Radiation imaging device and radiation imaging system

Abstract

It accurately reduces crosstalk in radiographic images. [Solution] A radiation imaging device comprising a plurality of pixels, a drive unit, and a readout unit, wherein during radiation irradiation, a first operation is performed in which drive signals are sequentially supplied to the readout unit to generate a first signal, and a second operation is performed in which, following the first operation, the readout unit generates a second signal without supplying a drive signal, and the first signal is corrected with the second signal to generate a radiation image data signal.

Description

Technical Field

[0001] The present invention relates to a radiation imaging device and a radiation imaging system.

Background Art

[0002] Radiation imaging devices have been put into practical use as imaging devices used for medical image diagnosis and non-destructive inspection. When a part of a radiation imaging device is strongly irradiated with radiation, a radiation image generated by the radiation imaging device includes crosstalk caused by signal leakage or the like. Depending on the radiation imaging device, a process for reducing such crosstalk may be performed. Patent Document 1 describes a technique for repeatedly changing a sensor for detecting radiation between a conductive state and a non-conductive state and subtracting a signal acquired in the non-conductive state from a signal acquired in the conductive state in order to reduce crosstalk. Patent Document 2 describes a technique for suppressing artifacts generated due to the influence of leakage charge by correcting a signal when a detection element is turned on with a signal when the switch of the detection element is turned off when there is a missing part in a captured image.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology described in Patent Document 1 had room for improvement in terms of frame rate and power consumption. The technology described in Patent Document 2 made it difficult to correct for continuous radiation image acquisition over time. The present invention aims to provide a technology for accurately reducing crosstalk in continuous radiation image acquisition while suppressing a decrease in frame rate and an increase in power consumption. [Means for solving the problem]

[0005] The present invention, which solves the above problems, comprises a plurality of pixels arranged in a matrix, each having a conversion element that converts radiation or light into electric charge and a switching element that outputs the charge generated by the conversion element or a signal based on said charge, A drive unit that outputs a drive signal to drive the switch element, A plurality of drive lines that supply the drive signal output by the drive unit to the switch element, A readout unit that processes the signal output from the aforementioned pixel, A plurality of signal lines are provided corresponding to the row of pixels and supply the signals generated by the pixels to the readout unit, A control unit that controls the operation of the drive unit and the read unit, An image generation unit that receives a signal output from the reading unit and generates a radiation image data signal. A radiation imaging device equipped with, The control unit, during radiation irradiation, performs a first operation in which the drive unit sequentially supplies drive signals to the plurality of drive lines and generates a first signal in the readout unit, and a second operation in which, following the first operation, the drive unit does not supply drive signals to the plurality of drive lines and generates a second signal in the readout unit. The image generation unit is characterized by generating a radiation image data signal by correcting the first signal with the second signal. [Effects of the Invention]

[0006] The above embodiment makes it possible to accurately reduce crosstalk while suppressing a decrease in frame rate and an increase in power consumption. [Brief explanation of the drawing]

[0007] [Figure 1] A block diagram illustrating an example configuration of a radiation imaging system in some embodiments. [Figure 2] An equivalent circuit diagram illustrating an example configuration of a radiation detection panel in some embodiments. [Figure 3] A schematic diagram illustrating an example of the pixel structure in some embodiments. [Figure 4] A diagram illustrating an example of operation of a radiation imaging system in some embodiments. [Figure 5] A diagram illustrating the crosstalk generation mechanism in some embodiments. [Figure 6] A diagram illustrating images in which crosstalk occurs in some embodiments. [Figure 7] A diagram illustrating the shooting flow of some embodiments. [Figure 8] A schematic diagram illustrating an example of the pixel structure in some embodiments. [Figure 9] A diagram illustrating images in which crosstalk occurs in some embodiments. [Modes for carrying out the invention]

[0008] [First Embodiment] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0009] Figure 1 shows an example configuration of a radiation imaging system 100 according to one embodiment. The radiation imaging system 100 is configured to generate an electrical radiation image by electrically capturing an optical image formed by radiation. The radiation is typically X-rays, but may also be alpha rays, beta rays, gamma rays, etc. The radiation imaging system 100 includes, for example, a radiation imaging device 110, a control device computer 120, a display 114, an exposure control device 130, and a radiation generator 140.

