JP2015115868A - Radiation imaging device and radiation imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device or an imaging system which is capable of reducing the time from the start of radiation irradiation to the acquisition of a preview image.SOLUTION: In a radiation imaging device including a pixel array consisting of a plurality of pixels arranged in a matrix form and a control part controlling a reading operation for reading an electrical signal transferred from the pixel array and capturing a radiation image of a subject, the control part performs control so as to perform a first reading operation for reading the electrical signal for confirming the quality of the capturing of the radiation image of the subject from a part of the pixels of the pixel array, during a radiation irradiation period in which the pixel array is irradiated with radiation and a second reading operation for reading the electrical signal for capturing the radiation image of the subject from the pixel array, after the radiation irradiation period.

Description

  The present invention relates to an imaging apparatus, a radiation imaging apparatus, and a system suitable for use in medical diagnosis and industrial nondestructive inspection. In particular, the present invention relates to a radiation imaging apparatus and a radiation imaging system that detect radiation irradiation from a radiation generation apparatus.

  In recent years, radiation imaging apparatuses using a flat panel detector (hereinafter referred to as FPD) formed of a semiconductor material have been put into practical use as imaging apparatuses used for medical image diagnosis and nondestructive inspection using X-rays. Yes. This radiation imaging apparatus using FPD converts digital radiation such as X-rays transmitted through a subject such as a patient into an analog electrical signal by FPD, and converts the analog electrical signal to analog to digital to obtain a digital image signal. It is a device that can shoot.

  FPDs used in this radiation imaging apparatus are roughly classified into direct conversion type and indirect conversion type. The direct conversion type radiation imaging apparatus is an apparatus having an FPD in which a plurality of pixels including a conversion element using a semiconductor material capable of directly converting a radiation such as a-Se into a charge is arranged two-dimensionally. An indirect conversion type radiation imaging apparatus includes a wavelength converter such as a phosphor capable of converting radiation into light, and a photoelectric conversion element using a semiconductor material such as a-Si capable of converting light into electric charge. A device having an FPD in which a plurality of pixels including elements are two-dimensionally arranged.

  For example, in medical image diagnosis, a radiation imaging apparatus having such an FPD is used as a digital imaging apparatus for still image shooting such as general shooting or moving image shooting such as fluoroscopic shooting.

  A preview image is displayed in order to quickly determine whether or not the subject has been correctly photographed at the time of screening for photographing a large number of people using the FPD. By displaying the preview image, the radiologist confirms the position of the subject, confirms that the target part is correctly contained in the image, and if there is no problem, prepares the next person for imaging. By displaying the preview image in this way, it is possible to quickly shoot a large number of people.

  Patent Document 1 discloses that a preview image can be quickly displayed on a console display unit or the like by performing simple image correction processing.

JP 2011-172606 A

  However, in the method of Patent Document 1, since a preview image is displayed, reading is performed a plurality of times for one radiation irradiation, and therefore it takes time to obtain a preview image. Further, in the method of Patent Document 1, since the preview image cannot be displayed unless the radiation irradiation is completed, the time from the start of radiation irradiation to the display of the preview image is delayed by the radiation irradiation time. Therefore, an object of the present invention is to provide a radiation imaging apparatus or a radiation imaging system that can reduce the time from the start of radiation irradiation to obtaining a preview image.

  In order to solve the above-described problems, a radiation imaging apparatus according to the present invention includes a pixel array in which a plurality of pixels that accumulate electrical signals corresponding to radiation transmitted through a subject are arranged in a matrix, and is transferred from the pixel array. And a control unit that controls a readout operation for reading out the electrical signal. In the radiation imaging apparatus that captures a radiographic image of the subject, the control unit confirms whether the radiographic image of the subject is captured. A first readout operation for reading out an electrical signal for reading from a part of pixels of the pixel array during a radiation irradiation period in which the radiation is applied to the pixel array, and an electrical signal for capturing a radiographic image of the subject And a second readout operation for reading out from the pixel array after the radiation irradiation period. It is characterized by.

  By the above means, it is possible to provide a radiation imaging apparatus or radiation imaging system that can reduce the time from the start of radiation irradiation to the acquisition of a preview image.

1 is a conceptual diagram of a radiation imaging system including a conceptual equivalent circuit diagram of a radiation imaging apparatus according to a first embodiment. 1A is a conceptual diagram of a radiation imaging system including a conceptual equivalent circuit diagram of a radiation imaging apparatus according to a first embodiment. FIG. 2B is a conceptual equivalent circuit diagram showing the readout circuit according to the first embodiment. 3 is a flowchart according to the first embodiment. (A) It is a timing chart which concerns on 1st Embodiment. (B) It is a timing chart which concerns on 1st Embodiment. It is a conceptual diagram of the radiation imaging system containing the conceptual equivalent circuit schematic of the radiation imaging device which concerns on 2nd Embodiment. It is a timing chart concerning a 2nd embodiment. It is a conceptual diagram of the radiation imaging system containing the conceptual equivalent circuit schematic of the radiation imaging device which concerns on 3rd Embodiment. 10 is a timing chart according to the third embodiment. It is a radiation imaging system which concerns on 4th Embodiment.

