JP6189772B2 - Radiographic imaging system, image processing apparatus, radiographic imaging system control method, and radiographic imaging system control program - Google Patents

Description

  The present invention relates to a radiographic imaging system, an image processing apparatus, a radiographic imaging system control method, and a radiographic imaging system control program.

  2. Description of the Related Art Conventionally, for example, a radiographic imaging apparatus that performs radiographic imaging for medical diagnosis is known as a radiographic imaging apparatus that captures a subject. The radiation image capturing apparatus captures a radiation image by detecting radiation irradiated from the radiation irradiation apparatus and transmitted through the subject. The radiographic image capturing apparatus captures a radiographic image by collecting and reading out charges generated according to the irradiated radiation.

  A technique is known in which a plurality of radiographic image capturing apparatuses are used for capturing a large subject, for example, a long subject. When arranging a plurality of radiographic image capturing apparatuses adjacent to each other, end portions (parts) of the radiographic image capturing apparatuses are overlapped and overlapped so as not to cause defects in the radiographic image in adjacent portions. Yes.

  In the overlapped portion of the radiographic images taken, a step component due to the step at the end of the radiographic apparatus is generated and appears as a step artifact.

  Therefore, for example, in Patent Document 1, the luminance of a radiographic image obtained by photographing a subject is corrected by using a correction coefficient obtained from luminance data representing the density of an image obtained by X-ray photographing a reference subject. Describes a description of correcting the decrease in luminance in the overlapping region of the radiographic imaging device.

  Patent Document 2 describes a technique that suppresses luminance fluctuations that occur in the overlapped part by devising an overlapping method (overlapping area) of the radiation image capturing apparatus and facilitates image processing after capturing. ing.

JP 2000-278607 A JP 2000-292546 A

  In the above technique, if the incident direction of the radiation incident on the radiation image capturing apparatus changes, there may be a problem that the step component cannot be corrected appropriately.

  The present invention has been made to solve the above-described problems. Even when the incident direction of radiation changes between the correction image and the captured image, the step component generated in the captured image is corrected. An object of the present invention is to provide a radiographic imaging system, an image processing apparatus, a radiographic imaging system control method, and a radiographic imaging system control program that can be appropriately performed.

In order to achieve the above object, a radiographic imaging system of the present invention includes a first radiographic imaging device including a first radiographic imaging region that captures a radiographic image corresponding to radiation incident from a radiation irradiating device, and radiation. The first radiographic image capturing apparatus includes a second radiographing area that captures a corresponding radiographic image, and a part of the second radiographing area is overlapped with a part of the first radiographing area in the incident direction of the radiation. The second radiographic image capturing device disposed on the side far from the radiation irradiating device and the second radiographic image capturing device in accordance with the radiation incident on the second radiographic region, and the first of the first radiographic image capturing device. A correction image acquisition unit that acquires, as a correction image, a radiation image that includes a first step component generated due to a step with respect to the radiation incident direction in a part of the imaging region that is superimposed; A radiographic image of a subject captured at a timing different from the correction image by the image capturing device is acquired as a first captured image, captured at a different timing by the second radiographic image capturing device, and the first radiation image capturing device of the first radiographic image capturing device. From a correction image, a radiographic image of a subject including a second step component generated due to a step with respect to the incident direction of radiation in a part of the radiographed region overlapped, and a correction image As a modification for detecting one step component and detecting the second step component from the second photographed image to make the position of the first step component coincide with the position of the second step component, a correcting section for correcting the positional deviation of the second step components, imaging performed by using the image for correction the positional deviation is corrected by the correction unit, the inhibit correct variations in the gain of the second captured image Comprising an image correcting unit, and a step correcting unit that performs correction to reduce the level difference indicated by the second step component of the second photographed image corrected by the captured image correcting unit.

  The correction unit of the radiographic imaging system of the present invention corrects the positional deviation by converting at least one coordinate of the position of the first step component and the position of the second step component.

  The correction unit of the radiographic image capturing system of the present invention corrects the positional deviation by changing the shape of the first step component of the correction image to match the position of the first step component with the position of the second step component.

  The correction unit of the radiographic image capturing system of the present invention detects the first step component and the second step component by detecting an image representing a straight line generated by the step from each of the correction image and the second captured image.

