JP2015226106A - Radiation imaging device, and control method and program therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten the burden on a user by determining whether a noise level appearing in a radiation image is within a permissible range by a radiation imaging device.SOLUTION: A radiation imaging device includes a plurality of sensors forming pluralities of rows and columns, a drive part 120 which drives the plurality of sensors, row by row, a detection part 150 which detects a start of irradiation with radiation, and a control part 160, and performs first control to control the drive part to repeatedly initialize the plurality of sensors, row by row, before the irradiation with radiation starts and second control to control the drive part so that the initialization is interrupted in response to detection of the start of the irradiation with radiation by the detection part and then the plurality of sensors output signals. Based upon differences between signals from sensors in a row initialized finally in the first control among signals output from the plurality of sensors under the second control and signals from sensors in other rows, it is determined whether the signals from the plurality of sensors satisfy a predetermined standard.

Description

  The present invention relates to a radiation imaging apparatus, a control method thereof, and a program.

  A radiation imaging apparatus (hereinafter referred to as “apparatus”) includes, for example, a plurality of sensors arranged on a substrate and a drive unit that drives each sensor. In the plurality of sensors, charges due to the dark current of the substrate and the like are accumulated. Therefore, before the radiation irradiation is started, the driving unit performs an initialization operation to repeatedly initialize the plurality of sensors in units of rows. . Then, the initialization operation is interrupted in response to the start of radiation irradiation, and the plurality of sensors are driven by the drive unit so that signals corresponding to the radiation dose are output from the plurality of sensors.

  Some apparatuses are further provided with a detection unit for detecting that radiation irradiation has started, and some apparatuses are capable of performing signal readout by determining that radiation imaging has started. . For example, Patent Document 1 has a configuration in which the amount of current generated by charges discharged from a plurality of sensors in the initialization operation is monitored, and the start of radiation irradiation is detected based on the amount of current. It is disclosed. According to this configuration, the apparatus can determine by itself that radiation irradiation has started, interrupt the initialization operation, and output signals from a plurality of sensors by the drive unit.

JP 2010-268171 A

  By the way, there is a delay in detection from the start of radiation irradiation until the detection unit detects the start of the irradiation. Therefore, in the sensor that has been initialized between the start of radiation irradiation and the start of the irradiation is detected, a part of the signal component based on the irradiated radiation is lost, and the device A gray level difference appears as noise in a part of the obtained radiographic image.

  On the other hand, it is also possible to compensate for the signal component lost by initialization by performing correction processing on the radiation image. However, since the signal from the sensor may include a noise component due to random noise in addition to the signal component, the signal component is corrected and the noise component is also corrected by the correction process. Will remain.

  The noise described above can increase the burden on the user, for example, when a radiographer or the like visually confirms a radiographic image obtained from the apparatus every time radiography is performed.

  An object of the present invention is to provide a technique that is advantageous for reducing the burden on the user by determining whether or not the level of noise appearing in a radiographic image is within an allowable range by using a radiographic imaging device.

  One aspect of the present invention relates to a radiation imaging apparatus, which includes a plurality of sensors arranged to form a plurality of rows and a plurality of columns, and a drive for driving the plurality of sensors in units of rows. A radiation imaging apparatus comprising: a detection unit that detects that irradiation of radiation to the plurality of sensors has started; and a control unit, wherein the control unit has started irradiation of radiation Before the detection unit detects the first control for controlling the drive unit to repeatedly initialize the plurality of sensors in units of rows, and that the detection unit has detected that radiation irradiation has started. And the second control for controlling the drive unit so that the plurality of sensors output signals, and the radiation imaging apparatus is output by the second control. From the plurality of sensors Among the signals, the plurality of signals output by the second control based on a difference between a signal from a sensor in a row last initialized by the first control and a signal from a sensor in another row. It further comprises a unit for determining whether or not the signal from the sensor meets a predetermined reference.

  According to the present invention, it is possible to determine whether or not the level of noise appearing in a radiographic image is within an allowable range with the radiographic imaging device, which is advantageous in reducing the burden on the user.

The block diagram for demonstrating the example of whole structure of a radiation imaging device. The figure for demonstrating the structural example of a sensor and a reading part. The figure for demonstrating the example of the drive method of a sensor. The figure for demonstrating the example of the operation | movement flowchart of a radiation imaging device. The figure for demonstrating the example of the image data containing the information of a subject. The figure for demonstrating the example of the drive method of a sensor. The figure for demonstrating the example of the operation | movement flowchart of a radiation imaging device.

(Configuration example of radiation imaging system)
FIG. 1 is a block diagram for explaining a system configuration of a radiation imaging apparatus or radiation inspection apparatus IA (hereinafter simply referred to as “apparatus IA”) represented by a radiation imaging system. The apparatus IA includes an imaging unit 100, for example, and performs radiation imaging by receiving radiation from the radiation source 20. Specifically, the radiation control unit 30 controls the radiation source 20 to generate radiation in response to the exposure switch 40 being pressed. Radiation includes X-rays, α rays, β rays, γ rays and the like.

  Radiation from the radiation source 20 passes through a subject (not shown) such as a patient, for example, and the imaging unit 100 generates image data based on the radiation. The generated image data is subjected to arithmetic processing by an arithmetic processing unit 50 such as a processor, and is output as a radiation image to a display unit 60 such as a display. A user such as a radiologist can use the terminal 70 to input information necessary for performing radiographic imaging such as imaging conditions to the arithmetic processing unit 50, and save imaging results such as image data. Alternatively, it can be transmitted to other terminals via a communication means such as a wireless LAN.

