Image processing apparatus, radiation imaging system, and program

Abstract

To provide a technique for improving the image quality of a radiological image that is obtained from a radiation imaging apparatus in which imaging pixels having different properties due to structural differences are mixed.SOLUTION: An image processing apparatus is configured to: obtain a radiological image that includes a plurality of pixel values obtained from a plurality of imaging pixels through radiation imaging using a radiation imaging apparatus in which the plurality of imaging pixels are two-dimensionally arranged; determine a first pixel value obtained from an imaging pixel of a first type among the plurality of pixel values, and a pixel value obtained from an imaging pixel of a second type which has a different configuration from the imaging pixel of the first type; perform first correction processing on the pixel value obtained from the imaging pixel of the first type; and perform second correction processing which is different from the first correction processing on the pixel value obtained from the imaging pixel of the second type. Here, in the second correction processing, the correction processing to be applied to a pixel value to be corrected is determined on the basis of pixel value information based on some of the pixel values in the radiological image.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an image processing device and method, a radiation imaging system, and a program. [Background technology]

[0002] Radiation imaging devices (also known as flat panel detectors, or FPDs) are widely used, each having a pixel array provided with conversion elements that convert radiation into electric charges and switching elements such as thin-film transistors, a driving circuit, and a readout circuit. In recent years, efforts have been made to increase the number of functions of this type of radiation imaging device, including incorporating a function for obtaining radiation irradiation information while radiation is being emitted from a radiation source. The irradiation information is used, for example, to detect the timing at which radiation emitted from the radiation source begins to be incident and to detect the accumulated radiation exposure dose. The accumulated exposure dose can be used, for example, for an automatic exposure control (AEC) function of the radiation imaging device. In the AEC function, the radiation imaging device monitors the accumulated exposure dose and automatically terminates radiation irradiation from the radiation source by controlling the radiation source when the accumulated exposure dose reaches an appropriate level.

[0003] Patent Document 1 describes an FPD equipped with composite pixels composed of main pixels and sub-pixels that can read out electric charges to separate signal lines. According to the FPD of Patent Document 1, image signals for constructing a radiographic image are acquired from the main pixels, and signals representing irradiation information are acquired from the sub-pixels. The FPD is equipped with an AEC function that controls the radiation source to terminate irradiation in accordance with the result of comparing the integrated irradiation dose obtained based on the irradiation information with a preset threshold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-135389 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the FPD of Patent Document 1, composite pixels consisting of main pixels and sub-pixels have different output characteristics from normal pixels other than the composite pixels, which can cause image quality degradation in radiographic images. Patent Document 1 attempts to correct the image signal obtained from the composite pixels (main pixels) to reduce or prevent such image quality degradation. Specifically, the correction is performed by multiplying the image signal of the main pixel by the ratio of the total aperture area of ​​one pixel to the aperture area of ​​the main pixel (hereinafter referred to as the aperture ratio), or the ratio of the total output of the composite pixel to the output of the main pixel in response to radiation irradiated under certain conditions. The total output of the composite pixel is the sum of the outputs of the main pixel and the sub-pixel.

[0006] In Patent Document 1, a correction coefficient is determined based on the aperture ratio determined by the element structure of the composite pixel or the ratio of outputs obtained from the composite pixel under specific irradiation conditions. However, according to the inventor's research, the output difference between the output from a normal imaging pixel and the output from a composite pixel (main pixel) whose characteristics differ from those of the normal imaging pixel due to the influence of sub-pixels, etc., changes depending on the imaging environment and irradiation conditions. It has been found that this change in output difference has a significant impact on the image quality of the acquired radiographic image. Therefore, Patent Document 1, which does not take into account the imaging environment and irradiation conditions, is unable to fully prevent deterioration in the image quality of the radiographic image.

[0007] The present disclosure provides a technique for improving the image quality of a radiographic image obtained from a radiographic imaging device in which imaging pixels with different characteristics due to structural differences are mixed. [Means for solving the problem]

[0008] An image processing device according to one aspect of the present disclosure includes: an acquisition means for acquiring a radiographic image including a plurality of pixel values ​​obtained from a plurality of imaging pixels by radiography using a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged; a determination means for determining, from among the plurality of pixel values, pixel values ​​obtained from a first type of imaging pixel of the radiation imaging device and pixel values ​​obtained from a second type of imaging pixel having a configuration different from that of the first type of imaging pixel; a correction means for performing a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performing a second correction process different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, the correction process to be applied to the pixel values ​​to be corrected is determined based on pixel value information obtained from pixel values ​​of a portion of the radiographic image. [Effects of the Invention]

[0009] According to the present disclosure, the image quality of a radiographic image obtained from a radiographic imaging device in which imaging pixels with different characteristics due to structural differences are mixed is improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an example of the arrangement of a radiation imaging system according to a first embodiment. [Figure 2] 1 is a block diagram showing an example of the arrangement of a radiation imaging apparatus according to a first embodiment. [Figure 3] FIG. 2 is a diagram showing a detailed configuration of an amplifier unit in the radiation imaging apparatus. [Figure 4] 5 is a flowchart showing a radiation imaging process according to the first embodiment. [Figure 5] 5 is a flowchart showing pixel correction processing according to the first embodiment. [Figure 6] 10A and 10B are flowcharts showing pixel correction processing according to dose / pixel value. [Figure 7] 10 is a flowchart showing a radiation imaging process according to the second embodiment. [Figure 8] 10 is a flowchart showing pixel correction processing according to the second embodiment. [Figure 9] 10 is a flowchart illustrating a correction process according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0012] Furthermore, the term radiation may typically refer to X-rays, but is not limited to X-rays and may also apply to other types of radiation (eg, α-rays, β-rays, γ-rays, etc.).

[0013] (First embodiment) Fig. 1 is a block diagram showing an example of the overall configuration of a radiation imaging system 10 according to the first embodiment. The radiation imaging system 10 includes a control device 100, a radiation generating device 101, and a radiation imaging device 102. Although Fig. 1 shows an example in which the control device 100 and the radiation imaging device 102, and the control device 100 and the radiation generating device 101 communicate with each other via a wire, a configuration in which they communicate wirelessly is also possible. Furthermore, some or all of the components of the control device 100 may be provided in the radiation imaging device 102.

[0014] The control device 100 controls the dose of radiation (exposure dose) irradiated from the radiation generation device 101 by providing radiation generation conditions such as tube current and tube voltage to the radiation generation device 101. The control device 100 also performs image processing on the radiation image received from the radiation imaging device 102 to generate a radiation image in which artifacts and the like are reduced or prevented. The control device 100 of this embodiment includes, as functional units, a controller 103, a radiation source interface 104, an imaging interface 105, an image processing unit 106, and a display unit 107. A general-purpose computer equipped with a processor (CPU), a main memory device, an auxiliary memory device, and a display can be used as the control device 100. In this case, the processor executes a predetermined program to realize each of the above-mentioned functional units.

[0015] The controller 103 has a user interface and accepts user inputs for setting a dose target value, radiation irradiation intensity (including, for example, irradiation time (ms), tube current (mA), and tube voltage (kV)), an irradiation field, which is an area where radiation is detected, and the like. The dose target value is used to determine the end of irradiation in automatic exposure control (AEC), and for example, an exposure index (EI) value, which is a dose index value, may be used. The controller 103 sets the input radiation irradiation intensity in the radiation generation device 101 via the radiation source interface 104. The controller 103 also determines a dose target threshold used in automatic exposure control (AEC) based on the dose target value, radiation irradiation intensity, communication delay between units, processing delay, and the like. The dose target threshold is set in the radiation imaging device 102 via the imaging interface 105.

