KR101623512B1 - Dose calculation method, Recording medium recorded Dose calculation program - Google Patents

Abstract

The present invention provides a radiation dose calculation method for evaluating patient doses for various general radiography and a patient dose calculation program for evaluating patient effective dose in general radiography to provide a history of each patient's radiation dose, And a computer-readable recording medium storing a radiation dose calculation program and a radiation dose calculation program for a general radiographic examination which minimize an exposure dose.

Description

[0001] The present invention relates to a radiation dose calculation method and a radiation dose calculation program,

The present invention relates to a method for measuring a patient dose, more precisely, by accurately measuring a patient dose in a general X-ray of a diagnostic radiography area, And a computer-readable recording medium recording a patient dose calculation program.

Radiology is an important tool in modern medicine to diagnose various diseases. Therefore, the scope of diagnostic radiology is varied and the number of patients is increasing year by year.

However, as the public interest in health promotion increases due to the improvement of living standards, the public's interest and concern about the risks and side effects of radiation exposure are increasing together with the increase of radiation dose due to frequent radiation examination in the medical field . This follows from recent studies and examples that even small amounts of radiation exposure can be harmful to humans.

Therefore, a series of efforts are being made to more actively reduce medical radiation doses. The goal is to accurately measure the radiation dose of medical radiation and to manage the individual dose of the patient, in order to prevent the excessive dose of radiation.

In order to effectively optimize the medical radiation exposure, it is necessary to accurately grasp the patient exposure dose at the time of X-ray photographing. Of course, many research institutes and countries are still studying and measuring radiation exposure.

However, it does not currently measure the individual patient's exposure, but only provides an estimate of the exposure.

Another example is to provide a method of calculating the patient dose in various ways during radiography. Examples of these methods include a direct radiation dose measurement method using a dose evaluation simulator, a computer simulation calculation method using a radiation transport program, and a method using a general radiography patient dose calculation program.

However, the above methods have the following problems.

When using the dose evaluation simulator, it is not possible to perform experiments on various combinations of test conditions such as the type of test, the shooting direction, the inspection range, the kVp, the filter thickness, and the distance between the focus and the patient. Expenses are being spent.

The method of using the radiation transport program is mainly performed using a radiation transport computer program using the Monte Carlo methodology. This not only requires a lot of computation time, but also requires expertise in the use code. Therefore, it is difficult for users who perform direct radiography to calculate dose of patient using Monte Carlo methodology.

In the method using the general radiography patient dose calculation program, several programs have been developed and used. For example, 'PCXMC', CALDose_X, and the like. However, existing dose calculation programs have some important limitations. That is, the methods use mathematical dose evaluation simulators of planar, cylindrical, conical, elliptical and spherical forms. Therefore, there are many limitations in simulating the anatomical shape of the human body, and the shape and position of the human body organs are greatly different. As a result, the results of the dose evaluation using the mathematical dose evaluation simulator may distort the actual radiation dose. In addition, it is not possible to evaluate the dose for all the organs and tissues proposed in the ICRP Recommendation 103, and it does not reflect this in effective dose calculation.

Therefore, it is necessary to develop a new general radiation dose calculation program which can overcome the limitations of the existing program and apply the newly developed dose evaluation methodology.

Korean Patent Publication No. 10-2010-0071593 (June 29, 2010)

It is an object of the present invention to provide a radiation dose calculation method capable of minimizing the error in the conventional X-ray imaging examination.

Another object of the present invention is to derive a radiation dose indirect calculation factor applied to the radiation dose calculation method and to use it for calculating the radiation dose.

It is a further object of the present invention to provide a method and apparatus for evaluating a patient dose using a long-term dose database and a radiation dose calculation method, Program.

Another object of the present invention is to make it possible to easily calculate an effective dose using an incident surface dose (ESD) or a dose area product (DAP) at the time of X-ray radiography.

According to an aspect of the present invention, there is provided a method of evaluating a patient, the method comprising: providing an examination condition for evaluating a patient dose according to general radiography using a database constructed in advance; And calculating the radiation dose in accordance with the inspection conditions using the following formula: < EMI ID = 1.0 >

[Formula 1]

Where FA is the filter thickness (mm Al), kVp is the tube voltage, mAs is the tube current, and FSD is the focus-patient distance (cm).

