JP2008237445A - Method and system for radiographic imaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an accurate radiographic image all times by the appropriate treatment of residual images depending on their intensity when radiographic imaging operation is done using a flat panel detector (FPD). <P>SOLUTION: The problem can be settled by such a method that residual images are read to detect their intensity by a fixed timing, and depending on their intensity detected, the operator decides on postponing the next imaging operation, enforcing to correct the residual image or leaving it uncorrected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to radiographic imaging using a radiation solid state detector, and more particularly, a radiographic imaging method and radiographic image capable of stably capturing an accurate radiographic image by performing appropriate processing corresponding to an afterimage obtained by a previous radiographing. The present invention relates to a photographing apparatus.

Conventionally, radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.) transmitted through an object is used as an electrical signal for taking medical diagnostic images and industrial nondestructive inspections. Radiographic image detectors that capture radiographic images by taking them out are used.
Examples of the radiation image detector include a solid-state radiation detector that extracts radiation as an electrical image signal (so-called “Flat Panel Detector”, hereinafter referred to as FDP), an X-ray image tube that extracts a radiation image as a visible image, and the like. is there.

  In addition, the FPD collects electron-hole pairs (e-h pairs) emitted from a photoconductive film such as amorphous selenium upon incidence of radiation, for example, and reads them out as electrical signals. It has a direct method of conversion and a phosphor layer (scintillator layer) formed of a phosphor that emits light (fluorescence) upon incidence of radiation. The phosphor layer converts radiation into visible light, and the visible light is photoelectrically converted. There are two methods, that is, an indirect method of reading radiation with visible light and converting it into an electrical signal.

In such a radiographic image capturing apparatus using an FPD, in particular, a radiographic image capturing apparatus using a direct FPD, the previous subject image is captured as a cause of the deterioration of the image quality of the subject image (the radiographic image obtained by capturing the subject). Is an afterimage.
That is, even if a subject image is shot by exposing radiation to the FPD through the subject and an electric signal, that is, an image signal of the subject is read out from the FPD, the charge remains in the FPD. If a subject image is taken in this state, this residual charge is carried on the subject image as an afterimage, so the subject image becomes an image affected by the afterimage, and an accurate (high quality) subject image cannot be obtained.

  Therefore, in the radiographic image capturing apparatus, normally, prior to imaging of the subject, the FPD is read without exposure to radiation (that is, the dark image (afterimage) is read), and the subject image (subject image signal) By subtracting the dark image (dark image signal), so-called afterimage correction that eliminates the adverse effects of the afterimage of the previous shooting is performed.

Further, the afterimage attenuates with time.
Patent Document 1 uses this to read a dark image of an FPD, and wait for shooting until the dark image signal falls below an allowable value, thereby obtaining a high-quality subject image free from the adverse effects of afterimages. Is disclosed.

JP 2005-28113 A

However, since such afterimage correction is correction for subtracting the dark image from the subject image, the S / N ratio of the obtained radiographic image decreases.
In particular, when the exposure amount of the previous photographing is large or the elapsed time from the photographing is short, a large charge remains in the FPD, that is, the dark image becomes very large (high Intensity signal). In such a case, since a large dark image is subtracted from the subject, the subject image becomes an image with a low S / N ratio and deteriorated in image quality, that is, a high-quality subject image is obtained. Absent.

  Further, with the method disclosed in Patent Document 1, it is possible to obtain a subject image that is not affected by an afterimage, but it is necessary to wait for radiographic imaging depending on the dark image, that is, the state of the afterimage. In particular, when the exposure amount of the previous imaging is large, it takes time to attenuate the dark image, so it is necessary to wait for a long time to capture the radiographic image, which makes it impossible to perform efficient imaging and diagnosis. There is a possibility.

  An object of the present invention is to solve the problems of the prior art, and in radiographic imaging using a radiation solid state detector (FPD), an appropriate countermeasure can be taken according to the state of an afterimage. A radiographic imaging method capable of significantly reducing the adverse effects of radiographic images and enabling rapid radiographic imaging independent of afterimages as needed, and a radiographic imaging apparatus for performing this radiographic imaging method It is to provide.

