阅读说明：本技术 一种核医学受检者周围辐射剂量率确定方法及系统 (Method and system for determining peripheral radiation dose rate of nuclear medicine examinee ) 是由 丁库克 岳海振 何鑫雨 丁立新 林琳 唐小哲 刘瑶 陈园生 武云云 姜晓燕 尚兵 于 2021-06-09 设计创作，主要内容包括：本发明实施例公开了一种核医学受检者周围辐射剂量率确定方法及系统。该方法包括：获取受检者的人体模型参数以及目标图像的灰度值；目标图像包括受检者的PET/CT图像或PET图像；使用周围辐射剂量率时空分布预测模型,根据受检者的人体模型参数以及灰度值,确定受检者周围辐射剂量率的时空分布；其中,周围辐射剂量率时空分布预测模型根据灰度放射性比活度关系以及人体模型确定,灰度放射性比活度关系包括灰度与对应人体结构单位放射性比活度之间的关系。本发明实施例实现了对受检者周围辐射剂量率时空分布的确定。(The embodiment of the invention discloses a method and a system for determining the peripheral radiation dose rate of a nuclear medicine examinee. The method comprises the following steps: acquiring human body model parameters of a detected person and gray values of a target image; the target image comprises a PET/CT image or a PET image of the subject; determining the space-time distribution of the radiation dose rate around the detected person according to the human body model parameters and the gray value of the detected person by using a space-time distribution prediction model of the surrounding radiation dose rate; the prediction model of the spatial-temporal distribution of the ambient radiation dose rate is determined according to a gray level radioactivity relation and a human body model, wherein the gray level radioactivity relation comprises the relation between gray levels and corresponding human body structure unit radioactivity. The embodiment of the invention realizes the determination of the spatial and temporal distribution of the radiation dose rate around the examinee.)

1. A method of determining a radiation rate around a nuclear medical subject, comprising:

acquiring human body model parameters of a detected person and gray values of a target image; the target image comprises a PET/CT image or a PET image of the subject;

determining the space-time distribution of the radiation dose rate around the detected person according to the human body model parameters of the detected person and the gray value by using a space-time distribution prediction model of the surrounding radiation dose rate; the prediction model of the spatial-temporal distribution of the ambient radiation dose rate is determined according to a gray level radioactivity relation and a human body model, wherein the gray level radioactivity relation comprises the relation between gray levels and corresponding human body structure unit radioactivity.

2. The method of claim 1, wherein the method of determining the nuclear medical subject peripheral radiation dose rate further comprises:

constructing a human body model;

the human body model comprises a plurality of cylinder models, any cylinder model is used for representing a structural unit of a human body, and the human body model parameters comprise the size of each cylinder model.

3. A method of determining a peripheral radiation dose rate to a nuclear medical subject as claimed in claim 2 wherein said model of prediction of the spatial temporal distribution of the peripheral radiation dose rate is constructed by:

according to the relation between radioactive decay and time, the relation between gray level radioactivity and the gray level of the infinitesimal in any cylinder model, carrying out volume integration on the radiation dose rate of the infinitesimal in any cylinder model to the same space position outside the human body model to obtain the spatial-temporal distribution of the radiation dose rate around any cylinder model;

and correspondingly superposing the spatial and temporal distribution of the peripheral radiation dose rate of each cylinder model to obtain the spatial and temporal distribution prediction model of the peripheral radiation dose rate.

4. A method for determining a radiation dose rate around a nuclear medical subject as claimed in claim 2 wherein said plurality of cylinder models comprises: a head cylinder model, a torso cylinder model, a leg cylinder model, a heart cylinder model, and a bladder cylinder model.

5. A method for determining a radiation dose rate around a nuclear medical subject as claimed in claim 3 wherein the gray scale of the bins in any of said cylindrical models comprises: the average gray scale of the human body structure unit corresponding to any one cylinder model on the PET/CT image or the PET image.

6. A method of determining a peripheral radiation dose rate to a nuclear medical subject as claimed in claim 3, further comprising, prior to constructing the model of prediction of the spatial-temporal distribution of the peripheral radiation dose rate:

under the state of no urination, calculating the gray level radioactivity ratio relation k according to a first calculation formula;

the first calculation formula is:

wherein the content of the first and second substances,D₀is the initial activity value of the radionuclide in the body of the subject, lambda is the self radioactive decay coefficient of the radionuclide, t₁Timing when radioactive elements are injected into human body, shooting PET/CT image or PET image, k is the proportional coefficient between the activity value of radioactive nuclide and the gray value of image, h₁Height of the subject's head cylinder model, h₂Height of the subject's torso cylinder model, h₃Height of the subject's leg cylinder model, h₄Height, h, of a heart cylinder model₅Height, R, of a bladder cylinder model₁Is the radius, R, of a cylindrical model of the subject's head₂Is the equivalent radius of the torso cylinder model, R₃Radius of a cylindrical model of the subject's leg, R₄Radius of the heart cylinder model, R₅Is the radius of the cylindrical model of the bladder,representing the gray scale of the head cylinder model in the PET/CT image or the PET image,representing the gray scale of the voxel in the torso cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the cardiac cylinder model on the PET/CT image or PET image,representing PET/CT images or bladder cylinders on PET imagesThe gray scale of the infinitesimal elements in the model,representing the gray scale of the micro-elements in the leg cylinder model on the PET/CT image or PET image.

7. A method of determining a peripheral radiation dose rate to a nuclear medical subject as claimed in claim 3, further comprising, prior to constructing the model of prediction of the spatial-temporal distribution of the peripheral radiation dose rate:

under the state of urine emptying, calculating the gray-level radioactivity relation k according to a second calculation formula;

the second calculation formula is:

wherein the content of the first and second substances,D₀is the initial activity value, lambda, of a radionuclide in the subject₁Is the self-radioactive decay coefficient of the radionuclide, lambda₂Is the coefficient of variation of the biological metabolism in the internal organs, t₁Timing when radioactive elements are injected into human body, shooting PET/CT image or PET image, k is the proportional coefficient between the activity value of radioactive nuclide and the gray value of image, h₁Height of the subject's head cylinder model, h₂Height of the subject's torso cylinder model, h₃Height of the subject's leg cylinder model, h₄Height, R, of a heart cylinder model₁Is the radius, R, of a cylindrical model of the subject's head₂Is the equivalent radius of the torso cylinder model, R₃Radius of a cylindrical model of the subject's leg, R₄Is the radius of the heart cylinder model,representing the gray scale of the head cylinder model in the PET/CT image or the PET image,representing the gray scale of the voxel in the torso cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the cardiac cylinder model on the PET/CT image or PET image,representing the gray scale of the micro-elements in the leg cylinder model on the PET/CT image or PET image.