The distance between the focal point and the measuring instrument was 80 cm. The total filter thickness was 2.5, 4.5, 6.5, 8.5 mm Al and the tube voltage was 40 ~ Measure radiation dose by 10 kVp within the 140 kVp range.

In Equation (1), the exponent of the tube voltage is expressed by a quadratic function.

The radiation dose can be calculated by calculating Equation 2 in which the indirect radiation dose calculation factor NDD (k) is applied to Equation 1 above.

[Formula 2]

In this case, NDD (k) is the indirect radiation dose calculation factor according to the tube voltage (kVp) and the filter thickness (mmAl) of the general radiographic apparatus, mAs is the product of the tube current (mA) The distance between patients (m).

According to another aspect of the present invention, there is provided an inspection method, comprising: inspecting range input windows for inputting inspection type, photographing direction, image size, inspection condition, and filter thickness information; And a calculation window for calculating an effective dose using an incident surface dose (ESD) or a dose area product (DAP).

The effective dose can be obtained by Equation (3).

[Formula 3]

Here, the effective dose conversion factor refers to a value for evaluating the effective dose from the dose of the incident surface dose (ESD) or the dose area product (DAP).

The effective dose conversion factor is an effective dose conversion factor (E / ESD) based on the incident surface dose for each X-ray incidence direction for gender examination according to the International Radiation Protection Committee (ICRP) tissue weight for general radiography test; And effective dose conversion factor (E / DAP) by dose area multiplication.

The calculation window includes an incidence plane dose information input window, a dose area product information input window, a weight information input window, a dose and an effective information input window.

The dose evaluation simulation body used in the radiation dose calculation program is a dose evaluation simulation body such as an actual human body shape.

According to the present invention, a new radiation dose calculation formula is proposed in which the existing radiation dose calculation formula is improved. The proposed radiation dose formula derives NDD (k), which is the indirect dose calculation factor of general radiography equipment for tube voltage and filter thickness. As a result, the radiation dose can be easily calculated while reducing errors compared with the conventional method.

The present invention also proposes a general radiography patient dose program using a long term dose database and a radiation dose calculation formula. This program makes use of dose evaluation simulators and allows the evaluation of patient dose due to the specification of various examination ranges. It is also based on Windows, so it is easy to use without expert knowledge in related technology. In particular, the effective dose conversion factor is provided so that it can be easily derived from the incident surface dose and the dose area multiplication factor, so that it is possible to easily obtain the effective dose for evaluating how much the actual patient is exposed to the radiation.

FIGS. 1A to 1D are graphs showing changes in radiation dose according to tube voltage, variations in radiation dose according to tube current, changes in radiation dose according to distance, and changes in radiation dose according to filter thickness
FIGS. 2A to 2D are graphs comparing the radiation dose calculated by the radiation dose calculation formula according to the present invention and the result of the radiation dose calculated according to the conventional calculation methods to the measured radiation dose
FIG. 3 is a view showing an example of a patient dose calculation program to be used in general radiography according to the present invention

The present invention is to develop a dose management program (KDose calc) that can be used in a medical institution equipped with a general X-ray imaging apparatus. That is, the present invention provides a method for evaluating an effective dose of a patient by a general imaging test and a program for calculating a radiation dose of a patient due to a general imaging.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a radiation dose calculation method and a computer-readable recording medium on which a patient dose calculation program is recorded according to the present invention will be described in detail with reference to the accompanying drawings.

First, it is necessary to derive the necessary factors for the effective dose evaluation of the patient due to the general radiography test.

Factor derivation can be divided into factors affecting radiation dose and factors necessary for dose evaluation of final patient. These factors will be applied to the patient's dose management system in connection with the history management contents for patient dose input and patient dose management in general imaging tests.

First, the factors affecting the radiation dose are various. For this, the radiation dose unit, the dose factor, and the characteristics of the general radiography apparatus are examined.

First, it is the amount of radiation used for radiation protection purposes. The unit of radiation dose is radiation doses, absorbed doses, equivalent doses, effective doses, etc., and the radiation dose for the exposure dose evaluation is calculated. Each dose is expressed as follows.

