JP6708434B2 - Radiation imaging apparatus and processing method of radiation imaging apparatus - Google Patents

Description

The present invention relates to a radiation imaging apparatus and a processing method of the radiation imaging apparatus.

In recent years, an X-ray imaging apparatus having an X-ray flat panel detector has been put into practical use. It is known that an X-ray flat panel detector produces an offset component even when no X-ray is incident. The X-ray imaging apparatus can improve the image quality by subtracting the offset data corresponding to the offset component from the X-ray image.

Patent Document 1 discloses an X-ray imaging apparatus which has a plurality of imaging modes and in which offset data is collected and stored in advance for each imaging mode. Further, Patent Document 1 discloses that the offset data varies depending on the temperature inside the device.

For this reason, it is desirable that the offset data be updated regularly in order to correspond to the change in the offset data. Further, in order to reduce the amount of noise included in the offset data, the offset data may be acquired by averaging by collecting images of a plurality of frames for each shooting mode.

JP, 2001-99944, A

However, when the X-ray imaging apparatus updates the offset data for all imaging modes, the updating time becomes long. Then, if the time for updating the offset data becomes long, there is a possibility that the time during which imaging can be performed is limited. On the other hand, the X-ray imaging apparatus performs the offset correction using the old offset data unless the offset data is updated regularly, so that the image quality of the X-ray image may deteriorate.

An object of the present invention is to provide a technique capable of shortening the time required to generate offset data and suppressing the occurrence of artifacts due to offset correction.

The radiation imaging apparatus according to the present invention is configured to convert radiation into electric charges by an imaging mode setting unit that sets one imaging mode out of a plurality of imaging modes and an imaging mode set by the imaging mode setting unit. A radiation detector for generating an image; an offset data storage unit for storing offset data in an imaging mode smaller than the plurality of imaging modes; and the radiation detection using the offset data stored in the offset data storage unit. Of the radiation detector so as to perform the reading used for image generation and the reading not used for image generation within one frame, based on the offset correction means for correcting the image generated by the detector and the set imaging mode. and control means possess for the control means controls the radiation detector so as to read without using the read image generated for use in the image generated in the one frame, the offset data storage means The read time Tr used for image generation of the radiation detector is equal to the read time Tr not used for image generation in the same charge accumulation time as the image capture mode in which the offset data is stored, and the image capture mode is used. A read determination unit that determines whether or not the conditional expression of Tf−2×Tr≧Tc is satisfied based on the frame time Tf of one frame based on the imaging mode set by the setting unit and the charge storage time Tc. The radiation detector performs reading used for image generation and reading not used for image generation within one frame when the conditional expression is satisfied .

It is possible to shorten the time required to generate the offset data and suppress the occurrence of artifacts due to the offset correction.

It is a figure which shows the structural example of a radiation imaging device. It is a figure which shows an example of an imaging mode setting means. 9 is a timing chart showing X-ray image data of imaging mode number 23. 7 is a timing chart showing offset data of imaging mode number 23. 9 is a timing chart showing X-ray image data of imaging mode number 24. It is a figure which shows the time required for offset data collection. It is a figure which shows the time required for offset data collection. 9 is a timing chart showing X-ray image data of imaging mode number 25. It is a timing chart which shows 11-fps X-ray image data. It is a figure which shows the time for every mode, and an imaging mode number.

(First embodiment)
FIG. 1 is a block diagram showing a configuration example of a radiation imaging apparatus according to the first embodiment of the present invention. The radiation imaging apparatus includes an irradiation switch 103, an X-ray generation unit 104, an X-ray flat panel detector 105, a display unit 106, and a device control unit 107. The X-ray generation unit 104 is a radiation generation unit that includes the X-ray irradiation control unit 101 and the X-ray tube 102 and emits radiation. The X-ray tube 102 irradiates the X-ray flat panel detector 105 with X-rays via the subject 100. The X-ray irradiation control unit 101 controls the X-ray irradiation of the X-ray tube 102. The irradiation switch 103 is a switch for switching on/off of X-ray irradiation.

The X-ray flat panel detector 105 is a radiation detector, and detects the radiation (X-rays) transmitted through the subject 100. The X-ray flat panel detector 105 is arranged in a matrix and has a plurality of detection elements each of which converts radiation into an electric charge. The electric charges accumulated in the plurality of detection elements are sequentially read out, and the read-out image data is stored in the apparatus. Output to the control unit 107. The device control unit 107 performs image processing and the like on the image data read from the X-ray flat panel detector 105 and displays the image data on the display unit 106. The device control unit 107 is a control unit that controls the entire radiation imaging apparatus including the X-ray irradiation control unit 101, the X-ray flat panel detector 105, and the display unit 106.

