KR20130127356A - X-ray image apparatus and control method for the same - Google Patents

Abstract

One aspect of an X-ray image device and a controlling method thereof provides the X-ray image device and the controlling method thereof generating an X-ray image with reduced noise by calibrating errors according to the feature of each pixel. The present invention discloses the X-ray image device comprising an X-ray generating part generating and radiating X-ray; an X-ray detecting part detecting the X-ray and counting the number of photons having energy above threshold energy by pixel for outputting X-ray data; a function acquiring part acquiring a calibration function by pixel through using X-ray data for a plurality of phantoms designed in advance; and an image calibrating part calibrating the X-ray image of an object by pixel through using the acquired calibration function. [Reference numerals] (110) X-ray generation unit;(120) X-ray detection unit;(131) Function obtaining unit;(132) Function storage unit;(133) Image revising unit;(134) Image processing unit;(140) Display unit

Description

X-RAY IMAGE APPARATUS AND CONTROL METHOD FOR THE SAME

The present invention relates to an X-ray imaging apparatus for generating X-ray images by transmitting X-rays to an object and a control method thereof.

An X-ray imaging apparatus is an apparatus that may radiate X-rays to an object and acquire an internal image of the object by using X-rays transmitted through the object. Since the transmittance of the X-rays differs depending on the characteristics of the material constituting the object, the intensity or intensity of the X-rays transmitted through the object can be detected to image the internal structure of the object.

Specifically, when the X-ray generator generates X-rays and irradiates the object, the X-ray detector detects X-rays passing through the object and converts the detected X-rays into electrical signals. Since the electrical signal is converted for each pixel, one X-ray image may be obtained by combining electrical signals corresponding to each pixel.

In the past, a method of accumulating electrical signals for a certain period of time has been mainly applied. Recently, a photon counting detector (PCD) has been developed, which separates the detected X-rays by energy.

PCD has the advantage of being able to separate a specific material from X-ray image and less X-ray exposure and noise.However, PCD is affected by the characteristics of light-receiving element or read-out circuit of each pixel. Even if X-rays are incident, different counter values may be output for each pixel, which causes noise in the image.

An aspect of an X-ray imaging apparatus and a control method thereof provides an X-ray imaging apparatus for generating an X-ray image with reduced noise by correcting an error according to a characteristic of each pixel and a control method thereof.

An X-ray imaging apparatus according to an aspect of the disclosed invention X-ray generation unit for generating and radiating X-rays; An X-ray detector for detecting the X-rays and counting the number of photons having energy above a threshold energy among the photons included in the detected X-rays for each pixel to output X-ray data; A function obtaining unit obtaining a calibration function for each pixel by using X-ray data of a plurality of previously designed phantoms; And an image corrector configured to correct the X-ray image of the object for each pixel by using the obtained calibration function.

The function acquisition unit may include: a measurement value storage unit configured to store the X-ray data output by detecting the X-rays transmitted by the X-ray generator through the phantom by the X-ray generator; And an operation unit configured to perform an operation for obtaining the calibration function using the X-ray data stored in the measurement value storage unit.

The function obtaining unit may divide the plurality of phantoms into at least two phantom sets, and obtain the calibration function for each phantom set.

The image corrector may generate at least two corrected X-ray images by applying a calibration function acquired for each phantom set to the X-ray image of the object.

The image corrector may generate one corrected X-ray image by synthesizing the two corrected X-ray images.

According to an aspect of the present invention, there is provided a method of controlling an X-ray imaging apparatus, the method including: obtaining a calibration function for each pixel using X-ray data of a plurality of pre-designed phantoms; Irradiating X-rays on the object and detecting X-rays passing through the object to obtain an X-ray image of the object; And correcting the X-ray image of the object for each pixel by using the obtained calibration function.

According to an aspect of the X-ray imaging apparatus and a method of controlling the same, an error according to characteristics of each pixel may be corrected by calculating and storing a mapping function for correcting an error for each pixel and applying a mapping function to an output value of each pixel.

1 illustrates an overall appearance of an X-ray imaging apparatus for mammography according to an exemplary embodiment of the present disclosure.
2 is a control block diagram of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.
3 is a diagram schematically illustrating a structure of an X-ray detector of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.
FIG. 4A is a diagram schematically illustrating a structure of a single pixel area of the X-ray detector illustrated in FIG. 3.
FIG. 4B is a diagram schematically illustrating a structure of a single pixel area capable of separating the detected X-rays according to a plurality of energy bands.
5A shows an example of an energy spectrum of X-rays radiated from the X-ray generator.
FIG. 5B illustrates an ideal spectrum when the X-ray detector divides the X-ray of FIG. 4A for each energy band.
6 shows an example of a graph and a theoretical graph measuring the standardized X-ray intensity for each threshold energy.
FIG. 7 is a control block diagram illustrating a configuration of a controller in the X-ray imaging apparatus according to the exemplary embodiment of the present disclosure.
8A illustrates a schematic structure of X-ray data output from each pixel of the X-ray detector of the X-ray imaging apparatus according to the exemplary embodiment of the present disclosure.
8B illustrates a schematic structure of data stored in a function acquisition unit of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.
9 is a diagram schematically illustrating a structure of data stored in a function storage unit.
FIG. 10 is a diagram schematically illustrating a structure of data stored in a measurement value storage unit when a calibration function is acquired for each condition.
FIG. 11 is a diagram schematically illustrating a structure of data stored in a function storage unit when a calibration function is acquired for each condition.
12 is a control block diagram of an X-ray imaging apparatus according to another exemplary embodiment of the present disclosure.
FIG. 13 is a diagram schematically illustrating a structure of data stored in a function storage unit of an X-ray imaging apparatus according to another exemplary embodiment of the present disclosure.
14 is a cross-sectional view showing the internal tissue configuration of the breast.
15 is a flowchart illustrating a control method of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.
FIG. 16 is a flowchart illustrating a process of obtaining and storing a calibration function for each energy per pixel.
17 is a flowchart illustrating a control method of an X-ray imaging apparatus according to another exemplary embodiment of the present disclosure.

Hereinafter, embodiments of an X-ray imaging apparatus and a control method thereof will be described in detail with reference to the accompanying drawings.

1 illustrates an overall appearance of a mammography X-ray imaging apparatus according to an exemplary embodiment of the present disclosure, and FIG. 2 illustrates a control block diagram of the X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.

The X-ray imaging apparatus may photograph various objects, and the structure of the X-ray imaging apparatus may vary slightly depending on the photographing target. Although the X-ray imaging apparatus according to the present disclosure does not limit the subject to be photographed, FIG. 1 illustrates an X-ray imaging apparatus for mammography as an example for detailed description.

1 and 2, the X-ray imaging apparatus 100 according to an exemplary embodiment of the present disclosure detects an X-ray generating unit 110, X-rays passing through an object, and generates an X-ray and radiates an electric signal. The X-ray detector 120 that obtains the X-ray data by converting the data into an X-ray data, stores a calibration function for correcting an error according to the characteristics of each pixel, and applies a calibration function stored in advance to the X-ray data obtained when the actual object is photographed. And a controller 130 to calibrate.

