages of good angular response and high detection efficiency; the shielding body, also known as a collimator, mainly functions to limit the measurement region, shield the interference of the environmental background and the radioactive substances in other regions of the human body. At present, there is no mature and standardized thyroid counter measurement system in China, and due to the limitations of the shielding body design, some thyroid measurement devices have the following deficiencies: the measured objects are mainly adult humans, the applicable range is limited; the measurement region is limited too large or too small; the interference of the environmental background and the radioactive substances in other regions of the human body is not sufficiently shielded, which affects the use range and application effect of the thyroid counter.

[0003] The above problems need to be solved. SUMMARY

[0004] The present application discloses a shielding structure of a thyroid counter and a design method thereof, aiming to solve the technical problems existing in the prior art.

[0005] The present application adopts the following technical solutions:

[0006] On one hand, the present application provides a shielding structure of a thyroid counter, which is installed on a detector of the thyroid counter, a thyroid model is arranged on one side of the detector, and the shielding structure comprises: a front-end shielding body; a side shielding body arranged on the outer side of the detector, one end of the side shielding body being detachably connected with the front-end shielding body; and a rear-end shielding body detachably connected with the other end of the side shielding body; wherein the front-end shielding body is arranged at one end of the detector close to the thyroid model, and the rear-end shielding body is arranged at one end of the detector away from the thyroid model.

[0007] Preferably, the front-end shielding body is in a horn-shaped structure, which is used for limiting the effective measurement region of the detector and shielding the radiation interference in front of the side of the detector.

[0008] Preferably, the opening angle of the front shielding body is 0-60°.

[0009] Preferably, the side shielding body is a cylindrical structure, and the side shielding body is used for shielding the radiation interference on the side of the detector.

[0010] Preferably, the rear shielding body is a circular plate structure.

[0011] Preferably, the rear shielding body is connected with the side shielding body through bolts, and the side shielding body is connected with the front shielding body through threads.

[0012] Preferably, the rear shielding body is provided with a wiring hole, and the wiring hole is designed as an inclined hole for connecting the signal cable of the detector.

[0013] Preferably, the thickness of the front shielding body, the side shielding body and the rear shielding body is 0.5cm-3cm.

[0014] Preferably, the material of the front shielding body, the side shielding body and the rear shielding body is lead or tungsten.

[0015] According to another aspect of the embodiment of the present application, a design method of a shielding body structure of a thyroid counter is also provided, which is applied to any one of the shielding body structures of the thyroid counter, and includes:

[0016] Measuring the size of the detector, wherein the size includes length and diameter;

[0017] Determining the size of the side shielding body and the rear shielding body based on the size of the detector;

[0018] Determining the opening angle of the front shielding body according to the size of the measured object and the measuring distance;

[0019] Using the Monte Carlo method to simulate and calculate the shielding degree of the shielding body structure, and determining the thickness of the shielding body.

[0020] The technical solution adopted by the present application can achieve the following beneficial effects:

[0021] This invention primarily provides a shielding structure and design method for a thyroid counter. The shielding structure is installed on the detector of the thyroid counter, with a thyroid model disposed on one side of the detector. The shielding structure includes: a front shield; a side shield disposed on the outside of the detector, one end of which is detachably connected to the front shield; and a rear shield detachably connected to the other end of the side shield. The front shield is disposed at the end of the detector closer to the thyroid model, and the rear shield is disposed at the end of the detector farther from the thyroid model. This invention can effectively shield background interference during the measurement process while ensuring measurement efficiency, and can be widely applied to thyroid measurements in different age groups, thus having a wide range of applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 This is a schematic diagram of the shielding structure of the thyroid counter provided in Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the front shield of the shielding structure of a thyroid counter provided in Embodiment 1 of the present invention;

[0025] Figure 3 A schematic diagram of the front shield of another shielding structure for a thyroid counter provided in Embodiment 1 of the present invention;

[0026] Figure 4 This is a flowchart of a shielding structure design method for a thyroid counter provided in Embodiment 2 of the present invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Front shield; 2. Side shield; 3. Rear shield; 4. Detector; 5. Threaded interface; 6. Bolt; 7. Thyroid model; 8. Wiring hole. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0030] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be magnetic connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, in the description of the present application, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three or more, etc., unless otherwise explicitly specified and limited.

[0031] Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0032] To solve the problems existing in the prior art, the shielding body structure of the thyroid counter and the design method thereof are provided.

