Radiographic imaging apparatus for obtaining improved radiographic images and method of operating the radiographic imaging apparatus

Abstract

The radiation imaging apparatus of the present disclosure includes an image output unit that outputs a first radiation image included in a series of radiation images acquired by radiation imaging of a subject, an image brightness information extraction unit that acquires brightness information from the first radiation image, a first irradiation condition calculation unit that determines a first irradiation condition based on the brightness information, an irradiation control unit that controls the dose of radiation based on the first irradiation condition, a second irradiation condition calculation unit that determines a second irradiation condition based on a second radiation image generated based on the first irradiation condition when the imaging site of the subject is fixed, and a dose reduction unit that reduces or maintains the dose of radiation based on the second irradiation condition.

Description

Technical Field

[0001] The present disclosure relates to a radiation imaging apparatus for acquiring improved radiation images and a method of operating the radiation imaging apparatus. When acquiring consecutive radiation images, the radiation imaging apparatus determines irradiation conditions by different methods.

Background Art

[0002] Radiation imaging apparatuses that implement low dose are becoming increasingly important in medical imaging because they reduce the risk of side effects. Such apparatuses can achieve low dose using advanced software algorithms, improved hardware components, and new types of radiation sources.

[0003] Radiation imaging apparatuses that achieve low dose are limited in that they may produce images with reduced contrast and spatial resolution. As a result, it may become more difficult to detect small lesions or abnormalities. Also, low-dose imaging may not be suitable for certain types of imaging procedures that require high-dose imaging to visualize specific structures or abnormal findings.

[0004] In addition, radiation imaging apparatuses with low dose are relatively expensive and thus accessibility may be limited. Also, additional education and expertise of radiation technologists and radiation specialists may be required to implement new technologies and techniques, thereby making it difficult to adopt low-dose imaging apparatuses.

[0005] As one of the low-dose radiation imaging devices, a radiation imaging device is widely known as equipment used during surgery and medical procedures by continuously irradiating a diseased part of the human body and animal bodies with X-rays to obtain a fluoroscopic image of the diseased part in real time. When performing a patient's surgery using a radiation imaging device, there is a problem that it is affected by objects other than the objects of interest such as the surgeon's hand and surgical instruments, and it is impossible to maintain a constant image brightness and level due to the influence on the irradiation conditions and image brightness. In addition, since the existing automatic irradiation condition adjustment method uses irradiation conditions that can be used for various subjects, more radiation can be irradiated than the appropriate irradiation amount for the subject during actual imaging.

[0006] Despite such limitations, there is a need to use a low-dose radiation imaging device for medical imaging in that the risk of side effects can be reduced and patient safety can be improved by minimizing radiation exposure. Therefore, various studies are being conducted to implement a low-dose radiation imaging device.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present disclosure discloses a radiation imaging device that implements a low-dose radiation image. More specifically, the radiation imaging device quickly obtains a low-dose radiation image and minimizes the burden on patients and users.

Means for Solving the Problems

[0008] The radiation imaging device according to the present disclosure includes an image output unit that outputs a first radiation image included in a continuous radiation image obtained by radiation imaging of a subject, an image brightness information extraction unit that obtains brightness information from the first radiation image, a first irradiation condition calculation unit that determines a first irradiation condition based on the brightness information, an irradiation control unit that controls the dose of radiation based on the first irradiation condition, a second irradiation condition calculation unit that determines a second irradiation condition based on a second radiation image generated based on the first irradiation condition when the imaging site of the subject is fixed, and a dose reduction unit that reduces or maintains the dose of radiation based on the second irradiation condition.

[0009] The value obtained by subtracting the radiation dose based on the second irradiation condition from the radiation dose based on the first irradiation condition of the radiation imaging apparatus according to the present disclosure is less than or equal to 70% of the dose based on the first irradiation condition.

[0010] When the dose is decreased by the dose reduction unit, the radiation imaging apparatus according to the present disclosure deactivates the first irradiation condition calculation unit.

[0011] The radiation imaging apparatus according to the present disclosure accumulatively averages the pixel values included in the current frame image included in the third radiation image output by the dose decreased by the dose reduction unit and the previous frame image included in the third radiation image to generate an improved current frame image.

[0012] The radiation imaging apparatus according to the present disclosure further includes an image post-processing unit that performs post-processing on the third radiation image output by the dose decreased by the dose reduction unit, and the image post-processing unit adjusts at least one of the brightness information and the contrast information of the third radiation image so as to be similar to at least one of the brightness information and the contrast information of the second radiation image.

[0013] The radiation imaging apparatus according to the present disclosure includes a radiation irradiation unit that irradiates a subject with radiation, an image acquisition unit that receives the radiation irradiated from the radiation irradiation unit and that has passed through the subject to generate a continuous radiation image, and a control unit that controls the radiation irradiation unit and the image acquisition unit. The method of operating the radiation imaging apparatus includes: a step of the control unit acquiring brightness information based on a first radiation image included in the continuous radiation images; a step of determining a first irradiation condition based on the brightness information by a first algorithm; a step of controlling the dose of the radiation based on the first irradiation condition; a step of acquiring a second radiation image included in the continuous radiation images and generated based on the first irradiation condition; a step of acquiring movement presence / absence information indicating whether or not the imaging site of the subject is fixed; when the movement presence / absence information indicates that the imaging site of the subject is fixed, a step of determining a second irradiation condition based on the second radiation image by a second algorithm; a step of controlling the dose of the radiation based on the second irradiation condition; and a step of acquiring a third radiation image included in the continuous radiation images and generated based on the second irradiation condition.

[0014] The radiation dose based on the second irradiation condition in the method of operating the radiation imaging apparatus according to the present disclosure is greater than or equal to 30% of the radiation dose based on the first irradiation condition.

[0015] The first algorithm for determining the first irradiation condition and the second algorithm for determining the second irradiation condition in the method of operating the radiation imaging apparatus according to the present disclosure are different from each other.

[0016] The step of acquiring the third radiation image in the method of operating the radiation imaging apparatus according to the present disclosure includes a step of generating an improved current frame image by cumulatively averaging pixel values included in at least a part of the current frame image included in the third radiation image and pixel values included in at least a part of the previous frame image included in the third radiation image.

[0017] The step of obtaining a third radiation image in the operation method of the radiation imaging apparatus according to the present disclosure includes generating a motion perception image including motion perception information for each pixel of a difference image obtained by the difference between the current frame image included in the third radiation image and the previous frame image included in the third radiation image, generating a motion probability image based on the generated motion perception image and the motion perception image accumulated up to the previous frame, and generating an improved current frame image by mixing the current frame image and the previous frame image based on the motion probability image.

[0018] The step of generating a motion probability image in the operation method of the radiation imaging apparatus according to the present disclosure includes generating a motion probability image by summing one or more of the motion perception image of the current frame and the motion perception image up to the previous frame. The step of generating an improved current frame image includes variably determining a mixing ratio of the current frame image and the previous frame image based on a value indicating the degree of motion of each pixel of the motion probability image. The mixing ratio is determined such that the larger the degree of motion indicated by the value of each pixel of the motion probability image, the larger the reflection ratio of the current frame image compared to the previous frame image.

[0019] The step of obtaining brightness information in the operation method of the radiation imaging apparatus according to the present disclosure includes obtaining brightness information by averaging pixel values included in at least a part of the first radiation image. The step of determining the first irradiation condition includes determining the first irradiation condition so that the brightness information increases when the brightness information is smaller than a predetermined first critical brightness information, and determining the first irradiation condition so that the brightness information decreases when the brightness information is larger than the predetermined first critical brightness information.

[0020] The step of obtaining brightness information by averaging pixel values included in at least a part of the first radiation image in the operation method of the radiation imaging apparatus according to the present disclosure includes obtaining an area where the subject appears from the first radiation image based on a subject area acquisition model and obtaining brightness information by averaging pixel values included in the area where the subject appears.

[0021] The step of determining the second irradiation condition of the operation method of the radiation imaging apparatus according to the present disclosure includes the steps of: downsampling the second radiation image in units of patches of a predetermined size to obtain a downsampled image; obtaining the minimum pixel value among the pixel values included in the downsampled image; and when the minimum pixel value is greater than the predetermined second critical brightness information, determining the second irradiation condition so that the minimum pixel value becomes the same as the second critical brightness information.

[0022] The step of determining the second irradiation condition so that the minimum pixel value of the operation method of the radiation imaging apparatus according to the present disclosure becomes the same as the second critical brightness information includes the steps of: determining a reduction ratio based on the minimum pixel value and the second critical brightness information; and determining the second irradiation condition so that the dose obtained by subtracting the value obtained by multiplying the dose by the first irradiation condition by the reduction ratio from the dose by the first irradiation condition is irradiated from the radiation irradiation unit. The reduction ratio is greater than 0 and less than the predetermined maximum reduction ratio.

[0023] The step of obtaining movement presence / absence information of the operation method of the radiation imaging apparatus according to the present disclosure includes the steps of: when the time at which at least one of the first radiation image and the second radiation image is obtained is less than a predetermined critical time, determining the movement presence / absence information so as to indicate that the imaging part of the subject was not fixed; and when the time at which at least one of the first radiation image and the second radiation image is obtained is equal to or greater than the predetermined critical time, determining the movement presence / absence information so as to indicate that the imaging part of the subject was fixed.

[0024] In addition, a program for implementing the operation method of the radiation imaging apparatus as described above can be recorded on a computer-readable recording medium.

Advantages of the Invention

[0025] The radiographic imaging apparatus of the present disclosure can explicitly fix the image brightness to solve the above-described problems. Further, when it is determined that the imaging region is fixed, the radiographic imaging apparatus can reduce the radiation exposure dose of the patient by using optimized irradiation conditions adapted to the corresponding region.

[0026] The radiographic imaging apparatus of the present disclosure can minimize the radiation exposure doses of the patient and the user by acquiring a low-dose radiographic image. Further, the radiographic imaging apparatus of the present disclosure can be useful for the medical judgment of the user by providing an image that is both low-dose and has high sharpness. Further, the radiographic imaging apparatus of the present disclosure can acquire a low-dose radiographic image quickly by minimizing image processing, thus assisting the user in performing a medical procedure promptly.

Brief Description of the Drawings

[0027]

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Best Mode for Carrying Out the Invention

[0028] The advantages and features of the disclosed embodiments, and the methods for achieving them, will become clear by referring to the embodiments described below together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, and can be embodied in various different forms. Merely, these embodiments are provided so that the present disclosure becomes complete and fully conveys the scope of the invention to those having ordinary knowledge in the technical field to which the present disclosure pertains.

[0029] The terms used in this specification will be briefly explained, and the disclosed embodiments will be specifically described.

[0030] The terms used in this specification are general terms that are currently widely used as much as possible while considering their functions in the present disclosure. However, this can change depending on the intentions or precedents of those skilled in the relevant fields, the emergence of new technologies, etc. Also, in certain cases, there are terms arbitrarily selected by the applicant, and in such cases, the meaning thereof will be described in detail in the explanatory part of the corresponding invention. Therefore, the terms used in the present disclosure must be defined based on the meaning of the terms and the overall content of the present disclosure.