  Hereinafter, embodiments to which the present invention can be suitably applied will be described in detail with reference to the drawings. In the present embodiment, description will be made assuming that electromagnetic waves such as X-rays and γ rays, α rays, and β rays are also included in the radiation.

(First embodiment)
The configuration of the radiation imaging apparatus will be described in detail with reference to FIGS. 1 and 2.

  FIG. 1 is a conceptual diagram of a radiation imaging system including a conceptual equivalent circuit diagram of the radiation imaging apparatus according to the first embodiment of the present invention. The radiation imaging apparatus 100 in FIG. 1 is an apparatus that captures a radiation image of a subject (not shown). Further, the radiation imaging apparatus 100 of FIG. 1 includes a pixel array 101 in which a plurality of pixels that accumulate electrical signals corresponding to radiation transmitted through a subject are arranged in a matrix. In addition, the radiation imaging apparatus 100 includes a drive circuit 102 that drives the pixel array 101 in order to output electrical signals accumulated in the pixel array 101.

  In the present embodiment, the pixel array 101 is configured to have pixels of 8 rows and 8 columns as an example. The electric signal 112 output from the pixel array 101 is read by the corresponding reading circuit 103. The electrical signal 112 read to the readout circuit 103 is subjected to predetermined processing in the readout circuit 103 and is output as a serial electrical signal 113. The serial electric signal 113 is converted into a digital signal 114 by the A / D converter 104.

  The digital signal 114 converted by the A / D converter 104 is output as a digital image signal 115 after signal processing such as offset correction and gain correction by the digital signal processing means 105. The digital signal processing means 105 of this embodiment corresponds to the offset correction means and the image correction means of the present invention. The shading correction unit 106 corrects image shading with respect to a preview image, which will be described later, and generates a corrected digital image signal 210. Note that the shading correction unit 106 of the first embodiment corresponds to the shading correction means of the present invention.

  The power supply unit 107 supplies a reference voltage necessary for the operation of each circuit. The power supply unit 107 supplies the read circuit 103 with first and second reference power supplies Vref1 and Vref2, and supplies the A / D conversion unit 104 with a third reference power supply Vref3. The power supply unit 107 supplies bias power to the drive circuit 102. The power supply unit 107 supplies an on-bias Von for turning on the switch element T in the pixel and an off-bias Voff for turning off the switch element T.

  The control unit 108 supplies a drive control signal 119 to the drive circuit 102 in order to control the drive circuit 102. The drive circuit 102 supplies the drive signal 111 to the pixel array 101 based on the drive control signal 119 and transfers the electrical signal accumulated in a predetermined pixel. The control unit 108 supplies an operation control signal 118 to control the power supply unit 107. The power supply unit 107 controls power supplied to the pixel array 101, the drive circuit 102, the readout circuit 103, and the A / D conversion unit 104 based on the operation control signal 118. Further, the control unit 108 supplies signals 116, 117 and 120 for controlling the reading circuit 103.

  Next, the radiation generator of FIG. 1 will be described. Reference numeral 501 denotes a radiation generation apparatus that emits radiation to a subject, and reference numeral 502 denotes a radiation control apparatus for controlling the radiation generation apparatus. Reference numeral 503 denotes an exposure button for a user (not shown) to emit radiation, reference numeral 504 denotes a communication signal for communication between the radiation imaging apparatus 100 and the radiation control apparatus 502, and reference numeral 505 denotes a radiation beam.

  When the user turns on the exposure button 503, a confirmation signal is sent from the radiation control device 502 to the radiation imaging device 100 via the communication signal 504 as to whether radiation can be emitted. When a permission signal permitting radiation irradiation is output from the radiation imaging apparatus 100, the radiation generation apparatus 501 starts radiation irradiation. The radiation generator 501 stops radiation irradiation after a preset radiation irradiation period.

  FIG. 2 is a conceptual diagram of an imaging system including a conceptual equivalent circuit diagram of the imaging apparatus according to the first embodiment of the present invention. In addition, the same thing as the structure demonstrated using FIG. 1 is provided with the same number, and detailed description is omitted.

  Each pixel 201 in the pixel array 101 includes a conversion element S that converts radiation or light into electric charges, and a switch element T that transfers an electric signal corresponding to the electric charges.

  As the conversion element S for converting radiation or light into electric charge, a photoelectric conversion element such as a PIN photodiode or MIS photodiode, which is disposed on an insulating substrate such as a glass substrate and mainly contains amorphous silicon, is preferable. Used. Moreover, as a conversion element that converts radiation into electric charge, an indirect type including a wavelength conversion body that converts radiation into light in a wavelength band that can be detected by the photoelectric conversion element S on the radiation incident side of the photoelectric conversion element described above. A conversion element or a direct conversion element that directly converts radiation into electric charge is preferably used.

