JP2009204310A - Radiation image photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image photographing device capable of reducing a photographing interval regardless of accumulation time in photographing, when performing the lag correction of a radiation image. <P>SOLUTION: The radiation image photographing device comprises: an image acquisition section for acquiring lag data of the previous radiation image when no radiations are applied before the next photographing, and for acquiring the data of the next radiation image after the next photographing; an offset correction section for performing the offset correction of the lag data in the previous radiation image and the data of the next radiation image; an accumulation time correction section for converting the lag data after the offset correction to data corresponding to the accumulation time of the radiation image data in the next photographing; a lag correction section for performing lag correction by subtracting the lag data after correcting the accumulation time from the data of the next radiation image after the offset correction; and a control section for controlling the operation of the photographing device. The control section performs control so that the lag data are read from the radiation detector in shortened accumulation time that is smaller than the accumulation time in the next photographing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radiographic imaging apparatus that irradiates a subject with radiation, detects the radiation transmitted through the subject, converts the radiation into an electrical signal, and generates a radiation image based on the converted electrical signal.

  Radiographic imaging devices are used in various fields including, for example, medical diagnostic images and industrial nondestructive inspection. As a radiation detector for detecting radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.) transmitted through a subject in a radiographic imaging apparatus, a flat panel that converts radiation into electrical signals at present There is a type using a flat panel detector (FPD). In a radiographic image capturing apparatus using FPD, an afterimage of a previously captured radiographic image becomes a problem as a cause of deterioration in the image quality of the radiographic image obtained by imaging the subject.

  In a radiographic imaging apparatus using an FPD, a subject is irradiated with radiation from a radiation source, the radiation transmitted through the subject is converted into an electrical signal by the FPD, and an electrical signal corresponding to the image data of the subject is read out from the FPD. Is generated. However, even after the electrical signal corresponding to the image data is read from the FPD, a part of the charge corresponding to the image data remains in the FPD. When the next subject is photographed in this state, the residual charge in the FPD is superimposed on the next radiation image as an afterimage, and the radiation image becomes an image affected by the afterimage.

  Therefore, in the radiographic image capturing apparatus, before capturing the next subject, an afterimage correction process is performed to remove the influence of the afterimage of the subject image captured before (before the next capturing). The afterimage correction process is usually performed by the following steps 1 to 4.

  In the following description, Offset (x, y) is offset correction data for correcting image data offset (deviation from the reference voltage level), and Xdata (x, y) is taken by irradiating radiation. The radiographic image data (corrected image data) of the next subject, Lagdata (x, y) is the afterimage data of the previous radiographic image read from the FPD without irradiation immediately before the next imaging. , Α is a correction coefficient for the afterimage amount for correcting a decrease in the afterimage amount (afterimage charge amount) from when the afterimage data is read until the next shooting is performed.

(Step 1)
As shown in the following formula (1), the offset correction data Offset (x, y) is subtracted from the afterimage data Lagdata (x, y) to offset the afterimage data Lagdata (x, y). Later image data Data1 (x, y) is obtained.
Data1 (x, y) = Lagdata (x, y)-Offset (x, y) (1)

(Step 2)
As shown in the following formula (2), the afterimage data Data1 (x, y) after the offset correction is obtained by multiplying the afterimage data Data1 (x, y) after the offset correction by a correction coefficient α of the afterimage amount. Correction is performed to obtain afterimage data after correction (image data for correction) Data2 (x, y).
Data2 (x, y) = α × Data1 (x, y) (2)

(Step 3)
As shown in the following equation (3), the correction image data Xdata (x, y) is offset corrected by subtracting the offset correction data Offset (x, y) from the correction image data Xdata (x, y). Thus, corrected image data Data3 (x, y) after offset correction is obtained.
Data3 (x, y) = Xdata (x, y)-Offset (x, y)… (3)

(Step 4)
As shown in the following equation (4), the corrected image data Data2 (x, y) is subtracted from the corrected image data Data3 (x, y) after the offset correction, and the corrected image data Data3 (x, y) is obtained. Afterimage correction is performed to obtain image data Data4 (x, y) after the afterimage correction.
Data4 (x, y) = Data3 (x, y)-Data2 (x, y) (4)

