KR101709406B1 - Method for calculating radiation dose in cr system - Google Patents

Abstract

The present invention relates to a method for calculating a radiation dose in a CR system. The method for calculating a radiation dose in a CR system comprises: (A) a step of acquiring a raw image prior to image processing in the CR system; and (B) a step of calculating at least one among an incident surface dose, an incident skin dose, an area dose, and an effective area dose as the radiation dose based on each pixel value of the raw image. Accordingly, a processing image provided by the CR system is used to acquire a raw image, and various types of radiation doses affecting patients can be measured simply only through analysis of the pixel values of the raw image. In addition, a radiation dose for a processing image photographed by a conventional CR system which does not provide information for the radiation dose can be measured, thereby eliminating a need for separately purchasing a dose measuring instrument or replacing the CR system to provide radiation dose information.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for calculating a radiation dose in a CR system,

The present invention relates to a method of calculating a radiation dose in a CR (Computed Radiography) system, and more particularly, to a method of calculating a radiation dose in a CR (Computed Radiography) system by analyzing a pixel value of a processing image or a raw image, The present invention relates to a method of calculating a radiation dose from a processing image obtained by a CR system capable of calculating various types of radiation dose information.

The digital medical imaging system has a function of automatically recognizing an effective range of an incident X-ray distribution and converting a range in which an X-ray image exists into a digital image. The relationship between incident X-rays and pixel values used in such a transformation depends on the X-ray dose and the histogram absorbed by the image receptor, and the conversion function is defined in the digital medical imaging system itself.

In addition, the digital medical imaging system can display or output the parameters calculated in the process of converting incident X-ray distribution into digital images. These parameters are generally referred to as image processing parameters and have been used as a standard for the dynamic range of X-ray dose entering a digital medical imaging system.

By the above-described conversion process, even in the case of the X-ray dose in the digital medical imaging system, it is possible to obtain an appropriate output image, and the degree of the patient's exposure can not be known. Therefore, unless the dose value is displayed together with the output image in the equipment itself, it becomes difficult to manage the exposure of the patient.

 For the above reasons, it is preferable to display the dose of the patient in the digital medical imaging system, and international regulations and domestic regulations are being discussed to reflect this. For example, IEC 60601-1-3 Radiation protection in diagnostic X-ray equipment for diagnostic radiology (IEC 60601-1-3) and IEC 60601-2-54 X-ray equipment for radiography The basic safety and essential performance of X-ray equipment for radiography and radioscopy is to provide diagnostic X-ray equipment with dose information that is useful for assessing the amount of radiation, .

In addition, the Korea Standard for the Safety of Food and Drug Administration No 2014-122 complies with the International Standard for the Safety of Electrical and Mechanical Safety of Medical Devices, so that the International Standard will be applied gradually from January 2015 , And it is stipulated that the medical device should be applied sequentially from the medical device of class 4 to the medical device of class 1.

Therefore, in order to meet the above-mentioned international standards and domestic standards, there is a need for a technique for real-time measurement and display of the amount of radiation irradiated to a patient through medical irradiation.

Unlike DR (Direct Radiography) equipment in which DICOM header information includes information on photographing conditions, in the case of a CR (Computed Radiography) system, area dose values are displayed only in equipment that has recently been released However, in hospitals using existing CR systems without area dose dosimeters, real-time radiation dosimetry and exposure doses can not be displayed.

In addition, even in the case of a CR system with an area dose meter, since the area dose meter is attached to the front of the radiation generator, it is possible to reflect the X-ray portion, which is not incident on the patient's skin, There is a fundamental problem that an area dose to be irradiated and an error occur.

Therefore, in the case of the CR system, it is required for a method of calculating the exposure dose through the calculation without the area dose meter. In the IR Edmons, "Calculation of patient skin dose from diagnostic X-ray procedures (Br J Radiol, Vol. 57, pp. 733-744, 1984.), J. Chunan, H. Tung and Tsai, "Evaluations of Gonad and Fetal Doses for Diagnostic Radiology (Proc. Natl. Sci. 23, No. 2, pp. 107-113, 1999.).

However, the methods disclosed in the above-mentioned papers use an approach of analyzing the amount of X-rays irradiated from the X-ray irradiating part such as tube voltage, tube current of the X-ray irradiating part, And there is a disadvantage in that it includes an error appearing in the area dose meter as described above.

Therefore, in the CR system, it is applicable to the existing CR system without using the equipment for measuring the dose of the X-ray, for example, the area dose meter, and reflects the actual dose It would be desirable if an accurate calculation method could be proposed.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an image processing apparatus and a method thereof, It is an object of the present invention to provide a method of calculating a radiation dose from a processing image obtained by a CR system capable of calculating information.

This object is achieved according to the present invention by a method for calculating a radiation dose in a CR system, comprising the steps of: (A) obtaining a raw image prior to image processing in the CR system; (B) calculating at least one of incident surface irradiation dose, incident skin dose, area dose and effective area dose based on each pixel value of the row image as the radiation dose And calculating the radiation dose.