[0033] The shielding body structure of the thyroid counter of the present application is mounted on the detector 4 of the thyroid counter, and the thyroid model 7 is arranged on one side of the detector 4. The shielding body structure comprises: a front end shielding body 1; a side shielding body 2 arranged on the outside of the detector 4, one end of the side shielding body 2 being detachably connected with the front end shielding body 1; and a rear end shielding body 3 detachably connected with the other end of the side shielding body 2. The front end shielding body 1 is arranged at one end of the detector 4 close to the thyroid model 7, and the rear end shielding body 3 is arranged at one end of the detector 4 away from the thyroid model 7.

[0034] In some preferred embodiments, the shielding structure is designed as the front end shielding body 1, the side shielding body 2 and the rear end shielding body 3. The side shielding body 2 and the rear end shielding body 3 are detachably connected, which is convenient for disassembly and assembly. The shielding body structure adopts a modular shielding body construction method, and the measurement needs of the thyroid of different age groups can be met by replacing the front end shielding body 1.

[0035] In some preferred embodiments, the front end shielding body 1 is a horn-shaped structure. The front end shielding body 1 is used to define the effective measurement area of the detector 4 and shield the radiation interference in front of the side of the detector 4.

[0036] Figure 1 The schematic diagram of the shielding body structure of the thyroid counter provided for the embodiment 1 of the present application is shown in Figure 1As shown, the effective measurement area of the detector 4 is formed in a circular cross section at a certain distance along the direction of the opening angle of the inner side of the front shielding body 1, and the circular measurement area with a radius R formed at the measurement distance L is consistent with the size of the measured object (thyroid).

[0037] In some preferred embodiments, the opening angle of the front shielding body 1 is 0-60°, and the opening angle of the front shielding body 1 can be designed according to the size of the measured object and the measurement distance.

[0038] Figure 2 The structural schematic diagram of the front shielding body of the shielding body structure of the thyroid counter provided for the embodiment 1 of the present application is shown in Figure 2 As shown, taking a cylindrical sodium iodide detector as an example, and taking an adult male thyroid as the measurement object, as shown in Figure 1 The front end surface of the detector 4 is opposite to the surface of the thyroid model 7, the length of the radius of the detector 2.5 cm (i.e. the length of oa is 2.5 cm), the measurement distance L is 15 cm, and the center of the thyroid model 7 is located on the axis of the detector 4; the thyroid model 7 is a cylinder with a diameter of 12 cm and a height of 12 cm, and R=6 cm. Defining the center point of the front end surface of the detector 4 as o, the points where the detector 4 intersects with the front shielding body 1 as a and b, and the symmetric boundary points of the thyroid model 7 in the height direction as c and d, the inner side surface of the front shielding body 1 and the effective measurement area of the detector 4 are defined along the ac and bd directions, the effective measurement area can cover the thyroid model 7, and the cross section of the effective measurement area of the detector 4 at the positions of c and d is a circle with a radius R, so the opening angle of the front shielding body can be determined as 2arctan[(R-oa) / L], which is about 26.3°; in the direction of the radius R of the effective measurement area, the deviations are 0.2R and 0.4R in sequence, i.e. Figure 1 ce=ef=0.2R, oe and bf are connected, and ac intersects with p, so the front boundary of the front shielding body 1 can be defined.

[0039] Figure 3 The structural schematic diagram of the front shielding body of another shielding body structure of the thyroid counter provided for the embodiment 1 of the present application is shown in Figure 3 As shown, taking a cylindrical sodium iodide detector as an example, and taking a 5-year-old child thyroid as the measurement object, as shown in Figure 1As shown, the front end surface of the detector 4 is opposite to the surface of the thyroid model 7, the length of the detector radius 2.5 cm, i.e. the length of oa is 2.5 cm, the measuring distance L is 15 cm, and the center of the thyroid model 7 is located on the axis of the detector 4; the thyroid model 7 is a cylinder with a diameter of 8.2 cm and a height of 8.2 cm, and R=4.1 cm. The center point of the front end surface of the detector 4 is defined as o, the points where the detector 4 intersects with the front end shielding body 1 are defined as a and b, and the boundary points of the thyroid model 7 in the height direction are defined as c and d, so the inner side surface of the front end shielding body 1 and the effective measuring area of the detector 4 are defined along the ac and bd directions, the effective measuring area can cover the thyroid model 7, and the cross section of the effective measuring area of the detector 4 at the positions of c and d is a circle with a radius R, so the opening angle of the front end shielding body can be determined as 2arctan[(R-oa) / L], which is about 12.2°; in the radius R direction of the effective measuring area, the effective measuring area deviates from the center o by 0.2R and 0.4R in turn, i.e. Figure 1 ce=ef=0.2R, oe and bf are connected, and p is the intersection point of ac, so the front boundary of the front end shielding body 1 can be defined.

