KR20210081862A - The method for discriminating material using dual-energy x-ray and the calibration phantom device and the system thereof - Google Patents

Abstract

The present invention relates to a material fractionation method using dual energy X-rays, and a calibration phantom device and system for performing the method. In more detail, the present invention relates to a method in which a material classification coefficient is calibrated by generating a plurality of attenuation-based bases for a transmission image obtained through a rotating cylindrical or elliptical column-shaped calibration phantom in a cargo detector, and the material is fractionated by using the calibrated material fractionation coefficient, and a calibration phantom device and system for performing the method. A plurality of subject phantoms include a first subject phantom made of a single material.

Description

A method for material fractionation using dual energy X-rays, a calibration phantom device and a calibration phantom system for performing this method

The present invention relates to a material classification method using dual energy X-rays and a calibration phantom device for performing the method, and more particularly, using a transmission image obtained through a cylindrical or elliptical column-shaped calibration phantom rotating in a cargo screening machine. It relates to a method for fractionating substances and a calibration phantom device for performing the method.

Recently, for safety reasons, each country is strengthening security screening for cargo at facilities that handle international cargo, such as ports and airports. Accordingly, in order to quickly search for cargo, a device for quickly searching a large-scale cargo loaded in the container by passing a container loaded with the cargo through the container searcher, such as a container searcher, is widely used. Cargo screening will generally use X-rays as radiation.

The X-ray cargo inspection machine is composed of a radiation source, a transport truck, and a detector, and it is possible to search the inside of the cargo without direct inspection of the cargo by using X-rays.

Dual-energy X-ray cargo scanners provide more material information than single-energy X-rays. In particular, X-rays used for large-scale cargo search are MeV-class, and accelerators for generating dual-energy X-rays have been developed enough to be commercialized in Korea.

In order for the X-ray cargo detector to secure the image quality of the object, it is necessary to calibrate the detector every predetermined period, and for this calibration work, a phantom is used.

The Phantom is to calibrate the material classification algorithm. When using dual energy to distinguish organic and inorganic materials, a 3D image of the Phantom is secured, and the information of the 3D image is applied to the cargo image obtained from the container searcher. An algorithm that separates organic and inorganic substances will be used. At this time, it is possible to secure the performance of the detector by obtaining the value of the linear attenuation coefficient used in the material classification algorithm and correcting it.

More specifically, for each representative material (eg, water, aluminum, iron, or lead), a method of finding a material fractionation coefficient using a calibration phantom device is a commonly used dual energy material fractionation method.

And, before photographing the cargo with X-rays, calibration is performed on materials represented by atomic numbers. After that, the accuracy of material classification is greatly affected by the calibration method and the calibration phantom.

However, since X-rays generated from the accelerator have a multicolor energy spectrum, beam hardening occurs while penetrating an object. Due to beam hardening, even for the same material, it is necessary for material classification according to the density and thickness of the material. count will change.

Therefore, even for the same material, a coefficient required for material classification should be used differently according to the thickness and density of the material. Therefore, there is a need for a calibration method in consideration of a change in the thickness of a material and a calibration phantom including various thickness information for this.

However, it is difficult to build a database of all coefficients according to the thickness and density and to create a phantom for each thickness and density, and it is very difficult to calibrate all coefficients because actual calibration takes a lot of time.

On the other hand, the method of performing material fractionation by selecting several samples of arbitrary thickness to obtain coefficients is inaccurate, and has the disadvantage of significantly lowering material fractionation performance.

(KR) Registered Patent No. 10-1790135 (KR) Patent Publication No. 10-2012-0013724

The present invention has been devised to solve the above problems, and provides a calibration phantom device in consideration of thickness and density information of various materials, and a material classification method using the device.

An object of the present invention is to improve the material classification performance and further provide a method for reliable material classification even in the attenuated area of a material that cannot be corrected.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The calibration phantom device according to an embodiment of the present invention includes at least two or more plurality of subject phantoms made of a single material, and each of the plurality of subject phantoms is made of a different material. The subject phantoms may have a structure in which they are stacked in a direction perpendicular to a direction in which X-rays are irradiated.

The calibration phantom apparatus according to an embodiment of the present invention may be characterized in that the plurality of subject phantoms are elliptical or circular.