  The imaging unit 100 includes a sensor array 110, a drive unit 120, a signal processing unit 130, a voltage supply unit 140, a detection unit 150, and a control unit 160.

  The sensor array 110 is formed by a plurality of sensors arranged to form a plurality of rows and a plurality of columns. A scintillator (not shown) that converts radiation into light can be disposed on the sensor array 110. In this case, for example, a PIN photodiode or a MIS photodiode is used as the sensor, and the sensor is formed using, for example, amorphous silicon on a glass substrate. Here, an indirect conversion type configuration in which radiation is converted into light and photoelectric conversion of the light is illustrated, but a direct conversion type configuration in which radiation is converted into an electric signal (directly) may be adopted.

  The drive unit 120 drives (or controls) the sensor array 110, and supplies a drive signal (or control signal) to each sensor via, for example, a signal line arranged in each row of the sensor array 110. Drive in units.

  The signal processing unit 130 performs signal processing on signals from the respective sensors driven by the driving unit 120 (hereinafter sometimes simply referred to as “sensor signals”). The signal processing unit 130 includes, for example, a reading unit 131, an AD conversion unit 132, and a data generation unit 133. The reading unit 131 reads a signal from the sensor for each column of the sensor array 110. The AD conversion unit 132 performs analog-digital conversion (AD conversion) on the read sensor signal. The data generation unit 133 generates image data based on the AD converted sensor signal.

  The voltage supply unit 140 supplies a power supply voltage to each unit of the imaging unit 100. The voltage supply unit 140 may include, for example, a voltage generation unit (not shown) that generates a plurality of power supply voltages for receiving a power supply voltage from the outside and supplying it to each unit. The voltage supply unit 140 supplies each unit with a power supply voltage necessary for the unit to operate properly.

  The detection unit 150 detects that radiation irradiation has started. For example, the detection unit 150 monitors the state of the voltage supply unit 140 (for example, a change in current amount or a change in voltage value), and radiation irradiation is started and the state of the voltage supply unit 140 has changed. In response, a detection signal is output.

  The control unit 160 controls each unit of the imaging unit 100 and controls the overall operation of the imaging unit 100. For example, the control unit 160 controls the operations of the driving unit 120 and the signal processing unit 130 with a control signal. In addition, for example, the control unit 160 can perform synchronization control between the units in response to a detection signal from the detection unit 150, and can change the operation mode of the imaging unit 100, for example.

  The apparatus IA is not limited to the above configuration example, and may adopt a configuration in which another unit has a part of the functions of each unit described above, or further includes a unit having another function. Also good.

FIG. 2 shows a specific configuration example of the sensor array 110 and the reading unit 131 in the apparatus IA. In addition to the sensors S (S _{11 to} S ₈₈ ), corresponding switch elements T (T _{11 to} T ₈₈ ) are arranged in the sensor array 110. The switch element T includes a thin film transistor (TFT), for example, and is connected to a corresponding sensor S. One sensor S and one switch element T corresponding to the sensor S form one pixel PX (PX _{11 to} PX ₈₈ ). For ease of explanation, the sensor array 110 of 8 rows × 8 columns is illustrated in the figure, but the number of rows and the number of columns are not limited to these quantities.

The gate terminal of the switch element T in each row is connected to a signal line L _TX (L _{TX1 to} L _TX8 ) arranged so as to correspond to each row. The signal line L _TX propagates a drive signal from the drive unit 120. With such a configuration, the switch element T receives the drive signal from the drive unit 120 at the gate terminal.

  For example, when the drive signal is at a low level (L), the switch element T is in a non-conductive state, and the electric charge generated by the sensor S is accumulated in the sensor S. On the other hand, when the drive signal is at a high level (H), the switch element T is in a conductive state, and a sensor signal is output from the sensor S to the column signal line LC arranged in each column via the switch element T. . The signal value of the sensor signal depends on the amount of charge accumulated in the sensor S while the switch element T is in a non-conducting state.

The sensor S is connected to the bias line V _S at a terminal opposite to the side to which the switch element T is connected. The sensor S is connected to the ground from the voltage supply unit 140 via the bias line V _S. Receive power supply voltage. The aforementioned detecting unit 150, for example, has a function to monitor the amount of current of the bias line V _S. Although details will be described later, before the start of radiation imaging (that is, before the start of radiation irradiation), the driving unit 120 performs an initialization operation to initialize (reset) the sensor S, The unit 150 monitors the amount of current of the bias line V _S. When radiation irradiation is started during the initialization operation, the current amount of the bias line V _S increases. Thereby, the detection part 150 can detect that irradiation of a radiation was started.

The reading unit 131 includes, for example, a signal amplification unit U _A that amplifies the sensor signal, a sampling unit U _SH that samples the amplified signal, and an output unit U _OUT that outputs the sampled signal.

Signal amplifier U _A includes are disposed in each column, for example, an amplifier circuit A1 and the feedback capacitor C _FB. The feedback capacitor _CFB is arranged to connect the output terminal of the amplifier circuit A1 and one input terminal. The column signal line LC is connected to the one input terminal of the amplifier circuit A1. A reference potential _VREF is connected to the other input terminal of the amplifier circuit A1. With this configuration, the signal amplification unit U _A amplifies the sensor signal.

The signal amplification unit _{U A} further includes a switch SW1～SW2. The switch SW1 is disposed between the column signal line LC and the reference potential _VREF, and can be maintained in a conductive state while the sensor signal is not being read. The switch SW2 is arranged in parallel with the feedback capacitor _CFB (so that the output terminal of the amplifier circuit A1 and one input terminal are connected), and the amplifier circuit A1 is turned on by making the switch SW2 conductive. Can be initialized. The switches SW1 and SW2 may be controlled by the same control signal or may be individually controlled by different control signals. At this time, the potential of the output potential and the signal amplifier U _A column signal line LC is a reference potential V _REF.

