Radiation imaging device and radiation imaging system

Abstract

We provide a radiography system that enables high frame rate, low afterimage, and high-resolution imaging. [Solution] A radiation imaging apparatus comprising a processing unit that acquires pixel signals from pixels driven by a drive unit and generates image data, wherein the drive unit performs a first selection scan in which it sequentially selects m rows of row wiring, which are a part of a plurality of row wirings, at intervals of a first predetermined number of rows for each m row, and a second selection scan in which it sequentially selects n rows of row wiring, which are greater than m, at intervals of a second predetermined number of rows for each n row, and the processing unit corrects the radiation image data based on the pixel signals acquired in the first selection scan with offset image data based on the pixel signals acquired in the second selection scan to generate corrected radiation image data, wherein the first predetermined number of rows in the first selection scan and the second predetermined number of rows in the second selection scan are different from each other.

Description

Technical Field

[0001] The present invention relates to a radiation imaging apparatus and a radiation imaging system that acquire the intensity distribution of radiation transmitted through a subject as an image.

Background Art

[0002] In recent years, as an imaging device used for medical image diagnosis by X-rays and non-destructive inspection, a radiation imaging device using a flat panel detector (hereinafter abbreviated as FPD) formed of a semiconductor material has been put into practical use.

[0003] This FPD is composed of a photodiode mainly made of amorphous silicon and a switching element (TFT) arranged on an insulating substrate such as a glass substrate. Radiation such as X-rays transmitted through a subject such as a patient is converted into a charge signal by the FPD, and the charge signal is subjected to analog-digital conversion, and a transmission image of the subject can be acquired as a digital image.

[0004] In addition to still image shooting, radiation imaging using an FPD can also perform moving image shooting in which images are read out at high speed. In moving image shooting, it is required to read out images at high speed, achieve a high frame rate, and reduce afterimages.

[0005] Further, regardless of the presence or absence of radiation, an offset component is generated by the dark current flowing through the photodiode and the afterimage due to the previous radiation irradiation in the FPD. Therefore, offset correction is performed to reduce the dark current and the afterimage.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] One method of offset correction involves reading an offset image before radiation exposure and subtracting it from the image taken during radiation exposure. While this method allows for a higher frame rate due to the pre-acquisition of the offset image, it cannot correct for afterimages.

[0008] Another method involves alternately acquiring radiation images with radiation exposure and offset images without radiation exposure, and then subtracting the offset images from the radiation images. In this method, the offset images are acquired after radiation exposure and then subtracted, so afterimage correction is possible. However, it requires acquiring two images—the radiation image and the offset image—to obtain a single frame, which limits the frame rate.

[0009] Furthermore, the method disclosed in Patent Document 1 achieves high frame rates and afterimage correction by acquiring offset images by binning multiple rows. However, when offset images are acquired by binning and radiation images are acquired by reading one row at a time as in the conventional method, the difference in storage time between radiation image acquisition and offset image acquisition increases as the rows progress. This difference in storage time results in a noise distribution (the lower part has more noise), which degrades image quality.

[0010] Therefore, in view of the above problems, the present invention aims to provide a radiography system capable of high frame rate, low afterimage, and high image quality imaging. [Means for solving the problem]

[0011] In view of the above problems, the present invention provides a radiation imaging apparatus comprising: a plurality of pixels arranged in a matrix; a plurality of row wirings connecting the plurality of pixels row by row; a drive unit capable of switching the row wirings connected to and selected by the plurality of row wirings; and a processing unit that acquires pixel signals from pixels connected to the row wirings selected by the drive unit and generates image data, wherein the drive unit performs a first selection scan in which it simultaneously selects m row wirings from the plurality of row wirings and sequentially selects the plurality of row wirings by switching the simultaneously selected m row wirings; and a second selection scan in which it simultaneously selects n row wirings greater than m and sequentially selects the plurality of row wirings by switching the simultaneously selected n row wirings; the processing unit generates corrected radiation image data by correcting the radiation image data based on the pixel signals acquired in the first selection scan with offset image data based on the pixel signals acquired in the second selection operation; and the switching of the selected row wirings in the first selection scan and the switching of the selected row wirings in the second selection scan are different from each other. [Effects of the Invention]