8. A method for nuclear medicine subject peripheral radiation dose rate determination as defined in any of claims 1 to 4, wherein the model for predicting the peripheral radiation dose rate spatial distribution includes a dose rate modification factor determined from actual measurements of the peripheral radiation dose rate spatial temporal distribution.

9. A method of nuclear medicine subject peripheral radiation dose rate determination as claimed in claim 6 or 7, wherein the method of determining the equivalent radius of the torso cylinder model comprises:

according toCalculating the equivalent radius R of the trunk cylinder model₂Wherein Mg is the body weight, H is the body height, V is the body volume, H₁Height h of human head₂Height h of human body₃Is the height, R, of the human leg₁Radius of human head, R₃Is the radius of the leg of the human body, and rho is the average density of the human body.

10. A nuclear medicine subject ambient radiation rate determination system, comprising:

the acquisition module is used for acquiring human body model parameters of a detected person and the gray value of the target image; the target image comprises a PET/CT image or a PET image of the subject;

the prediction module is used for determining the space-time distribution of the radiation dose rate around the detected person according to the human body model parameters of the detected person and the gray value by using a space-time distribution prediction model of the surrounding radiation dose rate; the prediction model of the spatial-temporal distribution of the ambient radiation dose rate is determined according to a gray level radioactivity relation and a human body model, wherein the gray level radioactivity relation comprises the relation between gray levels and corresponding human body structure unit radioactivity.

11. The nuclear medicine subject ambient radiation rate determination system of claim 10, further comprising:

the human body model building module is used for building a human body model; the human body model comprises a plurality of cylinder models, any cylinder model is used for representing a structural unit of a human body, and the human body model parameters comprise the size of each cylinder model.

12. The nuclear medical subject ambient radiation rate determination system of claim 11, further comprising: a prediction model construction module comprising a first unit and a second unit;

the first unit is used for carrying out volume integration on the radiation dose rate of the micro-element in any cylinder model to the same space position outside the human body model according to the relation between radioactive decay and time, the relation between gray level radioactivity and the gray level of the micro-element in any cylinder model, so as to obtain the space-time distribution of the radiation dose rate around any cylinder model;

the second unit is used for correspondingly superposing the peripheral radiation dose rate space-time distribution of each cylinder model to obtain the peripheral radiation dose rate space-time distribution prediction model.

Technical Field

The invention relates to the field of nuclear medicine radiation, in particular to a method and a system for determining the peripheral radiation dose rate of a nuclear medicine examinee.

Background

The PET/CT technique combines PET (Positron Emission Tomography) and CT (Computed Tomography) for scanning imaging. Prior to scan imaging, the PET/CT subject is injected with a radiopharmaceutical (e.g., fluorodeoxyglucose).

After the radiopharmaceutical is injected, the subject becomes a "free-moving" radiation source: on one hand, the subject himself (including tissues and organs) is subjected to certain radiation damage, and on the other hand, a dynamically changing radiation field is formed around the subject. This radiation field may cause unnecessary exposure to personnel in contact with the subject with the radiopharmaceutical in the body. These persons may be referred to as professional illuminators, such as attending doctors, nurses, etc., and public illuminators, such as accompanying persons, family members, etc.

In order to protect the health of the above personnel, the radiation dose rate distribution around the subject should be determined first, and therefore, a technical scheme capable of measuring the radiation dose rate distribution around the nuclear medical subject is urgently needed at present.

Disclosure of Invention

The embodiment of the invention aims to provide a method and a system for determining the peripheral radiation dose rate of a nuclear medical examinee.

In order to achieve the above object, the embodiment of the present invention provides the following solutions:

a method of nuclear medicine subject ambient radiation rate determination, comprising:

acquiring human body model parameters of a detected person and gray values of a target image; the target image comprises a PET/CT image or a PET image of the subject;

determining the space-time distribution of the ambient radiation dose rate of the examinee according to the human body model parameters of the examinee and the gray value by using a prediction model of the space-time distribution of the ambient radiation dose rate; the prediction model of the spatial-temporal distribution of the peripheral radiation dose rate is determined according to a gray level radioactivity relation and a human body model, wherein the gray level radioactivity relation comprises the relation between gray levels and corresponding human body structure unit radioactivity.

Optionally, the method for determining the radiation dose rate around the nuclear medical subject further includes:

constructing a human body model;

the human body model comprises a plurality of cylinder models, any cylinder model is used for representing a structural unit of a human body, and the human body model parameters comprise the size of each cylinder model.

Optionally, the process of constructing the prediction model of spatial and temporal distribution of ambient radiation dose rate includes:

according to the relation between radioactive decay and time, the relation between gray level radioactivity and the gray level of the infinitesimal in any cylinder model, carrying out volume integration on the radiation dose rate of the infinitesimal in any cylinder model to the same space position outside the human body model to obtain the spatial-temporal distribution of the radiation dose rate around any cylinder model;

and correspondingly superposing the spatial and temporal distribution of the peripheral radiation dose rate of each cylinder model to obtain the spatial and temporal distribution prediction model of the peripheral radiation dose rate.

Optionally, the plurality of cylinder models includes: a head cylinder model, a torso cylinder model, a leg cylinder model, a heart cylinder model, and a bladder cylinder model.

Optionally, the gray scale of the infinitesimal element in any one of the cylinder models includes: the average gray scale of the human body structure unit corresponding to any one cylinder model on the PET/CT image or the PET image.