Wherein (A) comprises: (A1) registering a mode characteristic equation for each of a plurality of image processing modes of the CR system, and a normalization feature equation for at least one image processing parameter for each of the image processing modes; ; (A2) a processing image generated by processing the raw image by the CR system and an image processing mode and an image processing parameter value of the processing image; (A3) a first inverse corrected pixel value is calculated by applying each pixel value of the processing image to an output value of a mode characteristic equation corresponding to the image processing mode input in the step (A2); (A4) the second inverse corrected pixel value is calculated by applying the first inverse corrected pixel value to the output value of the normalized feature equation corresponding to the image processing mode input in the step (A2); (A5) obtaining the row image using the second inverse corrected pixel value as a pixel value.

The image processing parameter may also include a sensitivity adjustment parameter for adjusting the sensitivity of the image and a contrast adjustment parameter for adjusting the contrast of the image.

The step (A1) includes the steps of: (A11) image-processing a virtual digital test pattern having a predetermined gradation pattern according to one of the plurality of image processing modes to obtain a gradation characteristic curve for the image processing mode; ; (A12) analyzing the gradation characteristic curve to register a mode characteristic equation for the image processing mode; (A13) a sensitivity deviation relation in which a relationship between a change in the sensitivity adjustment parameter value and a sensitivity deviation of an input signal with respect to the same output signal according to a change in the sensitivity adjustment parameter value is registered; (A14) a step of registering a sensitivity normalization property expression having the sensitivity deviation as a slice; (A15) registering a slope characteristic expression defining a relationship between a change in the contrast degree adjustment parameter and a slope of the normalization characteristic equation; (A16) the step of registering the normalization characteristic expressions based on the sensitivity normalization characteristic expression and the slope characteristic expression, and the steps (A11) to (A16) are performed for each of the other of the plurality of image processing modes , The mode characteristic equation, the sensitivity normalization characteristic equation, the slope characteristic equation and the normalization characteristic equation for each image processing mode may be registered.

The step (A1) may further include the step of registering the range of the straight line section of the gradation characteristic curve.

In the step (A4), the sensitivity adjustment parameter value among the image processing parameter values inputted in the step (A2) is applied to the sensitivity deviation relation registered in the step (A13), and the sensitivity deviation is calculated ; (A42) determining the sensitivity normalization characteristic equation using the sensitivity deviation value as an intercept; (A43) calculating a rotation center according to a change in the contrast degree parameter based on the sensitivity normalization characteristic equation; (A44) calculating a slope value of the normalization characteristic equation by applying the contrast control parameter value among the image processing parameter values input in the step (A2) to the slope characteristic equation; (A45) the rotation center is input to the normalization characteristic equation, and a piece of the normalization characteristic equation is calculated to determine the normalization characteristic equation; (A46) The first inverse corrected pixel value is applied to the output value of the normalization characteristic equation determined in step (A55), and the second inverse corrected pixel value is calculated.

In step (A), a low image photographed by the CR system may be input.

Here, the calculating of the incident surface irradiation dose in the step (B) may include calculating an average value of the pixel values of the row image obtained in the step (A); Converting the average value into a transmission dose value; And calculating the incident surface irradiated dose by reflecting the susceptibility to the transmitted dose value.

The area dose can be calculated on the basis of the incident surface irradiation dose of each pixel based on the pixel value of the row image obtained in the step (A) and the area of the pixel of the row image.

Here, the area dose is expressed by the following equation: DAP = (ΣESE_pixel) × f × s_pixel (DAP is the area dose, ESE_pixel is the incident surface irradiation dose of each pixel, f is the absorbed dose conversion coefficient, s_pixel is the area Lt; / RTI > The method for calculating an incident surface irradiated dose may include converting a pixel value of the row image obtained in the step (A) into a transmittance dose value; And calculating the incident surface irradiated dose by reflecting the susceptibility to the transmitted dose value.

In the step (B), the effective area dose may be calculated as an area dose of a region that has passed through the measurement target.

×f×n×s_pixel (EDAP는 상기 유효면적선량이고,

는 유효입사표면적의 평균조사선량이고, f는 흡수선량변환계수이고, n은 유효입사표면적의 화소수이고, s_pixel은 화소의 면적이다)에 의해 산출되며; 상기 유효입사표면적은 상기 측정 대상을 투과한 영역으로 상기 (A) 단계에서 획득된 상기 로우 이미지의 관심 영역 내의 최대 화소값 이내의 화소값을 갖는 화소들의 포함하며; 상기 평균조사선량을 산출하는 방법은 상기 유효입사표면적을 구성하는 화소의 화소값의 평균값을 산출하는 단계와; 상기 평균값을 투과선량값으로 변환하는 단계와; 상기 투과선량값에 감약율을 반영하여 상기 평균조사선량을 산출하는 단계를 포함할 수 있다.Here, the effective area dose is given by the equation EDAP =

× f × n × s_pixel (EDAP is the effective area dose,

Where f is the absorbed dose conversion factor, n is the number of pixels of the effective incidence surface area, and s_pixel is the area of the pixel); Wherein the effective incidence surface area includes pixels having a pixel value within a maximum pixel value within an area of interest of the row image obtained in step (A), the area being transmitted through the measurement object; Calculating a mean value of pixel values of pixels constituting the effective incident surface area; Converting the average value into a transmission dose value; And calculating the average irradiation dose by reflecting the susceptibility to the transmission dose value.