Sampling unit _{U SH} includes are disposed in each column, for example, a sample and hold circuit SH1～SH4. The circuits SH1 to SH4 sample a signal including a signal component corresponding to the radiation dose (hereinafter referred to as S signal) or a signal not including the signal component (hereinafter referred to as N signal). The N signal is a signal corresponding to an offset component caused by a circuit configuration, element variation, or the like. For example, the circuit SH1 samples the S signal from the sensor S in the odd rows (first row, third row,..., Seventh row), and the circuit SH2 receives the N signal from the sensor S in the odd row. Sampling. Similarly, the circuit SH3 samples the S signal from the sensor S in the even-numbered rows (second row, fourth row,..., Eighth row), and the circuit SH4 receives the N signal from the sensor S in the even-numbered row. Is sampled. When performing a reading operation for reading out sensor signals, the sampling unit _USH alternately performs sampling of sensor signals in odd rows and sampling of sensor signals in even rows, for example.

The output unit U _OUT sequentially outputs the S signal and the N signal from the sampling unit U _SH to the AD conversion unit. The output unit U _OUT includes, for example, amplifier circuits A2 _S , A2 _N, and A3. Amplifier circuit A2 _S amplifies the S signal, the amplifier circuit A2 _N amplifies the N signal. Amplifier circuit A2 _S and A2 _N may be, for example, a source follower circuit which performs a source follower operation in response to a signal from the sampling unit U _SH. Amplifier A3 will amplifies the difference between the N signal output of the S signal from the amplifier circuit A2 _S from amplifier A2 _N.

  The reading unit 131 performs correlated double sampling processing (CDS processing) of the sensor signal with the configuration exemplified above. Thereafter, the sensor signal is AD-converted by the AD conversion unit 132, and image data is generated by the data generation unit 133 based on the AD-converted sensor signal. Note that the reading unit 131 is not limited to the above configuration example. For example, a signal or data corresponding to the difference between the S signal and the N signal may be obtained outside the reading unit 131. Further, a part of the circuit configuration of the reading unit 131 may be changed, or the reading unit 131 may further include a circuit that performs other signal processing.

(First embodiment)
The first embodiment will be described with reference to FIGS.

FIG. 3A shows an operation timing chart for driving the sensor S. In the figure, the horizontal axis as a time axis, and the operation mode, the irradiation condition of radiation, and a control signal RES, a drive signal TX1～TX8, and the amount of current I _S, are respectively shown. Control signal RES is a signal for controlling the switches SW1 and SW2, control signal RES becomes conductive switches SW1 and SW2 are by the H, the signal amplification unit _{U A} is initialized. The drive signal TX1 or the like is a drive signal that propagates through the signal line _LTX1 or the like. The current amount I _S is the amount of current flowing through the bias line V _S.

  When performing radiography, the apparatus IA, for example, performs an initialization operation RS before radiation is irradiated, and interrupts the initialization operation RS in response to the start of radiation irradiation and accumulates the operation. AO and read operation RO are performed. Thereby, the apparatus IA performs the first reading for acquiring the image data based on the irradiated radiation.

Thereafter, device IA, the above operation RS, with AO and RO the same procedure, performed initialization operation RS _F, the accumulation operation AO _F and read operations RO _F, in a state in which radiation is not irradiated. Thereby, the apparatus IA performs the second reading for acquiring the image data in a state where the radiation is not irradiated. Specifically, in each sensor S, electric charges are generated and accumulated due to dark current or the like even when radiation is not irradiated. The image data is formed based on a sensor signal corresponding to the charge. Then, by performing correction processing on the image data obtained by the first reading described above using the image data obtained by the second reading, noise components caused by dark current and the like are removed. The The second reading is also referred to as “dark image reading”, and the image data obtained by the dark image reading is also referred to as “dark image data”.

First, in the initialization operation RS, the initialization of the plurality of sensors S is repeatedly performed in units of rows. Specifically, in the initialization operation RS, the control signal RES is H, and the above-described switches SW1 and SW2 are maintained in a conductive state. Meanwhile, the drive signals TX1 to TX8 are sequentially set to H, and the switch elements T in the first row to the eighth row are sequentially turned on. As a result, the charge generated in the sensor S is released to the reference potential V _REF via the column signal line LC. In this way, the sensors S in each row are initialized in order.

When radiation irradiation is started, the amount of charge generated by each sensor S increases. As a result, the amount of charge (here, electrons) released to the reference potential V _REF in the initialization operation RS is increased, and the amount of charge (here, holes) flowing through the bias line V _S , that is, the current amount _IS is also increased. growing. The detection unit 150 described above can detect the start of radiation irradiation based on, for example, the current amount _IS or the change thereof, and can output a detection signal.

Since the amount of current _IS is mainly obtained by time-integrating charges generated according to radiation, the amount of current _IS is increased, for example, as time elapses after the irradiation of radiation is started. Increase at a constant rate. When the amount of current I _S is greater than a predetermined threshold I _TH, the detection unit 150 determines that the irradiation of the radiation is started, outputs a detection signal. Here, the detection signal is output when the sensor S in the fifth row is initialized. Then, in response to the detection signal, the initialization operation RS is interrupted and the accumulation operation AO is started.