Optionally, before constructing the prediction model of the spatial-temporal distribution of the ambient radiation dose rate, the method further includes:

under the state of no urination, calculating the gray level radioactivity ratio relation k according to a first calculation formula;

the first calculation formula is:

wherein the content of the first and second substances,D₀is the initial activity value of the radionuclide in the body of the subject, lambda is the self radioactive decay coefficient of the radionuclide, t₁Timing when radioactive elements are injected into human body, shooting PET/CT image or PET image, k is the proportional coefficient between the activity value of radioactive nuclide and the gray value of image, h₁Height of the subject's head cylinder model, h₂Height of the subject's torso cylinder model, h₃Height of the subject's leg cylinder model, h₄Height, h, of a heart cylinder model₅Height, R, of a bladder cylinder model₁Is the radius, R, of a cylindrical model of the subject's head₂Is the equivalent radius of the torso cylinder model, R₃Radius of a cylindrical model of the subject's leg, R₄Radius of the heart cylinder model, R₅Is the radius of the cylindrical model of the bladder,representing the gray scale of the micro-elements in the head cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the torso cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the cardiac cylinder model on the PET/CT image or PET image,representing the gray scale of the microelements in the bladder cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the PET/CT image or the leg cylinder model on the PET image.

Optionally, before constructing the prediction model of the spatial-temporal distribution of the ambient radiation dose rate, the method further includes:

under the state of urine emptying, calculating the gray-level radioactivity relation k according to a second calculation formula;

the second calculation formula is:

wherein the content of the first and second substances,D₀is the initial activity value, lambda, of a radionuclide in the subject₁Is the self-radioactive decay coefficient of the radionuclide, lambda₂Is the coefficient of variation of the biological metabolism in the internal organs, t₁The time of taking PET/CT image or PET image is timed according to the time of injecting radioactive element into human body, k is the proportionality coefficient between radioactive nuclide activity value and image gray scale value, h₁Height of the subject's head cylinder model, h₂Height of the subject's trunk cylinder model, h₃Height of the subject's leg cylinder model, h₄Height, R, of a heart cylinder model₁Is the radius, R, of a cylindrical model of the subject's head₂Is the equivalent radius of the torso cylinder model, R₃Radius of a cylindrical model of the subject's leg, R₄Is the radius of the heart cylinder model,representing the gray scale of the head cylinder model in the PET/CT image or the PET image,representing the gray scale of the voxel in the torso cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the cardiac cylinder model on the PET/CT image or PET image,representing the gray scale of the micro-elements in the leg cylinder model on the PET/CT image or PET image.

Optionally, the prediction model of the spatial-temporal distribution of the ambient radiation dose rate includes a dose rate modification factor, and the dose rate modification factor is determined by an actual measurement value of the spatial-temporal distribution of the ambient radiation dose rate.

Optionally, the method for determining the equivalent radius of the torso cylinder model includes:

according toCalculating the equivalent radius R of the trunk cylinder model₂Wherein Mg is the body weight, H is the body height, V is the body volume, H₁Height h of human head₂Height h of human body₃Is the height, R, of the human leg₁Radius of human head, R₃Is the radius of the leg of the human body, and rho is the average density of the human body.

The invention also provides a system for determining the peripheral radiation dose rate of a nuclear medical examinee, comprising:

the acquisition module is used for acquiring human body model parameters of a detected person and the gray value of the target image; the target image comprises a PET/CT image or a PET image of the subject;

the prediction module is used for determining the space-time distribution of the ambient radiation dose rate of the detected person according to the human body model parameters of the detected person and the gray value by using an ambient radiation dose rate space-time distribution prediction model; the prediction model of the spatial-temporal distribution of the ambient radiation dose rate is determined according to a gray level radioactivity relation and a human body model, wherein the gray level radioactivity relation comprises the relation between gray levels and corresponding human body structure unit radioactivity.

Optionally, the system for determining a radiation rate around the nuclear medical subject further includes:

the human body model building module is used for building a human body model; the human body model comprises a plurality of cylinder models, any cylinder model is used for representing a structural unit of a human body, and the parameters of the human body model comprise the size of each cylinder model.

Optionally, the nuclear medical subject ambient radiation rate determination system further comprises: a prediction model construction module comprising a first unit and a second unit;

the first unit is used for carrying out volume integration on the radiation dose rate of the infinitesimal in any one cylinder model at the same space position outside the human model according to the relation between radioactive decay and time, the relation between gray level radioactivity and the gray level of the infinitesimal in any one cylinder model, so as to obtain the space-time distribution of the peripheral radiation dose rate of any one cylinder model;

the second unit is used for correspondingly superposing the peripheral radiation dose rate space-time distribution of each cylinder model to obtain the peripheral radiation dose rate space-time distribution prediction model.

According to the specific embodiment provided by the invention, the following technical effects are disclosed: according to the method and the system for determining the peripheral radiation dose rate of the nuclear medicine examinee, a prediction model of the spatial-temporal distribution of the peripheral radiation dose rate of the examinee is determined according to the PET/CT image gray value or the relation between the PET image gray value and the corresponding human body structure unit radioactivity and the human body model of the examinee, the obtained human body model parameters and the image gray value are used as input data, and the prediction model of the spatial-temporal distribution of the peripheral radiation dose rate is used, so that the determination of the spatial-temporal distribution of the peripheral radiation dose rate of the examinee is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.

FIG. 1 is a schematic flow chart of a method for determining a radiation dose rate around a nuclear medical subject according to an embodiment of the present invention;

FIG. 2a is a diagram of geometric parameters of a human body of a subject in an embodiment of the present invention, and FIG. 2b is a diagram illustrating a standing state of a physical model of a "cylinder stack" of the human body of the subject in an embodiment of the present invention;

FIG. 3 is a schematic diagram of coordinate transformation according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a "infinitesimal" MN on a "line source" EF according to an embodiment of the present invention;

fig. 5 is a schematic diagram of performing surface integration (with a line segment EF as a infinitesimal) on a thin plane ABCD according to an embodiment of the present invention, fig. 5(a) is a line infinitesimal diagram, fig. 5(b) is a diagram of a position relationship between a point P and the plane ABCD, and fig. 5(c) is a rotation diagram of fig. 5 (b);

FIG. 6 is a schematic view of a cylinder with thin-face ABCD as "infinitesimal" in the embodiment of the present invention;

FIG. 7 is a schematic diagram illustrating an integration principle of a head cylinder model according to an embodiment of the present invention;

FIG. 8 is a projection of a head cylinder model in the XOY plane in an embodiment of the present invention;

FIG. 9a is a drawing of a graph h according to an embodiment of the present invention_p-h<Angle of 0 DEG theta₂Fig. 9b is a schematic diagram of the determination of h in the embodiment of the present invention_p-h>Angle of 0 DEG theta₂Determining a schematic diagram of (1);

FIG. 10 is a schematic diagram of the volume division of the right half cylinder of the head cylinder model in the embodiment of the present invention

FIG. 11 is a schematic view of the left half cylinder of the head cylinder model according to an embodiment of the present invention;

FIG. 12 shows an embodiment of the present invention¹⁸A whole body kinetic map of F-FDG;

FIG. 13 is a schematic diagram of the PET/CT or PET image gray scale values and the radioactivity ratio of the corresponding region of the subject according to the embodiment of the present invention;

fig. 14 is a schematic structural diagram of a radiation rate determination system for a nuclear medical subject according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a method and a system for determining the peripheral radiation dose rate of a nuclear medicine examinee (system for short).

