JP6552306B2 - Radiation imaging apparatus, radiation imaging system, and method using radiation imaging apparatus - Google Patents

Description

  The present invention relates to a radiation imaging apparatus, a radiation imaging system, and a method using a radiation imaging apparatus.

  At present, radiation imaging apparatuses using a flat panel detector (hereinafter abbreviated as FPD) made of a semiconductor material are widely used as imaging apparatuses used for medical image diagnosis and nondestructive inspection using radiation. Such a radiation imaging apparatus is used as a digital imaging apparatus for still image shooting such as general shooting or moving image shooting such as fluoroscopic shooting in medical image diagnosis, for example.

  Some radiation imaging devices monitor the radiation dose and terminate the radiation when the radiation dose reaches a target value (for example, output a signal for stopping the radiation to the radiation source) There is something to do. This operation is called automatic exposure control (Automatic Exposure Control (AEC)), and can prevent, for example, excessive irradiation of radiation.

  As such a radiation imaging apparatus, for example, Patent Document 1 discloses a radiation imaging apparatus including a detection pixel for detecting an irradiation dose of the radiation in a detector that outputs an image signal corresponding to the radiation. There is. In this patent document 1, a radiation detection signal indicating that the irradiation dose of radiation has reached a predetermined value or more is generated based on the signal from the detection pixel, and the radiation detection signal from the radiation source is generated based on the generated radiation detection signal. The timing of stopping radiation irradiation is controlled.

JP, 2014-071034, A

However, in Patent Document 1, there is a problem in the accuracy of detection of the radiation dose and the accuracy of control of the radiation source based thereon. The radiation emitted from the radiation source may not be stopped instantaneously even if a stop instruction is received. In such a case, due to the delay component of the radiation stop with respect to the stop instruction, the radiation dose of radiation actually irradiated to the radiation imaging apparatus becomes larger than the radiation dose of radiation at the timing when the radiation detection signal is generated. .
Therefore, an object of the present invention is to provide a radiation imaging apparatus capable of detecting the radiation dose with higher accuracy.

  A radiation imaging apparatus according to the present invention calculates a radiation amount of radiation irradiated to the pixel array, and a pixel array including a plurality of pixels for outputting an image signal according to the radiation emitted from the radiation generation device. An output unit that outputs a signal for the output, a calculation unit that calculates an error caused by the falling waveform of the data based on a rising waveform of the data indicating the waveform of the signal output from the output unit, and the calculation unit A control unit that controls a timing of outputting a control signal for requesting the radiation generation apparatus to stop emission of radiation based on the calculated error.

  According to the present invention, it is possible to provide a radiation imaging apparatus capable of detecting the radiation dose with higher accuracy.

Schematic block diagram of a radiation imaging system Schematic equivalent circuit diagram for explaining a detector, and schematic cross-sectional view of a pixel included in a pixel array of the detector Timing chart for explaining the operation of the detector Time variation characteristic showing variation with time of output of radiation emitted from radiation generator, and time variation characteristic of signal output from dose pixel Time variation characteristics of the signal output from the dose pixel, and time variation characteristics of the integrated value of the signal output from the dose pixel Flowchart for explaining processing for calculating radiation dose Time variation characteristics of the signal output from the dose pixel and the integrated value of the signal

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The radiation may typically be X-rays, but may be α rays, β rays, γ rays, or the like.

  First, the radiation imaging system will be described with reference to FIG. FIG. 1 is a schematic block diagram of a radiation imaging system.

  The radiation imaging system can include an imaging device 100, a control computer 109, a radiation control device 110, a radiation generation device 111, and a display unit 114. The imaging apparatus 100 can include a detector 104, a signal processing unit 105, a control unit 106, and a communication unit 107. The detector 104 includes a pixel array 101 having a plurality of pixels that convert radiation or light into an electrical signal, a drive circuit 102 that drives the pixel array 101, and an electrical signal from the driven pixel array 101 is output as an image signal. And the read out circuit 103. An example of the detector 104 will be described later in detail with reference to FIGS. 2 (a) and 2 (b). The signal processing unit 105 can include a calculation unit 116 for calculating the irradiation dose of the radiation irradiated on the detector 104. The control computer 109 can include a communication unit 108 and a control console 115. The radiation generator 111 may include a radiation source 112 and an irradiation field stop mechanism 113.