The device control unit 107 includes an offset correction unit 108, an offset mode storage unit 109, an offset data storage unit 110, a read determination unit 111, and an imaging mode setting unit 112. The offset correction means 108 performs offset correction. The offset mode storage means 109 is an imaging mode storage means and stores the imaging mode number of offset data collected in advance. The offset data storage means 110 stores a plurality of offset data collected in advance. The read determination means 111 determines whether or not a read that is not used to generate an X-ray image can be inserted during X-ray imaging. The image capturing mode setting means 112 sets the image capturing mode.

The offset correction means 108 performs offset correction by subtracting the offset data stored in advance in the offset data storage means 110 from the X-ray image data read from the X-ray flat panel detector 105 after the X-ray irradiation. .. The offset data storage unit 110 is a memory that averages the images of a plurality of frames read from the X-ray flat panel detector 105 without irradiating the X-rays, and stores the averaged images as offset data. The offset data storage unit 110 is, for example, a volatile memory such as a RAM (Random Access Memory). The image capturing mode setting means 112 sets an image capturing mode and an image capturing condition.

FIG. 10 shows the time (seconds) and the imaging mode number for each imaging mode required to collect the offset data when the number of frames of offset data to be collected in advance is 16. The image reading size of the X-ray flat panel detector 105 has two modes, a mode of 40 cm (width)×40 cm (height) and a mode of 20 cm (width)×20 cm (height). Further, there are two modes of amplifier gain when converting X-rays into electric charges and reading the electric charges, that is, a 1× mode and a 2× mode. There are two binning modes, a 1×1 mode and a 2×2 mode. There are seven types of frame rate modes from 30 fps to 1 fps. Further, when the image read size is 40 cm (width)×40 cm (height), it is difficult to achieve the frame rate of 30 fps, and therefore the modes that cannot be realized are represented by “−”.

For example, in the imaging mode number 23, the image read size of the X-ray flat panel detector 105 is 40 cm (width)×40 cm (height), the amplifier gain is double, the binning mode is 2×2, and the frame is The rate is 15 fps. Further, there are 22 imaging modes in total, and the time for updating the offset data in all the imaging modes is 109.8 seconds, which is the total time of the offset data collection time for each imaging mode. Hereinafter, an embodiment for shortening the time required to update the offset data will be described.

The radiation imaging apparatus has 22 imaging modes shown in FIG. The imaging mode number stored in the offset mode storage unit 109 is the imaging mode number having the highest frame rate in each image reading size of the X-ray flat panel detector 105 and each binning mode. An example of numbers 14, 23, 32, and 41 will be described.

FIG. 2 is a diagram showing a configuration example of the imaging mode setting means 112. The imaging mode setting means 112 has a display unit 113, an upper button 114, and a lower button 115. The imaging mode setting unit 112, according to the operation of the operator, the image reading size of the X-ray flat panel detector 105, the binning mode, the frame rate (fps), and the irradiation according to the imaging purpose and the imaging region of the subject 100. It is possible to set the tube voltage, tube current, mAs value, etc. of the X-ray to be used. The upper button 114 is a button for increasing the frame rate (fps) and the like. The lower button 115 is a button for lowering the frame rate (fps) and the like. For example, if the operator wants to reduce the frame rate (fps), the operator presses the down button 115 once to reduce the frame rate displayed on the display unit 113 of fps from 15 to 10, and press the button twice to reduce the frame rate to 5. Go down to. Further, when the frame rate is set, the imaging mode setting unit 112 calculates the time of one frame which is the reciprocal of the frame rate.

Next, the read determination means 111 will be described. As an example, a case where the imaging mode number of the offset data stored in the offset mode storage unit 109 is 23 and the imaging mode numbers of the X-ray image data captured by the radiation imaging apparatus are 23 and 24 will be described. Specifically, as shown in FIG. 10, in the imaging mode number 23, the image reading size of the X-ray flat panel detector 105 is 40 cm (width)×40 cm (height), the gain is 1×, and the binning mode is 2×. 2. The frame rate is 15 fps. The imaging mode number 24 has the same image reading size, gain, and binning mode as the imaging mode number 23, and has a frame rate of 10 fps.

Assuming that the time of one frame of the image capturing mode numbers 23 and 24 is Tf23 and Tf24, respectively, the image capturing mode setting unit 112 calculates the one frame time from the frame rate as shown in the following equations (1) and (2). Calculate Tf23 and Tf24.
Tf23=1/15=66.6 (ms) (1)
Tf24=1/10=100 (ms) (2)

Further, as shown in FIG. 3, assuming that the readout time of the image data is Tr and the charge accumulation time during which the readout is not performed is Tc, the respective times Tr and Tc will be described as the times of the following expressions (3) and (4). ..
Tr=20 (ms) (3)
Tc=46.7 (ms) (4)

