JP2010276580A - Radiographic apparatus and control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a load, a power consumption, and a heating value of a light source for irradiating light aimed at reset of a conversion element, and to suppress deterioration progression of the conversion element. <P>SOLUTION: An apparatus includes a plane detector 120 constituted by including a plurality of pixels having conversion elements, for acquiring a radiographic image, based on a radiation 111b transmitted through a subject 300; the light source 130 for irradiating light having a wavelength band detectable by the conversion element to the conversion element; and a control part 150 for detecting a reference value from an offset image photographed, without having to use radiation prior to photographing a radiographic image, and irradiating from a light source 130, light for putting the conversion element into a saturated state based on the reference value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiation imaging apparatus that captures an object using radiation and a control method thereof. In this specification, it is assumed that electromagnetic waves such as X-rays and γ rays, α rays, and β rays are included in the radiation.

  In recent years, digital radiography apparatuses having a conversion element that converts non-single crystal semiconductors such as amorphous silicon and amorphous selenium into a main material and converts radiation or light into electric charges have been put into practical use. In addition, digital radiography apparatuses such as CCD and CMOS sensors, which are mainly composed of a single crystal semiconductor and have a conversion element that converts radiation or light into electric charges, have been put into practical use.

  The radiographic apparatus uses a phosphor that converts radiation into visible light, an indirect method of converting the visible light into charges with a conversion element mainly made of amorphous silicon, and amorphous selenium as the main material. There is a direct method in which radiation is directly converted into electric charge by a conversion element. Since both methods can realize a thin radiation detector with a large area, it is also called a flat panel detector (FPD) or a flat detector, and the time from photographing a subject to observing the radiation image is very short. It has the characteristics.

  These radiographic apparatuses are affected by the elapsed time from when the apparatus is turned on and the conversion element is biased, the time of the imaging operation, the amount of radiation or the amount of light irradiated to the apparatus, etc. There is a risk of fluctuations in the image characteristics and fluctuations in the acquired image signal. For example, the dangling bond or defect of the conversion element may act as a trap level, causing the dark current to fluctuate, or an afterimage (lag) may occur or fluctuate due to the influence of past radiation or light irradiation history. . In addition, due to at least one of these factors, there is a possibility that the sensitivity which is the input / output characteristic between the input of radiation or light and the output of the generated charge in the conversion element may vary.

  Therefore, in the following Patent Document 1 and Patent Document 2, before irradiating the radiation imaging apparatus with radiation that bears subject information, light that does not bear subject information is irradiated from a separately prepared light source to obtain characteristics and acquisition of the apparatus. Thus, a fluctuation suppressing effect for suppressing fluctuations in the image signal to be obtained is obtained.

JP 2007-181183 A JP 2008-256675 A

  However, with the techniques of Patent Document 1 and Patent Document 2, there is a concern that the amount of light that is applied to light that does not carry subject information is increased. In this case, as the amount of current flowing through the light source that emits light increases, the load on the light source increases, the power consumption of the light source increases, and the amount of heat generated by the light source also increases. Moreover, when there is much irradiation amount of the light from a light source, the element deterioration of the conversion element irradiated with light will be accelerated | stimulated. In addition, the range in which an afterimage is generated varies depending on the range irradiated with radiation immediately before.

  The present invention has been made in view of such problems, and reduces the load, power consumption, and heat generation of a light source that emits light for the purpose of resetting the conversion element, and promotes deterioration of the conversion element. An object of the present invention is to provide a radiation imaging apparatus that suppresses noise and a control method thereof.

The radiation imaging apparatus of the present invention is a radiation imaging apparatus that captures a subject using radiation, and includes a plurality of pixels having a conversion element, in order to acquire a radiation image based on the radiation transmitted through the subject. A flat detector, a light source that emits light in a wavelength band that can be sensed by the conversion element to the conversion element, and an offset image that is captured without using the radiation before the radiographic image is captured And a control unit that performs control to irradiate light from the light source that saturates the conversion element based on the reference value.
The present invention also includes a method for controlling the above-described radiation imaging apparatus.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to reduce the load of a light source which irradiates the light aiming at reset of a conversion element, power consumption, and emitted-heat amount, it is possible to suppress promotion of deterioration of a conversion element. Become.

It is a schematic diagram which shows an example of schematic structure of the radiography apparatus which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows an example of schematic structure of the flat detector shown in FIG. It is a schematic diagram which shows an example of schematic structure of the radiography system containing the radiography apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart which shows an example of the control method of the radiography apparatus which concerns on the 1st Embodiment of this invention. 3 is a timing chart according to the first embodiment of the present invention and related to switching from a still image mode (still image shooting mode) to a moving image mode (moving image shooting mode). It is a schematic diagram which shows the 1st Embodiment of this invention and shows an example of the pixel value of the horizontal line pixel containing the pixel from which the minimum pixel value of the offset image was detected. It is a flowchart which shows an example of the control method of the radiography apparatus which concerns on the 1st Embodiment of this invention. 4 is a timing chart according to the first embodiment of the present invention, which is related to switching from a moving image mode (moving image shooting mode) to a still image mode (still image shooting mode). It is a flowchart which shows an example of the control method of the radiography apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows an example of the control method of the radiography apparatus which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the 2nd Embodiment of this invention and shows an example of the detection range of the reference value set with the change of a radiation aperture range.