[0012] The present invention provides a radiographic imaging system capable of high frame rate, low afterimage, and high image quality imaging. [Brief explanation of the drawing]

[0013] [Figure 1] A diagram illustrating an example configuration of a radiation imaging system according to an embodiment of the present invention. [Figure 2] A diagram illustrating an example configuration of a radiation imaging device according to an embodiment of the present invention. [Figure 3] A diagram illustrating an example of the cross-sectional structure of a pixel according to an embodiment of the present invention. [Figure 4] A diagram illustrating an example of operation of a radiation imaging system according to an embodiment of the present invention. [Figure 5] A diagram illustrating an example of operation of a radiation imaging system according to an embodiment of the present invention. [Figure 6] A diagram illustrating the pixel rearrangement of a radiation imaging system according to an embodiment of the present invention. [Figure 7]A diagram for explaining the stretching process of the radiation imaging system according to an embodiment of the present invention. [Figure 8] A diagram for explaining an operation example of the radiation imaging system according to an embodiment of the present invention. [Figure 9] A diagram for explaining an operation example of the radiation imaging system according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and duplicate explanations are omitted.

[0015] <First Embodiment> FIG. 1 shows a configuration example of a radiation imaging system 100 according to the first embodiment of the present invention. The radiation imaging system 100 is configured to electrically image an optical image formed by radiation and obtain an electrical radiation image. The radiation is typically X-rays, but may be α-rays, β-rays, γ-rays, or the like. The radiation imaging system 100 includes, for example, a radiation imaging device 110 and a computer 120 as a processing device. In the preferred form shown in FIG. 1, it further includes a display means 114, an exposure control device 130, and a radiation generation device 140.

[0016] The radiation generation device 140 starts radiation irradiation in accordance with an exposure command (radiation command) from the exposure control device 130. The radiation irradiated from the radiation generation device 140 enters the radiation imaging device 110 through the subject 150. The radiation generation device 140 also stops radiation irradiation in accordance with a stop command from the exposure control device 130.

[0017] The radiation imaging device 110 includes a radiation detection panel 111, a control circuit 112, and an image processing unit 113. The radiation detection panel 111 generates image data corresponding to the radiation incident on the radiation imaging device 110 and transmits it to a computer 120 which is a processing device. The image data is data representing a radiation image and includes corrected radiation image data which will be described later. The control circuit 112 controls the operation of the radiation detection panel 111. For example, based on the image signal obtained from the radiation detection panel 111, the control circuit 112 generates a stop signal for stopping the irradiation of radiation from the radiation generator 140. The stop signal is supplied to the exposure control device 130 via the computer 120. The exposure control device 130 sends a stop command to the radiation generator 140 in response to the stop signal. The control circuit 112 is composed of a dedicated circuit such as a PLD (Programmable Logic Device) like an FPGA (Field Programmable Gate Array). Note that it may also be composed of a dedicated circuit such as an ASIC (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 storage circuit such as a memory. In this case, the function of the control circuit 112 may be realized by the general-purpose processing circuit executing the program stored in the storage circuit.

[0018] The image processing unit 113 stores the pixel signal acquired from the radiation detection panel 111 as radiation image data in a memory, corrects the stored radiation image data using offset image data, and transmits it to the computer 120 as corrected radiation image data. Note that hereinafter, the radiation image data, offset image data, and corrected radiation image data may also be collectively referred to simply as image data.