Next, the read determination means 111 determines whether the conditional expression of the following expression (5) is satisfied, where Tf is the time of one frame.
Tf-2×Tr≧Tc (5)

The frame time Tf of one frame is a time based on the frame rate of the image capturing mode set by the image capturing mode setting unit 112. When the X-ray imaging is performed in the imaging mode number 23, Tf=Tf23, and therefore the equation (5) does not hold. When the X-ray imaging is performed in the imaging mode number 24, Tf=Tf24, and therefore the expression (5) is established. When the expression (5) is not established, the read determination unit 111 ends the process here, and the apparatus control unit 107 captures the X-ray image data by a normal method. The normal imaging of X-ray image data will be described later in detail with reference to FIG. When Expression (5) is satisfied, the device control unit 107 calculates the time Ti (FIG. 5) of Expression (6) below.
Ti=Tf-Tc-Tr (6)

Here, the time Ti indicates the time from the reading of the X-ray imaged image data to the reading not used for generating the X-ray image. Imaging of the time Ti and the X-ray image data will be described later in detail with reference to FIG.

FIG. 3 is a timing chart for explaining the image pickup of the X-ray image data of the image pickup mode number 23, and shows the processing method of the radiation image pickup apparatus. First, the image capturing mode setting unit 112 sets the image capturing mode of the image capturing mode number 23 according to the operation of the operator. As already described, in the case of the imaging mode number 23, the equation (5) does not hold, and in this case, the radiation imaging apparatus images the X-ray image data by a normal method.

In FIG. 3, the switch signal becomes high level when the irradiation switch 103 is pressed. The X-ray irradiation control unit 101 outputs the switch signal to the X-ray flat panel detector 105 via the device control unit 107. The synchronization signals Syn1 to Syn4 are signals that the device control unit 107 outputs to the X-ray flat panel detector 105. The device control unit 107 sets the synchronization signals Syn1 to Syn4 to a high level at a frame rate of 15 fps. Then, the X-ray flat panel detector 105 starts reading the image data in synchronization with the synchronization signals Syn1 to Syn4. The read signals Rx0 to Rx3 are signals that the X-ray flat panel detector 105 outputs to the apparatus control unit 107, and become high level when the X-ray flat panel detector 105 reads out image data. However, the data collected by the read signal Rx0 for reading the first image data is not used as the image data, and is used as the image data after the second read signal Rx1 shown by the mesh.

The X-ray permission signal is a signal output from the X-ray flat panel detector 105 to the apparatus control unit 107, and becomes a high level when X-ray irradiation is permitted. In the case of X-ray imaging, the X-ray flat panel detector 105 sets the X-ray permission signal to the high level when the read signals Rx0 to Rx3 become the low level, and immediately before the synchronization signals Syn2 to Syn4 become the high level, the X-ray permission is set. Set the signal to low level. Therefore, the time when the X-ray permission signal is at the high level is the same as the charge accumulation time Tc. The X-ray signals X1 to X3 are signals that the device control unit 107 outputs to the X-ray irradiation control unit 101, and when the X-ray signals X1 to X3 become high level, the X-ray tube 102 irradiates X-rays. In the case of X-ray imaging, the device control unit 107 sets the X-ray signal to the high level when the switch signal and the X-ray permission signal become the high level and irradiates the X-ray for a predetermined time, and then sets the X-ray signal to the low level. To do. The maximum time of the time Tx when the X-ray signal is at the high level is the same as the time when the X-ray permission signal is at the high level. Further, by changing the mAs value described with reference to FIG. 2, it is possible to change the time Tx at which the X-ray permission signal becomes high level. For example, when the value of mAs is set to 3 mAs, when the tube current is 5 mA and the frame rate is 15 fps, the X-ray irradiation time becomes high level for 40 ms. The X-ray irradiation time Tx (second) can be calculated by the following equation (7) using the mAs value, the tube current (mA), and the frame rate (fps).
Tx=mAs value/(tube current×frame rate) (7)

Then, the apparatus control unit 107 performs offset correction by subtracting the offset data stored in the offset data storage unit 110 from the input X-ray image data (Rx1 to Rx3). At this time, the offset data collected in the imaging mode number 23 is used for the offset correction. Further, X-ray irradiation and X-ray image data reading are performed while the switch signal is at a high level.

FIG. 4 is a timing chart for explaining the collection of the offset data of the imaging mode number 23, showing the processing method of the radiation imaging apparatus. In FIG. 4, the switch signal, the synchronization signal, the X-ray permission signal, and the X-ray signal are the same as those in FIG. 3, but in the case of offset data acquisition, the switch signal, the X-ray permission signal, and the X-ray signal are low. It remains at the level. Further, the device control unit 107 automatically collects the offset data of the imaging mode number stored in the offset mode storage unit 109. The offset mode storage unit 109 stores four imaging mode numbers 14, 23, 32, 41, which are less than the 22 imaging modes in FIG. Imaging mode numbers for collecting offset data are imaging mode numbers 14, 23, 32, and 41 stored in the offset mode storage unit 109. The offset data storage means 110 stores the offset data of the imaging mode stored in the offset mode storage means 109. That is, the offset data storage unit 110 stores the offset data of the four imaging mode numbers 14, 23, 32, and 41, which are less than the 22 imaging modes of FIG. As an example, a timing chart at the time of collecting offset data of imaging mode number 23 will be described.

