Patent Description:
An X-ray imaging device generates images of an inner structure of an object by radiating X-rays to the object and analyzing X-rays passing through the object. X-ray transmittance varies depending on internal substances of the object, and an image of the inner structure of the object is acquired using an attenuation coefficient indicating transmittance as a numeric value.

In recent years, in order to increase a contrast between internal tissues of the object, a great deal of research has been conducted, and a method for acquiring X-ray images from a plurality of X-rays having different energy levels has been proposed.

<CIT> describes a system which can generate dual energy and single energy images by collecting dual energy x-ray data when scanning the patient and extracting single energy image data from the dual energy data. The dual energy scan data can be used to extract or construct dual energy and single energy images for display. These images can be selectively displayed on the monitor of a workstation, or they can be simultaneously displayed on, for example, a split screen display. <CIT> discloses systems and methods for displaying multi-energy data received from an operably connected data source, wherein the data is displayed as an image, a region of interested is selected in said image and information regarding the selected region of interest are displayed on a graphical user interface.

Exemplary embodiments may address at least the above problems and/or disadvantages and other disadvantages not described above. Also, the exemplary embodiments are not required to overcome the disadvantages described above, and an exemplary embodiment may not overcome any of the problems described above.

The above and/or other aspects will become more apparent by describing certain exemplary embodiments, with reference to the accompanying drawings, in which:.

Certain exemplary embodiments are described in greater detail below with reference to the accompanying drawings.

In the following description, the same drawing reference numerals are used for the same elements even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of exemplary embodiments. Thus, it is apparent that exemplary embodiments can be carried out without those specifically defined matters. Also, well-known functions or constructions are not described in detail since they would obscure exemplary embodiments with unnecessary detail.

<FIG> is a block diagram illustrating a configuration of an X-ray imaging device.

Referring to <FIG>, the X-ray imaging device or the X-ray imaging apparatus <NUM> includes an X-ray generator <NUM> to generate X-rays and radiate the same to an object, an X-ray detector <NUM> to detect X-rays passing through the object, a controller <NUM> to evaluate characteristics of the object using the detected X-rays and produce a single energy X-ray image or a multiple energy X-ray image, based on the evaluated results, and a display <NUM> to display the produced X-ray image.

The X-ray generator <NUM> generates X-rays having a predetermined energy level and radiates the same to the object. The X-ray generator <NUM> receives power from a power supply (not shown) and generates X-rays. The X-ray energy may be controlled by a supplied tube voltage and the X-ray intensity or dose may be controlled by a tube current and an X-ray exposure time.

Although X-rays radiated from the X-ray generator <NUM> may be monochromatic X-rays or polychromatic X-rays, a configuration in which polychromatic X-rays are radiated from the X-ray generator is described below with reference to exemplary examples, for convenience of description.

The X-ray generator <NUM> radiates X-rays having a predetermined energy band, and an energy band of the radiated X-rays is defined by an upper limit and a lower limit. X-ray energy may be represented as average energy, maximum energy, energy band or the like. In an exemplary example, X-ray energy is represented by an X-ray energy band or maximum energy of the X-ray energy band.

The upper limit of the energy band, that is, the maximum energy of radiated X-ray is controlled by a level of tube voltage, and energy band lower limit, that is, a minimum energy of radiated X-rays is controlled by a filter provided inside or outside the X-ray generator <NUM>. When X-rays with a low energy band are filtered through the filter, radiated average X-ray energy is increased.

The X-ray detector <NUM> detects X-rays passing through the object and converts the detected X-rays into electrical signals. X-rays radiated from the X-ray generator <NUM> pass through the object and are attenuated. An attenuation ratio of X-rays varies depending on characteristics of tissues of an object area, to which the X-rays are radiated, or thickness of the object area, and an amount of detected X-rays varies depending on the inner composition of the object. The object is imaged by using the electrical signal of the X-ray detector <NUM> and a signal output from the X-ray detector <NUM> is a type of image signal.

The X-ray detector <NUM> acquires a plurality of image signals with different energy bands. According to an exemplary example, a method of acquiring image signals includes a method including radiating respectively a plurality of X-rays having different energy bands by the X-ray generator <NUM> and detecting respectively the plurality of X-rays by the X-ray detector <NUM>, and a method including radiating X-rays having a predetermined energy band by the X-ray generator <NUM> and dividing the X-rays into specific energy bands by the X-ray detector <NUM>. The different energy bands may have at least one of upper and lower limits of energy bands which are different from one another.

The controller <NUM> analyzes the image signal acquired by the X-ray detector <NUM> and evaluates characteristics of the object. The characteristics of the object include at least one of structures of the tissues constituting the object, ratios of respective tissues and densities of specific tissues, and another characteristic of the object evaluated by the controller <NUM> may be used as a characteristic of the object so long as it determines an X-ray image which is easy to analyze.

The controller <NUM> generates at least one of a single energy X-ray image and a multiple energy X-ray image, based on the evaluation results of the object. The single energy X-ray image means an X-ray image which is produced by detecting X-rays having a single energy band, and the multiple energy X-ray image means an X-ray image which is produced by detecting a plurality of X-rays having different energy bands and increasing a contrast between components of the object using the X-rays detected.

An image signal produced from X-rays having a single energy band exhibits good signal-to-noise ratio (SNR) and a single energy X-ray image thus exhibits superior spatial resolution and contrast. The multiple energy X-ray image has a high contrast between tissues and is thus useful for specific tissues such as lesions.

Accordingly, when an image with a high contrast between tissues is needed depending on characteristics of the object, a multiple energy X-ray image is produced, and when an image with low contrast between tissues is not needed, a single energy X-ray image with good signal-to-noise ratio is produced.