A calibration phantom apparatus according to an embodiment of the present invention may include: a first subject phantom made of a single material; and a second subject phantom made of a material different from that of the first subject phantom, wherein a radius of the second subject phantom may be smaller than a radius of the first subject phantom.

The calibration phantom apparatus according to an embodiment of the present invention may be characterized in that the thickness of each of the plurality of phantoms under test is different from each other.

The calibration phantom apparatus according to an embodiment of the present invention further includes a motor for rotating the plurality of subject phantoms, wherein the motor is disposed on the same axis in a direction in which the plurality of subject phantoms are stacked, and the motor It may be characterized in that the plurality of subject phantoms rotate according to the rotation.

A calibration phantom system according to an embodiment of the present invention may include a calibration phantom device and a material classification coefficient calculating device.

According to an embodiment of the present invention, an apparatus for calculating a material fractionation coefficient of a calibration phantom system includes: a transmission image receiver configured to receive a phantom transmission image of a subject obtained from an X-ray detector; an attenuated image data calculator configured to log-transform the received phantom transmission image with respect to a background signal to calculate attenuated image data; a basis generator for generating a basis by dividing the calculated attenuated image data into a plurality of image data based on a plurality of step-by-step thresholds; an image reconstruction unit for reconstructing image data based on the generated basis; and a material classification coefficient calculator for calculating a material classification coefficient from the reconstructed image data.

The apparatus for calculating the material classification coefficient of the calibration phantom system according to an embodiment of the present invention is performed for each of the plurality of m subject phantoms when the number of the plurality of step-by-step thresholds is n, so that the material classification coefficient is It may be characterized in that (mxn) dogs are produced.

The apparatus for calculating the material fractionation coefficient of the calibration phantom system according to an embodiment of the present invention may be characterized in that the attenuated image data calculating unit calculates the attenuated image data through the following equation.

Attenuated image data = -log(b/a)

(Here, a is the background signal and b is the transmitted image signal.)

In the apparatus for calculating the material fractionation coefficient of the calibration phantom system according to an embodiment of the present invention, the base generator is sequentially configured with the plurality of step-by-step threshold values at predetermined intervals to form a plurality of sections, and each pixel of the attenuated image data When the value of corresponds to any one of the plurality of sections, only the attenuated image data value of the corresponding pixel is maintained and the remaining pixels are 0 image data to output image data equal to the number of the plurality of sections, The output image data may be divided into image data for the plurality of sections.

The apparatus for calculating the material fractionation coefficient of the calibration phantom system according to an embodiment of the present invention may be characterized in that the image reconstruction unit is performed for each image data separated for each threshold section.

A method for material classification using dual energy X-rays according to an embodiment of the present invention includes the steps of: (a) acquiring, by an X-ray detector, a phantom transmission image of a subject irradiated from an X-ray source; (b) obtaining, by an apparatus for calculating a material classification coefficient, attenuated image data by log-transforming the phantom transmission image of the subject with respect to a background signal; (c) generating, by the apparatus for calculating the material discrimination coefficient, a basis for the attenuated image data by dividing the attenuated image data into a plurality of image data based on a plurality of step-by-step thresholds; (d) reconstructing the image data based on the generated basis by the material classification coefficient calculating device; and (e) calculating, by the apparatus for calculating a substance discrimination coefficient, a substance discrimination coefficient from the reconstructed image data.

In the method for material fractionation using dual energy X-rays according to an embodiment of the present invention, when the number of the plurality of step-by-step thresholds is n, all of the steps are performed for each of the plurality of m subject phantoms, and the material classification It may be characterized in that (mxn) coefficients are calculated.

The step (b) of obtaining the attenuated image data according to an embodiment of the present invention may be obtained through the following equation.

Attenuated image data = -log(b/a)

(Here, a is the background signal and b is the transmitted image signal.)

In the step (c) of generating a basis according to an embodiment of the present invention, the plurality of step-by-step thresholds are sequentially configured at predetermined intervals to form a plurality of sections, and the values of each pixel of the attenuated image data are outputting image data corresponding to any one of the plurality of sections by maintaining only the attenuated image data value of the corresponding pixel and outputting image data in which the remaining pixels are 0; and dividing the output image data into image data for the plurality of sections.