[0010] The radiation generator 140 begins irradiating with radiation 160 in accordance with the exposure command (radiation command) from the exposure control device 130. The radiation 160 emitted from the radiation generator 140 passes through the subject 150 and enters the radiation imaging device 110. The radiation generator 140 also stops irradiating with radiation 160 in accordance with the stop command from the exposure control device 130.

[0011] The radiation imaging device 110 includes a radiation detection panel 111, a control circuit 112, and an image generation circuit 113, which is an image generation unit. The image generation circuit 113 acquires a signal that will become image data from a readout circuit (described later) and generates a radiation image data signal after applying corrections (described later). The radiation detection panel 111 generates a radiation image corresponding to the radiation 160 incident on the radiation imaging device 110 and transmits it to the computer 120. The control circuit 112 controls the operation of the radiation detection panel 111.

[0012] The control circuit 112 may be composed of a dedicated circuit such as a PLD (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). FPGA stands for Field Programmable Gate Array, PLD for Programmable Logic Device, and ASIC for Application Specific Integrated Circuit. Alternatively, the control circuit 112 may be composed of a combination of a general-purpose processing circuit, such as a processor, and a memory circuit, such as memory. In this case, the functions of the control circuit 112 may be realized by the general-purpose processing circuit executing a program stored in the memory circuit.

[0013] The image generation circuit 113 stores the signal supplied from the radiation detection panel 111 in a memory, and generates a radiation image based on this signal. Details of the method for generating the radiation image will be described later. The image generation circuit 113 transmits the generated radiation image to the computer 120.

[0014] The computer 120 includes a control unit that controls the radiation imaging apparatus 110 and the exposure control apparatus 130, a reception unit that receives a radiation image from the radiation imaging apparatus 110, and a signal processing unit that processes the radiation image obtained by the radiation imaging apparatus 110. Each of the control unit, the reception unit, and the signal processing unit may be configured by a dedicated circuit, similarly to the control circuit 112, or may be configured by a combination of a general-purpose processing circuit and a storage circuit. In one example, the exposure control apparatus 130 has an exposure switch. When the exposure switch is turned on by the user, the exposure control apparatus 130 sends an exposure command to the radiation generation apparatus 140 and sends a start notification indicating the start of radiation irradiation to the computer 120. The computer 120 that has received the start notification notifies the control circuit 112 of the radiation imaging apparatus 110 of the start of radiation irradiation in response to the start notification. When the exposure control apparatus 130 and the computer 120 are not synchronously connected, the radiation detection panel 111 may detect the start of irradiation of the radiation 160 based on the pixel signal.

[0015] FIG. 2 shows a configuration example of the radiation detection panel 111. The radiation detection panel 111 includes, for example, a pixel array 200, a drive circuit 210 as a drive unit, a readout circuit 220 as a readout unit, a buffer circuit 230, and an analog-digital (AD) converter 240. The radiation detection panel 111 is divided into upper and lower parts, and the pixel array 200, the drive circuit 210, the readout circuit 220, the buffer circuit 230, and the analog-digital (AD) converter 240 are symmetrically arranged in the upper and lower parts respectively. The drive circuit 210 and the readout circuit 220 function as peripheral circuits of the pixel array 200. The pixel array 200 is composed of, for example, a plurality of pixels P, a plurality of drive lines Vg1 to Vgm, a plurality of signal lines Sig1 to Sign in the upper stage, a plurality of signal lines Sig’1 to Sig’n in the lower stage, and a bias line Bs. The drive lines Vg1 to Vgm and the signal lines Sig1 to Sign, Sig’1 to Sig’n are collectively referred to as drive lines Vg and signal lines Sig respectively. As shown in FIG. 2, the signal line Sig is divided into upper and lower parts. The plurality of pixels P are arranged in a matrix so as to form a plurality of pixel rows and a plurality of pixel columns. A pixel row is a set of a plurality of pixels arranged horizontally in FIG. 2. A pixel column is a set of a plurality of pixels arranged vertically in FIG. 2. As shown in FIG. 2, the pixel column is divided into upper and lower parts. In one example, the radiation detection panel 111 has a size of 9 inches, and the pixel array 200 has a total of 1000 rows including 1000 pixel columns and 500 pixel rows in the upper and lower parts respectively.

[0016] Each pixel row of the pixel array 200 is called the first row to the m-th row (m is an integer from 1 to 1000) in order from the top. Also, each pixel column of the pixel array 200 is called the first column to the n-th column (n is an integer from 1 to 1000) in order from the left side of FIG. 2. Each pixel P is composed of a combination of one conversion element C and one switch element S. The pixel P located at the i-th row and the j-th column in the pixel array 200 is represented as pixel P(i,j). The conversion element C and the switch element S included in the pixel P(i,j) are represented as conversion element C(i,j) and switch element S(i,j) respectively. For example, pixel P(1, 2) represents the pixel P located at the first row and the second column.