In an exemplary example, the controller <NUM> produces a multiple energy X-ray image with increased contrast between tissues, when the object has a dense tissue having a high ratio of fat tissue to parenchymal tissue, and the controller <NUM> produces a single energy X-ray image, when the object has a tissue having a high ratio of parenchymal tissue to fat tissue.

The controller <NUM> analyzes an image signal acquired by pre-shot and controls imaging conditions such as tube voltage and tube current supplied to the X-ray generator <NUM> and X-ray exposure time. The pre-shot aims at controlling X-ray imaging conditions depending on characteristics of the object prior to main imaging and is performed at X-rays dose decreased by controlling tube current and X-ray exposure time. Also, the controller <NUM> may select a target material (anode) used for X-ray generation in the X-ray generator <NUM>, or a filter used for filtering the generated X-ray.

The display <NUM> displays the X-ray image generated by the controller <NUM> for a user to perform diagnosis by analyzing the image.

In a case in which the object is human body, the X-ray imaging device may be used to image the chest, mouth, breasts and various other tissues, organs, or bones of the human body according to an application and the structure of the X-ray imaging device may be slightly changed according to imaging area.

Although the X-ray imaging device has no restrictions as to imaging area, for convenience of description, a detailed operation of the mammography X-ray imaging device is described below with reference to an exemplary example.

<FIG> illustrates an overall exterior appearance of an X-ray imaging device to image breast according to an exemplary example. <FIG> is a sectional view illustrating an internal composition of a breast.

Referring to <FIG>, the X-ray imaging device <NUM> to image breasts includes a housing <NUM> to support the X-ray generator <NUM> and the X-ray detector <NUM>, and a compression paddle <NUM> to compress the breast. A breast is disposed between the X-ray detector <NUM> and the compression paddle <NUM>, to reduce a thickness of the breast by compression using the compression paddle <NUM>, and X-rays are irradiated using the X-ray generator <NUM>, to perform X-ray imaging.

The controller <NUM> controls X-ray imaging conditions depending on breast characteristics and for this purpose, the X-ray imaging device performs pre-shot to evaluate characteristics of the breast.

The controller <NUM> analyzes an image signal acquired by pre-shot, estimates or calculates a density of breast and a thickness of compressed breast and determines imaging conditions suitable for characteristics of the object using these properties as analysis factors. Information associated with the thickness of the compressed breast may be acquired from the compression paddle <NUM>.

The controller <NUM> may be provided in a workstation or a host device to control an operation of the X-ray imaging device, but a position thereof is not limited.

Referring to <FIG>, the tissues of the breast <NUM> include fibrous tissue <NUM> which surrounds the breast periphery and supports the breast shape, fat tissue <NUM> distributed throughout the breast, a breast gland tissue <NUM> to produce human milk, and a breast duct tissue <NUM> to provide a passage for breast milk and the like. Tissues associated with production and supply of breast milk, such as the breast gland tissue <NUM> and the breast duct tissue <NUM>, are referred to as parenchymal tissues of breast. The parenchymal tissues have similar lesions, such as tumors, and similar X-ray absorbance. Accordingly, it is difficult to detect lesions from a breast X-ray image in which parenchymal tissues are dense and/or large, and it is relatively easy to detect lesions in a breast X-ray image in which little parenchymal tissue is present.

Accordingly, when the breast <NUM> is a dense breast in which parenchymal tissues are dense, a multiple energy X-ray image with an increased contrast between tissues is produced. When the breast <NUM> has less density, a single energy X-ray image with a superior signal-to-noise ratio is produced.

As described above, the method for producing a multiple energy X-ray image is divided into irradiation of a plurality of X-rays with different energy bands from the X-ray generator <NUM> and separation of X-rays detected from the X-ray detector <NUM> according to respective energy bands.

<FIG> is a block diagram illustrating X-rays imaging device according to an exemplary example in detail.

The X-ray imaging device <NUM> according to the present exemplary example radiates X-rays with different energy bands to produce a multiple energy X-ray image and performs pre-shot prior to main imaging.

Basic operations of the X-ray generator <NUM>, the X-ray detector <NUM> and the display <NUM> have been described above with reference to <FIG>.

The controller <NUM> includes an image analyzer <NUM> to analyze the image signal acquired by the X-ray detector <NUM> and evaluate characteristics of the object, an image controller <NUM> to determine X-ray imaging conditions depending on characteristics of the object, and an image processor <NUM> to produce a single energy X-ray image or a multiple energy X-ray image using the image signal acquired by the X-ray detector <NUM>.

First, the X-ray generator <NUM> radiates X-rays having a lower dose, as compared to the main imaging, to perform pre-shot. The X-ray detector <NUM> detects X-rays passing through the object during pre-shot and acquires an image signal of the object. In an exemplary example, pre-shot may be performed by adjusting X-ray dose to about <NUM> mAs.

The image analyzer <NUM> analyzes the image signal acquired by the X-ray detector <NUM> and evaluates characteristics of the object.

For example, the image analyzer <NUM> determines the breast density. As described above with reference to <FIG>, when parenchymal tissues of breast are dense and/or large, it is not easy to detect lesions in the breast tissue. A growth or a size degree of parenchymal tissues in the breast is referred to as breast density.

In an exemplary example in which the image analyzer <NUM> determines breast density, a breast region is extracted from the image signal acquired by the X-ray detector <NUM> and a region to be estimated as a parenchymal tissue is extracted from the breast region. A ratio of an area of the parenchymal tissue region with respect to a total area of the breast region is calculated to represent the breast density.