Since the afterimage data has a lot of noise components, the noise component of the image data Data4 (x, y) after the afterimage correction may partially increase by performing subtraction in the afterimage correction. Therefore, as shown in the following equation (5), the image data Data4 ′ (x, y) after the afterimage correction is calculated by subtracting the median-processed correction image data median (Data2 (x, y)) There is also.
Data4 '(x, y) = Data3 (x, y)-median (Data2 (x, y))… (5)

  Here, as prior art documents relevant to the present invention, for example, Patent Documents 1 and 2 can be exemplified.

  Patent Literature 1 obtains a radiographic image based on a radiation detection signal detected by irradiating a subject. In this document, for example, a lag image is acquired based on a radiation detection signal acquired at the time of non-irradiation of radiation and an offset signal corresponding to the storage time, and the radiation detection signal acquired at the time of irradiation of radiation and its storage It is disclosed that a radiographic image is acquired based on an offset signal corresponding to time, and lag correction is performed by removing lag from the acquired radiographic image using a lag image.

  Patent Document 2 relates to imaging of a subject in which an imaging unit irradiates the subject with radiation and detects the radiation transmitted through the subject. In this document, for example, immediately after recognizing that the imaging unit has shifted to the imaging preparation state, a dark image is obtained without performing radiation irradiation by the imaging unit, image correction data is created based on the dark image, and the imaging unit It is disclosed that radiation imaging is performed by an imaging unit to obtain imaging data while the imaging preparation state is maintained, and the imaging data is corrected based on the image correction data.

International Publication No. WO2007-026419 Pamphlet JP 2002-369077 A

  In Patent Document 1, since afterimage data is acquired with the same accumulation time as that at the time of photographing, when an afterimage correction is performed on an image having a long accumulation time such as a still image, it takes the same time to acquire the afterimage data. Therefore, it is necessary to add processing such as shot restriction (shooting interval adjustment). In addition, even when continuous shooting is performed in a fixed sequence such as long shooting, there is a problem that the shooting interval becomes longer depending on the accumulation time of afterimage data. Furthermore, since the above-mentioned afterimage amount correction is not performed, there is a concern that the accuracy of afterimage correction is deteriorated.

  Further, in Patent Document 2, since acquisition of afterimage data is started after the shooting menu is set, the time difference from acquisition of the afterimage data to the next shooting of the subject is further increased. For this reason, there is a concern that the accuracy of afterimage correction is deteriorated for the same reason as in the cited document 1.

A first object of the present invention is to solve the above-described problems of the prior art and to perform a radiographic image afterimage correction, a radiographic imaging apparatus capable of shortening an imaging interval regardless of an accumulation time during imaging. Is to provide.
In addition to the first object, the second object of the present invention is that the afterimage amount is reduced from afterimage data is read until the next subject is photographed, thereby reducing the accuracy of afterimage correction. An object of the present invention is to provide a radiographic imaging apparatus that can prevent the above-described problem.

In order to achieve the above object, the present invention irradiates a subject with radiation from a radiation source, detects the radiation transmitted through the subject with a flat panel radiation detector, and obtains a radiographic image obtained by photographing the subject. A radiographic imaging device to generate,
When radiation is not irradiated before the next imaging, afterimage data of the previous radiation image read from the radiation detector is acquired, and after the next imaging is performed, the afterimage data is read from the radiation detector. An image acquisition unit for acquiring data of the next radiation image that has been issued;
A first offset correction unit for offset correction of the residual image data of the previous radiation image;
A second offset correction unit for offset correction of the data of the next radiation image;
An accumulation time correction unit that corrects the accumulation time by converting the offset-corrected afterimage data into data corresponding to the accumulation time of the radiation image data at the next imaging;
An afterimage correction unit that subtracts the afterimage data with the accumulated time corrected from the offset-corrected next radiation image data to correct the afterimage of the next radiation image;
A control unit for controlling the operation of the radiographic apparatus,
The control unit provides a radiographic imaging apparatus that controls the afterimage data to be read from the radiation detector with a shortened accumulation time shorter than the accumulation time at the next imaging. is there.