[0019] The computer 120 includes a control unit that controls the radiation imaging device 110 and the exposure control device 130, a receiving unit that receives image data from the radiation imaging device 110, and a signal processing unit that processes the image data received by the receiving unit. The control unit, receiving unit, and signal processing unit may each be configured by dedicated circuits, similar to the control circuit 112, or by a combination of general-purpose processing circuits and memory circuits. In one example, the exposure control device 130 has an exposure switch, and when the exposure switch is turned on by the user, it sends an exposure command to the radiation generator 140 and a start notification to the computer 120 indicating the start of radiation irradiation. Upon receiving the start notification, the computer 120 responds to the start notification by notifying the control circuit 112 of the radiation imaging device 110 of the start of radiation irradiation.

[0020] In cases where the exposure control device 130 and the computer 120 are not synchronously connected, the radiation detection panel continues its image readout operation and detects the start of radiation exposure from the output value of the image signal.

[0021] Figure 2 shows an example configuration of a radiation detection panel 111. The radiation detection panel 111 comprises, for example, a pixel array 200, a drive circuit 210 which is a drive unit, a readout circuit 220, a buffer circuit 230, and an AD converter 240. 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 201 arranged in a matrix, a plurality of row wirings which are drive lines Vg1 to Vg8, a plurality of column wirings which are signal lines Sig1 to Sig8, and a bias line Bs. In Figure 2, for illustrative purposes, the pixel array 200 is composed of 8 rows × 8 columns of pixels 201. However, in reality, more pixels 201 may be arranged. In one example, the radiation detection panel 111 has dimensions of 17 inches and has approximately 3000 rows × approximately 3000 columns of pixels 201. Each pixel 201 is composed of a conversion element and a switching element.

[0022] The pixel array 200 includes multiple conversion elements C11 to C88 and multiple switch elements S11 to S88. In the following description, the conversion elements C11 to C88 are collectively referred to as conversion element C. The description of conversion element C applies to each of the conversion elements C11 to C88. Similarly, the switch elements S11 to S88, drive lines Vg1 to Vg8, and signal lines Sig1 to Sig8 are collectively referred to as switch element S, drive line Vg, and signal line Sig, respectively. As shown in Figure 2, the drive lines Vg connect the image 201 row by row, and the signal lines Sig connect the image 201 row by row. Each row of the pixel array 200 is referred to as row 1 to row 8 from the top of the drawing, and each column of the pixel array 200 is referred to as column 1 to column 8 from the left of the drawing. Each pixel 201 is composed of a combination of one conversion element C and one switch element S. For example, pixel 201, located in the first row and second column, is formed by a combination of a conversion element C12 and a switching element S12.

[0023] In each pixel 201, a conversion element C converts incident radiation into a charge signal, and a switch element S is connected between the conversion element C and the signal line Sig corresponding to the conversion element C. For example, switch elements S11, S21, S31, S41, S51, S61, S71, S81 are connected between multiple conversion elements C11, C21, C31, C41, C51, C61, C71, C81 and the signal line Sig1. When the switch element S is turned on, conduction occurs between the conversion element C and the signal line Sig, and the charge signal obtained by the conversion element C (for example, the charge accumulated in the conversion element C) is transferred to the signal line Sig. In the following, the charge signal may also be referred to as the pixel signal. 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 electric 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 201.

[0024] 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 of which 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.

[0025] The control terminal of the switch element S for pixel 201 in the first row is connected to the drive line Vg1. The control terminal of the switch element S for pixel 201 in the second row is connected to the drive line Vg2. The same applies to rows 3 through 8.

[0026] The drive circuit 210 supplies drive signals to the control terminals of the switch elements S of each pixel 201 via the drive line Vg, according to the control signals supplied from the control circuit 112. The control signals include an ON signal (high-level voltage in the following description) for turning on the switch elements S and an OFF signal (low-level voltage in the following description) for turning off the switch elements S. The drive circuit 210 includes, for example, a shift register, which performs a shift operation according to the control signals (for example, a clock signal) supplied from the control circuit 112. This allows the drive circuit 210 to sequentially select the drive lines Vg.

