JP2015080518A - Radiation imaging device and method for controlling the same, radiation image processing device and method, program and computer readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably correct a radiation defective pixel to be generated when automatically detecting radiation irradiation to acquire a radiation image.SOLUTION: A radiation imaging device: acquires a radiation image from radiation detected by radiation detection means; corrects a first pixel that is a correction object in the radiation image by referring to a second pixel other than the first pixel; calculates an evaluation value for evaluating increase of a noise level caused by correcting the first pixel; and performs processing for reducing the noise level to the first pixel after correction on the basis of the calculated evaluation value.

Description

  The present invention relates to a technique for correcting pixels present in a radiation image (for example, an X-ray image) in which radiation has been lost.

  In recent years, flat panel detectors (hereinafter referred to as FPD) that accumulate X-rays as charge signals and convert them into digital signals to provide diagnostic images have been put into practical use. Such an X-ray imaging apparatus using an FPD is configured to perform imaging while synchronizing the X-ray irradiation by the X-ray generator and the imaging operation by the FPD.

  On the other hand, there are many market demands to replace existing modality films and imaging plate portions with FPDs. When an imaging unit having such an existing modality is to be replaced with an FPD, it may be difficult to construct an interface for synchronizing the X-ray generator and the FPD. Patent Document 1 proposes an FPD that detects X-ray irradiation on the FPD side and automatically starts an accumulation operation without providing an interface between the X-ray generator and the FPD.

  However, when the X-ray irradiation is automatically detected and the accumulation operation is started on the FPD side, a certain amount of X-ray irradiation is necessary until the X-ray is detected and the accumulation operation is started. Will be done. For this reason, the charge due to the irradiated X-rays is discharged after the X-ray irradiation is actually started until the accumulation operation is started by detecting the X-rays, and the discharged charges contribute to the output value. Can not. Accordingly, a pixel in which charges are discharged and X-ray information is lost (hereinafter, this pixel is referred to as an X-ray defect pixel) and a pixel from which charges are not discharged (hereinafter, this pixel is referred to as a non-X-ray defect pixel). ) Has a problem that the output value varies even with the same incident X-ray dose.

  For example, in Patent Document 1, since the reset operation at the time of X-ray detection is performed for each line and the even-numbered line and the odd-numbered line are switched for each frame, the charge is discharged from the X-ray irradiation to the start of the accumulation operation. Is every other line. As a result, a line from which charges are discharged (hereinafter referred to as an X-ray defect line) and a line from which charges are not discharged (hereinafter referred to as a non-X-ray defect line) are alternately generated. There is a problem that a difference in output value between lines appears in a stripe pattern on an image. Regarding this problem, Patent Document 1 discloses a method of discarding X-ray defect line data as a defect and correcting it by linear interpolation of surrounding pixels.

  In addition, as a method other than the above-described method, a method of obtaining an X-ray defect rate in an X-ray defect line from a non-X-ray defect line adjacent to the X-ray defect line and digitally amplifying an output value according to the defect rate has recently been developed. Proposed. In this method, since the information of the X-ray defect line can be effectively used as compared with the method of discarding the X-ray defect line as a defect, a more preferable correction result can be obtained.

JP2011-249891A

X-rays that are not limited to the above-described automatic detection of X-rays and the reset operation of the FPD, but include X-ray defect pixels (X-ray defect lines) and non-X-ray defect pixels (non-X-ray defect lines). It is important to appropriately correct X-ray defect pixels (X-ray defect lines) in an image. This is because X-ray deficient pixels or improperly corrected X-ray deficient pixels in the X-ray image affect the interpretation performed by the doctor.
However, as described above, when the output value is amplified according to the defect rate of the X-ray defect line in the X-ray image, not only the signal but also the superimposed noise is amplified. Therefore, when driving as described in Patent Document 1 is used, the noise level differs between the adjacent X-ray defect line and the non-X-ray defect line even though the incident X-ray dose is substantially equal, and this is not possible. There is a problem that it becomes a natural image.