The X-ray generator 110 generates an X-ray to irradiate the object. When the object 30 is a breast composed of only soft tissue, compression in the vertical direction is required to obtain a clearer and more accurate image. Therefore, the object 30 is positioned between the compression paddle 107 and the X-ray detector 120 and X-rays are irradiated while the object 30 is compressed with the compression paddle 107. The X-ray generator 110, the X-ray detector 120, and the compression paddle 107 may be supported by the housing 101.

The X-ray generator 110 generates an X-ray to irradiate the object. The X-ray generator 110 generates X-rays by receiving power from a power supply (not shown), and energy of X-rays may be controlled by a tube voltage, and intensity or dose of X-rays may be controlled by tube current and X-ray exposure time. Can be.

The X-ray generator 110 may irradiate monochromatic X-rays or polychromatic X-rays, but in this embodiment, the X-ray generator 110 irradiates multi-colored X-rays having a predetermined energy band. The energy band of X-rays to be irradiated is defined by an upper limit and a lower limit.

The upper limit of the energy band, that is, the maximum energy of the irradiated X-rays can be controlled by the magnitude of the tube voltage, and the lower limit of the energy band, that is, the minimum energy of the irradiated X- Lt; / RTI > By filtering the X-rays of the low-energy band using a filter, the average energy of the X-rays to be irradiated can be increased.

The X-ray imaging apparatus 100 is provided with an AEC (Auto Exposure Controller) to detect at least one of X-ray irradiation parameters such as tube voltage, tube current, target material of the anode, exposure time, threshold energy, You can adjust the parameters. This is for optimizing X-ray irradiation conditions to an actually photographed object, and AEC may set a parameter optimized for characteristics of the object by analyzing a pre-shot image of the object.

The X-ray detector 120 detects the X-rays transmitted through the object and converts the detected X-rays into electrical signals to acquire X-ray data.

In general, the X-ray detector may be classified according to a material composition method, a method of converting the detected X-rays into an electrical signal, and a method of obtaining X-ray data.

First, the X-ray detector is classified into a case consisting of a single device and a case of a hybrid device according to a material construction method.

In the case of a single element, a portion that detects X-rays and generates an electrical signal and a portion that reads and processes the electrical signal may be formed of a semiconductor of a single material or manufactured in a single process. This is a case where a single device, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), is used.

In the case of a hybrid device, a portion for detecting an X-ray and generating an electrical signal and a portion for reading and processing the electrical signal are formed of different materials or manufactured by different processes. For example, when an X-ray is detected using a photodiode, a CCD, or a CdZnTe and an electrical signal is read and processed using a CMOS ROIC (Read Out Integrated Circuit), a strip detector is used to detect the X- When reading and processing electrical signals using ROIC, and when using an a-Si or a-Se flat panel system.

The X-ray detector is classified into a direct conversion method and an indirect conversion method according to a method of converting X-rays into electrical signals.

In the direct conversion method, when X-rays are irradiated, electron-hole pairs are temporarily generated inside the light receiving element, and electrons move to the anode and the hole moves to the cathode by the electric field applied to both ends of the light receiving element. Is converted into an electrical signal. Materials used in the light receiving device in the direct conversion method include a-Se, CdZnTe, HgI ₂ , PbI _2, and the like.

In the indirect conversion method, a scintillator is provided between the light receiving element and the X-ray generating unit, and when the X-ray irradiated from the X-ray generating unit reacts with the scintillator to emit photons having a wavelength in the visible region, the light receiving element detects the photon. To convert it into an electrical signal. In the indirect conversion method, a-Si is used as a light-receiving element. As the scintillator, a GADOX scintillation thin film, a micro-columnar or needle-structured CSI (T1) is used.

In addition, the X-ray detector may include a charge integration mode for storing a charge for a predetermined time and then obtaining a signal therefrom according to a method of acquiring X-ray data and a threshold energy whenever a signal is generated by a single X-ray photon. photon counting mode for counting photons having energy above the threshold energy.

The X-ray imaging apparatus 100 according to the exemplary embodiment of the present invention uses a photon counting method in which the X-ray exposure amount of the object and the noise of the X-ray image are smaller than the charge accumulation method. Therefore, the X-ray detector 120 is implemented with a PCD (Photon Counting Detector).

On the other hand, the material configuration method of the X-ray detection unit 120 and the method of converting the electrical signal is not limited, but in the embodiments to be described below, for the convenience of description, a direct conversion method for directly acquiring an electrical signal from the X-ray and light receiving for detecting X-rays A specific embodiment will be described by applying a hybrid method in which an element and a read circuit chip are combined.

The host device 140 includes a display unit 141 that displays the generated X-ray image and an input unit 142 that receives various commands related to the operation of the X-ray imaging apparatus 100 from a user. In addition, a process of generating an X-ray image using the X-ray data transmitted from the X-ray detector 120 may be performed, which is possible when the controller 130, which will be described later, is provided in the host device 140. However, embodiments of the disclosed invention are not limited thereto, and the position where the control unit 130 is provided is not limited as long as it can perform a function described below.

3 is a diagram schematically illustrating a structure of an X-ray detector of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.

Referring to FIG. 3, the X-ray detector 120 includes a light receiving element 121 that detects X-rays and converts the X-rays into electrical signals, and a read circuit chip 122 that reads electrical signals. Here, the read circuit chip 122 is formed in the form of a two-dimensional pixel array including a plurality of pixel regions. As the material of the light receiving element 121, a single crystal semiconductor material can be used to secure high resolution, fast response time, and high dynamic range at low energy and small dose. The single crystal semiconductor material used here includes Ge, CdTe, CdZnTe, GaAs and the like.

The light receiving element 121 can be formed in the form of a PIN photodiode by bonding a p-type layer 121c in which a p-type semiconductor is arranged in a two-dimensional pixel array structure to a lower portion of the n-type semiconductor substrate 121b having a high resistance, The reading circuit chip 122 using the CMOS process is coupled to the light receiving element 121 for each pixel. The CMOS readout circuit 122 and the light receiving element 121 may be coupled in a flip chip bonding method to form a bump 123 such as solder (PbSn), indium (In), and then reflow and heat. It can be combined by pressing and pressing. However, the above-described structure is only an embodiment of the x-ray detector 120, and the structure of the x-ray detector 120 is not limited thereto.

4A is a diagram schematically illustrating the structure of a single pixel region of the X-ray detector illustrated in FIG. 3, and FIG. 4B is a diagram schematically illustrating a structure of a single pixel region capable of separating the detected X-rays by a plurality of energy bands. The figure is shown.

Referring to FIG. 4A, when a photon of X-rays is incident on the light receiving element 121, electrons in the household appliance band receive the energy of the photons and are excited as a conduction band beyond the band gap energy difference. This results in electron-hole pairs in the depletion region.