  Hereinafter, embodiments (embodiments) for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
First, a first embodiment of the present invention will be described.

  FIG. 1 is a schematic diagram illustrating an example of a schematic configuration of a radiation imaging apparatus according to the first embodiment of the present invention. The radiation imaging apparatus 100 shown in FIG. 1 is used particularly for medical purposes.

  As shown in FIG. 1, the radiation imaging apparatus 100 includes, for example, a radiation source 110, a flat detector 120, a light source 130, an image processing circuit 140, and a control unit 150.

  The radiation source 110 irradiates the subject 300 such as a patient with radiation 111 a such as X-rays based on the control of the control unit 150.

  As shown in FIG. 1, the flat detector 120 includes, for example, a wavelength converter 121, a sensor unit 122, a drive circuit 123, and a readout circuit 124.

  The wavelength converter 121 converts the wavelength of the radiation 111b that has passed through the subject 300 into visible light. The sensor unit 122 includes a plurality of pixels each having a conversion element, and outputs an electrical signal corresponding to visible light obtained by the wavelength converter 121. The drive circuit 123 drives the sensor unit 122 based on the control of the control unit 150. The readout circuit 124 reads out an electrical signal from the sensor unit 122 and outputs a digital image signal (radiation image signal) based on the control of the control unit 150.

  Based on the control of the control unit 150, the light source 130 emits light that does not carry subject information to the sensor unit 122 in order to suppress fluctuations in characteristics of the radiation imaging apparatus 100 and acquired radiographic image signals. . Specifically, the light source 130 irradiates the conversion element of the sensor unit 122 with light in a wavelength band that can be detected by the conversion element. In this embodiment, at least the flat detector 120 and the light source 130 are provided in a housing (not shown).

  The image processing circuit 140 appropriately performs image processing on the digital image signal read from the reading circuit 124 based on the control of the control unit 150. The specific method of image processing performed by the image processing circuit 140 is any method that uses a digital image signal and can solve the above-described problems.

  The control unit 150 controls the radiation source 110, the drive circuit 123, the readout circuit 124, the light source 130, the image processing circuit 140, and the like as necessary, and comprehensively controls the operation of the radiation imaging apparatus 100. is there. For example, the control unit 150 inputs the digital image signal image-processed by the image processing circuit 140 and controls the operation of the light source 130 based on the input digital image signal.

  Note that at least one of the image processing circuit 140 and the control unit 150 may be incorporated in the same IC as the readout circuit 124 or a different IC and held in the housing. Further, in the radiation imaging apparatus 100, a subject 300 is installed between the radiation source 110 and the flat detector 120, and a digital image signal based on an electrical signal corresponding to the dose of the radiation 111b that has passed through the subject 300 carrying subject information is generated. To be acquired.

  Further, in the present embodiment, a wavelength converter 121 is provided as the flat detector 120, and an indirect method is used in which visible light wavelength-converted from radiation by the wavelength converter 121 is converted into an electrical signal by the sensor unit 122. However, the present invention is not limited to this. For example, you may use the form of the direct system which converts a radiation into an electrical signal directly in the sensor part 122, without using the wavelength converter 121. FIG.

  In this embodiment, the control unit 150 (including the flat detector 120 and the image processing circuit 140 as necessary) functions as a unit that detects information indicating the necessity of light irradiation from the light source 130 to the sensor unit 122. is doing.

Next, the flat detector 120 will be described in detail.
FIG. 2 is a schematic diagram illustrating an example of a schematic configuration of the flat detector 120 illustrated in FIG. 1. In the example shown in FIG. 2, for convenience of explanation, nine pixels of 3 rows × 3 columns are shown as the number of pixels 1220, but the present invention is not limited to this, and the number of pixels is as required. The number of matrices can be determined as appropriate.

  The sensor unit 122 includes a radiation detection unit in which a plurality of pixels 1220 (S11 to S33) are arranged in a two-dimensional matrix on an insulating substrate such as a glass substrate. Each pixel 1220 (S11 to S33) includes a conversion element 1221 (D11 to D33) that converts radiation or light into electric charge, and a switch element 1222 (T11 to T11) that outputs an electric signal based on the converted electric charge. T33). Each of the conversion elements 1221 (D11 to D33) includes a conversion unit D that converts radiation or light into electric charges and a capacitor C1 that stores the electric charges. The capacitor C1 may be separately configured outside the conversion element 1221.

Since the planar detector 120 according to the present embodiment is an indirect system, the wavelength converter 121 shown in FIG. 1 is configured on the upper surface of the sensor unit 122, although not shown in FIG. Here, the wavelength converter 121 is formed by suitably using a material such as CsI: Tl or Gd ₂ O ₂ S: Tb, for example.