  Accordingly, an exemplary object of the present invention is to provide a correction method capable of suppressing deterioration in noise level that occurs when correcting pixels.

In order to achieve the above object, a radiation imaging apparatus according to one aspect of the present invention has the following arrangement. That is,
Acquisition means for acquiring an X-ray image from X-rays detected by the radiation detection means;
Correction means for correcting the first pixel to be corrected in the radiation image with reference to a second pixel other than the first pixel;
Calculating means for calculating an evaluation value for evaluating an increase in noise level caused by correcting the first pixel by the correcting means;
Reduction means for performing a process of reducing the noise level on the corrected first pixel based on the evaluation value calculated by the calculation means.

  According to the present invention, it is possible to reduce the deterioration of the noise level that occurs during pixel correction.

The figure which shows the structural example of the X-ray imaging apparatus by embodiment. The flowchart which shows the process sequence in embodiment. FIG. 6 illustrates a circuit configuration of an FPD. The figure explaining the drive of FPD. The figure explaining the fall of the output value in a X-ray defect line. The figure explaining the calculation method of a correction coefficient.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is applied to a radiation imaging apparatus that acquires a radiation image from a radiation dose detected by a radiation detection unit that detects radiation and performs radiation image processing, for example, an X-ray imaging apparatus 100 as shown in FIG. When the X-ray imaging apparatus 100 automatically detects X-ray irradiation and acquires an X-ray image, the X-ray imaging apparatus 100 corrects an X-ray deficient pixel in the X-ray image that is generated due to the loss of X-rays by a reset operation A function of executing X-ray image processing for the purpose.

  In the X-ray imaging apparatus 100 as described above, the X-ray tube 101 irradiates the subject 103 with X-rays. The X-ray generator 104 applies a high voltage pulse to the X-ray tube 101 when an exposure switch (not shown) is pressed to generate X-rays. The FPD 102 is controlled by the FPD control unit 105 to convert X-rays transmitted through the subject 103 into visible light using a fluorescent substance and detect it with a photodiode. The detected electrical signal is AD converted and transmitted to the FPD control unit 105. The FPD control unit 105 includes an image processing unit 109 and an image storage unit 108, and includes one or more computers (not shown).

  The computer included in the FPD control unit 105 includes a main control unit such as a CPU and a storage unit such as a ROM (Read Only Memory) and a RAM (Random Access Memory). Further, the computer may include a graphic control unit such as a GPU (Graphics Processing Unit), a communication unit such as a network card, an input / output unit such as a keyboard, a display, or a touch panel. Each of these components is connected by a bus or the like, and is controlled by the main control unit executing a program stored in the storage unit. The monitor 106 displays the received digital signal or the digital signal processed by the image processing unit 109 as an image. The operation unit 107 inputs an instruction from the user to the image processing unit 109 and the FPD 102. The image storage unit 108 stores the digital signal output from the FPD control unit 105 and the image data processed by the image processing unit 109. The image processing unit 109 corrects X-ray deficient pixels in the image captured by the FPD 102, and includes a correction coefficient calculation unit 110, a correction unit 111, a deterioration degree calculation unit 112, and a noise reduction unit 113.

The operation of the X-ray imaging apparatus 100 of the present embodiment having the above configuration will be specifically described with reference to the flowchart shown in FIG. First, a high voltage pulse is applied to the X-ray tube 101 by the X-ray generator 104 to irradiate the subject 103 with X-rays. After the X-ray irradiation is started, the FPD 102 starts an accumulation operation by automatically detecting the X-ray irradiation and acquires an X-ray image (S201).