The incident skin dose is given by the following equation: D = X _air x f x BSF where D is the incident skin dose, X _air is the incident surface irradiation dose, f is the absorbed dose conversion coefficient, and DSF is the back scattering coefficient. Lt; / RTI >

According to the present invention, according to the present invention, it is possible to acquire a row image using a processing image provided by a CR system, and to measure various types of radiation dose do.

In addition, it is possible to measure the radiation dose also for the processing image photographed by the existing CR system which does not provide information on the radiation dose, so that a dose meter is purchased separately or the replacement of the CR system It becomes unnecessary.

When the CR system provides a low image, it is possible to directly calculate the radiation dose using the corresponding low image.

1 is a view showing a configuration of a CR system according to the present invention,
2 is a view showing an example of a configuration of a plate reader of a CR system according to the present invention,
3 shows an example of an X-ray image and a histogram thereof,
4 is a diagram showing an example of the EDR curve of the CR system,
5 is a view for explaining a method of calculating the radiation dose in the CR system according to the present invention,
6 is a view for explaining an example of a process of registering a mode characteristic equation and a normalization characteristic equation in a method of calculating a radiation dose according to the present invention,
7 is a diagram showing an example of a virtual digital test pattern and a processing image obtained by image processing the virtual digital test pattern,
8 to 11 are diagrams showing examples of input / output characteristic curves in the CR system.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

[CR system]

1 is a diagram showing a configuration of a CR system 100 according to the present invention. 1, a CR system 100 according to the present invention includes an x-ray tube 110 for irradiating an x-ray, an image plate 120, a plate reader 130, and an image processing apparatus 140.

The image plate 120 is a flexible plate having a predetermined thickness and is coated with a vibrating phosphor. When excited phosphors are excited by x-rays, electrons, ultraviolet rays, etc., they absorb energy absorbed in quasi-energy state. And, when it is stimulated by visible light or ultraviolet light, it has a characteristic of emitting energy corresponding to absorbed energy.

The plate reader 130 reads the radiation image from the image plate 120 on which the latent image is formed by the X-ray. 2 is a diagram showing an example of the configuration of the plate reader 130 of the CR system 100 according to the present invention. 2, the plate reader 130 includes a laser beam irradiator 131, an optical scanner 132, a photomultiplier tube 133, an A / D converter 134, and an image processor 135 .

The laser beam irradiated by the laser beam irradiating part 131 is reflected by the optical scanner 132 and is directed to the image plate 120. Here, the laser beam irradiated by the laser beam irradiating unit 131 according to the rotation of the optical scanner 132 is subjected to a line scan of the image plate 120, and is scanned by the roller or the like in the direction perpendicular to the scanning direction The entire surface of the plate 120 is sequentially scannable.

The laser beam reflected from the image plate 120 is received by the photo multiplier 133 containing the radiation image information, and the photo multiplier 133 converts the optical image signal received to the electrical image signal.

Then, the electrical image signal generated by the photo-multiplier 133 is converted into a digital image signal through the A / D converter 134. That is, the digital image signal output from the A / D converter 134 becomes a low image including the radiation image information.

The raw image output from the A / D converter 134 is converted into a final processed image through an image processing process of the image processor 135, and the processed image is transmitted to an image processing apparatus 140 such as a computer, And the like can visually check the processing image.

[Image processing]

The image processor 135 of the CR system 100 according to the present invention outputs the row image transmitted from the A / D converter 134 to the processing image through automatic gradation processing, frequency processing, and equalization processing.

In the automatic gradation processing, gradation processing conditions optimal for each image are automatically determined, and the gradation of the low image is converted according to the conditions to obtain a sensitivity (or density, hereinafter referred to as sensitivity) Process.

Generally, in the image processor 135 of the CR system 100, a read sensitivity adjustment method by read-ahead is applied. That is, the image plate 120 analyzes the level range of the recorded X-ray signal by scanning with a weaker laser than the image reading, which is referred to as read-ahead. Then, the range of the signal to be digitally imaged when the image reading is proceeded is determined.

The level range of the signal recorded in the read-ahead image plate 120 is interpreted by a histogram. 3 (a) shows an example of an X-ray image, and FIG. 3 (b) shows a histogram of FIG. 3 (a).