The step (d) of reconstructing a plurality of separated image data according to an embodiment of the present invention may be performed for each of the separated image data for each threshold section.

The present invention divides a transmission image of dual energy X-rays into an attenuation-based basis to allow material classification by considering changes in thickness and density of materials, and can greatly improve material discrimination performance when searching for materials.

In addition, according to the present invention, it is possible to reliably discriminate a material even for a thickness area of a material that is not measured using the obtained area coefficient.

According to an embodiment of the present invention, since the calibration phantom device performs calibration by dividing the transmission image based on the attenuation, there is an advantage in that it is possible to obtain a coefficient according to the difference in thickness and density.

That is, according to the present invention, the different material classification coefficients can be more precisely corrected according to the difference in the thickness and density of the material.

In addition, it is good to perform the calibration for all thickness ranges through which X-rays can transmit, but in practice, this can be burdensome in terms of cost and time. In the present invention, since the calibration is performed by dividing the attenuation-based basis, there is an advantage in that the material can be rationally classified using the linear interpolation method and the extrapolation method for the data area that has not been obtained.

Effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 shows a calibration phantom device according to an embodiment of the present invention.
2 shows a calibration phantom device according to another embodiment of the present invention.
3 shows a block diagram of a calibration phantom system according to an embodiment of the present invention.
4 shows a flow chart of a method for fractionating a substance using a calibration phantom system according to an embodiment of the present invention.
5 illustrates, by way of example, a plurality of step-by-step thresholds according to an embodiment of the present invention.
6A and 6B illustrate a method of dividing image data into a plurality of images according to an embodiment of the present invention.
7 to 8 show images reconstructed based on the separated base according to an embodiment of the present invention.
9 shows a material fractionation coefficient calculated according to an embodiment of the present invention.

Since the present invention can have various changes and can have various embodiments, specific embodiments will be described in detail with reference to the drawings. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numerals have been used for like elements.

Terms such as first, second, A, and B may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. and/or includes a combination of a plurality of related description items or any of a plurality of related description items.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it should be understood that other components may exist in between. something to do. On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

It should also be understood that the terms "first" and "second" are used herein for distinguishing purposes only, and are not meant to indicate or anticipate sequences or priorities in any way.

Throughout this specification, “base” may refer to image data divided into several pieces of image data.

Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Throughout the specification and claims, when a part includes a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

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

Figure 1 shows a calibration phantom device according to an embodiment of the present invention, Figure 2 shows a calibration phantom device according to another embodiment of the present invention.

1 and 2 , the calibration phantom device according to an embodiment of the present invention includes at least two or more plurality of subject phantoms made of a single material, and each of the plurality of subject phantoms is made of a different material. can be done

In an embodiment of the present invention, the plurality of subject phantoms are phantoms for calibration used to secure a database for calibrating the material discrimination coefficient.

Materials constituting each of the plurality of subject phantoms according to an embodiment of the present invention may be selected as four representative materials in each region when all kinds of materials are divided based on density and atomic number. For example, the plurality of subject phantoms may include acrylic phantoms 101 and 201 , aluminum phantoms 102 and 202 , iron phantoms 103 and 203 , and lead phantoms 104 and 204 , respectively, but are not limited thereto.

The plurality of subject phantoms according to an embodiment of the present invention may be configured to have a stacked structure in a direction perpendicular to a direction in which X-rays are irradiated.

X-rays may be generated from the X-ray source 106 and irradiated to the calibration phantom device 1000 through the collimator 107 . On the other hand, the collimator may be installed in front of the beam outlet or detector of the X-ray source 106 to block an area outside the irradiation range of X-rays emitted from the X-ray source 106 .

X-rays irradiated by the calibration phantom apparatus 1000 may be vertically incident on the side surfaces of the phantoms 101 , 102 , 103 , and 104 to be inspected. In more detail, X-rays may be incident on the dotted line portion of the side surface of the column of the phantom under test ( 101 , 102 , 103 , 104 ).