  In order to achieve the above object, the radiographic image capturing method of the present invention detects the afterimage amount of the radiation solid detector at a predetermined timing, and sets the first threshold value TH1 and the second threshold value that are set in advance prior to radiographic image capturing. The threshold TH2 (where TH1> TH2) is compared with the afterimage amount. If afterimage amount ≧ TH1, the radiographic image capturing is waited, and if TH1> afterimage amount> TH2; Takes the radiographic image, performs afterimage correction on the taken radiographic image, and in the case of TH2 ≧ afterimage amount, the radiographic image is taken and the afterimage correction is performed on the radiographic image taken. Provided is a radiographic image capturing method characterized in that it is not performed.

  In such a radiographic image capturing method of the present invention, both the first threshold value TH1 and the second threshold value TH2 are used, and a high image quality process for comparing with the afterimage amount, and the second threshold value TH2 When the high-speed processing is selected, the radiographic image is captured when the after-image amount> TH2; In the case of TH2 ≧ afterimage amount; preferably, the radiographic image is captured and the afterimage correction is not performed on the captured radiographic image. The afterimage amount is preferably the intensity of the dark image.

  The radiographic imaging device of the present invention includes a radiation source, a radiation solid detector that detects radiation irradiated by the radiation source, and an afterimage detection unit that detects an afterimage amount from the radiation solid detector at a predetermined timing. And an afterimage correction unit that performs afterimage correction on the radiation image detected by the radiation solid state detector, and an afterimage amount detected by the afterimage detection unit. The threshold TH1 and the second threshold TH2 (where TH1> TH2) are compared with the afterimage amount, and an instruction for exposure to the radiation source and an instruction for afterimage correction to the afterimage correction means are performed. The signal intensity determining means. When the afterimage amount ≧ TH1, the signal intensity determining means issues an exposure standby instruction to the radiation source, and when TH1> afterimage amount> TH2; The source In the case of giving permission for exposure and instructing the afterimage correction means to perform afterimage correction on the radiation image detected by the radiation solid state detector, and TH2 ≧ afterimage amount; The radiation image photographing apparatus is characterized in that an exposure permission is issued and an instruction is issued to the afterimage correction means not to perform afterimage correction on the captured radiation image.

  In such a radiographic image capturing apparatus of the present invention, both the first threshold value TH1 and the second threshold value TH2 are used to make a comparison with the afterimage amount and to instruct the exposure to the radiation source. In addition, the process for instructing the afterimage correction unit to perform afterimage correction is set as a high image quality mode, and the signal intensity determination unit uses only the second threshold TH2 in addition to the high image quality mode, A high-speed mode is set in which an instruction for exposure to the radiation source and an instruction for afterimage correction to the afterimage correction means are performed by comparing with the amount of afterimage, and the high image quality mode and the high speed mode are set. In the high-speed mode, the signal intensity judging means gives an exposure permission to the radiation source when the afterimage amount> TH2; and the afterimage correcting means The radiation solid state detector In the case of TH2 ≧ afterimage amount, the radiation source is permitted to be exposed, and the afterimage correction unit is configured to perform the afterimage correction on the captured radiation image. It is preferable to instruct not to perform afterimage correction, and it is preferable that the amount of afterimage is the intensity of a dark image.

  In such a radiographic image capturing method and radiographic image capturing apparatus of the present invention, it is preferable that the intensity of the dark image is an average value of the dark image, or the intensity of the dark image is the maximum value of the dark image. Further, it is preferable that the afterimage amount is detected in a predetermined region of a dark image.

According to the present invention having the above-described configuration, the predetermined threshold TH1 and threshold TH2 (where TH1> TH2) for the afterimage amount such as the intensity of the dark image (the intensity of the dark image signal) are determined, and in accordance with the threshold It is determined whether to perform non-permission of radiographic imaging (exposure), radiographic imaging with afterimage correction, or radiographic imaging without afterimage correction. Therefore, according to the present invention, it is possible to perform the most appropriate processing according to the amount of afterimage, that is, the state of the afterimage, and to stably capture an accurate (high image quality) radiographic image with greatly reduced influence of the afterimage. Can be done.
In addition, as a preferable aspect, the image processing apparatus has a high image quality mode capable of capturing the high image quality radiation image and a high speed mode permitting image capturing regardless of the afterimage amount. Even in the high speed mode, the afterimage correction is performed according to the afterimage state. Determine the presence or absence. Therefore, according to the present invention, even in the case of an emergency or when it is necessary to continuously capture a large number of radiographic images, radiographic images can be captured promptly and with the maximum adverse effects of afterimages being eliminated. it can.