The horizontal axis of the histogram shown in FIG. 3 (b) shows the intensity of the signal recorded on the image plate 120, that is, the X-ray, and the vertical axis shows the presence frequency of each intensity signal. In the case of the chest, the signal at the upper part of the shoulder, that is, the part of the space other than the human body, is strongest and represents the apex of the rightmost part of the histogram, and the signal of the lower part of the medulla is located at the leftmost position with the minimum histogram. When the X-ray dose at the time of photographing is large, this histogram is located on the right side of the horizontal axis.

The automatic sensitivity adjustment (EDR) performed by the image processor 135 of the CD apparatus analyzes the position and the range of the histogram as described above to determine the range in which the x- .

Accordingly, even if the X-ray dose at the time of photographing is excessive, the image processor 135 of the CR system 100 automatically adjusts the sensitivity, so that a final processing image that can be read visually can be provided.

The basic principle of the EDR processed by the image processor 135 can be confirmed through the EDR curve shown in Fig.

The first quadrant of the EDR curve shows the intensity relationship between the X-ray dose absorbed in the image plate 120 and the amount of emitted flash generated in accordance with the laser stimulus. Here, a linear relationship is shown in the diagnostic areas 1 to 10 ⁴ , which contributes to improving the diagnostic area and sensitivity of the CR system 100.

The second quadrant shows the relationship between the input signal of the image processor 135, that is, the pixel value of the low image, and the output signal by adjusting the sensitivity and contrast. At this time, the image processor 135 automatically adjusts the sensitivity and contrast of the low image based on the sensitivity adjustment parameter value and the contrast adjustment parameter value.

The third quadrant shows the relationship between the automatically adjusted signal based on the sensitivity adjustment parameter value and the contrast adjustment adjustment parameter value, and the signal adjusted by the image processing mode. The image processing mode is registered according to the adjustment characteristic suitable for each diagnosis such as a chest, a breast, etc., and shows a lookup table (LUT) characteristic performed according to independent image processing characteristics.

The fourth quadrant represents the X-ray dose and the sensitivity of the final processed image, and reflects the output characteristics after gradation processing.

In the CR system 100 according to the present invention, the image processing parameters include the sensitivity control parameter and the contrast control parameter, as described above.

The sensitivity adjustment parameter is a measure of the sensitivity of the processing image to a value corresponding to the concentration of the processing image. When the sensitivity adjustment parameter is changed, the EDR curve of the second quadrant is shifted in the horizontal direction.

The contrast control parameter is a measure for the contrast of the processing image. If the contrast control parameter value changes, the slope of the EDR curve of the second quadrant changes.

[Calculation method of radiation dose]

Hereinafter, a method of calculating the radiation dose in the CR system 100 according to the present invention will be described in detail with reference to FIGS. 5 to 11. FIG.

The method for calculating the radiation dose in the CR system 100 according to the present invention includes the steps of acquiring a raw image before image processing in the CR system 100, And calculating at least one of an incident skin dose, an area dose, and an effective area dose as a radiation dose.

The raw image is data not provided in the conventional CR system 100 and the data stored in the patient's x-ray image is a processing image subjected to image processing by the image processor 135 of the CR system 100.

In an embodiment of the method of calculating the radiation dose according to the present invention, the radiation dose is calculated using the processing image.

Referring to FIG. 5, a method for acquiring raw data from a processing image in a method of calculating a radiation dose according to the present invention will be described in detail.

The CR system 100 has an image processing process by a plurality of processing modes and an image processing process by image processing parameters, as described above. In the method of calculating the radiation dose according to the present invention, the processing image is processed back to the image processing procedure of the CR system 100 to obtain the raw data.

First, a mode characteristic equation for each of a plurality of image processing modes and a normalization characteristic equation for at least one image processing parameter for each image processing mode are registered (S50). Here, the image processing parameter includes a sensitivity adjustment parameter for adjusting the sensitivity of the image and a contrast adjustment parameter for adjusting the contrast of the image.

FIG. 6 shows an example of a process of registering a mode characteristic equation and a normalization characteristic equation in a method of calculating a radiation dose according to the present invention.

A virtual digital test pattern having a predetermined tone pattern is subjected to image processing according to one of the image processing modes (S60), and a tone characteristic curve is obtained (S61). 7 (a) shows an example of a virtual digital test pattern, and Fig. 7 (b) shows a processing image obtained by image processing a virtual digital test pattern in a mode suitable for chest radiography during image processing mode.

As shown in FIG. 7, when a virtual digital test pattern and a processing image are analyzed, a gradation characteristic curve can be obtained. FIG. 8 shows an example of a gradation characteristic curve according to each image processing mode.

8 is obtained for five image processing modes of the REGIUS 150 CR system 100. The virtual digital test pattern is generated using a binary editor program 'Hex Editor NEO' , And it uses 33 steps as a gray scale 12 bit file.

When the gradation characteristic curve is obtained through the above method, the mode characteristic equation of the corresponding image processing mode can be obtained and registered through analysis of the gradation characteristic curve (S61). Here, the mode characteristic equation is determined as a linear function between input and output. The range of the linear section is determined in the gradation characteristic curve shown in FIG. 8, and the linear function corresponding to the linear section is registered as the linear equation. At this time, the range of the straight line section is registered together with the mode characteristic expression. The mode characteristic equation can be expressed by Equation (1).