Transmission images passing through the subject phantoms 101 , 102 , 103 , and 104 may be acquired by the detector. The detector and the X-ray source 106 may be disposed to face the X-ray source so that the subject is interposed between the detector and the X-ray source 106 (not shown).

The subject phantoms according to an embodiment of the present invention may be formed of elliptical pillars 101, 102, 103, and 104 as shown in FIG. 1, or circular pillars 201, 202, 203, 204).

According to an embodiment of the present invention, the subject phantoms are formed of oval pillars 101, 102, 103, 104 or circular pillars 201, 202, 203, and 204, so that the thickness of the subject phantom is from a thin portion to a thick portion. A lot of data can be obtained for various thicknesses of In addition, since the phantoms to be inspected are formed in an elliptical column or a circular column, there is an advantage that data for various thicknesses form a Gaussian distribution, and data can be uniformly obtained.

On the other hand, if the subject phantom is formed in a triangle or a rectangle, there may be a disadvantage in that only data for a specific thickness is obtained.

The calibration phantom apparatus according to an embodiment of the present invention may further include motors 105 and 205 for rotating the plurality of phantoms 101, 102, 103, 104, 201, 202, 203, and 204. have.

The motors 105 and 205 according to an embodiment of the present invention may be disposed on the same axis as the direction in which the phantoms to be inspected are stacked. The motor may rotate 360 degrees while performing a uniform circular motion.

The X-ray detector captures a transmission image passing through each of the phantoms of the subject while also rotating the phantoms of the subject according to the rotation of the motors 105 and 205 . Through this transmission image, it is possible to obtain a material discrimination coefficient for a change in the thickness of a material constituting each phantom of the subject.

A database for each material may be constructed by acquiring material classification coefficients for the obtained various thickness changes.

Meanwhile, the material classification coefficient may be obtained by rotating each of the plurality of subject phantoms in order, or the material classification coefficient for each material may be simultaneously obtained while rotating the plurality of subject phantoms at once.

3 shows a block diagram of a calibration phantom system according to an embodiment of the present invention.

The calibration phantom system according to an embodiment of the present invention may calculate material discrimination coefficients using a phantom transmission image obtained using the calibration phantom device shown in FIGS. 1 and 2 and form a database.

Referring to FIG. 3 , the calibration phantom system according to an embodiment of the present invention may include a calibration phantom apparatus 1000 and a material fractionation coefficient calculating apparatus 2000, and the material fractionation coefficient calculating apparatus 2000 is a transmission image It may include a receiving unit 2100 , an attenuated image data calculating unit 2200 , a basis generating unit 2300 , an image reconstruction unit 2400 , and a material discrimination coefficient calculating unit 2500 .

4 shows a flow chart of a method for fractionating a substance using a calibration phantom system according to an embodiment of the present invention.

The method for classifying a substance using dual energy X-rays includes: an X-ray detector acquiring a phantom transmission image of a subject irradiated from an X-ray source, and receiving the transmission image by the transmission image receiving unit 2100 (a, S100); obtaining, by the attenuated image data calculating unit 2200 of the material classification coefficient calculation apparatus 2000, the attenuated image data by log-transforming the phantom transmission image of the subject with respect to a background signal (b, S200);

generating, by the basis generator 2300, a basis by dividing the attenuated image data into a plurality of image data based on a plurality of step-by-step thresholds (c, S300); Reconstructing image data based on the generated basis by the image reconstruction unit 2400 (d, S400); and calculating, by the material classification coefficient calculator 2500, a material classification coefficient from the reconstructed image data (e, S500).

In the method for material fractionation using dual energy X-rays according to an embodiment of the present invention, the calculated material fractionation coefficient is converted into a database, and finally, the material fractionation coefficient constructed in the database for a newly photographed subject is used to classify matter. can be performed.

In the method of material classification for an X-ray photographed subject, an image may be divided based on a log-transformation attenuation method according to an embodiment of the present invention, and material classification may be performed using the constructed material classification coefficient.

On the other hand, the conventional technique may be applied to a method of performing substance fractionation using the established substance fractionation coefficient.

5 shows a plurality of step-by-step thresholds according to an embodiment of the present invention, and FIG. 6A shows a method of dividing the image data into a plurality of image data according to an embodiment of the present invention. FIG. 6B shows separated image data for all materials divided by each material.