The radiographic image capturing system of the present invention further includes a removal unit that performs a high-frequency component removal process for removing noise from the correction image, and the captured image correction unit uses the correction image from which noise has been removed by the removal unit. 2 photographed image you corrected.

  The level difference correction unit of the radiographic image capturing system of the present invention performs correction to reduce the density difference between the density of the second level difference component and the density of a component in a region different from the second level difference component in the second captured image.

Moreover, the image processing apparatus of this invention image | photographs the radiographic image according to the 1st radiographic imaging apparatus provided with the 1st imaging region which image | photographs the radiographic image according to the radiation which injected from the radiation irradiation apparatus, and a radiation. A second imaging region is provided, and a part of the second imaging region is overlapped with a part of the first imaging region with respect to the radiation incident direction, and is farther from the radiation irradiation device than the first radiation image capturing device. An image processing apparatus that performs image processing of a radiographic image captured by a second radiographic image capturing apparatus arranged in the first radiographic image capturing apparatus, and is captured by the second radiographic image capturing apparatus in accordance with radiation incident on the second image capturing area. The radiographic image including the first step component generated due to the step with respect to the incident direction of the radiation in the overlapped part of the first radiographic region of the first radiographic imaging device is acquired as a correction image. A radiographic image of a subject captured at a timing different from the correction image by the correction image acquisition unit and the first radiographic image capturing device is acquired as a first captured image, and is captured at a different timing by the second radiographic image capturing device. A captured image for acquiring a radiographic image of a subject including a second step component generated due to a step with respect to an incident direction of radiation in the overlapped part of the first imaging region of the first radiographic image capturing apparatus as a second captured image The first step component is detected from the acquisition unit and the correction image, the second step component is detected from the second photographed image, and the position of the first step component and the position of the second step component coincide with each other. as modifications to the correction unit for correcting a positional deviation between the first stepped component and the second step components, using the image for correction the positional deviation is corrected by the correction unit, the gain of the second captured image Comprising a captured image correcting unit that performs suppressing correcting variability, and a step correcting unit that performs correction to reduce the level difference indicated by the second step component of the second photographed image corrected by the captured image correcting unit.

Moreover, the control method of the radiographic imaging system of the present invention includes a first radiographic imaging device that includes a first radiographic region that captures a radiographic image corresponding to radiation incident from the radiation irradiation device, and radiation corresponding to the radiation. A second imaging region for capturing an image is provided, and radiation is more irradiated than the first radiographic imaging device in a state where a part of the second imaging region is overlapped with a part of the first imaging region with respect to the incident direction of radiation. a second radiographic image capturing device disposed from the device farther, a control method of a radiographic image capturing system having a, the correction image acquisition unit, first in response to the radiation incident on the second imaging region (2) A radiograph including a first step component caused by a step with respect to the incident direction of the radiation in the overlapped part of the first imaging region of the first radiographic image capturing device. A step of acquiring a line image as a correction image, and a captured image acquisition unit acquires, as a first captured image, a radiographic image of a subject captured at a timing different from the correction image by the first radiographic image capturing apparatus. Radiation of a subject including a second step component that is captured at different timings by the two radiographic image capturing devices and includes a step difference with respect to the incident direction of the radiation in the overlapped part of the first radiographic region of the first radiographic image capturing device. acquiring an image as the second photographic image, by the correction unit, the correction image, and detects the first stepped component, from the second captured image, to detect a second step component, the position of the first stepped component as modifications to the state in which coincide with the position of the second step components, and correcting the positional deviation between the first stepped component and the second step components, the captured image correcting unit , By using the image for correction the positional deviation is corrected by the correction unit and performing suppress correcting variation in gain of the second captured image, the step correction unit, a second shot, which is corrected by the captured image correcting unit And a step of performing correction to reduce the step indicated by the second step component of the image.

  Moreover, the control program of the radiographic imaging system of this invention is for making a computer perform each step of the control method of this invention.

  According to the present invention, even when the incident direction of radiation changes between the correction image and the photographed image, it is possible to appropriately correct the step component generated in the photographed image.