  Here, the first offset correction unit offset-corrects the afterimage data of the previous radiation image using the offset data calculated according to the accumulation time of the afterimage data of the previous radiation image, and The second offset correction unit preferably performs offset correction on the data of the next radiation image using offset data calculated according to the accumulation time of the data of the next radiation image.

  Furthermore, it is preferable that an afterimage amount correction unit that corrects a decrease in the afterimage amount of the afterimage data subjected to the offset correction after the afterimage data is read until the next photographing is performed is preferably provided. .

In addition, the radiographic imaging device includes a plurality of radiographing modes with different accumulation times of radiographic image data at the time of radiographing,
When the shooting mode is not the shooting mode with the shortest storage time during shooting, the control unit sets the shortened storage time as the storage time during shooting in the shooting mode with the shortest storage time during shooting. It is preferable to control as described above.

  Alternatively, the control unit preferably controls the shortened accumulation time to be the shortest accumulation time that can be set in the radiation imaging apparatus.

In addition, it has a two-stage push-type shooting button to instruct shooting,
The controller reads out the afterimage data of the previous radiation image from the radiation detector at the timing when the imaging button is pressed to the first stage, and starts imaging when the second stage is pressed. It is preferable to control as described above.

  The present invention is a case of continuous photographing such as long photographing by reading out the afterimage data of the previous radiation image from the radiation detector with an accumulation time shorter than the accumulation time at the time of capturing the next radiation image. Also, the shooting interval can be shortened. Further, by performing afterimage amount correction, it is possible to prevent the afterimage amount from decreasing after image data reading of the previous radiation image until the next imaging, thereby preventing the accuracy of afterimage correction from decreasing. .

  Further, in the present invention, by controlling so that the afterimage data of the previous radiation image is read from the radiation detector at the timing when the photographing button is pushed to the first step, The time difference from the timing of the next shooting can be shortened. For this reason, it is possible to perform high-accuracy afterimage correction without giving the user (operator) of the radiographic image capturing apparatus of the present invention an uncomfortable feeling of waiting time due to shot restriction.

  Hereinafter, a radiographic imaging apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a block diagram of an embodiment showing a configuration of a radiographic image capturing apparatus of the present invention. A radiographic imaging apparatus (hereinafter also referred to as an imaging apparatus) 10 shown in the figure irradiates a subject (subject) H with radiation, detects the radiation transmitted through the subject H, and generates an electrical signal corresponding to image data. Based on the converted electrical signal, a radiographic image in which the subject H is captured is generated. The imaging device 10 includes an imaging unit 12, an imaging data processing unit 14, an image processing unit 16, an output unit 18, an imaging instruction unit 20, and a control unit 22.

  The imaging unit 12 is a part that shoots the subject H by irradiating the subject H with radiation and detecting the radiation transmitted through the subject H. The imaging unit 12 outputs data (analog data) of a radiographic image obtained by imaging the subject H. Details of the photographing unit 12 will be described later.

  The imaging data processing unit 14 is a part that performs data processing such as A / D (analog / digital) conversion on the radiation image data supplied from the imaging unit 12. The radiographic image data (digital data) after data processing is output from the imaging data processing unit 14.

  The image processing unit 16 is a part that performs image processing such as offset correction, afterimage amount correction, accumulation time correction, and afterimage correction on the radiographic image data after data processing supplied from the imaging data processing unit 14. . The image processing unit 16 is configured by a program (software) operating on a computer, dedicated hardware, or a combination of both. The image processing unit 16 outputs the radiation image data after the image processing. Details of the image processing unit 16 will be described later.

  The output unit 18 is a part that outputs radiographic image data after image processing supplied from the image processing unit 16. The output unit 18 is, for example, a monitor that displays a radiation image on a screen, a printer that prints out a radiation image, a storage device that stores radiation image data, and the like.