Here, the detection unit 150, illustrate the embodiments of detecting the start of irradiation of the radiation on the basis of the current amount I _S, the method of detection of the start of the irradiation is not limited to this embodiment. For example, the detection unit 150 may detect the start of the irradiation based on the amount of current of the reference potential V _REF or a change thereof, and signals from other wirings (power supply lines and signal lines) connected to the sensor S. The start of the irradiation may be detected based on Alternatively, another sensor different from the plurality of sensors S may be provided, and the start of radiation irradiation may be detected based on a signal from the other sensor.

  In addition, in the drawing, initialization operation RS of one round of the first row to the eighth row and the initialization interrupted in the next first row to the fifth row is shown. However, the initialization of the sensors S in each row is repeated until radiation irradiation is started. Moreover, about the initialization operation | movement RS, although the aspect initialized in order of the 1st line-the 8th line is illustrated here, the order of the line | wire to initialize is not restricted to this aspect.

  In the accumulation operation AO, the switch element T is maintained in a non-conductive state until radiation irradiation is completed for a predetermined period after the initialization operation RS is interrupted. Thereby, in each sensor S, the electric charge of the quantity according to the irradiated radiation dose is accumulate | stored.

In read operation RO, controls the signal RES to the signal amplification unit U _A in the L in the active state, into a conductive state of the first to eighth rows of the switching element T in order to turn H drive signal TX1～TX8. Thereby, signals corresponding to the charges generated by the sensor S are sequentially read out by the reading unit 131, and the first reading for acquiring image data based on the irradiated radiation is completed.

Thereafter, second reading for acquiring image data in a state where no radiation is irradiated (that is, dark image reading for acquiring dark image data) is started. Specifically, in the control signal RES H again performs the initialization operation RS _F and accumulation operation AO _F, then, performs a reading operation RO _F control signal RES again in the L. As described above, the series of operations RS _F , AO _F, and RO _F are performed in a state where radiation is not irradiated.

The initialization operation RS _F is performed in the same manner as the above-described initialization operation RS. After the sensor S is initialized at least once for all rows, the same row as the row where the initialization operation RS is interrupted (here) Then, it can be interrupted at the fifth line). Here, for ease of explanation, an example in which the initialization operation RS _F is interrupted after initialization for one round of the first to eighth rows is illustrated, but the initialization operation RS _F May be interrupted after initialization for two or more rounds.

Accumulation operation AO _F is the time for maintaining the switching element T in the non-conducting state, it may be made to be equal to the time for maintaining the switching element T in storage operation AO described above in a non-conductive state. Thereafter, signals corresponding to the charges accumulated in the sensor S in a state where no radiation is irradiated are sequentially read out by the reading operation RO _F , and dark image data is obtained. Further, thereafter, correction processing is performed on the image data obtained by the read operation RO using the dark image data.

  FIG. 3B shows, for each row, the average value of the signal value or data value of each row in the image data subjected to the correction processing in the example of FIG. The horizontal axis indicates row numbers (R1 to R8). Here, in order to facilitate understanding, a case will be considered in which radiation is uniformly applied (specifically, the detected radiation does not include in-vivo information of the subject). The sensor signal may include a signal component corresponding to the radiation dose and a noise component corresponding to the time from the last initialization in the initialization operation RS to the drive in the readout operation RO. Therefore, when the radiation is uniformly applied, the signal values of the respective rows are substantially equal to each other.

In this example, it is detected that radiation irradiation is started at the time of initialization of the fourth row, and that radiation irradiation is started at the time of initialization of the fifth row. Therefore, in the initialization of the fourth to fifth rows, in addition to the noise component corresponding to the electric charge accumulated in the sensor S in a state where no radiation is irradiated, one of the signal components corresponding to the irradiated radiation dose is used. The part has been initialized. As a result, as shown in FIG. 3B, the signal values of the fourth to fifth rows (R4 to R5) are smaller than the signal values of the other rows. For example, in the fifth row, which is an initialization target when the start of radiation irradiation is detected (specifically, when a detection signal is output by the detection unit 150), initialization is performed during radiation irradiation. There is a difference A in signal value between other rows (R1 to R3 and R6 to R8) that are not present. The signal value difference A is
A = D × T2 / T1
D: Signal value of another row not initialized during radiation irradiation T1: Radiation irradiation time T2: Time from the start of radiation irradiation until the start of the irradiation is detected. As described above, the current amount _IS is mainly obtained by time-integrating charges generated according to radiation. Therefore, if the threshold value I _TH for detecting the start of radiation irradiation is a fixed value, the signal value difference A is substantially constant, and if the radiation dose or radiation intensity is constant. The time T2 is also substantially constant.

  Here, when a radiographic image based on the image data is displayed on the display unit 60, the radiographic image has a difference in shading due to the signal value difference A (hereinafter simply referred to as “step noise”). Appears.) When a step noise appears in a radiographic image, typically, a user of a device IA such as a radiographer performs radiography again, which causes an increase in the burden on the user, and May increase the burden on the person. In particular, when performing multiple times of radiography, such as in continuous imaging mode, the radiographic image will be confirmed each time the radiography is performed.

  Therefore, in this embodiment, based on the signal value difference A, it is determined whether or not the noise level of the step is acceptable. The determination is made, for example, by determining whether the ratio A / D between the signal value difference A and the signal value D of another row that has not been initialized during the irradiation of radiation is larger or smaller than a predetermined reference value. Can be made based on In other words, when the signal value D is sufficiently larger than the signal value difference A, noise in a step due to the signal value difference A can be allowed. Specifically, for example, when the ratio A / D is smaller than 1%, it is determined that the step noise is allowed, and when the ratio A / D is larger than 1%, the step noise is allowed. Judge that it is not. In the present specification, the above determination may be simply referred to as “determination”.