Here, the weight (W _R ) required for the equivalent dose is a radiation weight of 1, regardless of the energy, and the radiation weight recommended by the International Commission on Radiation Protection (ICRP) is shown in Table 1. The tissue weights (W _T ) required for the effective dose are shown in [Table 2].

This is the radiation dose used in the second general shot. These include incident surface dose (ESD), incident surface air curtain (ESAK), incident air kerma (EAK), and dose area product (DAP). The incident surface dose is defined as the absorbed dose corresponding to the central region at the surface of the patient's entrance to and exiting from the radiographic examination, where the central region is the intersection of the central axis of the X-ray beam and the patient X- It says. The incidence plane air mass is the amount of radiation measured on the surface of a patient or on the surface of a tissue, and back scattering due to particle collision is considered. The incident air mass is a measure of the amount of radiation going into the air without the patient's influence and does not take into account the backscattering effect on the patient's surface. The dose area multiplication is the value obtained by multiplying the absorbed dose by the area of the corresponding cross-sectional area when the cross-section is cut perpendicular to the X-ray beam center axis to which the dose is applied.

It is a factor affecting the dose of the third patient. In order to calculate the radiation dose at the time of general radiography, it is necessary to derive the factors affecting the results. For example, the internal condition of the X-ray generating apparatus, general photographing apparatus, photographing conditions, and the like are applicable. Specifically, we examine the relationship between tube voltage (kVp), tube current time (mAs), filtration, collimator, focal plane distance (FFD) and focal plane distance (FSD) I have to see.

As another factor, it is a necessary factor for the dose evaluation of the final patient. [Table 3] [Table 3] [Table 3] < EMI ID = 16.1 >

Next, we will look at the methodology for evaluating patients' radiation dose according to general radiography.

First, it is necessary to select the measurement dose required for general radiography. In this embodiment, the incident air kerma (ESAK) using the ionization chamber of the general radiographic apparatus is selected as the measured dose.

And the selection of a measuring device. In order to measure the incident air kerma which was selected as the measurement dose, the measuring device was a measurement device of Radcal's 2026C dosimeter and the 60cc ionizer box.

And the measurement method. In order to measure incident air kerma, the ionization chamber was directly measured in the air passing through the x-ray beam to eliminate the effect of back scattering. In addition, various examination conditions will be presented in order to understand the changes in radiation dose due to changes in tube voltage, tube current, and total filter thickness during general radiography. This is shown in Table 4.

And we examined the radiation dose change according to these characteristics.

Changes in radiation dose were measured by varying the radiation dose according to the tube voltage, the radiation dose according to the tube current, the radiation dose according to the distance, and the radiation dose according to the filter thickness.

The measurement results are shown graphically in Fig. The radiation dose according to the tube voltage was measured according to the thickness of the filter for calculating the radiation dose according to the present invention. Measurement conditions were set as 2.5 (a), 4.5 (b), 6.5 (c) and 8.5 mm Al (d) as the total filter thickness The radiation dose was measured. In addition, as shown in FIG. 1B, in the measurement of the radiation dose according to the tube current, the focus-measuring period distance was 80 cm, the total filter thickness (intrinsic + addition) was 2.5 mm Al, tube voltage (kVp) was 60 kVp, , 5, 10, 20, 50, 100, and 200 mAs, respectively. Also, as shown in FIG. 1C, the radiation dose was measured by varying the length of the tube at 10 mAs, the tube voltage of 60 kVp, the total filter thickness of 2.5 mm Al, and the distance of 60-150 cm by 10 cm. Also, as shown in FIG. 1d, the radiation dose was measured according to a tube voltage of 40-150 kVp per 10 kVp according to an additional filter of 2, 4, 6 mm Al according to the filter voltage. The tube voltage is a: 50 kVp, b: 100 kVp, and c: 150 kVp.

In this way, the radiological characteristics of the radiographic equipment were examined.

Next, we will look at a methodology that can be applied to patient dose assessment using radiation transport computational methodology. It extracted and verified the methodology that simulates general photographic equipment, filters, and energy spectrum.

First, we will use the radiation transport computer code to calculate long term dose and effective dose.