  The photographing instruction unit 20 is a part that sets photographing conditions and a photographing mode and instructs photographing of the subject H. As the shooting instruction section 20, an input key for setting shooting conditions and a shooting mode, and a two-push type shooting button are used for shooting instructions. When the shooting button is pressed down to the first level (half-pressed), it is ready for shooting and when it is pressed down to the second level (fully pressed), shooting starts. The shooting instruction unit 20 outputs a shooting instruction signal indicating either the state where the shooting button is not pressed or the state where the first or second stage is pressed.

  Here, in the imaging apparatus 10, in addition to a manual imaging mode in which imaging conditions such as radiation intensity and irradiation time (amount of irradiation) are manually set as imaging modes, imaging conditions such as radiation intensity and irradiation time are set in advance. Is set, a first shooting mode for shooting still images and the like, and a second shooting mode for shooting long images and the like are provided. In the first shooting mode, the accumulation time during shooting is set longer than in the second shooting mode.

  The accumulation time is the time during which radiation is converted into charges and accumulated in the radiation detector. In the imaging apparatus 10, for example, when the subject H is captured, image data (radiation image data) is read from the radiation detector after a predetermined accumulation time. In addition, during the period from when the radiation image data is read until the afterimage data of the previous radiation image is acquired, the idle reading of the image data (afterimage data) is performed at a predetermined accumulation time interval in order to reduce the amount of afterimage Done in In addition, afterimage data is read after an accumulation time (shortened accumulation time) shorter than the accumulation time at the time of imaging of the next radiation image from the last empty reading before the next imaging is performed.

  The control unit 22 is a part that controls the operation of the imaging apparatus 10 in accordance with the imaging instruction signal supplied from the imaging instruction unit 20. For example, the control unit 22 controls the photographing unit 12 so that photographing is performed under predetermined photographing conditions or photographing modes. Further, control is performed so that afterimage data of the previous radiation image is read from the radiation detector with a shortened accumulation time. In addition, the control unit 22 controls the image processing unit 16 so that captured radiographic image data is acquired and image processing is performed.

  In the case of continuous imaging such as long imaging by reading afterimage data of the previous radiation image from the FPD 32 with an accumulation time shorter than the accumulation time at the time of imaging of the next radiation image under the control of the control unit 22 Even so, the shooting interval can be shortened.

  Next, the photographing unit 12 will be described.

  The imaging unit 12 includes an irradiation control unit 24, a radiation source 26, an imaging table 28, and a radiation detection unit 30.

  The irradiation control unit 24 drives the radiation source 26 to control the irradiation amount so that the radiation with the intensity set according to the imaging mode is irradiated for the set time. Radiation emitted from the radiation source 26 passes through the subject H on the imaging table 28 and enters the radiation detection unit 30.

  The radiation detection unit 30 detects the radiation transmitted through the subject H with the FPD 32 and converts it into an electrical signal (radiation image data). The radiation detection unit 30 outputs data (analog data) of a radiation image obtained by photographing the subject H. The FPD 32 can be either a direct FPD that directly converts radiation into electric charges, or an indirect FPD that converts radiation once into light and then converts the converted light into an electrical signal.

  The direct type FPD includes a photoconductive film such as amorphous selenium, a capacitor, a TFT (Thin Film Transistor) as a switch element, and the like. For example, when radiation such as X-rays is incident, electron-hole pairs (e-h pairs) are emitted from the photoconductive film. The electron-hole pair is accumulated in the capacitor, and the electric charge accumulated in the capacitor is read out as an electric signal through the TFT.

  On the other hand, an indirect FPD is composed of a scintillator layer made of a phosphor, a photodiode, a capacitor, a TFT, and the like. For example, when radiation such as “CsI: Tl” is incident, the scintillator layer emits light (fluoresces). Light emitted by the scintillator layer is photoelectrically converted by a photodiode and accumulated in a capacitor, and the electric charge accumulated in the capacitor is read out as an electrical signal through the TFT.

