JP4908283B2 - Radiation image capturing apparatus and pixel defect information acquisition method - Google Patents

Description

  The present invention relates to radiographic imaging using a fixed radiation detector, and more particularly to a radiographic imaging apparatus and pixel defect information acquisition method for acquiring pixel defect position information of a fixed radiation detector.

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.
As this radiation image detector, a radiation solid state detector (so-called “Flat Panel Detector”, hereinafter referred to as “FPD”) that extracts radiation as an electrical image signal, or an X-ray image tube that extracts a radiation image as a visible image. and so on.

  As a method of using FPD for a radiation image detector, for example, electron-hole pairs (e-h pairs) emitted from a photoconductive film such as amorphous selenium by the incidence of radiation are collected and read out as an electric signal. It has a direct system that directly converts it into an electrical signal and a phosphor layer (scintillator layer) that is made of phosphor that emits light (fluoresce) when incident radiation is applied. This phosphor layer converts radiation into visible light. There are two methods of reading out this visible light with a photoelectric conversion element, that is, an indirect method of converting radiation into an electric signal as visible light.

In the radiographic imaging apparatus using this FPD, a pixel defect of the FPD is cited as one cause of the deterioration of the image quality of the radiographic image.
In other words, not all FPD pixels (detecting elements) output signals with appropriate intensity with respect to incident radiation (radiation dose), but signals with abnormally low values or higher than radiation. There are pixels that output signals.

As a matter of course, an appropriate radiation image cannot be obtained in a portion (pixel) in which a pixel defect occurs. An image having such a defect causes a serious problem such as misdiagnosis. Further, the pixel defect of FPD cannot prevent the increase with time.
Therefore, in a radiographic imaging apparatus using FPD, the position of a pixel defect of FPD is detected at a predetermined timing, and when a radiographic image is captured, peripheral pixels ( It has been proposed to correct pixel defects by using the image data), to perform pixel defect correction, and to display a radiation image that has been corrected for pixel defects as a diagnostic image or the like as a display or print.
As a method for detecting a pixel defect of such an image sensor, there is a method described in Patent Document 1.

In US Pat. No. 6,057,031, a digital detector comprising an X-ray source and pixel elements arranged in rows and columns and a use operation phase during which the detector is calibrated during a calibration operation phase and occurs at different times. Describes an X-ray imaging system having a monitoring device for monitoring the detector using a controller that powers the detector.
Further, the monitoring device reads the data generated by the pixel elements, analyzes the data, and corresponds to data indicating defective pixel elements during the calibration operation phase and during a predetermined portion of the multiple use operation phases. The identification of pixel elements is also described.

JP 2003-198937 A

As described in Patent Document 1, pixel defect information can be obtained by periodically performing pixel defects during the use operation as well as during the calibration operation, and updating information related to the pixel defect.
However, in the radiation solid state detector, the number and position of the pixel defects change depending on the use situation, so that there are some pixel defects that are not detected. In addition, the pixel defect can be accurately detected by shortening the time interval and frequently detecting the pixel defect. However, the operation is complicated and the addition to the apparatus is increased.

  An object of the present invention is to obtain an appropriate radiographic image by correcting pixel defects of the FPD in radiographic imaging using a radiation solid state detector (FPD). Further, the pixel defects of the FPD increase with time. Therefore, it is an object of the present invention to provide a radiographic image capturing apparatus and a pixel defect information acquisition method capable of appropriately grasping a pixel defect occurrence state and obtaining a radiographic image capable of proper diagnosis and the like.

In order to solve the above problems, a first aspect of the first aspect of the present invention includes a radiation source,
A radiation solid detector for detecting radiation irradiated by the radiation source;
A defect detection means for detecting pixel defect position information of the radiation fixed detector;
Control means for controlling the timing at which the defect detection means detects pixel defect position information;
Having at least one of an exposure dose measuring means for measuring an exposure dose irradiated to the radiation fixed detector and a temperature measuring means for measuring the temperature of the radiation fixed detector;
The control means includes a pixel by the defect detection means based on at least one of a measurement result of the exposure dose measurement means and a measurement result of the temperature measurement means, and an elapsed time after the pixel defect is detected by the defect detection means. Provided is a radiographic imaging apparatus that calculates timing for detecting defect position information.

Here, the control means includes at least one of a temperature change, a cumulative exposure dose, a single exposure dose, and a pixel defect of the fixed radiation detector after pixel defect position information is detected by the defect detection means. Detecting an elapsed time since the position information was detected, and when at least one of the detected temperature change, the cumulative exposure dose, the single exposure dose, and the elapsed time exceeds an allowable value, It is preferable to detect pixel defect position information by the defect detection means.
Moreover, when the said control means detects the request | requirement of an image photography, it is preferable to wait for the detection of the pixel defect position information by the said defect detection means.
The control means further is detecting the pixel defect position information by the closing process during the defect detection means, the closing process startup after detecting the pixel defect position information when the pixel defect position by the defect detecting means It is preferable not to detect information.
Here, the end-of-work process is a process performed before the operation of the apparatus is stopped or stopped.