  The control computer 109 gives control signals to the imaging apparatus 100 and the radiation control apparatus 110 based on imaging information input from a photographer (not shown) via the control console 115 of the control computer 109. The radiation control device 109 receives a control signal from the control computer 109 and controls the operation of emitting radiation from the radiation source 112 of the radiation generation device 111 and the operation of the irradiation field stop mechanism 113. The control unit 106 of the imaging apparatus 100 receives a control signal from the control computer and controls each part of the imaging apparatus 100. In response to the radiation emitted from the radiation generation device 110 controlled by the radiation control device 110, the detector 104 of the imaging device 100 outputs an image signal corresponding to the radiation. The output image signal is subjected to image processing such as offset correction by the signal processing unit 105 and then transmitted to the control computer 109 via the communication unit 107 and the communication unit 108. Here, known wireless communication and wired communication may be applied to the communication unit 107 and the communication unit 108. The transmitted image signal can be displayed on the display unit 114 after necessary image processing is performed by the control computer 109.

  Next, an example of the detector 104 will be described using FIGS. 2 (a) and 2 (b). 2A is a schematic equivalent circuit diagram for explaining the detector 104, and FIG. 2B is a schematic cross-sectional view of pixels included in the pixel array 101 of the detector 104. 2A shows the detector 104 having m rows × n columns of pixels for ease of explanation. However, the actual imaging device has more pixels, for example, a 17-inch imaging device has about 2800 rows by about 2800 columns of pixels.

  The pixel array 101 has a plurality of pixels arranged in a matrix. Each pixel includes a conversion element 201 that converts radiation into an electrical signal, and a switch element 202 that outputs the electrical signal. In this embodiment, as a conversion element, as shown in FIG. 2B, an indirect type conversion in which a wavelength converter 223 for converting radiation into light and a photoelectric conversion element 201 ′ for converting light into electric charge are combined. Elements can be used. Note that the wavelength converter 223 can be disposed above the photoelectric conversion element 201 ′ via the interlayer insulating layer 222. As the photoelectric conversion element 201 ′, a PIN type photodiode which is disposed on an insulating substrate such as a glass substrate and is mainly made of amorphous silicon is used. The photoelectric conversion element 201 ′ can include an individual electrode 217, an n-type impurity semiconductor layer 218, an intrinsic semiconductor layer 219, a p-type impurity semiconductor layer 220, and a counter electrode 221. Note that as the conversion element, a direct type conversion element that converts radiation directly into charge may be used. As the switch element 202, a transistor having a control terminal and two main terminals is preferably used, and a thin film transistor (TFT) is used in this embodiment. As shown in FIG. 2B, a TFT having an amorphous silicon as a main material, which is disposed on an insulating substrate such as a glass substrate, is used as the switch element. The switch element 202 can include a gate electrode 211 serving as a control terminal, a gate insulating layer 212, an intrinsic semiconductor layer 213, an n-type impurity semiconductor layer 214, and a source or drain electrode 215 serving as two main terminals. The individual electrode 217, which is one electrode of the conversion element 201, can be electrically connected to one of the two main terminals of the switch element 202 through a through hole in the interlayer insulating layer 216. The other electrode of the conversion element 201 is electrically connected to the bias power source 116 via the common bias wiring Bs. The other of the two main terminals of the plurality of switch elements 202 can be electrically connected to the readout circuit 103 via the plurality of signal wirings Sig1 to Sign.

