JP2018114174A - Radiographic apparatus, radiographic system, radiographic method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiographic apparatus capable of performing appropriate afterimage correction according to a change in a radiographic condition.SOLUTION: A radiographic apparatus of the present invention is a radiographic apparatus for performing radiography based on an imaging condition of the radiography, and includes detection means for detecting an irradiated radiation and outputting radiation image data, calculation means for setting a threshold on the imaging condition, and, based on the threshold, calculating afterimage characteristics indicating characteristics of an afterimage in the radiation image data, and correction means for correcting the radiation image data based on the afterimage calculated by the afterimage characteristics.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radiation imaging apparatus, a radiation imaging system, a radiation imaging method, and a program.

  2. Description of the Related Art In recent years, radiation imaging apparatuses that take a radiographic image by arranging solid-state imaging elements made of amorphous silicon or single crystal silicon in a two-dimensional manner have been widely put into practical use.

  In such a radiographic apparatus, an afterimage may occur when radiation enters. In this case, since an afterimage component is added to the image data captured by the radiation imaging apparatus and output, image information inappropriate for the radiation imaging conditions is acquired.

  Therefore, in order to remove the generated afterimage, image correction processing is performed using image information (offset data) based on the offset signal. The offset data is image data output from the radiation imaging apparatus when no radiation is incident, and is referred to as a dark image.

  However, the afterimage has the property that the amount of afterimage attenuates with time. For this reason, a technique for correcting an image by estimating an afterimage amount that changes with time has been proposed.

US Pat. No. 5,249,123 Japanese Patent No. 4464612

  In Patent Document 1 and Patent Document 2, it is assumed that the afterimage included in the radiation detection signal is caused by an impulse response in which the afterimage component is composed of a plurality of exponential functions, and the afterimage is removed from the radiation detection signal by recursive calculation processing. The technology to do is proposed.

  However, the afterimage has a problem that when imaging conditions of radiography change (especially, when the number of times of continuous irradiation of radiation changes), the attenuation characteristic changes greatly and it becomes difficult to correct the afterimage.

  A radiographic apparatus according to the present invention is a radiographic apparatus that performs the radiographic imaging based on radiographic imaging conditions, the detecting means for detecting irradiated radiation and outputting radiographic image data, and the imaging A threshold value for a condition is set, a calculation means for calculating an afterimage characteristic representing the afterimage characteristic in the radiation image data based on the threshold value, and the radiographic image data based on the afterimage calculated by the afterimage characteristic. Correction means for correcting.

  ADVANTAGE OF THE INVENTION According to this invention, the suitable afterimage correction according to the change of the imaging conditions of radiography can be performed.

It is a figure which shows an example of a structure of the radiography apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of a structure of the afterimage correction part which concerns on the 1st Embodiment of this invention. It is a flowchart which shows an example of a process of the radiography apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the time change of the dark image after the radiation irradiation 1 time which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the effect of the implementation which concerns on the 1st Embodiment of this invention.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the following, as an embodiment of the present invention, an embodiment in which the changing radiation imaging condition is the number of continuous irradiations of radiation will be described. Note that the present invention is also applicable when other radiographic conditions (for example, radiation exposure dose, sensor temperature, etc.) change. The radiation in this embodiment is, for example, X-rays.

(First embodiment)

  A first embodiment of the present invention will be described. FIG. 1 is a diagram illustrating a configuration of a radiation imaging apparatus 100 according to the present embodiment. The radiographic apparatus 100 according to the present embodiment is mainly used for medical purposes, and performs radiographic imaging based on radiographic imaging conditions.

  In FIG. 1, a radiation irradiation unit 101 irradiates a subject with radiation. The radiation detection unit 102 detects radiation incident through the subject and generates radiation image data. The tube control unit 103 controls the radiation irradiation dose irradiated from the radiation irradiation unit 101. The imaging condition setting unit 104 sets radiographic imaging conditions such as the number of continuous irradiations of radiation irradiated to the subject, the radiation irradiation dose, and the frame rate in accordance with the operation of the operator. The detector control unit 105 controls the radiation detection unit 102 and the tube control unit 103 based on the signal output from the imaging condition setting unit 104.