[0017] The conversion element C generates and stores an electric charge corresponding to the radiation incident on the pixel P. The conversion element C can store not only the charge corresponding to the radiation, but also the charge generated by the dark current. The generation and storage of charge by the conversion element C of the pixel P is described as the generation and storage of charge by the pixel P.

[0018] The switch element S is connected between the conversion element C and the signal line Sig corresponding to this conversion element C. For example, switch elements S(1,1) to S(m,1) are connected between multiple conversion elements C(1,1) to C(m,1) and the signal line Sig1, respectively. When the switch element S is turned on, the connection between the conversion element C and the signal line Sig becomes conductive, and the charge obtained by the conversion element C (for example, the charge accumulated in the conversion element C) is transferred to the signal line Sig. The conversion element C may be, for example, an MIS-type photodiode made mainly of amorphous silicon and placed on an insulating substrate such as a glass substrate. Alternatively, the conversion element C may be a PIN-type photodiode. The conversion element C may be configured as a direct type that directly converts radiation into charge, or as an indirect type that converts radiation into light and then detects this light. In the indirect type, the scintillator may be shared by multiple pixels P.

[0019] The switching element S is composed of a transistor, such as a thin-film transistor (TFT) having a control terminal (gate) and two main terminals (source and drain). The conversion element C has two main electrodes. One main electrode of the conversion element C is connected to one of the two main terminals of the switching element S, and the other main electrode of the conversion element is connected to a bias power supply Vs via a common bias line Bs. The bias power supply Vs generates a bias voltage.

[0020] The control terminal of the switch element S for pixel P in the first row is connected to the drive line Vg1. The control terminal of the switch element S for pixel P in the second row is connected to the drive line Vg2. The same applies to rows 3 through m.

[0021] The drive circuit 210 supplies a drive signal to the control terminal of the switch element S of each pixel P via the drive line Vg, according to the drive signal supplied from the control circuit 112. The drive signal includes an ON signal (high-level voltage in the following description) for turning on the switch element S and an OFF signal (low-level voltage in the following description) for turning off the switch element S. For convenience of explanation, in the following, the state in which the OFF signal is supplied may be described as the state in which the drive signal is not supplied. In this case, the state in which the ON signal is supplied may be described as the state in which the drive signal is supplied. The drive circuit 210 includes, for example, a shift register, which performs a shift operation according to a control signal (for example, a clock signal) supplied from the control circuit 112.

[0022] Supplying an ON signal (i.e., a high-level drive signal) to a pixel P is described as selecting pixel P or supplying a drive signal to pixel P. In other words, the drive signal is a signal used to select one of several pixels P. The same drive signal is supplied to multiple pixels in the same pixel row. Selecting multiple pixels in a single pixel row is described as selecting this pixel row.

[0023] The readout circuit 220 amplifies and reads the signal that appears on the signal line Sig by selecting pixel P. This signal corresponds to the charge stored in the conversion element C. Reading out the signal corresponding to the charge stored in the conversion element C of pixel P is expressed as reading out the signal corresponding to the charge stored in pixel P.

[0024] The readout circuit 220 includes one amplifier circuit 221 for each signal line Sig. In the example in Figure 2, the pixel array 200 has n signal lines Sig both above and below, so the readout circuit 220 includes n amplifier circuits 221 both above and below. The amplifier circuit 221 includes, for example, an integral amplifier 222, a variable amplifier 223, a switch element 224, a capacitor 225, and a buffer circuit 226. The switch element 224 and the capacitor 225 constitute a sample-and-hold circuit. The integral amplifier 222 includes, for example, an operational amplifier, an integral capacitor connected in parallel between the inverting input terminal and the output terminal of the operational amplifier, and a reset switch. A reference voltage is supplied from a reference power supply Vref to the non-inverting input terminal of the operational amplifier. When the reset switch is turned on in response to the control signal RC (reset pulse) supplied from the control circuit 112, the integral capacitor is reset and the potential of the signal line Sig is reset to the reference potential. The variable amplifier 223 amplifies the signal from the integral amplifier 222 at a set amplification factor. The sample-and-hold circuit samples and holds the signal from the variable amplifier 223. The on / off state of the switch element 224 that constitutes the sample-and-hold circuit is controlled by the control signal SH supplied from the control circuit 112. The buffer circuit 226 buffers (impedance converts) the signal from the sample-and-hold circuit and outputs it. Note that in the following explanation, the pixel P connected to the upper readout circuit in Figure 2 may be described as some of the pixels. Also, the pixel P connected to the lower readout circuit may be described as other pixels besides some of the pixels. Furthermore, in the following explanation, the upper readout circuit may be described as the first readout circuit (first readout section). Also, the lower readout circuit may be described as the second readout circuit (second readout section).