  Here, the driving for automatically detecting and determining the start of X-ray irradiation will be specifically described with reference to FIGS. FIG. 3 shows a circuit configuration of the FPD 102. The FPD 102 has pixels formed of TFTs 302 and photodiodes 303, and several thousand pixels are formed on the glass substrate 301 both vertically and horizontally. Note that FIG. 3 shows an FPD composed of four pixels both vertically and horizontally for explanation. The scanning line control circuit 306 sequentially applies an ON signal to G1 to G4 to turn on the TFT 302. G1 to G4 are scanning lines. When an ON signal is applied to each scanning line, the TFT 302 is switched on, and the output charge of the photodiode 303 can be read line by line. S1 to S4 are signal lines. The charges read from the photodiode 303 are transmitted through the signal lines and read by the signal detection circuit 305. The signal detection circuit 305 holds the read signal, processes it such as amplification, AD conversion, and outputs it as a digital signal to the FPD control unit 105. A power supply 304 supplies an operating voltage to each photodiode 303.

  FIG. 4 is a timing chart showing driving of the FPD 102 in this embodiment. When the X-ray is not irradiated, the FPD 102 stands by for the X-ray detection drive. At this time, the scanning line control circuit 306 sequentially drives the scanning lines by odd numbers such as G1, G3... In the first frame. Then, the dark charges of the pixels connected to the odd-numbered scanning lines are read and reset. In the next second frame, the scanning line control circuit 306 sequentially drives only the even lines such as G2, G4,..., And resets the pixels connected to the even-numbered scanning lines. Thus, the odd lines are reset in the odd frames, and the odd lines are reset alternately by resetting the even lines in the even frames.

  Here, the signal detection circuit 305 of the FPD control unit 105 monitors the reset charge to detect X-ray irradiation. When the X-rays are irradiated, charges are generated by the photodiode 303, so that the output of the signal line is increased. When this output exceeds a predetermined threshold value, the FPD control unit 105 considers that X-rays have been irradiated and starts the accumulation operation by turning off all the TFTs 302.

  Incidentally, X-ray irradiation can be detected more quickly as the threshold for detecting the above-mentioned X-ray irradiation is smaller, but erroneous detection due to noise or the like is likely to occur. Therefore, it is necessary to set the threshold value to a certain value in consideration of such a malfunction. As a result, there is a considerable time lag between the start of X-ray irradiation and the detection of X-ray irradiation. Due to this time lag, the charge due to the X-rays irradiated until the accumulation operation is started cannot contribute to the output value, and becomes smaller than the original output value. In other words, a correction target line in which correction target pixels (referred to as defective pixels in this specification) in which X-rays are lost is arranged is generated.

  FIG. 5 is a schematic diagram showing a decrease in the output value when uniform X-rays are irradiated. Here, FIG. 5A shows one rectangle as one pixel. FIG. 5B is a bar graph showing the sum of the output values of the pixels in each row of FIG. When uniform X-rays are irradiated, the sum of the output values of each row is substantially the same if there is no time lag until X-ray irradiation is detected. Here, it is assumed that X-ray irradiation is started on the even line G4 and X-ray irradiation is detected on the even line G8. In this case, X-rays are lost in the even-numbered lines G4, G6, and G8 in which the reset operation is performed as shown in FIG. 5B, and the value becomes smaller than the original output value. These lines G4, G6, and G8 are correction target lines. On the other hand, X-ray loss due to the reset operation does not occur in other lines, and these lines are pixels that do not need to be corrected (that is, pixels other than the correction target pixels, hereinafter referred to as non-correction target pixels). ) Are non-correction target lines.

  Note that the decrease in the output value depends on the time lag from when the X-ray irradiation is started until the reset operation is performed, and the decrease becomes larger as the time lag increases. Therefore, in the operation of this embodiment, since the reset operation is sequentially performed from G1, the output values decrease greatly from G4 to G6, G8 from which X-ray irradiation is started as shown in FIG. 5B.

  As described above, the X-ray image obtained by the operation as described above has portions in which correction target lines in which correction target pixels are arranged and non-correction target lines in which non-correction target pixels are arranged alternately exist. Then, such an X-ray image is transferred to the image processing unit 109 and a correction target line (hereinafter referred to as an X-ray defect line) whose output value is reduced is corrected. A specific correction method will be described below.

