KR20200015208A - Method for evaluating radiation internal dose and simulated phantom - Google Patents

Abstract

The present embodiments provide a method for evaluating a radiation internal exposure dose and a simulated phantom, which can shorten the time for evaluating the dose without causing additional radiation exposure to a patient. The method for evaluating the radiation internal exposure dose of the present invention comprises the following steps of: preparing the phantom; generating a source; and determining the radiation exposure dose of a second organ.

Description

Method for evaluating internal radiation dose and its simulated exposure {METHOD FOR EVALUATING RADIATION INTERNAL DOSE AND SIMULATED PHANTOM}

The present embodiments relate to an exposure dose evaluation method for evaluating internal exposure doses for each organ and a simulated exposure thereof.

Positron emission tomography combines radioactive isotopes that emit positrons to drugs, injects them into the patient's body, detects a pair of gamma rays generated by mobilizing the injected positrons with neighboring electrons, An imaging apparatus for obtaining a three-dimensional tomography image of the inside of the body by tracking the detection position of the.

 Positron emission tomography, unlike Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), can provide functional images of the human organs (with or without tumors), rather than anatomical images. In contrast to CT, which causes radiation exposure in humans, radiopharmaceuticals injected into the body can cause internal exposure in patients diagnosed with PET.

 Therefore, it is very important to accurately evaluate the internal exposure to patients during PET imaging because it can reduce unnecessary radiation exposure of PET diagnosis patients and reduce secondary side effects caused by radiation.

 For this reason, many research teams at home and abroad are conducting various studies to evaluate the internal exposure to patients during PET testing.

 The internal exposure assessment developed to date calculates the residual amount of radionuclide in the body and its internal exposure based on the type of intake nuclide, elapsed time after ingestion, metabolism in the body and a mathematical algorithm, but it is based on mathematical algorithm. In order to confirm the movement of the radioisotope injected into the human body, additional 3 ~ 4 PET images are required, and CT imaging is simultaneously performed due to the limitation of PET images that cannot show anatomical images. It causes unnecessary radiation exposure.

The present embodiments provide a method for evaluating exposure doses and mock exposures that can shorten the time for internal exposure dose assessment without causing additional radiation exposure to the patient.

In one aspect, the present embodiments provide a method of preparing a mock exposure body in which an organ is compartmentalized and voxelated to a predetermined size, and generating a point source located in a voxel inside a first organ designated as a source organ of the mock exposure body. Internal radiation dose assessment by radiation, comprising determining the radiation dose of the second organ due to the source generated in the first organ using the dose delivered to the second organ designated as the target organ of the simulated exposure Provide a method.

In another aspect, the present embodiments provide a simulated exposure system in which organs are compartmentalized and voxelized to a certain size, generating a point source located in a voxel inside a first organ which is designated as a source organ of the simulated exposure target. The dose delivered to the second organ designated as the target organ is used to provide a simulated exposure object used to determine the radiation dose of the second organ due to the source generated in the first organ.

The present embodiments may use computer simulated mock exposures to not cause additional radiation exposure to the patient.

In addition, the present embodiments can shorten the time for dose evaluation by not using a mathematical algorithm.

1 is a flowchart of a method for evaluating a radiation exposure dose according to an embodiment.
Figure 2 shows the process of calculating the circumference by the method using the Monte Carlo method.
3 illustrates a voxel-based three-dimensional object.
4 is a diagram illustrating a voxel-based simulation target.
5 illustrates the difference between a voxel-based simulation and a tetrahedral plane-based simulation.
6 shows the body of male (a) and female (b) mock subjects based on polygonal plane.
7 illustrates a polygonal plane-based mock exposure (a) and a tetrahedral plane-based mock exposure (b).
8 shows the internal organs and organ compartments of a tetrahedral based mock exposure.
FIG. 9 illustrates the voxelization to a size of 1 cm after compartmentalizing the organs of the simulated object.
10 shows a sailor organ (for example liver) implemented through this embodiment.
FIG. 11 shows the absorbed dose results of target organs (eg lung, gonad, chest, and small intestine) exposed due to ⁶⁰ Co generated in source organs (eg liver).

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

In addition, in describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only to distinguish the components from other components, and the terms are not limited in nature, order, order or number of the components. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but between components It will be understood that the elements may be "interposed" or each component may be "connected", "coupled" or "connected" through other components.