And the energy spectrum is to simulate the X-ray at the time of general radiography using SRS 78. At this time, when the energy spectrum is sampled, the cathode material of the radiographer uses 100% tungsten (W).

In addition, a dose evaluation simulator is used to evaluate the patient dose.

Once the patient dose assessment methodology for general radiography has been determined, the patient's long-term dose database for each dose for the dose calculation program should be established.

The long term dose database shall be constructed by selecting general inspection conditions and inspection ranges for each type of inspection. Especially, total of 22 general radiographic examinations were selected considering the direction of examination such as AP, lateral (LAT), and oblique (OBL) directions for 15 test sites. This is summarized in [Table 5].

Also the tube voltage range for each test shall be specified.

That is, the tube voltage determines the energy of the x-ray generated in the general radiograph and the energy of the x-ray determines the transmittance to the human body. The higher the tube voltage, the greater the transmittance of the x-ray increases the longer-term dose in the human body. The lower the tube voltage, the lower the transmittance and the longer-term dose in the human body becomes lower than the higher tube voltage. Therefore, a database of patient doses by tube voltage should be established for the same test.

To this end, the database of patient doses according to the tube voltage was constructed using the maximum and minimum values of the tube voltage range and the average value of the tube voltage according to the domestic general radiography test, with reference to Table 6 after selecting the tube voltage range for each test.

The filter thickness range for each test should also be considered.

The filter is divided into intrinsic filtration, which is attenuated by the radiograph when the radiation is generated, and additional filtration, which is additionally inserted according to the purpose of the inspection. Table 7 lists the filter thicknesses per tube voltage recommended by the National Radiation Protection Board (NCRP).

In the present embodiment, the thickness of the total filter is selected based on this, that is, when the average tube voltage per examination is limited to domestic medical institutions, the total tube voltage is 50kVp or more. 3.5mm Al is selected. The thickness of the selected filters in the other ranges was 1, 2, 2.5, 3.5 mm Al and the database was constructed accordingly.

In addition, the database was constructed by limiting the scope of each test. The scope of inspection shall be based on the specifications of film and image plate applicable for each inspection. This is summarized in Table 8, which shows the specifications of the image plate (IP) selected for each general radiography test.

On the other hand, the patient dose can be evaluated using the database constructed as described above. For this reason, the method of evaluating the radiation dose for various examination conditions in general radiography will be described.

The radiation dose evaluation method is to know how much the radiation dose is investigated to the patient. In this case, since the examination conditions such as the tube voltage, the tube current, and the focus-patient distance are different according to the medical institution and the radiologist, This is to solve the problem.

First, we will briefly discuss existing methods for calculating radiation dose.

Radiation dose calculation methods include 'NDD-M (f) Calculation', 'Edmonds Calculation', 'Tung-Tsai Calculation', and 'Swiss Calculation'.

The NDD-M (f) calculation method uses the conversion factor for the tube voltage and the thickness of the filter, and presents the conversion factor according to the single-phase, three-phase, and inverter rectification methods. The Edmonds calculation, unlike other calculations, shows that the dose is proportional to 1.74 watts of tube voltage, and the total filter is also defined as not inversely proportional to the radiation dose plus 0.114 in inverse proportion. This calculation does not include the backscattering dose and it calculates the radiation dose to the air. The Tung-Tsai calculation uses the Rando dosimetry simulator and the TLD dosimeter to calculate the radiation dose and includes the backscatter dose. And the calculation method of Switzerland is the calculation method developed through the data and measurements provided by the Radiation Union of Switzerland and does not include the backscattering dose.

The NDD-M (f) calculation method showed the most similar result among the above-mentioned calculation methods by measuring the radiation dose according to the tube voltage and the filter thickness.

However, in the above NDD-M (f) calculation method, it has been confirmed that the radiation dose change according to the tube voltage change is different from the measured radiation dose variation, and an error of more than 10% occurs according to the tube voltage interval.

On the other hand, the present embodiment reduces the error generated in the above-described NDD-M (f) calculation method by providing Equation 1 below.