[0025] The readout circuit 220 also includes a multiplexer 227 that selects and outputs signals from multiple amplifier circuits 221 in a predetermined order. The multiplexer 227 includes, for example, a shift register, which performs a shift operation according to a control signal (e.g., a clock signal) supplied from the control circuit 112. This shift operation selects one signal from the multiple amplifier circuits 221.

[0026] The buffer circuit 230 buffers (impedance converts) the signal output from the multiplexer 227. The AD converter 240 converts the analog signal output from the buffer circuit 230 into a digital signal. The output of the AD converter 240, i.e., the pixel signal (sometimes referred to as the image data signal in the following description), is processed by the image generation circuit 113, which is the image generation unit, and then transmitted to the computer 120.

[0027] Figure 3 schematically shows an example of the cross-sectional structure of a single pixel P. The pixel P is formed on an insulating substrate 301 such as a glass substrate. The pixel P has a conductive layer 302, an insulating layer 303, a semiconductor layer 304, an impurity semiconductor layer 305, and a conductive layer 306 on the insulating substrate 301. The conductive layer 302 constitutes the gate of the transistor (e.g., TFT) that constitutes the switch element S. The insulating layer 303 is arranged to cover the conductive layer 302. The semiconductor layer 304 is arranged on the portion of the conductive layer 302 that constitutes the gate, via the insulating layer 303. The impurity semiconductor layer 305 is arranged on the semiconductor layer 304 so as to constitute the two main terminals (source and drain) of the transistor that constitutes the switch element S. The conductive layer 306 constitutes wiring patterns connected to the two main terminals (source and drain) of the transistor that constitutes the switch element S. Part of the conductive layer 306 constitutes the signal line Sig, and the other part constitutes a wiring pattern for connecting the switch element S to the conversion element C.

[0028] Pixel P further has an interlayer insulating film 307 covering the insulating layer 303 and the conductive layer 306. The interlayer insulating film 307 is provided with a contact plug 308 for connecting to the conductive layer 306 (switch element S). On top of the interlayer insulating film 307, pixel P further has a conductive layer 309, an insulating layer 310, a semiconductor layer 311, an impurity semiconductor layer 312, a conductive layer 313, a protective layer 314, an adhesive layer 315, and a scintillator 316 in this order. These layers constitute an indirect type conversion element C. The conductive layer 309 and the conductive layer 313 constitute the lower electrode and the upper electrode of the photoelectric conversion element that constitutes the conversion element C, respectively. The conductive layer 313 is made of, for example, a transparent material. The conductive layer 309, the insulating layer 310, the semiconductor layer 311, the impurity semiconductor layer 312, and the conductive layer 313 constitute an MIS type sensor as a photoelectric conversion element. The impurity semiconductor layer 312 is formed, for example, from an n-type impurity semiconductor layer. The scintillator 316 is composed of, for example, a gadolinium-based material or a CsI (cesium iodide) material, and converts radiation into light.

[0029] Alternatively, the conversion element C may be configured as a direct-type conversion element that directly converts incident radiation into electric charge. Examples of direct-type conversion elements C include those primarily made of amorphous selenium, gallium arsenide, gallium phosphorus, lead iodide, mercury iodide, CdTe, CdZnTe, etc. The conversion element C is not limited to the MIS type; for example, it may also be a pn type or PIN type photodiode.

[0030] In the example shown in Figure 3, in an orthographic projection (plan view) onto the surface of the insulating substrate 301 on which the pixel array 200 is formed, each of the multiple signal lines Sig overlaps with a portion of the conversion element C. This configuration is advantageous because it allows for a larger area of ​​the conversion element C for each pixel P.