[0016] The controller 103 is connected to an exposure switch 110 for instructing the radiation generation device 101 to start irradiating radiation. The radiation imaging device 102 performs an operation to reset its electrical circuit, such as one or more pre-reads, immediately after power-on or after each radiation imaging session. When a predetermined condition is met, the radiation imaging device 102 outputs a ready signal. The pre-read is a readout operation for resetting charges generated by dark current charge accumulation in the conversion elements of the radiation imaging device 102. If the pre-read is performed multiple times, the readout is repeated at a predetermined interval. The predetermined condition may be, for example, at least one of a predetermined time having elapsed since the start of the reset operation and a signal value obtained by the pre-read has become smaller than a threshold. The predetermined time may be set by a user. After the controller 103 receives the ready signal from the radiation imaging device 102 via the imaging interface 105, the user operates the exposure switch 110. The radiation source interface 104 then sends an instruction to the radiation generation device 101 to start irradiation. Upon receiving the signal instructing the start of irradiation, the radiation generating device 101 starts irradiating radiation at the set radiation irradiation intensity. The radiation imaging device 102 detects the irradiation of radiation and starts accumulating electric charges, thereby starting radiation imaging.

[0017] The radiation imaging device 102 has an AEC function that determines the end of imaging based on a signal (dose information) read from a detection element 2052, which will be described later. The radiation imaging device 102 acquires an integrated value of the radiation exposure dose based on the signal from the detection element 2052, and transmits a stop notification to the control device 100 when the integrated value reaches a target threshold. The stop notification is a signal requesting the end of radiation irradiation. In response to the imaging interface 105 receiving the stop notification from the radiation imaging device 102, the radiation source interface 104 transmits an instruction to the radiation generation device 101 to terminate radiation irradiation. In response to receiving the signal instructing the end of irradiation, the radiation generation device 101 terminates radiation irradiation.

[0018] When radiation imaging is completed, the imaging interface 105 receives radiation image data from the radiation imaging device 102 and outputs it to the image processing unit 106. The image processing unit 106 performs image processing such as offset correction processing, gain correction processing, and noise reduction processing on the radiation image. The determination unit 161 classifies pixel values ​​by type based on the configuration of the imaging pixels, and the correction unit 162 applies different correction processing to the pixel values ​​depending on the classification result. Details of the processing by the determination unit 161 and the correction unit 162 will be described later. The image processing unit 106 transmits the radiation image data after image processing to the display unit 107. The display unit 107 converts the radiation image data acquired from the image processing unit 106 into a two-dimensional image (radiation image) and displays the converted two-dimensional image (radiation image) on a general-purpose display or the like. This allows the operator to observe the radiation image of the subject P. The control device 100 including the image processing unit 106 is an example of an image processing device according to the present disclosure.

[0019] 2 is a block diagram showing an example of the configuration of a radiation imaging device 102 according to the first embodiment. The radiation imaging device 102 has a plurality of imaging pixels including multiple types of imaging pixels 201, 204, and 207, a plurality of drive lines 210 for driving the plurality of imaging pixels, and a plurality of signal lines 220 for acquiring signals from the plurality of imaging pixels. The plurality of imaging pixels are two-dimensionally arranged in an imaging region IR to form a plurality of rows and a plurality of columns. The plurality of drive lines 210 are arranged corresponding to each of the plurality of pixel rows, and each drive line 210 corresponds to one of the pixel rows. The plurality of signal lines 220 are arranged corresponding to each of the plurality of pixel columns, and each signal line 220 corresponds to one of the pixel columns.

[0020] The multiple imaging pixels include multiple imaging pixels 201, one or more imaging and detection pixels 204, and multiple imaging pixels 207 located in the same row as the imaging and detection pixel 204. In this embodiment, the imaging pixel 201, the imaging and detection pixel 204, and the imaging pixel 207 are treated as first, second, and third types of imaging pixels, each having a different configuration. The configuration of each type of imaging pixel will be described below. However, imaging pixels with different configurations differ in at least one of the following: sensitivity to radiation dose, noise, aperture ratio, parasitic capacitance, linearity, saturation characteristics, and offset characteristics. Such differences in characteristics can affect radiographic images and cause degradation of image quality.

[0021] The first type of imaging pixel 201 has a configuration in which a single photoelectric conversion element (imaging element 208) is arranged in the area of ​​one pixel. The second type of imaging and detection pixel 204 has a configuration in which two photoelectric conversion elements, each capable of independently reading out electric charges, are arranged in the area of ​​one pixel. One of the two photoelectric conversion elements is an imaging element 2051 for acquiring pixel values ​​constituting a radiographic image, and the other is a detection element 2052 for monitoring the radiation dose during AEC control. The third type of imaging pixel 207 has a single photoelectric conversion element (imaging element 208) for acquiring a radiographic image in its area. However, the imaging pixel 207 is an imaging pixel arranged in the same row as the imaging and detection pixel 204, and wiring (detection drive line 211) for controlling the detection element 2052 of the imaging and detection pixel 204 passes through the area of ​​that pixel. In the imaging and detection pixel 204, the area allocated to one pixel is divided by the imaging element 2051 and the detection element 2052. For this reason, the area (aperture ratio) of the imaging element 2051 is smaller than that of the imaging pixel 201. Furthermore, the imaging element 208 of the imaging pixel 207 is affected by the detection drive line 211, such that the aperture ratio is smaller than that of the imaging element 202 of the imaging pixel 201. As a result, the imaging pixel 201, the imaging and detection pixel 204, and the imaging pixel 207 are imaging pixels with mutually different characteristics. In this embodiment, the characteristics of the imaging pixel 201 are used as the reference. Note that, hereinafter, the imaging pixel 201 will also be referred to as a normal imaging pixel, and the imaging pixel 207 will also be referred to as an imaging pixel in an AEC row.

[0022] The imaging pixel 201 includes an imaging element 202, which is a conversion element that converts radiation into an electrical signal, and a switch element 203 that connects the imaging element 202 to a corresponding signal line 220. Similarly, the imaging pixel 207 includes an imaging element 208, which is a conversion element that converts radiation into an electrical signal, and a switch element 209 that connects the imaging element 208 to a corresponding signal line 220. The imaging and detection pixel 204 includes an imaging element 2051, which is a conversion element that converts radiation into an electrical signal, and a detection element 2052. An imaging switch element 2061 that connects the imaging element 2051 to a corresponding signal line 220 is connected to the imaging element 2051. Furthermore, a detection switch element 2062 that connects the detection element 2052 to a corresponding signal line 220 is connected to the detection element 2052. The imaging and detection pixel 204 divides one pixel into an imaging element 2051 and a detection element 2052, so that radiation information for a radiation image can be stored in the imaging element 2051 while the detection element 2052 can detect the dose during radiation irradiation. The dose detection by the detection element 2052 can be used for the AEC function. The imaging and detection pixel 204 is arranged so as to be included in the row and column formed by the imaging pixel 201 and the imaging pixel 207.

[0023] The imaging elements 202, 208, 2051, and the detecting elements 2052 may be configured with a scintillator that converts radiation into light and a photoelectric conversion element that converts light into an electrical signal. The scintillator is generally formed in a sheet shape so as to cover the imaging region IR, and is shared by multiple pixels. Note that the imaging elements 202, 208, 2051, and the detecting elements 2052 may also be configured with a conversion element that directly converts radiation into an electrical signal.