Specifically, the region corresponding to the parenchymal tissue is estimated as a region which has a high image signal brightness or intensity. For example, a predetermined first value is compared with the brightness or intensity of the image signal in each pixel region of the breast. When the brightness or intensity of the image signal exceeds the first value, the corresponding pixel region is estimated to belong to the parenchymal tissue. The first value may be predetermined through experimentation, statistics or theoretically.

The image controller <NUM> controls main imaging based on characteristics of the object evaluated by the image analyzer <NUM>. Specifically, the image controller <NUM> determines whether a single energy X-ray image or a multiple energy X-ray image is to be acquired by main imaging, based on characteristics of the object and controls the X-ray generator <NUM> based on the results. That is, when the characteristic of object corresponds to a single energy X-ray image, the single energy X-ray image is acquired, and when the characteristic of object corresponds to a multiple energy X-ray image, the multiple energy X-ray image is acquired.

When the breast density calculated by the image analyzer <NUM> exceeds a predetermined second value, the characteristic of object is determined to correspond to the multiple energy X-ray image, and when the breast density calculated by the image analyzer <NUM> does not exceed the predetermined second value, the characteristic of object is determined to correspond to the single energy X-ray image. The second standard value means a standard value which determines that the breast as the object is a dense breast.

The second value may be predetermined by a designer or a user. For example, when a breast density exceeds <NUM>%, the breast is determined to be a dense breast in accordance with the classification standard of breast imaging reporting and database system (BI-RADS). However, an exemplary example of the X-ray imaging device <NUM> is not limited thereto and other standard values may be set through experimentation or theoretically.

The image controller <NUM> may control imaging conditions such as tube voltage and tube current supplied to the X-ray generator <NUM> and X-ray exposure time depending on object characteristics.

When the characteristic of object corresponds to a multiple energy X-ray image, the X-ray generator <NUM> respectively radiates a plurality of X-rays having different energy bands for main imaging. The energy bands of radiated X-rays may be set according to type or characteristics of object.

<FIG> is a graph showing energy bands of X-rays radiated from the X-ray imaging device.

Referring to <FIG>, the X-ray generator radiates X-rays with a first energy band E1, X-rays with a second energy band E2 and X-rays with a third energy band E3 and the energy bands may partially overlap one another.

In an exemplary example in which X-rays with different energy bands are radiated, in order to radiate the X-ray with a first energy band E1, a tube voltage of about <NUM> kVp is supplied to the X-ray generator <NUM> to generate X-rays with a maximum energy E1max of about <NUM> keV. The X-ray generator <NUM> adjusts a minimum energy E1min of the radiated X-rays to about <NUM> keV using the filter provided inside or outside the device. As a result, X-rays having the first energy band E1 (about <NUM> to about <NUM> keV) are emitted.

Similarly, in order to radiate X-rays with a second energy band E2, a tube voltage of about <NUM> kVp is supplied to the X-ray generator <NUM> to generate X-rays having a maximum energy E2max of about <NUM> keV. The X-ray generator <NUM> adjusts a minimum energy E2min of emitted X-rays to about <NUM> keV using the filter. As a result, X-rays having the second energy band E2 (about <NUM> to about <NUM> keV) are emitted.

Similarly, in order to radiate X-rays with a third energy band E3, a tube voltage of <NUM> kVp is supplied to the X-ray generator <NUM> to generate X-rays having a maximum energy E3max of about <NUM> keV. The X-ray generator <NUM> adjusts a minimum energy E3min of emitted X-rays to about <NUM> keV using the filter. As a result, X-rays having the third energy band E3 (about <NUM> to about <NUM> keV) are emitted.

Referring to <FIG> again, the X-ray detector <NUM> detects a plurality of X-rays passing through the object, acquires a plurality of image signals of respective energy bands from the detected X-rays and transmits the image signals to a first image processor 233a. The first image processor 233a performs multiple energy image processing on the transmitted image signals to produce a multiple energy X-ray image with an increased contrast between tissues.

The multiple energy image processing is an image processing method for producing an image having an increased contrast between soft tissues and lesions having similar X-ray absorbance from a plurality of image signals having different energy bands, or an image having an increased contrast of soft tissues and hard tissues (such as bones or calcified materials) and any multiple energy image processing may be used in the X-ray imaging device.

Hereinafter, a multiple energy image processing method will be described in more detail.

<FIG> is a graph schematically showing variation in attenuation coefficient with respect to individual substances constituting the human body.

As described above, X-ray transmittance is changed depending on characteristics of an object, through which the X-ray passes, and this is defined as an attenuation coefficient.

<FIG> shows variation in attenuation coefficient as a function of X-ray energy with respect to bone, muscle and fat of the human body. As shown in <FIG>, bone, muscle and fat exhibit different variations in attenuation coefficient and the difference in attenuation coefficient between substances is changed according to X-ray energy.

Although variations in attenuation coefficient of bone, muscle, and fat are illustrated in <FIG>, the attenuation coefficient varies between various soft tissues containing fat. Accordingly, by using a plurality of image signals with different energy bands, substances having different attenuation properties may be extracted from one image.

Assuming that an attenuation coefficient of X-rays of N<NUM> photons having an energy E is µ(E), the number N of photons after passing through an object having a thickness T is represented by the following Equation <NUM>.

Assuming that a thickness of the mth substance is Tm and the number of types of substances, through which X-rays pass, is M, the Equation <NUM> may be represented by the following Equation <NUM>.

Based on Equation <NUM>, an image pixel value is determined by dividing both sides by a measurable value N<NUM> and applying antilogarithm (-log ). In the same manner, when a number L of X-ray images are acquired from the number L of different energies E<NUM>, E<NUM>,. , EL, the pixel value I(E<NUM>) may be represented by the following Equation <NUM>.

Accordingly, L equations associated with respective pixels according to the Equation <NUM> are acquired from the number L of X-ray images and this is represented by a matrix formula in the following Equation <NUM>.