[0031] An example of the operation of the radiation imaging system 100 will be described with reference to Figure 4. The upper part of Figure 4 shows the timing chart, and the lower part of Figure 4 shows the signal processing flow. The operation shown in Figure 4 is initiated, for example, by a user of the radiation imaging system 100. The operation of the radiation imaging system 100 is controlled by the computer 120. The operation of the radiation imaging device 110 is performed by the control circuit 112 under the control of the computer 120. Specifically, the control circuit 112 performs the operation shown in Figure 4 by controlling the drive circuit 210 and the readout circuit 220. In the following description, when the control circuit 112 causes a specific operation to be performed by controlling the drive circuit 210 or the readout circuit 220, it may simply be said that the control circuit 112 performs a specific operation.

[0032] In the timing chart of Figure 4, "Vg1" to "Vg8" indicate the levels of the drive signals supplied from the drive circuit 210 to each drive line Vg1 to Vg8. The example in Figure 4 describes a case where the pixel array 200 contains eight pixel rows, but the number of pixel rows is not limited to this.

[0033] In the timing chart of Figure 4, "Period" represents the period during which a specific operation is performed. Imaging by the radiation imaging device 110 includes an accumulation period during which an accumulation operation is performed and a readout period during which a readout operation is performed. During the accumulation period, the control circuit 112 does not select any of the multiple pixels P included in the pixel array 200. Specifically, the drive circuit 210 maintains a state in which an off signal is supplied to each of the drive lines Vg1 to Vg8 (a state in which no drive signal is supplied). As a result, the charge generated in each conversion element C is accumulated in the conversion element C.

[0034] During the readout period, the control circuit 112 selects each of the multiple pixels P included in the pixel array 200 and reads a signal from the selected pixel P. Specifically, the drive circuit 210 supplies ON signals to drive lines Vg1 to Vg8 one by one in sequence. First, the drive circuit 210 supplies an ON signal only to drive line Vg1. This turns on the switch element S(1,j) (j=1,...,n), creating a conductive state between the conversion element C(1,j) and the signal line Sigj, so the charge accumulated in the conversion element C(1,j) is read out to the signal line Sigj. Next, the drive circuit 210 supplies an ON signal only to drive line Vg2. This turns on the switch element S(2,j), creating a conductive state between the conversion element C(2,j) and the signal line Sigj, so the charge accumulated in the conversion element C(2,j) is read out to the signal line Sigj. The drive circuit 210 repeats this operation up to the drive line Vg8, so that the charge based on the charge accumulated in the conversion element C is read out by the read circuit 220 through the signal line Sigj. In other words, the drive unit sequentially supplies drive signals to multiple drive lines Vg1 to Vg8, causing the read unit to read signals corresponding to the charge from the pixels, thereby generating image data signals. In the following description, performing a read operation on multiple pixels P means performing a read operation on each of the multiple pixels P.

[0035] The control circuit 112 performs motion imaging (i.e., imaging of multiple radiation images). The control circuit 112 alternately performs accumulation and readout operations. As shown in Figure 4, it performs accumulation operations and then reads out signals based on the charges accumulated in multiple pixels P.

[0036] The image generation circuit 113 generates a radiation image data signal based on the image data signals read from each of the multiple pixels P included in the pixel array 200. The radiation image X is represented as an m x n matrix, and the signal read from pixel P(i,j) becomes the (i,j) component of this matrix.

[0037] Referring to Figure 5, the crosstalk occurring in the radiation detection panel 111 will be explained. In the first embodiment, the case in which the radiation emitted from the radiation generator 140 is continuous in time will be described. When the radiation emitted from the radiation generator 140 is continuous in time, radiation is emitted to all pixels even during readout, and the charge of the conversion element C changes. Then, a charge-based signal flows through the signal line due to the coupling capacitance. Figure 5 shows an example of the j-th column pixel when the switch in row 1000 is on. In Figure 5, the signal in row 1000 is superimposed as crosstalk by the charge-based signals of the conversion elements C in rows 501 to 999, to which the signal line Sigj is connected. Similarly, in the other rows, the signals of the unselected rows (rows to which the drive signal (on signal) is not supplied) to which the signal line Sigj is connected are superimposed on the signals corresponding to the charge of the selected rows (rows to which the drive signal (on signal) is supplied).