  The data collection unit 106 holds the radiation image data acquired by the radiation detection unit 102. The radiographic image data acquired by the radiation detection unit 102 includes an afterimage. The afterimage correction unit (correction unit) 107 removes the afterimage from the radiation image data (radiation image data including the afterimage acquired by the radiation detection unit 102) held in the data collection unit 106. An afterimage correction unit (correction unit) 107 corrects the radiation image data based on the afterimage calculated from the afterimage characteristics. The image display unit 108 outputs the radiographic image data subjected to the afterimage correction by the afterimage correction unit 107 to a monitor or the like.

  Next, the afterimage correction unit 107 according to the present embodiment will be described in detail. FIG. 2 is a diagram showing an example of the configuration of the afterimage correction unit 107 in detail.

  The memory unit 201 stores data used for afterimage correction (hereinafter referred to as “afterimage characteristic data”) generated based on image data captured by the radiation detection unit 102 in a state where no radiation is irradiated. The afterimage characteristic data is represented by a combination bn (k) × exp (−an) of an and bn in the equation (1). an is the time constant or decay rate of the afterimage. bn is the ratio or intensity of the afterimage. In the equation (1), the afterimage characteristic data has a characteristic that the ratio or intensity bn of the afterimage changes for each radiographing depending on k.

A (x, k) = bn (k) × exp (−an) × S (x, k) (1)

  Here, k is the radiation image data of the kth radiation imaging (that is, the number of imaging frames is the kth frame or the number of radiation irradiations is the kth), and x is a predetermined pixel (for example, pixel number x). It is. A (x, k) is an afterimage amount at the pixel x of the k-th radiation image data. An and bn are obtained, for example, by fitting the following equation (2) to a falling step response function (FSRF: Falling Step-Response Function) in a signal output from the radiation detection unit 102 when radiation is irradiated. be able to.

FSRF (k) = Σ {bn} × exp (−an · k) × (1-exp (−an · Nf)) × u (k) / (1-exp (−an)) ( 2)

  Here, Nf is the number of times of radiation irradiation. u (k) is a discrete unit step function.

  S (x, k) is image information derived from previously acquired radiation image data, and is image information including the previous radiation image data subjected to afterimage correction. S (x, k) is calculated by equation (3). Hereinafter, S (x, k) is referred to as “S value” or “S”. For example, the S value is a value in which the information of the previous frame is stored, and is updated for each shooting by Expression (3). The initial value S (x, 1) of the S value is set to 0 or a predetermined value.

S (x, k) = IC (x, k-1) + exp (-an) * S (x, k-1) (3)

  Here, IC (x, k-1) is the radiographic image data after the afterimage correction at the pixel number x of the (k-1) th frame (kth radiographic image data), and is represented by the following equation (4). The I (x, k-1) is radiation image data before afterimage correction at pixel number x in the (k-1) th frame (k-1th radiation image data).

IC (x, k-1) = I (x, k-1) -A (x, k-1) (4)

  The frame information acquisition unit 202 acquires and holds the S value in the current frame from the radiographic image data after the afterimage correction in the previous frame and the S value in the previous frame.

  An afterimage estimation unit (calculation unit) 203 uses an afterimage characteristic data selected from the memory unit 201 based on radiation imaging conditions and the like and an S value in the current frame held by the frame information acquisition unit 202. Estimate the amount. The afterimage estimation unit (calculation unit) 203 sets a threshold value related to the imaging condition, and calculates an afterimage characteristic representing the afterimage characteristic in the radiation image data based on the threshold value. The calculation unit 204 subtracts the afterimage amount estimated by the afterimage estimation unit 203 from the radiation image data including the afterimage acquired by the radiation detection unit 102. The computing unit 204 corrects the radiation image data based on the afterimage calculated from the afterimage characteristics.