Accordingly, if L=M, images of respective substances are acquired by calculating a matrix operation of T = µ-<NUM>. Equation <NUM> is derived based on an ideal monochromatic X-ray image, but a modification of Equation <NUM> may be used when X-rays having a predetermined energy band image are used.

The multiple energy X-ray image produced by the first image processor 233a may be a plurality of images separated according to respective substances, an image of only a specific substance, a region in which a ratio difference between substances is out of a normal range is diacritically marked as an abnormal tissue using the images separated according to respective substances, or an image in which the plurality of images are combined and the respective substances are diacritically marked in one image.

As a multiple energy image processing method according to another example, there is a method for acquiring image signals with non-imaged other energy bands from image signals with different energy bands.

As shown in <FIG>, generally, a difference in attenuation coefficient between the substances decreases, as X-ray energy increases, and increases, as X-ray energy decreases. Accordingly, X-rays with a low energy band in which a difference in attenuation coefficient between the substances is great may be used to obtain a breast X-ray image consisting of soft tissues such as parenchymal tissue, fat tissue and fibrous tissue.

However, since use of X-ray with a low energy band is restricted due to limitations as to physical properties or X-ray dose, an X-ray image with increased contrast between substances is produced by obtaining image signals regarding energy bands which may be imaged without great limitation of X-ray dose and estimating an image signal regarding a low energy band showing a great difference in attenuation coefficient between the substances from these image signals.

The above-described exemplary examples are examples of generating a multiple energy X-ray image, but this is not limiting.

The produced image is displayed on the display <NUM> and a user easily detects lesions on an image with an increased contrast ratio.

Referring to <FIG> again, the image controller <NUM> controls the X-ray generator <NUM> to radiate X-rays having a single energy band to an object, when the characteristic of object corresponds to a single energy X-ray image, that is, the breast is determined not to be a dense breast.

The X-ray detector <NUM> detects X-rays passing through the object and acquires an image signal of the object. The acquired image signal is transmitted to the second image processor 233b which subjects the image signal to image processing to produce an X-ray image. The image processing may include noise removal, edge enhancement or contrast ratio adjustment to produce a single energy X-ray image.

Specifically, the second image processor 233b controls gradation and frequency properties of images by gradation processing and frequency processing, improves image quality through spatial frequency processing and realizes objective image enhancement by gradation processing. Details of such image processing are known to those skilled in the art and a detailed explanation thereof will be omitted.

The produced X-ray image is displayed on the display <NUM> and a user analyzes the X-ray image with a superior signal-to-noise ratio (SNR) and thereby detects lesions.

In the above-described exemplary example, the image signal acquired during pre-shot is analyzed and characteristics of the object are evaluated. However, in an exemplary example an image of main imaging may be analyzed and characteristics of the object may be evaluated instead of or in addition to the pre-shot.

Specifically, the X-ray generator <NUM> radiates X-rays with a first energy band to an object and the X-ray detector <NUM> detects X-rays passing through the object to acquire an image signal. The first energy band corresponds to an energy band to produce a single energy X-ray image and is set by pre-shot or according to object type (chest, abdomen, breast and other skeletons) without pre-shot. For example, when chest is used as the imaging region, a high energy band having a maximum energy of about <NUM> keV is set at a first energy band and, when a breast is used as the imaging region, a low energy band having a maximum energy of about <NUM> keV is set at the first energy band.

The acquired image signal is transmitted to the image analyzer <NUM> and the image analyzer <NUM> analyzes the image signal and evaluates characteristics of the object. A method for evaluating characteristics of the object is described above.

When the characteristic of object evaluated by the image analyzer <NUM> corresponds to a multiple energy X-ray, the image controller <NUM> controls the X-ray generator <NUM> to radiate X-rays with a second energy band to an nth energy (n≥<NUM>, n is an integer) band, the X-ray detector <NUM> detects the X-rays and converts the x-rays into image signals. Here, n may be set depending on characteristics of the object and an order of n is not related to an energy level.

For example, when imaging the chest, n is set at <NUM> and X-rays with an energy band having a maximum energy of about <NUM> keV are radiated, and when imaging the breast, n is set at <NUM> and X-rays with an energy band having a maximum energy of about <NUM> keV are radiated. High energy and low energy are relative concepts. That is, when chest is imaged, X-rays with an energy band having a maximum energy of about <NUM> keV are X-rays with a low energy band, and when breast is imaged, an X-ray with an energy band having a maximum energy of about <NUM> keV is an X-ray with a high energy band.

The converted image signal is transmitted to the first image processor 233a which performs multiple energy image processing on an image signal corresponding to the first energy band and an image signal corresponding to the remaining energy band, produces a multiple energy X-ray image with increased contrast between tissues and displays the image on the display <NUM>.

When the characteristic of object evaluated by the image analyzer <NUM> corresponds to a single energy X-ray image, a first energy X-ray signal is transmitted to the second image processor 233b, and, thus, a single energy X-ray image is generated without further radiation of X-rays.

An exemplary example using a method for acquiring a multiple energy X-ray image by respectively radiating a plurality of X-rays from the X-ray generator is described above. Hereinafter, an exemplary example using a method for separating X-rays according to respective energy bands in the X-ray detector is described below.

<FIG> is a block diagram illustrating a configuration of an X-ray imaging device according to an exemplary example.

Referring to <FIG>, the X-ray imaging device <NUM> includes an X-ray generator <NUM> to generate X-rays, an X-ray detector <NUM> to detect the X-ray passing through the object, a controller <NUM> to evaluate characteristics of the object using the detected X-rays and produce a single energy X-ray image or a multiple energy X-ray image, based on the evaluated results, and a display <NUM> to display the X-ray image.