The control means may set an allowable value for the elapsed time based on at least one of the cumulative exposure dose measured by the exposure dose measurement means and the temperature detected by the radiation fixed detector. preferable.
Further, it is preferable that the defect detection means obtains new pixel defect position information by taking a logical sum of the pixel defect detected at the time of update and the pixel defect of the pixel defect position information before update.

In order to solve the above problems, a second form of the first aspect of the present invention includes a radiation source,
A radiation solid detector for detecting radiation irradiated by the radiation source;
A defect detection means for detecting pixel defect position information of the radiation fixed detector;
Control means for controlling the timing at which the defect detection means detects pixel defect position information;
Said control means, by detecting the pixel defect position information by the closing process during the defect detection means, and, when starting after the pixel defect position information is detected by the defect detecting means during the closing process, the defect detection Provided is a radiographic imaging apparatus that does not detect pixel defect position information by means.

In order to solve the above problem, a first aspect of the second aspect of the present invention is a pixel defect information acquisition method for acquiring pixel defect position information of a radiation fixed detector,
Elapsed time since the detection of the pixel defect position information, and temperature change, cumulative exposure dose, and single exposure dose of the radiation fixed detector since the detection of the pixel defect position information Detect one,
Pixel defect information for updating pixel defect position information of the radiation fixed detector when any one of the detected elapsed time, temperature change, cumulative exposure dose, and single exposure dose exceeds a set value Provide an acquisition method.

In order to solve the above-mentioned problem, a second aspect of the second aspect of the present invention is a pixel defect information acquisition method for acquiring pixel defect position information of a fixed radiation detector,
Based on at least one of the temperature of the radiation fixed detector and the radiation dose of the radiation detector, the update time interval of the pixel defect position information of the radiation fixed detector is set,
Compare the elapsed time since the detection of the pixel defect position information and the update time interval,
When the elapsed time exceeds the update time interval, a pixel defect information acquisition method for acquiring pixel defect position information of the radiation fixed detector and updating the pixel defect position information is provided.

According to the present invention, it is possible to appropriately acquire pixel defect position information according to usage conditions and characteristics. Thereby, a pixel defect can be corrected appropriately and a high-quality image can be formed.
In addition, according to the present invention, it is possible to appropriately detect the pixel defect by detecting the pixel defect position information at the time of the end-of-day process, and further, by not detecting the pixel defect position information in the startup process, The required time can be shortened. As a result, it is possible to use the apparatus in a shorter time after activation, and it is possible to form a high-quality image.

  A radiographic imaging apparatus and a pixel defect information acquisition method according to the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of a radiographic image capturing apparatus using the pixel defect information acquisition method of the present invention.
A radiographic image capturing apparatus 10 (hereinafter referred to as “imaging apparatus 10”) illustrated in FIG. 1 is a radiographic image diagnostic apparatus that captures a radiographic image that is a diagnostic image of a subject H (that is, a subject). An imaging unit 12 for imaging, an image processing unit 14 for processing a radiation image captured by the imaging unit 12, a monitor 16, a printer 18, and a measuring unit 19 for measuring the state of the radiation fixed detector 30 of the imaging unit 12. A control unit 20 that controls the photographing unit 12, the image processing unit 14, and the measurement unit 19.

The imaging unit 12 includes a radiation source 22, an imaging table 24, and imaging means 26, and images a radiation image of the subject H.
The radiation source 22 is a normal radiation source installed in various types of 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 further 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 imaging unit 26 includes a radiation fixed detector 30 (hereinafter referred to as “FPD 30”), and captures a radiation image on the FPD 30.
In the same manner as the normal radiographic imaging apparatus 10, the imaging apparatus 10 receives the radiation that is irradiated by the radiation source 22 and passes through the subject H by the light receiving surface of the FPD 30, and photoelectrically converts the radiation to be examined. A radiograph of the person H is taken.

In the present invention, the FPD 30 is a normal FPD (Flat Panel Detector) used in a radiographic imaging apparatus.
In the present invention, the FPD 30 uses a photoconductive film such as amorphous selenium and a TFT (Thin Film Transistor), etc., and collects electron-hole pairs (e-h pairs) emitted from the photoconductive film upon incidence of radiation. Using a scintillator layer, a photodiode, a TFT, etc., formed of a phosphor that emits light (fluorescence) by the incidence of radiation such as “CsI: Tl”, which is read out as an electrification signal by a TFT, and so on. Any of so-called indirect FPDs in which the light emitted from the scintillator layer upon incidence is photoelectrically converted by a photodiode and read out as an electrical signal by a TFT may be used.