  The device IA can notify (or notify) the user of the determination result by displaying it on the display unit 60, for example, but the device IA further includes another notification unit for performing the notification. It may be. The determination result may be output in characters, but may be notified by generating a sound, or may be notified by blinking or lighting an LED or the like.

  The signal value difference A described above is caused by a detection delay of the detection unit 150 from the start of radiation irradiation until the detection unit detects the start of the irradiation. Therefore, for example, when an amount of radiation that is not sufficient for appropriately performing radiography is accidentally applied, or when the sensitivity of the detection unit is set to be small, the detection delay becomes large. . Therefore, the user only needs to perform radiation imaging again under imaging conditions that can determine that the level of the noise in the step in the radiographic image is acceptable.

  The apparatus IA can also notify the user of candidates for imaging conditions that can be determined to be acceptable. The candidate may be notified using the display unit 60 or other display means or notification means. The candidates can include, for example, the dose or intensity of radiation to be irradiated, the irradiation time, and the like. In addition, for example, when the sensitivity of radiation detection by the detection unit 150 can be changed, the candidate can include the sensitivity to be set for the detection unit 150. These candidates can be calculated based on, for example, the ratio A / D, the signal value D, and other image data information.

  In the above example, the aspect in which the determination is made based on the ratio A / D is illustrated. However, the determination may be made based on the absolute value of the noise of the step, for example, the signal value difference A. May be made on the basis.

  Further, the determination is performed on the signal value of the row that is the initialization target when the detection signal is output (that is, the row when the initialization operation RS is interrupted, the fifth row in the above example), It suffices to be based on the difference from the signal values of other rows (signal value D in the above example). In the above-described example, the other rows may be, for example, the sixth row that is the next row after the fifth row, or may be rows after that (the seventh row or the eighth row). However, for the lines before the fifth line, in the case of the above example, since part of the signal component is lost due to initialization at the start of radiation irradiation in the fourth line, the first to third lines The signal value of is preferably applied. That is, a predetermined number of rows (for example, the number of rows set in advance by the user or the number of rows calculated based on the irradiated radiation dose) than the row to be initialized when the detection signal is output. It is good if the signal value of the previous row is used. Alternatively, the determination may be made based on the difference between the signal value of the fifth row to be initialized and the average value of the signal values in all the rows other than the fifth row.

  Since radiography is actually performed based on the radiation that has passed through the subject, the radiation that actually enters the imaging unit 100 is not uniform and may include in-vivo information of the subject. Therefore, as illustrated in FIG. 3B, the determination may be made based on the average value of the signal values for each row. Alternatively, the determination may be performed based on the median value or the mode value instead of the average value, or may be performed based on the statistical result of the signal value of each row such as a standard deviation.

  In addition, for example, radiation often enters the central region of the sensor array 110 (for example, the third to fourth columns in the example of FIG. 2) through the subject. In many cases, the light enters the end region (for example, the first row or the eighth row) without passing through the subject. Therefore, for example, the determination may be performed based on the data value corresponding to the end region in the image data. Alternatively, the determination may be performed based on a weighted average of the data value corresponding to the end region and the data value corresponding to the central region. In the weighted average, for example, the coefficient used for the data value corresponding to the end region may be set larger than the coefficient used for the data value corresponding to the central region.

  The above-described determination can be made by, for example, the arithmetic processing unit 50, but the configuration of the unit that performs the determination is not limited to this mode. For example, the imaging unit 100 may further include a determination unit for performing determination, or a part of the signal processing unit 130 or another unit (not illustrated) has a function of performing determination. It may be. The imaging unit 100 is initializing the sensor S in any row based on the drive signal TX from the drive unit 120 or the control signal from the control unit 160 and the detection signal from the detection unit 150. There may be further provided means for holding information on whether the detection signal has been output. Based on the information, the unit that performs the determination specifies the row that is the initialization target when the detection signal is output, and compares the signal value between the specified row and the other rows. And making a determination based on the difference between them.

  FIG. 4 shows an operation flowchart of the apparatus IA. In step S001 (hereinafter simply referred to as “S001”. The same applies to other steps), the above-described initialization operation RS is performed.

In S002, it is determined whether or not radiation irradiation has started. If radiation irradiation has not started, the process returns to S001, and if radiation irradiation has started, the process proceeds to S003. Specifically, the detection unit 150 monitors the current amount I _S of the bias line V _S and determines that radiation irradiation has started when the current amount I _S becomes larger than the threshold value I _TH. Then, a detection signal is output. When the detection signal is not output, the process returns to S001, and when the detection signal is output, the process proceeds to S003.

  In S003, the above-described accumulation operation AO is performed. The accumulation operation AO may be performed until the radiation irradiation is completed, but may be forcibly terminated when the radiation irradiation is not terminated even after a predetermined time has elapsed. Thereafter, in S004, the aforementioned read operation RO is performed.

In S005, the above-described dark image reading is performed. Specifically, the initialization operation RS _F , the accumulation operation AO _F, and the read operation RO _F are performed in the same manner as the operations RS, AO, and RO (S001, S003, and S004). Thereafter, correction processing is performed on the image data obtained in the read operation RO in S004 using the dark image data obtained in this step.

  In S006, the above-described determination, that is, whether or not the level of the noise in the step in the radiation image is acceptable (hereinafter referred to as “determination D1”) is performed. As a result of the determination D1, if it is determined that the level of the noise of the step is not permitted, the process proceeds to S007, and if it is determined that the level is acceptable, the radiography is terminated.

  In S007, the user is notified that the level of the noise in the step in the radiographic image is not allowed (hereinafter referred to as “notification N1”), and the radiographic imaging is terminated. The user can perform re-shooting based on the notification N1. Further, the user can confirm the radiographic image as necessary, and re-imaging may not be performed depending on the result of the confirmation.