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

FIG. 1 conceptually shows an example of a radiographic image capturing apparatus of the present invention that implements the radiographic image capturing method of the present invention.
A radiographic image capturing apparatus 10 (hereinafter referred to as an imaging apparatus 10) illustrated in FIG. 1 is a radiographic image diagnostic apparatus that captures a radiographic image (diagnostic image) of a subject H (subject), and captures a radiographic image. The imaging unit 12 includes an image processing unit 14 that processes a subject image captured by the imaging unit 12, a monitor 16, and a printer 18. The photographing apparatus 10 may be connected to an external apparatus or system such as a management system or an image server through a known communication network.

The imaging unit 12 is a part that captures a radiation image of the subject H (hereinafter referred to as a subject image), and includes an exposure control unit 20, a radiation source 22, an imaging table 24, and an imaging unit 26. Composed.
The exposure control means 20 has a high-voltage power source for irradiating radiation from the radiation source 22, and drives the radiation source 22 to irradiate radiation with a set intensity for a set time. 22 control means. The radiation source 22 is also a normal radiation source installed in various radiographic imaging devices.
The imaging table 24 is also a normal imaging table that is used in various radiographic imaging devices. Note that the imaging apparatus 10 may include a moving unit for the radiation source 22, a lifting unit for the imaging table 24, a moving unit for moving in the horizontal direction, a tilting unit for tilting the imaging table 24, and the like, as necessary.

The photographing means 26 photographs a subject image by a radiation fixed detector 30 (hereinafter referred to as FPD 30).
As with the normal radiographic imaging apparatus 10, the imaging apparatus 10 receives the radiation irradiated by the radiation source 22 and transmitted through the subject H by the light receiving surface of the FPD 30, and photoelectrically converts the radiation by the FPD 30, thereby subject image. Shoot.

In the present invention, the FPD 30 is a normal FPD (Flat Panel Detector) used in a radiographic imaging apparatus.
In the present invention, various types of FPD 30 can be used. Therefore, a photoconductive film such as amorphous selenium and a TFT (Thin Film Transistor) are used to collect electron-hole pairs (e-h pairs) emitted from the photoconductive film by the incidence of radiation and use the TFT as an electrification signal. Even in a so-called direct FPD that reads out, a scintillator layer formed of a phosphor that emits light (fluorescence) such as “CsI: Tl”, a photodiode, a TFT, and the like, and light emission of the scintillator layer by incidence of radiation. Alternatively, a so-called indirect FPD may be used in which the signal is photoelectrically converted by a photodiode and read out as an electrical signal by a TFT.
Note that the direct FPD is particularly preferable in that it is easily affected by the residual image, that is, the residual charge of the previously captured subject image, and the effects of the present invention can be obtained more suitably.

  In addition to the FPD 30, the imaging unit 26 may include various members included in a known radiographic imaging device such as a grid for shielding scattered radiation incident on the FPD 30, a grid moving unit, and the like. Of course it is good.

An output signal of the radiographic image captured by the imaging unit 26 (FPD 30) is output to the image processing unit 14.
The image processing unit 14 processes the output signal output from the FPD 30 and corresponds to display on the monitor 16, print output on the printer 18, and output of a radiographic image (data) using a network or a recording medium. A subject image (image signal (image data)) is used. In the illustrated imaging apparatus 10, the image processing unit 14 includes a data processing unit 32, an image processing unit 34, a dark image acquisition unit 36, and a radiation intensity determination unit 38.
As an example, the image processing unit 14 is configured by one or a plurality of computers and workstations. In addition to the illustrated parts, a keyboard, a mouse, and the like for inputting various operations and instructions are provided. have.

  The data processing means 32 performs processing such as A / D conversion and log conversion on the output signal of the FPD 30 to convert it into an image signal (image data) of the subject image, and obtains a dark image acquisition means 36 (dark image) and an image. This is supplied to the processing means 34 (subject image).

