JP2016158808A - Image processing apparatus, image processing apparatus control method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the presence or absence of an afterimage more accurately and update an offset image properly.SOLUTION: A memory (18) stores a last X-ray image captured. A CPU (17) obtains, as a dark image, an image captured with no X rays projected after the last X-ray image was captured, determines the presence or absence of an afterimage from the dark image on the basis of pixel values of the last X-ray image and offset image, and determines whether or not to update the offset image according to the determination result about the presence or absence of the after image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing apparatus, a control method for the image processing apparatus, and a program.

  Radiographic imaging apparatuses are widely used in many fields such as medical imaging and industrial nondestructive imaging. Conventionally, a radiographic imaging apparatus using a film has been used for a long time, but in recent years, a radiographic imaging apparatus having a radiation detector called a flat panel detector (hereinafter referred to as FPD) has been used. Widely used. The FPD is configured by arranging a large number of semiconductor elements for converting radiation into electrical signals in a two-dimensional matrix.

  A radiographic imaging apparatus equipped with an FPD accumulates radiation that has passed through a subject as charges in a semiconductor element, and then performs a transfer operation to read out charge information and create digital image information from the charge information. However, it is difficult to read out all of the accumulated charges with a single transfer operation, and a part of the charges may remain after the readout. When image information is read out in a state where a part of this charge remains regardless of the presence or absence of radiation irradiation, a phenomenon in which the remaining charge is superimposed on the acquired image information (hereinafter referred to as an afterimage). It is generally known that happens. Further, this afterimage has a characteristic that it gradually decreases as time elapses or as the charge decreases every time image reading is performed.

  As an example in which the above-mentioned afterimage affects the image quality, there is an overcorrection of an offset correction process using a previous offset image. First, the offset correction process and the previous offset image will be described. The offset correction process refers to a process of removing dark current components generated regardless of radiation when image information is read from the FPD. Here, in general, an image (hereinafter referred to as a dark image) acquired in a state in which no radiation is irradiated is an image based on a dark current component. This dark image becomes a correction image used for the offset correction processing. For this reason, the offset correction process is performed by subtracting a dark image from an image acquired in the state of irradiation with radiation (hereinafter referred to as a radiation image). The pre-offset image refers to a dark image used for offset correction processing acquired before irradiation with radiation, and is mainly used in offset correction processing of a radiographic imaging apparatus or the like whose frame rate is determined.

  However, the offset correction process cannot be performed properly because the amount of dark current changes due to the temperature change of the electronic substrate and the like when the radiographic image acquisition timing and the offset image acquisition timing are separated. For this reason, the radiographic image capturing apparatus obtains a dark image and updates the offset image at a fixed timing that is generally not performed, so that appropriate offset correction is performed. .

  Next, the overcorrection of the offset correction process using the previous offset image will be described. For this overcorrection, a pre-offset image was acquired for radiography (hereinafter referred to as second X-ray imaging) after radiography (hereinafter referred to as first X-ray imaging). Can occur in some cases. More specifically, the first offset X-ray image obtained after the first X-ray imaging and the X-ray image obtained by the second X-ray imaging performed thereafter are respectively the first X-ray imaging. There may be an afterimage. However, the size of the afterimages included in these images is larger for images closer to the acquisition time of the first X-ray imaging and images closer to the timing of image reading. That is, there is a high possibility that the previous offset image closer to the acquisition time of the first X-ray imaging or the image reading timing contains a larger afterimage than the X-ray image obtained by the second X-ray imaging. In such a case, when the offset correction process is performed, subtraction is performed on the X-ray image of the second X-ray imaging with a small afterimage by the previous offset image having a large afterimage. For this reason, in the X-ray image obtained by the second X-ray imaging, the difference due to the afterimage component of the previous offset image enters as an inverse image. This phenomenon is an overcorrection of the previous offset correction process.