[0031] The singular expressions in this specification include plural expressions unless specifically specified as singular in the context. Also, plural expressions include singular expressions unless specifically specified as plural in the context.

[0032] When a component is described as "including" a part that is the entire specification, this means that, unless there is a specifically contrary description, it can further include other components rather than excluding other components.

[0033] Also, the term "unit" as used in the specification means a software or hardware component, and the "unit" performs a predetermined role. However, the "unit" is not meant to be limited to software or hardware. The "unit" may be configured to be in a storage medium that can be addressed, or may be configured to reproduce one or more processors. Thus, by way of example, the "unit" includes components such as software components, object-oriented software components, class components and task components, and processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays and variables. The functions provided within the components and "units" may be combined with a smaller number of components and "units" or further separated with additional components and "units".

[0034] According to one embodiment of the present disclosure, the "unit" may be implemented by a processor and a memory. The term "processor" must be broadly interpreted to include general-purpose processors, central processing units (CPUs), microprocessors, digital signal processors (DSPs), controllers, microcontrollers, state machines, etc. In some environments, the "processor" may refer to an application-specific integrated circuit (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), etc. The term "processor" may refer to a combination of processing devices such as, for example, a combination of a DSP and a microprocessor, a combination of multiple microprocessors, a combination of one or more microprocessors coupled with a DSP core, or any other such configuration combination.

[0035] The term "memory" should be broadly construed to include any electronic component capable of storing electronic information. The term "memory" may refer to various types of processor-readable media such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage devices, registers, etc. When a processor can read information from / to or record information in the memory, the memory is said to be in electronic communication with the processor. Memory integrated into a processor is in electronic communication with the processor.

[0036] Hereinafter, with reference to the accompanying drawings, the present disclosure will be described in detail so that those having ordinary knowledge in the technical field to which the present disclosure pertains can easily implement the embodiments. And parts not related to the description are omitted to clearly explain the present disclosure in the drawings.

[0037] FIG. 1 is a diagram showing a mobile radiation imaging apparatus according to an embodiment of the present disclosure.

[0038] FIG. 1 illustrates an example of a C-arm type radiation imaging apparatus 100 according to an embodiment of the present disclosure. However, the present disclosure is not limited thereto, and the radiation imaging apparatus 100 of the present disclosure can have various forms.

[0039] The radiation imaging apparatus according to an embodiment of the present disclosure can be configured in a C-arm form as shown in FIG. 1, for example, to acquire a moving image. The radiation imaging apparatus can image a region of interest of a subject S, which is an imaging target, using radiation such as X-rays.

[0040] Referring to FIG. 1, the radiographic imaging apparatus 100 can include a radiation irradiation unit 111 that outputs radiation, for example, X-rays, and an image acquisition unit 112 that receives the incidence of the radiation transmitted through the subject S to acquire image data. The radiation irradiation unit 111 and the image acquisition unit 112 can be supported at both end portions of the C-arm 110. For example, the radiographic imaging apparatus can be applied to a mobile C-arm X-ray imaging apparatus, an interventional X-ray device, an interventional angiography C-arm X-ray device, and the like.

[0041] The support structure supports the radiation irradiation unit 111 and the image acquisition unit 112, and is configured to be able to change the spatial position and the rotational position of the radiation irradiation unit 111 and the image acquisition unit 112 for changing the imaging position and angle of the subject S and the like. For example, the support structure can include a support body 150, a lift column 130 fastened to the support body 150 so as to be movable in the vertical direction D1, and a forward and backward arm 120 that is movable in the vertical direction together with the lift column 130 and is fastened to the lift column 130 so as to be relatively movable in the horizontal direction D2 with respect to the lift column 130.

[0042] The C-arm 110 is fastened to the reciprocating arm 120 so as to be relatively rotatable with respect to the reciprocating arm 120 in at least one rotational direction, and the radiation irradiation unit 111 and the image acquisition unit 112 are respectively fastened to both side ends of the C-arm 110. At this time, the C-arm 110 can move up and down in the vertical direction and move forward and backward in the horizontal direction together with the reciprocating arm 120, and can be fastened to the reciprocating arm 120 so as to be relatively rotatable in at least one rotational direction with respect to the reciprocating arm 120, for example, the orbital rotation direction R1 and the axial rotation direction R2 centered on the direction parallel to the horizontal movement direction of the reciprocating arm 120. Although not shown in the drawings, the support structure can include actuators such as motors for the vertical movement of the lift column 130, the horizontal movement of the reciprocating arm 120, and the rotation of the C-arm 110. Elements for supporting and driving the C-arm 110, which is a support member for supporting the radiation irradiation unit 111 and the image acquisition unit 112, that is, the reciprocating arm 120, the lift column 130, and the actuators provided therein, can be said to be driving elements for driving the C-arm 110, and the combination thereof can be said to be a driving unit for driving the C-arm 110. Further, it may be configured such that panning rotation of the C-arm 110 is possible through the lateral rotation of the reciprocating arm 120. The form of the support member is not limited to the C shape, and in other embodiments of the present disclosure, arms such as a U shape, a G shape, an O shape, etc. may be used as the support member instead of the C shape.

[0043] The display unit 140 is configured to display at least one or more of real-time position information, image data, reference position information, and radiation output information. The display unit 140 may be any device capable of information and image display, for example, a printer, a CRT display, an LCD display, a PDP display, an OLED display, an FED display, an LED display, a DLP display, a PFD display, a 3D display, a transparent display, etc. Further, the display unit 140 may be embodied in a form capable of information display and input such as a touch screen that can receive input from a user.

[0044] FIG. 2 is a diagram showing a block diagram of various configurations that may be included in a radiation imaging apparatus according to an embodiment of the present disclosure.

[0045] Referring to FIG. 2, the radiation imaging apparatus 100 may include at least one of a control unit 200, a sensor unit 210, a communication unit 220, a memory 230, an output unit 240, and an input unit 250. FIG. 1 schematically shows the appearance of the radiation imaging apparatus 100, while FIG. 2 shows a block diagram functionally dividing the radiation imaging apparatus 100. At least one of the control unit 200, the sensor unit 210, the communication unit 220, the memory 230, the output unit 240, and the input unit 250 in FIG. 2 may be included inside at least one of the radiation irradiation unit 111, the image acquisition unit 112, the support body 150, the lift column 130, and the forward / backward moving arm 120 in FIG. 1, or may be coupled to the outside of at least one of the radiation irradiation unit 111, the image acquisition unit 112, the support body 150, the lift column 130, and the forward / backward moving arm 120.

[0046] The radiation imaging apparatus 100 according to an embodiment of the present disclosure may include a control unit 200. The control unit 200 may be embodied in the form of an information processing device such as one or more computers capable of information processing and calculation. For example, the computer may include control means such as a CPU, storage means such as a ROM (read only memory) or a RAM (random access memory), and graphic control means such as a GPU (graphics processing unit). Also, the computer may include communication means such as a network card and input / output means such as a keyboard, a display, or a touch screen. Such components of the computer may be connected through a bus as is known and may operate and be controlled by the execution of a program stored in the storage means.

[0047] The radiation image capturing apparatus 100 that can be embodied in the form of a computer capable of information processing can be installed in the radiation image capturing apparatus 100 shown in FIG. 1 and configured to execute an image processing function. In this case, it can be configured to receive and process an image captured as a part of the radiation image capturing apparatus, and display the processed image on the display unit 140 of the radiation image capturing apparatus.

[0048] The radiation image capturing apparatus 100 can include a sensor unit 210. The sensor unit 210 can acquire various information using at least one sensor. The sensor unit 210 can be equipped with sensors that utilize measurement means such as pressure, potential, and optics. For example, the sensor unit 210 can include at least one of a distance measurement sensor or an encoder. Also, the sensor can include a pressure sensor, an infrared sensor, an LED sensor, a touch sensor, and the like. However, it is not limited thereto. The sensor unit may be included in at least one of the radiation irradiation unit 111, the image acquisition unit 112, the support body 150, the lift column 130, the forward and backward movement arm 120, and the C-arm 110.

[0049] Furthermore, the radiographic imaging apparatus 100 can include a communication unit 220. The communication unit 220 may be a configuration for the radiographic imaging apparatus 100 to communicate with internal modules or external devices wirelessly or by wire. The external devices can include an external server and a user terminal. The user terminal can include a PC, a smartphone, a tablet, or a wearable device. The communication unit 220 can include a wired / wireless communication module for network connection. As the wireless communication technology, for example, WLAN (Wireless LAN) (Wi-Fi), Wibro (Wireless broadband), Wimax (World Interoperability for Microwave Access), HSDPA (High Speed Downlink Packet Access), etc. can be used. As the wired communication technology, for example, XDSL (Digital Subscriber Line), FTTH (Fibers to the home), PLC (Power Line Communication), etc. can be used. Also, the network connection unit can include a short-range communication module to transmit and receive data with any device / terminal located in the short range. For example, as the short-range communication technology, Bluetooth (registered trademark), RFID (Radio Frequency Identification), infrared communication (IrDA, infrared Data Association), UWB (Ultra-Wideband), ZigBee, etc. can be used, but not limited thereto.

[0050] The radiation imaging apparatus 100 can include a memory 230. The control unit 200 can execute the instruction words stored in the memory. The control unit 200 and the memory 230 may be independent hardware, but are not limited thereto, and the control unit 200 may include the memory 230. That is, the memory 230 may be included in the control unit 200 or may be external to the control unit 200. The memory 230 can store various information related to the radiation imaging apparatus 100. For example, the memory 230 can include information related to the operation method of the radiation irradiation unit 111, and can include captured images and user authentication information, but is not limited thereto.

[0051] The memory 230 can be implemented through a non-volatile storage medium that can persistently store any data. For example, the memory 230 can include, but is not limited to, a disk, an optical disk, and a magneto-optical storage device, as well as a storage device based on a flash memory and / or a battery backup memory. The memory 230 can be a main storage device directly accessible by a processor, such as a random access memory (RAM) like a dynamic RAM (DRAM) or a static RAM (SRAM), and can mean a volatile storage device in which the stored information is instantaneously erased when the power is turned off, but is not limited thereto. Such a memory 230 can be operated by the control unit 200. Also, the control unit 200 can execute the instruction words included in the memory 230.

[0052] Also, the radiation imaging apparatus 100 can further include an operation unit that provides an interface for the operation of the radiation imaging apparatus 100. The operation unit can include an output unit 240 and an input unit 250.

[0053] The output unit 240 can output sounds and images that indicate imaging-related information such as X-ray irradiation or confirm the state of the main body under the control of the control unit 200. The output unit 240 can include the display unit 140. The output unit 240 can include a speaker or a display. The output unit 240 can output a medical image generated by the control unit 200. The output unit 240 can output information necessary for the user to operate the radiation imaging apparatus 100, such as a UI (user interface), user information, or subject information. Examples of the output unit 240 can include a speaker, a printer, a CRT display, an LCD display, a PDP display, an OLED display, a FED display, an LED display, a VFD display, a DLP display, an FPD display, a 3D display, a transparent display, etc., and can include various output devices within the scope obvious to those skilled in the art.

[0054] The radiation imaging apparatus 100 may be wirelessly connected to a workstation. The workstation may exist in a space physically separated from the radiation imaging apparatus 100.