[0027] The readout circuit 220 amplifies and reads the charge signal obtained by the conversion element C and appearing on the signal line Sig. 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 eight signal lines Sig, so the readout circuit 220 includes eight amplifier circuits 221. Each column amplifier section CA 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 integrating 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.

[0028] 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.

[0029] 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 image data, is transmitted to the processing unit, the computer 120.

[0030] Figure 3 schematically shows an example of the cross-sectional structure of a single pixel 201. The pixel 201 is formed on an insulating substrate 301 such as a glass substrate. The pixel 201 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 makes up 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 makes up 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 makes up the switch element S. The conductive layer 306 constitutes wiring patterns connected to the two main terminals (source and drain) of the transistor that makes up the switch element S. A portion of the conductive layer 306 constitutes a signal line Sig, while another portion constitutes a wiring pattern for connecting the switching element S to the conversion element C.

[0031] Pixel 201 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 201 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.

[0032] Alternatively, the conversion element C may be configured as a direct-type conversion element that directly converts incident radiation into an electric charge signal. 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.

[0033] In the example shown in Figure 3, in the orthographic projection (plan view) of the plane on which the pixel array 200 is formed, each of the multiple signal lines Sig overlaps with a portion of the conversion element C. While this configuration has the advantage of a large area of ​​the conversion element C for each pixel 201, it has the disadvantage of increasing the capacitive coupling between the signal line Sig and the conversion element C.

[0034] An example of the operation of the radiation imaging system 100 will be described with reference to Figure 4. The operation of the radiation imaging system 100 is controlled by the computer 120. The operation of the radiation imaging device 110 is controlled by the control circuit 112 under the control of the computer 120. The operation shown in Figure 4 is initiated, for example, by a user of the radiation imaging system 100.

[0035] The "Operation" section in Figure 4 shows the operation of the radiation imaging system 100. The operation of the radiation imaging system 100 includes the acquisition of offset image data and the acquisition of radiation image data. The acquisition of offset image data is a series of operations performed while waiting for the start of radiation irradiation and a series of operations performed after the acquisition of radiation image data to acquire offset image data. In the following, radiation image data, offset image data, and the corrected radiation image data (image data obtained by correcting radiation image data with offset image data) may also be simply referred to as radiation image, offset image, and corrected radiation image, respectively.

[0036] Figure 4 shows an example of acquiring an offset image using two-row binning, but the number of rows to be binned is not limited to this. The number of rows skipped during radiation image acquisition should be changed according to the number of binning steps. For example, in the case of three-row binning, it will look like Figure 5. Thus, binning means selecting two or more drive lines Vg at once and reading out the pixel signals of the two or more drive lines Vg selected at once all at once.

[0037] Radiation image acquisition is a series of operations for acquiring a radiation image. An offset image is an image formed by charge signals obtained from each pixel 201 when the radiation imaging device 110 is not irradiated with radiation. In Figure 4, "Radiation" indicates whether or not radiation is being irradiated. Low level indicates that no radiation is being irradiated, and high level indicates that radiation is being irradiated. In Figure 4, "Frame" indicates the number of frames in the video recording. The image readout from the first radiation irradiation corresponds to the first frame, and the image readout from the second radiation irradiation corresponds to the second frame.

[0038] In 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. A switch element S connected to a drive line Vg to which a low-level (off signal) drive signal is supplied is off, and a switch element S connected to a drive line Vg to which a high-level (on signal) drive signal is supplied is on. A drive line Vg is selected when a high-level (on) drive signal is supplied.

[0039] The acquisition of radiation images and offset images includes an accumulation period and a readout period. During the accumulation period, the drive circuit 210 supplies an off signal to each drive line Vg1 to Vg8 for a predetermined time. As a result, charge corresponding to the radiation incident on each conversion element C is accumulated in the conversion element C, and at the same time, the dark current flowing through each conversion element C is also accumulated.