  As the switch element T, a transistor having a control terminal and two main terminals is preferably used. When the photoelectric conversion element is arranged on an insulating substrate, a thin film transistor (TFT) is preferably used. One electrode of the conversion element S is electrically connected to one of the two main terminals of the switch element T, and the other electrode is electrically connected to the sensor bias line Vs.

The control unit 108 controls the drive circuit 102 to transfer the electrical signal stored in a predetermined row in the pixel array 101 to the selected predetermined row. The switch elements of the plurality of pixels 201 in the row direction, for example, T _{11 to} T ₁₈ , have their control terminals electrically connected in common to the drive wiring G ₁ in the first row. Then, a drive signal 111 for controlling the conduction state of the switch element T from the drive circuit 102 is given to each switch element T in a row unit via the drive wiring.

The switching elements of the plurality of pixels 201 in the column direction, for example, T _{11 to} T ₈₁ , have their other main terminals electrically connected to the signal wiring Sig ₁ in the first column. For example, when the switch elements T _{11 to} T ₁₈ are turned on, the electric charge generated in the conversion element S ₁₁ is read as an electric signal via the signal wiring Sig ₁ .

  The control unit 108 causes the electrical signal transferred by the driving circuit 102 to read out the electrical signal by controlling the readout circuit 103. The readout circuit 103 includes an amplification circuit unit 202 that amplifies the electrical signal output in parallel from the pixel array 101, and a sample hold circuit unit 203 that samples and holds the electrical signal from the amplification circuit unit 202. Further, the readout circuit 103 includes a multiplexer 204 that sequentially outputs the electrical signals read in parallel from the sample hold circuit unit 203 and outputs the electrical signals as serial electrical signals.

The control unit 108 supplies a control signal 116 to the reset switches RC ₁ to ₈ of the amplifier circuit unit 202. The control unit 108 supplies control signals 120s, 120n, and 120oe to the sample and hold circuit unit. Further, the control unit 108 supplies a control signal 117 to the multiplexer 204. The amplifying circuit unit 202 amplifies the read electric signals and outputs them, operational amplifiers A ₁ to ₈ , integration capacitor groups Cf ₁ to _8, and reset switch RC ₁ that resets the integration capacitor groups Cf ₁ to _{8. Are provided} corresponding to each signal wiring. The electric signal output from the conversion element S is input to the inverting input terminals of the operational amplifiers A1 to _{A8, and} the amplified electric signal is output from the output terminal. The reference voltage Vref1 is input to the normal input terminals of the operational amplifiers A1 to _A8 .

The sample hold circuit unit 203 includes sampling switches SHOS ₁ to ₈ and sampling capacitors Chos _{1 to 8} that sample signal components in odd rows, sampling switches SHES ₁ to ₈ and sampling capacitors Ches _{1 to 8} that sample signal components in even rows. have.

Further, the sampling switches SHON ₁ to ₈ and sampling capacitors Chon _{1 to 8} for sampling the noise components of the odd rows, and the sampling switches SHEN ₁ to ₈ and sampling capacitors Chen _{1 to 8} for sampling the noise components of the even rows are configured. . Using these sampling switches and sampling capacities, correlated double sampling (CDS) processing is performed.

The multiplexer 204, the switch _MSON 1 to 8 correspond to the signal _{lines, MSEN 1~8, MSOS 1~8, MSES} 1~8, comprises respectively a. When the control unit 108 sequentially selects each switch of the multiplexer 204, an operation of converting a parallel electrical signal into a serial electrical signal 113 is performed.

  The converted serial electric signal 113 is input to the A / D converter 104 via the buffer amplifier SHA, converted into a digital signal 114, and sent to the digital signal processing means 105.

  Next, a radiographic imaging flow will be described with reference to the timing charts of FIGS. 3 and 4A. Hereinafter, a flow for acquiring an image (preview image) for confirming whether or not a radiographic image of a subject is captured and a radiographic image (diagnostic image) of the subject will be described in detail.

  When the radiologist instructs the radiation imaging apparatus 100 to start imaging, the radiation imaging apparatus 100 enters a state of performing an idling operation (S101). In processing 101, first, the control unit 108 supplies an operation control signal 118 to the power supply unit 107, and starts supplying power from the power supply unit 107 to the pixel array 101, the drive circuit 102, the readout circuit 103, and the A / D conversion unit 104. . Further, the control unit 108 supplies signals 116, 117, 119, and 120 for controlling the driving circuit 102 and the readout circuit 103, and controls the pixel array 101 to perform an idling operation.

In the idling operation, first, bias power is supplied from the power supply unit 107 to the conversion element S via the sensor bias wiring Vs. In this state, the drive wirings G1 to ₈ are sequentially scanned from the drive circuit 102 in units of rows, the switch elements T are sequentially turned on in units of rows, and the charges accumulated in the conversion elements S are reset. A state in which an idling operation for sequentially turning on the switch elements T in units of rows is repeatedly performed is referred to as an idling state.