  Here, the plurality of pixels of the pixel array 101 according to the present embodiment calculate the irradiation dose of the radiation irradiated to the pixel array 101 and the imaging pixel P1 outputting a signal for becoming an image signal according to the radiation. A dose pixel P2 that outputs a signal for The signal output from the dose pixel P2 can also be used as a signal to be an image signal. The control terminals of the switch elements 202 of the plurality of imaging pixels P1 can be electrically connected to the imaging drive circuit 102a included in the drive circuit 102 via the plurality of imaging drive wirings G1 to Gm. The drive circuit 102a for imaging is for driving the imaging pixel P1. On the other hand, the control terminals of the switch elements 202 of the plurality of dose pixels P2 can be electrically connected to the dose drive circuit 102b included in the drive circuit 102 via the plurality of detection drive wirings G1 ′ to Gm ′. . The dose drive circuit 102a is for driving the dose pixel P1. Here, the imaging drive circuit 102a and the detection drive circuit 102b can operate independently or in synchronization with each other by a control signal that can be input thereto.

  The readout circuit 103 is for reading out electric signals output in parallel from the pixel array 101, and provided with amplification circuits 203 for amplifying the electric signals output in parallel from the pixel array 101 corresponding to each signal wiring. ing. Each amplifier circuit 203 includes an integrating amplifier 207 that amplifies the output electric signal, a variable amplifier 204 that amplifies the electric signal from the integrating amplifier 207, and a sample hold circuit 205 that samples and holds the amplified electric signal. And a buffer amplifier 206. The integrating amplifier 207 has an operational amplifier that amplifies and outputs the read electric signal, an integrating capacitor, and a reset switch. The integral amplifier 207 can change the amplification factor by changing the value of the integral capacitance. The output electric signal is input to the inverting input terminal of the operational amplifier 105, the reference voltage Vref is input from the reference power supply 107b to the normal input terminal, and the amplified electric signal is output from the output terminal. Also, an integrating capacitance is disposed between the inverting input terminal and the output terminal of the operational amplifier. The sample and hold circuit 205 is provided corresponding to each amplifier circuit, and is configured of a sampling switch and a sampling capacitor. Further, the readout circuit 103 sequentially outputs the electric signals read out in parallel from the respective amplification circuits 203 and outputs it as an image signal of a serial signal, a buffer amplifier 209 which converts the impedance of the image signal and outputs it. Have. The analog image signal Vout output from the buffer amplifier 209 is converted into a digital image signal ADOUT by the A / D converter 210 and output to the signal processing unit 105 shown in FIG. The power supply unit (not shown) includes a reference power supply 107 b of the amplification circuit 203 and a bias power supply 116. The reference power supply 107 b supplies the reference voltage Vref to the non-inverting input terminal of each operational amplifier. The bias power supply 116 supplies a bias voltage Vs in common to the other electrode of each conversion element via the bias wiring Bs, so that the conversion element can convert radiation into electric charge.

  The imaging drive circuit 102a sets the switch element 202 in a conductive state and a non-conductive state in accordance with control signals (D-CLK, OE, DIO) input from the control unit 106 shown in FIG. A drive signal having a non-conduction voltage is output to each of the drive wirings G1 to Gm. In addition, the detection drive circuit 102b sends a drive signal having a conduction voltage and a non-conduction voltage in response to the control signals (D-CLK ′, OE ′, DIO ′) input from the control unit 106 to each drive wiring G1. Output to '~ Gm'. As a result, the drive circuit 102 drives the detection unit 101. Here, the control signals D-CLK and D-CLK ′ are shift clocks of each shift register used as a drive circuit. Control signals DIO and DIO 'are pulses transferred by each shift register, and OE and OE' are signals for controlling the output terminal of each shift register. Thus, the required drive time and the scanning direction are set. In addition, the control unit 106 controls the operation of each component of the reading circuit 103 by giving the reading circuit 103 a control signal RC, a control signal SH, and a control signal CLK. Here, the control signal RC indicates the operation of the reset switch of the integrating amplifier, the control signal SH indicates the operation of the sample hold circuit 205, the control signal CLK indicates the operation of the multiplexer 208, and the control signal ADCLK indicates the operation of the A / D converter 210. It is to control. In the present embodiment, the output unit of the present invention includes a plurality of dose pixels P2, a plurality of detection drive wirings G1 ′ to Gm ′, a detection drive circuit 102b, and a readout circuit 103, and irradiates the pixel array 101. Output a signal for calculating the radiation dose of the radiation.