[0055] The workstation can include a storage server. The storage server may store medical images, information about the subject, information about the user (medical personnel), etc. The workstation can include a review device. The review device can receive a medical image from the storage server based on a user's command and diagnose the medical image. The workstation and the radiation imaging apparatus 100 can transmit, store, process, and output data according to the DICOM (Digital Imaging and Communications in Medicine) standard. Also, the workstation can include a PACS (Picture Archiving and Communication System).

[0056] The workstation can include an output unit, an input unit, and a control unit. The output unit and the input unit provide an interface for the user to operate the workstation and the radiation imaging apparatus 100. The control unit of the workstation can control the workstation and the radiation imaging apparatus 100.

[0057] The radiation imaging apparatus 100 can be controlled through the workstation and can also be controlled by the control unit 200 included in the radiation imaging apparatus 100. Therefore, the user can control the radiation imaging apparatus 100 through the workstation or can also control the radiation imaging apparatus 100 through the operation unit and the control unit 200 included in the radiation imaging apparatus 100. In other words, the user may remotely control the radiation imaging apparatus 100 through the workstation or may directly control the radiation imaging apparatus 100.

[0058] The control unit of the workstation and the control unit 200 of the radiation imaging apparatus 100 may be separate, but are not limited thereto. The control unit of the workstation and the control unit 200 of the radiation imaging apparatus 100 may be embodied as one integrated control unit, and the integrated control unit may be included in only one of the workstation and the radiation imaging apparatus 100. Hereinafter, the control unit 200 can mean the control unit of the workstation and / or the control unit of the radiation imaging apparatus 100.

[0059] The output unit and the input unit of the workstation and the output unit 240 and the input unit 250 of the radiation imaging apparatus 100 can each provide an interface for the user to operate the radiation imaging apparatus 100. The workstation and the radiation imaging apparatus 100 can each include an output unit and an input unit, but are not limited thereto. The output unit or the input unit may be embodied in only one of the workstation and the radiation imaging apparatus 100.

[0060] Hereinafter, the input unit 250 means the input unit of the workstation and / or the input unit of the radiographic imaging apparatus 100, and the output unit 240 means the output unit of the workstation and / or the output unit of the radiographic imaging apparatus 100.

[0061] The input unit 250 can receive commands for operating the radiographic imaging apparatus 100 from the user and input various types of information related to X-ray imaging. The control unit 200 can control or operate the radiographic imaging apparatus 100 based on the information input to the input unit 250. The input unit 250 can include a joystick, a keyboard, a mouse, a touch screen, a shooting button, an unlocking button, a voice recognition device, a fingerprint recognition device, an iris recognition device, and a human motion recognition device, etc., and can also include other input devices obvious to those skilled in the art.

[0062] The user can input a command for X-ray irradiation through the input unit 250, and the input unit 250 can be provided with a switch for inputting such a command. The switch can be provided such that an irradiation command for X-ray irradiation is input when it is pressed at least once.

[0063] For example, when the user presses the switch, the switch can have a structure in which a preparation command for instructing preheating for X-ray irradiation is input, and when the switch is pressed deeper in that state, an irradiation command for substantial X-ray irradiation is input. When the user operates the switch in this way, the control unit 200 generates a signal corresponding to the command input through the operation of the switch, that is, a preparation signal, and transmits it to a high-voltage generation unit that generates a high voltage for X-ray generation. The high-voltage generation unit can be included in the radiation irradiation unit 111.

[0064] The high-voltage generation unit included in the radiation irradiation unit 111 receives the preparation signal transmitted from the control unit 200 and starts preheating. When the preheating is completed, it transmits the preparation completion signal to the control unit 200. And although the image acquisition unit 112 also needs to prepare for X-ray detection for X-ray detection, the control unit 200 transmits the preparation signal to the image acquisition unit 112 so that the image acquisition unit 112 can be prepared to detect the X-ray transmitted through the subject along with the preheating of the high-voltage generation unit. When the image acquisition unit 112 receives the preparation signal, it prepares for detecting X-rays, and when the detection preparation is completed, it transmits the detection preparation completion signal to the control unit 200.

[0065] When the preheating of the high-voltage generation unit included in the radiation irradiation unit 111 is completed and the X-ray detection preparation of the image acquisition unit 112 is completed, the control unit 200 transmits the irradiation signal to the high-voltage generation unit. The high-voltage generation unit generates a high voltage and applies it to the X-ray source included in the radiation irradiation unit 111, and the X-ray source irradiates X-rays. The X-ray source can vary the irradiation dose of X-rays by at least one of the tube voltage, tube current, and irradiation time of the X-ray pulse controlled by the control unit 200.

[0066] When transmitting the irradiation signal, the control unit 300 can transmit a sound or light output signal to the output unit 240 so that the subject or the user can know the irradiation of X-rays, and a predetermined sound or light is output by the output unit 240. Also, the output unit 240 can output a sound or light indicating other photographing-related information in addition to the irradiation of X-rays. The output unit 240 may be included in the operation unit, but is not limited thereto. The output unit 240 or a part of the output unit 240 can be located at a location different from the location where the operation unit is located. For example, it may be located on the wall of the photographing room where X-ray photographing of the subject is performed.

[0067] The control unit 200 controls the positions of the radiation irradiation unit 111 and the image acquisition unit 112, the photographing timing, the photographing conditions, etc. according to the photographing conditions set by the user.

[0068] Specifically, the control unit 200 controls the high-voltage generation unit and the image acquisition unit 112 according to instructions input through the input unit 250 to control the X-ray irradiation timing, X-ray intensity, X-ray irradiation area, and the like. Further, the control unit 200 adjusts the position of the image acquisition unit 112 according to predetermined imaging conditions and controls the operation timing of the image acquisition unit 112.

[0069] In addition, the control unit 200 generates a medical image of the subject using the image data received through the image acquisition unit 112. Specifically, the control unit 200 can receive the image data from the image acquisition unit 112, remove the noise of the image data, adjust the dynamic range and interleaving, and generate a medical image of the subject.

[0070] The workstation can further include a communication unit (not shown) that can be connected to a server, a medical device, a portable terminal, and the like through a network. The workstation may be one of external devices.

[0071] Hereinafter, the control unit 200 according to an embodiment of the present disclosure will be described in more detail. The control unit 200 can include at least one of at least one hardware module or at least one software module. Here, the module can mean at least one of hardware or software divided into functional units. More specifically, the control unit 200 of the radiation image imaging apparatus 100 can include at least one of an image output unit 201, an image brightness information extraction unit 202, a first irradiation condition calculation unit 203, an irradiation control unit 204, a second irradiation condition calculation unit 205, and a dose reduction unit 206.

[0072] The image output unit 201 may be configured to output a first radiation image included in a continuous radiation image obtained by radiographing a subject. The image output unit 201 may be configured to be included in the control unit 200 and process the data obtained from the image acquisition unit 112 to generate a continuous radiation image. However, it is not limited thereto, and the image output unit 201 may be configured to be included in the output unit 240 and display the image generated by the control unit 200. The continuous radiation image can be called, for example, at least one of an X-ray video, an X-ray motion imaging, or a fluoroscopy.

[0073] The radiation image capturing device 100 can acquire a continuous radiation image. That is, the radiation image capturing device 100 can acquire a moving image. The continuous radiation image can include a plurality of still radiation images. In the present disclosure, the still radiation image can be said to be a frame image.

[0074] The first radiation image can be included in the continuous radiation image. The first radiation image can include at least one frame image. The first radiation image may be an image obtained by image processing at least one frame image. The radiation image capturing device 100 may store predetermined irradiation conditions. The predetermined irradiation conditions can include at least one of a predetermined tube voltage, a predetermined tube current, and an irradiation time of a predetermined X-ray pulse. The predetermined irradiation conditions may be stored by the radiation image capturing device 100 and can be automatically selected at the time of imaging. Also, the predetermined irradiation conditions may be by the user's selection. The radiation image capturing device 100 controls the radiation irradiation unit 111 based on the predetermined irradiation conditions to irradiate the subject with radiation, and the image acquisition unit 112 can acquire the first radiation image.

[0075] The first radiographic image can include an image of a subject. In order for the subject to appear clearly in the radiographic image, it may be necessary to change the irradiation conditions according to the subject information. However, since the first radiographic image uses predetermined irradiation conditions, it may not be an optimized image according to the subject information. Here, the subject information can include at least one of the thickness of the subject, the type of the subject, the part of the subject, the material of the subject, and the density of the subject. Therefore, the radiographic imaging apparatus 100 can implement low dose and determine optimized irradiation conditions for the subject by further including the following configuration.

[0076] The image brightness information extraction unit 202 can include the step of acquiring brightness information from the first radiographic image. The image brightness information extraction unit 202 can be included in the control unit 200.

[0077] The region of interest may be automatically extracted and may not require user intervention. The image brightness information extraction unit 202 can acquire brightness information based on at least one of statistical values such as the maximum value, minimum value, average value, median value, and standard deviation of pixels, and at least one of the distribution degree of pixel values (for example, histogram), feature points extracted from the image, and the positions of the feature points. The process by which the image brightness information extraction unit 202 acquires brightness information will be described later.

[0078] The first irradiation condition calculation unit 203 can determine the first irradiation condition based on the brightness information. The first irradiation condition calculation unit 203 can also be included in the control unit 200. The first irradiation condition calculation unit 203 may be a configuration for controlling so that the brightness information of the first radiographic image is similar to the predetermined brightness information. The first irradiation condition may be information for controlling the radiation irradiation unit 111. The first irradiation condition can include at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse.

[0079] The first irradiation condition calculation unit 203 can determine at least one value among the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse of the radiation irradiation unit 111 based on the brightness information of the first radiation image. For example, the higher at least one of the first tube voltage and the first tube current, the greater the X-ray dose can be. The irradiation time of the first X-ray pulse is a value proportional to the time when the X-ray source emits X-rays, and the longer the irradiation time of the first X-ray pulse, the greater the X-ray dose can be. Also, the brightness information of the first radiation image can become brighter as the irradiation dose increases. However, it is not limited to this, and the brightness information of the first radiation image can become darker as the irradiation dose increases. The first irradiation condition calculation unit 203 can determine a first irradiation condition including at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse for the brightness information of the first radiation image to be similar to the predetermined brightness information. The first irradiation condition may be different from the predetermined irradiation condition. However, in a specific case, the first irradiation condition may be the same as the predetermined irradiation condition.

[0080] The irradiation control unit 204 can control the radiation dose based on the first irradiation condition. The irradiation control unit 204 may be included in the control unit 200. The irradiation control unit 204 can control the operation of the radiation irradiation unit 111 based on the first irradiation condition including at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse obtained from the first irradiation condition calculation unit 203.

[0081] The radiation irradiation unit 111 can irradiate the subject with radiation based on the first irradiation condition. The image acquisition unit 112 can acquire a second radiation image based on the radiation based on at least one of the determined tube voltage, tube current, and irradiation time of the X-ray pulse. The second radiation image may be a radiation image generated after the first radiation image. The second radiation image may be included in a series of radiation images. The second radiation image can include at least one frame image in the video.

