Radiation imaging apparatus, radiation imaging system, and control method for radiation imaging apparatus

Abstract

To make it possible to calculate the cumulative irradiation dose with high accuracy.SOLUTION: A radiation imaging apparatus has a detection pixel that generates a signal on the basis of radiation and a signal processing unit for calculating the cumulative irradiation dose on the basis of the irradiation dose based on the signal of the detection pixel and a correction value based on the signal of the detection pixel during a correction period. The signal processing unit determines the correction period on the basis of the differential value of the signal based on the signal of the detection pixel.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a radiation imaging device, a radiation imaging system, and a control method for a radiation imaging device.

Background Art

[0002] Currently, as a radiation imaging device used for medical image diagnosis and non-destructive inspection by radiation such as X-rays, a radiation imaging device equipped with a flat panel detector (FPD) formed of a semiconductor material has become widespread.

[0003] Among radiation imaging devices, there are those that monitor the dose (cumulative dose) of irradiated radiation and stop the radiation irradiation when the cumulative dose reaches a threshold value (for example, output an irradiation stop signal for stopping the radiation irradiation to a radiation generation device). This operation is called automatic exposure control (AEC), and by this, for example, over-irradiation of radiation can be suppressed.

[0004] As such a radiation imaging device, for example, a radiation imaging device including a dose detection unit that detects the dose of radiation reaching the imaging region within the imaging region of an FPD is known. For example, the radiation dose is monitored by operating only the pixels set for radiation detection at high speed during radiation irradiation.

[0005] Patent Document 1 describes a radiation imaging device that performs an operation of monitoring the radiation dose only for pixels for radiation detection during the reset operation of each pixel and acquiring an offset component before receiving a request for starting radiation irradiation.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The radiation imaging apparatus of Patent Document 1 acquires an offset component of an operation for monitoring a radiation dose. However, when the time elapsed from the offset acquisition to the actual correction becomes large, the correction accuracy of the signal may decrease due to a temperature drift component of the pixel or the like. Although the method for acquiring the offset component of Patent Document 1 mentions accuracy, there is room for improving the acquisition timing in order to improve the correction accuracy.

[0008] An object of the present disclosure is to enable calculation of a highly accurate integrated radiation dose.

Means for Solving the Problems

[0009] The radiation imaging apparatus includes a detection pixel that generates a signal based on radiation, an irradiation dose based on the signal of the detection pixel, and a signal processing unit that calculates an integrated irradiation dose based on a correction value based on the signal of the detection pixel during a correction period. The signal processing unit determines the correction period based on a differential value of a signal based on the signal of the detection pixel.

Effects of the Invention

[0010] According to the present disclosure, a highly accurate integrated radiation dose can be calculated.

Brief Description of the Drawings

[0011]

Figure 1

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Figure 10

Embodiments for Carrying Out the Invention

[0012] Embodiments will be described below with reference to the drawings. The same elements are denoted by the same reference numerals throughout the various embodiments, and duplicate descriptions are omitted. Also, the respective embodiments can be appropriately modified and combined.

[0013] (First Embodiment) FIG. 1 is a diagram showing a configuration example of a radiation imaging apparatus 100 according to the first embodiment. The radiation imaging apparatus 100 includes an imaging region IR, a power supply circuit 140, a drive circuit 150, a readout circuit 160, a signal processing unit 170, and a control unit 180. The communication interface 503 in FIG. 5 is connected to the control unit 180.

[0014] The radiation imaging apparatus 100 includes a plurality of pixels arranged in the imaging region IR so as to form a plurality of rows and a plurality of columns, a plurality of drive lines 110, and a plurality of signal lines 120. The plurality of drive lines 110 are arranged corresponding to the plurality of rows of pixels, and each drive line 110 corresponds to any one row of pixels. The plurality of signal lines 120 are arranged corresponding to the plurality of columns of pixels, and each signal line 120 corresponds to any one column of pixels.

[0015] The plurality of pixels include a plurality of imaging pixels 101 used for acquiring a radiation image, one or more detection pixels 104 used for monitoring the radiation dose, and one or more correction pixels 107 used for correcting the radiation dose. The sensitivity of the correction pixel 107 to radiation is lower than the sensitivity of the detection pixel 104 to radiation.

[0016] The imaging pixel 101 includes a conversion element 102 that converts radiation into an electrical signal, and a switch element 103 that connects the corresponding signal line 120 and the conversion element 102 to each other. The detection pixel 104 includes a conversion element 105 that converts radiation into an electrical signal, and a switch element 106 that connects the corresponding signal line 120 and the conversion element 105 to each other. The detection pixel 104 is arranged to be included in rows and columns composed of a plurality of imaging pixels 101. The correction pixel 107 includes a conversion element 108 that converts radiation into an electrical signal, and a switch element 109 that connects the signal line 120 and the conversion element 108 to each other. The correction pixel 107 is arranged to be included in rows and columns composed of a plurality of imaging pixels 101.

[0017] In FIG. 1 and subsequent drawings, the imaging pixel 101, the detection pixel 104, and the correction pixel 107 are distinguished by applying different hatchings to the conversion element 102, the conversion element 105, and the conversion element 108.

[0018] The conversion element 102, the conversion element 105, and the conversion element 108 may be constituted by a scintillator that converts radiation into light and a photoelectric conversion element that converts light into an electrical signal. The scintillator is generally formed in a sheet shape so as to cover the imaging region IR and is shared by a plurality of pixels. Alternatively, the conversion element 102, the conversion element 105, and the conversion element 108 may be constituted by conversion elements that directly convert radiation into electrical signals.

[0019] The switch element 103, the switch element 106, and the switch element 109 may include, for example, a thin film transistor (TFT) in which an active region is constituted by a semiconductor such as amorphous silicon or polycrystalline silicon.

[0020] The first electrode of the conversion element 102 is connected to the first main electrode of the switch element 103, and the second electrode of the conversion element 102 is connected to the bias line 130. One bias line 130 extends in the column direction and is commonly connected to the second electrodes of a plurality of conversion elements 102 arranged in the column direction. The bias line 130 receives a bias voltage Vs from the power supply circuit 140. The second main electrodes of the switch elements 103 of one or more imaging pixels 101 included in one column are connected to one signal line 120. The control electrodes of the switch elements 103 of one or more imaging pixels 101 included in one row are connected to one drive line 110.

[0021] The detection pixel 104 and the correction pixel 107 also have the same pixel configuration as the imaging pixel 101 and are connected to the corresponding drive line 110 and the corresponding signal line 120. The detection pixel 104 and the correction pixel 107 are exclusively connected to the signal line 120. That is, the correction pixel 107 is not connected to the signal line 120 to which the detection pixel 104 is connected. Also, the detection pixel 104 is not connected to the signal line 120 to which the correction pixel 107 is connected. The imaging pixel 101 may be connected to the same signal line 120 as the detection pixel 104 or the correction pixel 107.