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 includes a data processing unit 32, a defect detection unit 36, and an image correction unit 38. From the output signal output from the FPD 30, the image data corresponding to the display on the monitor 16, the printer 18 The image data corresponding to the print output and the output of the radiation image (data) using the network or the recording medium are created.
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 output from the FPD 30 to convert it into image data of a radiographic image.

The defect detection unit 36 (hereinafter referred to as “detection unit 36”) detects a pixel defect of the FPD 30.
Here, the pixel defect is a pixel (or a detection element or a region) that outputs an inappropriately high output signal or an inappropriately low output signal with respect to an incident radiation dose. Unit pixel defects, line defects in which a plurality of pixels are continuously defective, continuous defects, and the like.
The detection unit 36 detects a pixel defect of the FPD 30 and creates a defect map indicating the positions of all the pixel defects on the FPD 30 (that is, the positions of pixels having defects). As described above, the detection unit 36 detects the pixel defect position information of the FPD 30.
The detection unit 36 sends the created defect map to the image correction unit 38.

The detection method of the pixel defect by the detection unit 36 is not particularly limited. For example, a detection method using a dark image (dark current), a predetermined amount of radiation from the radiation source 22 in the absence of the subject H, FPD 30 Any of the pixel defect detection methods used in various radiographic imaging apparatuses, such as a detection method using a radiographic image obtained by uniformly irradiating (exposure), can be used.
Hereinafter, this embodiment will be described as an example of creating a defect map using a dark image.

  The image correction unit 38 is a unit that performs image processing on the image data. The image correction unit 38 performs predetermined image processing on the radiation image (more precisely, image data of the radiation image) processed by the data processing unit 32, and the like. The radiographic image corresponds to the image display by the printer, the output of the print (hard copy) by the printer 18, and the output to the network or storage medium.

The image correction unit 38 corrects the pixel defect of the image data processed by the data processing unit 32 based on the defect map. Specifically, the image correction unit 38 acquires position information of each pixel defect from the defect map. Further, the image correcting unit 38 specifies the position of the pixel defect based on the acquired position information of the pixel defect, and corrects the specified pixel defect 60 by the average value of the two normal pixels around the isolated point pixel defect. .
The image correction unit 38 corrects pixel defects on the image data by performing the same correction on all the pixel defects shown in the defect map.

Here, the pixel defect correction method is not particularly limited. In addition to the method of using the average value of pixels on both sides and surrounding pixels as pixel defect (the pixel) data as in the present embodiment, a predetermined region around the pixel defect. It is possible to use pixel defect correction methods used in various types of radiographic imaging apparatuses, such as a method of generating pixel defect data from the tendency of changes in pixels.
For example, the pixel defect may be corrected by a weighted average value calculated using three or more normal pixels around the pixel defect and the distance between each normal pixel and the pixel defect.

  The image processing performed by the image correction unit 38 is not limited to pixel defect correction. For example, offset correction (dark correction), gain correction (shading correction), floor correction, and the like that are performed in accordance with calibration together with pixel defect correction. Image processing performed in various types of radiographic imaging devices such as tone correction, density correction, and data conversion for converting image data into monitor display data or print output data may be performed.

  The image correction means 38 sends image data subjected to predetermined image processing to the monitor 16 and / or the printer 18 as necessary.

The measurement unit 19 includes a temperature measurement unit 42 that measures the temperature of the FPD 30 and an exposure dose measurement unit 44 that measures the dose to which the FPD 30 is exposed, and measures the state of the FPD 30.
As the temperature measuring means 42, devices that measure various temperatures such as contact type measuring devices such as thermocouples and thermistors, and non-contact type measuring devices such as radiation thermometers can be used.
Further, as the exposure dose measuring means 44, for example, a device for calculating the exposure dose (mAs) from the product of the tube current (mA) flowing through the radiation source at the time of exposure and time (sec), a set value at the time of exposure And / or a device that measures (or calculates) various doses, such as a device that calculates an exposure dose from an input value, a device that calculates an exposure dose from an output signal of the FPD (more precisely, the intensity of the output signal), etc. Can be used.
The temperature measurement unit 42 and the exposure dose measurement unit 44 send the measured temperature and exposure dose to the control unit 20.

The control unit 20 calculates the defect map calculation timing based on the temperature and the exposure dose of the FPD 30 sent from the temperature measurement means 42 and the exposure dose measurement means 42 in addition to the elapsed time after the defect map is created. And decide. That is, the control unit 20 determines whether or not the defect map needs to be updated based on the temperature of the FPD 30 and the exposure dose in addition to the elapsed time after the defect map is created.
Specifically, since the defect map was created (more precisely, from the previous defect map creation), the elapsed time, the temperature change of the FPD 30, the cumulative exposure dose of the FPD 30, The exposure dose and the like are compared with respective threshold values (that is, allowable values and set values) to detect whether each value exceeds the threshold value, and when the threshold value is exceeded, the defect map is updated.