  Next, with reference to FIG. 3, a process from photographing of a subject to displaying of radiation image data will be described. Here, the radiographic condition to be changed during radiographing is the number of times of radiation irradiation (the number of continuous irradiations) within a predetermined time. The number of continuous irradiations corresponds to the number of radiographic image data imaging within a predetermined time and the number of radiographic image data imaging frames within a predetermined time. In this case, the parameter of the imaging condition is the number of times of radiation irradiation (number of continuous irradiations) k. The number of irradiation times k corresponds to the number of imaging and the number of imaging frames.

  FIG. 3 illustrates an embodiment in which a threshold k ′ is provided for the continuous irradiation frequency k, and the correction method changes before and after the threshold.

  The threshold value k ′ is determined by the afterimage artifact attenuation characteristics in the radiation detection unit 102. In the case where the threshold value k ′ is provided for the number of continuous irradiations of radiation, for example, it can be determined from the output of a dark image after one irradiation of radiation. A dark image is image data output from the radiation imaging apparatus 100 when no radiation is incident.

  FIG. 4 is a diagram illustrating a change over time in the output of the dark image after one irradiation with radiation. As shown in FIG. 4, it can be seen that the afterimage amount is sufficiently attenuated when the number of continuous irradiations is around the 10th time. That is, the afterimage amount due to the n-10th irradiation is sufficiently attenuated when the nth irradiation is performed, and can be considered to be substantially zero. Similarly, at the time of the n-th irradiation, the afterimage amount due to the irradiation before the n-10th irradiation is sufficiently attenuated and can be considered to be substantially zero.

  Therefore, assuming that the afterimage amount due to the n-th irradiation is the accumulation of the afterimage amount from the first time, the afterimage amount from the first time to the n-10th time is substantially 0, so the nth time Is estimated to be an accumulation of the afterimage amount from the n-9th time to the (n-1) th time.

  That is, the cumulative value of the afterimage amount due to the first to ninth irradiation of radiation changes, but the afterimage amount after 10th time (specifically, the ratio or intensity of the afterimage) is estimated to be substantially constant.

  In this case, it is determined that the threshold value k ′ of the number of continuous irradiations of radiation is 10, and it can be estimated that the ratio or intensity of the afterimage is substantially constant in radiation imaging after the threshold value k ′. That is, the afterimage characteristic data has a characteristic that the ratio or intensity of the afterimage is substantially constant regardless of the number of irradiations.

  Note that the threshold value k ′ may be determined based on an afterimage attenuation amount or an attenuation rate. For example, in FIG. 4, it is assumed that the afterimage is sufficiently attenuated when the attenuation amount becomes a predetermined value (preferably 0.03%), and the number of continuous irradiations of radiation corresponding to the predetermined value of the attenuation amount ( Alternatively, the number of frames taken) may be set as the threshold value k ′.

  In the present embodiment, an example in which the threshold value k ′ is determined from dark image information has been described. However, the threshold value k ′ can also be determined from other information in which the afterimage amount attenuation characteristics are known. In the present embodiment, the threshold value k ′ is a threshold value of the number of continuous irradiations of radiation (or the number of imaging frames) k, but may be a threshold value of time until the afterimage amount due to irradiation of radiation is sufficiently attenuated. Good. In this case, the continuous irradiation time of radiation is used for k instead of the number of continuous irradiations of radiation (or the number of imaging frames).

  In step S <b> 101, the imaging condition setting unit 104 sets radiation imaging conditions at the time of imaging of the subject, such as an imaging mode, a radiation exposure dose, and a tube voltage of the radiation irradiation unit 101, according to an operation of the operator. The set radiation imaging conditions are output to the detector control unit 105.

  In step S102, the number of continuous irradiations of radiation (or the number of imaging frames) k is set to zero. In step S103, the detector control unit 105 outputs a dose control signal to the tube control unit 103 based on the radiographic conditions set in step S101. The tube control unit 103 outputs a radiation signal to the radiation irradiation unit 101 based on the dose control signal. The radiation irradiation unit 101 receives the radiation irradiation signal and irradiates the subject with radiation.