[0024] The switch elements 203, 209, 2053, and 2054 may each include a thin film transistor (TFT) whose active region is made of a semiconductor such as amorphous silicon or polycrystalline silicon. In the imaging pixel 201, a first electrode of the imaging element 202 is connected to a first main electrode of the switch element 203. A second electrode of the imaging element 202 is connected to a bias line 230. The bias line 230 has multiple column-direction bias lines extending in the column direction, and each column-direction bias line is connected to the second electrodes of multiple imaging elements 202 arranged in the same column. A bias voltage Vs supplied from a power supply circuit 240 is applied to the second electrode of the imaging element 202 via the bias line 230. The second main electrodes of the switch elements 203 of one or more imaging pixels 201 included in one column are connected to one signal line 220. The control electrodes of the switch elements 203 of the imaging pixels 201 are connected to a drive line 210. The same applies to the imaging pixel 207. That is, the first electrode of the imaging element 208 is connected to the first main electrode of the switch element 209, and the second electrode is connected to the bias line 230. In addition, the second main electrode of the switch element 209 is connected to the signal line 220.

[0025] In the imaging and detection pixel 204, a first electrode of the imaging element 2051 is connected to a first main electrode of the imaging switch element 2061, and a first electrode of the detection element 2052 is connected to a first main electrode of the detection switch element 2062. Respective second electrodes of the imaging element 2051 and the detection element 2052 are connected to a bias line 230. Respective first main electrodes of the imaging switch element 2061 and the detection switch element 2062 are connected to the same signal line 220. A control electrode of the imaging switch element 2061 is connected to a drive line 210, and a control electrode of the detection switch element 2062 is connected to a detection drive line 211.

[0026] The drive circuit 250 is configured to supply drive signals to the pixels to be driven via multiple drive lines 210 and detection drive lines 211 in accordance with control signals from the control unit 280. The drive lines 210 and the detection drive lines 211 may be connected to different drive circuits. For example, the drive lines 210 may be connected to a drive circuit for imaging, and the detection drive lines 211 may be connected to a drive circuit for radiation dose detection. The drive signals are signals for turning on switch elements included in the pixels to be driven. The switch elements included in each pixel are turned on by a high-level signal and turned off by a low-level signal. Therefore, these high-level signals are called drive signals. When a drive signal is supplied to a pixel, the signal stored in the conversion element of that pixel becomes available for readout by the readout circuit 260.

[0027] The readout circuit 260 is configured to read out signals from a plurality of pixels through a plurality of signal lines 220. The readout circuit 260 includes a plurality of amplifiers 261, a multiplexer 262, and an analog-to-digital converter (hereinafter, referred to as AD converter) 263. Each of the plurality of signal lines 220 is connected to a corresponding one of the plurality of amplifiers 261 of the readout circuit 260. One signal line 220 corresponds to one amplifier 261. The multiplexer 262 selects the plurality of amplifiers 261 in a predetermined order, and supplies a signal from the selected amplifier 261 to an AD converter (ADC) 263. The ADC 263 converts the supplied signal into a digital signal and outputs it.

[0028] Signals read out from the imaging pixels 201, the imaging and detection pixels 204, and the imaging pixels 207 in the AEC rows are supplied to the signal processing unit 270, where they are processed, such as calculated and stored. Specifically, the signal processing unit 270 includes a calculation unit 271 and a storage unit 272. The calculation unit 271 generates a radiographic image based on signals read out from the imaging elements 2051 of the imaging pixels 201, the imaging pixels 207, and the imaging and detection pixels 204, and stores the generated radiographic image in the storage unit 272. Furthermore, signals read out from the detection elements 2052 of the imaging and detection pixels 204 are supplied to the signal processing unit 270, where they are processed, such as calculated and stored, by the calculation unit 271. Specifically, the signal processing unit 270 generates irradiation information regarding the irradiation of radiation to the radiation imaging device 102 based on the signals read out from the detection elements 2052 of the imaging and detection pixels 204, and stores the generated irradiation information in the storage unit 272. The irradiation information includes, for example, information indicating the results of detecting the irradiation of radiation to the radiation imaging device 102 (which can be used to detect the start of irradiation), and information indicating the radiation irradiation dose and / or cumulative irradiation dose (which can be used for the AEC function).

[0029] The control unit 280 controls the drive circuit 250 and the readout circuit 260 based on information from the signal processing unit 270. The control unit 280 controls, for example, the start and end of exposure (accumulation of charges corresponding to the irradiated radiation by the imaging pixels 201) based on irradiation information (e.g., the radiation exposure dose) stored in the memory unit 272 of the signal processing unit 270 (AEC function). To obtain the irradiation information (radiation exposure dose), the control unit 280 controls the drive circuit 250 to scan only the detection drive lines 211, thereby enabling only the signals of the detection elements 2052 of the imaging and detection pixels 204 to be readable. Next, the control unit 280 controls the readout circuit 260 to read out the signals of the columns corresponding to the detection elements 2052, thereby obtaining information indicating the radiation exposure dose. Through these operations, the radiation imaging device 102 can obtain irradiation information for the imaging and detection pixels 204 during radiation exposure. Furthermore, the control unit 280 outputs (transmits) the radiographic images stored in the storage unit 272 to the outside via the communication I / F 291.

[0030] FIG. 3 shows a detailed example of the circuit configuration of the amplifier unit 261. The amplifier unit 261 includes a differential amplifier circuit AMP and a sample-and-hold circuit SH. The differential amplifier circuit AMP amplifies and outputs a signal appearing on the signal line 220. The control unit 280 can reset the potential of the signal line 220 by supplying a control signal φR to the switch element of the differential amplifier circuit AMP. The output from the differential amplifier circuit AMP can be held by the sample-and-hold circuit SH. The control unit 280 causes the sample-and-hold circuit SH to hold the signal (the output from the differential amplifier circuit AMP) by supplying a control signal φSH to the switch element of the sample-and-hold circuit SH. The signal held in the sample-and-hold circuit SH is read out by the multiplexer 262.

[0031] Next, the process from the start to the end of imaging of the subject P according to the first embodiment will be described with reference to the flowchart in FIG. 4. In step S401, the controller 103 accepts and determines imaging conditions input by the user via an imaging condition input unit (user interface). The imaging conditions include, for example, information such as a dose target value, radiation irradiation intensity (irradiation time (ms), tube current (mA), tube voltage (kV)), an irradiation field which is an area for detecting radiation, and an imaging region. The controller 103 transmits the accepted imaging conditions (including a dose target threshold value acquired based on the dose target value) to the radiation generation device 101 and the radiation imaging device 102 via the radiation source interface 104 and the imaging interface 105 as appropriate. The imaging conditions are also provided to the image processing unit 106.

[0032] In step S402, after receiving a preparation completion signal from the radiation imaging device 102, the controller 103, upon receiving an irradiation start operation by the user from the exposure switch 110, causes the radiation generation device 101 to start irradiation. This starts radiation imaging and a radiation image is acquired. More specifically, in response to the control device 100 receiving the preparation completion signal and then receiving the irradiation start operation, the radiation source interface 104 transmits an irradiation start signal to the radiation generation device 101 instructing it to start irradiating radiation. Upon receiving the irradiation start signal, the radiation generation device 101 irradiates radiation toward the subject P in accordance with the imaging conditions (radiation irradiation intensity) determined in step S401. The radiation imaging device 102 determines the start of radiation irradiation based on a signal read out from the detection element 2052 of the imaging and detection pixel 204, and starts radiation imaging. During radiation imaging, radiation that has passed through the subject P and entered the radiation imaging device 102 is converted into a dose information signal for each imaging pixel. In the radiation imaging device 102, the control unit 280 determines whether the integrated value of the irradiated radiation dose has reached the dose target threshold based on a signal from the detection element 2052 of the imaging and detection pixel 204. If it is determined that the integrated value has reached the dose target threshold, the notification unit 290 of the radiation imaging device 102 transmits a stop notification requesting the end of radiation irradiation from the communication I / F 291. When the stop notification is received by the imaging interface 105, the radiation source interface 104 instructs the radiation generation device 101 to stop radiation irradiation. In this way, one radiation imaging session is completed.