[0082] Also, if the first radiographic image is an image based on predetermined irradiation conditions, the second radiographic image may be an image based on the first irradiation conditions. Since the subject appearing in the second radiographic image is similar to the predetermined brightness information, the subject can appear clearly in the second radiographic image. Therefore, the user can easily diagnose the patient based on the second radiographic image. However, the second radiographic image may not be based on the minimum dose. The radiographic imaging apparatus 100 can further execute the following process in order to utilize the minimum dose and maintain the image quality.

[0083] The second irradiation condition calculation unit 205 may be included in the control unit 200. When the imaging site of the subject is fixed, the second irradiation condition calculation unit 205 can determine the second irradiation condition based on the second radiographic image generated based on the first irradiation condition. The second irradiation condition may be an irradiation condition for maintaining the image quality and realizing the minimum dose. The second irradiation condition may be different from the first irradiation condition. However, in a specific case, the second irradiation condition may be the same as the first irradiation condition. The second irradiation condition can include at least one of the second tube voltage, the second tube current, and the irradiation time of the second X-ray pulse. The second irradiation condition may be the minimum irradiation condition for maintaining the image quality of the fixed imaging site to be similar to the image quality by the first irradiation condition.

[0084] The value obtained by subtracting the radiation dose based on the second irradiation condition from the radiation dose based on the first irradiation condition may be smaller than or equal to 70% of the dose based on the first irradiation condition. That is, the radiation dose based on the second irradiation condition may be the same as 30% or more than 30% of the radiation dose based on the first irradiation condition. Since the radiation dose based on the second irradiation condition is smaller than the radiation dose based on the first irradiation condition in this way, the patient or the user can be exposed to less radiation. However, the radiographic imaging apparatus 100 of the present disclosure can improve the convenience of the user while protecting the health of the patient and the user by providing images of the same quality.

[0085] The dose reduction unit 206 can reduce or maintain the dose of radiation based on the second irradiation condition. The dose reduction unit 206 may be included in the control unit 200. The dose reduction unit 206 may be independent of the irradiation control unit 204. However, without being limited thereto, the dose reduction unit 206 may have the same configuration as the irradiation control unit 204.

[0086] The dose reduction unit 206 can control the dose of radiation based on the second irradiation condition. The dose reduction unit 206 can control the operation of the radiation irradiation unit 111 based on the second irradiation condition including at least one of the second tube voltage, the second tube current, and the irradiation time of the second X-ray pulse obtained from the second irradiation condition calculation unit 205.

[0087] The radiation irradiation unit 111 can irradiate the subject with radiation based on the second irradiation condition. The image acquisition unit 112 can acquire a third radiation image based on the radiation based on at least one of the determined second tube voltage, the second tube current, and the irradiation time of the second X-ray pulse. The third radiation image may be a radiation image generated after the second radiation image. The third radiation image may be included in a series of radiation images. The third radiation image can include at least one frame image in the video.

[0088] Also, if the second radiation image is an image based on the first irradiation condition, the third radiation image may be an image based on the second irradiation condition. The third radiation image can maintain almost the same quality as the second radiation image. That is, the sharpness and noise of the subject appearing in the third radiation image may be almost the same as the sharpness and noise of the subject appearing in the second radiation image. However, the dose of radiation irradiated to the subject to acquire the third radiation image may be smaller than or the same as the dose of radiation irradiated to the subject to acquire the second radiation image.

[0089] When the dose is reduced by the dose reduction unit 206, the first irradiation condition calculation unit 203 can be deactivated. That is, the radiation image capturing apparatus 100 may not acquire the first irradiation condition by the first irradiation condition calculation unit 203. The radiation image capturing apparatus 100 can avoid adjusting the subject of consecutive radiation images to predetermined brightness information. The radiation image capturing apparatus 100 can capture consecutive radiation images based on the second irradiation condition. The radiation image capturing apparatus 100 can capture a third radiation image using the minimum dose based on the second irradiation condition. The condition for obtaining the second irradiation condition is that the subject is fixed. When the subject does not move, a high-quality radiation image can be obtained even using the minimum dose. Therefore, the side effects of radiation on the user and the patient can be reduced.

[0090] Further, the radiation image capturing apparatus 100 can generate an improved current frame image by cumulatively averaging the pixel values included in the current frame image included in the third radiation image output by the dose reduced by the dose reduction unit 206 and the previous frame image included in the third radiation image. In the present disclosure, the pixel value may be the pixel value of a pixel included in the display, or may be a pixel value indicating the degree to which one of a plurality of pixels included in the image acquisition unit 112 is excited by radiation. The pixel value can have a value of 10 bits or more and 16 bits or less.

[0091] As already described, the third radiation image can include at least one frame image. The third radiation image can include a current frame image 830 and a previous frame image 820. The current frame image may be the frame most recently acquired through the image acquisition unit 112. The previous frame image 820 may be at least one frame image acquired before the current frame image. The previous frame image 820 can include the immediately previous frame image 822, the n-2 frame image 821, and the like. The immediately previous frame image may be the frame immediately before the current frame image.

[0092] The radiographic imaging apparatus 100 can generate an improved current frame image by accumulating and averaging the current frame image and a predetermined number of previous frame images. The predetermined number may be greater than or equal to 1. The predetermined number can mean the number of frames. The radiographic imaging apparatus 100 can cumulatively average the pixel value of one pixel of the current frame image and the pixel value of the previous frame image at the position corresponding to one pixel of the current frame image. The radiographic imaging apparatus 100 can obtain the pixel value included in the improved current frame image by cumulatively averaging the pixel values of the pixels corresponding to each other in the current frame image and the previous frame image. The pixels corresponding to each other mean that the positions (coordinate values) of the pixels in the current frame image and the positions (coordinate values) of the pixels in the previous frame image are the same as each other. The radiographic imaging apparatus 100 can generate an improved current frame image by obtaining the cumulative average value of all the pixels included in the current frame image and all the pixels included in the previous frame image.

[0093] As already described, since the subject does not move, the change in the pixel value of the pixels at the same position in the consecutive frame images is small. Therefore, when obtaining the improved current frame image by cumulative averaging as described above, the influence of noise can be minimized. The reason is that noise occurs while the pixel value of the pixel changes significantly.

[0094] The radiation imaging apparatus 100 may further include an image post-processing unit 207 that post-processes the third radiation image output with the dose reduced by the dose reduction unit 206. The image post-processing unit 207 can adjust at least one of the brightness information and the contrast information of at least one of the first radiation image, the second radiation image, and the third radiation image so as to maintain a predetermined brightness based on the predetermined brightness information. Unlike the first irradiation condition calculation unit 203, the image post-processing unit 207 of the radiation imaging apparatus 100 does not determine the irradiation conditions for controlling the radiation irradiation unit 111, and may be a unit that processes the radiation image software-wise.

[0095] The image post-processing unit 207 of the radiation imaging apparatus 100 can adjust the pixel values of the third radiation image so that the brightness information of the third radiation image is similar to the predetermined brightness information. The radiation imaging apparatus 100 can adjust the total pixel values included in the third radiation image using the same ratio or the same difference value, and the brightness information of the third radiation image can be similar to the predetermined brightness information. The predetermined brightness information may be the brightness information stored in the memory.

[0096] However, not limited thereto, the predetermined brightness information may be a value measured by the image brightness information extraction unit 202. For example, the radiation image imaging apparatus 100 can measure the brightness information of at least one of the first radiation image to the second radiation image by using the image brightness information extraction unit 202. The radiation image imaging apparatus 100 can measure the brightness information of the second radiation image. The image post-processing unit 207 of the radiation image imaging apparatus 100 can adjust the pixel values of the third radiation image so that the brightness information of the third radiation image is similar to the brightness information of the second radiation image. The image post-processing unit 207 can adjust at least one of the brightness information and the contrast information of the third radiation image so as to be similar to at least one of the brightness information and the contrast information of the second radiation image. The radiation image imaging apparatus 100 can adjust the overall pixel values included in the third radiation image by using the same ratio or the same difference value, and the brightness information of the third radiation image can be similar to the brightness information of the second radiation image.

[0097] For reference, in the present disclosure, being similar means that the difference between two pieces of information is smaller than or the same as a predetermined range. For example, that the brightness information of the second radiation image is similar to the brightness information of the third radiation image may mean that the absolute value of the difference between the brightness information of the second radiation image and the brightness information of the third radiation image is smaller than or the same as a predetermined range. The predetermined range may be a value greater than or equal to 0.

[0098] Hereinafter, the operation method of the radiation image imaging apparatus will be described in detail.

[0099] FIG. 3 is a flowchart showing an operation method of a radiation image imaging apparatus according to an embodiment of the present disclosure.

[0100] As already described, the radiation imaging apparatus 100 can include a radiation irradiation unit 111 that irradiates a subject with radiation. Further, the radiation imaging apparatus 100 can include an image acquisition unit 112 that receives the radiation irradiated from the radiation irradiation unit 111 and passing through the subject to generate a continuous radiation image.

[0101] The radiation imaging apparatus 100 can include a control unit 200 that controls the radiation irradiation unit and the image acquisition unit 112. The control unit 200 can execute the following operations.

[0102] The control unit 200 can execute a step 310 of acquiring a first radiation image. The image output unit 201 can output the first radiation image. The first radiation image can be included in the continuous radiation images. The first radiation image can include at least one frame image. The first radiation image may be an image obtained by image processing of at least one frame image. The radiation imaging apparatus 100 may store predetermined irradiation conditions. The predetermined irradiation conditions can include at least one of a predetermined tube voltage, a predetermined overcurrent, and an irradiation time of a predetermined X-ray pulse. The radiation imaging apparatus 100 can control the radiation irradiation unit 111 based on the predetermined irradiation conditions to irradiate the subject with radiation. The image acquisition unit 112 can acquire the first radiation image.

[0103] The control unit 200 can execute a step 320 of acquiring brightness information based on the first radiation image included in the continuous radiation images. The brightness information can be acquired by the image brightness information extraction unit 202.

[0104] The control unit 200 can execute a step 330 of determining a first irradiation condition based on the brightness information by a first algorithm. As already described, the first irradiation condition can be determined by the first irradiation condition calculation unit 203.

[0105] Refer to FIG. 4 to explain steps 320 and 330 in more detail.

[0106] FIG. 4 is a flowchart showing an operation method of a radiation imaging apparatus according to an embodiment of the present disclosure.

[0107] The step 320 of acquiring brightness information can include the following steps.

[0108] The control unit 200 can execute step 410 of obtaining brightness information by averaging pixel values included in at least a part of the first radiation image. In order to obtain brightness information by averaging pixel values included in at least a part of the first radiation image, the control unit 200 can execute step 411 of obtaining an area where the subject appears from the first radiation image based on the subject area acquisition model. The control unit 200 can determine an area where the subject appears from the first radiation image based on a predetermined algorithm. The predetermined algorithm may be a machine learning model and a rule-based model. The control unit 200 can determine an area where the subject appears based on the information of the subject and the first radiation image. Here, the information of the subject can include at least one of the thickness of the subject, the type of the subject, the part of the subject, the material of the subject, and the density of the subject. A predetermined algorithm can be selected based on the information of the subject. The control unit 200 can determine an area where the subject appears from the first radiation image based on the selected predetermined algorithm. The area where the subject appears may be a partial area of the first radiation image. The area where the subject appears can mean the inner area of the contour of the subject appearing in the first radiation image.