In order to solve the above problems, the present invention proposes a new internal exposure dose evaluation method for evaluating the internal radiation dose of the PET diagnosis patients in accordance with the standard body shape, location and size of the internal organs of the Korean people.

1 is a flowchart of a method for evaluating a radiation exposure dose according to an embodiment.

Referring to FIG. 1, the method 100 for estimating the radiation exposure dose according to an embodiment of the present invention includes preparing a mock exposure body in which an organ is compartmentalized and the organ is voxelized to a predetermined size (S110). Generating a source at the voxel internal point source of the first organ designated as (S120) and using the dose delivered to the second organ designated as the target organ of the mock bomber due to the source generated at the first organ. Determining two long-term radiation exposure dose (S130).

The simulated subject may refer to an object that is used for a dosimetry experiment or calculation by simulating a human body exposed to radiation. The radiation exposure dose is a physical quantity representing the intensity of the radiation field and may be expressed as renten (R). One lengen (R) is the dosage that produces a charge of 2.58 × 10 ⁻⁴ C per kg of air.

The radiation exposure dose may be a radiation exposure dose by positron emission tomography. In the following description, the radiation exposure dose by positron emission tomography is evaluated. However, radiation exposure by various methods capable of generating a source in the first organ of the simulated object and measuring the radiation exposure dose in the second organ Dose can be assessed.

Organs can be voxelized into various shapes such as hexahedral, triangular prism, conical and spherical. For example, organs may be voxelized into two or more hexahedral shapes. The organs are voxelized into a cube shape so that the voxels evenly generate the source throughout.

Meanwhile, in step S130 of generating a source, a source may be generated at a voxel center point of a first organ designated as a source organ.

 For example, the method 100 for estimating the radiation exposure dose according to an embodiment is a new method for evaluating the internal exposure dose using a mock simulation object using a computer simulation model of Monte Carlo simulation and a standard Korean without an additional mathematical algorithm.

The Monte Carlo method reproduces probabilistic natural phenomena through random number generation, and was developed as part of the Manhattan Project in 1940 in Los Alamos, USA. The Monte Carlo method uses circumferential calculations as an example. Can be.

As shown in FIG. 2, when sampling a point (x, y) in a 1 × 1 region, it is possible to calculate whether the distance from the collected point to the center (0, 0) is smaller than the radius 1 of the circle. By increasing the number of trials, the ratio of the number of points in the circle to the number of points outside the circle can be 4 / π. As shown in FIG. 2, when the number of trials is small, the error is large, but as the number of trials increases, the circumference converges to 3.14.

Monte Carlo simulations are reported to be the most accurate method for the analysis of radiation transport because the interaction between radiation and medium is calculated by particle and reflected in the result as the reaction between radiation and medium. Monte Carlo simulations include a variety of tools, including MCNPX (Monte Carlo N Particle eXtended), Geant4 (Geometry And Tracking), and EGSnrc (NRC`s Electron Gamma Shower). For example, the Monte Carlo simulation tool can use the Geant4 toolkit.

The computer-aided doll simulation phantom (phantom) described above refers to a virtual human model used in a computer, and is used in various fields such as dose calculation and simulation. Computer simulation doll mock bombs have been continuously developed in the 1950s from simple models such as cylinders and spheres to 4D phantoms that take into account the movement of the human body. This continuous development may mean that the maternal phantom plays a pivotal role in assessing human exposure to radiation.

In the method for evaluating the dose of radiation exposure 100 according to an embodiment, the computer-aided dummy simulation object for a mother is compartmentalized and voxelized to a predetermined size. As described above, as an example, as illustrated in FIG. 3, a voxel is a cube having a horizontal, a vertical, and a height, and a three-dimensional object may be defined through a set of cubes. 4 is a diagram illustrating a voxel-based mock exposure body. In FIG. 4, (a) shows an object, (b) and (c) are cross-sectional photographs of the front and side surfaces of a voxel-based mock exposure, and (d) is a plan view of a mock-based mock exposure. .

However, the voxel-based mock bombs based on voxels have a fixed voxel resolution that allows maximum description of human organs. 5 illustrates the difference between a voxel-based simulation and a tetrahedral plane-based simulation. Such voxel resolution may represent the closed curved surface of the organ as shown in FIG. 5, or may not accurately represent an extremely thin organ having a large hole and a thickness of several micrometers.