  Although not shown, the radiation source 26 and the radiation detection unit 30 are reciprocated along the longitudinal direction (left and right direction in FIG. 1) of the imaging table 28 for, for example, long imaging. It is configured as possible. On the other hand, you may comprise the imaging stand 28 so that a movement is possible.

  Next, the image processing unit 16 will be described.

  As shown in FIG. 2, the image processing unit 16 includes an image acquisition unit 34, a first offset correction unit 36, a second offset correction unit 38, an afterimage amount correction unit 40, and an accumulation time correction unit 42. And an afterimage correction unit 44.

  The image acquisition unit 34 acquires afterimage data of the previous radiographic image read from the FPD 32 at the time of non-irradiation where radiation is not applied before the next imaging. Further, the image acquisition unit 34 acquires data of the next radiation image read from the FPD 32 after the next imaging is performed. From the image acquisition unit 34, the afterimage data of the previous radiation image or the data of the next radiation image is output.

  Here, the control unit 22 may perform control so that the afterimage data of the previous radiation image is read from the FPD 32 at the timing when the imaging button is pressed to the first stage. Thereby, the time difference between the timing at which the afterimage data is acquired and the timing at which the next shooting is actually performed can be shortened. For this reason, it is possible to perform high-accuracy afterimage correction without giving the user (operator) of the photographing apparatus 10 the uncomfortable feeling of waiting time due to shot restriction.

  The first offset correction unit 36 performs offset correction on the afterimage data of the previous radiation image supplied from the image acquisition unit 34 using the offset data for afterimage data. The first offset correction unit 36 outputs afterimage data after offset correction. Further, the second offset correction unit 38 uses the offset data for the next radiation image data to offset-correct the next radiation image data supplied from the image acquisition unit 34. From the second offset correction unit 38, the next radiation image data after the offset correction is output.

  The offset component in the FPD 32 changes according to the accumulation time for accumulating charges. In the imaging apparatus 10, as described above, the accumulation time of the afterimage data read from the FPD 32 is set to a time shorter than the accumulation time of the radiographic image data at the time of imaging of the next subject H. That is, the accumulation time of afterimage data is different from the accumulation time of the next radiation image data. Therefore, it is desirable to use different offset data for the afterimage data and the next radiation image data depending on the respective accumulation times.

  The offset data is calculated in advance for each afterimage data accumulation time and each radiation image data accumulation time at the next imaging. Various methods are known for calculating the offset data, and any method may be used for the calculation.

  The afterimage amount correction unit 40 corrects the amount of decrease in the afterimage amount from the afterimage data read-out until the next shooting (the amount of attenuation of the afterimage amount over time). There is a time difference between the reading of the afterimage data and the next shooting, although it is a very short time. Since the afterimage amount decreases with time, the afterimage amount correction unit 40 supplies the afterimage amount from the first offset correction unit 36 so that the afterimage amount becomes a value corresponding to the afterimage amount when read at the next photographing time point. The corrected afterimage data after the offset correction is corrected. The afterimage amount correction unit 40 outputs afterimage data after the afterimage amount correction.

  The afterimage amount correction unit 40 performs afterimage amount correction by multiplying the afterimage data read from the FPD 32 by an afterimage amount correction coefficient α (a constant equal to or less than 1, for example, 0.9). The correction coefficient α is a numerical value determined for each FPD 32 and is calculated in advance. In order to improve the accuracy of afterimage correction, it is desirable that the change in the amount of afterimage is reduced as the afterimage data readout timing is brought closer to the next shooting timing.

  For example, the correction coefficient α is calculated as follows. That is, a predetermined amount of radiation is irradiated, a radiographic image is read from the FPD 32 at regular time intervals to acquire an afterimage amount, and a graph showing the relationship of the afterimage amount with time as shown in FIG. 3 is obtained. The curve of this graph can be expressed by, for example, a function (exp (−t / τ)). Here, t is time and τ is a time constant. Therefore, the correction coefficient α is calculated from this function based on the afterimage data read timing and the next shooting timing. The correction coefficient α is calculated in advance before actual use, for example, by shipping inspection or calibration.