  For this reason, techniques such as Patent Document 1 and Patent Document 2 have been proposed to prevent overcorrection. In these patent documents, whether or not a dark image acquired between the first X-ray imaging and the second X-ray imaging is used as a previous offset image is determined based on the presence or absence of the afterimage of the dark image, and the afterimage in the dark image Only when there is no image, the dark image is used as the previous offset image.

JP 2006-305228 A JP 2010-42150 A

  In the conventional afterimage determination method, the afterimage amount is estimated from the statistic of the dark image, the elapsed time after the first X-ray imaging, and the exposure dose. However, since the dark image also changes depending on various factors such as temperature, the conventional afterimage presence / absence determination method cannot clearly distinguish the afterimage components and is difficult to determine with high accuracy. If the presence or absence of an afterimage cannot be accurately determined in this way, the offset image may not be updated properly.

  The present invention has been made in view of such a problem, and is an image processing apparatus and an image processing apparatus control method capable of improving the accuracy of afterimage determination and appropriately updating a correction image. And to provide a program.

  The image processing apparatus of the present invention includes a storage unit that stores a radiographic image captured by irradiating radiation, an acquisition unit that acquires an image captured without radiating radiation as a correction image for the radiographic image, An afterimage that determines the presence or absence of an afterimage of the correction image based on the pixel value of the radiation image stored in the storage unit and the pixel value of the correction image acquired by the acquisition unit It is characterized by comprising presence / absence determination means and update determination means for determining whether or not to update the correction image according to the determination result of the presence / absence of the afterimage by the afterimage presence / absence determination means.

  According to the present invention, it is possible to improve the accuracy of the determination of the presence or absence of an afterimage and appropriately update the correction image.

It is a figure which shows schematic structure of the radiographic imaging apparatus of embodiment. It is a flowchart which shows the flow of the offset image update of 1st Embodiment. It is a flowchart of afterimage presence / absence determination processing (correlation coefficient method). It is a flowchart which shows the flow of the offset image update of 2nd Embodiment. It is a flowchart of afterimage presence / absence determination processing (approximate expression derivation method).

  FIG. 1 shows a schematic configuration of the radiographic image capturing apparatus of the present embodiment. The radiographic image capturing apparatus of the present embodiment is a radiographic image capturing system having an X-ray generating apparatus 10 that is an example of a radiation generating apparatus, an FPD 12, an image processing apparatus 13, a display apparatus 14, and an operating apparatus 15. It is configured. The X-ray generator 10 emits X-rays toward the FPD 12. The subject 1 is placed between the X-ray emitting unit of the X-ray generator 10 and the X-ray detection surface of the FPD 12, and the FPD 12 images the X-rays that have passed through the subject 1 to the image processing device 13. Send. The image processing apparatus 13 includes an I / O unit 16, a CPU 17, a memory 18, a storage medium 19 and the like therein. The I / O unit 16 transmits and receives data to and from the FPD 12 and the X-ray generator 10. The CPU 17 performs operation control of the radiation image capturing apparatus and the image processing apparatus 13 and various arithmetic processes described later. The memory 18 reads and writes programs and data used when the CPU 17 executes calculations. The storage medium 19 records and saves image data and the like. The image processing device 13 is connected to a display device 14 having a monitor screen for displaying processing results, images, and the like, and an operation device 15 for accepting user operations.

<First Embodiment>
Hereinafter, referring to the flowcharts of FIG. 2 and FIG. 3, the acquisition of the offset correction image, the offset correction processing using the offset correction image, and the offset correction image in the radiographic imaging device of the first embodiment are appropriately performed. A determination process for updating will be described. As described above, the offset correction process is a process of subtracting a dark image (offset correction image) captured in a state where no radiation is irradiated from a radiation image captured in a state where the radiation is irradiated. Although details will be described later, the determination processing in the present embodiment is processing including afterimage presence determination processing and update determination processing. As described later, the afterimage presence / absence determination process calculates a feature amount indicating a relationship between each pixel of the latest radiographic image and each pixel of the dark image acquired after capturing the radiographic image, and the feature amount Is a process for determining the presence or absence of an afterimage of a dark image based on the above. The update determination process is a process for determining whether or not to update the dark image as an offset correction image in accordance with the determination result of the afterimage presence / absence determination process. 2 and 3 is a process performed when the CPU 17 of the image processing apparatus 13 executes a program loaded in the memory 18.