Here, the detection method of elapsed time is not specifically limited, For example, the apparatus which measures time may be provided in the control part 20, and the progress of time after producing a defect map should just be detected.
Even if the temperature change of the FPD 30 is detected by the temperature measuring means 42, only the measurement result is sent from the temperature measuring means 42, and the control unit 20 sets the measurement result and the temperature at the time of creating the previous defect map. May be detected.
Further, as the temperature change of the FPD 30, a temperature difference, a length of time when the temperature difference is equal to or greater than a certain temperature difference, and the like can be set.
Further, even if the cumulative exposure dose is detected by adding the exposure dose measured by the exposure dose measuring means 42, the exposure dose measuring means 42 only measures the exposure dose, and the control unit 20 may add and detect the measurement results.
The single exposure dose is the maximum value of the radiation received by the FPD when photographing the subject. The single exposure dose may be detected by the exposure dose measurement unit 42 or may be calculated by analyzing the measurement result sent from the exposure dose measurement unit 42 by the control unit 20.

  Hereinafter, the determination of whether or not it is necessary to update the defect map (that is, the pixel defect position information of the FPD 30) by the control unit 20 will be described in detail with reference to FIG. FIG. 2 is a flowchart showing an example of a method for determining whether or not a defect map needs to be updated. In the example shown in FIG. 2, it is determined whether or not the defect map needs to be updated based on the accumulated exposure dose, temperature change, and elapsed time.

First, when the apparatus is activated, activation processing (that is, calibration) is performed (S102). Specifically, offset correction, gain correction (that is, shading correction), and acquisition or update of a defect map are performed. Further, after obtaining or updating the defect map, an elapsed time T described later is set to T = 0.
As a result, a radiographic image can be recorded.

Next, whether or not the cumulative exposure dose after creating the currently used defect map (that is, after detecting the pixel defect position information of the currently used FPD 30) exceeds the threshold value is determined. It detects (S104).
If the cumulative exposure dose exceeds the threshold, it is determined that the defect map needs to be updated, and a dark image is acquired (S110).
On the other hand, if the cumulative exposure dose does not exceed the threshold, it is detected whether or not the temperature change after the creation of the currently used defect map exceeds the threshold (S106).
If the temperature change exceeds the threshold, it is determined that the defect map needs to be updated, and a dark image is acquired (S110).
If the temperature change does not exceed the threshold, it is detected whether or not the elapsed time since the creation of the currently used defect map exceeds the threshold (S108). That is, if the elapsed time threshold is t and the elapsed time is T, it is detected whether t ≦ T.
When the elapsed time exceeds the threshold (that is, t ≦ T), it is determined that the defect map needs to be updated, and a dark image is acquired (S110).
When a dark image is acquired, a pixel defect is detected from the acquired dark image, and a defect map is created. The defect map created in this way is set as a new defect map. That is, the defect map is updated (S112).
When the defect map is updated, the elapsed time and accumulated exposure dose are reset, that is, the elapsed time T is set to T = 0, and the accumulated exposure dose is set to 0. Further, the temperature at the time of updating the defect map is set as a reference temperature for temperature change (S114).

After the elapsed time and accumulated exposure dose are reset and the reference temperature is set, it is determined whether there is an end work request (S116). Here, the end work request is an instruction to stop or pause the operation of the apparatus.
In S108, if the elapsed time does not exceed the threshold (that is, t> T), it is determined whether there is an end work request (S116).

When there is no end work request, the process returns to S104, and the above-described processing is performed again, such as whether or not the cumulative exposure dose exceeds the threshold value.
If there is an end-of-work request, end-of-work processing is performed (S118).

The control unit 20 determines whether or not it is necessary to update the defect map by repeating the above processing until the end-of-work request is received and the processing is terminated.
Further, the image correction unit 38 of the image processing unit 14 corrects the pixel defect based on the updated defect map (that is, the latest defect map).

In addition to determining whether or not the defect map needs to be updated, the control unit 20 performs the photographing operation of the photographing unit 12, the processing of the image data of the image processing unit 14, and the transmission of the image data to the monitor 16 and the printer 18. And so on.
The radiographic image capturing apparatus 10 of the present embodiment is basically configured as described above.

The radiographic imaging device 10 calculates the detection timing of the defect map based on the temperature change of the FPD 30 and the cumulative exposure dose of the FPD 30 in addition to the elapsed time, and newly detects (that is, updates) the defect map. Thus, pixel defects can be appropriately detected according to the usage status of the imaging apparatus 10 and the characteristics of the FPD 30.
Thereby, the pixel defect can be corrected based on an accurate defect map, that is, pixel defect position information, and a high-quality image in which the pixel defect is accurately corrected can be created. Thereby, also when using for a medical image, it can prevent that a pixel defect arises and causes a misdiagnosis.
Further, since the defect map can be updated at an appropriate frequency, the addition to the apparatus can be reduced, and the work efficiency can be increased.