The dark image acquisition unit 36 reads the dark image of the FPD 30.
That is, the dark image acquisition unit 36 reads the output signal of the FPD 30 in a state where no radiation is emitted from the radiation source 22, that is, in a state where no radiation is exposed to the FPD 30, and this output signal is read by the data processing unit 32. Processing is performed to read out a dark image (dark image signal) of the FPD 30. Further, the dark image acquisition unit 36 supplies the read dark image to the image processing unit 34 and the radiation intensity determination plan unit 38.

The imaging apparatus 10 in the illustrated example performs calibration at the time of activation, similarly to a normal radiographic imaging apparatus. In this example, as an example, an offset image for offset correction is read, a radiographic image for gain correction (shading correction) is taken, and a pixel defect map for pixel defect correction is created by calibration.
The dark image acquisition unit 36 reads a dark image at the time of activation and supplies it to the image processing unit 34 as an offset image for offset correction.

  In the illustrated imaging apparatus 10, the intensity Sd of the dark image of the FPD 30 is used as an afterimage amount for determining whether exposure is permitted / standby or whether or not afterimage correction is necessary. Correspondingly, the dark image acquisition means 36 reads the dark image at a predetermined timing after the imaging device 10 is activated, and determines the radiation intensity as a dark image (afterimage) for afterimage amount detection and afterimage correction. This is supplied to the means 38 and the image processing means 34.

The timing for reading out the dark image is not particularly limited, and is read out at a predetermined cycle after shooting, such as before shooting a subject image (for example, when shooting a subject) or every 0.5 to 5 minutes after shooting. What is necessary is just to set suitably according to the imaging | photography space | interval of a to-be-photographed image, the imaging frequency, etc. by the imaging device 10. FIG.
Note that in a normal radiographic image capturing apparatus, the capturing menu of the subject image captured first is already known, and the imaging region and the exposure dose can be known from the capturing menu. Using this, when a dark image is periodically read out after imaging, the period may be changed according to the radiation exposure amount and imaging region in the previous imaging.
Moreover, in the general radiation source 22, when the radiation exposure switch is pressed one stage (once or exposure preparation switch), it becomes ready (exposure preparation), and the second stage (second time or exposure switch) is reached. In many cases, exposure (radiation of radiation) is caused by pressing. This may be used to read a dark image when the switch is pressed one step.

  The radiation intensity determination means 38 (hereinafter referred to as intensity determination means 38) detects the dark image intensity Sd (the signal intensity Sd of the dark image signal) as the afterimage amount from the dark image read by the dark image acquisition means 36. The threshold values TH1 and TH2 (TH1> TH2) set in advance and the intensity Sd of the dark image are compared, and the exposure control means 20 is allowed to permit exposure or exposure according to the comparison result. A shooting standby instruction is issued, and an after-image correction necessity / unnecessary instruction is issued to the image processing means 34 (after-image correction means 42 described later).

Specifically, as schematically illustrated in FIG. 2A, when the dark image intensity Sd is equal to or greater than the (first) threshold TH1 [Sd ≧ TH1], the dark image, that is, the afterimage is large. (The signal strength of dark images is high).
Therefore, in this case, even if the subject image is shot and the afterimage correction is performed, only the subject image having a low S / N ratio and degraded in image quality can be obtained. The means 20 is instructed to wait for exposure (standby for photographing the subject image). That is, at this time, even if an imaging instruction is issued by an engineer or the like by pressing the exposure switch, the imaging device 10 does not capture the subject image. In addition, it is preferable that the photographing apparatus 10 informs that the afterimage is large by displaying on the monitor 16 or generating a warning sound. Further, in this case, the intensity determination unit 38 instructs the image processing unit 34 to discard this dark image.
When the dark image acquisition means 36 reads out a dark image using the pressing of the exposure switch, if [Sd ≧ TH1], the exposure switch is locked so that it cannot be pressed up to the second stage. It is also preferable to make it.