Next, the control unit 108 determines whether or not the exposure button of the radiation generation apparatus 501 is turned on while the idling operation is performed (S102). The idling state is maintained until the exposure button is turned on. When the exposure button is turned on and the control unit 108 receives a confirmation signal via the communication signal 504, first, the reading circuit 103 is brought into a readable state. After making the state readable _, the reset operation of the drive wirings G _1, G _3, G _{5, and} G ₇ in odd-numbered rows is performed once.

  In the present embodiment, the reset operation is an operation for sequentially scanning the driving lines in the odd-numbered rows and resetting the electric signals accumulated in the pixels 201. The reset operation is performed in order to align the accumulation time (interval between ON and ON of the drive wiring) in the preview offset image reading operation and the preview image reading operation in order to accurately perform offset correction on the preview image. Here, the preview offset image reading operation is to read from a part of the pixels 201 of the pixel array 101 before the preview image reading operation, and corresponds to the third reading operation of the present invention. The preview image reading operation corresponds to the first reading operation of the present invention.

  After the reset operation, before the irradiation with radiation, the control unit 108 controls to perform a preview offset image reading operation (third reading operation) in order to read an electrical signal for offset correction of the preview image. (S103). By the process 103, the offset image for preview can be acquired before the radiation imaging apparatus 100 is irradiated with radiation. Therefore, the radiation imaging apparatus 100 can reduce processing after radiation irradiation is started, and can reduce time until a preview image is acquired.

  Thereafter, the radiation imaging apparatus 100 outputs a permission signal from the control unit 108 that radiation irradiation can be started when permission from the radiation generation apparatus 501 is permitted due to the exposure button being turned on. The permission signal is transmitted to the radiation control apparatus 502 via the communication signal 504 (S104).

  When the radiation control apparatus 502 receives the permission signal from the radiation imaging apparatus 100, the radiation control apparatus 502 controls the radiation generation apparatus 501 and starts radiation irradiation (S105).

  In the process 105, it is desirable that the control unit 108 starts a preview image reading operation after a predetermined period has elapsed after outputting the permission signal. This is because the radiation control device 502 has a specific delay time from when the permission signal is received until the radiation generation device 501 starts radiation irradiation. Therefore, if this delay time can be set as a predetermined period, an accurate preview image can be acquired.

  On the other hand, if the period of the image reading operation for previewing from the start of radiation irradiation is made long in the radiation irradiation period, the amount of electrical signals accumulated in the pixels 201 decreases. Therefore, it is preferable to set an appropriate time so as to reduce the influence on the diagnostic image and obtain a suitable preview image.

  Then, after a predetermined period has elapsed, the control unit 108 performs a preview image reading operation (first reading operation) (S106). In the process 106, the control unit 108 reads an electrical signal from a part of the pixels 201 of the pixel array 101 during the radiation irradiation period in order to acquire an electrical signal for confirming whether the radiographic image of the subject is captured. In the first embodiment, reading is performed from odd rows.

  By reading out the electrical signal during the radiation irradiation period, it is possible to reduce the time for acquiring the preview image even when the radiation irradiation is long.

  Further, since the preview image is an image for confirming whether or not the radiographic image of the subject is captured, the control unit 108 can read only from some pixels 201 of the pixel array 101. Therefore, it is possible to shorten the time until an image is acquired as compared with a diagnostic image described later.

  In the reset operation, the first read operation, and the third read operation of the first embodiment, only odd rows are read, but only even rows or only one row in a plurality of rows may be used. The control unit 108 may perform the preview image reading operation by reading out an electrical signal from the pixel array 201 by thinning out a predetermined row (hereinafter referred to as a thinning driving method). By thinning out predetermined rows in this way, the time until the preview image is acquired can be reduced. It is desirable to thin out more lines in order to obtain a preview image earlier as the interval between the lines read out by thinning out. On the other hand, since it is necessary to obtain a resolution that allows the preview image to grasp the position of the subject, it is preferable to select a reading interval by thinning out depending on the system. Furthermore, the control unit 108 may simultaneously read out electric signals from the pixels 201 in a plurality of rows (hereinafter referred to as a pixel addition method) by a preview image reading operation. By performing the pixel addition method, the resolution of the preview image can be increased and the signal amount can be increased. It is also possible to combine the thinning drive method and the pixel addition method. However, the reset operation and the third readout operation are preferably performed in accordance with a method of performing the preview image readout operation (first readout operation) in order to align the accumulation time.

  The preview image, which is an image based on the electrical signal read out by the preview image reading operation, is subjected to offset correction by calculating a difference from the preview offset image by the digital signal processing unit 105. (S107). By performing offset correction of the preview image, the resolution of the preview image can be increased. In addition, gain correction and defect correction can be performed on the preview image as necessary. Further, when shading occurs in the preview image, the shading correction unit 106 may perform shading correction described later.