In the case of the imaging mode number 23, the device control unit 107 outputs the synchronization signals Syn1 to Syn4 to the X-ray flat panel detector 105 at a frame rate of 15 fps. The X-ray flat panel detector 105 reads the offset data (Rd0 to Rd3) in synchronization with the synchronization signals Syn1 to Syn4 without irradiating the X rays. However, the data collected in the first read of the offset data (Rd0) is not used as the offset data, and the offset data is used after the second read (Rd1) shown by the mesh.

In FIG. 4, only the reading (Rd4) is drawn, but when the number of frames for collecting the offset data is 16, the same process is repeated until the offset data reading (Rd16). Then, the apparatus control unit 107 calculates the arithmetic mean of the 16 pieces of offset data input from the X-ray flat panel detector 105, and stores the arithmetic mean offset data in the offset data storage means 110. The offset data storage means 110 calculates an average of one frame image generated by the X-ray plane detector 105 or images of a plurality of frames generated by the X-ray plane detector 105 in a state where the X-ray generation unit 104 does not emit radiation. Store as offset data.

After that, the device control unit 107 collects offset data of different imaging mode numbers 41, 14, and 32. However, the order of collecting the offset data is not limited to this. Further, when the collection of all the offset data is completed, the X-ray flat panel detector 105 periodically reads in synchronization with the synchronization signal, but the data read at that time is discarded.

For example, the timing at which the offset data is first acquired is the timing at which the power of the X-ray flat panel detector 105 is turned on and the state of the X-ray flat panel detector 105 is stable. The timing at which the offset data is updated is the timing at which the afterimage of the X-ray flat panel detector 105 is reduced after a predetermined time has elapsed after the X-ray irradiation.

FIG. 5 is a timing chart for explaining the imaging of X-ray image data of imaging mode number 24, and shows the processing method of the radiation imaging apparatus. This processing is processing when the conditional expression of the above expression (5) is satisfied. In FIG. 5, the switch signal, the synchronization signal, the X-ray permission signal, and the X-ray signal are the same as those described in FIG. Further, as described above, in the case of the imaging mode number 24, the above expression (5) is established, and in this case, the X-ray image data is imaged by the method according to the present embodiment.

The image capturing mode setting means 112 sets the image capturing mode of one image capturing mode number 24 out of the 22 image capturing modes of FIG. 10 according to the operation of the operator. Then, the device control unit 107 outputs the synchronization signal to the X-ray flat panel detector 105 at a cycle of 10 fps. Next, when the operator presses the irradiation switch 103, the switch signal becomes high level. Then, the X-ray flat panel detector 105 converts radiation into electric charges in the imaging mode set by the imaging mode setting unit 112, starts reading an X-ray image for imaging, and generates an image. However, the X-ray flat panel detector 105 performs the same reading (Ri0) that is not used for generating the X-ray image after the first reading (Rx0), and then performs the reading (Rx1, Ri1, Rx2, Ri2,... ). )repeat. The read (Rx0, Rx1) time Tr used for image generation of the X-ray flat panel detector 105 is equal to the read (Ri0, Ri1) time Tr not used for image generation.

The reading (Ri0) performed by the X-ray flat panel detector 105 is performed to make the charge accumulation time Tc the same as that of the imaging mode number 23, and is not used for offset correction or generation of an X-ray image. Further, the time Ti from the start of the first read (Rx0) to the start of the read (Ri0) is the time calculated by the above equation (6), and specifically, Ti=33.3 (ms). Is. As described above, the X-ray flat panel detector 105 reads out (Rx0, Rx1) used for image generation and does not use for image generation within one frame based on the image capturing mode set by the image capturing mode setting unit 112. Ri0, Ri1) is performed. As a result, the X-ray flat panel detector 105 generates an image at the same charge accumulation time Tc as the image capturing mode of the image capturing mode number 23 in which the offset data is stored in the offset data storage unit 110.

Then, the offset correction means 108 corrects the image generated by the X-ray flat panel detector 105 using the offset data stored in the offset data storage means 110. Specifically, the offset correction means 108 performs offset correction by subtracting the offset data stored in the offset data storage means 110 from the X-ray images (Rx1 to Rx) generated by the X-ray flat panel detector 105. To do. At this time, the offset data used for the offset correction is the offset data collected in the imaging mode number 23. The offset data collected in the imaging mode number 23 can be used for offset correction by reading out so that the charge accumulation time Tc of the imaging mode number 24 described in FIG. 5 becomes the same as the charge accumulation time Tc of the imaging mode number 23 ( This is because Ri0) is performed. That is, the image reading size, gain, binning mode, and charge storage time Tc of the X-ray flat panel detector 105 are the same.