In addition, when an exposure standby is issued with [Sd ≧ TH1], the intensity determination unit 38 sends the exposure control unit 20 after a predetermined time, preferably after a predetermined time corresponding to the intensity Sd. An instruction for permitting exposure is issued, and the image capturing apparatus 10 captures a subject image.
Alternatively, when the dark image intensity Sd by the dark image acquisition unit 36 becomes equal to or less than a predetermined value (TH1 or less, or TH2 or less), the exposure control unit 20 is instructed to permit exposure, and the photographing apparatus 10 The subject image is taken.
At this time, the presence or absence of afterimage correction may be determined according to the following judgment.

As schematically shown in FIG. 2B, when the intensity Sd of the dark image is [TH1>Sd> TH2] between the threshold value TH1 and the (second) threshold value TH2, a certain amount of afterimage is obtained. Although it remains, by performing afterimage correction, an accurate (high quality) subject image can be obtained.
Therefore, in this case, the intensity determination unit 38 gives exposure permission (subject image capturing permission) to the exposure control unit 20, and further causes the image processing unit 34 (afterimage correction unit 42) to capture the captured subject image. Is instructed to perform afterimage correction using this dark image (dark image from which the intensity Sd is detected). That is, at this time, the photographing apparatus 10 shoots a subject image in accordance with a photographing instruction from an engineer or the like, and outputs a subject image that has been subjected to afterimage correction using the dark image (offset correction using an offset image is performed). Not done).

As schematically shown in FIG. 2C, when the intensity Sd of the dark image is equal to or less than the threshold value TH2 [TH2 ≧ Sd], the amount of afterimage is sufficiently small and no afterimage correction is necessary.
Therefore, in this case, the intensity determination means 38 gives exposure permission to the exposure control means 20, and further instructs the image processing means 34 not to perform the afterimage correction using this dark image. . That is, at this time, the photographing apparatus 10 shoots a subject image in accordance with a photographing instruction from an engineer or the like, and outputs a subject image that has been offset-corrected by an offset image without performing afterimage correction by the dark image. To do.

  In the present invention, the dark image intensity Sd is not particularly limited, and various signal intensities can be used. As an example, the average value of dark images (the average value of dark image signals (image data)), the maximum value of dark images, the minimum value of dark images, the intermediate value of dark images, and the predetermined cumulative percentage point of the signal value histogram of dark images In particular, the average value of the dark image and the maximum value (maximum value) of the dark image are preferably used.

The threshold value TH1 and the threshold value TH2 are not particularly limited. The image quality required for the subject image, the processing capability required for the imaging device 10 (such as the number of images taken per unit time), the use of the imaging device such as the main imaging region, What is necessary is just to set suitably according to the imaging frequency, the frequency of emergency imaging, etc.
Further, for example, when the exposure amount is large in the current shooting (to be performed in the future), both threshold values are slightly increased, and when the exposure amount is small in the current shooting, both threshold values are slightly decreased. TH1 and / or threshold value TH2 may be appropriately changed according to imaging conditions (imaging site, radiation exposure dose, etc.). In this case, the threshold value may be changed in consideration of only the previous shooting condition, the threshold value may be changed only in consideration of the current shooting condition, and both the previous and current shooting conditions are considered. The threshold value may be changed. Such a change of the threshold value may be performed using, for example, a table (LUT) indicating the relationship between the photographing condition and the threshold value created in advance.

The area of the dark image (light receiving surface of the FPD 30) for detecting the intensity Sd (afterimage amount) of the dark image is not particularly limited, and may be the entire surface of the dark image, or a predetermined area at the center of the dark image, etc. It may be a predetermined area in a dark image set in advance.
In the case where the intensity Sd is detected in a predetermined area of the dark image, the area may be set as appropriate according to the part or the like mainly imaged by the imaging apparatus 10.

Further, as described above, in a normal radiographic image capturing apparatus, the capturing menu of the subject image captured first is already known, and the imaging region and the exposure dose can be known from the capturing menu.
Using this, when detecting the intensity Sd in a predetermined area of the dark image, the position of the area in which the intensity Sd is detected may be changed according to the previously captured subject image. In this case, for example, an area where the dark image is predicted to be the largest (the intensity of the dark image signal is high), or an area where the dark image is predicted to be average, Alternatively, the area where the dark image is read is changed to an area where the dark image is predicted to be the smallest.
Furthermore, when changing the position of the area where the intensity Sd of the dark image is detected, the size of the detection area of the intensity Sd may be changed according to the previously captured subject image.