[0040] Next, during the readout period, the control circuit 112 reads out the charge signals stored in each conversion element C. The following explanation will mainly focus on the charge read out through signal line Sig1, but the same applies to the charges read out through signal lines Sig2 to Sig8.

[0041] First, the drive circuit 210 supplies an ON signal only to the drive line Vg1. This turns on the switch element S11, creating a conductive state between the conversion element C11 and the signal line Sig1, so the charge signal obtained by the conversion element C11 is read out to the signal line Sig1.

[0042] Next, the drive circuit 210 supplies an ON signal only to the drive line Vg2. This turns on the switch element S21, creating a conductive state between the conversion element C21 and the signal line Sig1, so the charge signal obtained by the conversion element C21 is read out to the signal line Sig1. This act of supplying an ON signal to the drive line Vg is called selective operation, and the operation of switching (scanning) the drive line Vg to which the ON signal is supplied is called selective scanning.

[0043] By repeating this operation along the drive lines Vg1 to Vg8, the charge signals read from each conversion element are output to the signal lines Sig1 to Sig8, and the image processing unit 113 generates image data. Furthermore, by repeating this operation, it becomes possible to generate moving image data.

[0044] Next, we will describe the features of the first embodiment.

[0045] First, we will explain the operation of acquiring radiographic images and offset images.

[0046] The operation for acquiring radiographic images involves reading out the data in the order of drive lines Vg1, Vg3, Vg5, Vg7, Vg2, Vg4, Vg6, and Vg8 (skipping one row), a process known as interlaced scanning. In other words, it selects drive lines (row wiring) one row at a time, and then selects them sequentially with a one-row gap between selections. On the other hand, the operation for acquiring offset images involves supplying ON signals to drive lines Vg two rows at a time, a process known as binning scanning. By supplying ON signals to drive lines Vg two rows at a time, the charge signal for two rows flows through the signal line Sig, effectively doubling the charge signal. Furthermore, because drive lines Vg are turned on two rows at a time, the readout period can be halved. This allows for a shorter frame duration and a higher frame rate. This operation of reading out multiple rows at once is called binning. In this example, the drive lines (row wiring) are selected two rows at a time, and then selected sequentially with a zero-row gap between selections.

[0047] As a basic operation, as shown in Figure 4, the system waits for the start of radiation irradiation while repeatedly alternating between acquiring radiation images and acquiring offset images. Once radiation irradiation begins, radiation images are acquired, followed by the acquisition of offset images. Note that the acquisition of offset images may be performed before radiation irradiation.

[0048] Here, we will explain the pixel rearrangement of radiographic images, the stretching of offset images, and the binning process.

[0049] The radiation images acquired using the above radiation image acquisition operation are read out skipping rows, so simply arranging them from top to bottom will not produce a correct image. Therefore, as shown in Figure 6, it is necessary to rearrange the pixels to the correct positions. Also, the offset images acquired using the above offset image acquisition operation are acquired by binning scanning, so they undergo stretching. Figure 7 shows the method of stretching. Because ON signals are supplied to drive lines Vg1 and Vg2 simultaneously, the charge signals accumulated in conversion elements C11 and C21 flow simultaneously to signal line Sig1 and are captured as the charge signal of one pixel. On the other hand, in radiation image acquisition, ON signals are supplied to drive lines Vg1 and Vg2 one row at a time, so the charge signals accumulated in conversion elements C11 and C21 are captured as signals of different pixels. Therefore, as shown in Figure 6, pixels C11 and C12 are stretched in the row direction to create an image the same size as the radiation image. Additionally, since ON signals are supplied to both drive lines Vg1 and Vg2 simultaneously, the charge signal is doubled. Therefore, in the binning return process, the pixel value is divided by 2 to halve it.