  Next, an automatic exposure control (Automatic Exposure Control (AEC)) operation in this embodiment will be described with reference to FIG. FIG. 3 is a timing chart for explaining the operation of the detector 104. Here, FIG. 3 shows an example for a pixel array 101 of a 3 × 3 matrix of m = 3 and n = 3, and Vg1 to Vg3 are drive signals supplied to the imaging drive wirings G1 to G3, Vg1 ′ to Vg3 'is a drive signal supplied to the detection drive wirings G1' to G3 '.

  When the bias voltage Vs is supplied to the conversion element 201 at time t11, the detector 104 starts an idling operation. This idling operation is an operation for reducing the dark current that can be generated in the conversion element 201 by repeatedly performing an initialization operation for sequentially turning on the switch elements 202 of each pixel in units of rows. In the idling operation, the control unit 106 controls the drive circuit 102 to repeatedly perform the initialization operation during a period (t11 to t12) until time t12 when a signal (exposure signal) for informing the start of radiation exposure is detected. Note that during this period, the control unit 106 may control the reading circuit 103 to suppress heat generation and power consumption of the reading circuit 103 when it is not necessary to output an image signal. At this time, it is preferable to suppress the drift of the output due to the input offset current of the integrating amplifier 207 by turning on the reset switch of the integrating amplifier 207.

  When the exposure signal is detected at time t12, the supply of the conduction voltage by the imaging drive circuit 102a is stopped, and the switch elements 202 of the plurality of imaging pixels P1 are maintained in the non-conduction state. This operation is called an accumulation operation. When radiation is irradiated to the detector 104 during the accumulation operation (accumulation period), an electrical signal corresponding to the irradiated radiation can be accumulated in the imaging pixel P1. On the other hand, the detection drive circuit 102b sequentially outputs the signal of the dose pixel P2 by sequentially supplying the conduction voltage in units of rows. At this time, the control unit 106 controls the reading circuit 103 so that a signal obtained for calculating the radiation dose based on the signal input by the reading circuit 103 can be output. In the present embodiment, an offset reading operation for obtaining a signal corresponding to the offset component of the dose pixel P2 is performed between times t12 and t13. The signal output by this offset reading operation can be used for offset correction of the signal output from the dose pixel P2. Then, during time t13 to t14, the detection drive circuit 102b sequentially supplies the conduction voltage to the switch elements 202 of the dose pixels P2 in units of rows, thereby detecting the signals of the dose pixels P2 sequentially in units of rows. A signal read operation is performed. The signal output from the dose pixel P2 is output via the readout circuit 103 and can be a signal obtained for calculating the radiation dose. The calculation unit 116 can calculate the irradiation dose of the radiation irradiated to the detector 104 by, for example, integrating this signal. The signal processing unit 105 determines, based on the irradiation dose calculated by the calculation unit 116, whether the appropriate irradiation dose has been achieved. The control unit 106 controls the detector 104 and the signal processing unit 105 so that the detection signal reading operation and the calculation are repeated until it is determined that the appropriate irradiation dose has been reached. When it is determined by the signal processing unit 105 that an appropriate irradiation dose has been obtained, the control unit 106 controls the radiation control device 110 via the control computer 109 to stop emitting radiation by the radiation generation device 111. Control signal to output the The determination will be described later in detail. This detection signal read operation, calculation, and determination are referred to as AEC operation. In the present example, the calculation unit 116 may be included in the signal processing unit 105. Further, the above determination may be made by the calculation unit 116.