  FIG. 3 is a graph showing the relationship between the elapsed time from the previous shooting and the afterimage amount. The vertical axis of the graph represents the afterimage amount of the previous radiation image, and the horizontal axis represents the elapsed time from the previous imaging. As shown in this graph, it can be seen that the afterimage amount of the previous radiation image decreases with time.

  By performing afterimage amount correction, it is possible to prevent the afterimage amount from decreasing after image data of the previous radiation image until the next subject is imaged, thereby preventing the accuracy of afterimage correction from decreasing. Can do.

  The accumulation time correction unit 42 converts the afterimage data after the afterimage amount correction supplied from the afterimage amount correction unit 40 into data corresponding to the accumulation time of the radiographic image data at the next imaging, and corrects the accumulation time. . When the accumulation time of afterimage data read from the FPD 32 is T1, and the accumulation time of radiation image data at the next imaging is T2, the accumulation time correction unit 42 accumulates the afterimage data after the afterimage amount correction. The accumulation time is corrected by multiplying the correction coefficient T2 / T1. The accumulation time correction unit 42 outputs afterimage data after the accumulation time correction.

  In the imaging apparatus 10, as described above, the afterimage data of the previous radiographic image has an accumulation time different from the accumulation time of the radiographic image data at the next imaging. For example, when the shooting mode is not the shooting mode with the shortest storage time during shooting, the control unit 22 sets the shortened storage time as the storage time during shooting in the shooting mode with the shortest storage time during shooting. To control. Alternatively, the control unit 22 controls the shortened accumulation time to be the shortest accumulation time that can be set in the radiation imaging apparatus (accumulation time shorter than the imaging mode in which the accumulation time during imaging is the shortest).

  As described above, the imaging apparatus 10 is controlled so that the afterimage data of the previous radiographic image is read from the FPD 32 with a shortened accumulation time shorter than the accumulation time at the time of imaging the next radiographic image. The afterimage amount after a certain time is in direct proportion to the accumulation time as shown in FIG. 4, and the afterimage amount after the same amount of time has elapsed after irradiation with the same dose of radiation changes according to the accumulation time. Since the image capturing apparatus 10 acquires afterimage data with a reduced accumulation time, it acquires afterimage data that is smaller than the actual afterimage amount. Therefore, the amount of change in the afterimage amount due to the difference in the accumulation time is corrected by performing the accumulation time correction.

  FIG. 4 is a graph showing the relationship between the accumulation time and the amount of afterimage after a certain time. The vertical axis of the graph represents the amount of afterimage after a certain time, and the horizontal axis represents the accumulation time. As shown in this graph, it can be seen that as the accumulation time increases, the afterimage amount after a certain time increases in proportion to the accumulation time.

  The afterimage correction unit 44 subtracts the afterimage data after the accumulation time correction supplied from the accumulation time correction unit 42 from the data of the next radiation image after the offset correction supplied from the second offset correction unit 38. Afterimage correction is performed on the radiation image.

  Next, the operation of the photographing apparatus 10 will be described. Here, referring to the graph of FIG. 3, an operation from the previous shooting to the next shooting will be described.

  As shown in the graph of FIG. 3, the amount of afterimage is reduced after the previous imaging is performed and the radiographic image data is read from the FPD 32 until the afterimage data of the previous radiographic image is acquired. For the purpose, idle reading of image data is performed at intervals of a predetermined accumulation time.

  When shooting conditions or shooting modes are set by the user in the shooting instruction unit 20 and the shooting button is pressed down to the first level, the shooting apparatus 10 is in a shooting ready state under the control of the control unit 22. As shown in the graph of FIG. 3, afterimage data of the previous radiation image is read from the FPD 32 after the shortened accumulation time after the last idle reading is performed. The shortened accumulation time is determined according to the accumulation time of the radiographic image data at the next imaging determined by the imaging condition or the imaging mode.