[0033] In step S403, the imaging interface 105 transmits a dark image acquisition signal to the radiation imaging device 102. Upon receiving the dark image acquisition signal, the radiation imaging device 102 acquires signals from a plurality of imaging pixels without irradiating radiation and transmits the signals to the image processing unit 106. The image processing unit 106 generates and stores a dark image based on the received signals from the pixels. In step S404, the image processing unit 106 performs offset correction on the radiation image acquired in step S402 (dose information signals obtained from the imaging pixels). More specifically, the correction unit 162 of the image processing unit 106 subtracts the dark image acquired in step S403 from the radiation image acquired in step S402 to obtain a radiation image after offset correction.

[0034] In step S405, the image processing unit 106 performs a correction process on the pixel selected according to the pixel's characteristic information. In this embodiment, the characteristic information indicates the type of imaging pixel, i.e., whether the imaging pixel is a normal imaging pixel, an imaging pixel in an AEC row, or an imaging and detection pixel. Figure 5 shows a flowchart of the correction process in step S405.

[0035] In this embodiment, the determination unit 161 determines the type of imaging pixel for the pixel value of the radiation image after offset correction, and the correction unit 162 applies a correction process determined according to the determined type of imaging pixel to the pixel value. In this way, the correction unit 162 reduces or prevents image quality degradation by switching the correction process according to the type of imaging pixel (characteristics of the imaging pixel) determined by the determination unit 161.

[0036] Step S405 includes the processing steps of steps S500 to S504, and these processing steps are repeated for all pixels (step S505). First, in step S500, signal information of a pixel to be corrected is acquired. The signal information includes pixel characteristic information, pixel dose information, etc. As described above, the pixel characteristic information specifies whether the dose information signal to be processed is acquired from a normal imaging pixel, an imaging and detection pixel, or an imaging pixel in an AEC row. In step S501, the determination unit 161 determines the pixel characteristic (pixel type) based on the characteristic information. The correction process for the pixel is determined based on this determination result. Note that the signal information may include position information indicating the pixel's position (coordinates), and the pixel type may be obtained based on this position information and pre-stored position information of the imaging and detection pixel. In this case, the determination unit 161 determines whether the pixel is a normal imaging pixel, an imaging pixel in an AEC row, or an imaging and detection pixel by comparing the position information included in the signal information with the position information of the imaging and detection pixel.

[0037] If the determination unit 161 determines that the dose information signal is from a normal imaging pixel (imaging pixel 201), the process proceeds to step S502. The dose information signal is a pixel value expressed in quantization units (LSB) of AD conversion by the ADC 263, and hereinafter will also be simply referred to as a pixel value. In step S502, the correction unit 162 performs gain correction processing by dividing the pixel value of each pixel after offset correction by the corresponding pixel value of the gain image. The gain correction processing is a well-known process, and the gain image used in the gain correction processing is acquired in advance by capturing a radiological image in which no subject is present under predetermined irradiation conditions.

[0038] In step S501, if the determination unit 161 determines that the pixel value to be corrected is obtained from an imaging and detection pixel, the process proceeds to step S503a, and if it determines that the pixel value is obtained from an imaging pixel in an AEC row, the process proceeds to step S503b. Because the imaging and detection pixel and the imaging pixel in the AEC row have different characteristics, correction processes (correction processes in steps S503a and S504a or correction processes in steps S503b and S504b) are performed separately for each.

[0039] FIG. 6(a) is a flowchart showing offset correction A / B processing in steps S503a / S503b. The amount of output reduction in an imaging / detection pixel or an imaging pixel in an AEC row varies depending on the irradiation dose output from the radiation generation device 101. Therefore, the correction unit 162 determines and executes the correction processing to be applied based on the dose information signal included in the signal information acquired in step S500. If the pixel characteristic information indicates an imaging / detection pixel (step S503a), in step S601, the correction unit 162 acquires pixel value information related to the imaging pixel to be corrected based on a portion of pixel values ​​(dose information signal) of the radiographic image. The correction unit 162 determines which of the correction processing steps S602a to S602c to perform in accordance with the acquired pixel value information. Here, the pixel value information is, for example, the average value of dose information signals (pixel values) obtained from normal imaging pixels surrounding the imaging / detection pixel. For example, the average pixel values ​​obtained from a total of six normal imaging pixels, consisting of the upper three imaging pixels and the lower three imaging pixels of a 3x3 pixel array centered on the target imaging and detection pixel, can be used.

[0040] In step S601, if the pixel value information is less than 1000 LSB, the process proceeds to step S602a, where the correction unit 162 performs correction using correction value a obtained by substituting the pixel value information into approximation formula a. Similarly, if the pixel value information is equal to or greater than 1000 LSB and less than 30000 LSB, the process proceeds to step S602b, where the correction unit 162 performs correction using correction value b obtained by substituting the pixel value information into approximation formula b. Furthermore, if the pixel value information is equal to or greater than 30000 LSB, the process proceeds to step S602c, where the correction unit 162 performs correction using correction value c obtained by substituting the pixel value information into approximation formula c. In steps S602a to S602c, correction processes a to c are performed, respectively, to subtract (or add) correction values ​​a to c from (or add) the dose information signal (pixel value) to be corrected. Hereinafter, the correction processes in steps S602a to S602c are also referred to as offset correction. The correction process of step S503a (steps S602a to S602c) aims to compensate for the pixel values ​​from the imaging and detection pixels that cannot be fully corrected by the offset correction performed in step S404, and to correct offset characteristics that differ from those of normal imaging pixels. Approximation formulas a to c are generated in advance based on the results of actually measuring changes in offset characteristics (remaining correction amount) in response to the irradiation dose at the imaging and detection pixels 204, using radiation images and dark images obtained by the radiation imaging device 102. After step S503a, the process proceeds to step S504a.

[0041] When the pixel characteristic information indicates an imaging pixel in an AEC row (step S503b), the processing is the same as that of step S503a described above. However, the correction value used in step S503b is determined independently of step S503a. The approximate expressions a to c are generated in advance based on the results of actually measuring the change in offset characteristic (remaining correction amount) according to the exposure dose at the imaging pixel 207 in the AEC row, based on the radiation image and dark image obtained by the radiation imaging device 102. The purpose of step S503b is to compensate for the pixel value from the imaging pixel in the AEC row that could not be fully corrected by the offset correction performed in step S404. After step S503b, the processing proceeds to step S504b.

[0042] 6(b) is a flowchart showing the gain correction A / B processing in steps S504a / S504b. For example, in the case of an imaging / detection pixel (step S504a), in step S611, the correction unit 162 determines which of the correction processes in steps S612a to S612c to perform based on pixel value information. The pixel value information can be, for example, an average value obtained in the same manner as in step S601 (however, pixel values ​​after offset correction are used). However, in step S611, pixel value information obtained from the radiation image for which offset correction has been completed via step S503a is used. In steps S612a to S612c, correction processes x to z are performed to compensate for the amount of output reduction by dividing (or multiplying) the dose information signal (pixel value) to be corrected by the correction values ​​x to z (gain correction values) set for each step.