Similarly, the X-ray image data captured in the imaging mode numbers 25 to 27 can be offset-corrected by the offset data collected in the imaging mode number 23. Further, if there is the offset data collected in the imaging mode number 14, the X-ray image data imaged in the imaging mode numbers 15 to 17 can be offset-corrected. Further, if there is offset data collected in the imaging mode number 32, the X-ray image data captured in the imaging mode numbers 33 to 37 can be offset-corrected. Further, if there is the offset data collected in the imaging mode number 41, the X-ray image data captured in the imaging mode numbers 42 to 47 can be offset-corrected.

FIG. 6 is a diagram showing a time required for collecting offset data in the case of the present embodiment. The offset data storage unit 110 stores the offset data of the four imaging mode numbers 14, 23, 32, and 41, which are smaller than the 22 imaging modes of FIG. The offset data storage unit 110 picks up the image at the highest frame rate among the image reading size of the X-ray flat panel detector 105, the binning mode, and the image pickup mode in which the gain for amplifying the image signal is the same and the frame rate is different. Store the offset data of the mode. The offset data storage unit 110 has one image pickup mode among the image pickup size of the X-ray flat panel detector 105, the binning mode, and the image pickup modes having the same gain for amplifying the image signal and different frame rates. Store the offset data. As described above, the offset data to be collected in advance is of four types of imaging mode numbers 14, 23, 32, and 41, and the other imaging mode numbers are not collected, so the time is set to 0. In addition, when the offset correction data is added and averaged over 16 frames, the time required to collect the offset data can be shortened to 1.6+1.1+0.8+0.5=4 seconds as compared with FIG.

The imaging mode includes the image reading size of the X-ray flat panel detector 105, the binning mode, the gain for amplifying the image signal, or the frame rate. The imaging mode setting unit 112 sets at least one of the image reading size of the X-ray flat panel detector 105, the binning mode, the gain for amplifying the image signal, and the frame rate as the imaging mode. The offset data storage unit 110 stores, as offset data, an image generated by the X-ray flat panel detector 105 for each image reading size of the X-ray flat panel detector 105, each binning mode, or each gain without irradiation of radiation. can do.

Although the offset correction unit 108, the offset mode storage unit 109, the offset data storage unit 110, and the read determination unit 111 have been described as being inside the device control unit 107, the present invention is not limited thereto, and the X-ray plane detection is performed. It may be in the container 105.

Further, although the timing chart at the time of image capturing and offset correction has been described using the switch signal, the synchronization signal, the read signal, the X-ray permission signal, and the X-ray signal, the present invention is not limited to this. For example, the apparatus control unit 107 can implement the present embodiment even in a configuration having no synchronization signal by transmitting the imaging mode number for imaging to the X-ray flat panel detector 105 by command communication. Further, the X-ray permission signal has been described as a signal output from the X-ray flat panel detector 105 to the apparatus control unit 107, but the X-ray flat panel detector 105 is not limited to this. May be output to.

Further, although the offset data used for the offset correction is described as an average value of 16 frames, it is not limited to this and may be an average value of 8 frames, for example, and the number of frames may differ for each imaging mode number. Good. Although the imaging mode of the radiation imaging apparatus has been described as the 22 mode, it is not limited to this and may be, for example, 20 modes without the imaging mode numbers 37 and 47.

Further, although it has been described that the gain is determined when the image reading size of the X-ray flat panel detector 105 and the binning mode are determined, the present invention is not limited to this, and the gain may be set individually. However, as the number of types of gain increases, the number of types of offset data collected in advance and the imaging mode also increases, so the time required to collect offset data increases.

(Second embodiment)
The radiation imaging apparatus according to the second embodiment of the present invention will be described below. In the second embodiment, the radiation image pickup apparatus, the image pickup mode shown in FIG. 10, and the offset correction method are the same as those in the first embodiment. In the first embodiment, the imaging mode number stored in the offset mode storage unit 109 is the mode in which the frame rate is the fastest in each image reading size of the X-ray flat panel detector 105 and each binning mode. Are imaging mode numbers 14, 23, 32, and 41. However, for example, when the X-ray image data is imaged in the imaging mode number 27, if offset correction is performed using the offset data collected in the imaging mode number 23, the maximum time of the X-ray irradiation time Tx becomes the charge accumulation time Tc. The same is 46.7 ms. Therefore, when it is desired to perform imaging with a long X-ray irradiation time Tx when the frame rate is low, for example, offset data of imaging mode number 26 is collected in advance. Then, the offset correction of the X-ray image data imaged in the imaging mode number 27 can be applied to the imaging in which the X-ray irradiation time Tx is long by using the offset data collected in the imaging mode number 26. Specifically, in the case of the imaging mode number 26, assuming that the time of one frame is Tf26 and the charge accumulation time is Tc26, the times Tf26 and Tc26 have the following values, respectively.
Tf26=333.3 (ms)
Tc26=313.3 (ms)
Therefore, the maximum X-ray irradiation time Tx is 313.3 ms, which is the same as the charge storage time Tc26.