In particular, when a direct FPD that directly converts radiation such as amorphous selenium into electric charges is used, the above effect is more suitable because crystallization of amorphous selenium proceeds due to temperature rise or radiation exposure. Can get to. Specifically, amorphous selenium is easy to deposit on a large area substrate, and since selenium has a dark resistance of 10 ¹² Ωcm or more, it is easy to use as a semiconductor material for X-ray detection, at a relatively low temperature. Although there is an advantage that film formation is possible (specifically, film formation can be performed under temperature conditions that do not affect the TFT substrate when manufactured as an FPD), temperature changes and radiation are exposed. As a result, crystallization is likely to proceed, that is, defects increase.
In this way, even in the case of FPD using amorphous selenium in which pixel defects increase due to temperature changes and radiation exposure, pixel defects can be detected appropriately, so that high-quality images with pixel defects corrected accurately Can be formed.

Here, the defect map to be updated is preferably created by logical OR of the pixel defect of the defect map before the update and the pixel defect detected from the dark image. That is, the defect map is preferably updated by sequentially adding the detected pixel defects.
By sequentially adding the detected pixel defects in this manner, a pixel defect that is not detected can be detected as a pixel defect in the subsequent defect map once detected even if it is detected.
Specifically, a pixel that is not completely a pixel defect and is a normal pixel or a pixel defect depending on the state (hereinafter referred to as a “preliminary pixel defect”) is normal for a dark image at the time of update. A functioning pixel can also be detected as a pixel defect.
In this manner, the pixel defect can be reliably corrected by detecting the spare pixel defect as the pixel defect.

In addition, if an extremely large pixel defect, that is, a pixel defect in a certain area or more, is detected by comparing the pixel defect detected from the dark image with the previous defect map, it should be excluded from the pixel defect as dust or dust. Is preferred. In this way, it can be removed due to adhesion on the surface, etc., and by removing dust and dust whose position changes over time, erroneous detection can be prevented even when logical sum is used, and pixel Defects can be corrected.
In addition, when it is detected as dust or dust, it is preferable to notify the user that dust or dust is attached by sounding a buzzer or displaying a warning on the screen. Thereby, dust and dust can be quickly removed, and a high-quality image can be recorded.

  In addition, when the defect map is updated by the logical sum described above, a pixel defect that has been detected once as a pixel defect is not detected from the dark image when the defect map is updated a certain number of times. Is preferably excluded. Thereby, even when logical sum is used, erroneous detection can be prevented and pixel defects can be corrected appropriately.

  Here, in the above embodiment, it is detected whether or not the threshold value is exceeded in the order of the cumulative exposure dose (S104), the temperature change (S106), and the elapsed time (S108) (that is, each value and the threshold value). However, the detection order is not particularly limited, and any order may be used.

In the above embodiment, whether or not to update the defect map is determined based on the elapsed time, the temperature change, and the cumulative exposure dose (that is, the defect map update timing is calculated). Alternatively, it may be determined whether or not to update the defect map based on a single exposure dose of the FPD 30 instead of the temperature change and the cumulative exposure dose.
As a method of determining whether or not it is necessary to update the defect map based on a single exposure dose, after creating a currently used defect map, the exposure dose once Detects if there was an exposure that exceeded the threshold, and if it detected that there was an exposure that exceeded the threshold, it performed a defect map, and if no exposure was detected that exceeded the threshold, the defect map was updated. No method is illustrated.
Further, based on the measurement result of the exposure dose measuring means, the number of FPD exposures after the defect map is created may be calculated, and the necessity of updating the defect map may be determined based on the number of exposures. .

  Since pixel defects can be detected more reliably, it is possible to detect both the temperature change and the cumulative exposure dose, more preferably all of the single exposure dose in addition to the elapsed time. Although it is preferable to determine whether or not to update the defect map based on at least one of the temperature change, the cumulative exposure dose, and the single exposure dose and the elapsed time, the use status of the apparatus and the FPD Pixel defects can be detected according to the characteristics.

  In addition, the control unit 20 is provided with a recording unit, the timing at which the defect map is updated, the detection result, the condition for determining the update (that is, the value exceeding the threshold value), the temperature at the time of update, the cumulative exposure dose, It is preferable to record the maximum exposure dose of exposure, elapsed time, etc., and store it as a log. By saving the log in this way, it becomes easy to determine the relationship between pixel defects and measurement conditions and the state of the FPD 30.

Here, it is preferable that the control unit 20 updates the defect map (that is, detects pixel defect position information) as the end work process.
FIG. 3 is a flowchart showing a preferred example of the closing work process (S118) shown in FIG.

The control part 20 acquires a dark image, when there exists an end work request | requirement (S120).
When a dark image is acquired, a pixel defect is detected from the acquired dark image, and a defect map is created. The defect map created in this way is set as a new defect map. That is, the defect map is updated (S122).
Thereafter, other end-of-day processing is performed (S124).