When metal electrodes are formed on the P-type layer and the n-type substrate of the light receiving element 121 and subjected to reverse bias, electrons of the electron-hole pairs generated in the depletion region are attracted to the n-type region and holes to the p-type region. . Holes drawn into the p-type region are input to the readout circuit 122 through the bump bonding 123 to read the electrical signal generated by the photons. However, it is also possible to generate electrons by inputting electrons into the readout circuit 122 according to the structure of the light receiving element 121 and the voltage applied to them.

The read circuit 122 may be formed in a two-dimensional pixel array structure corresponding to the p-type semiconductor of the light receiving element 121, and read out an electrical signal for each pixel. When charge is input from the light receiving element 121 to the readout circuit 122 through the bump bonding 123, the input charge generated from one photon in the pre-amplifier 122a of the readout circuit 122 is received. It accumulates and outputs a voltage signal corresponding thereto.

The voltage signal output from the preamplifier 122a is transmitted to the comparator 122b. The comparator compares the externally controllable threshold voltage with the input voltage signal and outputs a '1' or ' And outputs a pulse signal of '0'. The counter 122c counts the number of times '1' is output, and outputs the X-ray data in digital form. By combining the X-ray data for each pixel, an X-ray image of the object may be obtained.

Here, the threshold voltage corresponds to a threshold energy, and when the number of photons having energy equal to or greater than E is counted, the threshold voltage corresponding to the threshold energy E is input to the comparator 122b. The threshold energy and the threshold voltage can be matched because the magnitude of the electrical signal (voltage) generated in the light receiving element varies according to the energy of the photons. Accordingly, a threshold voltage corresponding to a desired threshold energy may be calculated using a relationship between energy of photons and a generated voltage, and inputting the threshold energy into the X-ray detector 120 in the following embodiment corresponds to the threshold energy. It may be used in the same sense as inputting a threshold voltage.

In order to improve contrast between internal materials of the object, multiple energy X-ray images may be generated by acquiring X-ray images of a plurality of different energy bands. In this case, in order to obtain X-ray images of a plurality of different energy bands, X-rays may be irradiated a plurality of times by varying energy bands, but the X-ray imaging apparatus 100 according to an exemplary embodiment of the present disclosure may include an X-ray detector 120. Is implemented as a PCD, the X-ray generator 110 irradiates broadband X-rays including a plurality of energy bands only once, and the X-ray detector 120 separates the detected X-rays for each of the plurality of energy bands.

To this end, as shown in FIG. 4B, a plurality of comparators and counters are compared to count photons for each of a plurality of energy bands. In the example of FIG. 4B, three comparators are provided. However, the embodiment of the disclosed invention is not limited thereto, and a comparator may be provided according to the number of energy bands to be separated.

Referring to FIG. 4B, when electrons or holes generated by a single photon are input to the preamplifier 122a and output as voltage signals, the voltage signals are input to three comparators 122b-1, 122b-2, and 122b-3. . When the threshold voltage 1 (V _th1 ) to the threshold voltage 3 (V _th3 ) are input to the respective comparators, the comparator 1 (122b-1) compares the threshold voltage 1 with the input voltage. And counts the number of generated photons. In the same manner, the counter 2 counts the number of photons that generate a voltage higher than the threshold voltage 2, and the counter 3 counts the number of photons that generate a voltage that is higher than the threshold voltage 3.

5A shows an example of an energy spectrum of X-rays radiated from the X-ray generator, and FIG. 5B shows an ideal spectrum when the X-rays of FIG. 4A are separated by energy bands in the X-ray detector.

The energy of X-rays irradiated by the X-ray generator 110 varies according to the object. When the object is a breast, as shown in FIG. 5A, X-rays having a lower limit of energy of 10 keV and an upper limit of energy of 50 keV are generated. Can be investigated. To this end, X-rays may be generated with a tube voltage of 50 kVp and X-rays may be irradiated by filtering low energy bands (about 0-10 kev). At this time, the dose of X-rays (number of photons) represented by the y-axis can be controlled by the tube current and the X-ray exposure time.

And it can be separated by a three-band energy (E _{band1, band2} E, E _band3) as shown in Figure 5b the X-ray detected by the X-ray detection unit 120. To this end, a voltage corresponding to E _{1 and min} is calculated and input to the comparator 1 122b-1 of FIG. 4B as a threshold voltage, and a voltage corresponding to E _{2 and min} is calculated to the comparator 2 122b-2. The threshold voltage may be input, and a voltage corresponding to E _{3 and min} may be calculated and input to the comparator 3 122b-3 as the threshold voltage.

Theoretically, the magnitude of the voltage signal generated in each pixel of the x-ray detector 120 should be influenced only by the energy of the incident photons, but may also be influenced by the characteristics of the light receiving element of each pixel and the characteristics of the reading circuit. Therefore, even if photons having the same energy are incident on all pixels, the magnitude of the voltage signal generated in a single photon may vary according to the pixel-specific characteristics.

As a specific example, when the characteristics of the light receiving element are different for each pixel or the characteristics of the preamplifier are different, there may be an error in the X-ray data output from the counter when there is an error in the signal input or output to the preamplifier.

6 shows an example of a graph and a theoretical graph measuring the standardized X-ray intensity for each threshold energy.

Referring to FIG. 6, an error may occur between the standard X-ray intensity curve measured while changing the threshold energy and the theoretical standard X-ray intensity curve under the same conditions.

For example, if the value to be input as the threshold energy is E, that is to count the number of photons with energy above E, the theoretical standard x-ray intensity for the threshold energy E is m ₂ , The standard x-ray intensity measured when input with energy can be m ₁ .

Comparing the measured standard X-ray intensity curve with the theoretical standard X-ray intensity curve, the threshold energy must be inputted as E 'in order to obtain the theoretical standard X-ray intensity m ₂ corresponding to the threshold energy E or more under the same conditions through the X-ray detector. It can be seen.

The X-ray imaging apparatus 100 according to the exemplary embodiment of the present disclosure may correct the threshold energy according to the pixel-specific characteristics by changing the structure of the X-ray detector 120 in hardware. However, in order to minimize design complexity, the correction scheme may not be applied, and even if the threshold energy is corrected for each pixel, precise correction may not be performed due to the limitation of the number of bits allocated to each pixel.

Accordingly, the controller 130 estimates a calibration function for correcting X-ray data for each pixel in advance using the data measured for the phantom, and applies a calibration function for each pixel to the X-ray data obtained by photographing the actual object. Correct the X-ray image.

FIG. 7 is a control block diagram illustrating a configuration of a controller in the X-ray imaging apparatus according to the exemplary embodiment of the present disclosure.

Referring to FIG. 7, the controller 130 may include a function acquisition unit 131 for acquiring a calibration function for each pixel, a function storage unit 132 for storing the obtained calibration function, and X-ray data obtained by photographing an actual object. The image correction unit 133 applies a pixel-by-pixel calibration function and an image processor 134 which performs image processing for image enhancement on the corrected image and outputs the image through the display unit 141.