[0043] If the pixel value information is less than 1000 LSB (LSB is the quantization unit), the process proceeds to step S612a, where the correction unit 162 performs correction using a correction value x obtained by substituting the pixel value information into approximation formula x. If the pixel value information is 1000 LSB or more and less than 30000 LSB, the process proceeds to step S612b, where the correction unit 162 performs correction using a correction value y obtained by substituting the pixel value information into approximation formula y. If the pixel value information is 30000 LSB or more, the process proceeds to step S612c, where the correction unit 162 performs correction using a correction value z obtained by substituting the pixel value information into approximation formula z. In each of steps S612a to S612c, a correction process of dividing (or multiplying) a correction value is performed, and the correction process in steps S612a to S612c will hereinafter also be referred to as gain correction. The approximate expressions x to z are generated based on the results of actually measuring correction values ​​corresponding to the exposure doses of the imaging and detection pixels 204, based on multiple gain images obtained by the radiation imaging device 102 for multiple types of exposure doses, and are stored in the correction unit 162. The correction process in step S504a aims to perform gain correction on pixel values ​​after offset correction from the imaging and detection pixels using correction values ​​selected based on pixel characteristics and pixel value information. This correction process uses appropriate gain correction values ​​according to the exposure dose for pixel values ​​from imaging pixels (imaging and detection pixels) with different characteristics. As a result, output abnormalities caused by imaging pixels with different characteristics depending on the exposure dose are eliminated or reduced. The process in step S504b, which is executed when the characteristic information is an imaging pixel in an AEC row, is similar to step S504a. However, the approximate expressions x to z are generated for the imaging pixels in the AEC row, and the correction values ​​are determined independently of the imaging and detection pixels.

[0044] In addition to the dose information signal, imaging conditions input by the controller 103 may be taken into consideration. For example, in each of steps S602a to S602c and / or in each of steps S612a to S612c, the approximation formula may be switched based on the imaging conditions. The imaging conditions may include, for example, at least one of irradiation time, tube current, and tube voltage. For example, an approximation formula that determines the correspondence between pixel value information and correction values ​​for each tube voltage may be prepared, and the approximation formula to be used may be switched according to the imaging conditions.

[0045] Returning to FIG. 4 , in step S406, the correction unit 162 performs defect correction processing on defective pixels indicated by the pixel information held by the radiation imaging device 102 for the radiographic image that has been subjected to pixel correction according to the characteristics in step S405. Well-known defect correction processing may be used in step S406. In step S407, the image processing unit 106 performs Log conversion processing on the dose information signal for each pixel that has been subjected to defect correction in step S406. In step S408, the image processing unit 106 performs processing to reduce noise contained in the dose information signal (noise reduction processing) on ​​the dose information signal for each pixel that has been subjected to Log conversion processing in step S407. The noise reduction processing is a well-known processing, and is performed, for example, based on the information on the tube voltage, tube current, and imaging region received by the image processing unit 106 in step S401. In step S409, the image processing unit 106 performs processing to adjust the gradation (gradation processing) on ​​the dose information signal for each pixel that has been subjected to noise reduction processing in step S409. The gradation processing is performed based on the shooting conditions received by the image processing unit 106 in step S401.

[0046] In step S410, the image processing unit 106 transmits the signal subjected to the gradation adjustment in step S409 to the display unit 107. The display unit 107 displays the signal received from the image processing unit 106 as a two-dimensional image. In step S411, the controller 103 determines whether to continue or end the imaging based on an instruction input by the operator. If the controller 103 determines that the imaging should be continued (YES in step S411), the process returns to step S402, and the above-described process is repeated to capture a radiographic image again. On the other hand, if the controller 103 determines that the imaging should be ended (NO in step S411), the subject imaging process ends.

[0047] There is a method called fixed dark, in which the dark image acquired in step S403 during the first radiation imaging is used for offset correction in the second and subsequent radiation imaging sessions during continuous imaging. With fixed dark, the dark image acquired during the first radiation imaging session is used for offset correction in the second and subsequent radiation imaging sessions. Therefore, when fixed dark is used, step S403 is skipped for the second and subsequent radiation imaging sessions.

[0048] Furthermore, in steps S503a / S503b and S504a / S504b, the range of pixel value information classifications used to determine the approximation formula to be used from the three approximation formulas is not limited to the range exemplified in FIGS. 6(a) and 6(b). Furthermore, the range of pixel value information classifications may differ between processing imaging and detection pixels and processing imaging pixels in AEC rows. Furthermore, in steps S503a / S503b and S504a / S504b, three approximation formulas are prepared to determine the approximation formula to be used, but this is not limited thereto. The approximation formula may be determined from two approximation formulas, or from four or more approximation formulas. Furthermore, the correction value may be determined by substituting pixel value information into one approximation formula. In this case, the branching based on pixel value information in steps S601 and S611 can be omitted. Furthermore, the number of approximation formulas prepared may differ between imaging and detection pixels and imaging pixels in AEC rows.

[0049] As described above, the approximation formula is determined in advance so that, by substituting pixel value information, a correction value is obtained for bringing the pixel value obtained from the correction target imaging pixel closer to the pixel value obtained from a normal imaging pixel. Alternatively, the correction value may be determined by referencing a numerical value table instead of the approximation formula. In this case, the numerical value table stores correspondence between the pixel value information and the correction value for bringing the pixel value obtained from the correction target imaging pixel closer to the pixel value obtained from a normal imaging pixel. When a numerical value table is used, the branching based on the pixel value information in steps S601 and S611 can be omitted. Alternatively, a numerical value table may be prepared for each imaging condition, and a correction value corresponding to the pixel value information may be obtained by referencing a numerical value table selected according to the imaging condition.

[0050] Like the approximation formula, the numerical table used in steps S602a to S602c is generated based on actual measurement values ​​using the radiation imaging device 102. For example, the relationship between the amount of correction that cannot be fully performed (correction remaining amount) for the imaging / detection pixels and the imaging pixels of the AEC rows is actually measured from the radiation image and dark image obtained from the radiation imaging device 102. Then, a numerical table is determined so as to eliminate the correction remaining amount based on the relationship between the pixel value information and the actually measured correction remaining amount. Similarly to the approximation formula, the numerical table used in steps S612a to S612c can be obtained based on actual measurement values ​​using the radiation imaging device 102. For example, a numerical table can be generated by determining a correction value for each piece of dose value information based on multiple gain images obtained under different irradiation conditions so as to absorb differences in output due to the type of imaging pixel. Note that when a numerical table is used, a correction value corresponding to pixel value information not included in the numerical table may be obtained by interpolation. Alternatively, the approximation formula and the numerical table may be used separately depending on the pixel value information, for example, by using the approximation formula in step S602a and the numerical table in step S602b.

[0051] In acquiring the dark image and the gain image, the signal from the imaging and detection pixel may be used only from the imaging element, or the sum of the signals from the imaging element and the detection element may be used. The approximation formula and the numerical table will differ depending on how the signal from the imaging and detection pixel is handled in acquiring the dark image and the gain image.

[0052] Although the pixel value information used to determine the correction value is the pixel values ​​of the six normal imaging pixels surrounding (above and below) the imaging and detection pixel or the imaging pixel in the AEC row, it is not limited to this. For example, the average of the pixel values ​​of the three normal imaging pixels arranged above the imaging and detection pixel or the imaging pixel in the AEC row may be used. Furthermore, the pixel value obtained from the imaging and detection pixel that is the imaging pixel to be corrected or the imaging pixel in the AEC row may be used, or the ratio of the average value to the pixel value obtained from the imaging pixel to be corrected may be used.