FIG. 7 is a diagram showing a time required for offset data collection in the case of the second embodiment. In FIG. 7, the offset data to be collected in advance is eight types of imaging mode numbers 14, 16, 23, 26, 32, 36, 41, and 46, and the other imaging mode numbers are not collected, so the time is set to 0. When the offset correction data is averaged over 16 frames, the total time required for collecting the offset data is 25.2 seconds.

The X-ray image data captured in the imaging mode numbers 14 and 15 is offset-corrected using the offset data collected in the imaging mode number 14. Further, the X-ray image data acquired in the imaging mode numbers 16 and 17 is offset-corrected using the offset data acquired in the imaging mode number 16. The same applies to other imaging modes.

Therefore, the imaging mode number at the time of imaging and the imaging mode number at the time of collecting offset data are compared. The X-ray flat panel detector 105 uses the same image reading size, gain, and binning mode, and uses offset correction data of the frame rate at the time of collecting offset data that is faster than the frame rate at the time of imaging. When there are a plurality of frame rates at the time of collecting the fast offset data, the offset data collected at the slow frame rate is used.

The offset data storage unit 110 has a plurality (two) of image reading sizes of the X-ray flat panel detector 105, a binning mode, and an imaging mode in which the gain for amplifying an image signal is the same and the frame rate is different. The offset data of the imaging mode is stored.

In the above description, the imaging mode numbers stored in the offset mode storage unit 109 have been described as 14, 16, 23, 26, 32, 36, 41, 46, but the invention is not limited to this, and the operator or the radiation. The installer of the image pickup apparatus may freely change it according to the application.

(Third Embodiment)
The radiation imaging apparatus according to the third embodiment of the present invention will be described below. In the third embodiment, the radiation image pickup apparatus, the image pickup mode in FIG. 10, the difference image mode number stored in the offset mode storage unit 109, and the offset correction method are the same as those in the first embodiment.

FIG. 8 is a timing chart for explaining imaging of X-ray image data of imaging mode number 25. In FIG. 8, in the case of imaging X-ray image data of imaging mode number 25, the X-ray flat panel detector 105 performs reading (Rx0) used for image generation within one frame, and then a plurality of ( For example, the reading (Ri01, Ri02) is performed twice. Further, in FIG. 8, only the reading (Rx0) to the reading (Ri11) are drawn, but thereafter, this reading is repeated.

Then, the time Ti from the start of the first read (Rx0) to the start of the read (Ri01) is equal to the time Ti25 from the start of the read (Ri01) to the start of the read (Ri02). To do. In this case, it is the time Ti25 and the time calculated by the following equation (8).
Ti25=(Tf-Tc-Tr)/2 (8)

When actually calculated, Ti25=66.7 (ms). However, when the time from the start of the read (Rx0) to the start of the read (Ri01) and the time from the start of the read (Ri01) to the start of the read (Ri02) are the same time, it is calculated by Equation (8). It's time. However, the present invention is not limited to this, and the charge storage time Tc=46.7 ms may be established.

Further, the number Ni of reading (Ri01, Ri02) performed after reading (Rx0) within one frame time Tf can be increased. The number of times Ni can be calculated by the following equation (9).
Ni={(Tf-Tc)/Tr}-1 (9)

Here, Ni is an integer rounded down after the decimal point, and is 6 in the case of the imaging mode number 25. Therefore, in the case of the imaging mode number 25, the X-ray flat panel detector 105 can perform reading (Ri01 to Ri06) up to 6 times after reading (Rx0). When the reading (Ri01, Ri02,...) Is performed, the afterimage of the X-ray flat panel detector 105 tends to be reduced quickly. Therefore, the number of times of reading may be appropriately determined by examining the image quality.

Further, the read (Ri01, Ri02) has been described as the same read as the read (Rx0), but the read (Ri01) may be read at a higher speed than the read (Rx0). However, even in that case, the read (Ri02) immediately before the charge accumulation needs to be the same as the read (Rx0).