The X-ray generator <NUM> may perform pre-shot by radiating a reduced dose of X-rays. The X-rays radiated from the X-ray generator <NUM> may be a wide band X-ray including a wide energy band which is an energy band including a plurality of different single energy bands. The energy band of the radiated X-ray may be changed depending on object type. For example, when imaging the chest X-rays having an energy band of about <NUM> to about <NUM> keV may be radiated, and when imaging the breast, X-rays having an energy band of about <NUM> to about <NUM> keV may be radiated.

The radiated X-rays pass through the object and are detected by the X-ray detector <NUM>.

The X-ray detector <NUM> includes a photon counting detector (PCD) <NUM> and separates the detected X-rays according to energy band. In <FIG>, a circuit view of the pixel area of the PCD is shown.

Referring to <FIG>, the PCD <NUM> is divided into a sensor region <NUM> to detect X-rays and a readout circuit region <NUM>, and the sensor region may include a light-receiving device such as photodiode. The two regions may be connected to each other by bonding such as bump bonding. When the X-rays passing through the object reach the sensor region <NUM> of the PCD, electrons which stay in a valance band receive a photon energy of the X-ray and are then excited to a conduction band across a band gap indicating an energy difference. A great amount of electron-hole pairs are produced in a depletion region due to excitation, and electrons and holes are moved in opposite directions based on an electric field applied to the sensor region <NUM>.

The electrons or holes moved based on the electric field are input to the readout circuit region <NUM> through bump bonding, and an amplifier 52a of the readout circuit region <NUM> charges an input charge generated from one photon and outputs a voltage signal corresponding thereto. When the output voltage signal is input to the comparator 52b and a voltage corresponding to an energy band to be separated is input as a threshold voltage, the comparator 52b compares the input voltage signal with the threshold voltage, outputs the comparison results as pulses and input the same to the counter 52c. The counter 52c counts the number of output pulses of the comparator per unit time and measures X-ray intensity (represented as the number of photons) with a predetermined energy band among incident X-rays.

When X-rays passing through the object are detected according to respective bands separated into a first energy band, second energy band and third energy band, the readout circuit region <NUM> may include three comparators corresponding to the energy bands.

A signal output from the X-ray detector <NUM> is an X-ray image signal of each energy band. In the present exemplary example, the X-ray image signal includes information associated with the number of photons present in each pixel. The signals output from the X-ray detector <NUM> are a first energy image signal, a second energy image signal and a third energy image signal. The image signals may be output from the entire energy band which is not separated.

Since evaluation of object characteristics are carried out during pre-shot and an image output from the display <NUM> is acquired during main imaging, the X-ray detector <NUM> may output an image signal in the entire energy band, instead of separating X-rays according to energy bands.

Referring to <FIG> again, the controller <NUM> includes an image analyzer <NUM> to analyze an image signal and evaluate characteristics of the object, an image controller <NUM> to control an X-ray generator <NUM> or X-ray detector <NUM>, based on the analysis results of the image analyzer <NUM>, and an image processor <NUM> to produce a multiple energy X-ray image or a single energy X-ray image.

The image analyzer <NUM> analyzes at least one of image signals output from the X-ray detector <NUM> and evaluates object characteristics. The image signal used for analysis may be the first energy image signal, the second energy image signal, the third energy image signal or any image signal of the entire energy band.

The image analyzer <NUM> evaluates tissue properties of the object and, in an exemplary example, the image analyzer <NUM> determines breast density. Operation of the image analyzer <NUM> is described in detail above and a detailed description thereof is thus omitted.

The image controller <NUM> determines whether the characteristic of object corresponds to a multiple energy X-ray image or a single energy X-ray image, based on the determination results of the image analyzer <NUM>, controls the X-ray generator <NUM> or the X-ray detector <NUM> based on the result and begins main imaging.

When the characteristic of object corresponds to a multiple energy X-ray image, a broadband X-ray having a greater dose than X-rays radiated from the X-ray generator <NUM> during pre-shot is radiated to the object and the X-ray detector <NUM> detects X-rays passing through the object. The energy band of radiated X-rays may be the same as the energy band of X-ray radiated during pre-shot and may be newly set, based on characteristics of the object.

The X-ray detector <NUM> detects the X-ray, converts the same into a voltage signal and separates the converted voltage signal according to predetermined energy bands. The separated energy band may be set by the image controller <NUM> or the user according to object type, or by the image controller <NUM> depending on object characteristics analyzed in the image analyzer <NUM>. Image signals of the image are acquired according to individual energy bands and the acquired image signals are transmitted to the first image processor 333a.

The first image processor 333a performs multiple energy image processing on the image signals according to individual energy bands, produces a multiple energy X-ray image with an improved contrast between tissues and displays the image on the display <NUM>. The image processing operation of the first image processor 333a is described in detail above.

In the present exemplary example, characteristics of the object are evaluated by analyzing image signals acquired by pre-shot, but in another exemplary example, characteristics of the object may be evaluated by analyzing image signals acquired by main imaging.

<FIG> is a block diagram illustrating an X-ray imaging device according to an exemplary embodiment.

In a case of using a method of dividing X-rays according to individual energy bands to obtain a plurality of X-ray images, X-ray dose may be decreased even during main imaging, an energy band suitable for characteristics of an object may be set once after X-rays are radiated and pre-shot may be thus not performed. The X-ray imaging device <NUM> according to the exemplary embodiment of <FIG> analyzes image signals acquired during main imaging, regardless of performance of pre-shot.

The X-ray generator <NUM> radiates a broadband X-ray including a plurality of energy bands to an object. X-rays passing through the object are converted into an electric signal by the X-ray detector <NUM> and the X-ray detector <NUM> including the PCD separates the converted electric signals into individual energy bands predetermined according to object type, or separates only an energy band used for determination of object characteristics or acquires an image signal of the entire energy band.