  In step S104, 1 is added (incremented) to the number of times of continuous irradiation of radiation (or the number of imaging frames) k. In step S105, the detector control unit 105 outputs an image data acquisition signal to the radiation detection unit 102 based on the radiation imaging conditions set in step S101. The radiation detection unit 102 acquires the radiation image data y (k) captured based on the radiation imaging conditions set in step S101.

  In step S106, it is determined whether or not the number of continuous irradiations of radiation (or the number of imaging frames) k is equal to or greater than a preset threshold value k '.

  In step S106, if it is equal to or greater than the threshold value k ', the afterimage characteristic data is determined to be LagCcont (step S107-2). If it is equal to or less than the threshold value k ′, the afterimage characteristic data LagC (k) is selected from the memory unit 201 (step S107-1). However, LagC (k ′) and LagCcont are the same value. Here, LagC is a combination bn × exp (−an) of an and bn in the above formula (1).

  In step S108, the afterimage characteristic data selected or determined in step S107 is output to the afterimage estimation unit 203, and an afterimage amount that changes as the frame time elapses is estimated.

  The afterimage amount is estimated in the following cases according to the number of frames that is the threshold value k ′.

  Case 1 (when the number of frames k is less than the threshold k ′): k <k ′

  Case 2 (when the number of frames k is greater than or equal to the threshold k ′): k ≧ k ′

  In case 1 where the number of frames is less than the threshold, the afterimage amount is estimated using the above equation (1). In case 2 where the number of frames k is equal to or greater than the threshold value k ′, the afterimage amount is estimated using equation (5).

A (x, k) = bn (k ′) × exp (−an) × S (x, k) (5)

  Here, S (x, k) is updated by the frame information acquisition unit 202 using the above equation (3). The afterimage characteristic data is represented by a combination of an and bn in Expression (5) bn (k ′) × exp (−an). In equation (5), the afterimage characteristic data has a characteristic that the ratio or intensity of the afterimage is substantially constant regardless of the parameters.

  In step S109, the afterimage amount estimated in step S108 is output to the calculation unit 204, and afterimage correction is performed using the information. In the calculation unit 204, calculation is performed to subtract the afterimage amount estimated by the afterimage estimation unit 203 from the image data before afterimage correction held in the data collection unit 106. Further, Expression (6) is used for the calculation.

IC (x, k) = I (x, k) −A (x, k) (6)

  Here, I (x, k) is the radiation image data before afterimage correction held in the data collection unit 106 at the pixel number x of the kth frame (kth radiation image data).

  In step S110, the image display unit 108 displays the radiation image data x (k) corrected in the afterimage in step S109. In step S111, it is determined whether radiation is continuously exposed. When radiation is continuously exposed, the process returns to step S104. If there is no radiation exposure, the imaging is completed and the flow is completed.

  Next, the case where the frequency | count of continuous irradiation of a radiation is 100 times is demonstrated more concretely.

  The afterimage characteristic data representing the afterimage attenuation characteristic changes with respect to the number of continuous irradiations k of radiation. A case where the threshold value k ′ of the change is around 10 continuous irradiations of radiation will be described.

  In step S <b> 101, the imaging condition setting unit 104 sets radiation imaging conditions at the time of subject imaging such as an imaging mode, a radiation irradiation dose, and a tube voltage of the radiation irradiation unit 101 in accordance with an operation of the operator. The set radiation imaging conditions are output to the detector control unit 105. In step S102, the number of continuous irradiations of radiation (or the number of imaging frames) k is set to zero.

  In step S103, the detector control unit 105 outputs a dose control signal to the tube control unit 103 based on the radiographic conditions set in step S101. The tube control unit 103 outputs a radiation signal to the radiation irradiation unit 101 based on the dose control signal. The radiation irradiation unit 101 receives the radiation irradiation signal and irradiates the subject with radiation.