[Equation 1]

y = a x x + b

Where a and b values are constants determined through analysis of the linear section of the gradation characteristic curve for each image processing mode.

Meanwhile, the normalization characteristic equation can be determined by the sensitivity deviation relation formula and the sensitivity normalization characteristic equation, and the sensitivity deviation relation expression and the sensitivity normalization characteristic equation are registered together with the normalization characteristic equation.

The sensitivity deviation relation can be defined as a relationship between a change in the sensitivity adjustment parameter value and a sensitivity deviation of the input signal with respect to the same output signal according to the change in the sensitivity adjustment parameter value.

The variation of the output signal according to the sensitivity adjustment parameter varies depending on the value of each CR system 100, but the characteristic of shifting the EDR curve in the second quadrant of FIG. 4 in the lateral direction .

In the method of calculating the radiation dose according to the present invention, the sensitivity deviation relation and the normalization characteristic equation are exemplified by a method obtained through an experiment using a virtual digital test pattern applied to a mode characteristic equation and a method obtained by calculation.

The method of obtaining the test result will be described by comparing the amount of input exposure with the output pixel value according to the change of the sensitivity adjustment parameter and checking how the sensitivity adjustment parameter affects the pixel value of the output image.

To this end, a virtual digital test pattern is input to the image processor 135 and the image processing mode of the image processor 135 is changed to the LIN-01 mode of the FIX processing of the REGIUS 150 CR system 100, ) To analyze the pixel value of the output image according to the change of the sensitivity adjustment parameter.

(S _d = 293) of the sensitivity adjustment parameter is changed to the value of S ₁ , and the relative value of the ratio is apparently defined as the relative exposure amount difference ΔE. S ₁ applies 146, which is smaller than the default, and 590, which is larger than the default. At this time, the contrast adjustment parameter is fixed to a default value.

&Quot; (2) "

? E = Log (S _d / S ₁ )

In addition, when the default value of the sensitivity adjustment parameter is changed to S ₁ , that is, the sensitivity deviation between the input signals to the same output signal according to the change in the sensitivity adjustment parameter value is denoted by SS, the gradation level for reading the input signal is DD, If the number of digits of the range is KK, it can be expressed as Equation (3).

&Quot; (3) "

? E = (SS / DD) KK

In the equation (3), the DD and KK values are constants determined according to the CD apparatus. For the REGIUS 150 CR system 100, DD can be determined to be 4096 and KK can be determined to be 4.

The results of analyzing the sensitivity adjustment parameter and the pixel value of the output image in the LIN-01 mode of FIX processing in the above experiment are shown in FIG. Referring to FIG. 9, when the sensitivity adjustment parameter is 293, which is the default value, and when it is changed to 146 and 590, the difference in the input pixel value corresponding to the same output pixel value, that is, SS was fixed at 310.

The results of analyzing the S value and the pixel value of the output image are as follows. First, when the S value is 293 (default) and when the S value is changed to 146, 590, the difference (SS) of the input pixel value corresponding to the same output pixel value is 310. Further, by using the equations (2) and (3), the same ΔE value is obtained.

10 is a graph showing characteristic curves of the fourth quadrant of the EDR curve in the THX-01 mode of FIX processing. The characteristic curve according to the change of the sensitivity adjustment parameter can be defined according to the change of the straight line section, and the range of the straight line section can be determined by the range of the straight line section registered at the time of registration of the mode characteristic expression.

Then, the sensitivity normalization characteristic equation corresponding to the second quadrant can be obtained through the characteristic curve and the range of the straight line section shown in FIG.

On the other hand, the sensitivity normalization property equation can be determined by calculating the SS value of Equation (3) as shown in Equation (4).

&Quot; (4) "

y = x - SS

Here, the SS value can be calculated through Equation (5) through the result that Equation (3) and Equation (4) yield the same ΔE value.

&Quot; (5) "

Log (S _d / S ₁ ) = (SS / DD) KK

Here, [Expression 5] is registered as the sensitivity deviation relation expression (S63), and [Equation 4] is registered as the sensitivity normalization property expression having the sensitivity deviation as a slice (S63).

6, the slope characteristic equation for defining the relationship between the change of the contrast degree adjustment parameter and the slope of the normalization characteristic equation is registered with the sensitivity deviation relation expression and the sensitivity normalization characteristic equation as described above do.

As described above, the change of the contrast degree adjustment parameter has a characteristic of changing the slope of the second quadrant graph of the EDR characteristic curve, and the relation between the change of the contrast degree adjustment parameter and the change of the slope is registered as the slope characteristic equation.