  In addition, the preview image reading operation can read a smaller signal amount at a higher speed than a diagnostic image reading operation (second reading operation) described later. Therefore, the time for obtaining the preview image can be shortened by setting the filter band of the readout circuit 103 high, setting the readout gain of the readout circuit 103 high, or the like.

  After the radiation irradiation period (S108), the control unit 108 reads out the diagnostic image reading operation (second reading operation) for reading out an electrical signal for taking a radiographic image (diagnostic image) of the subject from the pixel array 101. (S109). Here, in order to acquire a diagnostic image, all the drive wirings in the pixel array 101 are scanned, and an image with high resolution is acquired.

  Next, a diagnostic offset image reading operation is performed (S110). The diagnostic offset image is used for offset correction of the diagnostic image.

  Here, when a non-semiconductor material such as amorphous silicon is used for the photoelectric conversion element, an image acquired by the read operation changes depending on a driving history before an arbitrary read operation. Therefore, it is preferable to give the same drive history as the diagnostic image reading operation before the diagnostic offset image reading operation. In the example of the first embodiment, the diagnostic offset image reading operation is performed after the idling, the preview offset image reading operation, and the preview image reading operation are sequentially performed.

After the diagnostic offset image read operation, offset correction is performed based on the difference between the acquired diagnostic image and the diagnostic offset image, and then the diagnostic image is corrected (S111).
An image correction unit that corrects diagnostic images other than offset correction will be described. In this embodiment, in order to obtain a preview image, only odd lines are read once immediately after the start of radiation irradiation. For this reason, since the accumulation amount of the electrical signals in the odd-numbered rows is small, the diagnostic image may require further resolution.

  The diagnostic image correction means includes an electrical signal read by the diagnostic image readout operation from the pixel in the pixel array on which the preview image readout operation has been performed, and a preview image readout operation in the pixel array. Correction is performed using an electrical signal read by a diagnostic image read operation from a pixel adjacent to the pixel and not subjected to the preview image read operation. In the present embodiment, for each odd-numbered row in the diagnostic image, the ratio between the odd-numbered row pixels and the pixels in the even-numbered rows that are adjacent pixels and for which the preview image is not read is calculated. Then, by multiplying the reciprocal of the ratio, it is possible to correct the electric signal lost for obtaining the preview image among the diagnostic images.

  In addition, as diagnostic image correction means, a diagnostic image can be corrected by adding a preview image, which is an image based on the electrical signal read out by the preview image reading operation, to the diagnostic image.

  Even when a preview image is acquired by the above-described diagnostic image correction means, the degradation of the resolution of the diagnostic image can be reduced.

  Next, the shading correction of the preview image will be described with reference to the timing chart of FIG. The time during which the electric signal is accumulated for each row of the pixel array from the start of the radiation irradiation period to the completion of the preview image reading operation is defined as the electric signal accumulation time. In the preview image reading operation of the embodiment, since the accumulation time of the electric signal is different for each row of the pixel array, shading occurs in the preview image. Therefore, in order to correct the preview image by the correction coefficient calculation means, each pixel is determined based on the difference in each pixel in the electrical signal accumulation time for each row of the pixel array and the number of rows on which the preview image reading operation is performed. A correction coefficient is calculated. Then, the shading correction of the preview image is performed by multiplying the pixels in each row by the correction coefficient. In the present embodiment, the correction coefficient calculation means is included in the shading correction unit 106.

Specifically, the readout time from the start of each radiation irradiation to the _first drive wiring G1 is TWAIT, and the time difference from one drive wiring to the next drive wiring is TLINE. If the number of rows read in the review image reading operation is N and the number of rows to be corrected is n, the correction coefficient Kn is expressed by the following formula (1).

  The shading correction unit 106 can correct the preview image by correcting the shading of the image due to the difference in the accumulation time of the electric signal for each row by multiplying the correction coefficient Kn. By performing the shading correction, it is possible to obtain a preview image that is more suitable for confirming the quality of radiographic image capture.

  As described above, by performing the preview image reading operation during the radiation irradiation period, the preview image can be acquired immediately regardless of the radiation irradiation period.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a conceptual diagram of an imaging system including a conceptual equivalent circuit diagram of an imaging apparatus according to the second embodiment of the present invention, and FIG. 6 shows the operation of the radiation imaging apparatus in the second embodiment. It is a timing chart. In addition, the same thing as the structure demonstrated in 1st Embodiment is provided with the same number, and detailed description is omitted.

  In the present embodiment, the radiation imaging apparatus 100 is configured to perform imaging without synchronization between the control unit 108 and the radiation control apparatus 502. In the present embodiment, the radiation imaging apparatus 100 includes a determination unit that determines that the pixel array 101 is irradiated with radiation. In the present embodiment, the determination unit is included in the control unit 108.

  The control unit 108 repeatedly performs the preview offset image reading operation before the radiation irradiation. The determination unit repeatedly obtains an image based on the electrical signal read by the preview offset image reading operation from the digital signal processing unit 105.