The function acquirer 131 obtains a calibration function for correcting the X-ray data output from the X-ray detector 120. The acquisition of the calibration function is performed before the actual object is photographed. The calibration function may be acquired once before using the X-ray imaging apparatus 100, may be performed at regular intervals, or may be arbitrarily performed at every component replacement or without a predetermined cycle. The X-ray imaging apparatus 100 according to an exemplary embodiment of the present disclosure does not limit the timing or number of times of obtaining a calibration function.

The function storage unit 132 stores the calibration function obtained by the function obtaining unit 131 for each pixel and the threshold energy, so that the function storage unit 132 can be used to correct an image of an actual object. Hereinafter, operations of the function acquisition unit 131 and the function storage unit 132 will be described in detail.

FIG. 8A illustrates a schematic structure of X-ray data output from each pixel of an X-ray detector of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure, and FIG. 8B illustrates a function of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure. A schematic structure of the data stored in the acquisition section is shown.

X-ray data is data output from each pixel, and represents the number of photons having energy above a threshold energy among photons input to the pixel. For example, when the threshold energy input to each pixel of the X-ray detector 120 is three, and the X-ray detector 120 includes m * n pixels (m and n are natural numbers, respectively), as shown in FIG. 8A. data b _1,11 , b _{1 , 12} , b _{1 , mn} , and data b corresponding to threshold energy 2 in each of m * n pixels PX ₁₁ , PX ₁₂ , and PX _mn . Data of data b _{3 , 11} , b _{3 , 12} , to b _{3 , mn} corresponding to _{2 , 11} , b _{2 , 12} , to b _{2 , mn} and threshold energy 3 are output. Both the subscript of PX and the second subscript of b are coordinates indicating the position of the pixel corresponding to the data in the two-dimensional pixel array, and the first subscript of b indicates the corresponding threshold energy.

 Referring to FIG. 8B, the function acquisition unit 131 may include a measurement value storage unit 131a that stores measured values for a phantom designed in advance, and an operation unit that performs an operation for obtaining a calibration function using the stored measured values. 131b.

The phantom may cover all the pixels of the X-ray detector 120, and the thickness and the material are designed to be uniform for all the pixel areas, so that a plurality of phantoms having different thicknesses and the material configurations are designed.

The X-ray data is measured by performing X-ray imaging on the designed phantoms under conditions applied when the actual object is photographed. At this time, the image can be taken with sufficient exposure time so that the influence of quantum noise is minimized. The conditions applied when the actual object is photographed include at least one of the tube voltage and tube current of the X-ray generator 110, the target material of the anode, the exposure time, the type of filter, and the threshold energy input to the X-ray detector 120.

The measured X-ray data is measured by the threshold energy (Th ₁ , Th ₂ , Th ₃ ) and the type of phantom (Phantom ₁ ) in the measured value storage unit 131a. To Phantom _k ). If the type of phantom taken is k (k is a natural number), the X-ray data (b ₁₁ , b ₁₂ to b _mn ) corresponding to each threshold energy (Th ₁ , Th ₂ , Th ₃ ) is divided by type of phantom ( Phantom ₁ To Phantom _k ). The superscript of the data shown in FIG. 8B indicates the type of phantom, the first subscript indicates the threshold energy, and the second subscript indicates the position of the corresponding pixel.

The calculation unit 131b performs an operation for obtaining a calibration function using data stored in the measurement value storage unit 131a. Since the error appearing in the output value of the X-ray detector 120 is due to the characteristics of the light receiving element or the characteristics of the readout circuit, the calibration function is obtained for each pixel.

In addition, as shown in FIG. 4B, when a plurality of comparators and counters are provided in the X-ray detector 120 to separate the detected X-rays into a plurality of energy bands, characteristics may be different for each device. In this case, a calibration function for each threshold energy and pixel is obtained.

As an example, the calculator 131b may assume that the calibration function is a polynomial defined by a plurality of coefficients, and may determine coefficient values of the polynomial by using data stored in the measured value storage unit 131a. In order to obtain a calibration function for one threshold energy, X-ray data corresponding to another threshold energy may be used, and the calibration function may be defined as shown in Equations 1 to 3 below.

[Equation 1]

b ₁ '= C _{1 , 0} + C _{1 , 1} b ₁ + C _{1 , 2} b ₂ + C _{1 , 3} b ₃ + C _{1 , 4} b ₁ b ₂ + C _{1 , 5} b ₁ b ₃ + C _{1 , 6} b ₂ b ₃ + C _{1 , 7} b ₁ ² + C _1,8 b ₂ ² + C _{1 , 9} b ₃ ²

&Quot; (2) "

b ₂ '= C _{2 , 0} + C _{2 , 1} b ₁ + C _{2 , 2} b ₂ + C _{2 , 3} b ₃ + C _{2 , 4} b ₁ b ₂ + C _{2 , 5} b ₁ b ₃ + C _{2 , 6} b ₂ b ₃ + C _{2 , 7} b ₁ ² + C _2,8 b ₂ ² + C _{2 , 9} b ₃ ²

&Quot; (3) "

b ₃ '= C _{3 , 0} + C _{3 , 1} b ₁ + C _{3 , 2} b ₂ + C _{3 , 3} b ₃ + C _{3 , 4} b ₁ b ₂ + C _{3 , 5} b ₁ b ₃ + C _{3 , 6} b ₂ b ₃ + C _{3 , 7} b ₁ ² + C _3,8 b ₂ ² + C _{3 , 9} b ₃ ²

In [Equations 1] to [Equation 3], b ₁ ', b ₂ ', b ₃ 'are the threshold energy 1 (Th ₁ ), threshold energy 2 (Th ₂ ), threshold energy 3 (Th ₃ ), respectively The ideal X-ray data corresponding to the X-ray data, that is, assumes that an error according to characteristics of each pixel is not reflected. In addition, b ₁ , b ₂ , and b ₃ are X-ray data for each threshold energy stored in the measured value storage unit 131a, and C is a coefficient of the polynomial. Therefore, Equations 1, 2, and 3 become functions representing the relationship between the measured X-ray data and the ideal X-ray data.

The calculation for obtaining the calibration function is performed for each threshold energy and pixel. First, an operation of the calculator 131b for obtaining a calibration function corresponding to a pixel having a coordinate of (1, 1) (hereinafter referred to as pixel ₁₁ ) and a threshold energy 1 (Th ₁ ) will be described.

Since the polynomial of Equation 1 includes ten coefficients, ten equations are required to determine ten unknown coefficients. Therefore, the X-ray data measured by radiating X-rays to at least 10 kinds of phantoms is stored in the measurement value storage unit 131a. However, this is only one embodiment of the disclosed invention, and there is no limitation on the number of coefficients, and if necessary, the polynomial may be set to have an appropriate number of coefficients. The number of phantom types also varies according to the number of coefficients.