  In the flowchart of FIG. 2, the CPU 17 of the image processing apparatus 13 first performs an offset correction image as a process in step S <b> 101 after the radiation image capturing apparatus is activated and before the radiation image of the subject 1 is captured. Perform initial settings for. Hereinafter, the offset correction image is simply referred to as an offset image. Specifically, in step S101, the CPU 17 acquires dark image data by causing the FPD 12 to capture an image without generating X-rays from the X-ray generation device 10, and uses the dark image as an initial offset image. Set to. The initial offset image may be a dark image acquired in advance and stored in the memory 18 or the storage medium 19. In this case, the CPU 17 uses the previously acquired dark image as the initial offset image in step S101. To do. Note that the CPU 17 may set the dark image acquired for one sheet as it is as the initial offset image. Alternatively, the CPU 17 may acquire a plurality of dark images, generate one dark image from the plurality of dark images, and set it as an initial offset image. Specifically, the CPU 17 obtains an average of each pixel having the same coordinates for a plurality of dark images, and generates one dark image in which the average values obtained for each pixel are arranged at corresponding coordinates. Then, it may be set as an initial offset image. Alternatively, the CPU 17 obtains the median value of the pixel values of the same coordinates of a plurality of dark images, and creates a dark image for one sheet in which the median values obtained for each pixel are arranged at corresponding coordinates. It may be set as an initial offset image. As described above, a dark image created by obtaining an average value or a median value from a plurality of dark images is more likely to have less noise than when only one dark image is acquired. After step S101, the CPU 17 advances the process to step S102.

  In step S <b> 102, the CPU 17 causes the X-ray generator 10 to irradiate the FPD 12 with X-rays and causes the FPD 12 to perform X-ray imaging. At this time, the subject 1 is placed between the X-ray emitting unit of the X-ray generation device 10 and the X-ray detection surface of the FPD 12, and thus the FPD 12 captures X-rays transmitted through the subject 1. After step S102, the CPU 17 advances the process to step S103.

  In step S103, the CPU 17 performs an offset correction process using an offset image on the X-ray image obtained by the X-ray imaging in step S102. After step S103, the CPU 17 advances the process to step S104.

  In step S104, the CPU 17 performs display image processing on the image data after the offset correction processing in step S103. Specifically, the display image processing in step S104 can use processing by a known technique such as gain correction processing, gradation processing, and frequency enhancement processing. Then, as the processing of step S105, the CPU 17 sends the image data after the display image processing of step S104 to the display device 14 and displays it on the monitor screen of the display device 14. After step S104, the CPU 17 advances the process to step S106.

  In step S <b> 106, the CPU 17 determines whether an instruction to continuously perform X-ray imaging such as a fluoroscopic image (moving image) is input from the operation device 15 by a user operation. If the CPU 17 determines in step S106 that an instruction to perform continuous X-ray imaging is input, the process returns to step S102. Thereby, the processing from the X-ray imaging (X-ray image acquisition) in step S102 to the image display in step S105 is continued. On the other hand, when an instruction to end continuous X-ray imaging is input, the CPU 17 advances the process from step S106 to step S107.

  In step S107, the CPU 17 stores the latest X-ray image at the present time, that is, the data of the last taken X-ray image (hereinafter referred to as the final X-ray image) in the storage medium 19, and the final X-ray. Perform image storage processing. However, the final X-ray image at this time is the X-ray image after the offset correction processing in step S103. After step S107, the CPU 17 advances the process to step S108.