  After the AEC operation, between time t14 and t15, a signal that becomes an image signal corresponding to the radiation irradiated during the accumulation operation is output from the plurality of imaging pixels P1 by a known method. An image signal may be output from the detector 104 through.

  Here, with reference to FIG. 4A and FIG. 4B, the principle of the present invention will be described. FIG. 4A shows a time fluctuation characteristic indicating the fluctuation of the output of the radiation emitted from the radiation generator 111 with respect to time, and FIG. 4B shows a time fluctuation characteristic of the signal output from the dose pixel P2. In the present specification, the variation with time of the output is referred to as a waveform. Note that this output may be the output of one dose pixel P2 or the average of the outputs of a plurality of dose pixels P2.

  The radiation emitted from the radiation generator 111 is ideally emitted in the form of a so-called rectangular wave that rises instantaneously when extraction is started and falls instantaneously upon completion of extraction. . However, in practice, as shown in FIG. 4A, the rise and fall are not instantaneously caused by various factors, and a certain amount of time is required until the desired output is reached at the rise and fall. It often takes time and delays. Moreover, such a delay may differ for every radiation generator. As shown in FIG. 4A, the rising delay time Ta of the radiation a emitted from one radiation generating device and the rising delay time Tb of the radiation b emitted from another radiation generating device are different. Can happen. The same applies to falling delay times Ta 'and Ta'. When such a delay occurs, for example, the rising delay Ta can be calculated by the calculation unit 116 during the AEC operation. However, for the fall, if the irradiation dose is calculated based only on the signal obtained by the calculation unit 116 in the AEC operation, the radiation portion irradiated to the detection unit 104 during the fall delay time Ta ′ It becomes an error.

  Therefore, the inventor of the present application found that there is a correlation between the rising and falling of the waveform of the radiation as a result of the sincerity examination. That is, the falling waveform of the data indicating the radiation waveform is calculated based on the rising waveform of the data indicating the radiation waveform, the value corresponding to the error is calculated based on the calculated falling waveform, and the calculated It was found that the value could be used to calculate more appropriate radiation dose. When the calculation unit 116 performs such calculation, it is possible to calculate a more appropriate irradiation dose in which an error caused by the fall delay time is suppressed.

  For example, when using an indirect type conversion element as the conversion element, it is desirable to consider the conversion characteristics of the wavelength converter. As shown in FIG. 4B, even when the same radiation is irradiated, time variation characteristics such as emission start and afterglow characteristics may differ depending on the type of wavelength converter. In FIG. 4 (b), as a representative example of the wavelength converter, time-varying characteristics of thallium activated cesium iodide (CsI: Tl) and gadolinium oxysulfide (GOS) are shown. Here, the delay time of the rise (start of light emission) of CsI: Tl is Tc, the delay time of the fall (afterglow) of CsI: Tl is Tc ′, the delay time of the rise (start of light emission) of GOS is Tg, The delay time of falling (afterglow) is set to Tg '. Even when such a delay occurs, for example, the rising delay Tc can be calculated by the calculation unit 116 during the AEC operation. However, for the fall, if the irradiation dose is calculated based only on the signal obtained by the calculation unit 116 in the AEC operation, the amount of afterglow irradiated to the detection unit 104 during the fall delay time Tc ′. Is an error. Therefore, the inventor of the present application has found that there is a correlation between the rise and fall of the light emission waveform of the wavelength converter as a result of the sincerity examination. That is, in the indirect radiation imaging apparatus, it has been found that the rising waveform of the output from the pixel includes the delay of the rising of the radiation and the delay of the light emission of the wavelength converter. However, this is not limited to the indirect type conversion element. For example, even a direct type conversion element may occur depending on the conversion characteristics of the conversion element. That is, it has been found that there is a correlation between rising and falling of the conversion characteristics of the conversion element.