Here, the slope characteristic equation can be obtained by analyzing the EDR curve obtained through image processing with the sensitivity adjustment parameter set to a default value using a virtual digital test pattern in each image processing mode. 11 shows a characteristic curve which is the fourth quadrant of the EDR curve in the THX-01 mode of FIX processing.

In each image processing mode, the change of the slope according to the change of the contrast adjustment parameter has a certain ratio, and the slope characteristic equation can be expressed by Equation (6).

&Quot; (6) "

SF = c x G

In Equation (6), SF is the slope, c is the slope ratio in each mode, and G is the contrast control parameter.

Then, the finally registered normalization property expression can be expressed as Equation (7), and it is registered as a normalization property expression.

&Quot; (7) "

y = SF x x + d

Here, d is a value determined in a calculation process of a second-order inverse-corrected pixel value, which will be described later.

The above process is performed for all the image processing modes of the CR system 100, and the registration of the mode characteristic equation, the sensitivity deviation relation, the sensitivity normalization characteristic equation, the slope characteristic equation and the normalization characteristic equation is performed for each image processing mode (See S66 in Fig. 6).

Referring to FIG. 5 again, when the registration process such as the mode characteristic equation is completed through the above process, the processing image, the image processing mode applied to the corresponding processing image, and the image processing parameter value, The adjustment parameter value is input (S51).

Here, the image processing mode, the sensitivity adjustment parameter value, and the contrast adjustment adjustment parameter value applied to the input processing image may be included in the DICOM header information of the corresponding processing image file and directly input based on the separately recorded contents.

Then, the primary inverse corrected pixel value is calculated by applying each pixel value of the processing image to the output value of the mode characteristic equation shown in [Equation 1], that is, the y value (S53). Then, the primary inverse corrected pixel value is applied to the output value of the normalization characteristic equation corresponding to the image processing mode, and the secondary inverse corrected pixel value is calculated (S53).

5, first, the sensitivity control parameter value input in step S51 is substituted into the sensitivity deviation relation expression of equation (5), and the SS value as the sensitivity deviation is calculated (S531). Here, Sd in Equation (5) is already registered as a default value of the sensitivity adjustment parameter, and DD and KK values are as described above.

Then, the calculated sensitivity deviation SS value is applied as an intercept of the sensitivity normalization characteristic equation of [Equation 4] to determine the sensitivity normalization characteristic equation (S532). Then, when the sensitivity normalization characteristic equation is determined, the center of rotation corresponding to the change in the contrast degree parameter is calculated using the sensitivity normalization characteristic equation.

Here, the center of rotation is the center coordinate in the change of the slope according to the change of the contrast degree parameter in a state where the sensitivity adjustment parameter is fixed. In the straight line graph according to the sensitivity normalization characteristic equation, the center in the range of the above- Center.

Therefore, when the sensitivity normalization characteristic equation is determined, the center coordinates in the range of the straight line section can be calculated.

Meanwhile, the contrast control parameter value input in the step S51 is applied to the slope relation of Equation (6) to calculate the slope SF of the normalization characteristic equation (S534). Then, the calculated slope value and the coordinates of the center of rotation are input to the normalization characteristic equation of Equation (7), and the b value of the normalization characteristic equation is calculated to determine the normalization characteristic equation of Equation (7) (S535).

When the normalization characteristic equation is determined through the above process, the first inverse complementary pixel value calculated in step S52 is input to the output value of the normalization characteristic equation, that is, the y value to calculate the x value, that is, the second inverse corrected pixel value (S536) .

At this time, the second inverse corrected pixel value is set to the pixel value of the low image, so that the low image is obtainable.

Through the above process, when a row image is obtained from the processing image, the radiation amount is calculated using the obtained row image.

Generally, the ESD (Entrance Skin Dose) is obtained by multiplying the air kermer and the back scatter fraction (BSF) at a given point of the patient.

In the method for calculating the amount of radiation according to the present invention, incident surface irradiation dose is calculated from a raw image by the following method.

First, an average value of pixel values of a row image is calculated. Then, the average value is converted into the transmission dose value (or the detector incident dose value, the same applies hereinafter), and the incidence surface irradiation dose is calculated by reflecting the subtraction rate on the converted transmission dose value.

Here, since the pixel value (or the average value) of the low image is not determined as the transmission dose value, the pixel value is converted into the transmission dose value. For this purpose, by acquiring and registering the relationship between the pixel value and the incident dose value according to the intensity of the X-ray (tube voltage) through experimentation, the pixel value can be converted into the transmission dose value. Equation (8) shows an example of a relational function between the pixel value and the transmittance dose value at each tube voltage in the REGIUS 150 CR system (100).

&Quot; (8) "

60 kVp:

80 kVp:

100 kVp:

120 kVp:

Here, S _IP is a transmission dose value, and P _VR is a pixel value.

Also, the deceleration rate is measured and registered according to the change of the tube voltage through the experiment. Equation (9) shows an example of the sensible expression measured by the REGIUS 150 CR system 100.