Where FA is the filter thickness (mm Al), kVp is the tube voltage, mAs is the tube current, and FSD is the focus-patient distance (cm). In Equation (1), the exponent of the tube voltage is expressed by a quadratic function rather than a constant considering the influence of the tube voltage varying depending on the filter thickness.

FIG. 2 shows the results of the calculation of the new method according to the above formula (1) and the above-described conventional calculation methods, namely, the NDD-M (f) calculation method, the Edmonds calculation method, the Tung- Tsai calculation method, The results of the calculated radiation doses were compared with measured radiation doses and plotted. It can be seen that the result of Equation 1 is the closest to the measured radiation dose.

On the other hand, in the case of Equation (1), since the calculation method is complicated, it is difficult to derive the result.

For this, the present embodiment obtains Equation 2 by applying the indirect radiation dose calculation factor NDD (k) of the general radiography equipment to the tube voltage and the filter thickness. Equation (2) also calculates the amount of radiation to the air without back scattering as a calculation of incident air kerma. Y

Here, NDD (k) is an indirect radiation dose calculation factor according to the tube voltage (kVp) and the filter thickness (mmAl) of a general radiography apparatus, mAs is a product of tube current (mA) (M) between the patient and the patient.

The NDD (k) is provided as shown in Table 9 below. NDD (k) in Table 9 is the value in an x-ray generator using a three-phase rectification scheme. Of course, the inverter rectification method increases the radiation dose by about 5% compared to the three-phase rectification method, and the radiation amount of about 60% is emitted by the single-phase rectification method.

Next, a program for calculating a radiation dose of a patient due to a general radiography according to the present embodiment will be described using the above-described long term dose database and indirect radiation dose calculation formula.

Prior to this, we will look at the existing radiation dose calculation program.

Existing radiation dose calculation programs include PCXMC and CalDose_X.

PCXMC is a program for calculating the patient's long-term dose and effective dose in general radiography. However, in the above-mentioned PCXMC, since the simulated body used for dose calculation is a mathematical dose evaluation simulator, an error may occur in estimating the radiation dose because the body shape and position are different from each other and the body is a hermaphroditic body. In addition, all of the information presented to evaluate patient doses do not include back scatter factors, and further information on back scatter factors is needed to evaluate patient doses.

CalDose_X is also a program for calculating long-term dose and effective dose for patients during general radiography. CALDose_X uses the long term dose conversion factor established for general radiography, unlike PCXMC. However, the established long - term dose conversion factor is about one test range for each test and there is a disadvantage that various test ranges can not be set for each test. In addition, there is a disadvantage that only a partial range can be applied to each test for the inspection condition.

On the other hand, the radiation dose calculation program proposed by the present embodiment uses a dose evaluation simulator developed on the basis of a human body image to solve the problems of PCXMC and CalDose_X, and it is possible to build a database of thousands of patients, Respectively.

A program for calculating the patient's exposure dose in a general imaging test is shown in FIG. 3 is a view showing a patient dose calculation program to be used in general radiography according to the present invention.

The patient dose calculation program 100 shown in the figure is developed using Microsoft Visual Studio 2010 for Windows application development.

Also, by applying the long term dose database described above, patient doses can be calculated according to 3 to 5 image sizes for 22 examinations considering the type of examination and the direction of imaging. The 3 to 5 image sizes for each test include the average image size, optimal image size, and maximum image size that can be used for the test, so that various patient dose can be evaluated according to the purpose.

These image sizes for each test can be easily selected with the mouse through the upper left test type of the program. That is, the inspection range can be selected by selecting the inspection type, the photographing direction, and the image size by operating the reference numeral 102 in FIG.

On the other hand, the patient dose calculation program 100 provides the following technical features.

First, since the radiation dose is calculated using the dose evaluation simulator like the actual human body shape, a more accurate dose value can be provided than the conventional calculation program. Secondly, dose evaluation is possible for each adult male and female. Third, both ICRP 60 and ICRP 103 effective dose assessment methodologies are applicable. Fourth, it is applicable to various shooting conditions, that is, kind of inspection, kVp, mAs, and the like. Fifth, even without expertise such as radiation transport theory is available.

On the other hand, the effective dose used in the patient dose calculation program is usually calculated by the following equation (3).