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The method and the system for determining the peripheral radiation dose rate of the nuclear medical examinee are introduced firstly, and the core idea is as follows:

after the nuclear medicine examinee is injected with the radioactive medicine, the nuclear medicine examinee becomes a radioactive source, and a radiation field which changes dynamically with time is formed on the periphery of the radioactive source. In terms of spatial dimension, in the radiation field, different positions differ in radiation intensity (radiation dose rate) due to the distance from the radiation source (nuclear medical subject); in the time dimension, the intensity of the radiation at each location in the radiation field decays over time.

To determine the spatial and temporal distribution of the radiation dose rate around the subject, a prediction model of the spatial and temporal distribution of the ambient radiation dose rate (a prediction model for short) can be used to predict the radiation intensity at each location in the radiation field generated by a radiation source (a nuclear medicine subject) from both the temporal and spatial dimensions.

The prediction model of the spatial-temporal distribution of the ambient radiation dose rate is established based on a gray level radioactivity relation (relation between gray levels and corresponding human body structure unit radioactivity) and a human body model.

In the prediction process, the acquired human body model parameters of the examinee and the gray value of the target image (the examinee PET/CT image or the PET image) can be input into the surrounding radiation dose rate space-time distribution prediction model, and the radiation dose rate space-time distribution around the examinee can be obtained.

Referring to fig. 1, based on the above core idea, the method for determining the peripheral radiation dose rate of a nuclear medical examinee performed by the above system at the time of formal prediction includes the steps of:

step 101: acquiring human body model parameters of a detected person and gray values of a target image;

the target image includes a PET/CT image or a PET image of the subject.

Step 102: determining the spatial-temporal distribution of the radiation dose rate around the detected person according to the human body model parameters of the detected person and the gray value by using a spatial-temporal distribution prediction model (short for prediction model) of the ambient radiation dose rate;

specifically, the human body model parameters of the subject acquired in step 101 and the gray-scale value of the target image may be input into the prediction model, so as to obtain the spatial and temporal distribution of the radiation dose rate around the subject.

Therefore, in the embodiment of the invention, the spatial and temporal distribution prediction model of the peripheral radiation dose rate of the detected person can be determined according to the gray value of the PET/CT image or the relation between the gray value of the PET image and the unit radioactivity of the corresponding human body structure and the human body model of the detected person, and the spatial and temporal distribution of the peripheral radiation dose rate of the detected person is determined by using the obtained human body model parameters and the image gray value as input data and the spatial and temporal distribution prediction model of the peripheral radiation dose rate.

In other embodiments of the present invention, before the prediction of the spatial-temporal distribution of the ambient radiation dose rate is performed on a specific examinee by using the spatial-temporal distribution prediction model of the ambient radiation dose rate, a construction work of the spatial-temporal distribution prediction model of the ambient radiation dose rate is also required, and the construction process thereof may include the following steps:

(1) construction of a mannequin

The structural units (i.e. organs, parts, etc.) of the human body are equivalent to obtain equivalent models corresponding to the human body, i.e. the human body models described herein.

For example, referring to fig. 2a, the human body structure units of the human body can be equivalent to cylinders, so that the whole human body can be equivalent to a human body model composed of a plurality of cylinder models. Based on this, the above-mentioned parameters of the human body model include the size of each cylinder model constituting the human body model.

In particular, a structural unit may include a body organ (heart, bladder, etc.) or region (head, torso, legs, etc.).

Referring to fig. 2b, the plurality of cylinder models may include: a head cylinder model, a torso cylinder model, a leg cylinder model, a heart cylinder model, and a bladder cylinder model. Of course, in other embodiments, the phantom may include a cylindrical phantom representing other different body parts or organs.

In another example, the above-mentioned physical body model can be established under the same coordinate system, i.e. each cylinder model is under the same coordinate system.

(2) Construction of prediction model of spatial and temporal distribution of ambient radiation dose rate

On the basis of obtaining the human body model, according to the gray scale of the infinitesimal in any cylinder model, the gray scale radioactivity ratio relation (described above) and the relation between radioactive decay and time, the volume integration is carried out on the radiation dose rate of the infinitesimal in any cylinder model to the same space position (such as a P point) outside the human body model, and the time distribution of the radiation dose rate of the infinitesimal in any cylinder model to the P point outside the human body model is obtained.

Similarly, the volume integration is carried out on other spatial positions outside the human body model in the same way to obtain the time distribution of the radiation dose rate of the cylinder model to other spatial positions. The spatial-temporal distribution of the ambient radiation dose rate corresponding to a certain cylinder model comprises: the cylinder model is used for time distribution of radiation dose rate at each space position outside the body.

And then, correspondingly superposing the spatial and temporal distribution of the peripheral radiation dose rate corresponding to each cylinder model to obtain the spatial and temporal distribution prediction model of the peripheral radiation dose rate.

In one example, the radioactivity k can be understood as a proportionality coefficient between the radionuclide activity value and the image gray scale value, and the specific calculation process can be as follows:

(1) in the non-urination state, k may be calculated according to the first calculation formula.

The non-urination state is that the human body does not urinate after the radioactive nuclide is injected into the human body and before the PET/CT image or the PET image is shot.