[0053] In another embodiment, the time elapsed from when the radiation imaging device 102 is powered on or when imaging is completed until a ready signal is output may be taken into consideration when determining the correction values ​​in steps S503a / S503b and steps S504a / S504b. As described above, after powering on or after each radiation imaging session, the radiation imaging device 102 resets its electrical circuitry and outputs a ready signal when imaging preparation is complete. The radiation imaging device 102 notifies the control device 100 of the time elapsed from when the reset operation begins until the ready signal is output, thereby enabling the control device 100 to acquire the elapsed time. Alternatively, the control device 100 may measure the time elapsed from when the control device 100 receives a signal corresponding to when power is turned on or when imaging is completed from the radiation imaging device 102 until the imaging preparation complete signal is received. In another embodiment, both the offset correction in steps S602a to S602c and the gain correction in steps S612a to S612c may be performed, and steps S504a / S504b may be omitted. In this case, the correction values ​​for the offset correction and the gain correction are determined based on the determination of the pixel value information in step S601. As another example, steps S502a / S503b may be omitted and only the gain correction may be performed. In this case, an approximation formula or a numerical value table that takes both the offset correction and the gain correction into consideration may be used to determine the correction values.

[0054] As described above, according to the first embodiment, by switching the correction process depending on the pixel characteristics (normal imaging pixels, imaging pixels in the AEC row, imaging and detection pixels), it is possible to reduce or prevent degradation of image quality caused by differences in pixel characteristics.

[0055] (Second embodiment) In the first embodiment, a case where the characteristics of the normal imaging pixels, the imaging pixels in the AEC row, and the imaging and detection pixels are different from one another is described. In the second embodiment, a case where the characteristics of the normal imaging pixels and the imaging pixels in the AEC row are equivalent, but the characteristics of the imaging and detection pixels 204 are different, is described. Possible configurations for equivalently equating the characteristics of the normal imaging pixels (imaging pixels 201) and the imaging pixels in the AEC row (imaging pixels 207) include the following. For example, a configuration may be adopted in which the aperture ratio of the normal imaging pixels without the detection drive lines 211 is limited so that the aperture ratio of the normal imaging pixels and the aperture ratio of the imaging pixels in the AEC row are equivalent. Alternatively, a configuration may be adopted in which the detection drive lines 211 are arranged below the image sensor, and the aperture ratio of the imaging pixels in the AEC row is maintained equivalent to that of the normal imaging pixels.

[0056] The configuration of the radiation imaging system 10 of the second embodiment is the same as that of the first embodiment (FIGS. 1, 2, and 3). FIG. 7 is a flowchart illustrating the radiation imaging process of the second embodiment. The difference from the flowchart of the first embodiment (FIG. 4) is that the process of step S405 is replaced by S701 and S702. That is, in the second embodiment, after offset correction (step S404) and gain correction (step S701) are performed on the radiation image acquired in S402, correction processing is performed using correction values ​​according to the characteristics (step S702).

[0057] First, in step S701, the image processing unit 106 performs gain correction processing on the radiation image after offset correction. Then, in step S702, the determination unit 161 and the correction unit 162 perform pixel correction according to their characteristics. The pixel correction in step S702 is performed on each of all pixels of the radiation image as a processing target.

[0058] FIG. 8A is a flowchart showing the correction process in step S702. Step S702 includes processing steps S800 to S802, and these processing steps are repeated for all pixels (step S803). First, in step S800, signal information of the pixel to be corrected is acquired. In step S801, the determination unit 161 determines whether the pixel to be corrected is a normal imaging pixel, an imaging pixel in an AEC row, or an imaging and detection pixel, using pixel characteristic information included in the acquired signal information. In this embodiment, as described above, normal imaging pixels and imaging pixels in an AEC row have similar characteristics and are treated as the same type of imaging pixel. In other words, normal imaging pixels or imaging pixels in an AEC row do not experience output reduction like the imaging and detection pixel 204. Therefore, if the determination unit 161 determines that the imaging pixel to be corrected is a normal imaging pixel or an imaging pixel in an AEC row, step S802 is skipped, and correction according to the characteristic information and pixel value is not performed. On the other hand, if the determining unit 161 determines that the pixel to be processed is an imaging / detection pixel, the process proceeds to step S802. In step S802, the correcting unit 162 performs correction processing on the pixel to be processed, which is determined based on the pixel values ​​of part of the radiographic image.

[0059] FIG. 8B is a flowchart showing the correction process in step S802. The amount of output reduction due to the characteristics of the imaging and detection pixel 204 varies depending on the irradiation dose. Therefore, in step S811, the determination unit 161 determines the correction process to be applied to the processing target pixel based on the pixel value information for the imaging pixel to be corrected. The pixel value information is as described in the first embodiment (steps S601 and S611). In this example, the pixel value information is classified into three ranges: less than 1000 LSB, 1000 LSB or more but less than 30000 LSB, and 30000 LSB or more. In steps S812a to S812c, the correction unit 162 performs correction processes a to c, which subtract (or add) correction values ​​a to c determined from the pixel value information and approximation formulas a to c from (or add) the pixel value to be corrected. The processes in steps S812a to S812c are the same as the processes in steps S602a to S602c in the first embodiment. Then, in steps S813a to S813c, the correction unit 162 performs correction processes x to z in which the pixel values ​​to be corrected are divided (or multiplied) by correction values ​​x to z determined from the pixel value information and approximate expressions x to z. The processes in steps S813a to S813c are similar to the processes in steps S612a to S612c in the first embodiment.

[0060] After steps S800 to S802 are performed on the pixel values ​​of all imaging pixels in the radiographic image, the process proceeds to step S406 in FIG. 7. In step S406, the correction unit 162 performs known defect correction on the radiographic image. Note that steps S812a to S812c may be omitted from the process of step S802 shown in FIG. 8(b). In that case, steps S813a to S813c may perform correction processing in which the pixel value to be corrected is divided (or multiplied) by a correction value that takes offset correction into consideration. Furthermore, in the above description, a configuration has been described in which correction processing is applied assuming that the characteristics of normal imaging pixels and imaging pixels in AEC rows are equivalent. However, as in the first embodiment, normal imaging pixels and imaging pixels in AEC rows may be treated as imaging pixels with different characteristics (different types of imaging pixels). In that case, even if a pixel is determined to be an imaging pixel in an AEC row in step S801, pixel correction is performed according to the pixel value information (however, correction processing independent of the pixel correction for imaging and detection pixels is used). Furthermore, in classifying the characteristics of the imaging pixels in the first embodiment (step S501), normal imaging pixels and imaging pixels in the AEC row may be regarded as imaging pixels with the same characteristics (same type) as in the second embodiment.

[0061] As described above, according to the second embodiment, by adding correction according to the characteristics to pixel values ​​after offset correction and gain correction, it is possible to reduce or prevent degradation of image quality caused by differences in pixel characteristics.

[0062] (Third embodiment) In some cases, correction errors are noticeable in high-contrast areas such as metal devices and implants in the imaging and detection pixel 204 or in a line in which the imaging and detection pixel 204 and the imaging pixel 207 are aligned. The present inventors have discovered that in such cases, artifacts can be prevented from occurring even in high-contrast images by performing defect correction in specific cases, such as when the outputs of the imaging and detection pixel 204 and the imaging pixel 207 are low, saturated, or near-saturated. In the third embodiment, a configuration will be described in which the imaging and detection pixel 204 is set as a defective pixel in specific cases, such as when the output is low or high, in accordance with the dose information signal, and is subjected to defect correction, thereby further improving image quality.