  The afterimage data read from the FPD 32 is subjected to processing such as A / D conversion by the photographing data processing unit 14 and supplied to the image processing unit 16. In the image processing unit 16, the afterimage data supplied from the photographic data processing unit 14 is acquired by the image acquisition unit 34, subsequently offset-corrected by the first offset correction unit 36, and afterimage amount correction by the afterimage amount correction unit 40. After that, the storage time correction unit 42 corrects the storage time.

  Subsequently, when the shooting button is pressed down to the second level, the next shooting is started as shown in the graph of FIG. When imaging is started, the imaging unit 12 emits radiation with intensity set according to imaging conditions or imaging modes from the radiation source 26 for a set time. The irradiated radiation passes through the subject H on the imaging table 28 and enters the FPD 32 of the radiation detection unit 30, and the radiation transmitted through the subject H is converted into an electrical signal (radiation image data).

  Similarly, captured radiographic image data is read from the FPD 32, processed by the imaging data processing unit 14 such as A / D conversion, and supplied to the image processing unit 16. In the image processing unit 16, the radiation image data supplied from the imaging data processing unit 14 is acquired by the image acquisition unit 34, offset-corrected by the second offset correction unit 38, and accumulated time is corrected by the afterimage correction unit 44. Afterimage correction is performed using the afterimage data.

  The radiographic image data after the afterimage correction is supplied to the output unit 18. In the output unit 18, for example, the radiographic image after the afterimage correction is displayed on a monitor, printed out from a printer, or stored in a storage device.

  The afterimage correction in the photographing apparatus 10 is performed by the following steps 1 to 5.

  In the following description, Offset1 (x, y) is afterimage data offset data for offset correction of the afterimage data of the previous radiation image. Offset2 (x, y) is offset data for the next radiation image data for offset correction of the next radiation image data. Further, the corrected image data Xdata (x, y), the afterimage data Lagdata (x, y) of the previous radiation image, the afterimage amount correction coefficient α, the afterimage data accumulation time T1, the radiographic image data at the next imaging The accumulation time T2 is as described above.

(Step 1)
As shown in the following equation (6), the afterimage data Lagdata (x, y) is offset and offset by subtracting the afterimage data offset data Offset1 (x, y) from the afterimage data Lagdata (x, y). After-correction afterimage data Data1 (x, y) is obtained.
Data1 (x, y) = Lagdata (x, y)-Offset1 (x, y) (6)

(Step 2)
As shown in the following formula (7), the afterimage data Data1 (x, y) after the offset correction is obtained by multiplying the afterimage data Data1 (x, y) after the offset correction by the afterimage amount correction coefficient α. Correction is performed to obtain afterimage data Data2 (x, y) after the afterimage complement correction.
Data2 (x, y) = α x Data1 (x, y) (7)

(Step 3)
As shown in the following equation (8), the afterimage data Data2 (x, y) after the afterimage complement correction is multiplied by the correction coefficient T2 / T1 of the accumulation time, thereby obtaining the afterimage data Data2 (x , y) is corrected for the accumulation time to obtain afterimage data (correction image data) Data3 (x, y) after the accumulation time correction.
Data3 (x, y) = Data2 (x, y) × T2 / T1 (8)

(Step 4)
As shown in the following equation (9), the corrected image data Xdata (x, y) is offset corrected by subtracting the offset correction data Offset2 (x, y) from the corrected image data Xdata (x, y). Thus, corrected image data Data4 (x, y) after offset correction is obtained.
Data4 (x, y) = Xdata (x, y)-Offset2 (x, y)… (9)

(Step 5)
As shown in the following equation (10), corrected image data Data4 (x, y) is obtained by subtracting correction image data Data3 (x, y) from corrected image data Data4 (x, y) after offset correction. ) To obtain image data Data5 (x, y) after the afterimage correction.
Data5 (x, y) = Data4 (x, y)-Data3 (x, y) (10)

In addition, since the afterimage data has many noise components, the noise component of the image data Data5 (x, y) after the afterimage correction may partially increase by performing subtraction in the afterimage correction. Therefore, as shown in the following formula (11), the image data Data5 ′ (x, y) after the afterimage correction is calculated by subtracting the median-processed correction image data median (Data3 (x, y)). Is desirable.
Data5 '(x, y) = Data4 (x, y)-median (Data3 (x, y))… (11)

  In the present invention, the afterimage amount correction is not essential, but the afterimage amount correction can improve the accuracy of the afterimage amount (correction image data), so that the afterimage correction accuracy is improved. Is also desirable. In addition, the shooting modes in which shooting conditions are set in advance are not limited to two shooting modes as in the embodiment, and any number of shooting modes may be provided as long as there are one or more shooting modes.