First, the correction coefficient calculation unit 110 calculates a correction coefficient for correcting the output value of the X-ray defect line (S202). Usually, the output value V of each pixel (hereinafter, the output value of each pixel may be referred to as a pixel value) is the sum of a gain component proportional to the X-ray dose X incident on the pixel and an offset component D due to dark current or the like. If the proportionality constant is A, the relationship between the pixel value V and the X-ray dose X is as follows.

In contrast, the pixel values V _d of the X-ray-deficient line, part of the X-ray dose X that is incident on the pixel is lost by the reset operation, the X-ray dosage contributes to the pixel value is reduced to 1 / G times. Therefore, the relationship between the pixel values V _d and X-ray dose X of the X-ray defective line is as follows.

なお、式（３）のＧ，Ｄの値は未知であり、これら２つを補正係数として算出することで、Ｘ線欠損ラインの画素値Ｖ_dを本来の画素値Ｖに補正することができる。 Therefore, the relationship between the pixel value V _d of the X-ray defect line and the original pixel value V is as follows from the equations (1) and (2).

Note that the values of G and D in Equation (3) are unknown, and the pixel value V _d of the X-ray defect line can be corrected to the original pixel value V by calculating these two as correction coefficients. .

Therefore, in this embodiment, the correction coefficients G and D are calculated by regression analysis using pixel values of adjacent non-X-ray defect lines (that is, non-correction target lines) that have a high correlation with the X-ray defect lines. More specifically, the pixel value of each column i of the X-ray defect line is {x _i | i = 1, 2,..., N} as shown in FIG. Let the pixel values of _i be {y _{i, 1} | i = 1,2,..., n} and {y _{i, 2} | i = 1,2,. If it is assumed that the pixel values in each column have substantially the same value, the relationship between the pixel value x of the X-ray defect line and the pixel value y of the non-X-ray defect line is expressed by the following equation (4).

Here, as in Expression (4), the relationship between x and y is expressed by a linear expression of slope G and intercept D · (1-G), and G and D can be calculated by linear regression analysis. . For example, when least square regression is used as a method of linear regression analysis, a slope a and an intercept b that minimize the error E represented by the equation (5) are obtained, and corrected by the equation (6) from the obtained slope a and the intercept b. The coefficients G and D may be calculated.

  Here, in the present embodiment, the method using the least square regression has been described, but the present invention is not limited to this method, and the correction coefficient can be similarly set even if an already known method such as MA regression or RMA regression is used. Can be calculated. In this embodiment, the correction coefficient is obtained on the assumption that the pixel values of the respective columns have substantially the same value. However, when a steep edge or the like exists, there is a pixel for which this assumption does not hold. Therefore, as a countermeasure against such outliers, known robust regression such as M estimation, LMedS estimation, and RANSAC can be used.

  Although the calculation method of the correction coefficients G and D for one X-ray defect line has been described above, the same processing is performed for all X-ray defect lines, and the correction coefficients G and D for each X-ray defect line are obtained. calculate. Since the timing at which X-ray irradiation is started is unknown, it is unknown which line is the X-ray defect line. Therefore, in this embodiment, how to determine whether or not the line is a correction target line is performed. That is, select the correction target line (X-ray deficient line) by going back from the line where the reset operation was performed at the timing when the X-ray irradiation was detected to the line where the reset operation was performed sequentially. Then, the correction coefficient of the selected correction target line (X-ray defect line) is obtained, and the correction coefficients G and D may be calculated up to a line where the correction coefficient G is within a predetermined range, for example, approximately 1. For example, in FIG. 5B, when G6 and G4 and correction coefficients G and D are obtained in order from G8 when the reset operation is performed at the timing when X-ray irradiation is detected, and the correction amount falls within a predetermined range. The calculation of the correction coefficient is finished. For example, the calculation of the correction coefficient ends at the line G2 where the correction coefficient G is approximately 1. Note that a line to be corrected may be traced back a predetermined number of lines from the line where the reset operation was performed at the timing when X-ray irradiation was detected. In this case, the predetermined number of lines may be obtained in advance by calculation or experiment.