The image analyzer <NUM> of the controller <NUM> analyzes image signals of the object and evaluates characteristics of the object. The image signal used for evaluation of characteristics of the object is one of image signals converted by the X-ray detector <NUM>. When the X-ray detector <NUM> separates the X-ray into predetermined individual energy bands, one of the separated energy bands may be selected and analyzed. For example, when imaging the breast, an image signal corresponding to a low energy band may be analyzed, and when imaging the chest, an image signal corresponding to a high energy band may be analyzed. The evaluation of characteristics of the object is described in detail above.

The image controller <NUM> determines whether the characteristic of object determined in the image analyzer <NUM> corresponds to a multiple energy X-ray image or a single energy X-ray image.

Generation of a multiple energy X-ray image or a single energy X-ray image according to an exemplary embodiment will be described in detail below.

When the X-ray detector <NUM> acquires a plurality of image signals according to a plurality of individual energy bands, the image signals are stored in a memory (not shown) provided in the X-ray detector <NUM> or the controller <NUM>.

When the imaging controller <NUM> determines that the characteristic of the object corresponds to a multiple energy X-ray image, the memory transmits the image signals to a first image processor 433a, and the first image processor 433a produces a multiple energy X-ray image with improved contrast between tissues through multiple energy image processing.

When the imaging controller <NUM> determines that the characteristic of object corresponds to a single energy X-ray image, the memory transmits one of the image signals to the second image processor 433b. The image signal transmitted to the second image processor 433b may be determined depending on type or characteristics of the object and may be an image signal used for the image analyzer <NUM>.

In a case in which the X-ray detector <NUM> separates only an energy band used for evaluation of characteristics of the object, when the characteristic of object corresponds to a multiple energy X-ray image, X-rays are separated at a not-separated band among the energy bands, image signals at respective energy bands and image signals used for evaluation of characteristics of the object are transmitted to the first image processor 433a. When the characteristic of object corresponds to a single energy X-ray image, the image signal used for evaluation of characteristics of the object is transmitted to the second image processor 433b.

In a case in which the X-ray detector <NUM> converts the entire energy band of X-rays into an image signal, instead of separating the X-ray, when the characteristic of the object corresponds to a multiple energy X-ray, the image X-ray detector acquires image signals of respective energy bands and transmits the same to the first image processor 433a. When the characteristic of the object corresponds to a single energy X-ray image, the image X-ray detector transmits the entire energy band of image signal to the second image processor 433b, or the X-ray detector <NUM> acquires an image signal of the single energy band determined according to type or characteristic of object and transmits the same to the second image processor 433b.

The energy bands separated by the X-ray detector <NUM> or the single energy band may be predetermined by the user or the imaging controller <NUM> depending on type or thickness of object, or by the imaging controller <NUM> depending on object characteristics evaluated by the image analyzer <NUM>.

In an exemplary embodiment, both a multiple energy X-ray image and a single energy X-ray image may be produced and displayed on a display <NUM>.

<FIG> is a flowchart illustrating a method for producing an X-ray image according to an exemplary example. In the present exemplary an image signal acquired during pre-shot is analyzed, in a method for radiating X-rays several times in order to acquire a multiple energy X-ray image.

Referring to <FIG>, for pre-shot, X-rays are radiated to an object (operation <NUM>). The radiated X-ray dose is decreased by decreasing tube current and exposure time, as compared to main imaging and the X-ray energy band may be suitably set according to the object. For example, when imaging the chest, a high energy band of about <NUM> to about <NUM> keV may be set and when imaging the breast, a low energy band of about <NUM> to about <NUM> keV may be set.

In operation <NUM>, X-rays passing through the object are detected. An image signal is acquired (operation <NUM>). As described above, X-rays passing through the object are detected at each pixel by the X-ray detector and the detected X-rays are converted into an electric signal. The electric signal may be an analog signal or a digital signal. When all the electric signals of respective pixels are combined, one image of the object may be acquired and the electric signal corresponds to an image signal of the object.

The acquired image signal is analyzed and object characteristics are evaluated (operation <NUM>). The object characteristics include characteristics affecting image analysis and are associated with inner structures of the object, as for example, at least one of tissue composition, ratios of respective tissues and a ratio of specific tissue of the object.

For example, when imaging the breast, the breast density is determined. The breast density may be represented by a ratio of a parenchymal tissue with respect to the total breast tissue, and a reference value, providing an estimation basis of the parenchymal tissue, may be predetermined according to experiments, statistics or theory.

In operation <NUM>, it is determined that the determined characteristic of the object corresponds to a multiple energy X-ray image (YES), and the multiple energy X-ray image is produced by performing main imaging.

For this purpose, a plurality of X-rays having different energy bands are respectively radiated to the object (operation <NUM>). This means that X-rays are radiated several times from the X-ray generator and the X-rays of different bands may be sequentially radiated. The energy band of the radiated X-rays and the number of X-ray irradiation may be predetermined depending on object type or may be set depending on object characteristics evaluated by analyzing image signals.

The radiated X-ray pass through the object and a plurality of X-rays passing through the object are detected and are converted into a plurality of image signals (operation <NUM>). The flowchart shows that the X-rays are radiated and then detected. This disclosure is given for convenience of description only. In an exemplary example, a first X-ray is radiated, the following X-ray is radiated, and the X-rays are then detected.

The image signals are subjected to multiple energy image processing to produce a multiple energy X-ray image (operation <NUM>). The multiple energy image processing enables one image with an improved contrast between tissues to be acquired from the image signals, as described in detail above.