The present invention is basically as described above.
The radiographic imaging apparatus of the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and changes may be made without departing from the gist of the present invention. It is.

It is a block diagram of one embodiment showing composition of a radiographic imaging device of the present invention. FIG. 2 is a block diagram illustrating a configuration of an image processing unit illustrated in FIG. 1. It is a graph showing the relationship between the elapsed time from the previous photographing and the afterimage amount. It is a graph showing the relationship between accumulation | storage time and the afterimage amount after a fixed time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radiation imaging device 12 Imaging unit 14 Imaging data processing unit 16 Image processing unit 18 Output unit 20 Imaging instruction unit 22 Control unit 24 Irradiation control unit 26 Radiation source 28 Imaging stand 30 Radiation detection unit 32 FPD
34 Image acquisition unit 36 First offset correction unit 38 Second offset correction unit 40 Afterimage amount correction unit 42 Storage time correction unit 44 Afterimage correction unit

Claims (6)

A radiation image capturing apparatus that irradiates a subject with radiation from a radiation source, detects radiation transmitted through the subject with a flat panel radiation detector, and generates a radiation image in which the subject is captured,
When radiation is not irradiated before the next imaging, afterimage data of the previous radiation image read from the radiation detector is acquired, and after the next imaging is performed, the afterimage data is read from the radiation detector. An image acquisition unit for acquiring data of the next radiation image that has been issued;
A first offset correction unit for offset correction of the residual image data of the previous radiation image;
A second offset correction unit for offset correction of the data of the next radiation image;
An accumulation time correction unit that corrects the accumulation time by converting the offset-corrected afterimage data into data corresponding to the accumulation time of the radiation image data at the next imaging;
An afterimage correction unit that subtracts the afterimage data with the accumulated time corrected from the offset-corrected next radiation image data to correct the afterimage of the next radiation image;
A control unit for controlling the operation of the radiographic apparatus,
The radiographic imaging apparatus, wherein the control unit controls the afterimage data to be read from the radiation detector with a shortened accumulation time shorter than an accumulation time at the next imaging.   The first offset correction unit offset-corrects afterimage data of the previous radiation image using offset data calculated according to an accumulation time of the afterimage data of the previous radiation image, and performs the second offset. The radiographic image according to claim 1, wherein the correction unit offset-corrects the data of the next radiographic image using offset data calculated in accordance with an accumulation time of the data of the next radiographic image. Shooting device.   The image processing apparatus further includes an afterimage amount correction unit that corrects a decrease in an afterimage amount of the afterimage data that has been offset-corrected after the afterimage data is read until the next shooting is performed. The radiographic imaging device according to claim 1 or 2. The radiographic image capturing apparatus includes a plurality of radiographing modes having different accumulation times of radiographic image data at the time of radiographing,
When the shooting mode is not the shooting mode with the shortest storage time during shooting, the control unit sets the shortened storage time as the storage time during shooting in the shooting mode with the shortest storage time during shooting. The radiographic imaging apparatus according to claim 1, wherein the radiographic imaging apparatus is controlled as described above.   The radiographic imaging apparatus according to claim 1, wherein the control unit controls the shortened accumulation time to be a shortest accumulation time that can be set in the radiographic apparatus. In addition, it has a two-stage push-type shooting button to instruct shooting,
The controller reads out the afterimage data of the previous radiation image from the radiation detector at the timing when the imaging button is pressed to the first stage, and starts imaging when the second stage is pressed. The radiographic image capturing apparatus according to claim 1, wherein the radiographic image capturing apparatus is controlled as described above.

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