[0022] The drive circuit 150 is configured to supply a drive signal to the pixel to be driven through a plurality of drive lines 110 according to a control signal from the control unit 180. In this embodiment, the drive signal is a signal for turning on the switch element included in the pixel to be driven. The switch element of each pixel is turned on by a high-level signal and turned off by a low-level signal. Therefore, this high-level signal is called a drive signal. When a drive signal is supplied to the pixel, the signal accumulated in the conversion element of this pixel becomes readable by the readout circuit 160. When the drive line 110 is connected to at least one of the detection pixel 104 and the correction pixel 107, that drive line 110 is called a detection drive line 111.

[0023] The readout circuit 160 is configured to read signals from a plurality of pixels through a plurality of signal lines 120. The readout circuit 160 includes a plurality of amplification units 161, a multiplexer 162, and an analog-to-digital converter (hereinafter, referred to as an AD converter) 163. Each of the plurality of signal lines 120 is connected to a corresponding amplification unit 161 among the plurality of amplification units 161 of the readout circuit 160. One signal line 120 corresponds to one amplification unit 161.

[0024] The multiplexer 162 selects the plurality of amplification units 161 in a predetermined order and supplies the signals from the selected amplification units 161 to the AD converter 163. The AD converter 163 converts the supplied signal into a digital signal and outputs it to the signal processing unit 170.

[0025] The signal read from the imaging pixel 101 is supplied to the signal processing unit 170, and processing such as calculation and storage is performed by the signal processing unit 170. Specifically, the signal processing unit 170 includes an arithmetic unit 171 and a storage unit 172. The arithmetic unit 171 generates a radiation image based on the signal read from the imaging pixel 101 and supplies it to the control unit 180.

[0026] The signals read from the detection pixel 104 and the correction pixel 107 are supplied to the signal processing unit 170, and processing such as calculation and storage is performed by the arithmetic unit 171 thereof. Specifically, the signal processing unit 170 outputs information indicating the irradiation of radiation to the radiation imaging apparatus 100 to the control unit 180 based on the signals read from the detection pixel 104 and the correction pixel 107. For example, the signal processing unit 170 detects the irradiation of radiation to the radiation imaging apparatus 100, and determines the irradiation dose and / or the integrated irradiation dose of the radiation.

[0027] The control unit 180 controls the drive circuit 150 and the readout circuit 160 based on the information from the signal processing unit 170. The control unit 180 controls, for example, the start and end of exposure (accumulation of charges corresponding to the radiation irradiated by the imaging pixel 101) based on the information from the signal processing unit 170.

[0028] To determine the radiation dose, the control unit 180 controls the drive circuit 150 to scan only the detection drive line 111 and make it possible to read only the signals from the detection pixel 104 and the correction pixel 107. Next, the control unit 180 controls the readout circuit 160 to read the signals of the columns corresponding to the detection pixel 104 and the correction pixel 107 and outputs them as information indicating the radiation dose. By such an operation, the radiation imaging apparatus 100 can obtain the irradiation information in the detection pixel 104 during radiation irradiation.

[0029] FIG. 2 is a circuit diagram showing a configuration example of the amplification unit 161 in FIG. 1. The amplification unit 161 includes a differential amplification circuit AMP and a sample-and-hold circuit SH. The differential amplification circuit AMP amplifies and outputs the signal appearing on the signal line 120. The control unit 180 can reset the potential of the signal line 120 by supplying a control signal φR to the switch element of the differential amplification circuit AMP. The output from the differential amplification circuit AMP can be held by the sample-and-hold circuit SH. The control unit 180 causes the sample-and-hold circuit SH to hold a signal by supplying a control signal φSH to the switch element of the sample-and-hold circuit SH. The signal held in the sample-and-hold circuit SH is read out by the multiplexer 162.

[0030] With reference to FIGS. 3 and 4, a structural example of the pixel of the radiation imaging apparatus 100 will be described. FIG. 3 is a plan view showing a configuration example of the imaging pixel 101, the detection pixel 104, and the correction pixel 107 in the radiation imaging apparatus 100. The plan view of FIG. 3 is equivalent to a front projection onto a plane parallel to the imaging region IR of the radiation imaging apparatus 100. As shown by hatching, a metal layer is disposed on the conversion element 108 of the correction pixel 107, and the conversion element 108 is shielded from light by this metal layer.

[0031] FIG. 4(a) is a cross-sectional view of the imaging pixel 101 along the line A-A' in FIG. 3. The cross-sectional view of the detection pixel 104 is the same as that of the imaging pixel 101. A switch element 103 is disposed on an insulating support substrate 400 such as a glass substrate. The switch element 103 may be a TFT (Thin Film Transistor). An interlayer insulating layer 401 is disposed on the switch element 103. A conversion element 102 is disposed on the interlayer insulating layer 401. This conversion element 102 is a photoelectric conversion element capable of converting light into an electrical signal. The conversion element 102 is composed of, for example, an electrode 402, a PIN photodiode 403, and an electrode 404. Instead of being a PIN-type photodiode, the conversion element 102 may be composed of a MIS-type sensor.

[0032] On the conversion element 102, a protective film 405, an interlayer insulating layer 406, a bias line 130, and a protective film 407 are sequentially disposed. On the protective film 407, a planarization film and a scintillator (not shown) are disposed. The electrode 404 is connected to the bias line 130 through a contact hole. As the material of the electrode 404, ITO having light transmissibility is used, and it is possible to transmit the light converted from radiation by a scintillator (not shown).

[0033] FIG. 4(b) is a cross-sectional view of the correction pixel 107 along the line B-B' in FIG. 3. The correction pixel 107 is different from the imaging pixel 101 and the detection pixel 104 in that the conversion element 108 is covered by a light shielding member 408, and other points may be the same. The light shielding member 408 is formed of, for example, a metal layer in the same layer as the bias line 130. Since the conversion element 108 of the correction pixel 107 is covered by the light shielding member 408, the sensitivity of the correction pixel 107 to radiation is significantly lower than the sensitivities of the imaging pixel 101 and the detection pixel 104. It can also be said that the charge accumulated in the conversion element 108 of the correction pixel 107 is not caused by radiation.

[0034] FIG. 5 is a diagram showing a configuration example of a radiation imaging system 500 including a radiation imaging apparatus 100. The radiation imaging system 500 includes a radiation imaging apparatus 100, a radiation source 501, a radiation source interface 502, a communication interface 503, and a controller 504. The radiation source 501 irradiates radiation.