  In step S <b> 108, the CPU 17 acquires dark image data by causing the FPD 12 to capture an image without generating X-rays from the X-ray generator 10. In addition, when acquiring the dark image in step S108, as described above, one dark image may be created by obtaining an average value or a median value from a plurality of dark images. After step S108, the CPU 17 advances the process to step S109.

  In step S109, the CPU 17 performs afterimage determination processing using the final X-ray image data stored in step S107 and the dark image data acquired in step S108. Details of the afterimage presence / absence determination process in step S109 will be described later. If the CPU 17 determines that there is an afterimage in the dark image data as a result of the afterimage determination process in step S109, the process proceeds to step S111. On the other hand, when it determines with there being no afterimage in step S109, CPU17 advances a process to step S110.

  When it is determined in step S109 that there is no afterimage and the process proceeds to step S110, the CPU 17 performs an offset image update process for updating the offset image using the dark image acquired in step S108 as a new offset image. After step S110, the CPU 17 advances the process to step S111.

  In step S <b> 111, the CPU 17 determines whether an instruction to start X-ray imaging is input from the operation device 15 by a user operation. If the CPU 17 determines in step S111 that an instruction to start X-ray imaging has been input, the process returns to step S102. Thereby, the processing from the X-ray imaging (X-ray image acquisition) in step S102 to the offset image update in step S110 is performed. Here, when it is determined in step S109 that there is no afterimage and the update by the new offset image is performed in step S110, the offset correction process in step S103 is performed using the updated new offset image. Become. On the other hand, if it is determined in step S109 that there is an afterimage and the offset image has not been updated, the offset correction processing in step S103 is performed using the same offset image as that used last time. If it is determined in step S111 that an instruction to start X-ray imaging has not been input, the CPU 17 advances the process to step S112.

  In step S112, the CPU 17 determines whether an input for ending the examination by X-ray imaging or an instruction to stop the apparatus is input from the operation device 15 by the user's operation. If the instruction to end the inspection or stop the apparatus is not input in step S112, the CPU 17 returns the process to step S108. As a result, the processing after the dark image acquisition processing in step S108 is performed until it is determined in step S111 that an instruction to start the next X-ray imaging is input. That is, in the case where an instruction to end the inspection or stop the apparatus is not input in step 112, the CPU 17 does not update with a new offset image in step S110 while it is determined in step S109 that there is an afterimage, for example. . If the instruction to end the inspection or stop the apparatus is not input in step 112, the CPU 17 updates the image with a new offset image in step S110 if it is determined in step S109 that there is no afterimage. As a result, for example, when an instruction to start X-ray imaging is subsequently input in step S111, an offset correction process using an offset image with no afterimage is performed in step S103. On the other hand, if it is determined in step S112 that the inspection end or apparatus stop instruction has been input, the CPU 17 ends the processing of the flowchart of FIG.

  Next, details of the afterimage presence / absence determination process performed in step S109 will be described with reference to the flowchart of FIG. In FIG. 3, a correlation coefficient is calculated as a feature amount indicating the relationship between each pixel of the latest radiation image (final X-ray image) and each pixel of the dark image, and the correlation coefficient is used as a criterion. It is a flowchart of the process which performs afterimage presence determination. When proceeding to the afterimage presence / absence determination process, first, in step S201, the CPU 17 performs an offset correction process using an offset image on the dark image acquired in step S108 of FIG. After step S201, the CPU 17 advances the process to step S202.

  In step S202, the CPU 17 performs a saturated pixel value determination process on the final X-ray image stored in the final X-ray image storage process of step S107 in FIG. Specifically, in the saturated pixel value determination process, the representative value of the saturated pixel value of the FPD 12 is investigated in advance, and is determined as a saturated pixel value when each pixel of the final X-ray image exceeds the representative value. Such a process can be used. After step S202, the CPU 17 advances the process to step S203.