It is a schematic block diagram which shows schematic structure of an example of the radiographic imaging system which concerns on this Embodiment. It is a schematic block diagram which shows an example of the console for demonstrating the image processing function containing the various correction | amendment which concerns on this Embodiment. It is a block diagram showing an example of a structure of the radiographic imaging apparatus which concerns on this Embodiment. It is a line sectional view of an example of a pixel of a radiation detector concerning this embodiment. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus which concerns on this Embodiment, and an electronic cassette, and represents the state seen from the side. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus which concerns on this Embodiment, and an electronic cassette, and represents the radiographic imaging apparatus seen from the radiation irradiation apparatus side. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus which concerns on this Embodiment, and an electronic cassette, and represents the state which the radiographic imaging apparatus moved (moved) in FIG. 5B. It is explanatory drawing for demonstrating the radiographic image image | photographed with each radiographic imaging device which concerns on this Embodiment. (1) shows a radiographic image captured by the upper radiographic apparatus. (2) shows a radiographic image taken by the lower radiographic imaging device. It is explanatory drawing for demonstrating the change of the position of the cinch level | step difference component which concerns on this Embodiment, and a glass level | step difference component. (1) shows a case where the angles of the radiation X incident on the imaging region are different. (2) shows a case where the radiographic image capturing apparatus moves (moves). It is a flowchart showing an example of the flow of the image processing which correct | amends with respect to the picked-up image image | photographed with the upper radiographic imaging device which concerns on this Embodiment. It is a flowchart showing an example of the flow of the image processing which correct | amends with respect to the picked-up image image | photographed with the lower radiographic imaging device which concerns on this Embodiment. It is a schematic diagram for demonstrating an example of the flow of an image process which correct | amends with respect to the picked-up image image | photographed with the lower radiographic imaging device which concerns on this Embodiment. It is a schematic block diagram for demonstrating an example which has arrange | positioned the some electronic cassette adjacently. It is a schematic block diagram for demonstrating the other example which has arrange | positioned the several electronic cassette adjacently.

  Hereinafter, an example of the present embodiment will be described with reference to the drawings.

  First, a schematic configuration of the entire radiographic image capturing system including the radiographic image processing apparatus of the present embodiment will be described. FIG. 1 shows a schematic configuration diagram of an overall configuration of an example of a radiographic imaging system according to the present exemplary embodiment. In the radiographic imaging system 10 of the present exemplary embodiment, the electronic cassette 12 includes a plurality of radiographic imaging apparatuses 14.

  The radiographic imaging system 10 according to the present exemplary embodiment is based on an instruction (imaging menu) input from an external system such as an RIS (Radiology Information System) via the console 20. It has a function of taking a radiation image by an operation of an engineer or the like.

  In addition, the radiographic image capturing system 10 of the present embodiment displays a radiographic image captured by the electronic cassette 12 on a display unit (see FIG. 2) of the console 20 or a radiographic image interpretation device (not illustrated), thereby And has a function of causing radiographers to interpret radiographic images. The radiographic image reading device (not shown) is a device having a function for a radiographer to interpret a radiographic image taken, and is not particularly limited, but is a so-called radiographic viewer, display, mobile terminal, and tablet. A terminal etc. are mentioned.

  The radiographic image capturing system 10 of the present exemplary embodiment includes an electronic cassette 12, a radiation irradiation device 16, and a console 20.

  The radiation irradiation device 16 has a function of irradiating the imaging target region of the subject 18 with radiation X from a tube (not shown) which is a radiation irradiation source based on the control of the console 20. Note that the radiation irradiation device 16 is configured so that the user can directly and manually set the radiation X irradiation conditions such as the tube voltage, the tube current, and the irradiation time with respect to the radiation irradiation device 16. You may provide the display part for displaying conditions. In addition, the radiation irradiation device 16 transmits information indicating the manual setting, the setting value by the manual setting, and the current status (standby state, preparation state, during exposure, completion of exposure, and the like) to the console 20. In the following description, the position of the tube is assumed to be equal to the position of the radiation irradiation device 16.

The radiation X transmitted through the subject 18 is irradiated to the electronic cassette 12. The radiographic imaging device 14 of the electronic cassette 12 has a function of generating charges according to the dose of the radiation X transmitted through the subject 18 and generating and outputting image information indicating a radiographic image based on the generated charge amount. Have. In the present embodiment, the generation and output of image information is called photographing. The electronic cassette 12 according to the present embodiment includes a plurality of radiographic image capturing devices 14 (14 _{1 to} 14 ₃ ) in a housing 13 (details will be described later).