A method of dividing an image based on an attenuation technique and constructing a database for material discrimination coefficients according to an embodiment of the present invention will be described with reference to FIGS. 5 and 6A .

The attenuation technique according to an embodiment of the present invention refers to a technique for attenuating a phantom transmission image of a subject by logarithmic transformation with respect to a background signal, and in more detail, it may be performed through Equation 1 below.

Here, a denotes a background signal and b denotes a transmitted image signal.

According to an embodiment of the present invention, the attenuated image data calculated through the above equation is divided into several image data. Image data separated into several pieces of image data may be referred to as “base” throughout this specification. The present invention is characterized in that the material fractionation is performed using the separated basis of the damping basis.

A method of generating a basis by dividing into several images based on an attenuation method according to an embodiment of the present invention will be described with reference to FIGS. 5 and 6A .

As shown in FIG. 5, when there is a data distribution from the lowest value (eg, 0) to the largest value (eg, n) of the attenuated image data, n sections are sequentially divided at a predetermined interval to a plurality of (n) steps Set the threshold.

And as shown in Figures 6a and 6b, when each pixel value of the attenuated image data corresponds to any one of the sections, only the attenuated image data value of the corresponding pixel is maintained and the remaining pixels are set to 0, A basis is generated by dividing the image data by the number of thresholds for each step.

More specifically, in the separated image a1 for the period 0 and 1, only pixels having a value of 0 or more and less than 1 maintain the value, the remaining pixels are set to 0, and the separated image a1 between the period n-1 and n is set to 0. an maintains a value of only pixels having a value greater than n-1 and less than or equal to n, and the remaining pixels are set to 0, so that n pieces of separated image data are output.

FIG. 6B shows the separated image data for all materials divided by each material, and separated data for an acrylic material 501 , an aluminum material 502 , an iron material 503 , and a lead material 504 . shows

Meanwhile, an embodiment of the present invention uses dual energy X-rays including high energy and low energy. In general, a signal using a high-energy source has a higher signal. After dividing the attenuation value based on the high-energy image, the low-energy image is separated based on the attenuation by using the spatial information of the divided data. That is, the basis separation technique according to an embodiment of the present invention is performed based on a low energy image.

,

라 할 때 로그변환된 감쇠 영상 데이터는 아래 수학식 2(저에너지 영상), 수학식 3(고에너지 영상)으로 구할 수 있다.When explaining in more detail by synthesizing the above, the obtained transmitted image is

,

The log-transformed attenuated image data can be obtained by Equation 2 (low energy image) and Equation 3 (high energy image) below.

The attenuation-based basis generation technique is performed only on low-energy images. According to an embodiment of the present invention, the attenuation-based separated basis may be reconstructed into several tomographic images, and may be performed for each phantom of the subject. Image reconstruction is reconstructed through 2D Filter Back Projection. The sum of all the separated base images is mathematically the same as the reconstruction image of the data of the existing non-separated image.

라 할 때 재건된 영상을 다음 수학식 4와 같이 표현할 수 있다.Transmission image separated based on attenuation

, the reconstructed image can be expressed as in Equation 4 below.

은 라돈 변환을 가리키고

는 그것의 역변환으로 일반적인 재건을 의미한다. 또,

은 1에서 N의 값을 가지고 모두가 N개의 기저를 나타낸다. 고에너지 영상에 대해서는 분리 영상을 구성하지 않고 재건영상을 구한다. 고에너지 영상에 대한 재건 영상은 아래 수학식 5와 같이 표현할 수 있다.here

indicates radon transformation

means a general reconstruction by its inverse transformation. In addition,

has values from 1 to N, all representing N bases. For high-energy images, a reconstruction image is obtained without constructing a separate image. The reconstruction image for the high-energy image can be expressed as in Equation 5 below.

7 to 8 show images reconstructed based on the separated base according to an embodiment of the present invention.

7A and 7B show an image reconstructed based on the basis of the acrylic phantom 101. FIG. 7A shows a high-energy image to which an attenuation technique is applied, and FIG. 7B is a separate low-energy basis image based on attenuation. show

Table 1 below shows the step-by-step thresholds used in the basal separation technique applied to FIG. 7B .