  In step S203, the CPU 17 performs saturated pixel value exclusion processing in order to exclude saturated pixels in the correlation coefficient derivation processing performed in later step S204. The saturated pixel value exclusion process is a process of determining pixel values to be excluded in a correlation coefficient derivation process performed later using, for example, a flag map image having the same size as the image size of the FPD 12. The flag map image is an image in which each pixel is arranged corresponding to the two-dimensional coordinates of each semiconductor element of the FPD 12 (two-dimensional coordinates of each pixel of the final X-ray image). In the flag map image, “1” is stored in the pixel value of the pixel corresponding to the saturation pixel of the final X-ray image, and “0” is stored in the pixel value of the other pixels. Among the pixel values of the final X-ray image, the pixel values corresponding to the pixel coordinates in which “1” is stored as the pixel value in the flag map image are the pixel values to be excluded in the correlation coefficient derivation process. . That is, in the correlation coefficient derivation process described later, by referring to this flag map image, among the pixels of the final X-ray image, the pixel value in the flag map image corresponds to the pixel coordinate of “1”. The obtained pixel value is excluded from the calculation. In other words, among the pixels of the final X-ray image and the pixels of the dark image, only the pixel values corresponding to the pixel coordinates with the pixel value “0” in the flag map image are subjected to the correlation coefficient derivation process described later. It will be used for calculation. After step S203, the CPU 17 advances the process to step S204.

  In step S204, the CPU 17 performs a correlation coefficient derivation process using the flag map image created in the saturated pixel value exclusion process in step S203, the final X-ray image, and the dark image after the offset correction process. The correlation coefficient deriving process is a process of calculating a correlation coefficient using the calculation formula (1) as a feature amount indicating the relationship between each pixel of the final X-ray image and each pixel of the dark image. However, among the pixels of the final X-ray image and the pixels of the dark image, the pixel value of each pixel determined to be a saturated pixel value in the flag map image is excluded from this calculation.

In Equation (1), r is a correlation coefficient, (x, y) indicates the coordinates of the X axis and the Y axis of the image, and V _Dark (x, y) is (x, y) of the dark image after offset correction. y) The pixel value of the coordinate, V _Xray (x, y) represents the pixel value of the (x, y) coordinate of the final X-ray image. After step S204, the CPU 17 advances the process to step S205.

  In step S205, the CPU 17 performs afterimage presence / absence threshold determination processing based on the correlation coefficient obtained in step S204. Here, an element with a high correlation is an afterimage component, and an element with a low correlation is considered a noise component. For this reason, the CPU 17 determines that the afterimage component is acceptable if it is approximately the same as the noise component. For example, if “0.5” is used as the threshold value of the correlation coefficient that can be determined to be comparable to the noise component, the CPU 17 determines that there is an afterimage if the correlation coefficient value is 0.5 or more. If it is less than 0.5, it is determined that there is no afterimage. If it is determined that there is an afterimage, the CPU 17 proceeds to step S113 in FIG. 2, while if it is determined that there is no afterimage, the process proceeds to step S110 in FIG.

  In the case of the first embodiment, the CPU 17 uses the correlation coefficient as a determination criterion in the afterimage presence / absence determination process in step S109 of FIG. 2, but obtains an approximate expression described later with reference to FIG. An evaluation coefficient for an error from the equation may be used as a criterion.

<Second Embodiment>
In the second embodiment, the after-image presence / absence determination of the acquired dark image is performed, and whether or not the after-image correction process of the offset correction image is necessary is determined based on the presence / absence of the after-image. Hereinafter, with reference to the flowcharts of FIGS. 4 and 5, determination as to whether or not the afterimage correction process of the offset correction image in the second embodiment is necessary will be described. In the flowcharts of FIGS. 4 and 5, the same processes as those in the flowcharts of FIGS. 2 and 3 described above are denoted by the same instruction numbers, and description of these processes is omitted. The processing in the flowcharts of FIGS. 4 and 5 is processing performed by the CPU 17 of the image processing apparatus 13 executing a program loaded in the memory 18.