The first calculation formula is:

wherein the content of the first and second substances,D₀is the initial activity value, lambda, of a radionuclide in the subject₁Is the self-radioactive decay coefficient of the radionuclide h₁Height of the subject's head cylinder model, h₂Is the trunk circle of the examineeHeight of cylinder model, h₃Height of the subject's leg cylinder model, h₄Height, h, of a heart cylinder model₅Height, R, of bladder cylinder model₁Is the radius, R, of a cylindrical model of the subject's head₂Is the equivalent radius of the torso cylinder model, R₃Radius of a cylindrical model of the subject's leg, R₄Radius, R, for a heart cylinder model₅Radius of the bladder cylinder model.

(2) In the urine-empty state, k is calculated according to the second calculation formula.

The state of urinary emptying refers to: after the human body is injected with the radioactive nuclide, the human body urinates before the PET/CT image or the PET image is shot.

The second calculation formula is:

wherein, among others,D₀is the initial activity value, lambda, of a radionuclide in the subject₁Is the self-radioactive decay coefficient of the radionuclide, lambda₂Is the coefficient of variation of the biological metabolism in the internal organs, t₁The time when the PET/CT image or the PET image is shot is timed according to the time when the radioactive elements are injected into the human body, k is a proportionality coefficient between the activity value of the radioactive nuclide and the gray value of the image, h₁Height of the subject's head cylinder model, h₂Height of the subject's torso cylinder model, h₃Height of the subject's leg cylinder model, h₄Height, R, for a heart cylinder model₁Is the radius, R, of a cylindrical model of the subject's head₂Is the equivalent radius of the torso cylinder model, R₃Radius of a cylindrical model of the subject's leg, R₄Is the radius of the heart cylinder model,representing the gray scale of the head cylinder model in the PET/CT image or the PET image,representing the gray scale of the voxel in the torso cylinder model on the PET/CT image or PET image,representing the gray scale of the voxel in the cardiac cylinder model on the PET/CT image or PET image,representing the gray scale of the micro-elements in the leg cylinder model on the PET/CT image or PET image.

The principle description of the first calculation formula and the second calculation formula described above will be described below.

In one example, the spatial-temporal distribution of ambient radiation dose rate prediction model is embodied in the form of:

the addition in the formula is represented by the above-mentioned "correspondence superposition". Wherein, omega is a correction factor, and M represents a prediction model of the spatial and temporal distribution of the surrounding radiation dose rate.

The derivation process of the model for solving the spatial and temporal distribution of the peripheral radiation dose rate corresponding to each cylinder model in the model is as follows:

referring to fig. 2 and 3, the cylinder model not covering the origin of the coordinate system can be moved to the origin of the coordinate system, and the coordinate position of a radiated point P in the surrounding space is also moved along with the movement of the cylinder model. Referring to fig. 3, after moving, the original radiating point P moves to point P ', and the integral of the point P' at the original position of the remaining cylinder model is equivalent to the integral of the point P at the original position.

The embodiment of the invention adopts a multi-step linear integral of 'point infinitesimal', a surface integral of 'line infinitesimal' and a cylindrical volume division form of 'surface infinitesimal'. The remarkable characteristic of the embodiment of the invention in method innovation is that the embodiment of the invention is derived by mathematical integration. The integration method adopted here is in the form of direct integration, or in the form of non-discretization integration. The integration is as follows:

first, a schematic diagram of "infinitesimal" on the line source is given, as shown in fig. 4. The radiation dose rate generated by a point-like radiation source at any point in space (assuming that the distance from the point-like radiation source is r) can be calculated by formula (1).

According to a typical gamma radiation dose calculation method published by Ganjiafu (scientific innovation and application 21 of 2017), the article gives an isotropic point source gamma dose rate calculation formula:

in the above formula, a is the activity of a certain point-like source, i.e. the aforementioned time variation model, and the unit is Bq;is the gamma dose rate at a distance R from the point source, and has the unit of Gy/h; gamma is the gamma constant of the corresponding radioactive nuclide in Gy.m²V (h.bq); r is the distance from the point source in m.

For the definition of the f constant: the f constant of a radioisotope represents the dose rate (R/h) caused by unshielded gamma rays released from a 1mCi point source at 1cm from the source. The f constant is divided into a differential f constant and a total f constant. For a certain monoenergetic gamma ray of a given radioisotope, the f constant used for the calculation is the differential f constant, in terms of f_iRepresents; the total f constant, abbreviated to f constant, of radioactive isotopes is equal to f_iAnd (4) summing.

The above equation can be simplified as:

secondly, on the basis of finishing the line integration, the area division calculation on the thin plane ABCD is carried out on the line infinitesimal EF. As shown in fig. 5.

On the basis of finishing the above surface integral, the volume fraction calculation of the cylinder is carried out on the surface element ABCD. As shown in fig. 6.

.

Taking the solution of the head part of the spatial and temporal distribution of the peripheral radiation dose rate corresponding to the head cylinder model as an example, the integral of the point P is specifically introduced for the cylinder model.

Referring to FIG. 7, let the distance from EF to PH be h_FI.e., FH distance.

Let the included angle between EF and PF be theta₁The angle between the extension line of FE and PE is theta₂Let the angle between FN and NP be θ.

(1) Head line integral:

(line integration on the Z axis, multiplied by dz)

Wherein D₀、Г_δT and lambda are constants, gamma_δRepresenting the gamma constant, t, of the corresponding radionuclide of the infinitesimal delta₁Denotes a time when the PET/CT image or the PET image is captured, measured as a time when the radioactive element is injected into the human body, t denotes a time measured from the time when the PET/CT image or the PET image is captured, λ denotes an attenuation coefficient of the radioactive element,representing the gray scale of the micro-elements in the PET/CT image or the head cylinder model on the PET image, e^-λtThe radioactive decay is shown in relation to time, and r is the distance from a point infinitesimal to a certain point P in the external space.