&Quot; (9) "

60 kVp:

80 kVp:

100 kVp:

120 kVp:

In the above example, the average value of the pixel values of the row image is converted into the transmission dose value, and the incident surface irradiation dose is calculated by reflecting the subtraction rate on the converted transmission dose value. However, the pixel values are converted into the transmission dose values , It is needless to say that the average value of the values reflecting the decay rate can be calculated by the incidence surface irradiation dose.

Further, in the case of [Equation 8] and [Equation 9], if a constant error rate is to be taken, each Equation can be set to one equation.

On the other hand, the area dose can be calculated on the basis of the incident surface irradiation dose of each pixel based on the pixel value of the low image and the area of the pixel of the low image.

For example, the area dose can be calculated by the following equation (10).

&Quot; (10) "

DAP = (ΣESE_pixel) × f × s_pixel

(Where DAP is the area dose, ESE_pixel is the incident surface irradiation dose of each pixel, f is the absorbed dose conversion coefficient, and s_pixel is the area of the pixel.

Here, in the method of calculating the incident surface irradiation dose, the incident surface dose for each pixel can be calculated by converting the pixel value of the low image into the transmission dose value and reflecting the susceptibility to the transmission dose value.

Meanwhile, in the method of measuring the area dose according to the present invention, the effective area dose can be measured by the area dose. The effective area dose represents the area dose for the area to be measured, for example, the area transmitted through the patient, that is, the area dose to the area from which the area not passed through the patient is removed from the area dose.

As can be seen from the chest X-ray image shown in FIG. 3 (a), the conventional area dose includes an X-ray that does not reflect the dose received directly by the patient and does not affect the patient. On the other hand, the effective area dose can be defined as the concept of measuring only the x-rays directly irradiated to the patient, and calculating the dose of the x-ray directly received by the patient.

Equation (11) shows an example of a method of calculating the effective area dose according to the present invention.

&Quot; (11) "

×f×n×s_pixelEDAP =

× f × n × s_pixel

는 유효입사표면적의 평균조사선량이고, f는 흡수선량변환계수이고, n은 유효입사표면적의 화소수이고, s_pixel은 화소의 면적이다Here, EDAP is an effective area dose,

F is the absorbed dose conversion factor, n is the number of pixels of the effective incident surface area, and s_pixel is the area of the pixel

In one example of the present invention, the effective incidence surface area, that is, the area corresponding to the patient, i.e., the area through which the measurement object is transmitted, includes pixels having pixel values within a maximum pixel value within a ROI image. That is, a pixel value larger than the maximum pixel value in the region of interest, that is, a region where the intensity of the X-ray is largely measured, is excluded. In addition, the effective incidence surface area can be determined through the method of extracting the boundary region in the image analysis method.

In the method of calculating the average irradiation dose in the expression (11), the average value of the pixel values of the pixels constituting the effective incidence surface area is calculated, the average value is converted into the transmission dose value, and the subtraction rate is reflected in the transmission dose value The average irradiation dose can be calculated.

On the other hand, the incidence skin dose can be calculated through the equation (12).

&Quot; (12) "

D = X _air x f x BSF

D is the incident skin dose, X _air is the incident surface irradiation dose, f is the absorbed dose conversion coefficient, and DSF is the back scattering coefficient.

According to the above-described configuration, in the method of calculating the radiation dose according to the present invention, a low image is acquired using a processing image, and various types of radiation dose do.

In addition, it is possible to measure the radiation dose also for the processing image photographed by the existing CR system 100 which does not provide information on the radiation dose, so that the radiation dose information can be obtained by separately purchasing the dose measuring device, (100) is not required to be replaced.

In the above-described embodiment, an example has been described in which a low image is obtained from a processing image to calculate a radiation dose. In addition, it is possible to calculate the radiation dose by directly using the low image of the CD equipment. For example, when a manufacturer of a CD device provides a raw image file when providing a processing image, the radiation dose can be calculated directly using the raw image.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be exemplary and explanatory only and are not to be construed as limiting the scope of the inventive concept. And it is obvious that it is included in the technical idea of the present invention.

100: CR system 110: X-ray tube
120: image plate 130: plate reader
131: laser beam irradiation part 132: optical scanner
133: optoelectronic amplifier tube 134: A / D converter
135: image processor 140: image processing device

Claims (13)