As described above, according to the driving method or the control method, the apparatus IA analyzes the image data obtained by the reading operations RO and RO _F and determines whether or not the level of the noise in the step in the radiation image is acceptable. D1 is performed. The determination D1 can be made based on the difference between the signal value of the row to be initialized when the detection signal is output and the signal value of the other rows. If the level of the noise at the step is not acceptable, the device IA can notify the user of the determination result N1 and prompt the user to re-shoot. Therefore, it is not necessary for the user to check the radiation image every time radiography is performed. Therefore, according to the present embodiment, it is possible to determine whether or not the level of noise appearing in the radiographic image is within an allowable range with the radiographic imaging device, which is advantageous for reducing the burden on the user, and It is also advantageous to reduce the burden on the user.

(Second Embodiment)
When the predetermined data processing is performed on the image data, the determination criterion of the above-described determination D1 may be changed according to the content of the data processing. In the second embodiment, determination D1 in the case where correction processing for compensating the above-described signal value difference A is performed on the image data obtained by the read operations RO and RO _F will be described.

  For example, the sensor signal may include a noise component due to random noise in addition to a signal component corresponding to the radiation dose. The random noise is generated due to heat or the like due to driving of the sensor S and other circuits, and causes noise to the sensor S and may also cause noise to other sensors S. Specifically, when a random noise occurs in a certain sensor S, the sensor signal of the sensor S and the sensor signal of the adjacent sensor S or the sensor S in the vicinity thereof may contain the same level of noise components. . In this case, the signal component is corrected and the noise component is also corrected by performing the correction process for compensating for the signal value difference A described above. For this reason, in the radiographic image based on the image data that has been subjected to the correction process, noise of another step due to the corrected noise component (hereinafter, simply referred to as “other step noise”) may appear. End up.

  Therefore, in the present embodiment, when the correction process is performed, the determination criterion of the above-described determination D1 is changed. For example, when the ratio A / D is smaller than 30%, it is determined that other step noise is allowed. When the ratio A / D is larger than 30%, other step noise is present. Judged as unacceptable. Thereby, when correction processing is performed on the image data thereafter, it is appropriately determined whether or not the noise level of other steps that may occur in the radiographic image based on the image data is acceptable. Can do.

In this embodiment, as a result of performing the correction process on the image data obtained by the read operations RO and RO _F , the signal component is corrected and the noise component caused by random noise or the like is corrected. The case where noise occurs is described. However, the present invention is not limited to the case where the above correction processing is performed, and can also be applied to the case where correction processing such as shading correction or other data processing is performed. That is, when predetermined data processing is performed on the image data obtained by the read operations RO and RO _F , the determination criterion of the determination D1 may be appropriately changed according to the contents of the data processing. Thus, the present embodiment can provide the same effects as those of the first embodiment described above.

(Third embodiment)
In the first embodiment described above, the case where the radiation is uniformly incident on the imaging unit 100 has been considered for ease of explanation. However, when actually performing radiography, the radiation incident on the imaging unit 100 includes in-vivo information of the subject and is not uniform. In addition, when performing radiography a plurality of times, such as in the continuous imaging mode, the row to be initialized when the start of radiation irradiation is detected may be different for each radiography. That is, the initialization operation RS is interrupted when the sensor S in which row is being initialized may be different in each radiography. Therefore, even if each time of radiography is performed under the same imaging conditions, the result of the determination D1 may be different in each time of radiography.

  For example, consider a case where the determination D1 is performed based on whether the above-described ratio A / D is larger or smaller than a predetermined reference value. In this case, for example, when the signal value of the row to be initialized or the next row when the radiation start is detected in a certain radiography, the radiation value is relatively larger than the signal value difference A. It can be determined that the level of noise in the step in the image is acceptable. On the other hand, in other times of radiography, when the signal value of the row to be initialized when detecting the start of radiation irradiation or the signal value of the next row is relatively smaller than the signal value difference A, It can be determined that the noise level of the step is not acceptable.

  Therefore, in the third embodiment, determination D1 and other determinations when performing multiple times of radiography such as continuous imaging mode will be described. Hereinafter, this embodiment will be described with reference to FIGS.

5A and 5B illustrate signal values or average values of data values for each row of image data including in-vivo information of the subject for each row. In the drawing, for example, a region R1 corresponds to a radiation irradiation region, and a region R2 corresponds to a radiation non-irradiation region. Of the region R1, the region R _ob corresponds to a region where the radiation is detected through the subject, and the region R _em corresponds to a region where the radiation is detected without passing through the subject. In addition, each area | region R1 etc. in a figure is not restricted to the said aspect, The area | region R2 may not exist depending on the imaging | photography method, and area | region Rem may not exist depending on the site _| part to be examined.

The apparatus IA may further include a specifying unit that specifies which region in the image data is the region R1 or the like. For example, a region where the signal value is smaller than a predetermined minimum value is specified as a region R2, and the other region is specified as a region R1, and among the regions R1, a region where the signal value is larger than a predetermined maximum value is specified. It is also possible to specify the region R _em and specify the other region as the region R _ob .

In the example of FIG. 5A, in the region R _ob , the signal value of the row to be initialized when the start of radiation irradiation is detected is relatively large, that is, the start of irradiation is detected at a row where the radiation dose is large. It has been shown. At K1 in the figure, there is a difference A ′ between the signal value of the row to be initialized and the signal value D1 ′ of the next row. In this example, the ratio A ′ / D1 ′ is smaller than the predetermined reference value, and it can be determined that the level of the noise of the step in the radiographic image is allowed.