  Furthermore, the control unit 20 detects whether or not the defect map is updated during the end process during the start process, and if the defect map is updated during the end process, the creation of the defect map during the start process is omitted. It is preferable that the defect map is not updated.

FIG. 4 is a flowchart showing a preferred example of the activation process (S102) shown in FIG.
When the photographing apparatus 10 is activated, the control unit 20 performs offset correction and gain correction as calibration processing (S130).
Next, it is detected whether or not the defect map has been updated during the last closing process (S132).
If the defect map is updated during the last closing process, the elapsed time T is set to T = 0 (S136).
Thereafter, the process proceeds to S104 where it is detected whether the cumulative exposure dose exceeds the threshold value.

On the other hand, if the defect map has not been updated during the last closing process, or if it is the first activation, a dark image is acquired by the same method as described above, and a defect map is created from the dark image (S134).
After creating the defect map, the elapsed time T is set to T = 0 (S136).
Thereafter, the process proceeds to S104 where it is detected whether the cumulative exposure dose exceeds the threshold value.

As described above, by detecting the pixel defect at the end of processing, it is possible to detect the pixel defect more reliably than when detecting the pixel defect at the start-up process. Regarding this point, immediately after startup, the spare pixel defect is likely to function as a normal pixel and is difficult to detect as a pixel defect. This is presumed to be possible to detect.
Thereby, a pixel defect can be detected more reliably and a pixel defect can be corrected more accurately.
Furthermore, by updating the defect map at the end of work processing and omitting the update of the defect map at the time of starting, the time required for the start processing at the start can be shortened, and the defect map created at the end of processing is used. Thus, the pixel defect can be corrected more accurately.

  Next, another example of a method for determining whether or not a defect map needs to be updated by the control unit 20 will be described. FIG. 5 is a flowchart showing another example of a method for determining whether or not a defect map needs to be updated. In FIG. 5, the same processing steps as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

First, when the apparatus is activated, activation processing (that is, calibration) is performed (S102).
Next, it is detected whether or not the cumulative exposure dose after creating the currently used defect map exceeds a threshold value (S104).
If the cumulative exposure dose exceeds the threshold, it is detected whether there is an imaging request (S140). Here, the photographing request is a request such as photographing for obtaining an image of the subject H, not photographing a dark image for creating a defect map. That is, it is in a state where it is detected that preparation for shooting has started, such as a request for shooting or input of shooting menu information.
On the other hand, if the cumulative exposure dose does not exceed the threshold, it is detected whether or not the temperature change after the creation of the currently used defect map exceeds the threshold (S106).
If the temperature change exceeds the threshold, it is detected whether there is a photographing request (S140).
On the other hand, if the temperature change does not exceed the threshold value, it is detected whether or not the elapsed time since the creation of the currently used defect map exceeds the threshold value (S108).

If the elapsed time exceeds the threshold (that is, t ≦ T), it is detected whether there is a photographing request (S140).
If it is detected that there is a photographing request, a dark image is not acquired and a subject is photographed (S142).
Image processing of the captured image is performed (S144). Thereafter, it is detected again whether there is a photographing request (S140).
On the other hand, if there is no photographing request (that is, no photographing request is detected), a dark image is acquired for updating the defect map (S110).

When a dark image is acquired, a pixel defect is detected from the acquired dark image, and a defect map is created. The defect map created in this way is set as a new defect map. That is, the defect map is updated (S112).
When the defect map is updated, the elapsed time and accumulated exposure dose are reset, that is, the elapsed time T is set to T = 0, and the accumulated exposure dose is set to 0. Further, the temperature at the time of updating the defect map is set as a reference temperature for temperature change (S114).

After the elapsed time and accumulated exposure dose are reset and the reference temperature is set, it is determined whether there is an end work request (S116).
In S108, if the elapsed time does not exceed the threshold (that is, t> T), it is determined whether there is an end work request (S116).

When there is no end work request, the process returns to S104, and the above-described processing is performed again, such as whether or not the cumulative exposure dose exceeds the threshold value.
On the other hand, when there is a request for closing work, the closing process is performed (S118).

  As described above, even when any of the elapsed time, the accumulated exposure dose, and the temperature change exceeds the threshold value, if there is an imaging request, after the imaging is performed, dark image acquisition or the like (that is, S110, S112, and S114) is performed. By performing processing related to the update of the defect map, that is, by giving priority to shooting, an image can be shot without waiting for the user. Specifically, when used for medical purposes, it is possible to cope with a case where it is necessary to take an image as soon as possible due to an emergency patient or the like.

In the above-described embodiment, the elapsed time, the FPD exposure dose, and the FPD temperature are determined based on different criteria. However, the necessity of updating the defect map may be determined by combining them.
Hereinafter, with reference to FIG. 6, an example of a determination method for performing determination by combining the elapsed time, the exposure dose, and the temperature will be described. FIG. 6 is a flowchart showing an example of a method for determining whether or not the defect map needs to be updated.