The included angle between the connecting line from the point infinitesimal to the point P and the parallel line of the Z axis is theta, the vertical line of the point infinitesimal intersects with AD and BC at E, F points respectively, and thenAndthe included angle is theta₂，Andthe included angle is theta₁。Has a height of h_P，Has a length of h_F。

Is provided withIs of a height of h, is,

with reference to figure 8 of the drawings,

m²＝x²+H_p ² (5)

with reference to figure 9 of the drawings,

when h is generated_pWhen-h is greater than 0,

when h is generated_pWhen-h is less than 0,then

Therefore, the temperature of the molten metal is controlled,

(2) vertical thin planar area integral of head:

with reference to figure 7 of the drawings,

(3) the head part is divided into:

the volume of the right half cylinder is divided into:

referring to FIG. 10, the line connecting dx and dot O forms an angle with the Y axis∠COQ＝β，

l＝Rcosβ

Since x > 0, y > 0,

then the right half cylinder for the portion y > 0 expresses the P radiation dose rate by G_{Right side}Represents:

referring to fig. 11, the left half cylinder has a volume:

when x is more than 0 and y is less than 0,

the left half cylinder volume is divided into:

thus, the expression of the dose rate of the cylinder for P radiation, with G_{Left side of}Represents:

therefore, the calculation of the spatial and temporal distribution of the peripheral radiation dose rate corresponding to the head cylinder model is completed, the calculation principle of the spatial and temporal distribution of the peripheral radiation dose rate corresponding to other cylinder models (the heart cylinder model, the leg left leg cylinder model, the right leg cylinder model, the shoulder bladder cylinder model and the trunk cylinder model) is the same as the spatial and temporal distribution of the peripheral radiation dose rate corresponding to the head cylinder model, and the calculation principle is not the same as the spatial and temporal distribution of the peripheral radiation dose rate corresponding to the head cylinder model, but the cylinder model parameters (such as the height and the radius of the cylinder model), the physical parameters (such as the gray scale) and the included angle related to the point P in the integration process are different.

It should be noted that, because the central axes of the heart cylinder model, the leg left leg cylinder model and the leg right leg cylinder model do not coincide with the Z coordinate axis, the heart cylinder model, the leg left leg cylinder model and the leg cylinder model need to be moved to make the central axes coincide with the Z coordinate axis, and the specific moving manner can be seen in fig. 3, that is, the heart cylinder model and the leg cylinder model whose central axes do not coincide with the Z coordinate axis are moved to the position coinciding with the Z coordinate axis, during the moving process, the point P is also moved to a point P ', at which point P ' corresponds to P, and then the peripheral radiation dose rate space-time distribution corresponding to the heart cylinder model and the leg cylinder model is calculated by the same method as the calculation principle of the peripheral radiation dose rate space-time distribution corresponding to the head cylinder model for the point P ', and no matter is the cylinder model parameters (such as the height of the cylinder model, the length, and the length of the cylinder model length, Radius), physical parameters (e.g., gray value size), and the angle associated with point P during integration.

It should be noted that, in calculating the radiation dose rate around the subject, since each person is about physiologically metabolized, t is the ratio₁(in practice, the time value can be fixed) detection of the moment, and t is respectively made for the first 5 persons₁In addition to the PET or PET _ CT image, the subsequent evidence of the radiation dose rate around the person is given as t₁Fixed, no further detection is required to do t₁The first 5 persons t, in particular₁After the PET or PET _ CT gray levels are obtained, the respective k values are calculated, and in other applications, the k values of the first 5 people are averaged to be used as k in other applications, of course, t is made for the front₁The more people are detected at any moment, the more accurate the application of the k value obtained by averaging to the later detection and analysis of the evidence of the radiation dose rate around the people is. Based on the estimation, t was previously performed on the first 5 people₁The PET or PET _ CT detection of the moment in time is sufficient. T may not be done for the person after 6₁PET or PET _ CT gray scale detection.

In one example, the gray scale of the infinitesimal in any one cylinder model is the average gray scale of the PET/CT image or the human body structure unit corresponding to the cylinder model on the PET image. For example, the gray scale of the infinitesimal in the head cylinder is the average gray scale of the head on the PET/CT image or the PET image; the gray scale of the infinitesimal in the trunk cylinder model is the average gray scale of the trunk on the PET/CT image or the PET image; the gray scale of the infinitesimal element in the heart cylindrical model is the average gray scale of the heart on the PET/CT image or the PET image, and so on, which is not described in detail.

In one example, in the process of building the prediction model of the spatial and temporal distribution of the ambient radiation dose rate, the equivalent radius of the trunk cylinder model is also required to be obtained. The specific calculation method may be as follows:

according toCalculating the equivalent radius R of the trunk cylinder model₂Wherein Mg is the weight of the human body, H is the height of the human body, V is the volume of the human body, H₁Height h of human head₂Height h of human body₃Is the height, R, of the human leg₁Radius of human head, R₃Is the radius of the leg of the human body, and rho is the average density of the human body.

The volume of the body involved in the above formula can be determined by the body completely entering the water.

Except the equivalent radius of the trunk cylinder model in the formula, other parameters can be obtained through actual measurement.

The above formula is a calculation template for calculating the equivalent radius of the trunk cylinder model, and when the spatial and temporal distribution of the peripheral radiation dose rate of a specific examined person is predicted, specific values of other parameters can be substituted, and the equivalent radius of the trunk cylinder model of the examined person is calculated on site.

In other embodiments of the present invention, the prediction model of spatial and temporal distribution of ambient radiation dose rate may further include a dose rate modification factor, and the dose rate modification factor is used to modify the prediction model of spatial and temporal distribution.

Assuming that F (t, d) represents the spatial-temporal distribution prediction model of the ambient radiation dose rate and ω represents the dose rate modification factor, the modified spatial-temporal distribution prediction model of the ambient radiation dose rate is F' (t, d) ═ F (t, d) + ω.

The dose rate modification factor may be determined from actual measurements of the spatial and temporal distribution of the ambient radiation dose rate, as will be described in more detail later herein.

The following describes a more detailed construction of the prediction model of the spatial-temporal distribution of the ambient radiation dose rate, which may include the following stages:

firstly, establishing a corresponding relation between the human body geometric parameters and the cylinder model.

The radioactivity of each part and organ of human body can be regarded as uniform and equivalent, the same coordinate system is established for different parts of human body in one space, and the integration of the same cylinder model is completed on three layers of point infinitesimal, line infinitesimal and surface infinitesimal. Therefore, the uniform cylindrical structure is regarded as the prototype of physical model of each part and organ of human body.

For the examinee, the geometric parameters of the human body, such as the height, the weight, the head size, the chest size, the sizes of the legs, the brain size, the heart size, the bladder size, the human body mass, the body density and the like, of the human body are required to have a one-to-one correspondence in the human body 'cylinder' model, and the basic requirements of unchanged height and weight average of the human body are required to be met. Therefore, a fit relation between the human body geometric parameters of the examinee and the cylindrical model needs to be established, and a physical model matching the human body geometric parameters and the cylindrical model needs to be established. If the two can not be matched or the difference is large, the problems of the human body of the examinee and the distribution of the radioactive nuclide in the human body in reality are difficult to simulate.