[0038] Refer to Figure 6 to explain how crosstalk appears in images. Figure 6(a) is a conceptual diagram of reading the signal from one side of the radiation detection panel 111 when a high dose is irradiated to an arbitrary location without a subject in place. Figure 6(b) is an example of the signal output values ​​in the reading direction of columns (A) and (B) in the image of (a). Figure 6(c) is a conceptual diagram of reading the signal from both the top and bottom directions of the radiation detection panel 111 (when reading with the configuration in Figure 2). Figure 6(d) is an example of the signal output values ​​in the reading direction of columns (C), (D), (E), and (F) in the image of (c). In other words, in Figures 6(b) and 6(d), the horizontal axis plots smaller drive line numbers on the left and larger numbers on the right. When strong radiation hits a specific location on the radiation detection panel 111, the signal in the column hit by the strong radiation will be output as a larger value compared to the signal line column that was not hit by the strong radiation due to crosstalk. Thus, when reading from both the top and bottom, a step is created in the center compared to reading from only one side, and crosstalk becomes more pronounced in the image.

[0039] Referring to Figure 7, the flow of image output with crosstalk correction is explained. In step S101, the imaging conditions such as accumulation time, gain, and number of frames are set. In step S102, irradiation of temporally continuous radiation begins, and in step S103, the control circuit 112 receives a signal to start imaging from the computer 120 and starts imaging under the conditions set in step S101. In step S104, after a specified accumulation time, the drive lines Vg1 to Vgn are driven sequentially and the radiation signals for each row are read out. Note that when reading from both the upper and lower directions (in the configuration of Figure 2), the drive lines Vg'1 to Vg'n are driven sequentially in the same way as the drive lines Vg1 to Vgn. Next, in step S105, with the drive lines Vg not driven, the signal of the signal line Sig is read out for a specified time. Specifically, in the configuration of Figure 2, after driving Vg1 to Vg500, with no drive signal supplied to the drive lines Vg1 to Vg500, the signal of the signal line Sig is read out for a specified time. Similarly, after driving Vg1000~Vg501, the signal from signal line Sig is read out for a specified time while no drive signal is supplied to drive lines Vg1000~Vg501. At this time, the longer the readout time, the more the noise is averaged, but the maximum frame rate cannot be increased accordingly, so it is desirable to set it appropriately based on the time required to read out a pixel row and the storage time set in step S101. For example, in this embodiment, the signal from signal line Sig is read out without supplying a drive signal to the drive lines 30 times (the time it takes to scan 30 drive lines). However, this is not limited to this, and the readout operation can be performed multiple times, or even just once depending on the shooting conditions. Then, in step S106, the correction value for each pixel row is calculated from the average value obtained by averaging the output signals when the drive lines Vg read out in step S105 were not driven (a process of adding up the 30 outputs and averaging them). In steps S107 and S108, the radiation image signal is calculated for each pixel row from the difference between the radiation signal read in step S104 and the correction value for each pixel column calculated in step S106. Specifically, the signal output value of (B) in Figure 6(b) is set to the same level as the signal output value of (A), and the signal output value of (D) in Figure 6(d) is set to the same level as the signal output values ​​of (C, E, F).After the calculation of the radiation image signal is completed for all rows, i.e., for all pixel rows of the radiation detection panel 111, the radiation image is sent to the computer 120 in step S109. In step S110, it is determined whether the number of images set in step S101 has been reached, and if not, steps S103 to S109 are repeated.

[0040] According to this embodiment, since the operation to read out the radiation image signal is performed during continuous radiation irradiation, the image signal contains a crosstalk component. However, by reading the signal from the signal line without supplying a drive signal to the drive line, and using this signal to correct the image signal, it becomes possible to remove the crosstalk component from the image signal and obtain a correct radiation image. Furthermore, as described above, in this embodiment, the image signal for one screen is read out, and the crosstalk correction signal is acquired during the period before reading out the image signal for the next screen, in other words, during the period between screens (frame switching period). Therefore, it is possible to acquire the crosstalk correction value and perform crosstalk correction while suppressing a decrease in the frame rate.

[0041] In this embodiment, the order of signal acquisition for creating a single image was described as acquiring the output signal with the drive line Vg driven first, followed by acquiring the output signal when the drive line Vg is not driven. However, as long as it is a series of operations, it is also acceptable to acquire the output signal without the drive line Vg driven first, and then acquire the output signal with the drive line Vg driven. Furthermore, although the driving direction of the drive line Vg was described as driving from the outside to the inside of the radiation detection panel 111, it may also be driven from the inside to the outside. In addition, as shown in the configuration in Figure 2, if there are two readout circuits (a first readout circuit (first readout section) and a second readout circuit (second readout section)), both readout circuits may be operated simultaneously.