The produced multiple energy X-ray image is displayed on the display (operation <NUM>). A user analyzes dense breast using a multiple energy X-ray image with an improved contrast between tissues and thereby efficiently determines presence of lesions.

If, in operation <NUM>, it is determined that the determined characteristic of object does not correspond to a multiple energy X-ray image (NO), the characteristic of the object corresponds to a single energy X-ray image, and a single energy X-ray image is produced by performing main imaging.

For this purpose, X-rays having a single energy band are radiated to an object (operation <NUM>). An energy of the radiated X-rays may be the same as an energy of X-rays radiated during pre-shot, but X-ray dose may be increased by increasing tube current and exposure time, as compared to pre-shot.

The X-ray passing through the object is detected (operation <NUM>) and an image signal is acquired (operation <NUM>). The converted image signal is subjected to image processing to produce a single energy X-ray image (operation <NUM>). The image processing means image processing generally used for generation of the X-ray image and a detailed explanation thereof is thus omitted.

The obtained image is displayed on the display (operation <NUM>).

<FIG> is a flowchart illustrating a method for producing an X-ray image according to an exemplary example. In the present exemplary example the pre-shot is not performed.

Referring to <FIG>, an X-ray with a first energy band is radiated to the object (operation <NUM>). The first energy band X-ray may be used for generation of the single energy X-ray image and a first level of energy may be changed depending on object type.

The X-ray passing through the object is detected (operation <NUM>), and a first energy image signal of the object is acquired from the detected X-ray (operation <NUM>). The first energy image signal corresponds to an image signal indicating a general single energy X-ray image.

The first energy image signal is analyzed and characteristics of the object are evaluated (operation <NUM>). The evaluation of object characteristics is described with reference to <FIG> above and a detailed explanation thereof is thus omitted.

Based on a result of evaluation of characteristics of the object, it is determined that the characteristic of object corresponds to a multiple energy X-ray image (operation <NUM>), as for example, when the tissues of the object are dense and/or an image with an improved contrast between the tissues is needed, and a multiple energy X-ray image of the object is produced.

For this purpose, <NUM>nd to nth energy (n≥<NUM>, in which n is an integer) bands of X-rays are radiated to the object (operation <NUM>). The <NUM>nd to nth energy bands are different energy bands and are different from the first energy band. X-rays of different energy bands are sequentially radiated from the X-ray generator and the <NUM>st to nth energy bands may indicate an X-ray irradiation order and may be unrelated to energy levels. The energy level of X-rays and the number (n) of different energy bands may be predetermined depending on object type and may be set depending on object characteristics evaluated by analyzing image signals.

The <NUM>nd to nth energies passing through the object are detected (operation <NUM>) and <NUM>nd to nth energy image signals of the object are acquired from the detected X-rays (operation <NUM>). The flowchart discloses that <NUM>nd to nth energy X-rays are radiated and then detected. This disclosure is given only for convenience of description. In the exemplary example, a second energy X-ray is radiated, the following X-ray is radiated and the X-rays are then detected.

The <NUM>st to nth energy image signals are subjected to multiple energy image processing to produce a multiple energy X-ray image (operation <NUM>), and the produced image is displayed on the display (operation <NUM>). The first energy image signal is the image signal used for evaluation of characteristics of the object.

When it is determined, in operation <NUM>, that object characteristics does not correspond to a multiple energy X-ray image (NO), as for example, when the tissues of the object are not dense and/or detection of lesions or other effects is possible with a single energy X-ray image, the single energy X-ray image of the object is produced.

For this purpose, the acquired first energy image signal is subjected to image processing to produce a first energy X-ray image (operation <NUM>), and the image is displayed on the display (operation <NUM>).

<FIG> is a flowchart illustrating a method for producing an X-ray image according to an exemplary example. In the present exemplary example, the pre-shot is performed.

Referring to <FIG>, X-rays are radiated to the object, for pre-shot (operation <NUM>). The radiated X-ray has a dose or irradiation amount which is decreased by decreasing a tube current and an exposure time, and the X-rays may have an energy band set according to object type and may be a broadband X-ray including a plurality of energy bands.

The X-ray passing through the object is detected (operation <NUM>) and an image signal of the object is acquired from the detected X-ray (operation <NUM>). When the radiated X-ray is a polychromatic X-ray having a predetermined energy band, an energy band suitable for the object may be separated during acquisition of an appropriate image signal. For example, when imaging the breast, an image signal of an energy band of about <NUM> keV or less is acquired.

An image signal of the object is analyzed and characteristics of the object are evaluated (operation <NUM>). The evaluation of characteristics of the object is described in detail above.

In operation <NUM>, it is determined that the determined characteristic of the object corresponds to a multiple energy X-ray image (YES), as for example, when the tissues of the object are dense and/or an image with improved contrast between tissues is needed, and a multiple energy X-ray image of the object is produced.

For this purpose, X-rays are radiated to the object to begin main imaging (operation <NUM>). The radiated X-rays may be polychromatic X-rays having a predetermined energy band and include both a low energy band and a high energy band. For example, when imaging the breast, X-rays with a <NUM>-<NUM> keV band may be radiated.

The X-rays passing through the object are detected (operation <NUM>) and the detected X-rays are divided according to individual energy bands to acquire a plurality of image signals (operation <NUM>). The separation of the energy bands may be predetermined depending on object type or be set in consideration of object characteristics. The image signals are image signals of individual energy bands.

The image signals are subjected to multiple energy image processing to produce a multiple energy X-ray image with improved contrast between tissues (operation <NUM>), and the produced image is displayed on the display (operation <NUM>).