  In the present embodiment, image information indicating a radiographic image output by the electronic cassette 12 is input to the console 20. The console 20 according to the present embodiment has a function of controlling the electronic cassette 12 and the radiation irradiation device 16 by using an imaging menu and various information acquired from an external system or the like via a wireless communication LAN (Local Area Network) or the like. have. In addition, the console 20 of the present embodiment has a function of transmitting / receiving various information to / from the electronic cassette 12. The console 20 also has a function of outputting a radiographic image acquired from the electronic cassette 12 to a PACS (Picture Archiving and Communication System) 22. A radiographic image taken by the electronic cassette 12 is managed by the PACS 22.

  The console 20 of the present embodiment is a server computer. FIG. 2 shows an example of a schematic configuration diagram of the console 20 for explaining an image processing function including various corrections. The console 20 includes a control unit 30, a display unit drive unit 32, a display unit 34, an operation input detection unit 36, an operation input unit 38, an I / O (Input Output) unit 40, an I / F (Interface) unit 42, an I / F An F unit 44 and a storage unit 50 are provided.

  The control unit 30 has a function of controlling the operation of the entire console 20, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an HDD (Hard disk drive). ing. The CPU has a function of controlling the operation of the entire console 20, and various programs including an image processing program used by the CPU are stored in advance in the ROM. The RAM has a function of temporarily storing various data, and the HDD has a function of storing and holding various data. The control unit 30 functions as a correction image acquisition unit and a captured image acquisition unit. The control unit 30 has a function of performing image processing including various corrections on various images.

  The display unit driving unit 32 has a function of controlling display of various types of information on the display unit 34. The display unit 34 according to the present embodiment has a function of displaying an imaging menu, a captured radiographic image, and the like. The operation input detection unit 36 has a function of detecting an operation state and a processing operation with respect to the operation input unit 38. The operation input unit 38 is used by the user to input processing operations related to radiographic image capturing and image processing of the captured radiographic image. The operation input unit 38 may have a keyboard form as an example, or may have a touch panel form integrated with the display unit 34. Further, the operation input unit 38 may include a camera, and may have a form in which various instructions are input by causing the camera to recognize a user's gesture.

  Further, the I / O unit 40 and the I / F unit 42 have a function of transmitting and receiving various types of information between the PACS 22 and the RIS by wireless communication or the like. Further, the I / F unit 44 has a function of transmitting and receiving various types of information between the radiation image capturing device 14 and the radiation irradiation device 16.

  The storage unit 50 has a function of storing captured images, gain calib images, and the like (details will be described later).

  The control unit 30, the display unit drive unit 32, the operation input detection unit 36, the I / O unit 40, and the storage unit 50 are connected so as to be able to exchange information and the like with each other via a bus 46 such as a system bus or a control bus. Has been.

Next, a schematic configuration of the electronic cassette 12 according to the present embodiment will be described. The electronic cassette 12 includes a plurality of radiographic image capturing devices 14. In the present embodiment, as a specific example, the case where the electronic cassette 12 includes three radiographic imaging devices 14 (14 _{1 to} 14 ₃ ) as illustrated in FIG. 1 will be described. The number of image capturing devices 14 is not limited to the present embodiment. The radiographic imaging devices 14 ₁ , 14 ₂ , and 14 ₃ are referred to as the radiographic imaging device 14 when they are not distinguished or collectively referred to.

  The three radiographic image capturing devices 14 are accommodated in the housing 13. As shown in FIG. 1, in the present embodiment, the radiographic image capturing apparatus 14 is disposed adjacent to the subject 18 with the imaging region (imaging surface) facing the subject 18. In the electronic cassette 12 of the present embodiment, as shown in FIG. 1, the end (part) of the radiographic image capturing device 14 is arranged so as to overlap with the adjacent radiographic image capturing device 14 (details will be described later). .

  By arranging a plurality (three) of radiographic imaging devices 14 in this way, the entire electronic cassette 12 has a long imaging region.