  In addition, the conversion element 1221 (D11 to D33) in the present embodiment is configured using, for example, a MIS type conversion element whose main material is amorphous silicon. However, the present invention is not limited to this, and a PIN conversion element may be used. In addition, as the conversion element 1221 (D11 to D33), an element that can directly convert radiation mainly composed of amorphous selenium into electric charge may be used. In this case, the wavelength converter 121 is not necessary. The conversion element 1221 (D11 to D33) includes at least two electrodes and a semiconductor layer provided between the two electrodes.

  The switch element 1222 (T11 to T33) in the present embodiment is configured using, for example, a thin film transistor (TFT) whose main material is amorphous silicon. However, the present invention is not limited to this, and a TFT mainly composed of polysilicon may be used. Further, as shown in FIG. 2, the switch elements 1222 (T11 to T33) in the present embodiment use three-terminal active elements, but the present invention is not limited to this, and switching diodes, etc. These two-terminal active elements may be used. In addition, as shown in FIG. 2, the switch element 1222 (T11 to T33) in this embodiment includes one electrode of the conversion element 1221 and one of the source and drain that are the two main electrodes of the switch element 1222. It is connected. However, the present invention is not limited to this. For example, the conversion element 1221 and the gate of the switch element 1222 may be connected to form a source follow amplifier. In that case, a switch element for initializing the potential of the connection portion between the conversion element 1221 and the gate of the switch element 1222 may be separately provided.

  The drive wirings G1 to G3 are connected in common to the gate, which is the control terminal of the switch element 1222 of the plurality of pixels 1220 in the row direction in the sensor unit 122, and the drive signal from the drive circuit 123 is sent to each switch. The data is transmitted to the element 1222. The signal wirings M <b> 1 to M <b> 3 are connected in common to the other of the sources or drains of the switch elements 1222 of the plurality of pixels 1220 in the column direction in the sensor unit 122, and the electric signals output by the switch elements 1222 are transmitted. The data is transmitted to the reading circuit 124. In this embodiment, the other electrode of the conversion element 1221 is connected to a common bias wiring (not shown) for the plurality of pixels 1220 so that the conversion element 1221 converts radiation or light into electric charges. A bias is supplied to the conversion element 1221.

  As described above, the sensor unit 122 includes the pixels 1220 (S11 to S33) provided on the insulating substrate, the drive wirings G1 to G3, the signal wirings M1 to M3, and the bias wiring.

  The drive circuit 123 is electrically connected to the drive wirings G1 to G3, and applies a drive signal in units of rows to the switch elements 1222 of the pixels 1220 connected to the respective drive wirings G1 to G3. The sensor unit 122 is driven by controlling the state and the non-communication state.

  Here, the drive signal output from the drive circuit 123 has a pulsed conduction voltage that makes the switch element 1222 conductive. For example, the switch elements (T11 to T13) to which the drive signal is applied from the drive circuit 123 via the drive wiring G1 in the first row are in a conductive state, and an electric signal corresponding to the charge of the conversion elements (D11 to D13) is a signal. The data is output in parallel in units of lines via the wirings M1 to M3. Similarly, the switch elements (T21 to T23) in the second row and the switch elements (T31 to T33) in the third row are sequentially driven, and an electrical signal output from the pixel 1220 in units of rows is output by the readout circuit 124 for one frame. Are converted into digital image signals and output.

  The readout circuit 124 is electrically connected to the signal wirings M1 to M3, reads the electrical signals output via the signal wirings M1 to M3 in parallel in units of rows, converts the parallel signals into serial signals, and analog Is converted into a digital signal and a digital image signal is output.

  The reading circuit 124 is electrically connected to the signal wirings M1 to M3, amplifies the electrical signals from the respective M1 to M3, and outputs the operational amplifiers (A1 to A3), and samples the electrical signals from the operational amplifiers A sample hold circuit for holding is provided. Here, the sample-and-hold circuit is configured by switches (Sr1 to Sr3) that sample electric signals and capacitors (CL1 to CL3) that hold the sampled electric signals. These operational amplifiers (A1 to A3) and the sample hold circuit are provided for each of the signal wirings M1 to M3, and the electric signals output in parallel from the sensor unit 122 are processed in parallel up to the sample hold circuit.

  The readout circuit 124 further includes a multiplexer Sr4, an operational amplifier B, and an analog / digital converter (A / D converter) 1241. The multiplexer Sr4 sequentially outputs the electrical signals held in the sample and hold circuits provided for the signal wirings M1 to M3 and converts them into serial image signals. The operational amplifier B performs impedance conversion on the image signal output from the multiplexer Sr4. The A / D converter 1241 converts the analog image signal output from the operational amplifier B into a digital image signal, and outputs the digital image signal.

  In the example shown in FIG. 2, the A / D converter 1241 is provided at the subsequent stage of the multiplexer Sr4. However, the present invention is not limited to this. For example, the A / D converter 1241 is connected to the signal wiring. Each of M1 to M3 may be provided before the multiplexer Sr4. Further, the configuration in the readout circuit 124 is an example, and various forms are conceivable. An analog signal from the signal wirings M1 to M3 is input, and amplification, multiplexing, A / D conversion is performed, and a digital image signal is obtained. 2 may be used other than the configuration shown in FIG.