When, in operation <NUM>, it is determined that the characteristic of object does not correspond to a multiple energy X-ray image (NO), as for example, when the tissues of the object are not dense and/or detection of lesions is possible with a single energy X-ray image, a single energy X-ray image of the object is produced.

For this purpose, X-rays are radiated to the object to begin main imaging (operation <NUM>). An X-ray of a specific energy band set according to type or properties of the object may be radiated and a broadband X-ray including the specific energy band may be radiated.

The X-ray passing through the object is detected (operation <NUM>) and an image signal of the object is acquired from the detected X-ray (operation <NUM>). When the radiated X-ray is a broadband X-ray having a specific energy band, an X-ray with a specific energy level set according to type or characteristic of object is separated from the detected broadband X-ray and an image signal corresponding to the corresponding energy level may be acquired.

The acquired image signal is subjected to image processing to produce a single energy X-ray image (operation <NUM>) and the produced image is displayed on the display (operation <NUM>).

<FIG> is a flowchart illustrating a method for producing an X-ray image according to an exemplary example. In the present exemplary example, the pre-shot is not performed.

Referring to <FIG>, an X-ray is radiated to the object (operation <NUM>). The radiated X-ray is an X-ray for main imaging which includes a plurality of energy bands set depending on the object.

The X-ray passing through the object is detected (operation <NUM>) and an image signal of the object is acquired from the detected X-ray (operation <NUM>).

Characteristics of the object are evaluated by analyzing image signals (operation <NUM>). The evaluation of object characteristics is described above.

In operation <NUM>, it is determined that the characteristic of the object corresponds to a multiple energy X-ray image (YES), as for example, when the tissues of the object are dense and/or an image with improved contrast between tissues is needed, and a multiple energy X-ray image of the object is produced.

For this purpose, the X-rays detected in (operation <NUM>) are divided according to individual energy bands and a plurality of image signals corresponding to the energy bands are acquired (operation <NUM>). The divided energy bands may be set depending on type or characteristics of the object.

The acquired image signals are subjected to multiple energy image processing to produce a multiple energy X-ray image (operation <NUM>) and the produced image is displayed on the display (operation <NUM>).

When in operation <NUM>, it is determined that the characteristic of object corresponds to a single energy X-ray image (NO), as for example, when the tissues of the object are not dense and/or detection of lesions is possible with a single energy X-ray image, a single energy X-ray image of the object is produced (operation <NUM>).

For this purpose, the acquired image signal acquired is subjected to image processing to produce a single energy X-ray image (operation <NUM>). That is, an X-ray image corresponding to the entire energy band of the detected X-ray may be produced. As another example, an X-ray with a desired energy band is extracted, an image signal is acquired from the extracted X-ray and production of a single energy X-ray image from the image signal is possible. For example, when imaging the breast, an X-ray with a low energy band (<NUM>-<NUM> keV) may be extracted and when imaging the chest, an X-ray with a high energy band (<NUM>-<NUM> keV) may be extracted.

The produced image is displayed on the display (operation <NUM>) and the user analyzes a single energy X-ray image with superior image quality and thereby detects lesions.

<FIG> is a flowchart illustrating a method for producing an X-ray image according to an exemplary example. In the present exemplary example the pre-shot is not performed and X-rays are separated into individual energy bands before evaluation of object characteristics.

Referring to <FIG>, X-rays are radiated to an object (operation <NUM>). The radiated X-rays are used for main imaging and include a plurality of energy bands predetermined depending on the object.

The X-rays passing through the object are detected (operation <NUM>) and the detected X-rays are divided according to individual energy bands to acquire a plurality of image signals (operation <NUM>). An image signal of the entire energy band may be acquired.

One of the image signals is analyzed and characteristics of the object are evaluated (operation <NUM>). The analyzed image signal may be an image signal of the entire energy band, an image signal of a low energy band or an image signal of a high energy band according to the object.

In operation <NUM>, it is determined that the characteristic of the object corresponds to a multiple energy X-ray image (YES), as for example, the tissues of the object are dense and/or an image with improved contrast between tissues is needed, and a multiple energy X-ray image of the object is produced.

For this purpose, the acquired image signals are subjected to multiple energy image processing to produce a multiple energy X-ray image (operation <NUM>) and the produced image is displayed on the display (operation <NUM>).

If, in operation <NUM>, it is determined that the characteristic of object does not correspond to a multiple energy X-ray image (NO), as for example, the tissues of the object are not dense and/or easy detection of lesions is possible with a single energy X-ray image, a single energy X-ray image of the object is produced.

For this purpose, one of the acquired image signals is subjected to image processing to produce a single energy X-ray image (operation <NUM>) and the produced image is displayed on the display (operation <NUM>).

As apparent from the foregoing, at least one of a single energy X-ray image and a multiple energy X-ray image is produced according to tissue characteristics of the object and efficient image analysis is thus possible.

Claim 1:
An X-ray imaging apparatus comprising:
an X-ray generator (<NUM>) configured to generate and radiate X-rays to an object an X-ray detector (<NUM>) configured to detect the X-rays which have passed through the object and acquire an image signal of the object;
wherein the X-ray detector is configured to acquire a plurality of image signals according to a plurality of individual energy bands;
a memory to store the plurality of image signals; and
a controller (<NUM>) configured to evaluate a characteristic of the object based on one of the image signals and to generate a single energy X-ray image based on one of the image signals stored in the memory and a multiple energy X-ray image based on the plurality of image signals stored in the memory,
wherein the image signal on which the single energy image is based is determined based on the evaluation result of the characteristics of the object;
wherein the X-ray imaging apparatus further comprises a display (<NUM>) and both the multiple energy X-ray image and the single X-ray image are produced and displayed on said display; and
wherein the X-ray generator is configured to radiate the X-rays having an energy band set according to a type or the characteristic of the object.