In the present embodiment, as an example, as illustrated in FIG. 6, immediately after the start of imaging, the control unit 108 scans the odd-numbered drive wirings G _1, G _3, G _5, G ₇ , and even-numbered drive wiring G. _{2, G 4,} repeated scanning of _G 6, _{G 8,} and repeatedly performs the offset image read operation for preview. Further, the control unit 108 repeatedly obtains the preview offset image from the odd-numbered row and the even-numbered row before the radiation irradiation, and updates the image every time it is repeatedly read out.

  When radiation irradiation is started, radiation information is added to the image read by the control unit 108 based on the preview offset image reading operation, so that the determination unit determines whether radiation has been irradiated from the read image. Can be determined. At this time, the determination means calculates the average value of the image based on the electrical signal read by the predetermined preview offset image read operation and the preview offset image read operation to be performed next, thereby determining the presence or absence of radiation irradiation. Can be determined.

  In FIG. 6, the determination unit is configured to display each of the preview offset image obtained by the odd preview offset image read operation (4) and the preview offset image obtained by the odd preview offset image read operation (3). When the difference between the average values is equal to or greater than the threshold value, it is possible to determine that radiation irradiation has started.

  Thereafter, the determination unit determines whether the calculated difference image is irradiated with a radiation dose that can be used as a preview image. In this case, as a threshold for the determination unit to determine, for example, a value that is 10 times or more the random noise of the preview image can be set as the threshold.

  As a method for the determination means to determine whether or not the irradiation of radiation to the pixel array 101 has been started, an electric signal read by a predetermined preview offset image read operation and then a preview offset image read operation is used. It can be determined that radiation irradiation has started when the difference from the average value of the based image is equal to or greater than the threshold value.

  Another determination method possessed by the determination means will be described. The determination unit starts radiation irradiation when the difference (contrast) between the maximum value and the minimum value in the image based on the electrical signal read by the preview offset image reading operation repeatedly performed by the control unit 108 is equal to or greater than a threshold value. It can also be determined that it has been done. For example, the difference in contrast between the part that has passed through the subject and the part that has not passed through during radiation irradiation can be used as a criterion.

Then, after the determination unit determines that radiation irradiation has started, the control unit 108 changes the control of the drive circuit 102 and the readout circuit 103 and enters a preview image readout operation. After determining that the radiation irradiation has started, if the predetermined reading operation at the time of the determination by the determination means is the even preview offset image reading operation, the control unit 108 controls the even-row drive wirings G _2, G _4, G _{6 and} G ₈ are scanned again, and the electric signals accumulated in the pixels before that are reset. The control unit 108 performs a preview image read operation after the reset operation. Thereafter, the digital signal processing means 105 performs preview offset correction on the preview image based on the read electrical signal. At this time, the control unit 108 performs the preview offset image acquired in the even preview offset image read operation (3) updated immediately before.

In the present embodiment, after irradiation, the control unit 108 scans the driving lines G _2, G _4, G _{6, and} G ₈ in even rows again, and resets the electrical signals accumulated in the pixels. Therefore, the accumulation time of the electric signals in each even row is the same. For this reason, there is a feature that shading due to the difference in electrical signal accumulation time hardly occurs in the preview image, and shading correction need not be performed on the preview image. Thereafter, a diagnostic image is acquired, and the subsequent steps are the same as in the first embodiment.

  As described above, in the radiation imaging apparatus that does not synchronize with the radiation control apparatus, it is possible to reduce the acquisition time of the preview image.

  Further, the method for acquiring the preview image described in the present embodiment is a method suitable for the radiation imaging apparatus that does not synchronize with the radiation generation apparatus illustrated in FIG. 5, but the radiation imaging apparatus illustrated in FIG. The radiation imaging apparatus shown in FIG. 7 described later in the embodiment can also be applied.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a conceptual diagram of a radiation imaging system including a conceptual equivalent circuit diagram of the radiation imaging apparatus according to the third embodiment of the present invention, and FIG. 8 is an operation of the radiation imaging apparatus according to the third embodiment. It is a timing chart which shows. In addition, the same thing as the structure demonstrated in 1st Embodiment is provided with the same number, and detailed description is omitted.

As in the second embodiment, the radiation imaging apparatus 100 according to the present embodiment is configured to perform imaging without synchronizing the control unit 108 and the radiation control apparatus 502. In the present embodiment, the control unit 108 repeats the scanning in the odd-numbered rows of the driving line _{G 1, G 3, G 5} , the scanning of the _{G 7,} even row drive lines _{G 2, G 4, G 6} , G 8 Yes. Further, the control unit 108 monitors the current flowing through the sensor bias wiring Vs by the radiation current monitoring unit 300 and determines the presence or absence of radiation irradiation.

  A flow of offset correction of a preview image and acquisition of a preview image and a preview offset image in the present embodiment will be described.