Where W _T is the tissue weight, W _R is the radiation weight, H _T is the equivalent dose, and D _{T · R} is the average absorbed dose for the tissue.

The tissue weights for calculating the effective dose are summarized in Table 10 below.

However, in this embodiment, the effective dose can be easily obtained by using the patient dose calculation program. In other words, the effective dose can be calculated using the ESD (Entrance Surface Dose) and the Dose Area Porduct (DAP), which requires a g-factor for general radiography effective doses.

The effective dose to which the effective dose conversion factor is applied can be calculated as shown in Equation (4).

At this time, the effective dose conversion factor is a factor that converts the effective dose of the patient to the effective dose of the patient using the radiation dose index (ESD), the dose area product (DAP), the incident air kerma (EAK) . Therefore, the effective dose calculated for each general radiography test is divided by the radiation dose such as incident surface dose, dose area product, incident air kerma, and the effective dose value of the patient is the inspection condition (tube voltage, filter thickness, , Test area, and test site.

However, the effective dose conversion factor applied to the present embodiment uses a constant value as described below, and only the average inspection condition for each test for calculating the effective dose conversion factor is shown in Table 11 below.

The effective dose conversion factor can be summarized as follows. The effective dose conversion factor can be derived for the incident surface dose (ESD) and the dose area product (DAP), and the effective dose conversion factor (E / ESD) by the incident surface dose and the effective dose conversion The factor (E / DAP) is shown in Table 12 and Table 13 below.

Thus, this embodiment provides a radiation dose calculation method for evaluating the patient dose for various general radiography, and also provides a patient dose calculation program for evaluating the patient effective dose in general radiography.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be apparent that modifications, variations and equivalents of other embodiments are possible. Therefore, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: Patient dose calculation program

Claims (9)

A method for calculating a radiation dose of an X-ray examination applied to a patient's dose management system,
Providing a test condition for the patient's dose management system to evaluate a patient dose according to a general radiography using a pre-built database; And
Wherein the dose management system of the patient includes the step of calculating the dose of radiation according to the inspection condition using Equation (1).
[Formula 1]

Where FA is the filter thickness (mm Al), kVp is the tube voltage, mAs is the tube current, and FSD is the focus-patient distance (cm). The method according to claim 1,
The inspection conditions include,
Calculate the radiation dose of the air not including the backscattering dose,
The tube current is 10mAs, the distance between the focus and the instrument is 80cm, the total filter thickness is 2.5, 4.5, 6.5, 8.5mm Al, and the tube voltage is 40 ~ 140kVp. Calculation method. The method according to claim 1,
The formula (1) is a method of calculating a radiation dose of an X-ray photographing test that shows the exponent of the tube voltage as a quadratic function. The method according to claim 1,
A method for calculating the radiation dose of an X-ray examination that calculates the radiation dose by obtaining Equation 2 in which the indirect radiation dose calculation factor NDD (k) is applied to Equation 1 above.
[Formula 2]

In this case, NDD (k) is the indirect radiation dose calculation factor according to the tube voltage (kVp) and the filter thickness (mmAl) of the general radiographic apparatus, mAs is the product of the tube current (mA) Distance between patients (m). An inspection range input window for inputting inspection type, photographing direction, image size, inspection condition, and filter thickness information; And
And a calculation window for calculating an effective dose by using an incident surface dose (ESD) or a dose area product (DAP). 6. The method of claim 5,
Wherein the effective dose is obtained by the equation (3).
[Formula 3]

Here, the effective dose conversion factor is a value for evaluating the effective dose from the dose of the incident surface dose (ESD) or the dose area product (DAP). The method according to claim 6,
The effective dose conversion factor may be expressed as:
(E / ESD) based on the incident surface dose established by the direction of incidence of X-rays in gender examination according to the weight of tissue of the International Radiation Protection Committee (ICRP) for general radiography; And
And an effective dose conversion factor (E / DAP) by a dose area product. 6. The method of claim 5,
The calculation window includes:
A dose amount information input window, a dose area product information input window, a weight information input window, and a dose and effective information input window. 6. The method of claim 5,
Wherein the radiation dose calculation simulator used in the radiation dose calculation program is a radiation dose calculation simulator such as a human body shape.

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