Referring back to FIG. 8B, the data needed to obtain a calibration function corresponding to pixel ₁₁ and threshold energy 1 (Th ₁ ) is the data set of the first column of the data structure of FIG. 8B. Specifically, the operating section (131b) by substituting the _first b _{^1, 11} b ₁ of the Equation 1, and substituting the _2,11 b ¹ to b _2, and substituting ¹ b _3, b ₃ to ₁₁ Create one equation for Phantom 1. The representative data of the data set of the first row of the data structure of FIG. 8B, that is, the data set corresponding to the threshold energy 1 and the phantom 1 may be substituted into the ideal data b ₁ ′. Here, the representative value is the most frequent mode value among the m * n pixel values, the median value of the m * n pixel values, the weighted sum value obtained by adding an appropriate weight to each pixel value, and the average value of m * n pixel values. At least one selected from the group containing (m and n are each a natural number). The representative value may be stored in the measured value storage unit 131a together with the measured X-ray data.

In the same manner, if one equation is made for each of the remaining nine phantoms and ten equations are completed, the calculator 131b solves the equations and determines values for the ten coefficients. Substituting the determined coefficient value into [Equation 1], a calibration function for threshold energy 1 and pixel ₁₁ is obtained.

9 is a diagram schematically illustrating a structure of data stored in a function storage unit.

The calculation unit 131b may obtain a calibration function for each threshold energy and for each pixel in the same manner as the above-described calibration functions for the threshold energy 1 and the pixel ₁₁ , and the obtained calibration function is stored in the function storage unit 132. Stored.

9, functions f _{1 and 11} for threshold energy 1 (Th ₁ ) and pixel ₁₁ (PX ₁₁ ) to functions f _{3 and mn} for threshold energy 3 (Th ₃ ) and pixel _mn (PX _mn ). The function may be stored in the function storage unit 132 for each threshold energy and pixel. The function stored in the function storage unit 132 may be called and used when correcting an image of an actual object.

FIG. 10 is a diagram schematically illustrating a structure of data stored in a measurement value storage unit when acquiring a calibration function for each condition, and FIG. 11 is stored in a function storage unit when acquiring a calibration function for each condition. A diagram schematically showing the structure of the data is shown.

As mentioned above, the X-ray imaging apparatus 100 may include an AEC to optimize X-ray imaging conditions to an object. In this case, X-ray imaging conditions may vary according to an object, and the X-ray imaging apparatus 100 may obtain a calibration function for each X-ray imaging condition.

Referring to FIG. 10, some sets of X-ray imaging conditions that can be set by the AEC are estimated in advance, X-ray data is measured by radiating X-rays to the phantom for each X-ray imaging condition set, and the X-ray data is stored in the measured value storage unit 131a. do. X-ray imaging conditions such as the tube voltage, the tube current, the target material of the anode, the exposure time, the threshold energy, and the filter type described above may form one set. 10 illustrates a case where X-ray data is measured for three sets of X-ray imaging conditions, and one threshold energy input to one pixel is one. Therefore, the X-ray data measured under the conditions 1, 2 and 3 are stored in the measurement value storage unit 131a for each phantom and for each pixel.

And the calculation unit 131b performs a calculation in the manner described above to obtain a calibration function, but [Equation 1] is for condition 1, not the threshold energy 1, [Equation 2] is the condition 2, Equation 3 is for condition 3.

The obtained calibration function is stored in the function storage unit 132 for each condition (condition 1, condition 2, condition 3) and for each pixel (PX ₁₁ to PX _mn ), as shown in FIG. 11, and corrects an image of an actual object. In the poem, a function corresponding to a condition applied to photographing an object may be called and used.

Referring to FIG. 7 again, the image corrector 133 corrects an X-ray image obtained by photographing an actual object by using a calibration function stored in the function storage 132.

Assuming that the X-ray detector 120 separates the X-rays input to each pixel by three threshold energies and applies the example of FIGS. 8 and 9, the X-ray generator 110 first applies three energy bands to the object. Irradiating a wide-band X-ray, and the X-ray detector 120 detects the X-rays transmitted through the object, the number of photons larger than the threshold energy 1, the number of photons larger than the threshold energy 2 and the number of photons larger than the threshold energy 3, respectively X-ray data corresponding to the threshold energy 1, X-ray data corresponding to the threshold energy 2, and X-ray data corresponding to the threshold energy 3 are output.

The output X-ray data is input to the image corrector 133 and corrected. Since the X-ray data corresponding to the threshold energy 1 forms an X-ray image corresponding to the threshold energy 1, and the same for the threshold energy 2 and the threshold energy 3, the correction of the X-ray data by the image corrector 133 is equivalent to correcting the X-ray image. It can mean the same thing.

The image corrector 133 reads the functions f _{1 , 11} to f _{1 , mn} corresponding to the threshold energy 1 (Th ₁ ) from the function storage 132 to correct the X-ray image corresponding to the threshold energy 1. The X-ray data of each pixel is corrected by using a function corresponding to the pixel.

For example, the X-ray data of the pixel ₁₁ is corrected using f _{1 and 11} . When the function obtaining unit 131 obtains the calibration function by using Equation 1, the functions f _{1 and 11} corresponding to the threshold energy 1 may be represented by Equation 4 below.

&Quot; (4) "

f _{1 , 11} (b ₁ , b ₂ , b ₃ ) = C _{1 , 0} + C _{1 , 1} b ₁ + C _{1 , 2} b ₂ + C _{1 , 3} b ₃ + C _{1 , 4} b ₁ b ₂ + C _{1 , 5} b ₁ b ₃ + C _{1 , 6} b ₂ b ₃ + C _{1 , 7} b ₁ ² + C _{1 , 8} b ₂ ² + C _{1 , 9} b ₃ ²

Here, C _{1 , 0} to C _{1 , 9} are coefficients already determined, and b ₁ , b _2, and b ₃ are variables, and X-ray data (b _{1 , 11} , b) corresponding to each threshold energy output from the pixel ₁₁ are here. _{2 , 11} , b _{3 , 11} ) can be obtained, the X-ray data can be obtained that the error is corrected. When the X-ray data is corrected in the same manner with respect to the remaining pixels, the X-ray image corresponding to the threshold energy 1 is corrected.

The image corrector 133 reads the functions f _{2 , 11} to f _{2 , mn} corresponding to the threshold energy 2 (Th ₂ ) from the function storage 132 to correct the X-ray image corresponding to the threshold energy 2. The X-ray data of each pixel is corrected by using a function corresponding to the pixel.

For example, the X-ray data of the pixel ₁₁ is corrected using f _{2 , 11} . When the function obtaining unit 131 obtains the calibration function using Equation 2, the functions f _{2 and 11} may be represented by Equation 5 below.