[0109] The control unit 200 can execute step 412 of obtaining brightness information by averaging the pixel values included in the region where the subject appears. However, it is not limited to this. The control unit 200 can obtain at least one of the minimum value, average value, and median value of the pixel values of the pixels in the region where the subject appears as the brightness information. However, it is not limited to this. The control unit 200 can obtain at least one of the minimum value, average value, and median value of the pixel values of all the pixels of the first radiation image as the brightness information.

[0110] The control unit 200 can execute the following process to execute step 330 of determining the first irradiation condition.

[0111] When the brightness information is smaller than the first critical brightness information determined in advance, the control unit 200 can execute step 420 of determining the first irradiation condition so that the brightness information increases. Also, when the brightness information is larger than the first critical brightness information determined in advance, the control unit 200 can execute step 440 of determining the first irradiation condition so that the brightness information decreases. Also, when the brightness information is the same as the first critical brightness information determined in advance, the control unit 200 can execute step 430 of determining the first irradiation condition with the irradiation condition determined in advance. The irradiation condition determined in advance may be the irradiation condition used to obtain the first radiation image.

[0112] As already described, the first irradiation condition can include at least one of a first tube voltage, a first tube current, and an irradiation time of a first X-ray pulse. The first irradiation condition calculation unit 203 can determine at least one value among the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse of the radiation irradiation unit 111 based on the brightness information of the first radiation image. For example, the larger at least one of the first tube voltage and the first tube current is, the larger the X-ray irradiation dose can be. The irradiation time of the first X-ray pulse is a value proportional to the time during which the X-ray source emits X-rays, and the longer the irradiation time of the first X-ray pulse is, the larger the X-ray irradiation dose can be. At least one of the first tube voltage, the first battery, and the irradiation time of the first X-ray pulse can have a linear relationship with the irradiation dose. However, it is not limited thereto, and at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse can have a non-linear relationship with the irradiation dose.

[0113] The control unit 200 can correct at least one of a predetermined tube voltage, a predetermined tube current, and a predetermined irradiation time of a predetermined X-ray pulse included in a predetermined irradiation condition based on at least one of a predetermined first irradiation condition function and a first irradiation condition table, and determine at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition. The first irradiation condition function or the first irradiation condition table may be a function or a table for determining the first irradiation condition based on the predetermined irradiation condition and the brightness information of the first radiation image.

[0114] According to an embodiment of the present disclosure, as the irradiation dose increases, the brightness information of the first radiation image can become brighter. At this time, when the brightness information is smaller than the predetermined first critical brightness information, the first irradiation condition may be larger than the predetermined irradiation condition. That is, when the brightness information is smaller than the predetermined first critical brightness information, at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition may be larger than at least one of the predetermined tube voltage, the predetermined tube current, and the irradiation time of the predetermined X-ray pulse included in the predetermined irradiation condition. Further, when the brightness information is larger than the predetermined first critical brightness information, the first irradiation condition may be smaller than the predetermined irradiation condition. That is, when the brightness information is larger than the predetermined first critical brightness information, at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition may be smaller than at least one of the predetermined tube voltage, the predetermined tube current, and the irradiation time of the predetermined X-ray pulse included in the predetermined irradiation condition. Further, when the brightness information is the same as the predetermined first critical brightness information, the first irradiation condition may be the same as the predetermined irradiation condition. That is, when the brightness information is the same as the predetermined first critical brightness information, at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition may be the same as at least one of the predetermined tube voltage, the predetermined tube current, and the irradiation time of the predetermined X-ray pulse included in the predetermined irradiation condition.

[0115] However, and not limited thereto, according to various embodiments of the present disclosure, as the irradiation dose increases, the brightness information of the first radiation image may become darker. For example, the control unit 200 can use an inverted image obtained by inverting the pixel values of the image acquired from the image acquisition unit 112. Therefore, as the irradiation dose increases, the brightness information of the first radiation image, which is an inverted image, may become darker. At this time, when the brightness information is smaller than the predetermined first critical brightness information, the first irradiation condition may be smaller than the predetermined irradiation condition. That is, when the brightness information is smaller than the predetermined first critical brightness information, at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition may be smaller than at least one of the predetermined tube voltage, the predetermined tube current, and the predetermined irradiation time of the X-ray pulse included in the predetermined irradiation condition. Further, when the brightness information is larger than the predetermined first critical brightness information, the first irradiation condition may be larger than the predetermined irradiation condition. That is, when the brightness information is larger than the predetermined first critical brightness information, at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition may be larger than at least one of the predetermined tube voltage, the predetermined tube current, and the predetermined irradiation time of the X-ray pulse included in the predetermined irradiation condition.

[0116] As described above, the control unit 200 can determine a first irradiation condition including at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse for the brightness information of the first radiation image to be the same as the predetermined brightness information. The first irradiation condition may be different from the predetermined irradiation condition. However, in a specific case, the first irradiation condition may be the same as the predetermined irradiation condition. The control unit 200 can make the brightness information of the radiation image generated after the first radiation image based on the first irradiation condition the same as the predetermined brightness information.

[0117] The control unit 200 can repeatedly acquire the first irradiation condition at a predetermined cycle. The radiation imaging apparatus 100 can provide a moving image, and the subject can change continuously. The radiation imaging apparatus 100 can continuously acquire the first irradiation condition and thereby provide an optimal radiation image to the user by irradiating radiation.

[0118] Also, referring to FIG. 3, the control unit 200 can execute a step 340 of controlling the dose of radiation based on the first irradiation condition. The step 340 can be executed by the irradiation control unit 204. As already described, the dose of radiation can be determined by at least one of the first tube voltage, the first tube current, and the irradiation time of the first X-ray pulse included in the first irradiation condition.

[0119] The control unit 200 can execute a step 350 of acquiring a second radiation image included in the continuous radiation images and generated based on the first irradiation condition. The second radiation image may be a radiation image generated after the first radiation image. The second radiation image can be included in the continuous radiation images. The second radiation image can include at least one frame image in the moving image. Also, if the first radiation image is an image based on a predetermined irradiation condition, the second radiation image may be an image based on the first irradiation condition. Since the subject appearing in the second radiation image is similar to the predetermined brightness information, the subject can appear clearly in the second radiation image. Therefore, the user can easily diagnose the patient based on the second radiation image. However, the second radiation image may not be based on the minimum dose. The radiation imaging apparatus 100 can further execute the following process to utilize the minimum dose while maintaining the image quality.

[0120] The control unit 200 can execute step 360 of acquiring motion presence / absence information indicating whether the photographed part of the subject is fixed. The motion presence / absence information can be acquired from the user through the input unit 250. For example, after the user confirms that the subject is stationary, the user can input the motion presence / absence information into the radiographic imaging apparatus 100.

[0121] However, it is not limited thereto, and the motion presence / absence information may be automatically acquired. More specifically, step 360 of acquiring the motion presence / absence information can include the following process.

[0122] When the time at which at least one of the first radiographic image and the second radiographic image is acquired is less than a predetermined critical time, the control unit 200 can execute a step of determining the motion presence / absence information so as to indicate that the photographed part of the subject is not fixed. The critical time may be a time sufficient for the patient to be fixed. In a main environment, the subject may be a patient who is the target of surgery. The patient may be under anesthesia for the surgery. When the patient is placed in the radiographic imaging apparatus, the patient hardly moves. Therefore, when the time from the time when the radiographic imaging apparatus 100 starts to acquire at least one of the first radiographic image and the second radiographic image is less than a predetermined critical time, the control unit 200 can determine the motion presence / absence information so as to indicate that the photographed part of the subject is not fixed. Here, the time when acquiring the first radiographic image may mean the time when starting to acquire the first radiographic image for the subject. Also, the time when starting to acquire the second radiographic image may mean the time when starting to acquire the radiographic image under the first irradiation condition. The time when starting to acquire the second radiographic image may be the time when the acquisition of the first radiographic image ends. The difference between the time when starting to acquire the first radiographic image and the time when starting to acquire the second radiographic image may be within 5 seconds.

[0123] When the time at which at least one of the first radiographic image and the second radiographic image is acquired is equal to or longer than a predetermined critical time, the control unit 200 can execute a step of determining the presence / absence of movement information so as to indicate that the imaging region of the subject is fixed. That is, the radiographic imaging apparatus (100) can assume that the subject is fixed after the predetermined critical time.

[0124] When the presence / absence of movement information indicates that the imaging region of the subject is fixed, the control unit 200 can execute step 370 of determining a second irradiation condition based on the second radiographic image by a second algorithm. Step 370 can be executed by the second irradiation condition calculation unit 205.

[0125] The first algorithm for determining the first irradiation condition and the second algorithm for determining the second irradiation condition may be different from each other. Hereinafter, FIG. 5 is referred to in order to explain step 370 of determining the second irradiation condition.

[0126] FIG. 5 is a flowchart showing the operation of the radiographic imaging apparatus according to an embodiment of the present disclosure. FIG. 6 is a diagram for explaining downsampling according to an embodiment of the present disclosure.

[0127] Referring to FIGS. 5 and 6, the step 370 of determining the second irradiation condition can include the following operations. The control unit 200 can execute a step of downsampling the second radiation image 610 in units of patches 611 of a predetermined size to obtain a downsampled image 620. The patch 611 of the predetermined size may be smaller than the second radiation image 610. If the size of the second radiation image 610 is n×m, the size of the patch 611 of the predetermined size may be a×b. n is the number of pixels on the horizontal axis included in the second radiation image 610, and m may be the number of pixels on the vertical axis included in the second radiation image 610. Also, a is the number of pixels on the horizontal axis of the patch 611 of the predetermined size, and b may be the number of pixels on the vertical axis of the patch 611 of the predetermined size. n may be greater than or equal to a, and m may be greater than or equal to b.

[0128] The control unit 200 can determine one of the average, minimum, maximum, and median of the pixel values of the pixels included in the patch 611 of the predetermined size in the second radiation image 610 as the pixel value of one pixel 621 of the downsampled image 620. The control unit 200 can determine one of the average, minimum, maximum, and median of the pixel values of the pixels included in the next patch 612 of the predetermined size in the second radiation image 610 as the pixel value of one pixel 622 of the downsampled image 620. The sizes of the patch 611 of the predetermined size and the next patch 612 of the predetermined size may be the same or may not overlap with each other. The control unit 200 can repeat the above process for the entire second radiation image 610 to obtain a downsampled image 620.

[0129] Above, the patches 611 and 612 of a predetermined size did not overlap with each other, but it is not limited thereto. The patches of a predetermined size may overlap with each other. For example, the control unit 200 can determine one of the average, minimum, maximum, and median of the pixel values of the pixels included in the patch 631 of a predetermined size from the second radiation image 630 as the pixel value of one pixel 641 of the downsampled image 640. The control unit 200 can determine one of the average, minimum, maximum, and median of the pixel values of the pixels included in the next patch 632 of a predetermined size from the second radiation image 630 as the pixel value of one pixel 642 of the downsampled image 640. The sizes of the patch 631 of a predetermined size and the next patch 632 of a predetermined size may be the same or may overlap with each other. The control unit 200 can repeat the above process for the entire second radiation image 630 to obtain the downsampled image 640. When the patches of a predetermined size are downsampled overlappingly, the downsampled image 640 may be larger than the downsampled image 620.