(Fourth Embodiment)
The radiation imaging apparatus according to the fourth embodiment of the present invention will be described below. In the fourth embodiment, the radiation imaging apparatus, the imaging mode number stored in the offset mode storage unit 109, and the offset correction method are the same as those in the first embodiment. The difference between the fourth embodiment and the first embodiment is that an image can be picked up at a frame rate other than the image pickup mode shown in FIG. 10, and therefore the image pickup mode setting means 112 is not the image pickup mode shown in FIG. You can set the frame rate of.

FIG. 9 is a timing chart for explaining imaging of X-ray image data having a frame rate of 11 fps. However, the image reading size, gain, and binning mode of the X-ray flat panel detector 105 are the same as those of the imaging mode number 23, and only the frame rate is different from that of the imaging mode number 23.

In FIG. 9, the imaging mode setting unit 112 sets 11 fps as a frame rate according to the operation of the operator. Then, the device control unit 107 outputs the synchronization signals Syn1 to Syn3 to the X-ray flat panel detector 105 at a frame rate of 11 fps. Then, when the operator presses the irradiation switch 103, the switch signal becomes high level, and the X-ray flat panel detector 105 reads out (Rx0, Ri0, Rx1, Ri1,... In synchronization with the synchronization signals Syn1 to Syn3.・) Start. Further, the read determination means 111 determines whether or not the above expression (5) is established, and in the case of the fourth embodiment, the above expression (5) is established. Therefore, when the above formula (6) is calculated and calculated, Ti=24.2 (ms). Therefore, the time Ti from the start of reading (Rx0) to the start of reading (Ri0) is 24.2 (ms).

In FIG. 9, the offset data collected in advance is the same as that in the first embodiment, so the time required to collect the offset data is 4 seconds. Therefore, it is possible to capture X-ray image data at various frame rates without increasing the time required to collect offset data. Although the frame rate has been described as 11 fps in the above description, the frame rate is not limited thereto, and the X-ray image data may be captured at an arbitrary frame rate if the frame rate satisfies the above equation (5). You can

According to the first to fourth embodiments, it is possible to perform imaging in many imaging modes, but it is possible to reduce the types of offset data collected in advance and to shorten the time required to update the offset data. The radiation imaging apparatus can be used as a medical or industrial nondestructive inspection apparatus.

It should be noted that each of the above-described embodiments is merely an example of an embodiment for carrying out the present invention, and the technical scope of the present invention should not be limitedly interpreted by these. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

105 X-ray flat panel detector, 107 Device control unit, 108 Offset correction means, 109 Offset mode storage means, 110 Offset data storage means, 111 Read determination means, 112 Imaging mode setting means

Claims (14)