The establishment of the corresponding relationship between the human body geometric parameters and the cylinder model specifically comprises the following processes:

(1) superposition of cylinders

According to the conditions of age, sex, standing posture and the like in the human body size (GB10000-88) of Chinese adults, the human body geometric parameters of a detected person are converted into a physical model of human body 'cylinder superposition', and the detected person and the human body 'cylinder superposition' model have the following peer-to-peer relationship, and the specific content is as follows:

firstly, the height is not changed; the body weight is not changed; the longitudinal height of the head and the neck is not changed; fourthly, the longitudinal height of the trunk is not changed; the height of the leg part is not changed; sixthly, the average diameter of the head part on the horizontal plane is unchanged; keeping the average diameter of the trunk on the horizontal plane unchanged; two legs become cylindrical and the diameters of the cylinders at different heights are equal; ninthly, taking the standing posture of the human body as a standard, and taking the density of the head, the trunk (including upper limbs) and the two legs as a constant; the position parameters of all organs of the human body in the R are almost unchanged in the human body and the physical model. The human body geometric parameters and the cylindrical body model (standing state) of the examinee are shown in fig. 2 a.

The method for determining the equivalent radius of the trunk cylinder model can be found in the above description, and is not described herein again.

(2) And superposing the human body cylinders in the same coordinate system.

When the spatial-temporal distribution of the radiation dose rate around the examinee is calculated, the calculation of any part in the examinee needs to be carried out in the same coordinate system. Therefore, the human body cylindrical models can be superposed under the same coordinate system.

In one example, an O point with the center of the lower surface of the bladder cylinder as a cylindrical coordinate may be established, and a line connecting the O point with the center of the lower surface of the human head cylinder model as a Z axis is used to make a coordinate line of distance and angle on a vertical horizontal plane of O O'. As shown in fig. 2 b.

Establishing an internal relation between the PET/CT or PET image gray value and the radioactivity of the corresponding part.

In the case of PET/CT or PET examinations, the nuclear medicine staff injects the examined person¹⁸F-FDG drugs. The value of radioactivity to be injected depends mainly on the actual parameters such as the weight of the subject.

As can be seen from FIG. 12, at the beginning of the radiopharmaceutical injection,¹⁸F-FDG is distributed mainly in the heart and in one large vessel. Over time, approximately at the time of injection¹⁸The 30 th second after F-FDG,¹⁸F-FDG spreads almost to all parts of the human body. At around 350 seconds after injection of the drug,¹⁸the distribution of F-FDG is mainly concentrated in four parts of the brain, heart, tumor part and bladder, and a PET image of the human body at a of fig. 13 can be formed. If there is no tumor in the subject's body,¹⁸F-FDG is mainly distributed in brain, heart and bladderOf these three parts, and of other parts of the body¹⁸The F-FDG can be considered as a uniform distribution, as in the image after 360 seconds in fig. 12.

Radiopharmaceutical agents¹⁸In a subject, F-FDG has radioactive decay, and also has biological metabolism and're-diffusion distribution' among organs, namely the pharmacokinetics problem in a human body. Therefore, it is proposed to establish¹⁸The intrinsic relationship between the total radioactivity of F-FDG in the initial stage of the body and the sum of the specific radioactivity in each site after diffusion must be considered and the biological metabolism and radioactive decay corrected. Based on the one-to-one correspondence between the specific radioactivity of each part in the subject and the gray-scale values of the corresponding part in the PET/CT or PET image at that time (or at approximately that time), an equation or an equal ratio mathematical expression between them can be established. This is the basic idea and working principle to solve the problem.

Specifically, taking the human PET image shown in fig. 13 as an example, the image at B can be regarded as a schematic radioactivity ratio corresponding to the PET grayscale image at a according to the equivalent principle of the radiopharmaceutical distribution (the small change amount of radioactive decay can be disregarded at the moment of imaging). Similarly, the image at D can be regarded as a radioactivity diagram corresponding to the PET gray level image at C; the image at F can be regarded as a radioactivity map corresponding to the PET gray scale image at E.

As can be seen from FIG. 13, the imaging times for the two PET images at C, E were 1770sec-1800sec, 3480sec-3600sec, respectively, after the radiopharmaceutical injection.

Here, the specific activity values of various parts of the human body at B, D, F are set. It is assumed that the subject only performs PET-CT/PET detection of myocardial conditions, and there is no radiopharmaceutical accumulation at the tumor as shown in FIG. 8. Under the premise, taking D, F as an example of the graph of the specific activity of each part in the body, the head specific activity value is set as a₁Setting the value of specific activity of body radioactivity to be a₂Setting the heart specific activity value as a₃Setting the bladder specific activity value as a₄Setting the specific activity value of the two legs as a₅。

In order to establish the internal relationship between the gray value of the PET/CT or PET image of the examinee and the specific activity of the corresponding part, the injection into the body is set¹⁸F-FDG initial Activity value D₀Bq, is provided with¹⁸F-FDG has a self radioactive decay coefficient ofThe coefficient of variation of the biological metabolism in a certain organ in vivo is(except for bladder). For the bladder interior due to the particularities of bladder function¹⁸F-FDG, taking into account only its physical radioactive decay and not taking into account¹⁸Biological metabolism of F-FDG in the bladder. Here, the heart and bladder were also modeled as "cylinders", with the heart "cylinder" radius being set at R₄Height of h₄(ii) a Setting the radius of the bladder 'column' as R₅Height of h₅. And simultaneously, the proportionality coefficient between the radionuclide activity value and the image gray value is assumed to be k. And according to the human body columnar superposition model, establishing a physical model and a mathematical expression of the specific activity change in the body of the detected person, and further obtaining the time change model.

In practical scenarios, the subject may be in different physiological states, such as a state of voiding urine (or referred to as a urination state), a non-urination state.

The principle of the first calculation formula and the second calculation formula of the gray level radioactivity ratio relation k is as follows:

the physical model and mathematical expression of the change of specific activity in the body of the subject under the condition that the patient does not urinate are as follows:

under the condition of urination of a patient, the physical model and the mathematical expression of the specific activity change in the body of the subject are as follows:

in the above formula, the parameters other than the k parameter are known.