[0130] Above, downsampling was performed on the entire area of the second radiation image 630, but it is not limited thereto. The control unit 200 can execute downsampling on the region of interest in the second radiation image to obtain a downsampled image. The region of interest may be a region selected by the user or a region automatically selected by the radiation image capturing device 100. For example, the region of interest may be a region where the subject appears. Since the region where the subject appears has already been described, overlapping descriptions are omitted.

[0131] The control unit 200 can execute a step of obtaining the minimum pixel value among the pixel values included in the downsampled image (one of 620 and 640). When the minimum pixel value is greater than the predetermined second critical brightness information, the control unit 200 can execute a step of determining the second irradiation condition so that the minimum pixel value becomes the same as the second critical brightness information. When the minimum pixel value is less than or equal to the predetermined second critical brightness information, the control unit 200 can execute a step of determining the second irradiation condition to be the same as the first irradiation condition. When the minimum pixel value is less than or equal to the predetermined second critical brightness information, the control unit 200 can also not determine the second irradiation condition. The second critical brightness information can be obtained based on the performance of the detector. The second critical brightness information is the smallest pixel value that can be processed without problems by at least one of the image acquisition unit 112 and the image post-processing unit 207 included in the control unit 200, and may be a constant defined in advance. When the performance of the image acquisition unit 112 and the image post-processing unit 207 is not good, there may be noise components in the pixels, and values below a specific pixel value may be due to noise rather than radiation. Therefore, the second critical brightness information may be a value related to the minimum radiation dose that can indicate that the pixel has been excited by radiation. That is, the better the performance of the image acquisition unit 112 and the image post-processing unit 207, the smaller the second critical brightness information can be.

[0132] Refer to FIG. 7 to explain the step of determining the second irradiation condition so that the minimum pixel value becomes the same as the second critical brightness information.

[0133] FIG. 7 is a flowchart for explaining the process for obtaining the second irradiation condition according to an embodiment of the present disclosure.

[0134] The step of determining the second irradiation condition so that the minimum pixel value becomes the same as the second critical brightness information can include the following process.

[0135] The control unit 200 can execute step 710 of determining a reduction ratio based on the minimum pixel value and the second critical brightness information. The second critical brightness information is the smallest pixel value that can be processed without problems in at least one of the image acquisition unit 112 and the image post-processing unit 207 included in the control unit 200, and may be a constant defined in advance. The reduction ratio may be greater than or equal to 0 and less than or equal to a predefined maximum reduction ratio. The maximum reduction ratio may be 65% or more and 75% or less. For example, the maximum reduction ratio may be 70%. The unit of the reduction ratio may be %. However, it is not limited thereto.

[0136] The control unit 200 can obtain the reduction ratio based on the following formula.

[0137] Reduction ratio = min(max(1 - second critical brightness information / minimum pixel value, 0), maximum reduction ratio) * 100

[0138] The dose of radiation based on the second irradiation condition may be greater than or equal to 30% of the dose of radiation based on the first irradiation condition. When the reduction dose is determined to be 70% which is the maximum reduction ratio, the dose of radiation based on the second irradiation condition may be 30% of the radiation based on the first irradiation condition.

[0139] The control unit 200 can execute step 720 of determining the second irradiation condition so that the dose irradiated from the radiation irradiation unit is the dose obtained by subtracting the value obtained by multiplying the dose by the first irradiation condition by the reduction ratio from the dose by the first irradiation condition.

[0140] The second irradiation condition can include at least one of a second tube voltage, a second tube current, and an irradiation time of a second X-ray pulse. The control unit 200 can determine at least one value among the second tube voltage, the second tube current, and the irradiation time of the second X-ray pulse based on the reduction ratio determined in step 710. For example, the greater at least one of the second tube voltage and the second tube current is, the greater the X-ray irradiation dose can be. The irradiation time of the second X-ray pulse is a value proportional to the time during which the X-ray source emits X-rays, and the longer the irradiation time of the second X-ray pulse is, the greater the X-ray irradiation dose can be. Also, the brighter the radiation image brightness information can be as the irradiation dose increases. However, it is not limited thereto, and the brighter the radiation image brightness information can be as the irradiation dose increases. The control unit 200 can determine a second irradiation condition including at least one of the second tube voltage, the second tube current, and the irradiation time of the second X-ray pulse according to the reduction ratio. The second irradiation condition may be different from the first irradiation condition. However, in a specific case, the second irradiation condition may be the same as the first irradiation condition.

[0141] At least one of the second tube current and the irradiation time of the second X-ray pulse can have a linear relationship with the irradiation dose. Also, the second tube voltage can have a non-linear relationship with the irradiation dose. The control unit 200 can determine at least one of the second tube current and the irradiation time of the second X-ray pulse by reducing at least one of the first tube current and the irradiation time of the first X-ray pulse by the reduction ratio. However, it is not limited thereto, and the control unit 200 can apply at least one of the first tube current and the irradiation time of the first X-ray pulse to a predetermined reduction ratio determination function or a reduction ratio determination table to determine at least one of the second tube current and the irradiation time of the second X-ray pulse corresponding to the reduction ratio. Also, the control unit 200 can obtain a voltage reduction ratio corresponding to the reduction ratio based on a voltage reduction ratio determination function or a voltage reduction ratio determination table. The control unit 200 can determine the second tube voltage by reducing the first tube voltage by the voltage reduction ratio.

[0142] Referring further to FIG. 3, the control unit 200 can execute a step 380 of controlling the dose of radiation based on the second irradiation condition. The step 380 can be executed by at least one of the dose reduction unit 206 and the irradiation control unit 204. As already described, the second irradiation condition can be determined based on the first irradiation condition and the reduction ratio. The dose of radiation based on the second irradiation condition may be smaller than or the same as the dose of radiation based on the first irradiation condition. That is, the control unit 200 can determine the dose according to the second irradiation condition by the following formula according to the second irradiation condition.

[0143] Dose according to the second irradiation condition = Dose according to the first irradiation condition * (1 - reduction ratio / 100)

[0144] The control unit 200 can execute a step 390 of obtaining a third radiation image included in the continuous radiation images and generated based on the second irradiation condition. The third radiation image may be a radiation image generated after the second radiation image. The third radiation image may be included in the continuous radiation images. The third radiation image can include at least one frame image in the video.

[0145] Also, if the second radiation image is an image based on the first irradiation condition, the third radiation image may be an image based on the second irradiation condition. In the third radiation image, almost the same quality as the second radiation image can be maintained. That is, the sharpness and noise of the subject appearing in the third radiation image may be almost the same as the sharpness and noise of the subject appearing in the second radiation image. However, the dose of radiation irradiated to the subject to obtain the third radiation image may be smaller than or the same as the dose of radiation irradiated to the subject to obtain the second radiation image.

[0146] The control unit 200 can repeatedly acquire the second irradiation condition at a predetermined period. The radiation imaging apparatus 100 can provide a moving image, and the subject can change continuously. The radiation imaging apparatus 100 can continuously acquire the second irradiation condition, and thereby, by irradiating radiation, can acquire a radiation image of the subject with a low dose and can maintain high quality of the radiation image.

[0147] According to the radiation imaging apparatus 100 according to an embodiment of the present disclosure, the control unit 200 can fix the second irradiation condition based on a user input or a predetermined condition. When the control unit 200 fixes the second irradiation condition, an effect of maintaining a low dose can be expected because the second irradiation condition is not changed when an object other than the subject enters the imaging area additionally. For example, when a medical device or the like enters the imaging area, the radiation imaging apparatus 100 can maintain a low dose according to the second irradiation condition without changing the radiation dose for changing the brightness of the radiation image.

[0148] The third radiation image can be post-processed to improve the quality of the image. Hereinafter, a process in which the third radiation image is post-processed will be described.

[0149] FIG. 8 is a diagram for explaining the operation of the radiation imaging apparatus according to an embodiment of the present disclosure.

[0150] The stage 390 of acquiring the third radiation image can include the following process. The control unit 200 can execute a stage of generating an improved current frame image 840 by cumulatively averaging pixel values included in at least a part of the current frame image 830 included in the third radiation image and pixel values included in at least a part of the previous frame image 820 included in the third radiation image. The stage of acquiring the improved current frame image 840 can be executed by the image post-processing unit 207 included in the control unit 200.

[0151] As already described, the third radiographic image can include the current frame image 830 and the previous frame image 820. The current frame image may be the frame most recently acquired through the image acquisition unit 112. The previous frame image 820 may be at least one frame image acquired before the current frame image. The previous frame image 820 can include the immediately previous frame image 822 and the n-2 frame image 821. The immediately previous frame image may be the frame image immediately before the current frame image.

[0152] The control unit 200 can generate an improved current frame image 840 by accumulating and averaging the current frame image 830 and a predetermined number of previous frame images 820. The predetermined number may be greater than or equal to 1. The predetermined number may mean the number of frames. Hereinafter, for the sake of convenience of explanation, the case where the predetermined number is 1 will be described. The same explanation can be applied to the case where the predetermined number is 2 or more.

[0153] The control unit 200 can cumulatively average the pixel value of one pixel in the current frame image 830 and the pixel value of the previous frame image 820 at the position corresponding to one pixel in the current frame image. The radiation imaging apparatus 100 can obtain the pixel values included in the improved current frame image 840 by cumulatively averaging the pixel values of the pixels at the positions corresponding to each other in the current frame image 830 and the previous frame image 820. The pixels at the positions corresponding to each other mean that the pixel positions (coordinate values) in the current frame image 830 and the pixel positions (coordinate values) in the previous frame image 820 are the same. The control unit 200 can obtain the cumulative average value of the entire pixels included in the current frame image 830 and the entire pixels included in the previous frame image 820 to generate the improved current frame image 840. However, not limited thereto, the control unit 200 can obtain the cumulative average value of the pixel values of at least some of the pixels included in at least a part of the current frame image 830 and the pixel values of at least some of the pixels included in at least a part of the previous frame image 820 to generate the improved current frame image 840. At least a part of the current frame image 830 may be at least one of the region of interest or the region where the subject appears.

[0154] As already described, since the subject does not move, the change in the pixel values of the pixels at the same position in the consecutive frame images is small. Therefore, when obtaining the improved current frame image by cumulative averaging as above, the influence of noise can be minimized. The reason is that noise occurs while the pixel values of the pixels change greatly.

[0155] FIG. 9 is a flowchart showing the operation of the radiation imaging apparatus according to an embodiment of the present disclosure. FIG. 10 is a diagram for explaining the operation of the radiation imaging apparatus according to an embodiment of the present disclosure. FIG. 11 is a diagram for explaining the operation of the radiation imaging apparatus according to an embodiment of the present disclosure. FIG. 12 is a diagram for explaining the operation of the radiation imaging apparatus according to an embodiment of the present disclosure.