[0035] To the controller 504, the dose, the irradiation upper limit time (ms), the tube current (mA), the tube voltage (kV), a region of interest (ROI) which is a region to monitor radiation, etc. are input. When an exposure switch attached to the radiation source 501 is operated, the controller 504 transmits a start request signal to the radiation imaging apparatus 100. The start request signal is a signal requesting the start of radiation irradiation. The radiation imaging apparatus 100 starts preparing to receive radiation irradiation in response to receiving the start request signal. When the preparation is complete, the radiation imaging apparatus 100 transmits a startable signal to the radiation source interface 502 via the communication interface 503. The startable signal is a signal notifying that the start of radiation irradiation is possible. The radiation source interface 502 causes the radiation source 501 to start radiation irradiation in response to receiving the startable signal.

[0036] When the integrated value of the dose of the irradiated radiation reaches a threshold value, the radiation imaging apparatus 100 transmits an end request signal to the radiation source interface 502 via the communication interface 503. The end request signal is a signal requesting the end of radiation irradiation. The radiation source interface 502 causes the radiation source 501 to end radiation irradiation in response to receiving the end request signal. The threshold value of the integrated value of the dose is determined by the control unit 180 based on the input value of the dose, the radiation irradiation intensity, the communication delay between each unit, the processing delay, etc. When the irradiation time of the radiation reaches the input irradiation upper limit time, the radiation source 501 stops radiation irradiation even if it has not received the end request signal.

[0037] After the irradiation of radiation stops, the radiation imaging apparatus 100 sequentially scans the driving lines 110 (driving lines 110 other than the detection driving line 111) to which only the imaging pixels 101 are connected, and reads out the image signals of the respective imaging pixels 101 by the readout circuit 160, thereby acquiring a radiation image. The charges accumulated in the detection pixels 104 are read out during the irradiation of radiation, and since the correction pixels 107 are shielded from light, the signals from these pixels cannot be used for forming the radiation image. Therefore, the signal processing unit 170 of the radiation imaging apparatus 100 performs interpolation processing using the pixel values of the imaging pixels 101 around the detection pixels 104 and the correction pixels 107, thereby interpolating the pixel values at the positions of these pixels.

[0038] Referring to FIG. 6, a basic operation example of the radiation imaging apparatus 100 will be described. This operation is executed by the cooperation of a control unit 180 that controls the driving circuit 150 and the readout circuit 160, and a signal processing unit 170. Therefore, the combination of the signal processing unit 170 and the control unit 180 may be called an exposure determination unit. In FIG. 6, "radiation" indicates whether the radiation imaging apparatus 100 is irradiated with radiation. In the case of low, the radiation is not irradiated, and in the case of high, the radiation is irradiated.

[0039] "Vg1" to "Vgn" indicate the driving signals supplied from the driving circuit 150 to the plurality of driving lines 110. "Vgk" corresponds to the driving line 110 of the k-th row (k = 1,..., the total number of driving lines). As described above, a part of the plurality of driving lines 110 is also called a detection driving line 111. The j-th detection driving line 111 is represented as "Vdj" (j = 1,..., the total number of detection driving lines).

[0040] φSH indicates the level of the control signal supplied to the sample hold circuit SH of the amplifier unit 161. φR indicates the level of the control signal supplied to the differential amplifier circuit AMP of the amplifier unit 161.

[0041] The "detection pixel signal" indicates the value of the signal read from the detection pixel 104. The "correction pixel signal" indicates the value of the signal read from the correction pixel 107. The "integrated radiation dose" indicates the integrated value of the radiation irradiated on the radiation imaging apparatus 100. The method for determining this integrated value will be described later. The "radiation dose DOSE" represents the radiation calculated from the detection pixel signal and the correction pixel signal. The "differential value" is used to calculate the irradiation start point in the present embodiment, and the details will be described later.

[0042] At time t0, the control unit 180 starts the reset operation of a plurality of pixels. The reset operation is an operation for removing the charges accumulated in the conversion elements of each pixel. Specifically, it is to make the switch elements of each pixel in the conductive state by supplying a drive signal to the drive line 110. The control unit 180 controls the drive circuit 150 to reset each pixel connected to the drive line 110 of the first row. Subsequently, the control unit 180 resets each pixel connected to the drive line 110 of the second row. The control unit 180 repeats this operation until the drive line 110 of the last row.

[0043] At time t1, after the control unit 180 finishes the reset operation of the drive line 110 of the last row, it repeats the reset operation from the drive line 110 of the first row again.

[0044] At time t2, the control unit 180 receives a start request signal from the controller 504. In response to the reception of the start request signal, the control unit 180 performs the reset operation up to the last row and finishes the reset operation. The control unit 180 may finish the reset operation before performing the reset operation up to the last row and shift to the next process. For example, when the control unit 180 receives the start request signal during the reset operation of the drive line 110 of the k-th row, it may shift to the next process without performing the reset operation of the drive lines 110 after the (k + 1)-th row. In this case, the steps generated in the radiation image may be reduced by adjusting the drive for acquiring the radiation image and performing image processing on the radiation image.

[0045] At time t3, the control unit 180 starts a determination operation for determining the amount of radiation being irradiated to the radiation imaging apparatus 100. In the determination operation, the control unit 180 repeatedly executes a read operation for reading from the detection pixels 104 and the correction pixels 107. Among the multiple read operations, the first half of one or more read operations are performed to determine correction values, and the latter half of the repeated read operations are performed to continuously determine the amount of radiation at each time point.

[0046] The read operation is executed on the detection drive line 111 and not on the other drive lines 110. Specifically, the drive circuit 150 supplies a drive signal to the drive line 110 (i.e., the detection drive line 111) connected to at least one of the detection pixels 104 and the correction pixels 107 among the multiple drive lines 110. However, the drive circuit 150 does not supply a drive signal to the drive line 110 that is not connected to any of the detection pixels 104 and the correction pixels 107 among the multiple drive lines 110. Also, the drive circuit 150 simultaneously supplies a drive signal to the drive line 110 connected to at least one of the detection pixels 104 and the correction pixels 107 among the multiple drive lines 110. Thereby, signals from the multiple pixels connected to the same signal line 120 are combined and read out to the read circuit 160. Since the detection pixels 104 and the correction pixels 107 are exclusively connected to the signal line 120, the read circuit 160 can separate and read out the signals of pixels with different sensitivities.

[0047] In one read operation, the control unit 180 performs operations from time t3 to time t4. Specifically, the control unit 180 temporarily supplies a drive signal to one or more detection drive lines 111. Thereafter, the control unit 180 temporarily sets the control signal φSH to a high level to hold the signal read from the pixel through the signal line 120 in the sample-and-hold circuit SH. Thereafter, the control unit 180 temporarily sets the control signal φR to a high level to reset the read circuit 160 (specifically, the differential amplifier circuit AMP of its amplification unit 161). When a region of interest is set within the imaging region IR, it is not necessary to read signals from the detection pixels 104 not included in this region of interest.