  Although not shown in FIG. 2, the radiation imaging apparatus 100 of the present embodiment has a surface opposite to the light receiving surface (that is, the radiation incident side) of the sensor unit 122 as shown in FIG. A light source 130 is disposed between the (rear surface) and the housing. Here, the light receiving surface of the sensor unit 122 is a surface on which the pixels 1220 are formed, is opposed to the wavelength converter 121, and is a surface on the side irradiated with radiation when the subject 300 is imaged.

  The light source 130 is preferably an organic EL panel, LED, cold cathode tube, or the like, and may be used in combination with a known light guide as necessary. Moreover, it is desirable that the light emission wavelength of the light source 130 be in a band that can be absorbed by the conversion element 1221 (D11 to D33). The light emitted from the light source 130 is directly incident from the back surface of the sensor unit 122 and is absorbed by the semiconductor layers of the conversion elements 1221 (D11 to D33).

Next, the image acquisition operation by the flat detector 120 will be described with reference to FIGS. 1 and 2.
When acquiring a radiographic image of the subject 300, the control unit 150 performs control to irradiate the subject 300 with the radiation 111 a from the radiation source 110. Thereby, the flat panel detector 120 is irradiated with the radiation 111b that has passed through the subject 300.

  Then, the radiation 111b irradiated to the flat detector 120 performs wavelength conversion on light in a wavelength band that can be detected by the conversion element 1221 (D11 to D33) of the sensor unit 122 in the wavelength converter 121, and the wavelength-converted light. Is irradiated to the conversion element 1221 (D11 to D33). The conversion element 1221 (D11 to D33) generates charges according to the amount of light irradiated in the conversion unit D, and the charges are accumulated in the capacitor C1. The operation so far is referred to as “accumulation operation”.

  Next, the control unit 150 controls the drive circuit 123 to supply drive signals from the drive circuit 123 to the respective drive wirings G1 to G3, and the switch elements 1222 (T11 to T33) are turned on for each row to set the pixels. A read operation for outputting an electric signal based on the electric charge from 1220 is performed. In the present embodiment, the drive signal from the drive circuit 123 is sequentially applied in the order of the drive wiring G1 in the first row, the drive wiring G2 in the second row, and the drive wiring G3 in the third row. Therefore, as described above, the switch element 1222 for the read operation is controlled in units of rows, and electrical signals are output in parallel from the pixels 1220 in units of rows.

  Specifically, first, a drive signal is applied from the drive circuit 123 to the drive wiring G1 in the first row, and a conduction voltage is applied to the control terminals of the switch elements T11 to T13 in the first row. As a result, the switch elements T11 to T13 in the first row are turned on, and electric signals based on the charges accumulated in the capacitors C1 of the pixels S11 to S13 in the first row are output in parallel to the signal wirings M1 to M3. Is done. Then, the electrical signals output to the signal wirings M1 to M3 are read by the reading circuit 124.

  The electrical signal read to the reading circuit 124 is amplified by the operational amplifiers A1 to A3. Here, the reset switches Sw <b> 1 to Sw <b> 3 connected to the operational amplifiers A <b> 1 to A <b> 3 are opened when the electric signal is read out under the control of the control unit 150. Subsequently, the controller 150 conducts the switches Sr1 to Sr3 of the sample and hold circuit and performs control to store the electric signals amplified by the operational amplifiers A1 to A3 in the capacitors CL1 to CL3 of the sample and hold circuit. After the electrical signals are accumulated in the capacitors CL1 to CL3, the control unit 150 turns off the switches Sr1 to Sr3, and interrupts the electrical connection between the capacitors CL1 to CL3 and the signal wirings M1 to M3. Thereafter, the control unit 150 resets the operational amplifiers A1 to A3 and the signal wirings M1 to M3 by using the reset switches Sw1 to Sw3, and prepares for the output of the electrical signal from the next row. The operation so far is referred to as “read operation”.

  The electric signals sampled and held in the capacitors CL1 to CL3 are sequentially output by the multiplexer Sr4, converted in parallel / serial, and sequentially read out to the amplifier B. Thereby, the electrical signals accumulated in the order of the capacitors CL1, CL2, and CL3 can be sequentially output. At this time, since the amount of charge accumulated every time the capacitor Cf4 of the amplifier B is output changes, the control unit 150 short-circuits the switch Sw4 to select the capacitor Cf4 every time the capacitors CL1 to CL3 are selected by the multiplexer Sr4. It is necessary to return to the initial state.

  As a result, electrical signals based on the charges of the pixels S11 to S13 in the first row are sequentially output to the amplifier B as analog electrical signals by the multiplexer Sr4. The analog electric signal is impedance-converted by the amplifier B, is digital-analog converted by the A / D converter 1241, and is output as a digital image signal for one row. The operation so far is referred to as “output operation”.