  In step S104, 1 is added to the number of continuous irradiations of radiation (or the number of imaging frames) k. In step S105, the detector control unit 105 outputs an image data acquisition signal to the radiation detection unit 102 based on the radiation imaging conditions set in step S101. The radiation detection unit 102 acquires the radiation image data y (k) captured based on the radiation imaging conditions set in step S101.

  In step S106, it is determined whether or not the number of continuous irradiations (or the number of imaging frames) k is equal to or more than a preset threshold value 10 times.

  In step S107, when the number of continuous irradiations of radiation (or the number of imaging frames) k is between 1 and 10, the afterimage characteristic data is set to the number of continuous irradiations of radiation (or the number of imaging frames) k. Accordingly, the memory unit 201 is selected. That is, the afterimage characteristic data changes according to the number of continuous irradiations of radiation (or the number of imaging frames) k. For this reason, it is necessary to store afterimage characteristic data of k ′ = 10 patterns in the memory unit 201.

  In step S107, when the number of continuous irradiations (or the number of imaging frames) k is 10 or more, the afterimage characteristic data is fixed to a value of 10 continuous irradiations. That is, after image irradiation 10 times or more, afterimage correction is performed using the same afterimage characteristic data.

  In step S108, the afterimage characteristic data selected or determined in step S107 is output to the afterimage estimation unit 203, and an afterimage amount that changes as the frame time elapses is estimated. In step S109, the afterimage amount estimated in step S108 is output to the calculation unit 204, and afterimage correction is performed using the information. In step S110, the image display unit 108 displays the radiation image data x (k) corrected in the afterimage in step S109.

  In step S111, it is determined whether radiation is continuously exposed. When radiation is continuously exposed, the process returns to step S104. When the radiation exposure reaches 100 times, the imaging is finished and the flow is completed.

  The result of applying this embodiment is shown in FIG. As shown in FIG. 5, the effect of afterimage correction is also exhibited when Patent Document 1 is applied to the afterimage attenuation before correction. However, the afterimage in the initial frame is sufficiently corrected. You can see that it is not broken.

  On the other hand, when this embodiment is applied, the afterimage in the initial frame can be sufficiently corrected, and a sufficient correction result appears compared to Patent Document 1.

  The imaging conditions may be an imaging frame rate of radiation image data, an imaging time of radiation image data, and an irradiation time of radiation.

  In the present embodiment, the present invention is applicable when the imaging condition is at least one of the number of radiographic image data imaging, the number of radiographic image data imaging frames, the imaging time, and the number of times of radiation irradiation. Explained. In this case, in an area where the imaging condition parameter k is less than or less than the threshold, an afterimage is calculated based on an afterimage characteristic in which the ratio or intensity of the afterimage changes with each radiography. Further, in an area where the parameter k of the shooting condition is greater than or equal to the threshold value or greater than the threshold value, the afterimage is calculated by the afterimage characteristic in which the ratio or intensity of the afterimage is substantially constant regardless of the shooting condition.

(Second Embodiment)

  In the second embodiment, a description will be given of a method of setting a threshold for the radiation exposure dose and changing the correction method before and after the threshold when the radiation imaging condition that changes during imaging is a radiation exposure dose.

  If the sensor output and the radiation exposure dose are proportional, assuming that the sensor output and the afterimage amount are proportional, the ratio or intensity of the afterimage relative to the sensor output is estimated to be approximately constant regardless of the radiation exposure dose. The In this case, the afterimage characteristic data has a characteristic that the ratio or intensity of the afterimage is substantially constant regardless of the radiation irradiation dose.

  However, when a high dose is applied where the relationship between the sensor output and the radiation exposure dose is not proportional, the ratio of the afterimage amount to the sensor output changes. In this case, the afterimage characteristic data has a characteristic that the ratio or intensity of the afterimage changes for each radiographing depending on the radiation exposure dose. That is, it is necessary to estimate the afterimage amount by dividing into cases as follows.