Next, the correction unit 111 corrects each defective pixel of the defective line using the obtained correction coefficients G and D (S203). Specifically, the pixel value of each column i of the X-ray deficient line is {V _d (i) | i = 1, 2,..., N}, the correction coefficients for the line are G and D, and The pixel value V (i) after correction is calculated for all X-ray deficient lines by (7).

Next, the degree of deterioration calculation unit 112 calculates the degree of noise deterioration for each of all the corrected pixels (S204). Here, the noise level at the X-ray dose corresponding to the pixel value of the pixel to be corrected before correction is increased by the correction as described above, and at the X-ray dose corresponding to the pixel value after the correction. An evaluation value is calculated based on the noise level. Therefore, this evaluation value indicates the degree of noise level deterioration due to correction. Usually, the noise level superimposed on the output of each pixel is dominated by quantum noise proportional to the X-ray dose X incident on the pixel and system-specific system noise that does not depend on the X-ray dose. Therefore, if the standard deviation of the quantum noise is σ _Q and the standard deviation of the system noise is σ _S , the standard deviation σ of noise superimposed on the output of each pixel is expressed by the following equation depending on the additiveness of the variance.

On the other hand, in the pixel of the X-ray defect line, a part of the X-ray dose X incident on the pixel is lost by the reset operation, and the X-ray dose contributing to the output is reduced to 1 / G times. Therefore, the standard deviation σ _{d of} noise superimposed on the output of the pixel of the X-ray defect line is expressed by the following equation.

Here, in the X-ray defect line corrected by Expression (7), the signal component included in the output value of the pixel is multiplied by G and the noise is also multiplied by G by G which is the magnification of correction. That is, the standard deviation σ _{C of} noise superimposed on the output value of the pixel of the corrected X-ray defect line is expressed by the following equation (10).

Therefore, the noise level included in the output value of the pixel of the corrected X-ray defect line is σ _C / σ with respect to the noise level included in the output value of the original pixel (output value when the X-ray dose is X). The noise level will be doubled. Therefore, for each pixel, this value is calculated as an evaluation value (hereinafter referred to as noise deterioration degree W) representing an increase in noise level. A specific calculation method is the following equation (11).

Here, the standard deviation σ _Q of the quantum noise and the standard deviation σ _S of the system noise are values uniquely determined by the imaging system, and values calculated in advance may be held in advance and used. Further, the incident X-ray dose X can be calculated by using the relationship of the above-described equation (1). Specifically, if the pixel value in the i row and j column of the corrected image V is V (i, j), the X-ray dose X (i, j) incident on each pixel is calculated by the following equation. can do.

  Here, N determines a filter size for removing the influence of noise, and is set to 2, for example, in the present embodiment. A is a proportional constant for converting the X-ray dose X into the pixel value V, and is a value uniquely determined by the sensor. Therefore, a value calculated in advance may be stored in advance and used.

  Next, the noise reduction unit 113 performs noise reduction for all the corrected pixels (S205). Here, it is assumed that the noise level in adjacent pixels is the same, and the corrected noise level of the X-ray defective pixel is corrected so as to be substantially equivalent to that of the adjacent non-X-ray defective pixel.

In the present embodiment, noise of X-ray defective pixels corrected by three-point weighted addition (filtering) of upper and lower non-X-ray defective pixels adjacent to the corrected X-ray defective pixel is reduced. Specifically, if the pixel value in the i row and j column of the corrected image V is V (i, j), the noise of the X-ray deficient pixel is reduced by the following equation.

  In Equation (13), a is a weighting factor that determines the degree of noise reduction, and the corrected noise level of the pixel V (i, j) is the adjacent pixel V (i−1, j), V ( It is set to be approximately equivalent to the noise level of i + 1, j). Hereinafter, a method for determining a will be described.