  Similarly, the readout operation and the output operation are sequentially performed on the pixels 1220 in the second row and the third row, so that digital image signals for each row are output from the readout circuit 124. Further, in the present embodiment, for example, the output operation of the first row and the read operation of the second row are performed over time in the same period. As a result, it is possible to shorten the time of the photographing operation for acquiring the image signal for one image, as compared with the mode in which the read operation for the second row is performed after the output operation for the first row.

  Next, a radiation imaging apparatus 100 according to the present embodiment and a method for controlling a radiation imaging system including the radiation imaging apparatus 100 will be described.

  In the radiation imaging apparatus 100, the radiation imaging apparatus 100 is affected by an elapsed time after the apparatus is turned on and a bias is applied to the conversion element 1221, an imaging operation time, a radiation amount or a light amount irradiated on the flat detector 120, and the like. The characteristics of the apparatus and the acquired image signal vary. In order to solve this, the radiation imaging apparatus 100 according to the present embodiment irradiates the sensor unit 122 with light that does not bear image information emitted from the light source 130, separately from the radiation 111 b having image information of the subject 300. Therefore, fluctuations in device characteristics and fluctuations in image signals are suppressed. However, in this case, when the amount of irradiation of light that does not bear image information is more than the saturation state of the conversion element 1221, unnecessary light is irradiated to the conversion element 1221, and the conversion element 1221 is deteriorated. As a result, the light source 130 that performs light irradiation deteriorates. Therefore, in the radiation imaging apparatus 100 of this embodiment, it is necessary to adjust the input voltage of the light source 130 in advance so that the light until the conversion element 1221 is saturated can be irradiated.

  FIG. 3 is a schematic diagram illustrating an example of a schematic configuration of a radiation imaging system including the radiation imaging apparatus according to the first embodiment of the present invention. Here, in FIG. 3, the same code | symbol is attached | subjected about the structure similar to the radiography apparatus 100 shown in FIG.

  As illustrated in FIG. 3, the radiation imaging system 10 includes, for example, a radiation imaging apparatus 100, a table 210, a radiation generation apparatus 220, and a monitor 230.

The table 210 is a table on which the subject 300 shown in FIG. 1 is placed.
The radiation source 110 is attached at a position facing the flat detector 120 with a table 210 on which the subject 300 is placed. As in FIG. 1, the flat detector 120 includes a wavelength converter 121, a sensor unit 122, a drive circuit 123, and a readout circuit 124. In the example shown in FIG. 3, an example in which the flat detector 120 is attached to the table 210 is shown. However, for example, the flat detector 120 may be freely carried as a cassette. The flat panel detector 120 is connected to a control unit 150 formed of a PC (personal computer) by a cable or wireless communication, and is connected to a power source (not shown) inside the radiation imaging apparatus 100 and the radiation generation apparatus 220. Synchronized with the radiation source 110.

  The radiation generator 220 is provided with various buttons such as an imaging button (moving image) 221 and an imaging button (still image) 222, and the radiation source 110 according to the operation state of the various buttons and the control of the control unit 150. To generate radiation 111a.

  The monitor 230 is connected to the control unit 150, for example, and a photographer (engineer, doctor, etc.) can check the captured image through the monitor 230.

  In the present embodiment, the image processing circuit 140 is configured separately from the control unit 150 configured by a PC. However, for example, the image processing circuit 140 is configured inside the control unit 150 configured by a PC. There may be. The image processing circuit 140 acquires the output from the sensor unit 122 as a digital image signal through the reading circuit 124 and performs image processing.

  The control unit 150 according to the present embodiment is based on the dark output value obtained from the image processing circuit 140, information after the arithmetic processing using the dark output image corresponding to one image, and the operation state of the radiation source 110. Thus, the light emission operation of the light source 130 is controlled. The conditions for causing the light source 130 to emit light will be described later.

  In addition, the radiographic apparatus 100 has radiographing functions of a still image mode (still image shooting mode) for capturing a radiographic image as a still image and a moving image mode (moving image shooting mode) for capturing a radiographic image as a moving image. is there. The radiation imaging apparatus 100 is configured to be able to switch at least between a still image mode and a moving image mode. The photographer can switch from the still image mode to the moving image mode by operating the shooting button (moving image) 221 in FIG. 3, and can switch from the moving image mode to the still image mode by operating the shooting button (still image) 222. Is possible.

Next, a control example including shooting timing will be described.
FIG. 4 is a flowchart showing an example of a control method of the radiation imaging apparatus according to the first embodiment of the present invention. Specifically, FIG. 4 is a flowchart of control related to switching from the still image mode (still image shooting mode) to the moving image mode (moving image shooting mode).

  During shooting in the still image mode, first, in step S101, the control unit 150 determines whether or not the shooting button (moving image) 221 in FIG. 3 has been pressed.

  As a result of the determination in step S101, if the shooting button (moving image) 221 has not been pressed, the process proceeds to step S102, and the control unit 150 performs control to continue shooting in the still image mode. Then, it returns to step S101.

  On the other hand, as a result of the determination in step S101, if the shooting button (moving image) 221 is pressed, the process proceeds to step S103, and the control unit 150 sets the moving image mode.