  When radiation irradiation is started, the control unit 108 detects radiation irradiation, and resets the electrical signal accumulated in the pixel 201 by performing a reset operation once. The control unit 108 performs a preview offset image read operation after the TOFFSET time has elapsed from the start of radiation irradiation, and further performs a preview image read operation after the TXRAY time has elapsed. Then, the digital signal processing means 105 performs offset correction by calculating a difference between images based on these reading operations. As a result, an electrical signal proportional to the time obtained by subtracting the TOFFSET time from the TXRAY time is accumulated, and a preview image can be acquired. Further, as in the second embodiment, the accumulation time of the electric signals of each row in the pixel array 101 in which the preview offset image reading operation has been performed is almost the same, so that no shading correction is required for the preview image. Good.

  As described above, the offset correction of the preview image is performed by calculating the difference between the image acquired by the preview image reading operation and the preview offset image acquired between the start of the radiation irradiation and before the preview image reading operation is performed. It can be corrected by calculating.

  The offset correction of the preview image described in the present embodiment described above is a method suitable for the radiation imaging apparatus capable of detecting the presence or absence of radiation irradiation shown in FIG. However, the correction method in this embodiment can be applied even to the radiation imaging apparatus shown in the first and second embodiments.

(Fourth embodiment)
FIG. 9 is a schematic diagram showing an application example to the radiation imaging system 400 which is an embodiment of the radiation imaging apparatus of the present invention. The radiation imaging apparatus 100 according to any one of the embodiments of the present invention is applied to a radiation imaging system 400 that is an embodiment of the radiation imaging apparatus.

  The radiation imaging system 400 includes a radiation generator (not shown), an X-ray tube 6050 as a radiation source, the radiation imaging apparatus 100, an image processor 6070 as a signal processing unit, and displays 6080 and 6081 as display units. Have. Further, the radiation imaging system 400 includes a film processor 6100 and a laser printer 6120 in addition to these.

  Radiation (X-rays) generated by an X-ray tube 6050 serving as a radiation source passes through an imaging region 6062 of a subject (subject) 6061 and enters the radiation imaging apparatus 100. The radiation incident on the radiation imaging apparatus 100 includes information inside the imaging region 6062 of the subject (subject) 6061.

  As in the first embodiment, the radiation imaging apparatus 100 permits radiation irradiation from a radiation source when radiation irradiation is permitted when an exposure button of a radiation generation apparatus (not shown) is turned on. Is output to the radiation generator. When the radiation generation apparatus receives the permission signal from the radiation imaging apparatus 100, the radiation generation apparatus controls the radiation source and starts radiation irradiation. The radiation imaging apparatus 100 outputs a permission signal from the control unit 108 and then starts a preview image reading operation after a predetermined period.

  When radiation enters the radiation imaging apparatus 100, information on the imaging region 6062 of the electrical subject (subject) 6061 is obtained. This information is converted into a digital format and output to an image processor 6070 as signal processing means.

  The image processor 6070 as a signal processing unit is a computer including a CPU, a RAM, and a ROM. Further, the image processor 6070 has a recording medium capable of recording various types of information as recording means. For example, the image processor 6070 has a built-in HDD, SSD, recordable optical disk drive, or the like as recording means. Alternatively, the image processor 6070 may be externally connectable to an HDD or SSD as a recording unit, a recordable optical disk drive, or the like.

  Then, an image processor 6070 as a signal processing unit performs predetermined signal processing on the information and displays the information on a display 6080 as a display unit.

  When the radiation imaging apparatus 100 of the present embodiment is applied as the radiation imaging system 400, a preview image reading operation can be performed during the radiation irradiation period after the start of radiation irradiation, and a preview image can be acquired. Therefore, even when the radiation irradiation time is long, the preview image is displayed immediately, and the subject (subject) and the examiner (user) can confirm the preview image.

  Further, the image processor 6070 can record this information on an HDD, SSD, or recordable optical disk drive as a recording means.

  The image processor 6070 may be configured to have an interface capable of transmitting information to the outside as information transmission means. As such an interface as a transmission means, for example, an interface to which a LAN or a telephone line 6090 can be connected is applicable.

  The image processor 6070 can transmit this information to a remote place through an interface as a transmission means. For example, the image processor 6070 transmits this information to a doctor room located away from the X-ray room in which the radiation imaging apparatus 100 is installed. Thereby, a doctor or the like can diagnose a subject (subject) in a remote place. The radiation imaging system 400 can also record this information on the film 6210 by a film processor 6100 as recording means.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also within the scope of the present invention. included. Furthermore, each embodiment mentioned above is only what shows one embodiment of this invention, and it is also possible to combine each embodiment suitably.