In the example of FIG. 5B, in the region _Rob , the signal value of the row to be initialized when the start of radiation irradiation is detected is relatively small, that is, the start of irradiation is detected in the row where the radiation dose is small. It has been shown. At K2 in the figure, there is a difference A ′ between the signal value of the row to be initialized and the signal value D2 ′ of the next row. In this example, the ratio A ′ / D2 ′ is smaller than the predetermined reference value, and it can be determined that the level of the noise of the step in the radiographic image is allowed.

Here, as described in the first embodiment, if the threshold value I _TH for detecting the start of radiation irradiation is a fixed value, the signal value difference A ′ is substantially constant. This is the same even when the radiation dose or radiation intensity is different. That is, the signal value difference A ′ in FIG. 5A and the signal value difference A ′ in FIG. 5B are substantially equal to each other. This will be described with reference to FIG.

FIG. 6A shows an operation timing chart in the case where the radiation dose is one-half that of the example of the first embodiment (see FIG. 3A), and FIG. The signal value or the average value of the data values in each row in the image data in that case is shown for each row. If the radiation dose of one-half the rate of increase of the current amount I _S becomes one half substantially for the example of the first embodiment (see Figure 3 (b)). Therefore, if the threshold value I _TH is a fixed value, the delay in detecting the start of radiation irradiation by the detection unit 150 is approximately twice that of the example of the first embodiment. As a result, the row to be initialized when the start of radiation irradiation is detected is the fifth row in the example of the first embodiment, while the seventh row in the example of FIG. It has become.

That is, if the threshold value I _TH is a fixed value, when the radiation dose or radiation intensity is different, the detection delay is different, but the signal value difference A ′ is substantially constant. Here, in order to distinguish from the example of the first embodiment, the signal value difference is indicated as “A ′”, but the signal value differences A and A ′ are substantially equal to each other.

  Referring to FIG. 5 again, the example of FIG. 5A in which the irradiation start is detected in a row with a large radiation dose, and the example of FIG. 5B in which the irradiation start is detected in a row with a small radiation dose. In both cases, the signal values D1 ′ and D2 ′ are different from each other, but in each example, a signal value difference A ′ is generated. Therefore, in the example of FIG. 5A, the ratio A ′ / D1 ′ is smaller than the predetermined reference value, and in the example of FIG. 5B, the ratio A ′ / D2 ′ is lower than the predetermined reference value. Increases, the results of determination D1 in these examples differ from each other. That is, even if it is determined that the level of the level difference noise in the image data is acceptable in the determination D1 in one radiography, the level difference in the image data is determined in the determination D1 in the next radiography. It may be determined that the noise level is not acceptable.

  In the present embodiment, in addition to performing the determination D1 in a certain radiography, and further performing another radiography, the determination D1 in the other radiography may determine that the noise of the step is not allowed. The second determination of whether or not there is further is performed (hereinafter referred to as “determination D2”).

  FIG. 7 shows an operation flowchart according to the present embodiment. In the figure, steps having the same contents as those in FIG. That is, S001 to S007 are the same as those in FIG.

  If it is determined by the determination D1 in S006 that the level of the noise of the step is not permitted, the process proceeds to S007, and if it is determined to be permitted, the process proceeds to S009.

  In S007, notification N1 is performed. As a result of determination D1, specifically, the user is notified that the level of noise in the step in the radiographic image is not allowed, and the process proceeds to S008.

  In S008, the radiography is terminated by notifying the user of imaging condition candidates (hereinafter referred to as “notification N2”) that can be determined that the step noise is allowed in the determination D1. The candidate may be notified using the display unit 60 or other display means or notification means as described in the first embodiment. The candidates may include candidates such as the irradiation amount or intensity of the radiation to be irradiated, the irradiation time, the sensitivity to be set by the detection unit 150, and the like. The candidate can be calculated based on, for example, the ratio A ′ / D ′, the signal value D ′, and other image data information.

In S009, determination D2, that is, whether or not there is a possibility that the noise of the step may be determined to be unacceptable in determination D1 in the other radiation imaging when another radiation imaging is further performed. I do. If there is a possibility that the noise of the step is not allowed, the process proceeds to S010, and if not, the radiation imaging is terminated. In the example of FIG. 5, the determination D _<b > 2 may be made based on the smallest signal value in the region R _ob and the signal value difference A ′, that is, the ratio A ′ / D ′ is smallest. It may be done paying attention to the part.

  In S010, as a result of the determination D2, specifically, when the other radiation imaging is further performed, it may be determined that the noise of the step is not allowed in the determination D1 in the other radiation imaging. To the user (hereinafter referred to as “notification N3”), the process proceeds to S011.

In S011, the user is notified of imaging condition candidates that can be determined that the noise of the step is allowed in the determination D1 in the other radiation imaging when the other radiation imaging is further performed (hereinafter, “ Notification N4 ”), and the radiation imaging is terminated. The candidate may be notified using the display unit 60 or other display means or notification means. The candidates may include candidates such as the irradiation amount or intensity of the radiation to be irradiated, the irradiation time, the sensitivity to be set by the detection unit 150, and the like. The candidates can be calculated based on, for example, the ratio A ′ / D ′, the signal value D ′, and other image data information. Specifically, in the example of FIG. 5, it may be calculated based on the smallest signal value in the region R _ob and the signal value difference A ′, that is, the ratio A ′ / D ′ is the smallest. What is necessary is just to calculate paying attention to the part which becomes.