  Subsequently, in step S104, the control unit 150 performs control to perform shooting in the last still image mode.

  Subsequently, in step S105, the control unit 150 performs control to end shooting in the still image mode.

  Along with the processing in step S105, in step S106, the control unit 150 performs control to detect a reference value (in this example, the minimum pixel value) from all the pixel values of the offset image obtained from the flat detector 120. Here, the offset image is an image captured without irradiating the subject 300 with radiation before (immediately before) performing moving image capturing (S110) of the radiation image related to switching of the capturing mode.

  Subsequently, in step S107, the control unit 150 performs control to store the reference value (minimum pixel value in this example) detected in step S106, for example, in an internal memory.

  Subsequently, in step S108, the control unit 150 performs control to adjust the light emission amount of the light source 130 based on the reference value described above, for example. Specifically, the control unit 150 performs control for irradiating light from the light source 130 that makes the conversion element 1221 saturated.

When the processes of steps S105 and S108 are completed, the process proceeds to step S109.
In step S109, based on the adjustment of the light emission amount by the control unit 150 in step S108, the light source 130 emits the light of the light emission amount related to the adjustment to the sensor unit 122 for irradiation.

Thereafter, the process proceeds to step S110, and the control unit 150 controls the start of shooting in the moving image mode set in step S103.
With the above processing, the processing of the flowchart shown in FIG. 4 ends.

  FIG. 5 shows a first embodiment of the present invention, and is a timing chart relating to switching from a still image mode (still image shooting mode) to a moving image mode (moving image shooting mode). That is, FIG. 5 corresponds to the processing of the flowchart shown in FIG.

  In the drive timing chart of FIG. 5, under the control of the control unit 150, in the still image mode and the moving image mode, the offset image F in which no radiation is emitted is captured continuously with the radiation image X captured by radiation emission. Here, the offset image F will be described as an example of the image taken immediately before. Then, the last captured offset image F is sent from the flat detector 120 to the control unit 150 and stored in an internal memory or the like.

  At this time, the control unit 150 compares pixel values pixel by pixel before or after AD conversion of the A / D converter 1241 in FIG. 2 and detects a reference value from all pixel values of the offset image F. Here, since the reference value may be converted by the A / D converter 1241, it becomes the maximum pixel value or the minimum pixel value (in this example, the minimum pixel value is used). The reference value may be a digital value, an analog value, or other signals. Here, in this embodiment, the case where the reference value is the minimum pixel value will be described as an example.

FIG. 6 is a schematic diagram illustrating an example of the pixel values of the horizontal line pixels including the pixel in which the minimum pixel value of the offset image is detected according to the first embodiment of this invention.
Specifically, the control unit 150 detects the reference value that is the minimum pixel value, calculates the difference pixel value from the reference value to the saturation value of the pixel, and performs all of the next radiographic image capturing. The light emission amount (irradiation amount) at which the conversion element 1221 is saturated is predicted in advance to adjust the light emission amount. Then, the light source 130 irradiates the sensor unit 122 with light as shown in the timing chart of FIG. 5 based on the control of the control unit 150, and the conversion element 1221 that is predicted and adjusted in advance is saturated. Irradiate light with the amount of emitted light. Thereafter, in the timing chart shown in FIG. 5, shooting in the moving image mode is started.

  FIG. 7 is a flowchart illustrating an example of a control method of the radiation imaging apparatus according to the first embodiment of the present invention. Specifically, FIG. 4 is a flowchart of control related to switching from the moving image mode (moving image shooting mode) to the still image mode (still image shooting mode).

  During shooting in the moving image mode, first, in step S201, the control unit 150 determines whether or not the shooting button (still image) 222 in FIG. 3 has been pressed.

  As a result of the determination in step S201, if the shooting button (still image) 222 has not been pressed, the process proceeds to step S202, and the control unit 150 continues to perform control for shooting in the moving image mode. Thereafter, the process returns to step S201.

  On the other hand, as a result of the determination in step S201, if the shooting button (still image) 222 is pressed, the process proceeds to step S203, and the control unit 150 sets the still image mode.

  Subsequently, in step S204, the control unit 150 performs control to perform shooting in the final moving image mode.

  Subsequently, in step S205, the control unit 150 performs control to end shooting in the moving image mode.

  Along with the processing in step S205, in step S206, the control unit 150 performs control to detect a reference value (the minimum pixel value in this example) from all the pixel values of the offset image obtained from the flat detector 120. Here, the offset image is an image captured without irradiating the subject 300 with radiation before (immediately before) performing still image capturing (S210) of the radiation image related to switching of the capturing mode.

  Subsequently, in step S207, the control unit 150 performs control to store the reference value (minimum pixel value in this example) detected in step S206, for example, in an internal memory.

  Subsequently, in step S208, the control unit 150 performs control to adjust the light emission amount of the light source 130 based on the reference value described above, for example. Specifically, the control unit 150 performs control for irradiating light from the light source 130 that makes the conversion element 1221 saturated.