[0156] FIGS. 9 to 12 can be executed by the image post-processing unit 207 included in the control unit 200. The image post-processing unit 207 does not control the radiation irradiation unit 111, but can correct the first to third radiation images acquired using software and output a radiation image with improved high quality.

[0157] When executing the step 390 of acquiring the third radiation image, the image post-processing unit 207 included in the control unit 200 can further execute the following process.

[0158] Referring to FIG. 9, the control unit 200 can execute a step 910 of generating a motion perception image including motion perception information for each pixel of a difference image obtained by the difference between the current frame image included in the third radiation image and the previous frame image included in the third radiation image.

[0159] More specifically, referring to FIGS. 9 and 10, the control unit 200 can generate a motion perception image through threshold processing of the difference image. Thereby, as shown in FIG. 10, a motion perception image 1010 can be generated from the noise-processed current frame image 830 and the previous frame image 820. Here, the motion perception image 1010 can be obtained based on a subtraction image obtained by subtracting the previous frame image 820 from the current frame image 830.

[0160] The control unit 200 generates a difference image by differentiating the current frame image 830 and the previous frame image 820 that have undergone noise processing, that is, noise reduction and noise stabilization processing. For noise reduction, the control unit 200 can add the absolute values of the differences between the pixel values of any two of the upper left, upper, upper right, left, right, lower left, lower, and lower right pixels adjacent to the central pixel to be noise-reduced and the central pixel to obtain the sum of the absolute values of the differences. The selected adjacent pixels can be appropriately determined according to requirements and conditions. For example, the sum of the absolute values of the differences between the central pixel and two of the upper left, upper, upper right, left, right, lower left, lower, and lower right pixels is calculated respectively.

[0161] For example, the control unit 200 can obtain the sum (A1) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the upper pixel, the sum (A2) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the upper right pixel, the sum (A3) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the left pixel, the sum (A4) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the right pixel, the sum (A5) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the lower left pixel, the sum (A6) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the lower pixel, the sum (A7) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper left pixel and the difference between the pixel value of the central pixel and the pixel value of the lower right pixel. The control unit 200 can obtain the sum (A8) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper pixel and the difference between the pixel value of the central pixel and the pixel value of the upper right pixel. The control unit 200 can obtain the sum (A9) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper cell and the difference between the pixel value of the central pixel and the pixel value of the left pixel, the sum (A10) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper pixel and the difference between the pixel value of the central pixel and the pixel value of the right pixel, the sum (A11) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper pixel and the difference between the pixel value of the central pixel and the pixel value of the lower left pixel, the sum (A12) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper pixel and the difference between the pixel value of the central pixel and the pixel value of the lower pixel, the sum (A13) of the absolute values of the difference between the pixel value of the central pixel and the pixel value of the upper pixel and the difference between the pixel value of the central pixel and the pixel value of the lower right pixel. The control unit 200 can determine the sum of the absolute values of the differences between the central pixel and the surrounding pixels through the above process.That is, the control unit 200 can obtain the sum of absolute values (A1 to A29) through the above process. At this time, it can be determined that the pixel having the direction most similar to the central pixel is in the direction where the sum of absolute values (Ak) is smaller. For example, when A1 is the smallest among A1 to A29, the upper left pixel and the upper pixel can be selected, and the direction of proceeding to the upper left pixel, the central pixel, and the upper pixel in order can be selected.

[0162] Since impulse noise is a pixel having an absolute value particularly larger than that of surrounding pixels, in order to eliminate this, the control unit 200 uses the pixel values of two adjacent pixels with the smallest sum of absolute values of the differences between the pixel values of the two selected adjacent pixels and the central pixel to correct the pixel value of the central pixel and update it to a pixel value with reduced noise. For example, the control unit 200 can substitute the pixel value of the central pixel with the average value or the median value of the pixel value of the central pixel and the pixel values of the two selected pixels. By sequentially performing the update of the pixel value in such a manner while moving the mask, noise reduction can be achieved through the update of the pixel value.

[0163] In the above, an embodiment of considering the pixels around the central pixel within one frame has been described, but it is not limited thereto. The control unit 200 may further use at least one of the frame immediately before and the frame immediately after the current frame. The frame immediately after may be a frame obtained immediately after the current frame as the image obtained from the image acquisition unit 112. The current frame may be a frame during noise processing, and the frame immediately after may be a frame before noise processing. The frame immediately before may be a frame in which noise processing has been completed as the frame immediately before the current frame.

[0164] The control unit 200 can obtain the absolute value of the difference between the pixel value of the central pixel of the current frame and the central pixel of the previous frame at the same position, and at least any one of the adjacent upper left, upper, upper right, left, right, lower left, lower, and lower right pixels of the current frame. Further, the control unit 200 can also obtain the absolute value of the difference between the pixel value of the central pixel of the current frame and the central pixel of the subsequent frame at the same position, and at least any one of the adjacent upper left, upper, upper right, left, right, lower left, lower, and lower right pixels of the current frame. The control unit 200 can select two pixels with the smallest sum of the two absolute values. The control unit 200 can replace the pixel value of the central pixel of the current frame with the average value or the median value of the pixel values of the central pixel of the current frame and the two selected pixels.

[0165] The control unit 200 can reduce the deviation of the noise between the current frame image with reduced noise and the previous frame image to stabilize the noise. For example, since the amount of photons incident on each sensor for acquiring a radiation image appears randomly and independently over time and is not constant, the noise characteristics of the radiation image generally follow a Poisson distribution. In an embodiment of the present disclosure, in order to remove noise having Poisson distribution characteristics, it is approximated to noise having Gaussian distribution characteristics through an Anscombe transform. Since the Anscombe transform approximates to a Gaussian distribution close to a standard deviation of 1, the transformed data comes to have a stable noise deviation.

[0166] The control unit 200 can calculate the difference in pixel values of each pixel at the same position for all pixels between the current frame image 830 and the previous frame image 820 to generate a difference image. The difference image can include the motion information of the subject and the remaining noise information. Additionally, an average value filter or a median value filter, etc. may be used on the generated difference image to stabilize the difference image.

[0167] The control unit 200 can determine a critical pixel value for motion detection of the difference image, and by performing threshold processing based on the determined critical pixel value, sense the presence or absence of motion of each pixel, thereby generating a motion detection image 1010. If the critical pixel value for motion detection is set too low, the motion detection sensitivity increases and the noise reduction level decreases. Conversely, if the critical pixel value is set too high, the motion detection sensitivity decreases and motion blur (blurring phenomenon) may occur. Since X-ray images are acquired under different dose conditions and subject characteristics, it is difficult to predict the pixel values of the acquired images, and it is necessary to set an appropriate critical pixel value according to the pixel values.

[0168] The control unit 200 according to an embodiment of the present disclosure can apply an adaptive critical pixel value whose size changes according to the size of the pixel value of each pixel of the difference image. For example, the critical pixel value for motion determination can be set to decrease as the pixel value of the pixel increases.

[0169] When the absolute value of the pixel value of a pixel included in the difference image is greater than or equal to a predetermined critical pixel value, the pixel value of the corresponding pixel included in the motion detection image 1010 can be "0". For example, when the absolute value of the pixel value of a pixel included in the difference image is less than the predetermined critical pixel value, the pixel value of the corresponding pixel included in the motion detection image 1010 can be "1". However, it is not limited thereto. When the absolute value of the pixel value of a pixel included in the difference image is greater than or equal to a predetermined critical pixel value, the pixel value of the corresponding pixel included in the motion detection image 1010 can be "1". For example, when the absolute value of the pixel value of a pixel included in the difference image is less than the predetermined critical pixel value, the pixel value of the corresponding pixel included in the motion detection image 1010 can be "0".

[0170] The motion detection image 1010 can include information regarding the presence or absence of motion for each pixel. For example, pixels with motion can be set to have a value of "0", and pixels without motion can be set to have a value of "1". That is, all pixels of the motion detection image 1010 have pixel values of 0 or 1. A pixel with a value of 0 means there is motion based on the previous frame image, and a pixel with a value of 1 can mean there is no motion based on the previous frame image. However, it is not limited to this.

[0171] The control unit 200 can generate an improved current frame image 840 based on the motion detection image 1010. As described with reference to FIG. 8, the control unit 200 can execute a step of generating an improved current frame image 840 by cumulatively averaging the pixel values included in at least a part of the current frame image 830 included in the third radiation image and the pixel values included in at least a part of the previous frame image 820 included in the third radiation image. At this time, the control unit 200 can further utilize the motion detection image 1010. More specifically, for pixels where motion is detected in the motion detection image 1010, the control unit 200 determines the pixel value of the current frame image 830 as the pixel value of the improved current frame image 840, and for pixels where no motion is detected, the control unit 200 can determine the pixel value of the improved current frame image 840 by cumulatively averaging the pixel value of the current frame image 830 and the pixel value of the previous frame image 820. However, it is not limited to this, and the control unit 200 may utilize a motion probability image instead of the motion detection image 1010 to generate the improved current frame image 840.

[0172] Also, referring to FIG. 9, the control unit 200 can execute a step 920 of generating a motion probability image based on the generated motion detection image and the motion detection image accumulated up to the previous frame.

[0173] Referring to FIGS. 9 and 10, the control unit 200 can generate a motion probability image 1020 by accumulating it in a separate memory in chronological order based on the motion detection result. The motion probability image 1020 can be used to determine an appropriate mixing ratio of the previous frame image 820 and the current frame image 830 for generating an improved current frame image 840. As already described, the previous frame image 820 can include at least one frame. The current frame image 830 can include one frame.

[0174] In order to execute the stage 920 of generating a motion probability image, the control unit 200 can execute the following process. The control unit 200 can execute a stage of generating the motion probability image 1020 by adding one or more of the motion detection images of the current frame and the motion detection images up to the previous frame.

[0175] More specifically, FIG. 11 is a diagram showing a method of generating a motion probability image 1020 using the motion detection image 1010. The control unit 200 can generate and update the motion probability image 1020 by storing the motion detection image 1010 obtained through motion detection in a separate independent memory in a cumulative manner frame by frame in chronological order. The left image in FIG. 11 shows the accumulated motion detection image 1110, and the right side shows the motion probability image 1120 obtained by adding the motion detection images. The values of the same pixels of the motion probability image of the previous frame and the motion detection image 1010 of the current frame can be added together to generate the motion probability image 1120 of the current frame. That is, the motion probability image 1120 of a specific frame is an image obtained by adding the pixel values of the same pixels of all the motion detection images obtained up to the corresponding frame. For example, referring to FIG. 11, when the current frame is the fourth frame, the sum of the values of the same pixels in the motion detection images obtained from the four frames up to now is the value of the same pixel in the motion probability image of the current frame.

[0176] When the value of the pixel determined to have movement in the motion detection image is set to "0" and expressed brightly, and the value of the pixel determined to have no movement is set to "1" and expressed darkly, each pixel of the motion probability image comes to have a value corresponding to the sum of the motion detection values (0 or 1) of the corresponding pixel, and comes to have other values, that is, other brightness levels, depending on the number of motion determination times. For example, assuming a motion probability image consisting of 10 frames, the corresponding motion probability image is obtained by summing 10 motion detection images, and each pixel of the motion probability image comes to have one of the values between 0 and 10. Here, when the values of the same pixel in all the motion detection images are all 0, the corresponding pixel of the motion probability image has a value of 0, and when the values of the same pixel in all the motion detection images are all 1, the corresponding pixel of the motion probability image has a value of 10. Thereby, as shown in FIG. 10, each pixel of the motion probability image has a pixel value, that is, brightness, according to the number of motion detection times of the same pixel in the motion detection images up to the corresponding frame.