  In the flowchart of FIG. 4, steps S101 to S108 are the same as steps S101 to S108 of the flowchart of FIG. After the dark image acquisition process in step S108, the CPU 17 advances the process to step S109. In step S109, the CPU 17 performs afterimage presence / absence determination processing. The afterimage presence / absence determination processing may be a method using the correlation coefficient as described above with reference to FIG. 3, but in the second embodiment, the approximate expression of FIG. 5 is derived and an error from the approximate expression is calculated. An evaluation coefficient is used as a criterion.

  The details of the afterimage presence / absence determination process using the evaluation coefficient of the error from the approximate expression as a determination criterion will be described below with reference to the flowchart of FIG. This FIG. 5 calculates an evaluation coefficient of an error from the approximate expression as a feature amount indicating the relationship between each pixel of the latest radiation image (final X-ray image) and each pixel of the dark image, and the evaluation It is a flowchart of the process which performs the afterimage presence determination using a coefficient as a determination criterion. In the flowchart of FIG. 5, steps S201 to S203 are the same as steps S201 to S203 of the flowchart of FIG. After the saturated pixel exclusion process in step S203, the CPU 17 advances the process to step S206.

In step S206, the CPU 17 performs an approximate expression creation process using the flag map image created by the saturated pixel exclusion process, the final X-ray image, and the dark image after the offset correction. Here, since the afterimage is proportional to the input X-ray dose, the approximate expression creation process is specifically a process of calculating the afterimage coefficient T and the linear component D by the least square method with respect to the linear expression of Expression (2). Become. However, as described above, pixel values that are saturated pixel values in the flag map image are excluded from the calculation. Note that (x, y), V _Dark (x, y), and V _Xray (x, y) in equation (2) are the same as in equation (1).

After the approximate expression creating process in step S206, the CPU 17 advances the process to step S207. In step S207, the CPU 17 performs an approximate error derivation process using the approximate expression obtained by the approximate expression creation process in step S206. More specifically, the approximate error derivation process is a process of calculating the determination coefficient R ² as an evaluation coefficient of an error from the approximate expression using Expression (3). F (x, y) in the equation (3) indicates the pixel value of the dark image approximated by the equation (4).

After the approximation error derivation process in step S207, the CPU 17 advances the process to step S208. In step S <b> 208, the CPU 17 performs afterimage presence / absence threshold determination processing using the result of the approximate error derivation processing. Here, the element that increases the determination coefficient R ² is an afterimage component, and the element that decreases the determination coefficient is a noise component. For this reason, the CPU 17 determines that the afterimage component is acceptable if it is approximately the same as the noise component. For example, assuming that “0.25” is used as the threshold value of the determination coefficient R ^{2 that} can be determined to be approximately the same as the noise component, the CPU 17 determines that there is an afterimage if the value of the determination coefficient R ² is 0.25 or more. If it is less than 0.25, it is determined that there is no afterimage.

  Returning to the flowchart of FIG. 4, when it is determined that there is an afterimage in the afterimage presence / absence determination process in step S <b> 109, the CPU 17 advances the process to step S <b> 113. In step S113, the CPU 17 performs afterimage correction processing on the dark image acquired in the dark image acquisition processing in step S108. Specifically, the CPU 17 preliminarily calculates the pixel value of the final X-ray image, the time from acquisition of the final X-ray image to acquisition of the dark image, and the amount of afterimage remaining in the dark image before performing the afterimage correction process. Ask for a relationship. Then, the CPU 17 estimates the afterimage amount based on the time from acquisition of the final X-ray image to acquisition of the dark image, and subtracts the estimated afterimage amount from the amount of afterimage remaining in the dark image.