Basis One 2 3 4 5 Threshold value (c) -0.808724 -0.814247 -0.817843 -0.821842 -0.827337

8A and 8B show an image reconstructed based on the base for the iron phantom 101, FIG. 8A shows a high-energy image to which an attenuation technique is applied, and FIG. 8B shows a separated low-energy base image based on attenuation. show

Table 2 below shows the step-by-step thresholds used in the basal separation technique applied in FIG. 8B .

Basis One 2 3 4 5 Threshold value (c) -0.814218 -0.827726 -0.835303 -0.843476 -0.854032

The algorithm of the material fractionation method according to an embodiment of the present invention calculates a substance fractionation coefficient from each base data, and determines the substance fractionation coefficient for all substances included in the calibration phantom device.

The cost function (E) for determining the material classification coefficient using the high-energy image and the low-energy basis image obtained as described above is expressed in Equation (6) below.

는 영상의 공간 좌표를 나타내고

는 물질분별 계수를 나타낸다. here

represents the spatial coordinates of the image.

represents the substance fractionation coefficient.

The cost function (E) can be analytically determined by setting the differential equation for the material classification coefficient to 0. That is, a coefficient that minimizes the sum of the product of each base value and the material classification coefficient may be determined as the material classification coefficient.

If this process is applied equally to all material phantoms, the calibration coefficient for each material can be obtained. The material fractionation coefficient obtained above always has a value less than 1 because the attenuation of low energy is always greater than that of high energy. And this can be interpreted as the damping ratio at the corresponding base of the corresponding material.

9 shows a material fractionation coefficient calculated according to an embodiment of the present invention.

Referring to FIG. 9 , according to an embodiment of the present invention, it is possible to obtain several material classification coefficients even for the same material. That is, since a material fractionation coefficient can be obtained for one type of material as many as the number of bases separated according to an embodiment of the present invention, the present invention more precisely corrects other material fractionation coefficients according to the difference in thickness and density of the material. There are advantages to doing.

As described above, after completing the material classification coefficient calibration work to build a database for the material fractionation coefficient, a cargo object is photographed to perform material classification on the object.

In the same manner as in the method according to an embodiment of the present invention, a low-energy image is separated based on attenuation for a transmission image of a cargo subject. In addition, for a pixel coordinate of one specific image data, a material discrimination coefficient in which the attenuation of the coordinate is most similar to the attenuation ratio of the low-energy and high-energy image calculated based on the corresponding basis is found from the established database.

When a material classification coefficient most similar to the previously stored material classification coefficient is found, a material label to which the material classification coefficient belongs is allocated to the pixel position of the cargo object transmission image. Material classification for cargo objects means performing the material labeling process for all image coordinates.

The above description is merely illustrative of the technical idea of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

1000: calibration phantom device
101, 201: Acrylic Phantom
102, 202: aluminum phantom
103, 203: Iron Phantom
104, 204: lead phantom
105, 205: motor
106: X-ray source
107: collimator
2000: Substance fractionation coefficient calculation device
2100: transmitted image receiving unit
2200: attenuated image data calculation unit
2300: base generator
2400: image reconstruction unit
2500: substance classification coefficient calculation unit

Claims (16)