&Quot; (5) "

f _{2 , 11} (b ₁ , b ₂ , b ₃ ) = C _{2 , 0} + C _{2 , 1} b ₁ + C _{2 , 2} b ₂ + C _{2 , 3} b ₃ + C _{2 , 4} b ₁ b ₂ + C _{2 , 5} b ₁ b ₃ + C _{2 , 6} b ₂ b ₃ + C _{2 , 7} b ₁ ² + C _{2 , 8} b ₂ ² + C _{2 , 9} b ₃ ²

Here, C _{2 , 0} to C _{2 , 9} are coefficients already determined, and b ₁ , b _2, and b ₃ are variables, and X-ray data (b _{1 , 11} , b) corresponding to each threshold energy output from the pixel ₁₁ are included here. _{2 , 11} , b _{3 , 11} ) can be obtained, the X-ray data can be obtained that the error is corrected. When the X-ray data is corrected in the same manner with respect to the remaining pixels, the X-ray image corresponding to the threshold energy 2 is corrected.

The image corrector 133 reads the functions f _{3 , 11} to f _{3 , mn} corresponding to the threshold energy 3 (Th ₃ ) from the function storage 132 to correct the X-ray image corresponding to the threshold energy 3. The X-ray data of each pixel is corrected by using a function corresponding to the pixel.

For example, the X-ray data of the pixel ₁₁ is corrected using f _{3 and 11} . When the function obtaining unit 131 obtains the calibration function using Equation 1, the functions f _{3 and 11} may be represented by Equation 4 below.

&Quot; (4) "

f _{3 , 11} (b ₁ , b ₂ , b ₃ ) = C _{3 , 0} + C _{3 , 1} b ₁ + C _{13 , 2} b ₂ + C _{3 , 3} b ₃ + C _{3 , 4} b ₁ b ₂ + C _{3 , 5} b ₁ b ₃ + C _{3 , 6} b ₂ b ₃ + C _{3 , 7} b ₁ ² + C _{3 , 8} b ₂ ² + C _{3 , 9} b ₃ ²

Here, C _{3 , 0} to C _{3 , 9} are coefficients already determined and b ₁ , b _2, and b ₃ are variables, and X-ray data (b _{1 , 11} , b corresponding to each threshold energy output from pixel ₁₁₎ are included here. _{2 , 11} , b _{3 , 11} ) can be obtained, the X-ray data can be obtained that the error is corrected. When the X-ray data is corrected in the same manner with respect to the remaining pixels, the X-ray image corresponding to the threshold energy 3 is corrected.

The image processor 134 performs image processing on the corrected X-ray image, wherein the image processing includes at least one of image processing for image enhancement or image enhancement and image processing for multi-energy X-ray image acquisition. The latter image processing includes a case in which the X-rays detected by the X-ray detector 120 are separated for each of a plurality of energy bands.

As a specific example, when the object is a breast and the X-ray detector 120 outputs an X-ray image corresponding to three threshold energies, if the image corrector 133 corrects the X-ray image, the image processor 134 may correct the X-ray image. An X-ray image for each energy band is obtained from the X-ray image, and an X-ray image for each energy band is multiplied by an appropriate weight and subtracted to obtain an image obtained by separating three types of soft tissues having different attenuation characteristics.

As another example, when the object is a chest and the X-ray detector 120 outputs an X-ray image corresponding to two threshold energies, when the image corrector 133 corrects the X-ray image, the image processor 134 corrects the X-ray image. The X-ray image of each energy band can be obtained from the X-ray image, and the X-ray image of each energy band can be multiplied by an appropriate weight and subtracted to obtain an image of bone and soft tissue.

The final X-ray image output from the image processor 134 is displayed on the display unit 141.

12 is a control block diagram of an X-ray imaging apparatus according to another exemplary embodiment of the present disclosure.

Referring to FIG. 12, the X-ray imaging apparatus 200 generates an X-ray, an X-ray generator 210 that irradiates an object, and an X-ray detector that detects X-rays passing through the object and converts the signal into an electrical signal to obtain X-ray data. 220) and a control function for acquiring a calibration function for correcting an error according to pixel characteristics for each phantom set and storing the calibration function for each phantom set and applying the calibration function for each phantom set stored in advance to the X-ray image of the real object to correct the image and the X-ray And a display unit 241 for displaying an image.

Since the description of the X-ray generator 210 and the X-ray detector 220 is the same as in the above-described embodiment, the description thereof will be omitted.

The controller 230 applies a function obtaining unit 231 for obtaining a calibration function for each threshold energy, pixel, and phantom set, a function storage unit 232 for storing the obtained function, and a calibration function to apply the calibration function. And an image processor 234 for correcting an image, and an image processor 234 for performing image processing on the corrected X-ray image.

The operation of acquiring and storing the calibration function in the function acquiring unit 231 and the function storage unit 232 is similar to that of the function acquiring unit 131 and the function storage unit 132 according to the above-described embodiment. The function acquirer 231 according to an example divides the plurality of phantoms into at least two sets to obtain a calibration function for each phantom set, and the function storage unit 232 stores the obtained function.

FIG. 13 is a diagram schematically illustrating a structure of data stored in a function storage unit of an X-ray imaging apparatus according to another exemplary embodiment of the present disclosure.

For example, when the calibration function is obtained using Equations 1 to 3, X-ray data is measured for each of 10 types of phantoms belonging to set A and 10 types of phantoms belonging to set B, respectively. By using the measured X-ray data, a threshold energy and a pixel-specific calibration function are obtained for sets A and B, respectively.

Accordingly, as shown in FIG. 13, the function storage unit 232 may perform the calibration function f ^A (for the set A for each threshold energy Th ₁ , Th ₂ , Th ₃ , and pixels PX ₁₁ to PX _mn ). b) and the calibration function f ^B (b) for set B. Specifically, the functions f ^A _{1 , 11} and f ^B _{1 , 11} corresponding to the threshold energy 1 and the pixel ₁₁ (PX ₁₁ ) are stored, and the same applies to the remaining pixels and the remaining threshold energy.

The image corrector 233 applies the calibration function f ^A (b) for the set A to the first image corrector 233a for correcting the X-ray image of the real object, and the calibration function f ^B (b) for the set B. A second image corrector 233b for correcting the X-ray image of the real object, a corrected image to which a calibration function f ^A (b) is applied, and a corrected image to which a calibration function f ^B (b) is applied to Set B And an image synthesizing unit 233c for synthesizing the same.

Correcting the X-ray image by the first image corrector 233a and the second image corrector 233b is the same as that of the image corrector 133 according to the above-described embodiment. However, the first image corrector 233a applies the calibration function f ^A (b) for the set A to output the corrected image A, and the second image corrector 233b outputs the calibration function f ^B (for the set B). b) is applied to output the corrected image B.

The corrected image A and the corrected image B are input to the image synthesizing unit 233c, and the image synthesizing unit 233c synthesizes the corrected image A and the corrected image B to which different calibration functions are applied to finally generate one corrected image. . When the threshold energy is two or more, the first image corrector 233a and the second image corrector 233b respectively perform functions f ^A (b) and f ^B (b) for each X-ray image corresponding to each threshold energy. The image synthesizer 233c synthesizes the corrected image A and the corrected image B for each threshold energy, and finally generates one corrected image for each threshold energy.