[0042] [Second Embodiment] In the first embodiment, a correction method using a non-driven signal under radiation irradiation was described. In this structure, there is a risk of overcorrection because the reference value of the so-called dark current when no reference radiation is present is unknown. A method of measuring the reference value before radiation irradiation can be considered, but when used continuously for a long period of time, the reference value fluctuates due to the effect of temperature drift, making accurate correction impossible. Therefore, as a method to solve this problem, a technique is described in which a pixel that is not sensitive to radiation, a so-called optical black (OB) pixel, is placed on the radiation detection panel 111, and the reference value is corrected based on the output value of this OB pixel. Note that the optical black (OB) pixel can be constructed by covering the conversion element with a shielding material that shields against radiation or light.

[0043] Referring to Figure 8, the radiation detection panel 111 with OB pixels will be described. The effective pixel area 1111 in the center of the radiation detection panel 111 has the structure shown in Figure 2 above. Several rows, for example, about three rows of OB pixel areas 1112 are provided at the left and right ends of the radiation detection panel 111. The OB pixel area is structured such that it is covered with a metal film over the normal pixels and does not receive light converted by the scintillator 316. Alternatively, the panel may be covered with a structure to prevent radiation from hitting it. In addition, instead of photodiodes for pixels, an equivalent capacitance may be used to prevent the accumulation of charge due to radiation. The field of view of the output image is the effective pixel area, and areas other than the effective pixel area, such as the OB pixel area, are either not driven or driven but do not output, so they can be sensitive to radiation or not. Note that if the output image of the detection panel is rectangular, it will be the effective pixel area.

[0044] Refer to Figure 9 to explain the crosstalk correction of the radiation detection panel 111 with OB pixels. Figure 9(a) shows an image taken when a high dose is irradiated to an arbitrary part of the area without a subject in place. In this image, after reading out the signals of the pixels in the effective pixel area, the Sig readout from the signal lines is continued for half the number of rows of the effective pixel area without driving the drive lines Vg, and this is a schematic diagram of the output image. Figure 9(b) is an example of the signal output values ​​in the normal output area, high dose irradiation area, crosstalk generation area, and OB area area of ​​the output image in Figure 9(a). Here, the normal output area means the part irradiated with a normal dose of radiation. As mentioned above, crosstalk affects all rows of signal lines Sig, so the effect of crosstalk occurs even when the drive lines Vg are not driven. Therefore, the signal output value of the row in the high dose irradiation area is higher than the signal output value of the row in the normal output area. Here, the difference between the signal output value of the TFT-ON crosstalk generation area and the signal output value of the TFT-ON normal output area is defined as the TFT-ON crosstalk amount. Furthermore, the difference between the signal output value of the TFT-OFF crosstalk generation section and the signal output value of the TFT-OFF normal output section is defined as the TFT-OFF crosstalk amount. As shown in Figure 9(b), the TFT-ON crosstalk amount and the TFT-OFF crosstalk amount are approximately the same. On the other hand, the OB region is never affected by radiation irradiation, and the signal output remains constant due only to the amount of dark current caused by the noise component of the electrical circuit. Figure 9(c) shows an example of the signal output value at location (G) in Figure 9(b). Since the OB region is always constant due to the dark current component, the amount of crosstalk due to radiation irradiation for each signal line Sig can be obtained by subtracting this average value from the output value of the effective pixel region. Note that the value obtained by this method is only the increase component due to pure crosstalk.

[0045] This allows for correction of not only crosstalk but also dark current, making it possible to acquire more accurate radiation images compared to Embodiment 1.

[0046] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention.

[0047] Furthermore, the disclosures herein include the following radiation imaging devices and radiation imaging systems.

[0048] (Item 1) A plurality of pixels arranged in a matrix, each having a conversion element that converts radiation or light into electric charge and a switch element that outputs the electric charge generated by the conversion element or a signal based on the electric charge; a drive unit that outputs a drive signal to drive the switch element; a plurality of drive lines that supply the drive signal output by the drive unit to the switch element; a readout unit that processes the signal output from the pixel; a plurality of signal lines provided corresponding to the row of pixels and supplying the signal generated by the pixel to the readout unit; and a control unit that controls the operation of the drive unit and the readout unit. A radiation imaging apparatus comprising: an image generation unit that receives a signal output from the readout unit and generates a radiation image data signal, wherein the control unit causes the drive unit to sequentially supply drive signals to the plurality of drive lines during radiation irradiation, which is a first operation that causes the readout unit to generate a first signal; and, following the first operation, causes the drive unit to generate a second signal to the readout unit without supplying drive signals to the plurality of drive lines, and the image generation unit corrects the first signal with the second signal to generate a radiation image data signal.