First, when the apparatus is activated, activation processing (that is, calibration) is performed (S102).
Next, it is detected whether or not the cumulative exposure dose since the FPD is installed (that is, the total cumulative exposure dose of the FPD) exceeds a threshold value (S160).
If all the cumulative exposure dose exceeds the threshold, the threshold t of the elapsed time (i.e., a set value t of the update time interval of the defect map) is defined as t ₁ (S162). In other words, it is assumed that _t = t _1. Thereafter, it is detected whether or not the elapsed time T exceeds the threshold t of elapsed time (S170).
On the other hand, if the total cumulative exposure dose does not exceed the threshold, it is detected whether the temperature of the FPD 30 exceeds the threshold (S164).

If the temperature exceeds the threshold value, the threshold value t of the elapsed time and _{t 2} (S166). In other words, it is assumed that _t = t _2. Thereafter, it is detected whether or not the elapsed time T exceeds the threshold t of elapsed time (S170).
On the other hand, if the temperature does not exceed the threshold value, the threshold value t of the elapsed time is _{t 3} (S168). In other words, it is assumed that _t = t _3. Thereafter, it is detected whether or not the elapsed time T exceeds the threshold t of elapsed time (S170).

In S170, it is detected whether or not the elapsed time T exceeds the elapsed time threshold t set in S160 to S168.
When the elapsed time exceeds the threshold (that is, t ≦ T), it is determined that the defect map needs to be updated, and a dark image is acquired (S110).
When a dark image is acquired, a pixel defect is detected from the acquired dark image, and a defect map is created. The defect map created in this way is set as a new defect map. That is, the defect map is updated (S112).
When the defect map is updated, the elapsed time, that is, the elapsed time T is set to T = 0, and the cumulative exposure dose is set to 0 (S172).

If the elapsed time is reset, it is determined whether or not there is an end work request (S116).
In S108, if the elapsed time does not exceed the threshold (that is, t> T), it is determined whether there is an end work request (S116).

When there is no end work request, the process returns to S104, and the above-described processing is performed again, such as whether or not the cumulative exposure dose exceeds the threshold value.
If there is an end-of-work request, end-of-work processing is performed (S118).

As described above, in this embodiment, the threshold of the elapsed time is set according to the temperature of the FPD 30 and the total accumulated exposure dose, and when the temperature of the FPD or the total accumulated exposure dose exceeds a certain value, a short interval is set. To update the defect map.
As a result, it is possible to cope with cases where pixel defects are likely to occur due to high temperatures, and cases where pixel defects are likely to occur due to increased exposure dose. it can.

Here, the threshold values of the temperature and the total accumulated exposure dose are not limited to one value, and it is preferable to provide a plurality of threshold values and set the threshold value t of elapsed time for each threshold value. More preferably, a threshold t for elapsed time is set for each combination in combination with a threshold for cumulative exposure dose.
In this way, by setting the threshold t of elapsed time in stages, pixel defects can be detected appropriately according to the usage situation. In other words, in a situation where pixel defects are likely to occur, it is possible to reliably detect pixel defects by updating the defect map at a high frequency, and it is not necessary to update the defect map more frequently than necessary. The addition to the apparatus can also be reduced.

  As described above, the radiographic image capturing apparatus and the pixel defect information acquisition method according to the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and various types can be made without departing from the gist of the present invention. Improvements and changes may be made.

  For example, the defect map detection timing, that is, the update timing may be detected (or controlled) by combining the above embodiments. Specifically, the threshold of elapsed time is determined based on the FPD temperature and the total accumulated exposure dose, and further, the elapsed time, FPD temperature change, and FPD accumulated exposure since the defect map was created. When either the radiation dose or the single exposure dose of the FPD exceeds the threshold value, the defect map may be updated.

  Further, since the pixel defect can be detected more accurately, as in the present embodiment, when the apparatus is in operation, the update timing of the defect map is detected based on at least one of the exposure dose and temperature and the elapsed time, Furthermore, it is preferable to update the defect map at the time of end-of-day processing, but the present invention is not limited to this, and the defect map is updated (or detected) at the time of end-of-day processing regardless of the detection method and detection timing of the defect map during operation. By doing so, pixel defects can be detected more accurately than when detecting at the time of activation. Thereby, pixel defects can be corrected accurately, and a higher quality image can be created.