[0048] The control unit 180 performs the read operation a predetermined number of times of one or more times to determine the correction value. The signal processing unit 170 determines a correction value Od based on the signal read from the detection pixel 104 by the read operation a predetermined number of times, and a correction value Oc based on the signal read from the correction pixel 107 by the read operation a predetermined number of times. The determination of the correction value Od will be described in detail. If the predetermined number of times is once, since there is one signal read from the detection pixel 104, the signal processing unit 170 sets the value of the signal as the correction value Od. When the predetermined number of times is plural, the signal processing unit 170 sets the average value of the plurality of read signals as the correction value Od. Other statistical values may be used instead of the average value. The correction value Oc is similarly determined based on the signal read from the correction pixel 107. The signal processing unit 170 stores the correction values Od and Oc thus determined in the storage unit 172 so that they can be used in subsequent processing.

[0049] When the read operation one or more times is completed, the control unit 180 transmits an enable signal to the radiation source interface 502 at time t5. The determination of the above-described correction values Od and Oc may be performed before or after the transmission of the enable signal. After transmitting the enable signal, the control unit 180 repeatedly executes the above-described read operation. The signal processing unit 170 measures the radiation dose DOSE for each read operation and determines whether the integrated value exceeds a threshold value. Radiation irradiation starts at time t6 after time t5.

[0050] The method for determining the radiation dose DOSE will be described below. Let the value of the signal read from the detection pixel 104 by the most recent read operation be represented by Sd. Let the value of the signal read from the correction pixel 107 by the most recent read operation be represented by Sc. The signal processing unit 170 calculates the radiation dose DOSE by applying Sd, Sc, Od, and Oc to the following formula (1).

[0051] DOSE = (Sd - Od) - (Sc - Oc) … Formula (1)

[0052] In this formula (1), DOSE is determined based on the difference between the value Sc of the signal read from the correction pixel 107 after transmitting the startable signal and the correction value Oc determined based on the signal read from the correction pixel 107 before transmitting the startable signal.

[0053] Alternatively, the signal processing unit 170 may calculate the irradiation dose DOSE by applying Sd, Sc, Od, and Oc to the following formula (2) instead of formula (1).

[0054] DOSE = Sd - Od × Sc / Oc … Formula (2)

[0055] In this formula (2), DOSE is determined based on the ratio between the value Sc of the signal read from the correction pixel 107 after transmitting the startable signal and the correction value Oc determined based on the signal read from the correction pixel 107 before transmitting the startable signal.

[0056] As described above, the signal processing unit 170 determines the correction value Od based on the signal of the detection pixel 104 acquired at the timing of a predetermined number of times and the correction value Oc based on the signal of the correction pixel 107 acquired at the timing of a predetermined number of times. Then, the signal processing unit 170 calculates the irradiation dose DOSE based on the correction value Od, the correction value Oc, the signal Sd of the detection pixel 104 acquired at the most recent timing, and the signal Sc of the correction pixel 107 acquired at the most recent timing.

[0057] As shown in FIG. 6, the signal read from the detection pixel 104 changes significantly with time immediately after the end of the reset operation (immediately after time t3) and stabilizes over time (for example, in about 100 ms). Therefore, even if DOSE is calculated using only Sd and Od obtained from the detection pixel 104, the offset amount cannot be sufficiently removed. If the start of the read operation for acquiring the correction value Od is delayed until the signal read from the detection pixel 104 stabilizes, the time from the transmission of the start request signal to the actual start of radiation irradiation (the time from time t2 to t6, so-called exposure delay) becomes long.

[0058] In this embodiment, the irradiation dose DOSE is determined using the values (Sc and Oc) of the signals read from the correction pixel 107. Since the correction pixel 107 has a very low sensitivity to radiation, the value Sc of the signal read from the correction pixel 107 after the start of radiation irradiation can be regarded as representing the offset component of the value Sd of the signal read from the detection pixel 104. Further, in this embodiment, the irradiation dose DOSE is determined using the correction values Od and Oc based on the signals read from the detection pixel 104 and the correction pixel 107 before the start of radiation irradiation. Thereby, differences in the inherent characteristics of each pixel (differences in the channels of the detection circuit, differences in the parasitic resistance and parasitic capacitance of each pixel, etc.) can be corrected.

[0059] When the integrated irradiation dose reaches the threshold value at time t7, the control unit 180 transmits an end request signal to the radiation source interface 502. Instead of this, the control unit 180 may estimate the time when the integrated irradiation dose reaches the threshold value and transmit the end request signal at this estimated time. At time t8, in response to the reception of the end request signal, the radiation source interface 502 causes the radiation source 501 to end the radiation irradiation.

[0060] In the above example, the control unit 180 starts a predetermined number of read operations for determining the correction values Od and Oc immediately after the end of the reset operation. Instead of this, the control unit 180 may start a predetermined number of read operations after a predetermined time (for example, several ms to several tens of ms) has elapsed after the end of the reset operation. Thereby, it is possible to suppress reading the signal during a period when the time variation is particularly large.

[0061] Here, by implementing as in the above example, it is possible to perform the determination of transmitting the end request signal. However, the greater the temporal interval between the correction value Od and the signal value Sd to be corrected, the more the correction accuracy may decrease. In particular, the integrated irradiation dose calculated from the irradiation dose DOSE in a state where the correction accuracy has decreased may have a larger error amount from the true value as the irradiation time becomes longer, so in diagnosis, it may lead to overexposure or underexposure.

[0062] Therefore, in the present embodiment, in view of the above problems, a method for accurately calculating the integrated radiation dose by calculating a correction value based on the radiation irradiation start timing will be described with reference to FIGS. 7, 8, and 9.

[0063] FIG. 7 is a flowchart showing a control method of the radiation imaging apparatus 100, and shows the determination and correction flow of the correction value during the period from time t3 to t7 in FIG. 6. The detection pixel 104 generates a signal based on radiation. The correction pixel 107 has lower sensitivity to radiation than the detection pixel 104. The conversion element 108 of the correction pixel 107 is, for example, shielded from light. The imaging pixel 101 generates a signal based on radiation. The signal processing unit 170 generates a radiation image based on the signals of the plurality of imaging pixels 101.

[0064] First, in step S701, the control unit 180 reads signal values Sd and Sc from the detection pixel 104 and the correction pixel 107 in order to calculate the radiation irradiation dose. Here, the signals Sd and Sc when radiation is not particularly irradiated are denoted as Sddark and Scdark using the subscript dark. Also, equations (1) and (2) can be similarly applied by adding the subscript dark. Since the specific signal reading method has been described above, it will be omitted.