[0050] Next, the image processing unit performs accumulation time correction for each row. Accumulation time correction involves multiplying the offset image by a coefficient K. The afterimage component is proportional to the period from when the signal supplied to the drive line Vg is switched from an ON signal to an OFF signal until the next drive line Vg is switched from an ON signal to an OFF signal (the sum of the accumulation period and the readout period), and this period is called the accumulation period. For example, for the first row, the ratio of the accumulation time A for acquiring the radiation image to the accumulation time B for acquiring the offset image (A / B) is multiplied by the radiation image (radiation image including afterimage). For the second row, the ratio of the accumulation time C for acquiring the radiation image to the accumulation time D for acquiring the offset image (C / D) is multiplied by the radiation image (radiation image including afterimage). Here, A / B is a smaller value than C / D. By multiplying the offset image by this coefficient, which is the accumulation time ratio, the afterimage component contained in the radiation image can be accurately estimated. Therefore, a corrected radiation image can be generated by subtracting the image obtained by multiplying the offset image by the coefficient K from the radiation image. Corrected radiographic images have the afterimage component removed from the original radiographic image, resulting in a radiographic image with low afterimage (offset-corrected image).

[0051] However, while the coefficient K can improve the accuracy of afterimage correction, a large value increases noise. Therefore, by acquiring the radiographic image by reading every other row, odd-numbered rows will be image data rows with a small coefficient K and low noise (A / B), and even-numbered rows will be image data rows with a large coefficient K (C / D) and high noise. Thus, rows with high noise and rows with low noise can be alternated within the screen. As a result, the noise distribution is spread throughout, making the effect of increased noise less noticeable and improving image quality.

[0052] In this way, by acquiring radiation images by reading every other row and acquiring offset images using binning, it is possible to alternate rows with two different coefficients K, thereby achieving high frame rates, low afterimages, and high image quality.

[0053] Furthermore, by using the first and second pre-offset images, it is possible to extract more accurate afterimage components and generate radiation images with lower afterimages. This will be explained using Figure 9.

[0054] The operation of acquiring the first pre-offset image is the same as the operation of acquiring the radiation image, and the operation of acquiring the second pre-offset image is the same as the operation of acquiring the offset image. Before radiation irradiation, the first pre-offset image acquisition and the second pre-offset image acquisition are performed alternately multiple times, and the multiple acquired pre-offset images are averaged and stored in the image processing unit 113 as the first pre-offset image and the second pre-offset image. By averaging, the effect of noise is reduced. In Figure 9, the first pre-offset image acquisition and the second pre-offset image acquisition are performed alternately twice, and averaging is performed twice, but the effect of noise can be further reduced by performing averaging more times.

[0055] By calculating the difference between the radiation image and the first pre-offset image, it is possible to accurately extract the radiation image containing both the signal charge component and the afterimage component. Furthermore, by calculating the difference between the offset image and the second pre-offset image, it is possible to more accurately extract the afterimage image containing only the afterimage component. Therefore, the accuracy of afterimage correction can be improved.

[0056] In the above embodiment, the operation of sequentially selecting radiation image data with a one-row interval between each row and sequentially selecting offset image data with a zero-row interval between every two rows was described, but the present invention is not limited to this. For example, in shooting situations where high resolution is not required, the radiation image data may be sequentially selected with a two-row interval between every two rows, and the offset image data may be acquired with a zero-row interval between every three rows. In this case, shooting at a higher frame rate becomes possible. Thus, an embodiment in which radiation image data is selected with a predetermined number of rows between every m rows and offset image data is acquired by sequentially selecting n rows of row wiring (larger than m) with a second predetermined number of rows between every n rows is also within the scope of the present invention. In addition, as described above, when selecting with a predetermined number of rows between each row, it is also possible that the predetermined number of rows is zero.