  Case 1 (When sensor output and radiation dose are proportional)

  Case 2 (When sensor output and radiation dose are not proportional)

  The afterimage correction procedure is the same as in the first embodiment. For example, in the case 1, the afterimage amount is estimated by the equation (5) based on the radiation dose threshold k ′ for distinguishing the case 1 and the case 2 using a linear function. In case 2, the afterimage amount is estimated based on the above equation (1).

(Third embodiment)

  In the third embodiment, when the radiation imaging condition that changes during imaging is the sensor temperature (the temperature of the radiation detection unit 102), a method is described in which a threshold value is provided for the sensor temperature and the correction method is changed before and after the threshold value. To do.

  When the sensor output and the sensor temperature are in a proportional relationship, assuming that the sensor output and the afterimage amount are in a proportional relationship, the ratio or intensity of the afterimage with respect to the sensor output is estimated to be substantially constant regardless of the sensor temperature. In this case, the afterimage characteristic data has a characteristic that the ratio or intensity of the afterimage is substantially constant regardless of the sensor temperature.

  However, when the relationship between the sensor output and the sensor temperature is not proportional, the ratio of the afterimage amount to the sensor output changes. In this case, the afterimage characteristic data has a characteristic that the ratio or intensity of the afterimage changes for each radiographing depending on the sensor temperature. That is, it is necessary to estimate the afterimage amount by dividing into cases as follows.

  Case 1 (first temperature region in which the sensor output and the afterimage amount are in a proportional relationship): T1 ≦ T ≦ T2

  Case 2 (second temperature region where the sensor output and the afterimage amount are not in a proportional relationship): T <T1

  Case 3 (third temperature region where the sensor output and the afterimage amount are not in a proportional relationship): T> T2

  Here, T is the sensor temperature [° C.]. T1 is a lower limit value of a temperature region in which the sensor output and the afterimage amount are in a proportional relationship. T2 is an upper limit value of a temperature region in which the sensor output and the afterimage amount are in a proportional relationship.

  The afterimage correction procedure is the same as in the first embodiment. For example, in the case 1, the afterimage amount is estimated by the equation (5) based on the sensor temperature threshold k ′ = T1 that distinguishes the case 1 and the case 2 using a linear function. In case 2 and case 3, the afterimage amount is estimated based on the above equation (1).

  As mentioned above, although embodiment which concerns on this invention was described, this invention is not limited to these, It can change and change within the range described in the claim.

  The present invention supplies software (programs) for realizing the functions of the above-described embodiments to a system or apparatus via a network or various storage media, and a computer (CPU, MPU, etc.) of the system or apparatus reads the program. May be executed. The present invention can also be realized by a process in which one or more processors in a computer of a system or apparatus read and execute a program, and can also be realized by a circuit (for example, an ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 100 Radiography apparatus 101 Radiation irradiation part 102 Radiation detection part 103 Tube control part 104 Imaging condition setting part 105 Detector control part 106 Data collection part 107 Afterimage correction part 108 Image display part 201 Memory part 202 Frame information acquisition part 203 Afterimage estimation Part (calculation part)
204 Arithmetic unit

Claims (10)