[0040] Preferably, the thickness of the front end shielding body 1 is determined by Monte Carlo simulation, the iodine-131 point source is located on the axis of the detector 4, the distance from the point source to the front end surface of the detector 4 is L, and the detection efficiency of the detector 4 for the point source is ε, so the detection efficiency of the detector 4 for the point source in the effective measuring area is not less than 0.9ε, and the detection efficiency decreases rapidly as the point source deviates from the center o in the radius R direction of the effective measuring area; when the point source deviates by 0.2R, the detection efficiency decreases to less than 0.5ε, i.e. the detection efficiency of the detector 4 for the point source outside pe is less than 0.5ε; when the point source deviates by 0.4R or more, the detection efficiency decreases to less than 0.01ε, i.e. the detection efficiency of the detector 4 for the point source outside pf is less than 0.01ε; therefore, the thickness pg of the front end shielding body 1 for iodine-131 is 1.5 cm, which can meet the needs of iodine-131 measurement.

[0041] The thicknesses of the side shielding body 2 and the rear end shielding body 3 can also be determined by the Monte Carlo simulation method, and the thicknesses of the side shielding body 2 and the rear end shielding body 3 are in the range of 0.5 cm to 3 cm according to different measurement needs, and 2 cm can meet the needs of iodine-131 measurement.

[0042] In some preferred embodiments, the side shielding body 2 has a cylindrical structure, and the side shielding body 2 is used for shielding the radiation interference around the detector 4. The detection efficiency of the detector 4 for the radioactive source outside the side shielding body 2 with a certain thickness is less than 0.01ε.

[0043] In some preferred embodiments, the inner diameter of the side shielding body 2 is slightly larger than the outer diameter of the detector 4, so as to ensure that the side shielding body 2 is attached to the detector 4.

[0044] In some preferred embodiments, the rear shielding body 3 is in a circular plate structure, which can shield the rear end of the detector 4.

[0045] In some preferred embodiments, the rear shielding body 3 is connected to the side shielding body 2 by bolts, and the side shielding body 2 is connected to the front shielding body 1 by threads.

[0046] Preferably, at least one first threaded hole is formed on the end surface of the side shielding body 2 away from the thyroid model 7, and at least one second threaded hole is formed on the rear shielding body 3 in one-to-one correspondence, and the rear shielding body 3 and the side shielding body 2 are detachably connected together by bolts passing through the second threaded hole on the rear shielding body 3 and the first threaded hole on the side shielding body 2, which facilitates installation and disassembly.

[0047] Preferably, an external thread is formed on the end of the side shielding body 2 close to the thyroid model 7, and an internal thread is formed on the end of the front shielding body 1, and the front shielding body 1 and the side shielding body 2 are connected by the internal thread and the external thread, which is a modular structure, facilitating installation and disassembly, and the total thickness of the side shielding body 2 and the front shielding body 1 at the interface needs to be equal to the thickness of the side shielding body 2 at other positions.

[0048] In some preferred embodiments, a wiring hole 8 is formed on the rear shielding body 3, which is designed as an inclined hole for connecting the signal cable of the detector 4 and preventing the background radiation from directly irradiating the rear end of the detector 4, thereby reducing the background interference.

[0049] In some preferred embodiments, the thickness of the front shielding body 1, the side shielding body 2 and the rear shielding body 3 is 0.5-3 cm.

[0050] In some preferred embodiments, the material of the front shielding body 1, the side shielding body 2 and the rear shielding body 3 is one of lead and tungsten. The heavy metal materials such as lead and tungsten can reduce the volume of the device while ensuring the shielding effect.

[0051] According to the embodiments of the present application, a design method of the thyroid counter shielding body structure is also provided. It should be noted that the steps shown in the flowchart can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0052] Figure 4 is a flowchart of the design method of the thyroid counter shielding body structure in an embodiment of the present application, as shown in Figure 4 The method comprises the following steps:

[0053] Step S1, measuring the size of the probe 4, wherein the size includes length, diameter;

[0054] Step S2, determining the size of the side shielding body and the back-end shielding body based on the size of the probe 4;

[0055] Step S3, determining the front-end shielding body opening angle according to the size of the measurement object, i.e. the thyroid model 7, and the measurement distance L, wherein the front-end shielding body opening angle can be determined as 2arctan[(R-oa) / L] as described in Embodiment 1;

[0056] Step S4, constructing a mathematical model of the probe, the shielding body and the radioactive point source using Monte Carlo simulation software, placing γ radioactive point sources of different energies at different distances from the front end surface of the probe in the axial direction of the probe and at different distances in the radial direction, and using the Monte Carlo method to simulate and calculate the shielding effect of the shielding body structure and determine the shielding body thickness. The specific method is as follows: a mathematical model of the probe 4, the shielding body and the γ radioactive point source is constructed using Monte Carlo simulation software, the point source is located on the axis of the probe 4, and the detection efficiency of the probe 4 for the point source is ε when the point source is at a distance L from the front end surface of the probe 4, the detection efficiency of the probe 4 for the radioactive source in the effective measurement area is not less than 90%×ε, and the detection efficiency decreases rapidly as the radioactive source deviates along the direction of the effective measurement area R, specifically, the detection efficiency decreases to 50%×ε or less when deviating by 20%×R, and the detection efficiency decreases to 1%×ε or less when deviating by 40%×R or more.