  Therefore, the inventor of the present application calculated an error caused by the falling waveform of the data indicating the waveform of the signal output from the output unit based on the data indicating the rising waveform of the signal output from the output unit, and was calculated It has been found that the error can be used to calculate a more appropriate radiation dose. When the calculation unit 116 performs such a calculation, it is possible to calculate a more appropriate irradiation dose in which the error of the irradiation dose is suppressed. Especially for radiation imaging devices that use indirect type conversion elements, more appropriate irradiation doses with reduced radiation dose errors, taking into account the delay time of the radiation converter and the delay time of the wavelength converter. It becomes possible to calculate The irradiation dose calculated in this way may be used as data for managing the exposure dose of the subject, for example. Further, when the irradiation dose calculated in this way is used for AEC, the output timing of the control signal for requesting stop of radiation emission by the radiation generator 111 output from the control unit 106 is adjusted. That is, the control unit 106 controls the timing of outputting a control signal for requesting the radiation generation apparatus 111 to stop emitting radiation based on the calculated error.

  Next, the calculation method by the calculation unit 116 will be described using FIGS. 5 (a) and 5 (b). 5 (a) shows the time variation characteristic of the signal output from the dose pixel P2 for explaining the calculation method by the calculation unit 116, and FIG. 5 (b) shows the time of the integrated value of the signal output from the dose pixel P2. It is a fluctuation characteristic.

  The waveform of radiation applied to the pixel array 101 is ideally a rectangular wave y (t), and the integrated value Y (t) increases in proportion to time. In the case of an ideal rectangular wave, the calculation unit 116 calculates an integrated value obtained by integrating the signals output from the dose pixels P2, and compares the threshold B, which is an appropriate dose index, with the integrated value. When the integrated value reaches the threshold value B, the calculation unit 116 determines that the radiation irradiated to the pixel array 101 has reached an appropriate dose. Based on the determination, the control unit 106 transmits an exposure stop signal to the radiation control device 110, and the radiation generation device 111 stops the radiation generation by the radiation generation device 112. If the radiation emitted at time t0 is an ideal rectangular wave, the integrated value calculated by the calculation unit 116 at time t2 is equal to the dose emitted to the pixel array 101. However, in practice, as shown in FIG. 5A, the waveform of the radiation applied to the pixel array 101 is delayed as indicated by the waveform x (t) of the signal output from the output unit. The waveform of the radiation applied to the pixel array 101 rises at time T1 between time t0 and time t1 and falls at time T2 between time t3 and time t4 due to delay. That is, as shown in FIG. 5B, even when the radiation generation apparatus 112 is instructed to stop emitting radiation at time t3 when the integrated value is determined to exceed the threshold value B, between time t3 and time t4. The falling component is irradiated to the pixel array 101. For this reason, the light is irradiated more than the threshold value B.

  Here, assuming an error S2 that is an integrated value of radiation that can be exposed at time T2, S2 can be obtained from the waveform of rise time t0 to t1 of the signal output from the output unit. This is because the rising waveform and falling waveform of the signal output from the output unit have a similar relationship. Therefore, an error caused by the falling waveform can be acquired from the difference of the rising waveform from the ideal rectangular wave. When the calculation unit 116 determines that the radiation rising is completed at time t1, the rising time T1, the maximum value A of the signal output from the output unit, and the waveform x (t) of the signal output from the output unit at time t. Thus, the difference S1 between the ideal square wave waveform and the integrated value of the rising waveform of the signal output from the actual output unit is calculated.

すなわち、時間Ｔ２に曝射され得る放射線の積算値である誤差Ｓ２は立ち上がり波形の積算値の差分Ｓ１と相似であるためＳ１≒Ｓ２とみなして、時間Ｔ２に曝射された放射線の積算値Ｓ２を立ち上がり波形に基づいて算出することができる。なお、立ち上がり波形と立下り波形との相関をより正確にするために、予め波形を取得しておいて、取得された波形から立ち上がりと立下りの相違の情報として係数Ｋを取得し、以下の式（２）で求めてもよい。ここで、Ｓ１＝Ｓ２の場合には、係数Ｋ＝１である。

That is, since the error S2 that is the integrated value of radiation that can be exposed at time T2 is similar to the difference S1 of the integrated value of the rising waveform, it is considered that S1≈S2, and the integrated value S2 of radiation that is exposed at time T2 Can be calculated based on the rising waveform. In order to make the correlation between the rising waveform and the falling waveform more accurate, the waveform is obtained in advance, and the coefficient K is obtained from the obtained waveform as the information on the difference between the rising and the falling, and You may obtain | require by Formula (2). Here, when S1 = S2, the coefficient K = 1.