[0065] Next, in step S702, the signal processing unit 170 calculates the integrated radiation dose. Specifically, the signal processing unit 170 calculates the irradiation dose DOSE in the arithmetic unit 171 based on the above-described equation (1) or equation (2) from the signal values read by the reading circuit 160. Then, the signal processing unit 170 calculates the integrated radiation dose by adding the irradiation dose DOSE at the sampling time point (hereinafter t) to the irradiation dose DOSE at one sampling before (t - 1). Specifically, the signal processing unit 170 performs the calculation according to equation (3). Also, the signal processing unit 170 calculates the integrated amount when radiation is not irradiated as the integrated dark amount by equation (4). Here, the integrated radiation dose (0), the integrated dark amount (0), the irradiation dose DOSE(0), and the irradiation dose DOSEdark(0) are all set to 0 values.

[0066] Integrated irradiation dose (t) = Integrated irradiation dose (t - 1) + DOSE(t) … Equation (3) Integrated dark amount (t) = Integrated dark amount (t - 1) + DOSEdark(t) … Equation (4)

[0067] Here, the irradiation dose DOSEdark is the irradiation dose DOSE when no radiation is being irradiated, and is calculated by Equation (1) or (2).

[0068] Next, in step S703, the signal processing unit 170 determines whether radiation is being irradiated. Specifically, in step S706 described later, the signal processing unit 170 determines the radiation irradiation start point, and determines that radiation is being irradiated when it is sampling after that radiation irradiation start point.

[0069] If it is determined in step S703 that no radiation is being irradiated, the process proceeds to step S704. If it is determined in step S703 that radiation is being irradiated, the process proceeds to step S710.

[0070] In step S704, the signal processing unit 170 stores the irradiation dose DOSEdark calculated at the sampling time (t) in the storage unit 172. Here, the value of the irradiation dose DOSEdark may be overwritten, or may be stored in the storage unit 172 for a predetermined number of samplings without overwriting.

[0071] Next, in step S705, the signal processing unit 170 calculates the difference, that is, the differential value, between the irradiation dose DOSEdark(t) at the sampling time (t) and the irradiation dose DOSEdark at a sampling time that is temporally different from the sampling time (t). In the present embodiment, the sampling times that are temporally different are described as the data one sampling before, but the present embodiment is not limited thereto. For example, the irradiation dose DOSEdark acquired at different timings in time series may be used, or for example, the irradiation dose DOSEdark acquired before a predetermined time may be used. Further, the differential value may be calculated with respect to the moving average value of the irradiation dose DOSEdark calculated at a predetermined interval.

[0072] The differential value is the difference between the signals based on the signals of the detection pixel 104 and the correction pixel 107 acquired at different timings. Further, the differential value may be the difference between the moving averages of the signals based on the signals of the detection pixel 104 and the correction pixel 107 acquired at different timings.

[0073] Specifically, the differential value is the differential value based on the irradiation dose DOSEdark, and is the differential value of the irradiation dose DOSEdark. Note that the differential value may be the difference between the moving averages of the irradiation dose DOSEdark.

[0074] Next, in step S706, the signal processing unit 170 compares whether the differential value calculated in step S705 is equal to or greater than a predetermined threshold. Here, if the predetermined threshold is Expst, the comparison is performed by the following formula (5).

[0075] DOSEdark(t) - DOSEdark(t - 1)>Expst … Formula (5)

[0076] In this determination, if the differential value is not equal to or greater than the threshold, the process proceeds to step S701. If the differential value is equal to or greater than the threshold, the process proceeds to step S707.

[0077] Here, the value of Expst is set to an arbitrary value. For example, it may be determined based on the standard deviation of the irradiation dose DOSEdark, or it may be determined as an absolute value based on the irradiation conditions of the radiation that can be irradiated. Also, in the present embodiment, the differential value is calculated using the irradiation dose DOSEdark, but the differential value may also be replaced with a signal value that changes based on the radiation. For example, it may be calculated using the signal value Sd of the detection pixel 104, or it may be a crosstalk component caused by radiation exposure that can multiply the signal value Os of the correction pixel 107.

[0078] When step S706 is YES, the signal processing unit 170 transitions to step S707. In step S707, the signal processing unit 170 determines the time at the sampling time (t) as the radiation start point.

[0079] Next, in step S708, the signal processing unit 170 determines the range to be used for the correction value. Here, the correction value is denoted as Doffset in order to clearly distinguish it from the correction values Od and Oc described above. The correction value Doffset will be described with reference to FIG. 8.

[0080] FIG. 8 extracts the integrated irradiation dose in the time from time t3 to t8 in FIG. 6. Note that the vertical axis is extracted in more detail than FIG. 6. In FIG. 8, the integrated irradiation dose before the radiation is irradiated is almost 0, but strictly speaking, due to the time sampling time difference between the signal values Sc, Oc and the correction values Sd, Od in equations (1) and (2), it may not be 0. In the present embodiment, the difference between the integrated irradiation dose and the zero point is called Doffset. Doffset may be caused by factors such as the temperature drift component of the detection pixel 104 and the correction pixel 107, and it is difficult to make it exactly 0. Therefore, as one method for reducing the temperature drift component, it is possible to make the time difference between the signal values Sc, Oc and the correction values Sd, Od as short as possible.

[0081] Therefore, the correction value Doffset determines the range (correction period) to be used for the correction value Doffset based on the radiation start point determined in step S707 so that no radiation is being irradiated and it is as close as possible to the start of radiation irradiation. In this embodiment, it is assumed that the signal values until immediately before the start of radiation irradiation are used, and the signal values during the correction period from the start of reading in step S704 until immediately before the start of radiation irradiation are used. The correction period is the period before the differential value in step S706 becomes equal to or greater than the threshold value.

[0082] When the range of the irradiation dose DOSEdark to be used for the correction value Doffset is determined in step S708, step S709 is then executed.

[0083] In step S709, the signal processing unit 170 calculates the correction value Doffset in order to correct the error from the zero value of the integrated irradiation dose. Specifically, the signal processing unit 170 calculates the correction value Doffset by dividing the total value of the irradiation dose DOSEdark stored in the storage unit 172 in step S704 during the correction period by the number of samplings. Here, the correction period is the period from the start of reading the signal until immediately before the radiation start point. The above correction value Doffset is expressed by the following formula (6).

[0084]

Equation

[0085] Also, the above method for calculating the correction value Doffset is an example, and for example, it may be the result of the moving average value at time t since the start of storage in step S704. Also, it may be calculated from the values for a predetermined number of samplings closest to the start of radiation irradiation based on the predetermined number of samplings to be used for the correction value. In this case, the correction value Doffset is as shown in the following formula (7) using the predetermined number of samplings N.

[0086]

Equation

[0087] Here, the irradiation dose DOSEdark is the irradiation dose DOSE when no radiation is irradiated, and is calculated by Equation (1) or (2). The signal processing unit 170 calculates a correction value Doffset based on the signals of the detection pixel 104 and the correction pixel 107 during the above correction period and the irradiation dose DOSEdark corresponding thereto.