[0057] <Second Embodiment> Next, a second embodiment will be described using Figure 8. In this embodiment, during the operation of acquiring radiation images, in the first frame, reading starts from drive line Vg1 and skips one line, while in the second frame, reading starts from drive line Vg2 and skips one line. This operation is then repeated. In this embodiment, the starting line for reading is alternated from frame to frame. As a result, in the first frame, odd-numbered lines have a small coefficient K (A / B) and even-numbered lines have a large coefficient K (C / D), while in the second frame, odd-numbered lines have a large coefficient K (C / D) and even-numbered lines have a small coefficient K (A / B). As a result, the effect of noise can be made less visible, and the image quality can be improved.

[0058] Furthermore, the coefficient K used for accumulation time correction may be calculated as follows. By calculating it as follows, the coefficient K can be reduced to one type.

[0059] For example, the accumulation time ratio may be calculated based on multiple frames. Specifically, the value obtained by adding the accumulation times of radiation image acquisition for the first and second frames and dividing by 2 ((A+C) / 2) and the value obtained by adding the accumulation times of offset image acquisition for the first and second frames and dividing by 2 ((B+D) / 2) may be used. Alternatively, the accumulation time ratio may be calculated based on the accumulation times of adjacent drive lines Vg. For example, the value obtained by adding the accumulation times of radiation image acquisition for Vg1 and Vg2 and dividing by 2 ((A+C) / 2) and the value obtained by adding the accumulation times of offset image acquisition for Vg1 and Vg2 and dividing by 2 ((B+D) / 2) may be used.

[0060] Alternatively, image generation may be performed using multiple frames.

[0061] For example, an image may be generated based on a composite radiation image created by adding the radiation images of the first and second frames, and a composite offset image created by adding the offset images of the first and second frames. In this case, pixel rearrangement, stretching, binning correction, and accumulation time correction are performed to generate the image after offset correction. The coefficient K used in accumulation time correction is (A+C) / (B+D), and the coefficient K can be reduced to one type.

[0062] 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.

[0063] The disclosures herein include the following radiographic imaging devices and radiographic imaging systems.

[0064] (Item 1) A radiation imaging apparatus comprising: a plurality of pixels arranged in a matrix; a drive unit for driving the plurality of pixels; a plurality of row wirings connecting the plurality of pixels and the drive unit; and a processing unit that acquires pixel signals from the pixels driven by the drive unit and generates image data, Each of the plurality of row wirings connects a portion of the plurality of pixels to the drive unit row by row; the drive unit performs a first selection scan in which it sequentially selects m rows of row wiring, which are a portion of the plurality of row wirings, at intervals of a first predetermined number of rows for each m row; and a second selection scan in which it sequentially selects n rows of row wiring, which are greater than m, at intervals of a second predetermined number of rows for each n row; the processing unit corrects the radiation image data based on the pixel signals acquired in the first selection scan with offset image data based on the pixel signals acquired in the second selection scan to generate corrected radiation image data; and the first predetermined number of rows in the first selection scan and the second predetermined number of rows in the second selection scan are different from each other.

[0065] (Item 2) The radiation imaging apparatus according to item 1, characterized in that the first selected scan is an interlaced scan.

[0066] (Item 3) The radiation imaging apparatus according to item 1 or 2, characterized in that the drive unit alternately performs the first selection scan and the second selection scan multiple times.

[0067] (Item 4) The radiation imaging apparatus according to item 3, characterized in that the processing unit can generate corrected radiation image data multiple times and generate motion image data consisting of multiple frames.

[0068] (Item 5) The radiation imaging apparatus according to item 4, characterized in that the drive unit changes the starting row for selecting row wiring of m rows in the first selection scan for each frame.

[0069] (Item 6) The radiation imaging apparatus according to any one of items 1 to 4, characterized in that the processing unit applies a correction to the pixel signal acquired in the second selection operation to generate the offset image data, in accordance with the time taken from the selection of the first row wiring in the first selection scan by the drive unit to the selection of the first row wiring in the second selection scan.