[0063] The configuration of the radiation imaging system 10 of the third embodiment is the same as that of the first embodiment (FIGS. 1, 2, and 3). The radiation imaging process is also the same as that of the first embodiment (FIGS. 4, 5, and 6), except for the processing in steps S503a / S503b. FIG. 9A is a flowchart showing the processing in steps S503a / S503b according to the third embodiment. In step S601, the determination unit 161 determines that the pixel value information is low output when it is smaller than a first threshold (e.g., 500 LSB). Furthermore, the determination unit 161 determines that the pixel value information is saturated or high output near saturation (hereinafter simply referred to as saturated) when it is larger than a second threshold (e.g., 50,000 LSB). If it is determined from the pixel value information that the pixel value of the imaging pixel to be corrected is low output or saturated, the process proceeds to step S901. In step S901, the correction unit 162 sets the pixel information of the imaging pixel to a defective pixel, and skips the correction processes a to c (steps S602a to S602c) and the gain correction (steps S504a / S504b). In step S406 of Fig. 4, defect correction is performed on the pixel values ​​of the imaging pixels designated as defective pixels in the pixel information. In this way, defect correction is performed by regarding imaging and detection pixels and imaging pixels in AEC rows that are in a low output or saturated state as defective pixels, thereby improving the image quality of the radiographic image.

[0064] The above describes the processing of the third embodiment based on the radiographic processing of the first embodiment. However, the radiographic processing of the second embodiment can also be configured to detect low output or saturation. FIG. 9B is a flowchart showing the processing of step S802 according to the second embodiment (FIG. 8). In step S811, the determination unit 161 determines that the pixel value information is low output if it is smaller than the first threshold, and determines that the pixel value information is saturated if it is larger than the second threshold. If the determination unit 161 determines that the pixel value information is low output or saturated, the processing proceeds to step S911. In step S911, the correction unit 162 sets the pixel information of the imaging pixel to a defective pixel, and skips the subsequent correction processes a to c (steps S812a to 812c) and correction processes x to z (steps S813a to 813c). In step S406 of FIG. 7, defect correction is performed on pixels designated as defective pixels by the pixel information. In this way, the imaging pixels of the imaging and detection pixels that are in a low output or saturated state are regarded as defective pixels and defect correction is performed, thereby improving the image quality of the radiation image.

[0065] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0066] The disclosure of this specification includes the following imaging device, imaging system, method, and program. (Item 1) an acquisition means for acquiring a radiographic image including a plurality of pixel values ​​obtained from a plurality of imaging pixels by radiography using a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged; a determination means for determining, from among the plurality of pixel values, pixel values ​​obtained from a first type of imaging pixel of the radiation imaging device and pixel values ​​obtained from a second type of imaging pixel having a configuration different from that of the first type of imaging pixel; a correction means for performing a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performing a second correction process different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, the image processing device determines the correction process to be applied to the pixel values ​​to be corrected based on pixel value information obtained from pixel values ​​of a portion of the radiographic image. (Item 2) Item 1. An image processing device according to item 1, wherein the first type of imaging pixel has a configuration in which a single conversion element is arranged in the area of ​​one pixel, and the second type of imaging pixel has a configuration in which two conversion elements capable of independently reading out electric charges are arranged in the area of ​​one pixel, and a pixel value is provided from one of the two conversion elements, a first conversion element. (Item 3) the determining means further determines, from the plurality of pixel values, pixel values ​​obtained from a third imaging element included in a third type of imaging pixel having a configuration different from the first type of imaging pixel and the second type of imaging pixel; the correction means performs the second correction process on pixel values ​​obtained from the third type of image sensor; 3. The image processing device according to item 2, wherein the second correction processing determines a correction processing to be applied to pixel values ​​from the third type of imaging pixels based on the pixel value information, independently of a correction processing to be applied to pixel values ​​from the second type of imaging pixels. (Item 4) Item 3. The image processing device according to item 3, wherein the third type imaging pixel has a configuration in which a single conversion element connected to the same drive line as the first conversion element of the second type imaging pixel is arranged in a region of one pixel, and a drive line for a second conversion element, which is the other of the two conversion elements, passes through the region. (Item 5) the first correction process includes offset correction using a dark image and gain correction using a gain image; 5. The image processing device according to any one of items 1 to 4, wherein the second correction processing is a correction processing determined based on the pixel value information for pixel values ​​that have been subjected to the offset correction. (Item 6) the first correction process includes offset correction using a dark image and gain correction using a gain image; 5. The image processing device according to any one of items 1 to 4, wherein the second correction processing is a correction processing determined based on the pixel value information for pixel values ​​that have been subjected to the offset correction and the gain correction. (Item 7) 7. The image processing device according to item 5 or 6, wherein the second correction process includes a correction process of adding or subtracting a first correction value determined based on the pixel value information. (Item 8) 8. The image processing device according to any one of items 5 to 7, wherein the second correction process includes a correction process of multiplying or dividing by a second correction value determined based on the pixel value information. (Item 9) 9. The image processing device according to any one of items 1 to 8, wherein the second correction processing is determined based on further shooting conditions. (Item 10) 10. The image processing device according to item 9, wherein the imaging conditions include an irradiation time, a tube voltage, and a tube current set in a radiation generating device used for the radiation imaging. (Item 11) 11. The image processing device according to any one of items 1 to 10, wherein the second correction process is further determined based on the elapsed time from when the radiation imaging device is turned on or when one radiation imaging session is completed until preparation for the next radiation imaging session is completed. (Item 12) In the second correction process, a correction value obtained by substituting a value determined based on the pixel value information into an approximation formula is used; 12. The image processing device according to any one of items 1 to 11, wherein the approximation formula is determined in advance to convert a pixel value obtained from an imaging pixel to be corrected into a correction value that brings the pixel value obtained from the imaging pixel of the first type closer to the pixel value obtained from the imaging pixel of the first type. (Item 13) In the second correction process, a value determined based on the pixel value information and a correction value obtained by referring to a numerical value table are used; 12. The image processing device according to any one of items 1 to 11, wherein the numerical value table holds a correspondence between a correction value for making a pixel value obtained from an imaging pixel to be corrected closer to a pixel value obtained from the first type imaging pixel and a value determined based on the pixel value information. (Item 14) 14. The image processing device according to any one of items 1 to 13, wherein the second correction process sets an imaging pixel to be corrected as a defective pixel to be subjected to defect correction based on the pixel value information. (Item 15) 15. The image processing device according to any one of items 1 to 14, wherein the second correction process is determined based on any one of an average value of pixel values ​​obtained from a plurality of imaging pixels of the first type surrounding an imaging pixel to be corrected, a pixel value obtained from the imaging pixel to be corrected, and a ratio between the average value and the pixel value obtained from the imaging pixel to be corrected. (Item 16) 16. The image processing device according to any one of items 1 to 15, wherein the determination means determines whether an imaging pixel providing a pixel value is the first type imaging pixel or the second type imaging pixel based on positions in the radiation image of the plurality of pixel values ​​included in the pixel value information. (Item 17) a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged, the plurality of imaging pixels including a first type imaging pixel having a configuration in which a single conversion element is arranged in the area of ​​one pixel, and a second type imaging pixel having a configuration in which two conversion elements capable of independently reading out electric charges are arranged in the area of ​​one pixel, and a pixel value is provided from one of the two conversion elements; an image processing device that processes a radiographic image including a plurality of pixel values ​​obtained from the plurality of imaging pixels by radiography using the radiographic imaging device, The image processing device includes: a determining means for determining, from among the plurality of pixel values, pixel values ​​obtained from the first type of imaging pixel and pixel values ​​obtained from the second type of imaging pixel; a correction means for performing a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performing a second correction process different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, the correction process to be applied to the pixel value to be corrected is determined based on pixel value information obtained from pixel values ​​of a portion of the radiographic image. (Item 18) Item 18. The radiation imaging system of item 17, wherein the radiation imaging device performs automatic exposure control based on dose information detected from a second conversion element different from the first conversion element of the two conversion elements, and a first conversion element of the two conversion elements provides a pixel value. (Item 19) an acquisition step of acquiring a radiographic image including a plurality of pixel values ​​obtained from a plurality of imaging pixels by radiography using a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged; a determining step of determining, from among the plurality of pixel values, pixel values ​​obtained from a first type of imaging pixel of the radiation imaging device and pixel values ​​obtained from a second type of imaging pixel having a configuration different from that of the first type of imaging pixel; a correction step of performing a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performing a second correction process different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, the correction process to be applied to the pixel values ​​to be corrected is determined based on pixel value information obtained from pixel values ​​of a portion of the radiographic image. (Item 20) A program for causing a computer to function as each means of the image processing device described in any one of items 1 to 16.