[0088] Next, in step S710, the signal processing unit 170 calculates the irradiation dose DOSE based on the signals of the detection pixel 104 and the correction pixel 107 by Equation (1) or (2). Then, the signal processing unit 170 calculates the corrected integrated irradiation dose using the correction value Doffset in step S709. The offset amount considered by the correction value Doffset may always be included in the irradiation dose DOSE. Therefore, when adding to the integrated irradiation dose before one sampling, it is necessary to subtract the correction value Doffset. For this reason, as one example, the signal processing unit 170 performs the calculation of the integrated irradiation dose (t) of the following Equation (8) at the timing of updating the integrated irradiation dose.

[0089] Integrated irradiation dose (t) = Integrated irradiation dose (t - 1) + DOSE (t) - Doffset... Equation (8)

[0090] However, it is desirable that the first integrated irradiation dose at the start of radiation irradiation is 0.

[0091] Here, in this step, if the error from 0 included in the irradiation dose DOSE can be removed, the method is not limited to the above. For example, the threshold value may be changed using the correction value Doffset with respect to the threshold value of the end request signal in step S711 described later.

[0092] As described above, the signal processing unit 170 calculates the integrated radiation dose based on the radiation dose DOSE based on the signals of the detection pixel 104 and the correction pixel 107, and the correction value Doffset based on the signals of the detection pixel 104 and the correction pixel 107 during the correction period. Specifically, the signal processing unit 170 calculates the integrated radiation dose by subtracting the correction value Doffset from the integrated value of the radiation dose DOSE as shown in Equation (8). In step S708 described above, the signal processing unit 170 determines the above correction period based on the differential value of the signal based on the signal of the detection pixel 104 in step S705.

[0093] Note that in FIG. 8, the correction value Doffset is described as the deviation amount from the 0 value of the integrated dose when no radiation is irradiated, but it is not limited to this. The correction value may be calculated as the output (dark offset amount) when no radiation is irradiated. In that case, the signal processing unit 170 may calculate the integrated radiation dose by subtracting the correction value from the outputs of the detection pixel 104 and the correction pixel 107 acquired at the latest timing when radiation is irradiated.

[0094] Next, in step S711, the signal processing unit 170 determines whether or not the corrected integrated radiation dose is equal to or greater than the determination threshold value of the end request signal. If it is less than the determination threshold value, the process proceeds to step S701, and the control unit 180 reads the signal again. If it is equal to or greater than the determination threshold value, the process proceeds to step S712.

[0095] In step S712, the control unit 180 functions as a transmission unit, transmits an end request signal for radiation irradiation, and performs processing after time t7.

[0096] (Second Embodiment) In the second embodiment, a method for determining the signal values used for determining the correction values Od and Oc in the control unit 180 will be described.

[0097] First, as described above, the control unit 180 performs a read operation a predetermined number of times, one or more times, to determine a correction value. The signal processing unit 170 determines a correction value Od based on the signals read from the detection pixels 104 by the read operation a predetermined number of times, and a correction value Oc based on the signals read from the correction pixels 107 by the read operation a predetermined number of times. When the predetermined number is plural, the signal processing unit 170 uses the average value of the plurality of read signals as the correction value Od, but the signal value used for the correction value is desirably a stable signal value and immediately before the radiation irradiation.

[0098] This is because, as in the case of the correction pixel signal in FIG. 6, as the signal read starts, the temperature of the pixels and peripheral elements fluctuates, and the output value may change. This is one factor. For this reason, it is desirable to use the timing when the fluctuation of the output value is stable as the acquisition start point of the correction values Od and Oc. The method for determining the acquisition start point of the positive values Od and Oc will be described with reference to FIG. 9.

[0099] FIG. 9 is a flowchart for determining the acquisition start point of the correction values Od and Oc.

[0100] After the read operation is first started, in the second read, the process proceeds to step S901.

[0101] In step S901, the control unit 180 reads the signals of the detection pixels 104 and the correction pixels 107.

[0102] Next, in step S902, the signal processing unit 170 stores the signal values of the detection pixels 104 and the correction pixels 107 read into the storage unit 172.

[0103] Next, in step S903, the signal processing unit 170 calculates the differential value between the signal value of the detection pixel 104 in the current sampling read in step S902 and the signal value of the detection pixel 104 in the previous sampling. Specifically, when the read timing is t, the signal processing unit 170 calculates the differential value by detection pixel signal (t) - detection pixel signal (t - 1). In this embodiment, the differential value is calculated with respect to the result of one sampling before, but the method is not limited to this as long as it is calculated by differentiation. For example, the differential value with respect to the signal several predetermined samplings before may be calculated. Also, when the variation amount of the sampled signal is large and the calculated value is not stable, it is desirable to calculate the average value of the signal for each predetermined number of samplings and calculate the differential value with respect to the average value. Further, a moving average may be calculated at a predetermined sampling interval and the differential value may be calculated with respect to the moving average.

[0104] Next, in step S904, the signal processing unit 170 determines whether the differential value is less than or equal to a predetermined threshold. Specifically, it determines that the differential value is within the predetermined threshold.

[0105] This differential value may be further calculated for comparison with the threshold. For example, it may be a moving average of a predetermined number of samplings of the differential value. Also, other statistical values may be used instead of the average value. The threshold may be determined based on, for example, the standard deviation in the stable state when radiation has not been irradiated in advance. Also, the determination process may be made based on the fact that the differential value has fallen within the threshold for a continuous predetermined number of samplings.

[0106] If the differential value is less than or equal to the predetermined threshold in step S904, the process proceeds to step S905, and if the differential value is not less than or equal to the predetermined threshold, the process proceeds to step S901.

[0107] In step S905, the signal processing unit 170 determines this sampling point as the start point of signal acquisition (the start point of the correction period) for determining the correction signals Od and Oc. If the differential value becomes equal to or less than the threshold value, it means that the irradiation dose DOSEdark has stabilized. Therefore, during the correction period, a stabilized irradiation dose DOSEdark can be acquired. As a result, a highly accurate correction value Doffset can be calculated.

[0108] Next, a method for determining the acquisition end point of the correction values Od and Oc will be described with reference to FIG. 10.

[0109] FIG. 10 is a flowchart for determining the acquisition end point of the correction values Od and Oc. The radiation imaging apparatus 100 performs the processes of steps S701, S702, S704 to S707. The descriptions of the processes of steps S701, S702, S704 to S707 are omitted because they are the same as the processes in FIG. 7.