  As described above, according to the present driving method or control method, the apparatus IA determines the level of the noise of the step in the determination D1 in the case where another radiography is further performed based on the image data obtained by one radiography. A determination D2 is made as to whether or not there is a possibility of being determined to be unacceptable. The apparatus IA notifies the user of more suitable imaging condition candidates when there is a possibility that the noise level of the step is not allowed in the other radiation imaging. Therefore, according to the present embodiment, the same effects as those of the first embodiment described above can be obtained, and, for example, it is possible to prevent redoing of radiography, which is advantageous for further reducing the burden on the user and the subject. It is.

(program)
The embodiments described above can also be achieved by executing the program or software by a computer. Specifically, for example, a program that realizes the functions of the above-described embodiments is supplied to the system or apparatus via a network or various storage media. The computer of the system or apparatus (or CPU, MPU, etc.) then reads and executes the program.

(Other)
As mentioned above, although some suitable embodiment was illustrated, this invention is not limited to these, The part may be changed according to the objective etc., Each feature of each embodiment is combined. May be. For example, each function of two or more units may be achieved by one unit, some functions of a unit may be achieved by other units, and the configuration of each unit depends on the purpose, etc. It may be changed as appropriate.

  IA: radiation imaging apparatus, 50: arithmetic processing unit, 120: drive unit, 130: signal processing unit, 131: reading unit, 132: AD conversion unit, 133: data generation unit, 140: voltage generation unit, 150: detection unit 160: Control unit.

Claims (14)

A plurality of sensors arranged so as to form a plurality of rows and a plurality of columns, a drive unit that drives the plurality of sensors in units of rows, and detection of the start of radiation irradiation to the plurality of sensors A radiation imaging apparatus including a detection unit and a control unit,
The controller is
A first control for controlling the drive unit to repeatedly initialize the plurality of sensors in units of rows before the detection unit detects that radiation irradiation has started;
A second control for controlling the drive unit so as to interrupt the initialization in response to the detection unit detecting that radiation irradiation has started and to output signals from the plurality of sensors; Done
Among the signals from the plurality of sensors output by the second control, the radiation imaging apparatus includes a signal from a sensor in a row last initialized by the first control, and a sensor from other rows. A radiation imaging apparatus, further comprising: a unit that determines whether or not signals from the plurality of sensors output by the second control meet a predetermined reference based on a difference from the first signal. The unit performs the determination based on a difference between an average value of signals from sensors in the last initialized row and an average value of signals from sensors in other rows. The radiation imaging apparatus according to 1. The control unit is configured to output signals corresponding to the charges generated by the plurality of sensors in a state where the plurality of sensors are not irradiated with radiation before or after the first control and the second control. Further performing a third control for controlling the driving unit to output,
The radiation imaging apparatus includes: an output unit configured to output, as image data, a difference between signals from the plurality of sensors output by the second control and signals from the plurality of sensors output by the third control. The radiation imaging apparatus according to claim 1, further comprising: The unit performs other imaging based on the difference between the signal from the plurality of sensors output by the second control according to the radiation passing through the subject and the smallest signal value, and the difference. 4. It is further determined whether or not there is a possibility that signals from the plurality of sensors obtained by the other photographing do not meet the predetermined reference when the step is further performed. The radiation imaging apparatus according to any one of the above. The radiation imaging apparatus according to claim 1, further comprising a notification unit that notifies a user of a result of determination by the unit. The notification unit further notifies a candidate of an imaging condition in which signals from the plurality of sensors obtained by the other imaging satisfy the predetermined reference when another imaging is further performed. 5. The radiation imaging apparatus according to 5. The notifying unit may be a candidate for a radiation dose and a candidate for a radiation time for which a signal from the plurality of sensors obtained by the other photography when the other photography is performed satisfies the predetermined reference. The radiation imaging apparatus according to claim 5, wherein at least one is further notified. The radiation imaging apparatus according to claim 1, wherein the notification unit includes a display unit for displaying a radiographic image. The radiation imaging apparatus according to claim 1, further comprising a radiation source that generates radiation. A method for controlling a radiation imaging apparatus, comprising:
The radiation imaging apparatus includes a plurality of sensors arranged to form a plurality of rows and a plurality of columns, and a detection unit that detects that radiation irradiation to the plurality of sensors has started. And
The method for controlling the radiation imaging apparatus includes:
A first step of repeatedly initializing the plurality of sensors in units of rows until the detection unit detects that radiation irradiation has started;
A second step of driving the plurality of sensors such that the initialization is interrupted in response to the detection by the detection unit detecting that radiation irradiation has started, and the plurality of sensors output signals;
Of the signals from the plurality of sensors output in the second step, the difference between the signal from the sensor in the row last initialized in the first step and the signal from the sensor in the other row A third step of determining whether or not the signals from the plurality of sensors output in the second step meet a predetermined reference;
A control method for a radiation imaging apparatus, comprising: Other imaging was further performed based on the difference between the signal from the plurality of sensors output in the second step and the radiation having passed through the subject and having the smallest signal value, and the difference. 11. The method according to claim 10, further comprising a fourth step of further determining whether or not signals from the plurality of sensors obtained by the other photographing sometimes do not meet the predetermined reference. A control method of the radiation imaging apparatus described. In the fourth step, when another shooting is further performed, signals from the plurality of sensors obtained by the other shooting notify a candidate of shooting conditions satisfying the predetermined reference. The method of controlling a radiation imaging apparatus according to claim 11. In the fourth step, when the other imaging is further performed, a signal from the plurality of sensors obtained by the other imaging satisfies the radiation dose candidate satisfying the predetermined reference and the radiation irradiation time. The method of controlling a radiation imaging apparatus according to claim 11 or 12, wherein at least one of the candidates is notified.   The program for making a computer perform each process of the control method of any one of Claims 10 thru | or 13.

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