In the calibration phantom device,
It comprises at least two or more plurality of subject phantoms made of a single material, wherein each of the plurality of subject phantoms is made of a different material,
The calibration phantom apparatus having a structure in which the plurality of phantoms to be examined are stacked in a direction perpendicular to a direction in which X-rays are irradiated. According to claim 1,
The plurality of test subject phantoms are an oval column or a circular column, characterized in that the calibration phantom device According to claim 1,
The plurality of subject phantoms may include: a first subject phantom made of a single material;
and a second subject phantom made of a material different from that of the first subject phantom,
A radius of the second phantom under test is smaller than a radius of the phantom under test. According to claim 1,
The calibration phantom device, characterized in that the thickness of each of the plurality of phantoms to be examined is different from each other. According to claim 1,
Further comprising a motor rotating the plurality of subject phantoms,
The motor is disposed on the same axis as the direction in which the plurality of subject phantoms are stacked,
Calibration phantom device, characterized in that the plurality of subject phantoms rotate according to the rotation of the motor In the calibration phantom system,
The calibration phantom device according to any one of claims 1 to 5, and
A material fractionation coefficient calculation device,
The material fractionation coefficient calculation device is
a transmission image receiver configured to receive a phantom transmission image of the subject obtained from the X-ray detector;
an attenuated image data calculator configured to log-transform the received phantom transmission image with respect to a background signal to calculate attenuated image data;
a basis generator for generating a basis by dividing the calculated attenuated image data into a plurality of image data based on a plurality of step-by-step thresholds;
an image reconstruction unit for reconstructing image data based on the generated basis; and
Calibration phantom system comprising a material discrimination coefficient calculating unit for calculating a material classification coefficient from the reconstructed image data. 7. The method of claim 6,
When the number of the plurality of step-by-step thresholds is n,
The transmission image receiving unit, the attenuated image data calculating unit, the basis generating unit, the image reconstruction unit, and the material discrimination coefficient calculating unit are all performed for each of the plurality of m subject phantoms, so that the material discrimination coefficient is (mxn) ) Corrective phantom system, characterized in that dogs are calculated. 7. The method of claim 6,
The attenuated image data calculation unit,
A calibration phantom system that calculates attenuated image data through the following equation.
Attenuated image data = -log(b/a)
(Here, a is the background signal and b is the transmitted image signal.) 7. The method of claim 6,
The basis generator,
The plurality of step-by-step thresholds are sequentially configured at predetermined intervals to form a plurality of sections,
When the value of each pixel of the attenuated image data corresponds to any one of the plurality of sections,
By outputting image data in which only the attenuated image data value of the corresponding pixel is maintained and the remaining pixels are 0, image data corresponding to the number of the plurality of sections is output,
Calibration phantom system, characterized in that dividing the output image data into image data for the plurality of sections. 7. The method of claim 6,
The calibration phantom system, characterized in that the image reconstruction unit is performed for each image data separated for each threshold section. In the material fractionation method using dual energy X-rays,
(a) acquiring, by an X-ray detector, a phantom transmission image of a subject irradiated from an X-ray source;
(b) obtaining, by an apparatus for calculating a material classification coefficient, attenuated image data by log-transforming the phantom transmission image of the subject with respect to a background signal;
(c) generating, by the apparatus for calculating the material discrimination coefficient, a basis for the attenuated image data by dividing the attenuated image data into a plurality of image data based on a plurality of step-by-step thresholds;
(d) reconstructing the image data based on the generated basis by the material classification coefficient calculating device; and
and (e) calculating, by the apparatus for calculating the material fractionation coefficient, a material fractionation coefficient from the reconstructed image data. 12. The method of claim 11,
When the number of the plurality of step-by-step thresholds is n,
The above steps are all performed for each of the plurality of m subject phantoms, so that (mxn) material discrimination coefficients are calculated. 12. The method of claim 11,
Step (b) of obtaining the attenuated image data,
A material fractionation method using dual energy X-rays to be obtained through the following equation.
Attenuated image data = -log(b/a)
(Here, a is the background signal and b is the transmitted image signal.) 12. The method of claim 11,
Step (c) of generating the basis,
The plurality of step-by-step thresholds are sequentially configured at predetermined intervals to form a plurality of sections; and
When the value of each pixel of the attenuated image data corresponds to any one of the plurality of sections,
outputting image data equal to the number of the plurality of sections by maintaining only the attenuated image data value of the corresponding pixel and outputting image data in which the remaining pixels are 0; and
and dividing the output image data into image data for the plurality of sections. 12. The method of claim 11,
The step (d) of reconstructing the separated plurality of image data is performed for each separated image data for each threshold section. In the material fractionation coefficient calculation device,
an attenuated image data calculator configured to log-transform the phantom transmission image of the subject received from the X-ray detector with respect to a background signal to calculate attenuated image data;
a basis generator for generating a basis by dividing the calculated attenuated image data into a plurality of image data based on a plurality of step-by-step thresholds;
an image reconstruction unit for reconstructing image data based on the generated basis; and
and a material fractionation coefficient calculator configured to calculate a material fractionation coefficient from the reconstructed image data.

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