[0110] After the radiation irradiation start point is determined in step S707, the process proceeds to step S1008. In step S1008, the signal processing unit 170 determines the signal range of the correction values Od and Os as the correction period. Specifically, the signal processing unit 170 determines the signal value one or more samplings before the sampling at which the radiation irradiation start point was calculated as the end point of the correction period. Here, the end point of the correction period used for calculating the correction values Od and Os may be any timing of the signal value one or more samplings before the sampling at which the radiation irradiation start point was calculated. For example, it may be the timing of the signal value a predetermined number of samplings before.

[0111] Next, in step S1009, the signal processing unit 170 calculates and determines the correction values Od and Os based on the determined correction period.

[0112] The signal processing unit 170 stores the correction values Od and Oc determined in this way in the storage unit 172 so that they can be used in subsequent processes.

[0113] Here, the determination of the start point of the correction period in step S905 and the determination of the end point of the correction period in step S1008 may each be calculated using the average value or the moving average. It is desirable that the number of samples for calculating each average satisfies (determination of the end point of the correction period) > (determination of the start point of the correction period).

[0114] As described above, the correction period in step S1008 is the period from when the differential value in step S904 becomes equal to or less than the threshold value until before the differential value in step S706 becomes equal to or greater than the threshold value. The correction value Od is a value based on the signals of the detection pixels 104 obtained at predetermined timings within the correction period. The correction value Oc is a value based on the signals of the correction pixels 107 obtained at predetermined timings within the correction period.

[0115] As described above, according to the present embodiment, the signal processing unit 170 calculates the differential value based on the signals read from the detection pixels 104 and the correction pixels 107, and determines the acquisition timing of the correction value Doffset for correcting the integrated irradiation dose based on the differential value. Thereby, the signal processing unit 170 can accurately acquire the correction value Doffset.

[0116] The correction value Doffset in FIG. 8 changes due to factors such as the temperature drift component of the detection pixels 104 and the correction pixels 107. Therefore, it is important that the signal processing unit 170 determines an appropriate correction period in step S708 and determines the real-time correction value Doffset during the correction period in steps S905 and S709.

[0117] The correction value Doffset is calculated based on the integrated value of the irradiation dose DOSEdark during the correction period, as shown in Equation (6) or (7). Here, the irradiation dose DOSEdark is the irradiation dose DOSE when no radiation is irradiated, and is calculated based on the signal value Sd of the detection pixel 104, the signal value Sc of the correction pixel 107, and the correction values Od and Oc, as shown in Equation (1) or (2).

[0118] The signal value Sd of the detection pixel 104 and the signal value Sc of the correction pixel 107, as shown in FIG. 6, vary greatly with the start of signal reading due to the temperature fluctuations of the pixel and peripheral elements. Since the irradiation dose DOSEdark at the timing when the fluctuations of the signal values Sd and Sc are large is uncertain, it is preferably not used for calculating the correction value Doffset.

[0119] Therefore, in step S905, the signal processing unit 170 determines the timing when the differential value in step S904 becomes equal to or less than the threshold value as the start point of the correction period. When the differential value becomes equal to or less than the threshold value, it means that the irradiation dose DOSEdark has stabilized. Therefore, a stable irradiation dose DOSEdark can be obtained during the correction period. As a result, a high-precision correction value Doffset can be calculated.

[0120] In step S1008, the signal processing unit 170 determines the end point of the correction period based on the timing when the differential value in step S706 becomes equal to or greater than the threshold value. The end point of the correction period is the timing immediately before the radiation irradiation. As a result, since the correction value Doffset can use the irradiation dose DOSEdark immediately before the radiation irradiation, it becomes possible to calculate a high-precision correction value Doffset.

[0121] In step S709 of FIG. 7, the signal processing unit 170 can determine a high-precision correction value Doffset based on the integral value of the irradiation dose DOSEdark in an appropriate correction period, as shown in Equation (6) or (7).

[0122] In step S710, the signal processing unit 170 can calculate a high-precision integrated irradiation amount by using the high-precision correction value Doffset.

[0123] (Other Embodiments) The present disclosure can also be implemented by supplying a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be implemented by a circuit (for example, ASIC) that realizes one or more functions.

[0124] Note that the above-described embodiments are merely specific examples for implementing the present disclosure, and the technical scope of the present disclosure is not limitedly interpreted by these. That is, the present disclosure can be implemented in various forms without departing from its technical idea or its main features.

[0125] The disclosure of the present embodiment includes the following configurations and methods. (Configuration 1) A detection pixel that generates a signal based on radiation, A signal processing unit that calculates an integrated radiation dose based on the radiation dose based on the signal of the detection pixel and a correction value based on the signal of the detection pixel during a correction period. The signal processing unit determines the correction period based on a differential value of a signal based on the signal of the detection pixel, and is a radiation imaging apparatus. (Configuration 2) The differential value is a difference between signals based on signals of the detection pixel acquired at different timings, and is the radiation imaging apparatus according to Configuration 1. (Configuration 3) The differential value is a difference between moving averages of signals based on signals of the detection pixel acquired at different timings, and is the radiation imaging apparatus according to Configuration 1. (Configuration 4) The correction period is a period before the differential value becomes equal to or greater than a first threshold value, and is the radiation imaging apparatus according to any one of Configurations 1 to 3. (Configuration 5) Further having a correction pixel with lower sensitivity to radiation than the detection pixel, The signal processing unit, Calculating the correction value based on the signals of the detection pixels and the correction pixels during the correction period, The radiation imaging apparatus according to any one of Configurations 1 to 4, characterized in that the irradiation dose is calculated based on the signals of the detection pixels and the correction pixels. (Configuration 6) The radiation imaging apparatus according to any one of Configurations 1 to 5, characterized in that the signal processing unit calculates the integrated irradiation dose by subtracting the correction value from the integrated value of the irradiation dose. (Configuration 7) The radiation imaging apparatus according to Configuration 5, characterized in that the signal processing unit calculates the integrated irradiation dose by subtracting the correction value from the outputs of the detection pixels and the correction pixels when radiation is being irradiated. (Configuration 8) The radiation imaging apparatus according to any one of Configurations 1 to 7, further comprising a transmission unit that transmits a signal requesting the end of radiation irradiation when the integrated irradiation dose is equal to or greater than a second threshold value. (Configuration 9) The radiation imaging apparatus according to Configuration 5, characterized in that the signal processing unit calculates the irradiation dose based on a first value based on the signals of the detection pixels acquired at a timing of a predetermined number of times, a second value based on the signals of the correction pixels acquired at a timing of a predetermined number of times, the signal of the detection pixels acquired at the most recent timing, and the signal of the correction pixels acquired at the most recent timing. (Configuration 10) The radiation imaging apparatus according to Configuration 9, characterized in that the signal processing unit calculates the correction value based on the irradiation dose during the correction period. (Configuration 11) The radiation imaging apparatus according to Configuration 9 or 10, characterized in that the differential value is a differential value based on the irradiation dose. (Configuration 12) The radiation imaging apparatus according to Configuration 11, characterized in that the differential value is a differential value of the irradiation dose. (Configuration 13) The radiation imaging apparatus according to Configuration 11, wherein the differential value is a difference in the moving average of the irradiation dose. (Configuration 14) The radiation imaging apparatus according to Configuration 11, wherein the correction period is a period from when the differential value based on the signal of the detection pixel becomes equal to or less than a third threshold value until the differential value based on the irradiation dose becomes equal to or greater than a first threshold value. (Configuration 15) The first value is a value based on the signal of the detection pixel obtained at a timing of a predetermined number of times during a period from when the differential value based on the signal of the detection pixel becomes equal to or less than a third threshold value until the differential value based on the irradiation dose becomes equal to or greater than a first threshold value. The radiation imaging apparatus according to Configuration 11, wherein the second value is a value based on the signal of the correction pixel obtained at a timing of a predetermined number of times during a period from when the differential value based on the signal of the detection pixel becomes equal to or less than a third threshold value until the differential value based on the irradiation dose becomes equal to or greater than a first threshold value. (Configuration 16) The radiation imaging apparatus according to Configuration 5, wherein the conversion element of the correction pixel is shielded from light. (Configuration 17) Further comprising a plurality of imaging pixels that generate signals based on radiation. The radiation imaging apparatus according to Configuration 5, wherein the signal processing unit generates a radiation image based on the signals of the plurality of imaging pixels. (Configuration 18) The radiation imaging apparatus according to any one of Configurations 1 to 17. A radiation source that irradiates radiation. A radiation imaging system, characterized by comprising the same. (Method 1) A control method for a radiation imaging apparatus having a detection pixel that generates a signal based on radiation, the method comprising: determining a correction period based on a differential value of a signal based on the signal of the detection pixel; calculating an integrated irradiation dose based on the irradiation dose based on the signal of the detection pixel and a correction value based on the signal of the detection pixel during the correction period. A method for controlling a radiation imaging apparatus, characterized by comprising