DESCRIPTION OF SYMBOLS 100 Radiation imaging apparatus 101 Pixel array 102 Drive circuit 103 Reading circuit 104 A / D converter 105 Digital signal processing means 106 Shading correction part 107 Power supply part 108 Control part 201 Pixel 202 Amplifying circuit part 203 Sample hold circuit part 204 Multiplexer 400 Radiation imaging System 501 Radiation generation device 502 Radiation control device 6070 Signal processing means 6080 Display means

Claims (15)

A pixel array in which a plurality of pixels that accumulate electrical signals corresponding to radiation transmitted through the subject are arranged in a matrix;
A control unit for controlling a read operation for reading out the electrical signal transferred from the pixel array;
In a radiation imaging apparatus for capturing a radiation image of the subject,
The control unit reads out an electrical signal for confirming whether or not a radiographic image of the subject is captured from a part of pixels of the pixel array during a radiation irradiation period in which the radiation is irradiated on the pixel array. A radiation imaging apparatus that controls to perform a readout operation and a second readout operation that reads out an electrical signal for capturing a radiographic image of the subject from the pixel array after the radiation irradiation period. .   The radiation imaging apparatus according to claim 1, wherein the first reading operation reads out an electric signal from the pixel array by thinning out a predetermined row.   The radiation imaging apparatus according to claim 1, wherein the first readout operation simultaneously reads out an electrical signal from a plurality of rows of pixels.   The control unit reads out an electrical signal for offset correction of an image based on the electrical signal read out by the first readout operation from a part of pixels of the pixel array before the first readout operation. 4. The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus is controlled so as to perform three readout operations. 5.   The control unit reads out an electrical signal for offset correction of an image based on the electrical signal read out by the first readout operation from a part of pixels of the pixel array before the radiation irradiation period. The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus is controlled so as to perform a reading operation.   An offset for performing the offset correction by calculating a difference between an image based on the electrical signal read out by the first readout operation and an image based on the electrical signal read out by the third readout operation. The radiation imaging apparatus according to claim 4, further comprising a correction unit. A determination unit for determining that the irradiation of the radiation is started with respect to the pixel array;
The determination means includes an average value of images based on an electrical signal read by a predetermined third read operation among the third read operations that are repeatedly performed, and the next to the predetermined third read operation. When the difference between the average value of the images based on the electrical signal read out by the next third readout operation to be performed is equal to or larger than a threshold value, it is determined that the irradiation of the radiation is started. The radiation imaging apparatus according to any one of claims 4 to 6. A determination unit for determining that the irradiation of the radiation is started with respect to the pixel array;
The determination unit determines that the radiation irradiation has started when a difference between a maximum value and a minimum value of an image based on the electrical signal read by the third read operation is equal to or greater than a threshold value. The radiation imaging apparatus according to claim 4, wherein the radiation imaging apparatus is a radiographic imaging apparatus. The difference between each pixel in the time during which an electric signal was accumulated for each pixel of the pixel array from the start of the radiation irradiation period to the completion of the first readout operation, and the first readout operation were performed. Correction coefficient calculating means for calculating a correction coefficient for each pixel based on the number of rows;
Shading correction means for performing shading correction of the image acquired in the first readout operation using the correction coefficient;
The radiation imaging apparatus according to claim 1, further comprising: Image correction means for correcting an image based on the electrical signal read by the second read operation;
The image correction unit is configured to output an electrical signal read out from a pixel in the pixel array that has undergone the first reading operation by the second reading operation, and to perform the first reading operation in the pixel array. The correction is performed using an electrical signal read by the second reading operation from a pixel adjacent to the performed pixel and not performing the first reading operation. The radiation imaging apparatus according to any one of 9. Image correction means for correcting an image based on the electrical signal read by the second read operation;
The image correcting means adds the image based on the electrical signal read out by the first readout operation to the image based on the electrical signal read out by the second readout operation, thereby The radiation imaging apparatus according to claim 1, wherein an image based on an electric signal read by a reading operation is corrected. A pixel array in which a plurality of pixels that accumulate electrical signals corresponding to radiation transmitted through the subject are arranged in a matrix;
A control unit for controlling a read operation for reading out the electrical signal transferred from the pixel array;
In a radiation imaging apparatus for capturing a radiation image of the subject,
The control unit performs a first read operation for reading an electrical signal for confirming whether a radiographic image of the subject is captured from some pixels of the pixel array, and the radiation is applied to the pixel array. A second readout operation of reading out an electrical signal for capturing a radiographic image of the subject in the radiation irradiation period from the pixel array after the radiation irradiation period, and performing the first readout operation on the radiation A radiation imaging apparatus that is controlled to perform during an irradiation period. The radiation imaging apparatus according to any one of claims 1 to 12,
Signal processing means for processing signals from the radiation imaging apparatus;
Display means for displaying an image processed by the signal processing means;
A radiation imaging system comprising: The signal processing means processes a signal based on the electrical signal read by the first read operation during the radiation irradiation period,
The radiation imaging system according to claim 13, wherein the display unit displays an image processed by the signal processing unit during the radiation irradiation period. The radiation imaging system further includes a radiation generator that emits radiation to the subject,
The control unit performs control so that the first reading operation is started after a predetermined period of time has elapsed since the radiation imaging apparatus outputs a permission signal for allowing irradiation of radiation to the radiation generation apparatus. The radiation imaging apparatus according to claim 13 or 14, characterized in that:

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