It is a block diagram which shows schematic structure of the radiographic imaging apparatus of this invention. It is a flowchart which shows an example of the determination method of the necessity of the update of a defect map. It is a flow figure showing an example of end-of-day processing. It is a flowchart which shows an example of a starting process. It is a flowchart which shows another example of the determination method of the necessity of the update of a defect map. It is a flowchart which shows another example of the determination method of the necessity of the update of a defect map.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radiation imaging device 12 Imaging part 14 Image processing part 16 Monitor 18 Printer 19 Measuring part 20 Control part 22 Radiation source 24 Imaging stand 26 Imaging means 30 FPD (radiation solid state detector)
32 Data processing means 36 Pixel defect detection means 38 Image correction means 42 Temperature measurement means 44 Exposure dose measurement means

Claims (8)

A radiation source;
A radiation solid detector for detecting radiation irradiated by the radiation source;
A defect detection means for detecting pixel defect position information of the radiation fixed detector;
Control means for controlling the timing at which the defect detection means detects pixel defect position information;
Having at least one of an exposure dose measuring means for measuring an exposure dose irradiated to the radiation fixed detector and a temperature measuring means for measuring the temperature of the radiation fixed detector;
The control means includes a pixel by the defect detection means based on at least one of a measurement result of the exposure dose measurement means and a measurement result of the temperature measurement means, and an elapsed time after the pixel defect is detected by the defect detection means. A radiographic imaging apparatus that calculates timing for detecting defect position information and waits for detection of pixel defect position information by the defect detection means when a request for imaging is detected . A radiation source;
A radiation solid detector for detecting radiation irradiated by the radiation source;
A defect detection means for detecting pixel defect position information of the radiation fixed detector;
Control means for controlling the timing at which the defect detection means detects pixel defect position information;
Having at least one of an exposure dose measuring means for measuring an exposure dose irradiated to the radiation fixed detector and a temperature measuring means for measuring the temperature of the radiation fixed detector;
The control means includes a pixel by the defect detection means based on at least one of a measurement result of the exposure dose measurement means and a measurement result of the temperature measurement means, and an elapsed time after the pixel defect is detected by the defect detection means. The timing for detecting the defect position information is calculated, and further, the defect detection means is detected by the defect detection means at the end of processing, and the defect detection means at the start after detecting the pixel defect position information at the end of processing. A radiographic imaging device that does not detect pixel defect position information. A radiation source;
A radiation solid detector for detecting radiation irradiated by the radiation source;
A defect detection means for detecting pixel defect position information of the radiation fixed detector;
Control means for controlling the timing at which the defect detection means detects pixel defect position information;
Having at least one of an exposure dose measuring means for measuring an exposure dose irradiated to the radiation fixed detector and a temperature measuring means for measuring the temperature of the radiation fixed detector;
The control means includes a pixel by the defect detection means based on at least one of a measurement result of the exposure dose measurement means and a measurement result of the temperature measurement means, and an elapsed time after the pixel defect is detected by the defect detection means. The timing for detecting the defect position information is calculated, and further, based on at least one of the cumulative exposure dose measured by the exposure dose measuring means and the temperature detected by the radiation fixed detector, the allowance of the elapsed time is calculated. Radiation imaging device that sets the value. The control means includes at least one of a temperature change, a cumulative exposure dose, a single exposure dose, and pixel defect position information of the radiation fixed detector after the pixel defect position information is detected by the defect detection means. Detecting the defect when at least one of the detected temperature change, the cumulative exposure dose, the single exposure dose, and the elapsed time exceeds an allowable value. The radiographic image capturing apparatus according to claim 1 , wherein pixel defect position information is detected by means. The defect detecting means includes a pixel defects detected during an update, taking the logical sum of the pixel defect of the pre-update pixel defect position information, in any one of claims 1 to 4, new pixel defect position information The radiographic imaging apparatus described. A radiation source;
A radiation solid detector for detecting radiation irradiated by the radiation source;
A defect detection means for detecting pixel defect position information of the radiation fixed detector;
Control means for controlling the timing at which the defect detection means detects pixel defect position information;
The control means causes the defect detection means to detect pixel defect position information at the time of the end-of-work process, and detects the defect at the start after the pixel defect position information is detected by the defect detection means at the time of the end-of-process processing. A radiographic apparatus that does not detect pixel defect position information by means. A pixel defect information acquisition method for acquiring pixel defect position information of a fixed radiation detector,
Elapsed time since the detection of the pixel defect position information, and temperature change, cumulative exposure dose, and single exposure dose of the radiation fixed detector since the detection of the pixel defect position information Detect one,
If any one of the detected elapsed time, temperature change, cumulative exposure dose and single exposure dose exceeds a set value, update the pixel defect position information of the radiation fixed detector, and A pixel defect information acquisition method that waits for update of pixel defect position information of the fixed radiation detector when a request for imaging is detected . A pixel defect information acquisition method for acquiring pixel defect position information of a fixed radiation detector,
Based on at least one of the temperature of the radiation fixed detector and the radiation dose of the radiation detector, the update time interval of the pixel defect position information of the radiation fixed detector is set,
Compare the elapsed time since the detection of the pixel defect position information and the update time interval,
A pixel defect information acquisition method of acquiring pixel defect position information of the radiation fixed detector and updating the pixel defect position information when the elapsed time exceeds the update time interval.

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