次に、図６、図７（ａ）及び図７（ｂ）を用いて、算出部１１６が放射線の照射量を算出する方法を説明する。ここで、図６は処理を説明するためのフローチャートであり、図７（ａ）及び図７（ｂ）は算出部１１６による照射線量を算出する方法を説明するための線量画素Ｐ２から出力される信号及びその信号の積算値の時間変動特性である。

Next, a method of calculating the radiation dose of the calculation unit 116 will be described with reference to FIGS. 6, 7A, and 7B. Here, FIG. 6 is a flowchart for explaining the process, and FIGS. 7A and 7B are outputted from the dose pixel P2 for explaining the method of calculating the irradiation dose by the calculation unit 116. It is a time variation characteristic of the signal and the integrated value of the signal.

  As shown in FIG. 6, first, when the control unit 106 receives an exposure request control signal from the control computer 109 in step S601, the calculation unit 116 starts monitoring a signal from the output unit (step S602). Then, the calculation unit 116 calculates the difference (error) S1 between the integrated value of the ideal waveform and the actual rising waveform from the signal from the output unit at time T1 using the equation (1) (step S603). Then, the calculation unit 116 calculates an integrated value S2 of radiation that can be exposed at time T2 using the equation (2) from the calculated S1 (step S604), and monitors the calculated S2 (S605). .

  Here, a method of calculating the irradiation dose performed in step S604 will be described using FIGS. 7 (a) and 7 (b). In the method shown in FIG. 7A, the calculation unit 116 calculates the irradiation dose considering the calculated S2 minutes by changing the threshold value B to the corrected threshold value B ′ based on the calculated S2. . On the other hand, the method shown in FIG. 7B is a method of correcting the integrated value Z (t) by adding the calculated S2 to the integrated value of the signal from the output unit. Here, the processing is performed on the integrated value of the signal from the output unit, but the present invention is not limited thereto, and for example, a signal intensity difference or a histogram may be used.

  When the calculation unit 116 determines whether or not the irradiation dose calculated by the calculation unit 116 exceeds the threshold value B or the corrected threshold value B ′ (step 606), and it is determined that the irradiation dose does not exceed (NO) Monitoring will continue. On the other hand, if it is determined that the value has exceeded (YES), the control unit 106 sends a control signal for requesting the radiation control device 110 to stop radiation emission by the radiation generation device 111 via the control computer 109. It outputs (step 607). Thereafter, the calculation by the calculation unit 116 is ended, and the monitor is ended (S608).

  In the embodiment, the calculation unit 116 is included in the signal processing unit 105, that is, the calculation unit 116 is included in the imaging apparatus 100. However, the present invention is not limited thereto. For example, the calculation unit 116 may be included in the control computer 109. In such a case, the radiation imaging apparatus of the present invention may correspond to the one including the imaging apparatus 100 and the control computer 109. On the other hand, when the calculation unit 116 is included in the imaging apparatus 100 as in the embodiment, the imaging apparatus 100 may correspond to the radiation imaging apparatus of the present invention. Also, it can be realized by the computer included in the calculation unit 116 executing a program. Also, means for supplying a program to a computer, for example, a computer-readable recording medium such as a CD-ROM recording such a program, or a transmission medium such as the Internet for transmitting such a program is also applied as an embodiment of the present invention. Can. The above program can also be applied as an embodiment of the present invention. The above program, recording medium, transmission medium and program are included in the scope of the present invention. In addition, inventions based on combinations that can be easily imagined from the embodiments of the present invention are also included in the scope of the present invention.