A radiographic apparatus that performs the radiography based on radiographic imaging conditions,
Detecting means for detecting irradiated radiation and outputting radiation image data;
A calculation unit that sets a threshold value related to the imaging condition and calculates an afterimage characteristic that represents a characteristic of the afterimage in the radiation image data based on the threshold value;
Correction means for correcting the radiation image data based on the afterimage calculated by the afterimage characteristics;
A radiation imaging apparatus comprising:   The imaging conditions include the number of imaging of the radiographic image data within a predetermined time, the number of imaging frames of the radiographic image data within a predetermined time, the imaging frame rate of the radiographic image data, the imaging time of the radiographic image data, a predetermined 2. The radiographic apparatus according to claim 1, wherein the radiation imaging apparatus is at least one of the number of times of irradiation of the radiation within the period of time, the irradiation time of the radiation, the irradiation dose of the radiation, and the temperature of the detection means.   The afterimage characteristic changes using a characteristic in which the ratio or intensity of the afterimage changes every time the radiographing is performed, and a characteristic in which the ratio or intensity of the afterimage is substantially constant regardless of the parameters of the imaging conditions. The radiation imaging apparatus according to claim 1 or 2.   The imaging conditions include the number of radiographic image data imaging within a predetermined time, the number of radiographic image data imaging frames within a predetermined time, the radiographic image imaging time, and the radiation irradiation within a predetermined time. In the region where the imaging condition parameter is less than or less than the threshold when the number of times is at least one, the afterimage is calculated according to the afterimage characteristics in which the ratio or intensity of the afterimage changes with each radiography, The afterimage is calculated based on the afterimage characteristic in which the ratio or intensity of the afterimage is substantially constant regardless of the imaging condition in an area where the parameter of the imaging condition is equal to or greater than the threshold or greater than the threshold. Item 4. The radiation imaging apparatus according to any one of Items 1 to 3. 5. The radiographic apparatus according to claim 1, wherein the afterimage characteristic is expressed by the following expression in a region where the parameter of the imaging condition is less than the threshold or less than the threshold.

A (x, k) = bn (k) × exp (−an) × S (x, k)
S (x, k) = IC (x, k−1) + exp (−an) × S (x, k−1)

x: pixel number k: number of times of radiation imaging A (x, k): afterimage in pixel number x of the kth radiographic image data an: time constant or attenuation rate of afterimage bn (k): ratio or intensity S ( x, k): Image information IC (x, k−1) including the previous radiation image data subjected to afterimage correction: Radiation image data after afterimage correction at pixel number x of the k−1th radiation image data 6. The radiographic apparatus according to claim 1, wherein the afterimage characteristic is expressed by the following expression in an area where the parameter of the imaging condition is equal to or greater than the threshold value or greater than the threshold value.

A (x, k) = bn (k ′) × exp (−an) × S (x, k)
S (x, k) = IC (x, k−1) + exp (−an) × S (x, k−1)

x: pixel number k: number of times of radiography k ′: threshold value A (x, k) of the number of times of radiography: afterimage at pixel number x of the kth radiographic image data an: time constant or attenuation rate bn (k ): Ratio or intensity of afterimage S (x, k): Image information IC (x, k-1) including previous radiation image data subjected to afterimage correction: Pixel number x of the (k-1) th radiation image data Image data after afterimage correction in Japan The radiographic apparatus according to claim 1, wherein the correction unit corrects the radiographic image data based on the following expression.

IC (x, k) = I (x, k) -A (x, k)

x: Pixel number k: Number of times of radiation imaging IC (x, k): Radiation image data I (x, k) after afterimage correction at pixel number x of the k-th radiation image data: Pixel of k-th radiation image data Radiation image data A (x, k) before afterimage correction at number x: Afterimage at pixel number x of the kth radiation image data Radiation irradiating means for irradiating radiation based on radiographic imaging conditions;
Detecting means for detecting the irradiated radiation and outputting radiation image data;
A calculation unit that sets a threshold value related to the imaging condition and calculates an afterimage characteristic that represents a characteristic of the afterimage in the radiation image data based on the threshold value;
Correction means for correcting the radiation image data based on the afterimage calculated by the afterimage characteristics;
A radiation imaging system comprising: A radiographic method for performing radiography based on radiographic imaging conditions,
Detecting irradiated radiation and outputting radiation image data;
Setting a threshold relating to the imaging condition, and calculating an afterimage characteristic representing an afterimage characteristic in the radiation image data based on the threshold;
Correcting the radiation image data based on the afterimage calculated by the afterimage characteristics;
A radiation imaging method comprising: The program for functioning a computer as each means of the radiography apparatus of any one of Claims 1 thru | or 7.

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