Explanation of symbols

[0126] 100 Radiation imaging apparatus, 101 Imaging pixel, 102 Conversion element, 103 Switching element, 104 Detection pixel, 105 Conversion element, 106 Switching element, 107 Correction pixel, 108 Conversion element, 109 Switching element, 110 Drive line, 111 Detection drive line, 120 Signal line, 130 Bias line, 140 Power supply circuit, 150 Drive circuit, 160 Readout circuit, 161 Amplification unit, 162 Multiplexer, 163 AD converter, 170 Signal processing unit, 180 Control unit

Claims

1. A detection pixel that generates a signal based on radiation, A signal processing unit that calculates an integrated radiation dose based on the radiation dose based on the signal of the detection pixel and a correction value based on the signal of the detection pixel during a correction period, The signal processing unit determines the correction period based on a differential value of a signal based on the signal of the detection pixel, and the radiation imaging apparatus is characterized in that.

2. The radiation imaging apparatus according to claim 1, wherein the differential value is a difference between signals based on signals of the detection pixel acquired at different timings.

3. The radiation imaging apparatus according to claim 1, wherein the differential value is a difference between moving averages of signals based on signals of the detection pixel acquired at different timings.

4. The radiation imaging apparatus according to claim 1, wherein the correction period is a period before the differential value becomes equal to or greater than a first threshold value.

5. Further comprising a correction pixel having a lower sensitivity to radiation than the detection pixel, The signal processing unit, Calculates the correction value based on the signal of the detection pixel and the signal of the correction pixel during the correction period, The radiation imaging apparatus according to claim 1, wherein the radiation dose is calculated based on the signal of the detection pixel and the signal of the correction pixel.

6. The radiation imaging apparatus according to claim 1, wherein the signal processing unit calculates the integrated radiation dose by subtracting the correction value from the integrated value of the radiation dose.

7. The radiation imaging apparatus according to claim 5, wherein the signal processing unit calculates the integrated radiation dose by subtracting the correction value from the outputs of the detection pixel and the correction pixel when radiation is being irradiated.

8. The radiation imaging apparatus according to claim 1, further comprising a transmission unit that transmits a radiation irradiation end request signal when the integrated radiation dose is equal to or greater than a second threshold value.

9. The signal processing unit is based on a first value based on the signal of the detection pixel acquired at a timing of a predetermined number of times, a second value based on the signal of the correction pixel acquired at a timing of a predetermined number of times, the signal of the detection pixel acquired at the most recent timing, and the signal of the correction pixel acquired at the most recent timing. The radiation imaging apparatus according to claim 5, wherein the radiation dose is calculated.

10. The radiation imaging apparatus according to claim 9, wherein the signal processing unit calculates the correction value based on the radiation dose during the correction period.

11. The radiation imaging apparatus according to claim 9, wherein the differential value is a differential value based on the radiation dose.

12. The radiation imaging apparatus according to claim 11, wherein the differential value is a differential value of the radiation dose.

13. The radiation imaging apparatus according to claim 11, wherein the differential value is a difference between moving averages of the radiation dose.

14. The radiation imaging apparatus according to claim 11, wherein the correction period is a period from when a differential value based on the signal of the detection pixel becomes equal to or less than a third threshold value until a differential value based on the radiation dose becomes equal to or greater than a first threshold value.

15. The first value is a value based on the signal of the detection pixel obtained at a timing of a predetermined number of times during a period from when a differential value based on the signal of the detection pixel becomes equal to or less than a third threshold value until a differential value based on the radiation dose becomes equal to or greater than a first threshold value. The radiation imaging apparatus according to claim 11, wherein the second value is a value based on the signal of the correction pixel obtained at a timing of a predetermined number of times during a period from when a differential value based on the signal of the detection pixel becomes equal to or less than a third threshold value until a differential value based on the radiation dose becomes equal to or greater than a first threshold value.

16. The radiation imaging apparatus according to claim 5, wherein the conversion element of the correction pixel is shielded from light.

17. The radiation imaging apparatus further includes a plurality of imaging pixels that generate signals based on radiation. The radiation imaging apparatus according to claim 5, wherein the signal processing unit generates a radiation image based on the signals of the plurality of imaging pixels.

18. A radiation imaging system, comprising: the radiation imaging apparatus according to any one of claims 1 to 17; and a radiation source that irradiates radiation. The radiation imaging system is characterized by having the above components.

19. A control method for a radiation imaging apparatus having detection pixels that generate signals based on radiation, the method comprising: determining a correction period based on a differential value of a signal based on the signal of the detection pixel; and calculating an integrated radiation dose based on the radiation dose based on the signal of the detection pixel and a correction value based on the signal of the detection pixel during the correction period. The control method for a radiation imaging apparatus is characterized by having the above steps.

Images