[0177] In this sense, it can be determined that the higher the pixel value in the generated motion probability image 1020, the higher the motion probability, and the lower the pixel value, the lower the motion probability. For example, when motion is detected while the frames are advanced in time order at the same pixel position, the motion probability becomes high, and when no motion is detected, the motion probability becomes low.

[0178] The value of each pixel of the motion probability image 1020 indicates the degree of motion and the motion probability value of the corresponding pixel. That is, when a determination value of "0" is assigned when there is motion and "1" when there is no motion, it means that the smaller the pixel value of the motion probability image 1020, the higher the motion probability of the corresponding pixel.

[0179] FIG. 12 illustrates an example of the generation process of the motion detection image 1010 and the motion probability image 1020 based on the input image as the frames progress. The motion detection image can be generated by the difference between the frame image of each frame and the previous frame image, and further, the motion probability image 1020 can be generated by summing the motion detection image and the motion detection image of the previous frame.

[0180] Referring to FIG. 9, the control unit 200 can execute step 930 of generating an improved current frame image by mixing the current frame image and the previous frame image based on the motion probability image.

[0181] In order to execute step 930 of generating the improved current frame image, the control unit 200 can execute a step of variably determining the mixing ratio of the current frame image 830 and the previous frame image 820 according to the value indicating the degree of motion of each pixel of the motion probability image 1020. Also, the control unit 200 can determine the mixing ratio such that the larger the degree of motion indicated by the value of each pixel of the motion probability image 1020, the larger the reflection ratio of the current frame image compared to the previous frame image.

[0182] Here, the current frame image 830 may be a current frame image in a state where noise has been reduced by the control unit 200, and the previous frame image 820 may be a previous frame image in a state where noise has been reduced by the control unit 200. Also, the previous frame image 820 may be a frame image improved in the past or a frame image not improved. At this time, the control unit 200 can generate an improved current frame image 840 by mixing the current frame image 830 and the previous frame image 820 at an appropriate mixing ratio based on the motion probability image 1020. That is, the control unit 200 can perform a weighted average of the current frame image 830 and the previous frame image 820 based on the motion probability image 1020.

[0183] The reflection ratio of the current frame image 830 can be set to be relatively larger as the degree of motion indicated by the value of each pixel of the motion probability image 1020 is larger. That is, the mixing ratio can be determined such that the higher the motion probability determined by the pixel value included in the motion probability image 1020, the higher the weighted value of the current frame image 830. For example, the reflection ratio can be determined such that the reflection ratio of the current frame image 830 increases linearly as the degree of motion indicated by the pixel value of the motion probability image 1020 in pixel units is larger.

[0184] As a specific example, for pixels with a large amount of movement, a predetermined weighting value (α1), for example, 0.8, is assigned to the corresponding pixel in the current frame image 830, and a weighting value (1-α1), for example, 0.2, is assigned to the corresponding pixel in the previous frame image 820, and such a mixing process can be executed for all pixels.

[0185] On the other hand, for pixels with little movement, a predetermined weighting value (α2), for example, 0.2, is assigned to the corresponding pixel in the current frame image 830, and a weighting value (1-α2), for example, 0.8, is assigned to the corresponding pixel in the previous frame image 820, so that the current frame image 830 and the previous frame image 820 can be mixed. When the weighting value of the current frame image 830 is high for pixels with a large amount of movement, an image without motion blur can be obtained. As a result, the improved current frame image 840 updates pixels with a large amount of movement based on the motion probability by reflecting more of the value of the current frame, and updates pixels with little movement by reflecting more of the value of the previous frame, so that the noise reduction performance can be improved while the frames are accumulated over time.

[0186] So far, various embodiments have been described. Those having ordinary knowledge in the technical field to which the present disclosure pertains should understand that the present disclosure can be embodied in a modified form without departing from the essential characteristics of the present disclosure. Therefore, the disclosed embodiments should be considered from an illustrative rather than a limiting perspective. The scope of the present disclosure appears in the claims rather than the above description, and all differences within the scope equivalent thereto should be construed as being included in the present disclosure.

[0187] On the one hand, the above-described embodiments of the present disclosure can be created by a computer-executable program and can be embodied in a general-purpose digital computer that operates the program using a computer-readable recording medium. The computer-readable recording medium includes storage media such as magnetic storage media (e.g., ROM, floppy disk, hard disk, etc.) and optical reading media (e.g., CD-ROM, DVD, etc.).

Claims

1. In a radiation imaging apparatus, an image output unit that outputs a first radiation image included in continuous radiation images acquired by irradiating a subject with radiation; an image brightness information extraction unit that acquires brightness information from the first radiation image; a first irradiation condition calculation unit that determines a first irradiation condition based on the brightness information; an irradiation control unit that controls the dose of radiation based on the first irradiation condition; when the imaging part of the subject is fixed, a second irradiation condition calculation unit that determines a second irradiation condition based on a second radiation image generated based on the first irradiation condition; a dose reduction unit that reduces or maintains the dose of radiation based on the second irradiation condition, characterized in that the radiation imaging apparatus includes the dose reduction unit.

2. The value obtained by subtracting the radiation dose based on the second irradiation condition from the radiation dose based on the first irradiation condition is less than or equal to 70% of the dose based on the first irradiation condition, according to the radiation imaging apparatus described in Claim 1.

3. The radiation imaging apparatus described in Claim 1, characterized in that when the dose is reduced by the dose reduction unit, it includes deactivating the first irradiation condition calculation unit.

4. The radiation imaging apparatus described in Claim 1, characterized in that it includes generating an improved current frame image by cumulatively averaging the pixel values included in the current frame image included in the third radiation image output by the dose reduced by the dose reduction unit and the pixel values included in the previous frame image included in the third radiation image.

5. The radiation imaging apparatus further includes an image post-processing unit that post-processes the third radiation image output by the dose reduced by the dose reduction unit, wherein the image post-processing unit adjusts at least one of the brightness information and contrast information of the third radiation image so as to be similar to at least one of the brightness information and contrast information of the second radiation image, according to the radiation imaging apparatus described in Claim 1.

6. In an operating method of a radiation imaging apparatus including a radiation irradiation unit that irradiates a subject with radiation, an image acquisition unit that receives the radiation irradiated from the radiation irradiation unit and passing through the subject to generate continuous radiation images, and a control unit that controls the radiation irradiation unit and the image acquisition unit, a step in which the control unit acquires brightness information based on a first radiation image included in the continuous radiation images; Determining a first irradiation condition based on the brightness information by the first algorithm; Controlling the dose of radiation based on the first irradiation condition; Obtaining a second radiation image included in the continuous radiation images and generated based on the first irradiation condition; Obtaining movement presence information indicating whether the imaging site of the subject is fixed; When the movement presence information indicates that the imaging site of the subject is fixed, determining a second irradiation condition based on the second radiation image by the second algorithm; Controlling the dose of radiation based on the second irradiation condition; Obtaining a third radiation image included in the continuous radiation images and generated based on the second irradiation condition, wherein the method for operating a radiation image capturing apparatus is characterized by including these steps.

7. The method for operating a radiation image capturing apparatus according to claim 6, wherein the dose of radiation based on the second irradiation condition is greater than or equal to 30% of the dose of radiation based on the first irradiation condition.

8. The method for operating a radiation image capturing apparatus according to claim 6, wherein the first algorithm for determining the first irradiation condition and the second algorithm for determining the second irradiation condition are different from each other.

9. The step of obtaining the third radiation image includes generating an improved current frame image by cumulatively averaging pixel values included in at least a part of the current frame image included in the third radiation image and pixel values included in at least a part of the previous frame image included in the third radiation image, wherein the method for operating a radiation image capturing apparatus according to claim 6 is characterized by including this step.

10. The step of obtaining the third radiation image includes: Generating a motion perception image including motion perception information for each pixel of a difference image obtained by the difference between the current frame image included in the third radiation image and the previous frame image included in the third radiation image; Generating a motion probability image based on the generated motion perception image and the motion perception image accumulated up to the previous frame; Generating an improved current frame image by mixing the current frame image and the previous frame image based on the motion probability image, wherein the method for operating a radiation image capturing apparatus according to claim 6 is characterized by including these steps.

11. The step of generating the motion probability image includes the step of generating the motion probability image by adding together one or more of the motion detection images of the current frame and the motion detection images up to the previous frame. The step of generating the improved current frame image includes the step of variably determining a mixing ratio between the current frame image and the previous frame image based on a value indicating the degree of motion of each pixel of the motion probability image. The operation method of the radiation image capturing apparatus according to claim 10, wherein the mixing ratio is determined such that the larger the degree of motion indicated by the value of each pixel of the motion probability image, the larger the reflection ratio of the current frame image compared to the previous frame image.

12. The step of obtaining the brightness information includes the step of obtaining the brightness information by averaging pixel values included in at least a part of the first radiation image. The step of determining the first irradiation condition is when the brightness information is smaller than predetermined first critical brightness information, determining the first irradiation condition so that the brightness information increases; and when the brightness information is larger than predetermined first critical brightness information, determining the first irradiation condition so that the brightness information decreases, the operation method of the radiation image capturing apparatus according to claim 6.

13. The step of obtaining the brightness information by averaging pixel values included in at least a part of the first radiation image is obtaining a region where the subject appears from the first radiation image based on a subject region acquisition model; and obtaining the brightness information by averaging pixel values included in the region where the subject appears, the operation method of the radiation image capturing apparatus according to claim 12.

14. The step of determining the second irradiation condition is downsampling the second radiation image in units of patches of a predetermined size to obtain a downsampled image; obtaining a minimum pixel value among pixel values included in the downsampled image; and when the minimum pixel value is larger than predetermined second critical brightness information, determining the second irradiation condition so that the minimum pixel value becomes the same as the second critical brightness information, the operation method of the radiation image capturing apparatus according to claim 6.

15. The step of determining the second irradiation condition such that the minimum pixel value is the same as the second critical brightness information includes: determining a reduction ratio based on the minimum pixel value and the second critical brightness information; determining the second irradiation condition such that the dose obtained by subtracting the value obtained by multiplying the dose under the first irradiation condition by the reduction ratio from the dose under the first irradiation condition is irradiated from the radiation irradiation unit; The reduction ratio is greater than 0 and less than a predetermined maximum reduction ratio. The method for operating a radiation image capturing apparatus according to claim 14. **Claim 16** The step of obtaining movement presence / absence information includes: when the time at which at least one of the first radiation image and the second radiation image is obtained is less than a predetermined critical time, determining the movement presence / absence information to indicate that the imaging site of the subject was not fixed; when the time at which at least one of the first radiation image and the second radiation image is obtained is equal to or greater than a predetermined critical time, determining the movement presence / absence information to indicate that the imaging site of the subject was fixed. The method for operating a radiation image capturing apparatus according to claim 6.

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