delete A method of calculating a radiation dose in a CR system,
(A) obtaining a raw image prior to image processing in the CR system;
(B) calculating at least one of incident surface irradiation dose, incident skin dose, area dose, and effective area dose based on each pixel value of the row image as the radiation dose,
The step (A)
(A1) registering a mode characteristic equation for each of a plurality of image processing modes of the CR system and a normalization characteristic equation for at least one image processing parameter for each of the image processing modes;
(A2) a processing image generated by processing the raw image by the CR system and an image processing mode and an image processing parameter value of the processing image;
(A3) a first inverse corrected pixel value is calculated by applying each pixel value of the processing image to an output value of a mode characteristic equation corresponding to the image processing mode input in the step (A2);
(A4) calculating a second-order inverse-corrected pixel value by applying the first-order inverse-compensated pixel value to an output value of a normalization-based equation corresponding to the image processing mode input in step (A2);
(A5) obtaining the row image using the second inverse corrected pixel value as a pixel value, and calculating the radiation dose in the CR system. 3. The method of claim 2,
Wherein the image processing parameter comprises a sensitivity adjustment parameter for adjusting the sensitivity of the image and a contrast adjustment parameter for adjusting the contrast of the image. The method of claim 3,
The step (A1)
(A11) image-processing a virtual digital test pattern having a predetermined gradation pattern according to one of a plurality of the image processing modes to obtain a gradation characteristic curve for the image processing mode;
(A12) analyzing the gradation characteristic curve to register a mode characteristic equation for the image processing mode;
(A13) a sensitivity deviation relation in which a relationship between a change in the sensitivity adjustment parameter value and a sensitivity deviation of an input signal with respect to the same output signal according to a change in the sensitivity adjustment parameter value is registered;
(A14) a step of registering a sensitivity normalization property expression having the sensitivity deviation as a slice;
(A15) registering a slope characteristic expression defining a relationship between a change in the contrast degree adjustment parameter and a slope of the normalization characteristic equation;
(A16) a step of registering the normalization characteristic equation based on the sensitivity normalization characteristic equation and the slope characteristic equation,
(A11) to (A16) are performed for each of the plurality of the image processing modes, and the mode characteristic equation, the sensitivity normalization characteristic equation, the slope characteristic equation and the slope characteristic equation for each of the image processing modes Wherein the normalization characteristic equation is registered. 5. The method of claim 4,
Wherein the step (A1) further includes the step of registering the range of the straight line section of the gradation characteristic curve. 6. The method of claim 5,
The step (A4)
(A41) the sensitivity adjustment parameter value among the image processing parameter values inputted in the step (A2) is applied to the sensitivity deviation relation registered in the step (A13), and the sensitivity deviation is calculated;
(A42) determining the sensitivity normalization characteristic equation using the sensitivity deviation value as an intercept;
(A43) calculating a rotation center according to a change in the contrast degree adjustment parameter based on the sensitivity normalization characteristic equation;
(A44) calculating a slope value of the normalization characteristic equation by applying the contrast control parameter value among the image processing parameter values input in the step (A2) to the slope characteristic equation;
(A45) the rotation center is input to the normalization characteristic equation, and a piece of the normalization characteristic equation is calculated to determine the normalization characteristic equation;
(A46) a step of calculating the secondary inverse corrected pixel value by applying the primary inverse corrected pixel value to the output value of the normalization equation determined in the step (A55) / RTI > 3. The method of claim 2,
Wherein in the step (A), a raw image photographed by the CR system is input. 8. The method according to claim 2 or 7,
The method for calculating the incident surface irradiation dose in the step (B)
Calculating an average value of the pixel values of the row image obtained in the step (A);
Converting the average value into a transmission dose value;
And calculating the incident surface irradiation dose by reflecting the susceptibility to the transmission dose value. 9. The method of claim 8,
Wherein the area dose is calculated on the basis of the incident surface irradiation dose of each pixel based on the pixel value of the row image obtained in the step (A) and the area of the pixel of the row image. How to calculate. 10. The method of claim 9,
The area dose is given by Equation
(Where DAP is the area dose, ESE_pixel is the incident surface irradiation dose of each pixel, f is the absorbed dose conversion coefficient, and s_pixel is the area of the pixel), DAP = (ΣESE_pixel) × f × s_pixel
The method for calculating the incident surface irradiation dose
Converting the pixel value of the row image obtained in the step (A) into a transmission dose value;
And calculating the incident surface irradiation dose by reflecting the susceptibility to the transmission dose value. 8. The method according to claim 2 or 7,
Wherein in the step (B), the effective area dose is calculated as an area dose of a region transmitted through the measurement object. 12. The method of claim 11,
The effective area dose is given by Equation
EDAP =

× f × n × s_pixel (EDAP is the effective area dose,

Where f is the absorbed dose conversion factor, n is the number of pixels of the effective incidence surface area, and s_pixel is the area of the pixel);
Wherein the effective incidence surface area includes pixels having a pixel value within a maximum pixel value within an area of interest of the row image obtained in step (A), the area being transmitted through the measurement object;
The method for calculating the average irradiation dose
Calculating an average value of pixel values of pixels constituting the effective incidence surface area;
Converting the average value into a transmission dose value;
And calculating the average irradiated dose by reflecting the susceptibility to the transmitted dose value. ≪ RTI ID = 0.0 > 8. < / RTI > 8. The method according to claim 2 or 7,
The incidence skin dose is expressed by Equation
D = X _air x f x BSF where D is the incident skin dose, X _air is the incident surface irradiation dose, f is the absorbed dose conversion coefficient, and DSF is the back scattering coefficient. A method for calculating a dose of radiation in a system.

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