From the above equations (6) and (7), the first calculation formula and the second calculation formula can be derived:

wherein the content of the first and second substances,

for the volumes of the heart and bladder referred to in the above formula, it can be obtained according to the following way:

the heart of a person is similar to the size of the fist of the person, and the volume V of the heart can be obtained by putting the hand of the person into a beaker filled with water_heart(ii) a The volume V of the bladder can be calculated through the normal urine output of the individual_Bladder. Thus, the following two equations can be listed:

and thirdly, correcting the space-time distribution of the peripheral radiation dose rate of the human body model.

The foregoing mentions the use of a dose rate modification factor for modifying the spatiotemporal distribution prediction model, which may be determined from actual measurements of the spatial and temporal distribution of the ambient radiation dose rate.

Specifically, taking the nuclear medicine department of the Beijing Anzhen Hospital or the Beijing university tumor Hospital affiliated to the capital medical university as a radiation dose rate actual measurement place, in their waiting room or ward, the radiation dose rate is measured by using a corrected FH40G gamma dose rate meter, the measured radiation dose rate result is compared with the calculated value of the prediction model, and then the dose rate correction factor omega in the prediction model is corrected.

Based on the above techniques, a software system of the radiation dose rate distribution around a PET-CT or PET subject can be designed to implement the above determination method. The software system is developed by adopting C + + language under a Windows operating system.

The software system mainly relates to the rapid construction of the activity space of a detected person (mainly relating to the construction of three-dimensional spaces of waiting rooms and wards), the interactive construction of a physical model of human body ' cylinder superposition ', the triple calculation (including the integral calculation of three layers of ' point infinitesimal ', line infinitesimal ' and ' surface infinitesimal ') based on a cylinder as a core, the triple volume division superposition calculation of a plurality of cylinders under the same coordinate and the like. In addition, the visualization technology is utilized to convert the calculation result into visual two-dimensional and three-dimensional visualization results, and the staff is effectively helped to analyze and master the distribution condition of the radiation dose rate in the waiting room or ward.

Embodiments of the present invention further provide a system for determining a radiation dose rate around a nuclear medical subject, please refer to fig. 14, which exemplarily includes:

a data acquisition module 1401, configured to acquire a human body model parameter of a subject and a gray scale value of a target image; the target image comprises a PET/CT image or a PET image of the subject;

a peripheral radiation spatial-temporal distribution determination module 1402, configured to determine, according to the human body model parameter of the subject and the gray value, a spatial-temporal distribution of the peripheral radiation dose rate of the subject using a peripheral radiation dose rate spatial-temporal distribution prediction model; the prediction model of the spatial-temporal distribution of the ambient radiation dose rate is determined according to a gray level radioactivity relation and a human body model, wherein the gray level radioactivity relation comprises the relation between gray levels and corresponding human body structure unit radioactivity.

In one example, the functions of the data acquisition module 1401 and the ambient radiation spatiotemporal distribution determination module 1402 may be implemented in computer software, i.e. a computer at least implements acquiring target images and subject phantom parameters by running software, and determining the radiation dose rate spatiotemporal distribution around the subject using a predictive model.

In addition, the data obtaining module 1401 and the ambient radiation spatio-temporal distribution determining module 1402 may also be implemented in a hardware form, for example, the ambient radiation spatio-temporal distribution determining module 1402 may be a controller/processor of a computer device, and the data obtaining module 1401 may be an input/output interface of the computer device.

The controller/processor may load program code to obtain the target image and the phantom parameters of the subject via the input output interface and determine a spatial and temporal distribution of radiation dose rates around the subject using the predictive model.

Alternatively, the data acquisition module 1401 may include: the device comprises an input/output interface, an image acquisition device and a gray value processing device.

The input and output interface is used for receiving input human model parameters, and the gray value processing device is used for processing the target image acquired by the image acquisition device into a gray map and acquiring a gray value.

Further, the image acquiring device may be specifically a data transmission interface connected with the PET/CT apparatus or the PET apparatus, and may acquire the target image from the PET/CT apparatus or the PET apparatus.

In other embodiments of the present invention, the radiation dose rate determination system around the nuclear medical subject in all the above embodiments may further include: the device comprises a prediction model building module and a human body model building module.

The prediction model construction module is used for carrying out volume integration on the radiation dose rate of the micro element in any cylinder model to the same space position outside the human body model according to the relation between radioactive decay and time, the gray level radioactivity relation and the gray level of the micro element in any cylinder model so as to obtain the space-time distribution of the peripheral radiation dose rate of any cylinder model; and correspondingly superposing the spatial and temporal distribution of the peripheral radiation dose rate of each cylinder model to obtain the spatial and temporal distribution prediction model of the peripheral radiation dose rate.

The human body model building module is used for building a human body model; the human body model comprises a plurality of cylinder models, any cylinder model is used for representing a structural unit of a human body, and the parameters of the human body model comprise the size of each cylinder model.

Similar to the data acquisition module 1401 and the ambient radiation spatio-temporal distribution determination module 1402, the functions of the prediction model construction module and the human body model construction module may be implemented in the form of computer software or hardware.

When implemented in hardware, for example, the prediction model building module and the human body model building module may be respectively independent computer devices, and may also be hardware devices, such as a controller/processor, of the prediction model building and the human body model building, which are provided in the computer devices.

For the specific ways of constructing the prediction model and the human body model, please refer to the above description, which is not repeated herein.

In other embodiments of the present invention, the model for predicting the spatial and temporal distribution of the ambient radiation dose rate in all the embodiments may further include a dose rate modification factor, where the dose rate modification factor is determined by an actual measurement value of the spatial and temporal distribution of the ambient radiation dose rate. The prediction model can be modified by the prediction model construction module by using the dose rate modification factor to obtain a modified prediction model.

For a detailed description, refer to the above description, and are not repeated herein.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

The principle and implementation of the embodiments of the present invention are explained in the present text by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core idea of the embodiments of the present invention; meanwhile, for a person skilled in the art, the idea of the embodiment of the present invention may be changed in the specific implementation and application scope. In view of the above, the present disclosure should not be construed as limiting the embodiments of the present invention.