When the processes of steps S205 and S208 are completed, the process proceeds to step S209.
In step S209, the light source 130 emits light of the light emission amount related to the adjustment to the sensor unit 122 based on the adjustment of the light emission amount by the control unit 150 in step S208.

Thereafter, the process proceeds to step S210, and the control unit 150 controls the start of shooting in the still image mode set in step S203.
With the above processing, the processing of the flowchart shown in FIG. 7 ends.

  FIG. 8 shows a first embodiment of the present invention, and is a timing chart relating to switching from the moving image mode (moving image shooting mode) to the still image mode (still image shooting mode). That is, FIG. 8 corresponds to the processing of the flowchart shown in FIG.

  Also in the case of switching in FIGS. 7 and 8, similarly to the case of switching in FIGS. 4 and 5 described above, the light irradiated from the light source 130 is controlled to irradiate the conversion element 1221 with light.

  According to the first embodiment, by controlling the light emission amount of the light source based on the reference value in the offset image, it is possible to suppress the single light irradiation amount from the light source 130. Thereby, it is possible to reduce the load, power consumption, and heat generation amount of the light source 130 that emits light for the purpose of (light) resetting of the conversion element 1221, and to suppress the deterioration of the conversion element 1221. Is possible.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  Here, the schematic configuration of the radiation imaging apparatus according to the second embodiment is the same as the schematic configuration of the radiation imaging apparatus 100 of FIG. 1 according to the first embodiment. The schematic configuration of the radiation imaging system according to the second embodiment is the same as the schematic configuration of the radiation imaging system 10 of FIG. 3 according to the first embodiment. In the following description, the description will focus on parts that are different from the first embodiment.

  FIG. 9 is a flowchart showing an example of a control method of the radiation imaging apparatus according to the second embodiment of the present invention. Specifically, FIG. 9 is a flowchart of control related to switching from the still image mode (still image shooting mode) to the moving image mode (moving image shooting mode). The same step numbers are used for the same processing as the processing shown in FIG. The description is omitted.

  First, in the process of FIG. 9, the processes of steps S101 to S105 shown in FIG. 4 are performed.

When the process of step S104 ends, in step S301, the control unit 150 detects a radiation aperture range (radiation irradiation range).
Specifically, in step S301, when the radiation irradiation range is switched while the distance between the radiation source 110 and the flat detector 120 is constant, the control unit 150 first applies a radiation aperture range (radiation) to the encoder or the like of the radiation generator 220. The position information request signal is transmitted. Then, when the radiation aperture range (radiation irradiation range) is determined, the control unit 150 receives a signal of the radiation pixel range as the radiation aperture range from the radiation generation device 220, and detects the radiation aperture range from the received signal. Do.

  Subsequently, in step S302, the control unit 150 first sets a reference value detection range based on the radiation aperture range detected in step S301. Then, the control unit 150 performs control to detect a reference value (the minimum pixel value in this example) from all the pixel values of the offset image obtained from the flat detector 120 based on the set reference value detection range. . Here, the offset image is the same as that in step S106 of FIG.

  Thereafter, the processing in the flowchart shown in FIG. 9 is ended through the processing in steps S107 to S110 shown in FIG.

  FIG. 10 is a flowchart showing an example of a control method of the radiation imaging apparatus according to the second embodiment of the present invention. Specifically, FIG. 10 is a flowchart of control related to switching from the moving image mode (moving image shooting mode) to the still image mode (still image shooting mode), and the same step numbers are used for the same processing as the processing shown in FIG. The description is omitted.

  First, in the process of FIG. 10, the processes of steps S201 to S205 shown in FIG. 7 are performed.

When the process of step S204 ends, in step S401, the control unit 150 detects a radiation aperture range (radiation irradiation range).
Specifically, in step S401, when the radiation irradiation range is switched while the distance between the radiation source 110 and the flat detector 120 is constant, the control unit 150 first applies a radiation aperture range (radiation) to the encoder or the like of the radiation generator 220. The position information request signal is transmitted. Then, when the radiation aperture range (radiation irradiation range) is determined, the control unit 150 receives a signal of the radiation pixel range as the radiation aperture range from the radiation generation device 220, and detects the radiation aperture range from the received signal. Do.

  Subsequently, in step S402, the control unit 150 first sets a reference value detection range based on the radiation aperture range detected in step S401. Then, the control unit 150 performs control to detect a reference value (the minimum pixel value in this example) from all the pixel values of the offset image obtained from the flat detector 120 based on the set reference value detection range. . Here, the offset image is the same as that in step S206 of FIG.

  Thereafter, the processing in the flowchart shown in FIG. 10 is ended through the processing in steps S207 to S210 shown in FIG.

  FIG. 11 is a schematic diagram illustrating an example of a reference value detection range set in accordance with a change in the radiation aperture range according to the second embodiment of this invention.

  FIG. 11A shows a case where the radiation aperture range (radiation irradiation range) is enlarged when the imaging mode is switched. In FIG. 11A, a range 1101 is a radiation aperture range irradiated with radiation in the previous (immediately preceding) imaging, and a range 1102 is a radiation aperture range irradiated with radiation in the current imaging. The range is expanded from range 1101 to range 1102. In this case, for example, the control unit 150 detects a reference value (minimum pixel value) from all the pixel values of the offset image in the range, in which a range in which no radiation is irradiated in the previous imaging is set as a reference value detection range. .