[0067] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0068] 10: Radiation imaging system, 100: Control device, 101: Radiation pressure control device, 102: Radiation imaging device, 103: Controller, 104: Radiation source interface, 105: Imaging interface, 106: Image processing unit, 107: Display unit

Claims

1. an acquisition means for acquiring a radiographic image including a plurality of pixel values ​​obtained from a plurality of imaging pixels by radiography using a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged; a determining means for determining, from among the plurality of pixel values, pixel values ​​obtained from a first type of imaging pixel of the radiation imaging device and pixel values ​​obtained from a second type of imaging pixel having a configuration different from that of the first type of imaging pixel; a correction unit that performs a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performs a second correction process that is different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, the image processing device determines the correction process to be applied to the pixel values ​​to be corrected based on pixel value information obtained from pixel values ​​of a portion of the radiographic image.

2. 2. The image processing device according to claim 1, wherein the first type of imaging pixel has a configuration in which a single conversion element is arranged in the area of ​​one pixel, and the second type of imaging pixel has a configuration in which two conversion elements capable of independently reading out electric charges are arranged in the area of ​​one pixel, and a pixel value is provided from a first conversion element, which is one of the two conversion elements.

3. the determining means further determines, from the plurality of pixel values, pixel values ​​obtained from a third imaging element included in a third type of imaging pixel having a configuration different from the first type of imaging pixel and the second type of imaging pixel; the correction means performs the second correction process on pixel values ​​obtained from the third type of image sensor; 3. The image processing device according to claim 2, wherein the second correction process determines a correction process to be applied to pixel values ​​from the third type of imaging pixels based on the pixel value information, independently of a correction process to be applied to pixel values ​​from the second type of imaging pixels.

4. 4. The image processing device according to claim 3, wherein the third type imaging pixel has a configuration in which a single conversion element connected to the same drive line as the first conversion element of the second type imaging pixel is arranged in a region of one pixel, and a drive line for a second conversion element, which is the other of the two conversion elements, passes through the region.

5. the first correction process includes offset correction using a dark image and gain correction using a gain image; The image processing device according to claim 1 , wherein the second correction processing is a correction processing determined based on the pixel value information, performed on the pixel values ​​that have been subjected to the offset correction.

6. the first correction process includes offset correction using a dark image and gain correction using a gain image; The image processing device according to claim 1 , wherein the second correction processing is a correction processing determined based on the pixel value information, performed on the pixel values ​​that have been subjected to the offset correction and the gain correction.

7. The image processing device according to claim 5 , wherein the second correction process includes a correction process of adding or subtracting a first correction value determined based on the pixel value information.

8. The image processing device according to claim 5 , wherein the second correction process includes a correction process of multiplying or dividing by a second correction value determined based on the pixel value information.

9. The image processing device according to claim 1 , wherein the second correction processing is determined based on a shooting condition.

10. The image processing device according to claim 9 , wherein the imaging conditions include an irradiation time, a tube voltage, and a tube current set in a radiation generating device used for the radiation imaging.

11. The image processing device according to claim 1 , wherein the second correction processing is determined based on the elapsed time from when the radiation imaging device is powered on or when one radiation imaging session is completed until preparation for the next radiation imaging session is completed.

12. the second correction process uses a correction value obtained by substituting a value determined based on the pixel value information into an approximation formula; The image processing device according to claim 1 , wherein the approximation formula is determined in advance to convert a pixel value obtained from an imaging pixel to be corrected into a correction value that brings the pixel value obtained from the imaging pixel of the first type closer to the pixel value obtained from the imaging pixel of the first type.

13. In the second correction process, a value determined based on the pixel value information and a correction value obtained by referring to a numerical value table are used; 2. The image processing device according to claim 1, wherein the numerical value table holds correspondence between correction values ​​for bringing pixel values ​​obtained from the imaging pixels to be corrected closer to pixel values ​​obtained from the first type of imaging pixels and values ​​determined based on the pixel value information.

14. The image processing device according to claim 1 , wherein the second correction process sets an imaging pixel to be corrected as a defective pixel to be subjected to defect correction based on the pixel value information.

15. 2. The image processing device according to claim 1, wherein the second correction process is determined based on any one of an average value of pixel values ​​obtained from the plurality of imaging pixels of the first type surrounding the imaging pixel to be corrected, a pixel value obtained from the imaging pixel to be corrected, and a ratio between the average value and the pixel value obtained from the imaging pixel to be corrected.

16. 2. The image processing device according to claim 1, wherein the determining means determines whether an imaging pixel providing a pixel value is the first type imaging pixel or the second type imaging pixel based on positions in the radiation image of the plurality of pixel values ​​included in the pixel value information.

17. a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged, the plurality of imaging pixels including a first type imaging pixel having a configuration in which a single conversion element is arranged in the area of ​​one pixel, and a second type imaging pixel having a configuration in which two conversion elements capable of independently reading out electric charges are arranged in the area of ​​one pixel, and a pixel value is provided from one of the two conversion elements; an image processing device that processes a radiographic image including a plurality of pixel values ​​obtained from the plurality of imaging pixels by radiography using the radiographic imaging device, The image processing device includes: a determining means for determining, from among the plurality of pixel values, pixel values ​​obtained from the first type of imaging pixel and pixel values ​​obtained from the second type of imaging pixel; a correction unit that performs a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performs a second correction process that is different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, the correction process to be applied to the pixel value to be corrected is determined based on pixel value information obtained from pixel values ​​of a portion of the radiographic image.

18. 18. The radiation imaging system according to claim 17, wherein the radiation imaging device performs automatic exposure control based on dose information detected from a first conversion element of the two conversion elements, the second conversion element being different from the first conversion element, and a pixel value provided by the first conversion element of the two conversion elements.

19. an acquisition step of acquiring a radiographic image including a plurality of pixel values ​​obtained from a plurality of imaging pixels by radiography using a radiation imaging device in which a plurality of imaging pixels are two-dimensionally arranged; a determining step of determining, from among the plurality of pixel values, pixel values ​​obtained from a first type of imaging pixel of the radiation imaging device and pixel values ​​obtained from a second type of imaging pixel having a configuration different from that of the first type of imaging pixel; a correction step of performing a first correction process on pixel values ​​obtained from the first type of imaging pixels as correction targets, and performing a second correction process different from the first correction process on pixel values ​​obtained from the second type of imaging pixels as correction targets, In the second correction process, a correction process to be applied to the pixel value to be corrected is determined based on pixel value information obtained from pixel values ​​of a portion of the radiographic image.

20. A program for causing a computer to function as each of the means of the image processing device according to any one of claims 1 to 16.

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