Here, as a preferable aspect, the image capturing apparatus 10 in the illustrated example is set with the high-quality mode and the high-speed mode in the intensity determination unit 38, and the image capturing apparatus 10 further includes a mode selection unit. Yes. Note that the mode selection means may be realized by a known means using a GUI (Graphical User Interface) or the like.
In the high image quality mode, the above-described two threshold values TH1 and TH2 are used to compare the intensity of the dark image intensity Sd, and [Sd ≧ TH1], [TH1>Sd> TH2], [TH2 ≧ Sd] is a mode for determining whether exposure permission / standby and afterimage correction are necessary / unnecessary.
On the other hand, the high-speed mode is a mode in which exposure is always permitted and only necessity / unnecessity of afterimage correction is determined using only the threshold value TH2.

Specifically, in the high-speed mode, as schematically shown in FIG. 2D, when the intensity Sd of the dark image is equal to or higher than the threshold value TH2 [Sd> TH2], the intensity determination unit 38 performs exposure. The exposure control unit 20 is given exposure permission, and the image processing unit 34 is instructed to perform afterimage correction using the dark image on the photographed subject image.
Further, as schematically shown in FIG. 2E, when the dark image intensity Sd is equal to or lower than the threshold TH2 [TH2 ≧ Sd], the intensity determining unit 38 performs the exposure similarly to the high-speed mode. An exposure permission is issued to the control unit 20, and an instruction is issued to the image processing unit 34 so as not to perform the afterimage correction using the dark image.
In the case of the high-speed mode, the intensity determination unit 38 may not always instruct the exposure permission, but the imaging apparatus 10 may be always in the exposure permission state.

  In other words, in the high-speed mode, the exposure permission is issued regardless of the state of the dark image (afterimage), so there is no exposure standby in an emergency or when it is necessary to continuously capture a large number of subject images. Enables rapid shooting of subject images, and when dark images are large, afterimage correction is performed to output subject images with as little influence as possible, and when dark images are sufficiently small The image is output without performing afterimage correction.

As is clear from the above description, according to the present invention, according to the afterimage amount (size of afterimage), when an accurate subject image cannot be obtained, the exposure is waited for and an accurate subject is obtained by afterimage correction. When an image is obtained, afterimage correction is performed, and when the afterimage is sufficiently small, afterimage correction that causes a decrease in the S / N ratio is not performed. A stable subject image can be obtained stably.
Furthermore, preferably, by having a high-speed mode, it is possible to quickly capture a subject image even in an emergency or when it is necessary to continuously capture a large number of radiation images, and according to the amount of afterimage Thus, afterimage correction is performed by determining the necessity / unnecessity of afterimage correction, so that it is possible to obtain a subject image that eliminates the adverse effects of the afterimage to the maximum extent.

The subject image captured by the FPD 30 and processed by the data processing unit 32 is supplied to the image processing unit 34.
The image processing unit 34 performs predetermined image processing on the subject image processed by the data processing unit 32 to display an image on the monitor 16 or the like, to output a print (hard copy) by the printer 18, or to output to a network or a storage medium. The corresponding subject image (image signal (image data)) is used.
In the present invention, the image processing unit 34 uses the offset image and the dark image read out by the dark image acquisition unit 36 and performs either offset correction or afterimage correction according to the determination by the intensity determination unit 38 described above. Afterimage correction means 42 is provided.

Note that the image processing performed by the image processing unit 34 is not limited to the offset correction and the afterimage correction performed by the afterimage correcting unit 42.
The image processing performed by the image processing unit 34 includes, for example, pixel correction, gain correction (shading correction), gradation correction, density correction, and monitor display and print output performed according to calibration together with offset correction. All image processing performed in various types of radiographic imaging devices, such as data conversion for converting image data into data for use, can be performed.