Imaging mode setting means for setting one imaging mode among a plurality of imaging modes;
A radiation detector that generates an image by converting radiation into electric charges in the imaging mode set by the imaging mode setting means;
Offset data storage means for storing offset data in an imaging mode smaller than the plurality of imaging modes,
Offset correction means for correcting the image generated by the radiation detector using the offset data stored in the offset data storage means,
And a control unit that controls the radiation detector so as to perform reading used for image generation and reading not used for image generation within one frame based on the set imaging mode.
The control unit controls the radiation detector so as to perform the reading used for image generation and the reading not used for image generation within the one frame, so that the offset data is stored in the offset data storage unit. Generate an image with the same charge accumulation time as the mode,
The read time Tr used for image generation of the radiation detector is equal to the read time Tr not used for image generation,
Further, reading for determining whether or not the conditional expression of Tf−2×Tr≧Tc is satisfied based on the frame time Tf of one frame based on the image capturing mode set by the image capturing mode setting means and the charge accumulation time Tc. Has a judging means,
It said radiation detector, if the conditional expression is satisfied, to that radiological imaging apparatus, wherein the reading out is not used to read an image generating used for image generation in one frame. The radiation detector, when the conditional expression is satisfied, performs reading not used for the image generation after reading used for the image generation,
Said time Ti from the start of the reading used for image generation and the start of reading is not used in the image generation, radiation imaging apparatus according to claim 1, characterized in that the Ti = Tf-Tc-Tr. Imaging mode setting means for setting one imaging mode among a plurality of imaging modes;
A radiation detector that generates an image by converting radiation into electric charges in the imaging mode set by the imaging mode setting means;
Offset data storage means for storing offset data in an imaging mode smaller than the plurality of imaging modes,
Offset correction means for correcting the image generated by the radiation detector using the offset data stored in the offset data storage means,
And a control unit that controls the radiation detector so as to perform reading used for image generation and reading not used for image generation within one frame based on the set imaging mode.
The offset data storage means is the image reading mode of the fastest frame rate among the image reading size of the radiation detector, the binning mode, and the imaging mode in which the gain for amplifying the image signal is the same and the frame rate is different. you and to store the offset data radiological imaging apparatus. Imaging mode setting means for setting one imaging mode among a plurality of imaging modes;
A radiation detector that generates an image by converting radiation into an electric charge in the imaging mode set by the imaging mode setting means;
Offset data storage means for storing offset data in an imaging mode smaller than the plurality of imaging modes,
Offset correction means for correcting the image generated by the radiation detector using the offset data stored in the offset data storage means,
And a control unit that controls the radiation detector so as to perform reading used for image generation and reading not used for image generation within one frame based on the set imaging mode.
The offset data storage means stores the offset data of one imaging mode among the imaging modes in which the image reading size of the radiation detector, the binning mode, and the gain for amplifying the image signal are the same and the frame rate is different. you and to store the radiological imaging apparatus. Imaging mode setting means for setting one imaging mode among a plurality of imaging modes;
A radiation detector that generates an image by converting radiation into electric charges in the imaging mode set by the imaging mode setting means;
Offset data storage means for storing offset data in an imaging mode smaller than the plurality of imaging modes,
Offset correction means for correcting the image generated by the radiation detector using the offset data stored in the offset data storage means,
And a control unit that controls the radiation detector so as to perform reading used for image generation and reading not used for image generation within one frame based on the set imaging mode.
The offset data storage means stores the offset data of a plurality of imaging modes among the imaging modes in which the image readout size of the radiation detector, the binning mode, and the gain for amplifying the image signal are the same and the frame rates are different. you and to store radiological imaging apparatus. Imaging mode setting means for setting one imaging mode among a plurality of imaging modes;
A radiation detector that generates an image by converting radiation into an electric charge in the imaging mode set by the imaging mode setting means;
Offset data storage means for storing offset data in an imaging mode smaller than the plurality of imaging modes,
Offset correction means for correcting the image generated by the radiation detector using the offset data stored in the offset data storage means,
And a control unit that controls the radiation detector so as to perform reading used for image generation and reading not used for image generation within one frame based on the set imaging mode.
It said radiation detector to that radiological imaging apparatus and performing a plurality of read without using the read image generated for use in image generation in one frame. The imaging mode includes an image readout size of the radiation detector,
The offset data storage means, in a state in which radiation is not irradiated, claims and to store the images the radiation detector is generated for each image read size of the radiation detector as an offset data 1-6 The radiation imaging apparatus according to claim 1. The imaging mode includes a binning mode,
The offset data storage means, in a state in which radiation is not irradiated, any one of claim 1 to 7, characterized in that for storing an image in which the radiation detector is generated for each said binning mode as offset data The radiation imaging apparatus according to. The imaging mode includes a gain for amplifying an image signal,
The offset data storage means, in a state in which radiation is not irradiated, to any one of claims 1 to 8, characterized in that for storing an image generated by said radiation detector for each of the gain as offset data The radiation imaging apparatus described. The image pickup mode setting means sets at least one of an image read size of the radiation detector, a binning mode, a gain for amplifying an image signal, and a frame rate as the image pickup mode. the radiation imaging apparatus according to any one of 1-9. The offset data storage means stores, as offset data, an image of one frame generated by the radiation detector or an average of images of a plurality of frames generated by the radiation detector in a state where no radiation is applied. the radiation imaging apparatus according to any one of claims 1 to 10,. Said offset correction means, claim 1-11, characterized in that performing the correction by subtracting the offset data stored from the generated image on the offset data storage means by said radiation detector The radiation imaging apparatus according to item 1. Furthermore, it has an imaging mode storage means for storing imaging modes smaller than the plurality of imaging modes,
The offset data storage means, a radiation imaging apparatus according to any one of claims 1 to 12, characterized in that for storing offset data of an imaging mode wherein imaging mode storage means stores. Imaging mode setting means for setting one imaging mode among a plurality of imaging modes;
A radiation detector that generates an image by converting radiation into an electric charge in the imaging mode set by the imaging mode setting means;
A processing method of a radiation imaging apparatus, comprising: an offset data storage unit that stores offset data in an imaging mode smaller than the plurality of imaging modes,
A step of controlling the radiation detector by the control means so as to perform reading used for image generation and reading not used for image generation within one frame based on the set imaging mode;
The offset correction means, by using the offset data stored in the offset data storage means, possess a step of correcting the image generated by the radiation detector,
The control unit controls the radiation detector so as to perform the reading used for image generation and the reading not used for image generation within the one frame, and thus the offset data storage unit stores the offset data. Generate an image with the same charge accumulation time as the mode,
The read time Tr used for image generation of the radiation detector is equal to the read time Tr not used for image generation,
Based on the frame time Tf of one frame based on the imaging mode set by the imaging mode setting means and the charge storage time Tc, the read determination means determines whether or not the conditional expression of Tf−2×Tr≧Tc is satisfied. Judge,
A processing method of a radiation imaging apparatus, wherein the radiation detector performs reading used for image generation and reading not used for image generation within one frame when the conditional expression is satisfied .

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