Therefore, in order to overcome the limitations of the voxel-based mock-up, a polygon-based mock-up that can accurately represent very thin organs and tissues by converting them to polygons and nubs faces has been developed.

6 shows the body of male (a) and female (b) mock subjects based on polygonal plane.

As can be seen from FIG. 6 and Table 1, the body index of male and female mock subjects can be produced based on the body index data of a specific national standard, for example, the standard Korean. Mock bombs can also be constructed based on standard body index data from other countries.

The disadvantage of the polygon plane-based simulation is that it takes a long time to calculate through Monte Carlo simulation. In order to overcome the shortcomings of the polygonal plane-based mock exposure, the radiation exposure dose estimation method 100 according to an embodiment is a polygonal plane-based mock exposure while maintaining the appearance of the polygonal plane-based mock exposure as it is. It can be used to evaluate the exposure dose through the tetrahedral plane-based simulation that overcomes the limitations of the calculation time of the simulation.

In FIG. 7, (a) illustrates a polygonal plane-based mock exposure, and (b) illustrates a tetrahedral plane-based mock exposure. FIG. 8 illustrates tetrahedral surface based simulated internal organs and organ compartments.

For the method 100 for estimating the radiation exposure dose according to an embodiment, the target organ exposed to the source organ and the source organ in which the radiopharmaceutical is accumulated after the intake of the radiopharmaceutical among the internal organs shown in FIG. 8 are targeted. organ must be established.

 Therefore, the method for evaluating the radiation exposure dose 100 according to an embodiment comprises organizing the organs of the mock target in advance and setting the organ organs in which the radiopharmaceuticals are accumulated for each organ in advance, and then voxelizing them to a constant size, and at the center of the voxel. After the source is generated, the internal exposure dose can be assessed by evaluating the exposure dose of the target organs due to the source organs by collecting only the results of dose evaluation by the dotted source existing inside the organ.

The method 100 for estimating the radiation exposure dose according to an embodiment may shorten the time for dose assessment because there is no additional positron emission tomography, which does not cause unnecessary radiation exposure to the patient and no additional mathematical algorithm calculation is required.

Hereinafter, a specific embodiment of the method for evaluating the radiation exposure dose 100 according to the embodiment using the above-described simulated exposure object will be described, but the present invention is not limited thereto.

Example

Positron emission tomograpy (PET) can acquire physiological and functional images of the human body in three dimensions by ingesting radiopharmaceuticals that emit positrons, but are accompanied by internal exposure due to ingested radiopharmaceuticals. Since ingested radiopharmaceuticals are accumulated in the internal organs of the human body, the integrated radiopharmaceuticals deteriorate the function of surrounding tissues and cause lesions such as cancer, so calculation of the internal exposure of the patient is necessary.

Therefore, various research teams have been developing programs that can calculate the residual amount and internal exposure of nuclides based on the type of intake nucleus, elapsed time after ingestion, metabolism in the body, and mathematical algorithms.

However, the current commercialized program confirms the tendency of radiopharmaceuticals to be decomposed and exposed to organs based on the results of source and target organs calculated on the basis of compartment models and mathematical algorithms and PET images taken 3-4 times. Internal dose calculations are performed through dose assessments between source organs and target organs, which takes much time to calculate doses.

Therefore, the purpose of this embodiment is to use the internal exposure dose that can easily calculate the exposure dose of the PET diagnosis patient based on the pre-calculated internal exposure dose value using Monte Carlo simulation and the doll simulation using computer simulation without additional mathematical algorithm. It is to provide evaluation-based technology.

For internal exposure dose assessment, the source organs of organs where radiopharmaceuticals accumulate after ingestion of radiopharmaceuticals and the target organs that are exposed due to the source organs should be established. In this example, a tetrahedral surface-based standard Korean mock bomb developed at Hanyang University's Advanced Radiation Engineering Laboratory was used to establish the long-term source.

In this embodiment, in order to set the source organs in which the uniform radiopharmaceuticals are integrated, the organs of the mock subject are compartmentalized and voxelized to 1 cm in size as shown in FIG. 9. After that, assuming that a source occurs at the center of each voxel, the source organ is defined through a set of point sources that exist only inside the organ.