[0049] (Item 2) The radiation imaging apparatus according to item 1, characterized in that the control unit causes the drive unit and the readout unit to perform the second operation multiple times to generate multiple second signals, and corrects the first signal using a signal obtained by averaging the multiple second signals.

[0050] (Item 3) The radiation imaging apparatus according to item 1 or 2, wherein the reading unit comprises a first reading unit and a second reading unit, the first reading unit processes signals output from some of the plurality of pixels, and the second reading unit processes signals output from the other pixels of the plurality of pixels.

[0051] (Item 4) The radiation imaging apparatus according to item 3, characterized in that the control unit operates the first readout unit and the second readout unit simultaneously.

[0052] (Item 5) The radiation imaging apparatus according to any one of items 1 to 4, characterized in that the plurality of pixels have a first pixel and a second pixel, and the conversion element provided in the second pixel is covered with a shielding member that shields the radiation or light.

[0053] (Item 6) The radiation imaging apparatus according to item 5, characterized in that the image generation unit corrects the first signal generated by the readout unit processing the signal output from the first pixel in the first operation with the second signal generated by the readout unit processing the signal output from the first pixel in the second operation, and the first signal generated by the readout unit processing the signal output from the second pixel in the first operation or the second signal generated by the readout unit processing the signal output from the second pixel in the second operation to generate the radiation image data signal.

[0054] (Item 7) A radiation imaging system comprising a radiation imaging device described in any one of items 1 to 6, and a control device that acquires radiation image data signals from the radiation imaging device and processes the acquired radiation image data signals. [Explanation of symbols]

[0055] 100 Radiation Imaging Systems 110 Radiation imaging device 112 Control circuits 113 Image generation circuit 200-pixel array 210 Drive Circuit 220 Readout Circuit

Claims

1. A plurality of pixels arranged in a matrix, each having a conversion element that converts radiation or light into electric charge and a switch element that outputs the charge generated by the conversion element or a signal based on said charge, A drive unit that outputs a drive signal to drive the switch element, A plurality of drive lines that supply the drive signal output by the drive unit to the switch element, A readout unit that processes the signal output from the aforementioned pixel, A plurality of signal lines are provided corresponding to the row of pixels and supply the signals generated by the pixels to the readout unit, A control unit that controls the operation of the drive unit and the read unit, An image generation unit that receives a signal output from the reading unit and generates a radiation image data signal. A radiation imaging device equipped with, The control unit, during radiation irradiation, performs a first operation in which the drive unit sequentially supplies drive signals to the plurality of drive lines and generates a first signal in the readout unit, and a second operation in which, following the first operation, the drive unit does not supply drive signals to the plurality of drive lines and generates a second signal in the readout unit. The image generation unit is characterized by generating a radiation image data signal by correcting the first signal with the second signal.

2. The radiation imaging apparatus according to claim 1, characterized in that the control unit causes the drive unit and the readout unit to perform the second operation multiple times to generate a plurality of second signals, and corrects the first signal using a signal obtained by averaging the plurality of second signals.

3. The radiation imaging apparatus according to claim 1, wherein the reading unit comprises a first reading unit and a second reading unit, the first reading unit processes signals output from some of the plurality of pixels, and the second reading unit processes signals output from the other pixels of the plurality of pixels.

4. The radiation imaging apparatus according to claim 3, characterized in that the control unit operates the first readout unit and the second readout unit simultaneously.

5. The radiation imaging apparatus according to claim 1, wherein the plurality of pixels include a first pixel and a second pixel, and the conversion element provided in the second pixel is covered with a shielding member that shields against radiation or light.

6. The radiation imaging apparatus according to claim 5, characterized in that the image generation unit corrects the first signal generated by the readout unit processing the signal output from the first pixel in the first operation with the second signal generated by the readout unit processing the signal output from the first pixel in the second operation, and the first signal generated by the readout unit processing the signal output from the second pixel in the first operation or the second signal generated by the readout unit processing the signal output from the second pixel in the second operation to generate the radiation image data signal.

7. A radiation imaging system comprising a radiation imaging device according to claim 1, and a control device that acquires radiation image data signals from the radiation imaging device and processes the acquired radiation image data signals.

Images