The image synthesizing unit 233c may compare the corrected image A and the corrected image B for each region to select or extract the region with the least noise, or may add the region having the smallest noise with a greater weight. In this case, the area to be compared may be a pixel unit, a unit larger than the pixel, or may be an area divided according to the characteristics of the object. Hereinafter, a case of comparing regions divided according to characteristics of an object will be described as an example.

14 is a cross-sectional view showing the internal tissue configuration of the breast.

As an example, X-ray imaging may be performed using the breast as a subject. Referring to FIG. 14, the tissue of the breast 30 is formed around the circumference of the breast to maintain its shape, the fibrous tissue 31, the adipose tissue 32 distributed throughout the breast, and the mammary gland 33 to produce breast milk. And the associated tissue 34, which is a passage for breast milk. Among these, tissues related to the production and supply of breast milk, such as the mammary gland tissue 33 and the coronary tissue 34, are called parenchymal tissues of the breast. The parenchymal tissue and the adipose tissue 32 have different X-ray attenuation characteristics, so Also appears differently.

Accordingly, the image synthesizer 233c divides the X-ray image of the object into a real tissue region and an adipose tissue region, and compares whether the noise of the real tissue region is smaller in the corrected image A or smaller in the corrected image B. The real tissue region is extracted from the smaller corrected image, and the adipose tissue region is extracted from the corrected image where the noise is smaller by comparing whether the noise of the adipose tissue region is smaller in the corrected image A or smaller in the corrected image B. Two regions can be synthesized.

Alternatively, the weighted data may be added for each region, and a larger weight may be given to a corrected image in which noise is smaller.

The synthesized corrected image is displayed on the display unit 241 through image processing by the image processor 234.

Hereinafter, an embodiment of a control method of an X-ray imaging apparatus according to an aspect of the disclosed invention will be described.

15 is a flowchart illustrating a control method of an X-ray imaging apparatus according to an exemplary embodiment of the present disclosure.

Referring to FIG. 15, first, a calibration function for each pixel and threshold energy is obtained and stored (410). Acquisition and storage of the calibration function is performed before the actual object is photographed, may be performed once before using the X-ray imaging apparatus, may be performed at regular intervals, or may be performed at every component replacement or arbitrarily without a predetermined cycle. One embodiment of the disclosed invention does not limit the timing or number of times to obtain a calibration function.

In operation 420, X-rays are irradiated to the actual object, and X-rays transmitted through the object are detected (430). For example, in order to obtain a multi-energy X-ray image having high contrast between tissues, a wide-band X-ray including a plurality of energy bands may be irradiated onto the object and detected.

In operation 440, the detected X-rays are separated by the threshold energy and the X-ray image for each threshold energy is obtained. Specifically, when there are two threshold energies input to each pixel of the X-ray detector, two X-ray images corresponding to each threshold energy are obtained. When the threshold energies input to each pixel of the X-ray detector are three threshold energies, Three X-ray images corresponding to are obtained.

The X-ray image is corrected by applying a calibration function corresponding to the pixel data of the X-ray image for each threshold energy (450). To do this, the stored calibration function is retrieved in step 410 and the corresponding calibration function is applied for each threshold energy and pixel. Correction of the image to which the calibration function is applied is the same as described above in the embodiment of the X-ray imaging apparatus 100, and thus description thereof will be omitted.

The image processing may be performed on the corrected threshold energy X-ray image (460), and the final image may be output through the display unit. The image processing may include at least one of image processing for image quality enhancement or image enhancement and image processing for multi-energy X-ray image acquisition. In the case of the latter image processing, the X-rays detected by the X-ray detector are separated for each of a plurality of energy bands, and the description thereof is the same as described above in the embodiment of the X-ray imaging apparatus 100, and thus description thereof will be omitted. do.

FIG. 16 is a flowchart illustrating a process of obtaining and storing a calibration function for each energy per pixel.

Referring to FIG. 16, X-rays are first irradiated to a phantom designed in advance (411), and X-rays transmitted through the phantom are detected (412). The phantom can cover all the pixels of the X-ray detector, and the thickness and the material are designed to be uniform for all the pixel areas, so that a plurality of phantoms having different thicknesses and material configurations are designed.

When X-rays are irradiated to the phantom, X-rays are irradiated under conditions applied when the actual object is photographed. At this time, the image can be taken with sufficient exposure time so that the influence of quantum noise is minimized. The conditions applied when the actual object is photographed include at least one of the tube voltage and tube current of the X-ray generator, the target material of the anode, the type of filter, the X-ray exposure time, and the threshold energy input to the X-ray detector.

The detected X-rays are separated for each threshold energy to obtain an X-ray image for each threshold energy (413). The acquired image is stored in the measurement value storage unit.

When the X-ray image is acquired for all the phantoms (Yes of 414), the calibration function for each pixel and the threshold energy is acquired and stored using the stored X-ray image of the phantom (415). Since the X-ray image is composed of X-ray data corresponding to each pixel, a calibration function for each pixel and threshold energy may be obtained using the stored X-ray data. For example, assuming that the calibration function is a polynomial defined by a plurality of coefficients, unknown coefficient values can be determined by substituting the stored X-ray data into polynomials for each phantom and using equation solving. The information regarding the acquisition and storage of the calibration function is the same as in the above-described embodiment.

The acquisition and storage of the calibration function are repeated until 416 is complete for all pixels and all threshold energies. In the above-described embodiment, the calibration function is acquired for each threshold energy. However, when the X-ray imaging apparatus adjusts the X-ray imaging conditions using AEC, the calibration function is acquired for each condition by predicting some conditions applicable to the actual object. It is also possible. The condition may also include threshold energy.

17 is a flowchart illustrating a control method of an X-ray imaging apparatus according to another exemplary embodiment of the present disclosure. In this embodiment, two or more types of calibration functions are acquired according to the phantom set.

Referring to FIG. 17, X-rays are irradiated to a phantom designed in advance (511), and X-rays transmitted through the phantom are detected (512). X-rays are irradiated under conditions that are applied at the time of photographing an actual object, and phantoms can cover all pixels of the X-ray detector and are designed to have a uniform thickness and material for all pixel areas, and thus have different thicknesses and material configurations. Multiple phantoms are designed.

The detected X-rays are separated for each threshold energy, and an X-ray image for each threshold energy is obtained (513) and stored.

When the acquisition of the X-ray image is completed for all the phantom sets (Yes of 514), a calibration function for each phantom set, for each pixel, for each threshold energy is obtained and stored (515). One phantom set is composed of a plurality of phantoms used to obtain one calibration function, and the phantom set may be two or more, and there is no limit to the number of phantom sets, but in this embodiment, two phantom sets (phantom set A, phantom set) It is assumed that B) is used.

The process of acquiring and storing the calibration function is the same as in the above-described embodiment, but the same process is performed in this embodiment for two phantom sets to obtain and store two calibration functions per pixel and per threshold energy. There is a difference.

When the acquisition and storage of the calibration function are completed, X-ray imaging and image correction are performed on the real object.