In this example, the absorbed dose of target organs (eg lung, gonad, chest and small intestine) exposed from defined source organs (eg liver) was evaluated and Geant4 Monte Carlo simulation was used for this. The calculated dose evaluation results of the source organs and target organs were compared and evaluated with the voxel phantom-based dose evaluation results used in the existing internal exposure dose assessment. The voxel-based simulation targets (phantoms) used in the present embodiment were Hanyang University. High Definition Reference Korean voxel phantom (HDRK-Man) developed in the Nuclear Engineering and Advanced Radiation Engineering Laboratory was used.

10 illustrates a sailor organ (for example liver) implemented through this embodiment.

As shown in Fig. 10, the sailor organ (for example, liver) was composed of a total of 4,500 point sources. The internal point sources of the sailor organs generated 1x10 ^{7 60} Co crews each, and it took about 20 minutes of computer simulation time for each point crew. FIG. 11 shows the absorbed or exposed dose results of target organs (eg lung, gonad, breast, and small intestine) exposed due to ⁶⁰ Co generated in source organs (eg liver).

As a result of dose assessment, the uniform dose of ⁶⁰ Co inside the organ organs delivered the highest doses to the organ organs and relatively high doses to the lungs, chest and small intestine close to the liver. In contrast, low doses were delivered to relatively distant and small gonads. Overall, the doses of source organs and target organs in tetrahedral phantoms were estimated to be up to 54% lower than those of phantom-based phantoms. Due to the fact that it is larger than the actual organs, it has delivered relatively high doses. Also, the difference in dose is caused by different computer simulation tools of voxel phantom and tetrahedral phantom.

This embodiment aims to develop a dose assessment based technique that can calculate the internal exposure of PET diagnosis patients without additional mathematical algorithms. As a result of the dose evaluation proposed in this example, absorbed doses of source organs and target organs similar to those of conventional dose assessments using voxel phantoms were obtained. If the dose evaluation method proposed in the phantom based phantom is applied to the whole human body and then the dose evaluation results by various radiopharmaceuticals are databased, the dose by the source where radiopharmaceuticals are accumulated after PET diagnosis Evaluation results can be selected from a database to facilitate easy and rapid internal exposure dose assessment.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may various modifications and changes without departing from the essential characteristics of the present invention. Embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention but to describe the scope of the technical spirit of the present invention by the embodiments.

S110: mock bomb preparation
S120: Generation of Sailors in Chapter 1
S130: Determination of the radiation exposure dose of the second long-term due to the source generated in the first long-term

Claims (12)

Preparing a mock subject in which an organ is compartmentalized and voxelized to a predetermined size;
Generating a source in a voxel of a first organ designated as a source organ of the mock exposure object; And
And determining the radiation exposure dose of the second organ due to the source generated in the first organ using the dose delivered to the second organ designated as the target organ of the simulated exposure target. The method of claim 1,
And the radiation exposure dose is a radiation exposure dose by positron emission tomography. The method of claim 1,
Wherein said organ is voxelized into two or more hexahedral shapes. The method of claim 3,
The method of evaluating the radiation exposure dose of the cube is a cube. The method of claim 1,
In generating the source,
And a radiation exposure dose evaluation method for generating a source at a voxel center point of the first organ designated as the source organ. The method of claim 1,
The method of simulating radiation exposure dose of the simulated exposure is a tetrahedral simulation. It is a simulated exposure system where organs are compartmentalized and voxel to a certain size.
The source is generated in the voxel of the first organ designated as the source organ of the mock exposure target, and the dose generated in the first organ using the dose delivered to the second organ designated as the target organ of the mock exposure target. A simulated exposure body used to determine the radiation dose of the second organ. The method of claim 7, wherein
And the radiation exposure dose is a radiation exposure dose by positron emission tomography. The method of claim 7, wherein
The organ is a mock exposure voxelized into two or more hexahedral shapes. The method of claim 9,
The hexahedron shape is a cube mock exposure. The method of claim 7, wherein
A simulated exposure target generating source at the voxel center point of the first organ designated as the source organ. The method of claim 7, wherein
The simulated subject is mock-substrate, characterized in that the tetrahedral base.

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