The afterimage correction means 42 performs offset correction or afterimage correction on the subject image (the captured radiographic image of the subject H).
There are no particular limitations on the offset correction and afterimage correction methods, and various methods using an offset image and a dark image, which are performed in a known radiographic image capturing apparatus, can be used.
As an example, the offset correction is exemplified by a method of subtracting an offset image (a dark image read when the photographing apparatus 10 is activated) by the dark image acquisition unit 36 from the subject image. The dark image correction is exemplified by a method of subtracting a dark image, that is, an afterimage (dark image signal (afterimage signal)) by the dark image acquisition unit 36 from the subject image (subject image signal).

  When the afterimage correction unit 42 receives an instruction not to perform afterimage correction in response to an instruction from the intensity determination unit, the afterimage correction unit 42 performs an offset correction on the subject image and does not perform afterimage correction, but issues an instruction to perform afterimage correction. If received, afterimage correction is performed on the subject image and no offset correction is performed.

Hereinafter, the operation of the photographing apparatus 10 will be described.
When the photographing apparatus 10 is activated, calibration is performed when the apparatus is stabilized in a predetermined state, and the dark image acquisition unit 36 reads a dark image from the FPD 30.
That is, the dark image acquisition means 36 reads out the output signal of the FPD 30 in a state where no radiation is exposed, causes the data processing means 32 to process it, reads out a dark image (dark image signal), and uses this dark image as an offset image. To the image processing means 34 (afterimage correction means 42).

When the photographing apparatus 10 is activated and the subject image is ready to be photographed, the dark image acquisition unit 36 reads the dark image of the FPD 30 at a predetermined timing as described above, and uses the read dark image as an intensity determination unit. 38 and the image processing means 34 (afterimage correction means 42).
When the dark image is supplied from the dark image acquisition unit 36, the intensity determination unit 38 detects the intensity Sd of the dark image. In the high image quality mode, the intensity determination unit 38 compares the threshold value TH1 and the threshold value TH2 as described above. In addition, according to whether [Sd ≧ TH1], [TH1>Sd> TH2], or [TH2 ≧ Sd], the exposure control unit 20 is instructed to wait for exposure / permission, and the afterimage correction unit 42. Indication of whether or not afterimage correction is necessary.
In the case of the high-speed mode, as described above, the afterimage correction means 42 is instructed whether or not afterimage correction is necessary according to whether [Sd ≧ TH2] or [TH2> Sd]. In the high-speed mode, as described above, the exposure is always permitted.

  In such a state, when the subject H gets on the photographing stand 24, preparation for photographing the subject image is completed, and an instruction to photograph the subject image (such as pressing an exposure switch) is issued from an engineer or the like, the exposure control means A radiation exposure instruction is issued at 20. Here, the exposure control means 20 does not drive the radiation source 22 (radiation emission) when the intensity determination means 38 gives an instruction to wait for exposure (standby for imaging), and the imaging apparatus 10 Do not shoot images (standby for shooting).

On the other hand, when an instruction for permitting exposure (permitting imaging) is issued from the intensity determining unit 38, the exposure control unit 20 drives the radiation source 22 in response to the imaging instruction, and the imaging apparatus 10. Takes a subject image.
Radiation emitted from the radiation source 22 and transmitted through the subject H enters the FPD 30 and a subject image is photographed. An output signal of the FPD 30 is output to the data processing unit 32. The data processing unit 32 performs processing such as A / D conversion and log conversion on the output signal from the FPD 30 and outputs the subject image (subject image signal (image data)) to the image processing unit 34.

The image processing unit 34 performs predetermined processing such as pixel defect correction, gain correction, and gradation conversion on the photographed subject image, and the monitor 16, the printer 18, or the photographing device 10 serves as an output subject image. Output to connected network.
Here, the afterimage correction unit 42 of the image processing unit 34 does not perform the offset correction when the instruction to perform the afterimage correction is issued according to the instruction from the intensity determination unit 38, and first obtains the dark image. The afterimage correction is performed by subtracting the dark image (afterimage) supplied from the means 36 from the subject image. On the other hand, the afterimage correction unit 42 does not perform afterimage correction when an instruction not to perform afterimage correction is issued from the intensity determination unit 38, and uses the offset image supplied from the dark image acquisition unit 36 at the time of calibration. Offset correction is performed by subtracting from the subject image.

  The radiographic image capturing method and radiographic image capturing apparatus of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, you can do it.