100 image pickup apparatus 101 pixel array 106 control unit 116 calculation unit

Claims (12)

A pixel array including a plurality of pixels for outputting an image signal according to the radiation emitted from the radiation generator;
An output unit for outputting a signal for calculating an irradiation dose of radiation applied to the pixel array;
A calculation unit that calculates an error caused by the falling waveform of the data based on the rising waveform of the data indicating the waveform of the signal output from the output unit;
A control unit that controls a timing of outputting a control signal for requesting stop of radiation emission by the radiation generation apparatus based on the error calculated by the calculation unit;
A radiation imaging apparatus comprising:   The radiation imaging apparatus according to claim 1, wherein the calculation unit calculates the irradiation dose based on the error. The calculating unit determines that the waveform of the signal from the output unit at time T1 between time t0 and time t1 is x (t), the maximum value of the signal from the output unit is A, and the waveform of an ideal rectangular wave Assuming that the difference between the integrated values of the rising waveforms of the signal output from the actual output unit is S1 and the coefficient is K, the error S2 is

The radiation imaging apparatus according to claim 1, wherein:   The radiation imaging apparatus according to claim 3, wherein the calculation unit calculates the irradiation dose by adding the error to a signal from the output unit.   The calculation unit determines a threshold value for determining whether or not the irradiation dose of the radiation irradiated to the pixel array is an appropriate irradiation dose based on the error by comparing with the signal from the output unit. The radiation imaging apparatus according to claim 3, wherein the irradiation dose is calculated by changing.   6. The radiation according to claim 1, wherein each of the plurality of pixels includes a conversion element that converts radiation into an electrical signal and a switch element that outputs the electrical signal. Imaging device.   The plurality of pixels include an imaging pixel P1 outputting a signal for becoming an image signal according to radiation, and a dose pixel P2 outputting a signal for calculating an irradiation dose of radiation being irradiated to the pixel array 101. The radiation imaging apparatus according to claim 6, comprising: It further includes a drive circuit for imaging for driving the imaging pixel, a drive circuit for dose for driving the dose pixel, and a readout circuit for reading out an electrical signal output in parallel from the pixel array. ,
The radiation imaging apparatus according to claim 7, wherein the output unit includes the dose pixel, a drive circuit for the dose , and the readout circuit. The radiation imaging apparatus according to any one of claims 1 to 8,
The radiation generator for emitting radiation to the radiation imaging device;
Radiation imaging system. A radiation imaging apparatus including an output unit for outputting a signal for calculating an irradiation dose of radiation irradiated to a pixel array including a plurality of pixels for outputting an image signal according to radiation emitted from the radiation generation apparatus A method for controlling stop of radiation emission by the radiation generator,
In order to request stop of radiation emission by the radiation generating apparatus using an error caused by the falling waveform of the data calculated based on the rising waveform of the data indicating the waveform of the signal output from the output unit The method of controlling the timing which outputs the control signal of this. A pixel array including a plurality of pixels for outputting an image signal according to the radiation emitted from the radiation generator;
An output unit for outputting a signal for calculating an irradiation dose of radiation applied to the pixel array;
A calculation unit that calculates the irradiation dose based on a signal output from the output unit;
A radiation imaging apparatus comprising
The calculation unit calculates an error caused by the falling waveform of the data based on a rising waveform of data indicating a waveform of the signal output from the output unit, and the irradiation dose is calculated based on the calculated error. A radiation imaging apparatus characterized by calculating. A radiation imaging apparatus including an output unit for outputting a signal for calculating an irradiation dose of radiation irradiated to a pixel array including a plurality of pixels for outputting an image signal according to radiation emitted from the radiation generation apparatus A method of calculating the radiation dose of
And calculating the irradiation dose using a value calculated based on a rising waveform of data indicating a waveform of a signal output from the output unit.

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