First, if the standard deviation of noise superimposed on the output of the corrected X-ray deficient pixel is σ _T , and the standard deviation of noise superimposed on the output of the adjacent pixel is σ _R , it is superimposed on the output obtained after noise reduction. The standard deviation σ of noise is as follows.

また、σ_Tとσ_Rの関係は上述したノイズ悪化度Wから下記式となる。

ここで、式（１５）と式（１６）を式（１４）に代入し、整理すると、

となる。よって、（１７）式の条件を満たすように、すなわち、下記の式（１８）にてａを設定すれば良い。

Here, the condition for the noise level of the corrected pixel V (i, j) to be substantially equivalent to the noise level of the adjacent pixels V (i−1, j) and V (i + 1, j) is as follows. It is.

Further, the relationship between σ _T and σ _R is expressed by the following equation based on the noise deterioration degree W described above.

Here, when formula (15) and formula (16) are substituted into formula (14) and rearranged,

It becomes. Therefore, a may be set so as to satisfy the condition of the expression (17), that is, the following expression (18).

  Here, since the weighting coefficient a is a value dependent on the deterioration degree W, a is calculated for each pixel based on the deterioration degree of each pixel calculated by the deterioration degree calculation unit 112, and noise correction is performed.

  In the above embodiment, the upper and lower two pixels are used for noise reduction of X-ray deficient pixels. However, the present invention is not limited to this. For example, noise reduction may be performed using six pixels including diagonally. Further, although the present embodiment uses a method of reducing noise with a linear filter, the present invention is not limited to this, and a non-linear filter that preserves edges, such as an ε filter or a bilateral filter, may be used. .

  Furthermore, although the said embodiment demonstrated the case where the correction target line in which a correction target pixel is located, and the non-correction target line in which a non-correction target pixel is located alternately, it is not restricted to this. For example, if the correction target pixel in which X-ray loss has occurred is an image arranged so as to be correctable by the non-correction target pixel in which X-ray loss has not occurred, the correction and noise level reduction according to the above embodiment are applied. can do. Therefore, for example, the present invention may be applied to a configuration in which reset is performed for each column instead of a configuration in which reset is performed for each line. In addition, for example, it is obvious that the above-described processing can be applied to an X-ray image in which correction target pixels and non-correction target pixels are arranged in a lattice pattern. Furthermore, in the above-described embodiment, an example in which reset is performed line by line as the reset operation in units of lines has been described. However, a plurality of even lines or odd lines (for example, “G2 and G4”, “G6 and G8” in FIG. May be reset at the same time.

  As mentioned above, although preferable embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Further, the present invention supplies a software program (in the embodiment, a program corresponding to the flowchart shown in the figure) to the system or apparatus directly or remotely, and the computer of the system or apparatus implements the functions of the above-described embodiments. Is also achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  Computer-readable recording media for supplying the program include, for example, a hard disk, an optical disk, a magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD ( DVD-ROM, DVD-R).

  As another program supply method, a client computer browser is used to connect to an Internet homepage, and the computer program of the present invention itself or a compressed file including an automatic installation function is downloaded from the homepage to a recording medium such as a hard disk. Can also be supplied. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  In addition to the functions of the above-described embodiments being realized by the computer executing the read program, the OS running on the computer based on the instructions of the program is a part of the actual processing. Alternatively, the functions of the above-described embodiment can be realized by performing all of them and performing the processing.

Claims (19)

Obtaining means for obtaining a radiation image from radiation detected by the radiation detecting means;
Correction means for correcting the first pixel to be corrected in the radiation image with reference to a second pixel other than the first pixel;
Calculating means for calculating an evaluation value for evaluating an increase in noise level caused by correcting the first pixel by the correcting means;
A radiation imaging apparatus comprising: a reduction unit that performs a process of reducing a noise level on the corrected first pixel based on the evaluation value calculated by the calculation unit.   The correction means obtains a correction coefficient by performing regression analysis on the relationship between the pixel value of the first pixel and the pixel value of the second pixel adjacent to the first pixel, and uses the correction coefficient. The radiation imaging apparatus according to claim 1, wherein the first pixel is corrected. The calculating means includes
The noise level at the radiation dose corresponding to the pixel value before correction of the first pixel is increased by the correction of the correction means, and the noise at the radiation dose corresponding to the pixel value after correction of the first pixel The radiographic apparatus according to claim 1, wherein the evaluation value is calculated based on a level.   The radiographic apparatus according to claim 3, wherein the noise level is a standard deviation of noise. The calculation means includes σ _Q as a standard deviation of quantum noise depending on the radiation dose, σ _S as a standard deviation of system noise independent of the radiation dose, G as a correction factor by the correction means, and X as a pixel value after correction. When the radiation dose corresponds to