It is a block diagram which shows an example conceptually in the radiographic imaging device of the present invention. (A), (B), (C), (D), and (E) are conceptual diagrams for explaining dark image intensity determination in the radiographic imaging device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 (Radiation image) imaging device 12 Imaging part 14 Image processing part 16 Monitor 18 Printer 20 Exposure control means 22 Radiation source 24 Imaging stand 26 Imaging means 30 FPD (radiation solid state detector)
32 Data processing means 34 Image processing means 36 Dark image acquisition means 38 (Dark image) intensity determination means 42 Afterimage correction means

Claims (9)

The afterimage amount of the radiation solid detector is detected at a predetermined timing, and the first threshold value TH1 and the second threshold value TH2 (TH1> TH2) set in advance prior to the radiographic image capturing, and the afterimage amount are obtained. Compared to,
In the case of afterimage amount ≧ TH1;
In the case of TH1> afterimage amount> TH2, the radiographic image is captured, the afterimage correction is performed on the captured radiographic image,
In the case of TH2 ≧ afterimage amount; a radiographic image capturing method, wherein the radiographic image is captured, and afterimage correction is not performed on the captured radiographic image. A high image quality process that uses both the first threshold value TH1 and the second threshold value TH2 to compare with the afterimage amount;
Using only the second threshold TH2 and selecting either high-speed processing for comparison with the afterimage amount;
When selecting the high-speed processing,
In the case of afterimage amount> TH2, the radiographic image is captured, the afterimage correction is performed on the captured radiographic image,
2. The radiographic image capturing method according to claim 1, wherein in the case of TH2 ≧ afterimage amount, the radiographic image is captured, and no afterimage correction is performed on the captured radiographic image.   The radiographic image capturing method according to claim 1, wherein the afterimage amount is intensity of a dark image. A radiation source;
A radiation solid detector for detecting radiation irradiated by the radiation source;
Afterimage detection means for detecting an afterimage amount at a predetermined timing from the radiation solid detector;
Afterimage correction means for performing afterimage correction on the radiation image detected by the radiation solid detector;
Using the afterimage amount detected by the afterimage detection means, the first threshold value TH1 and the second threshold value TH2 (TH1> TH2) set in advance are compared with the afterimage amount prior to radiographic image capturing. A signal intensity determining means for instructing the exposure to the radiation source and for giving an afterimage correction instruction to the afterimage correction means,
And this signal strength judgment means is
In the case of afterimage amount ≧ TH1, the exposure instruction is given to the radiation source,
In the case of TH1> afterimage amount> TH2, the exposure permission is given to the radiation source, and the afterimage correction unit is instructed to perform afterimage correction on the radiation image detected by the radiation solid detector. Take out
In the case of TH2 ≧ afterimage amount; the exposure permission is given to the radiation source, and the afterimage correction unit is instructed not to perform afterimage correction on the captured radiation image. Radiation imaging device. Using both the first threshold value TH1 and the second threshold value TH2, a comparison is made with the afterimage amount, an instruction for exposure to the radiation source, and afterimage correction to the afterimage correction means. The instruction processing is set to the high image quality mode.
In addition to the high image quality mode, the signal intensity determination means uses only the second threshold value TH2, compares it with the afterimage amount, and instructs the exposure to the radiation source, and A high-speed mode for instructing afterimage correction to the afterimage correction means is set, and further includes a selection means for selecting the high image quality mode and the high speed mode,
In the high-speed mode, the signal strength determination means is
In the case of afterimage amount> TH2, the exposure permission is given to the radiation source, and the afterimage correction means is instructed to perform afterimage correction on the radiation image detected by the radiation solid detector. ,
5. In the case of TH2 ≧ afterimage amount, the exposure permission is given to the radiation source, and the afterimage correction unit is instructed not to perform afterimage correction on the captured radiation image. Radiographic imaging device.   The radiographic image capturing apparatus according to claim 4, wherein the afterimage amount is a dark image intensity.   The radiographic image capturing apparatus according to claim 6, wherein the intensity of the dark image is an average value of the dark image.   The radiographic image capturing apparatus according to claim 6, wherein the intensity of the dark image is a maximum value of the dark image.   The radiographic imaging device according to claim 4, wherein the afterimage amount is detected in a predetermined region.

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