  FIG. 11B shows a case where the radiation aperture range (radiation irradiation range) is reduced when the imaging mode is switched. In FIG. 11B, a range 1103 is a radiation aperture range irradiated with radiation in the previous (immediately preceding) imaging, and a range 1104 is a radiation aperture range irradiated with radiation in the current imaging. The range is reduced from the range 1103 to the range 1104. In this case, for example, the control unit 150 uses the reduced range (1104) as the reference value detection range, and detects the reference value (minimum pixel value) from all the pixel values of the offset image in the range.

  According to the second embodiment, by setting the reference value detection range based on the radiation aperture range, in addition to the effects of the first embodiment, the number of pixels to be detected by the reference value can be further reduced. Thus, the detection of the reference value from the offset image can be accelerated.

(Other embodiments of the present invention)
4, 7, 9, and 10 showing the control method of the radiation imaging apparatus 100 according to each embodiment of the present invention described above, the CPU of the computer executes a program stored in the storage medium. Can be realized. This program and a computer-readable recording medium storing the program are included in the present invention.

  In addition, the present invention can be implemented as, for example, a system, apparatus, method, program, storage medium, or the like. Specifically, the present invention may be applied to a system including a plurality of devices. You may apply to the apparatus which consists of one apparatus.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowcharts shown in FIGS. 4, 7, 9, and 10) that realizes the functions of the above-described embodiments is directly transferred to the system or apparatus. Or it includes what is supplied remotely. The present invention also includes a case where the system or the computer of the apparatus is achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Examples of the recording medium for supplying the program include a flexible disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, and CD-RW. In addition, there are magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R), and the like.

  As another program supply method, a browser on a client computer is used to connect to an Internet home page. The computer program itself of the present invention or a compressed file including an automatic installation function can be downloaded from the homepage by downloading it to a recording medium such as a hard disk.

  It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, the present invention includes a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. Let The downloaded key information can be used to execute the encrypted program and install it on the computer.

  Further, the functions of the respective embodiments described above are realized by the computer executing the read program. In addition, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can be realized by the processing.

  Further, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instructions of the program, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

  For the purpose of solving the problems of the present invention, a case where the above-described embodiments are combined or an easily conceivable application is included in the scope of the present invention. In other words, each of the above-described embodiments is merely an example of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. . That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

DESCRIPTION OF SYMBOLS 100: Radiography apparatus, 110: Radiation source, 111a, 111b: Radiation, 120: Plane detector, 121: Wavelength converter, 122: Sensor part, 123: Drive circuit, 124: Reading circuit, 130: Light source, 140: Image processing circuit, 150: control unit, 300: subject

Claims (7)

A radiography apparatus for imaging a subject using radiation,
A plane detector configured to include a plurality of pixels having a conversion element, and for obtaining a radiation image based on the radiation transmitted through the subject;
A light source that irradiates the conversion element with light in a wavelength band that can be sensed by the conversion element;
Control that irradiates light from the light source that detects a reference value from an offset image that is captured without using the radiation and that saturates the conversion element based on the reference value before capturing the radiation image A radiation imaging apparatus comprising: a control unit that performs:   The radiographic apparatus according to claim 1, wherein the light source is disposed on an opposite side to the radiation incident side of the flat panel detector.   3. The control unit according to claim 1, wherein the control unit performs control to adjust an emission amount of the light based on the reference value of the offset image captured immediately before capturing the radiographic image. The radiation imaging apparatus described. The reference value is a value detected by comparing each pixel value of the offset image,
4. The radiation according to claim 3, wherein when the radiographic image is captured, the control unit performs control by predicting in advance the light emission amount of the light at which all the conversion elements are saturated. 5. Shooting device. The radiation imaging apparatus is configured to at least switch between a still image mode for capturing the radiographic image as a still image and a moving image mode for capturing the radiation image as a moving image as an imaging mode,
5. The radiographic apparatus according to claim 1, wherein the control unit performs control to irradiate the light from the light source when the imaging mode is switched. 6.   The control unit sets the detection range of the reference value based on the irradiation range when the irradiation range of the radiation to the flat panel detector is switched when the imaging mode is switched, and sets the detection range of the reference value to the detection range of the reference value. 6. The radiographic apparatus according to claim 5, wherein the reference value is detected based on the reference value. A method for controlling a radiation imaging apparatus that performs imaging of a subject using radiation,
The radiation imaging apparatus includes a plurality of pixels each having a conversion element, and is a flat panel detector for acquiring a radiation image based on the radiation transmitted through the subject, and the conversion element can sense the conversion element. With a light source that emits light in various wavelength bands,
A detection step of detecting a reference value from an offset image captured without using the radiation before capturing the radiation image;
And a control step of performing control to irradiate light from the light source that saturates the conversion element based on the reference value.

Images