[0057] Through the above steps S1 to S4, the shielding body structure can be customized according to the measurement object, the measurement area can be more accurately defined, and the environmental background and the interference of radioactive substances in other areas of the human body can be reduced, thereby solving the problems of small application range of the thyroid counter and improper shielding design in the related art.

[0058] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative and not limiting, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection of the present application.

Claims

1. A shielding structure for a thyroid counter, characterized in that, The shielding structure is installed on the detector (4) of the thyroid counter, and the thyroid model (7) is disposed on one side of the detector (4). The shielding structure includes: Front shield (1); Side shield (2), the side shield (2) is disposed on the outside of the detector (4), and one end of the side shield (2) is detachably connected to the front shield (1); The rear shield (3) is detachably connected to the other end of the side shield (2); The front shield (1) is located at one end of the detector (4) near the thyroid model (7), and the rear shield (3) is located at one end of the detector (4) away from the thyroid model (7). Measure the size of the detector (4), wherein the size includes length and diameter; based on the size of the detector (4), determine the size of the side shield (2) and the rear shield (3); determine the angle of the front shield (1) according to the size of the object being measured and the measurement distance, the angle of the front shield (1) is 2arctan[(R-oa) / L], where L is the measurement distance, the center point of the front face of the detector (4) is o, the distance between the center point of the front face of the detector (4) and the thyroid model (7) is L, the points where the detector (4) and the front shield (1) intersect are a and b respectively, the boundary points of the height direction of the thyroid model (7) are c and d respectively, oa is the distance between the center point of the front face of the detector (4) and the point where the detector (4) and the front shield (1) intersect are a and b respectively, the boundary points of the height direction of the thyroid model (7) are c and d respectively, oa is the distance between the center point of the front face of the detector (4) and the point where the detector (4) and the front shield (1) intersect are R, the radius of the effective measurement area of ​​the thyroid model (7) is 0~60°; Points e and f are obtained by successively deviating from the radius R of the effective measurement area by 0.2R and 0.4R, respectively. Connect oe and bf, and intersect with ac at point p. This area is the boundary of the front shield (1). The detection efficiency of a point source located on the axis of the detector (4) at a distance L from the front end face of the detector (4) is ε. The point source is moved to deviate along the radius R of the effective measurement area. Using Monte Carlo simulation, when it is within the effective measurement range, i.e. ≤R, the detection efficiency is not less than 0.9ε. When the deviation exceeds the effective measurement range by 0.2R, the detection efficiency decreases to below 0.5ε. When the deviation exceeds the effective measurement range by 0.4R, the detection efficiency decreases to below 0.01ε. This is the thickness of the front shield. Using Monte Carlo simulation, when the point source is outside the side shield and the rear shield, the shield thickness is adjusted to the detection efficiency being less than 0.01ε. This thickness is the thickness outside the side shield and the rear shield. The thickness of the front shield (1), the side shield (2), and the rear shield (3) is 0.5cm-3cm.

2. The shielding structure of the thyroid counter according to claim 1, characterized in that, The front shield (1) is a horn-shaped structure. The front shield (1) is used to define the effective measurement area of ​​the detector (4) and to shield the radiation interference in front of the detector (4).

3. The shielding structure of the thyroid counter according to claim 1, characterized in that, The side shield (2) is a cylindrical structure and is used to shield the radiation interference around the detector (4).

4. The shielding structure of the thyroid counter according to claim 1, characterized in that, The structure of the rear shield (3) is a circular plate structure.

5. The shielding structure of the thyroid counter according to claim 4, characterized in that, The rear shield (3) is connected to the side shield (2) by bolts, and the side shield (2) is connected to the front shield (1) by threads.

6. The shielding structure of the thyroid counter according to claim 1, characterized in that, The rear shield (3) is provided with a wiring hole (8), which is used to connect the signal cable of the detector (4).

7. The shielding structure of the thyroid counter according to claim 1, characterized in that, The front shield (1), the side shield (2), and the rear shield (3) are made of lead or tungsten.

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