  After step S208, the CPU 17 advances the process to step S110 in FIG. Step S110 and subsequent steps are the same as those in the flowchart of FIG.

  As described above, according to the radiographic imaging device of the present embodiment, the presence or absence of the afterimage of the acquired dark image indicates the relationship between each pixel value of the final X image and each pixel value of the dark image. By estimating based on the quantity, it can be determined with high accuracy. Therefore, according to this embodiment, it is possible to appropriately update the offset image.

<Other embodiments>
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  DESCRIPTION OF SYMBOLS 10 X-ray generator, 12 FPD, 13 Image processing apparatus, 14 Display apparatus, 15 Operation apparatus, 16 I / O part, 17 CPU, 18 Memory, 19 Storage medium

Claims (8)

Storage means for storing a radiation image taken by irradiating radiation;
An acquisition means for acquiring an image captured in a state in which radiation is not irradiated as a correction image for the radiation image;
An afterimage that determines the presence or absence of an afterimage of the correction image based on the pixel value of the radiation image stored in the storage unit and the pixel value of the correction image acquired by the acquisition unit Presence / absence judging means;
An image processing apparatus comprising: an update determination unit that determines whether or not to update the correction image according to a determination result of the presence or absence of an afterimage by the afterimage presence / absence determination unit. The storage means stores the latest radiation image taken by irradiating with radiation,
The afterimage presence / absence determining means calculates a feature amount indicating a relationship between a pixel value of the latest radiation image and the correction pixel value, and determines the presence or absence of the afterimage based on the feature amount. The image processing apparatus according to claim 1.   The afterimage presence / absence determining means calculates a correlation coefficient between a pixel value of the latest radiation image and a pixel value of the correction image as the feature amount, and determines the presence / absence of the afterimage using the correlation coefficient. The image processing apparatus according to claim 2.   The afterimage presence / absence determining means calculates an evaluation coefficient of an approximation error between the pixel value of the latest radiation image and the pixel value of the correction image as the feature amount, and determines the presence or absence of the afterimage using the evaluation coefficient The image processing apparatus according to claim 2, wherein:   The afterimage presence / absence determining means determines a pixel value that is not saturated among the pixel values of the latest radiation image, and determines the presence or absence of the afterimage using only the pixel values that are not saturated. The image processing apparatus according to claim 3, wherein the image processing apparatus is an image processing apparatus. A control method of an image processing apparatus that performs correction processing of a radiographic image captured by irradiating with radiation,
A storage step for storing a radiation image taken by irradiating radiation;
An acquisition step of acquiring an image captured in a state in which radiation is not irradiated as a correction image for the radiation image;
An afterimage that determines the presence or absence of an afterimage of the correction image based on the pixel value of the radiographic image stored in the storage step and the pixel value of the correction image acquired in the acquisition step Presence / absence determination step;
A control method for an image processing apparatus, comprising: an update determination step for determining whether or not to update a correction image according to a determination result of the presence or absence of an afterimage in the afterimage presence / absence determination step. Computer
Storage means for storing a radiation image taken by irradiating radiation;
An acquisition means for acquiring an image captured in a state in which radiation is not irradiated as a correction image for the radiation image;
An afterimage that determines the presence or absence of an afterimage of the correction image based on the pixel value of the radiation image stored in the storage unit and the pixel value of the correction image acquired by the acquisition unit Presence / absence judging means;
A program for functioning as an update determination unit for determining whether or not to update a correction image according to a determination result of the presence or absence of an afterimage by the afterimage presence / absence determination unit. A radiation generator for emitting radiation;
An imaging device for capturing a radiation image by detecting radiation emitted from the radiation generation device;
The correction process using the image for correction is performed on the radiographic image captured by the imaging apparatus detecting the radiation emitted from the radiation generation apparatus. A radiographic imaging system comprising: an image processing apparatus.

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