The radiographic apparatus according to claim 4, wherein the evaluation value is obtained by:   The reduction means reduces the noise level so that a corrected noise level of the first pixel is equivalent to a noise level of the second pixel adjacent to the first pixel. The radiation imaging apparatus according to any one of claims 1 to 5.   7. The noise reduction unit according to claim 1, wherein the reduction unit applies a filter determined based on the evaluation value to the corrected first pixel to reduce a noise level. The radiation imaging apparatus according to item 1.   The radiation imaging apparatus according to claim 7, wherein the reduction unit performs the noise level of the first pixel after correction by filtering with a plurality of adjacent second pixels.   The radiation imaging apparatus according to claim 1, wherein the first pixel is a pixel in which loss of radiation information has occurred due to a reset operation of the radiation detection unit.   The radiation image has a portion where the correction target line in which the first pixels are arranged and the non-correction target line in which the second pixels are arranged alternately. The radiation imaging apparatus according to item 1. While further resetting the radiation detection means in units of lines, further comprises a determination means for determining the start of radiation irradiation based on a signal read at the time of reset,
The correction target line and the non-correction target line in the radiation image are alternately arranged by repeating the reset after the radiation detection unit is irradiated with radiation until the determination unit determines that the irradiation is started. The radiation imaging apparatus according to claim 10, wherein an existing part is generated.   For each correction target line, the correction unit determines a correction coefficient of the correction target line by performing linear regression analysis of a relationship with an adjacent non-correction target line, and uses the correction coefficient to determine the correction target line. The radiation imaging apparatus according to claim 11, wherein the pixel is corrected. From the line determined to start irradiation by the determination means, select the correction target line by going back in the order of execution of the reset,
The radiation imaging apparatus according to claim 12, wherein a correction target line is a line up to a line in which a correction amount of a pixel value indicated by the correction coefficient falls within a predetermined range. Correction means for correcting the first pixel to be corrected in the radiographic image with reference to a second pixel other than the first pixel;
Calculating means for calculating an evaluation value for evaluating an increase in noise level caused by correcting the first pixel by the correcting means;
A radiation image processing apparatus comprising: a reduction unit that performs a process of reducing a noise level on the corrected first pixel based on the evaluation value calculated by the calculation unit. An acquisition step of acquiring a radiation image from the radiation detected by the radiation detection means;
A correction step of correcting the first pixel to be corrected in the radiation image with reference to a second pixel other than the first pixel;
A calculation step for calculating an evaluation value for evaluating an increase in noise level caused by correcting the first pixel in the correction step;
A radiation imaging apparatus control method, comprising: a reduction step of performing a process of reducing a noise level on the corrected first pixel based on the evaluation value calculated in the calculation step. A correction step of correcting the first pixel to be corrected in the radiation image with reference to a second pixel other than the first pixel;
A calculation step for calculating an evaluation value for evaluating an increase in noise level caused by correcting the first pixel in the correction step;
A radiation image processing method comprising: a reduction step of performing a process of reducing a noise level on the corrected first pixel based on the evaluation value calculated in the calculation step.   The program for functioning a computer as each means of the radiography apparatus described in any one of Claims 1 thru | or 13.   The program for functioning a computer as each means of the radiographic image processing apparatus described in Claim 14.   A computer-readable recording medium storing the program according to claim 17 or 18.

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