To this end, X-rays are irradiated to the object (520), and X-rays transmitted through the object are detected (530). For example, in order to obtain a multi-energy X-ray image having high contrast between tissues, a wide-band X-ray including a plurality of energy bands may be irradiated onto the object and detected.

In operation 540, the detected X-rays are separated by the threshold energy and the X-ray image for each threshold energy is obtained.

The calibration function of the phantom set A and the calibration function of the phantom set B are applied to the X-ray images for each threshold energy (550) to generate a corrected image A and a corrected image B for each threshold energy.

The corrected image A and the corrected image B are synthesized (560) to generate one corrected image. In detail, the corrected image A and the corrected image B may be compared for each region to select or extract the region having the smallest noise, and may combine or may add the region having the smallest noise with greater weight. In this case, the area to be compared may be a pixel unit, a unit larger than the pixel, or may be an area divided according to the characteristics of the object.

The X-ray image for each of the finally corrected threshold energy is image-processed and output through the display unit. The content of image processing is the same as in the above-described embodiment.

100,200: X-ray imaging apparatus 110,210: X-ray generator
120,220: X-ray detection unit 130,230: control unit
131,231: function acquisition unit 132,232: function storage unit
131a and 231a: measurement value storage unit 131b and 231b and calculation unit
133, 233: image correction unit

Claims (30)

An x-ray generator for generating and irradiating an x-ray;
An X-ray detector for detecting the irradiated X-rays and counting the number of photons having energy above a threshold energy among the photons included in the detected X-rays for each pixel to output X-ray data;
A function obtaining unit obtaining a calibration function for each pixel by using X-ray data output for a plurality of previously designed phantoms; And
And an image corrector configured to correct the X-ray image of the object for each pixel by using the obtained calibration function. The method of claim 1,
The function acquisition unit,
A measurement value storage unit configured to store X-ray data output by the X-ray generation unit radiating X-rays to the phantom and the X-ray detection unit detects X-rays passing through the phantom; And
And an operation unit configured to perform an operation for obtaining the calibration function using the X-ray data stored in the measurement value storage unit. 3. The method of claim 2,
The operation unit,
And a function defined by at least one coefficient as the calibration function, and determines the value of the coefficient by substituting X-ray data stored in the measured value storage unit as a variable of the function. The method of claim 3, wherein
The operation unit,
And determining the value of the coefficient by assuming ideal X-ray data without an error as a function value of the function. 5. The method of claim 4,
The operation unit,
And determining the value of the coefficient by substituting a representative value of the X-ray data for the phantom as a function value of the function. The method of claim 5, wherein
The representative value of the X-ray data for the phantom,
X-ray at least one selected from the group including the most frequent mode value among all pixel values, the median value among all pixel values, a weighted sum value obtained by appropriately weighting each pixel value, and an average value averaged over all pixel values Imaging device. The method of claim 1,
And at least two threshold energies are input to a single pixel of the X-ray detector, the function obtaining unit obtaining the calibration function for each threshold energy. The method of claim 7, wherein
Wherein the image correction unit comprises:
When two or more threshold energies are input to a single pixel of the X-ray detector, the X-ray imaging apparatus corrects the X-ray image of the object for each pixel and for each threshold energy by using the calibration function. The method of claim 1,
The function acquisition unit,
An X-ray imaging apparatus for acquiring the calibration function for each X-ray imaging condition of an object. The method of claim 9,
Wherein the image correction unit comprises:
An X-ray imaging apparatus for calibrating an X-ray image of the object by using a calibration function corresponding to an X-ray imaging condition applied to the object. The method of claim 1,
The function acquisition unit,
And dividing the plurality of phantoms into at least two phantom sets, and obtaining the calibration function for each phantom set. The method of claim 11,
Wherein the image correction unit comprises:
And at least two corrected X-ray images by applying a calibration function acquired for each phantom set to the X-ray image of the object. 13. The method of claim 12,
Wherein the image correction unit comprises:
And a corrected X-ray image by synthesizing the two corrected X-ray images. The method of claim 13,
Wherein the image correction unit comprises:
And comparing the two corrected X-ray images for each region to select and synthesize an area having the least noise, or to add the weighted area to the area having the least noise. 15. The method of claim 14,
The area corresponds to one of a region in pixels and a region divided according to characteristics of an object. Obtaining a calibration function for each pixel using X-ray data of a plurality of pre-designed phantoms;
Irradiating X-rays on the object and detecting X-rays passing through the object to obtain an X-ray image of the object; And
And calibrating the X-ray image of the object for each pixel by using the obtained calibration function. 17. The method of claim 16,
Acquiring the calibration function,
Storing X-ray data for the phantom; And
And performing a calculation to obtain the calibration function using the stored X-ray data. The method of claim 17,
Performing an operation for obtaining the calibration function,
And assuming that a function defined by at least one coefficient is the calibration function, and substituting the stored X-ray data as a variable of the function to determine a value of the coefficient. The method of claim 18,
Performing an operation for obtaining the calibration function,
And determining the value of the coefficient by assuming ideal X-ray data having no error reflected as a function value of the function. The method of claim 19,
Performing an operation for obtaining the calibration function,
The control method of the X-ray imaging apparatus determines the value of the coefficient by substituting the representative value of the X-ray data for the phantom as a function value of the function. 21. The method of claim 20,
The representative value of the X-ray data for the phantom,
X-ray at least one selected from the group including the most frequent mode value among all pixel values, the median value among all pixel values, a weighted sum value obtained by appropriately weighting each pixel value, and an average value averaged over all pixel values Control method of the imaging device. 17. The method of claim 16,
If the X-ray image of the object is obtained for each of at least two threshold energies, the obtaining of the calibration function comprises obtaining the calibration function for each of the threshold energies. 23. The method of claim 22,
Compensating the X-ray image of the object for each pixel,
If the X-ray image of the object is obtained for at least two threshold energy, the control method of the X-ray imaging apparatus to correct the X-ray image of the object for each pixel, the threshold energy by using the calibration function. 17. The method of claim 16,
Acquiring the calibration function,
And obtaining the calibration function for each X-ray imaging condition of an object. 25. The method of claim 24,
Compensating the X-ray image of the object for each pixel,
And correcting an X-ray image of the object by using a calibration function corresponding to an X-ray imaging condition applied to the object among the obtained calibration functions. 17. The method of claim 16,
Acquiring the calibration function,
Dividing the plurality of phantoms into at least two phantom sets, and obtaining the calibration function for each of the phantom sets. The method of claim 26,
Compensating the X-ray image of the object for each pixel,
And generating at least two corrected X-ray images by applying a calibration function acquired for each phantom set to the X-ray image of the object. The method of claim 27,
Compensating the X-ray image of the object for each pixel,
And synthesizing the two corrected X-ray images to generate one corrected X-ray image. 29. The method of claim 28,
Synthesizing the two corrected X-ray images,
And comparing the two corrected X-ray images for each region, selecting and synthesizing the region having the least noise, or summing the regions having the least noise with greater weight. 30. The method of claim 29,
And the area corresponds to one of a pixel area and an area divided according to characteristics of an object.

Images