[0070] (Item 7) The radiation imaging apparatus according to item 4 or 5, characterized in that the processing unit calculates an accumulation time ratio which is the ratio of the time taken from the selection of the first row wiring in the second selection scan in the first frame by the drive unit to the selection of the first row wiring in the first selection scan in the second frame, and the time taken from the selection of the first row wiring in the first selection scan in the second frame to the selection of the first row wiring in the second selection scan in the second frame, and generates the offset image data by multiplying the pixel signal acquired in the second selection operation in the second frame by the accumulation time ratio.

[0071] (Item 8) The radiation imaging apparatus according to item 7, characterized in that the processing unit calculates the accumulation time ratio based on multiple frames.

[0072] (Item 9) The radiation imaging apparatus according to item 7, characterized in that the processing unit calculates the accumulation time ratio based on a plurality of adjacent row wirings.

[0073] (Item 10) A radiation imaging system comprising a radiation imaging device described in any one of items 1 to 9, and a processing device for processing the corrected radiation image data acquired from the radiation imaging device. [Explanation of symbols]

[0074] 100 Radiation Imaging Systems 110 Radiation imaging device 113 Image Processing Unit 201 pixels 210 Drive Circuit

Claims

1. Multiple pixels arranged in a matrix, A drive unit that drives the plurality of pixels, Multiple row wirings connecting the multiple pixels and the drive unit, A processing unit that acquires pixel signals from pixels driven by the aforementioned drive unit and generates image data, A radiation imaging device equipped with, Each of the aforementioned multiple row wirings connects some of the multiple pixels to the drive unit row by row. The drive unit performs a first selection scan in which it sequentially selects m rows of wiring, which are a part of the plurality of row wirings, with a first predetermined number of rows spacing between each m row, and a second selection scan in which it sequentially selects n rows of wiring, which are greater than m, with a second predetermined number of rows spacing between each n row. The processing unit corrects the radiation image data based on the pixel signals acquired in the first selection scan with the offset image data based on the pixel signals acquired in the second selection scan to generate corrected radiation image data. A radiation imaging apparatus characterized in that the first predetermined number of rows in the first selection scan and the second predetermined number of rows in the second selection scan are different from each other.

2. The radiation imaging apparatus according to claim 1, characterized in that the first selected scan is an interlaced scan.

3. The radiation imaging apparatus according to claim 1, characterized in that the drive unit alternately performs the first selection scan and the second selection scan multiple times.

4. The radiation imaging apparatus according to claim 3, characterized in that the processing unit can generate corrected radiation image data multiple times and generate motion image data consisting of multiple frames.

5. The radiation imaging apparatus according to claim 4, characterized in that the drive unit changes the starting row for selecting row wiring of m rows in the first selection scan for each frame.

6. The radiation imaging apparatus according to claim 4, characterized in that the processing unit applies a correction to the pixel signal acquired in the second selection operation to generate the offset image data in accordance with the time taken from the selection of the first row wiring in the first selection scan by the drive unit to the selection of the first row wiring in the second selection scan.

7. The processing unit calculates an accumulation time ratio, which is the ratio of the time taken from the selection of the first row wiring in the second selection scan in the first frame by the drive unit to the selection of the first row wiring in the first selection scan in the second frame, to the time taken from the selection of the first row wiring in the first selection scan in the second frame to the selection of the first row wiring in the second selection scan in the second frame, and generates the offset image data by multiplying the pixel signal acquired in the second selection operation in the second frame by the accumulation time ratio, as described in claim 4.

8. The radiation imaging apparatus according to claim 7, characterized in that the processing unit calculates the accumulation time ratio based on multiple frames.

9. The radiation imaging apparatus according to claim 7, characterized in that the processing unit calculates the accumulation time ratio based on a plurality of adjacent row wirings.

10. A radiation imaging system comprising a radiation imaging device according to claim 1, and a processing device for processing the corrected radiation image data acquired from the radiation imaging device.

Images