  In FIG. 3, the block diagram showing an example of a structure of the radiographic imaging apparatus 14 which concerns on this Embodiment is shown. In the present embodiment, a case will be described in which the present invention is applied to an indirect conversion type radiographic image capturing apparatus 14 that once converts radiation such as X-rays into light and converts the converted light into electric charges. In FIG. 3, the scintillator 98 (see FIG. 4) that converts radiation into light is omitted.

  The radiographic imaging device 14 of the present exemplary embodiment includes a radiation detector 26, a scan signal control circuit 104, a signal detection circuit 105, a control unit 106, and a power supply 110.

  The radiation detector 26 generates light by receiving light, accumulates the generated charge, and a TFT (Thin Film Transistor) switch 74 that is a switch element for reading out the charge accumulated in the sensor unit 103. And a pixel 100 configured to include. In the present embodiment, charges are generated in the sensor unit 103 by irradiation with light converted by the scintillator 98 (see FIG. 4).

  A plurality of pixels 100 are arranged in a matrix in one direction (gate wiring direction in FIG. 3) and in a direction intersecting with the gate wiring direction (signal wiring direction in FIG. 3). In FIG. 3, the arrangement of the pixels 100 is simplified, but for example, 1024 × 1024 pixels 100 are arranged in the gate wiring direction and the signal wiring direction.

  In the radiation detector 26, a plurality of gate wirings 101 for turning on / off the TFT switch 74 and a plurality of signal wirings 73 for reading out the electric charges accumulated in the sensor unit 103 intersect each other. Is provided. In the present embodiment, one signal wiring 73 is provided for each pixel column in one direction, and one gate wiring 101 is provided for each pixel column in the cross direction. For example, when 1024 × 1024 pixels 100 are arranged in the gate wiring direction and the signal wiring direction, 1024 signal wirings 73 and 1024 gate wirings 101 are provided.

  Further, the radiation detector 26 is provided with a common electrode wiring 95 in parallel with each signal wiring 73. The common electrode wiring 95 has one end and the other end connected in parallel, and one end connected to a power supply 110 that supplies a predetermined bias voltage. The sensor unit 103 is connected to the common electrode wiring 95, and a bias voltage is applied via the common electrode wiring 95.

  A control signal for switching each TFT switch 74 flows through the gate wiring 101. As described above, when the control signal flows to each gate wiring 101, each TFT switch 74 is switched.

  An electric signal corresponding to the electric charge accumulated in each pixel 100 flows through the signal wiring 73 in accordance with the switching state of the TFT switch 74 of each pixel 100. More specifically, an electric signal corresponding to the amount of charge accumulated by turning on any TFT switch 74 of the pixel 100 connected to the signal wiring 73 flows through each signal wiring 73.

  Each signal wiring 73 is connected to a signal detection circuit 105 that detects an electrical signal flowing out to each signal wiring 73. Each gate line 101 is connected to a scan signal control circuit 104 that outputs a control signal for turning on / off the TFT switch 74 to each gate line 101. In FIG. 3, the signal detection circuit 105 and the scan signal control circuit 104 are shown in a simplified form. However, for example, a plurality of signal detection circuits 105 and a plurality of scan signal control circuits 104 are provided (for example, 256). The signal wiring 73 or the gate wiring 101 is connected every time. For example, when 1024 signal wirings 73 and 1024 gate wirings 101 are provided, four scan signal control circuits 104 are provided, 256 gate wirings 101 are connected, and four signal detection circuits 105 are provided 256. The signal wiring 73 is connected one by one.

  The signal detection circuit 105 incorporates an amplification circuit (not shown) for amplifying an input electric signal for each signal wiring 73. In the signal detection circuit 105, an electric signal input from each signal wiring 73 is amplified by an amplifier circuit and converted into a digital signal by an ADC (analog / digital converter).

  The signal detection circuit 105 and the scan signal control circuit 104 are subjected to a predetermined process such as noise removal on the digital signal converted by the signal detection circuit 105 and also indicate the signal detection timing to the signal detection circuit 105. A control unit 106 that outputs a control signal and outputs a control signal indicating the output timing of the scan signal to the scan signal control circuit 104 is connected.

  The control unit 106 according to the present embodiment is a microcomputer, and includes a nonvolatile storage unit (not shown) including a CPU (Central Processing Unit), ROM and RAM, flash memory, and the like. The control unit 106 performs control for radiographic imaging by executing a program stored in the ROM by the CPU.

  FIG. 4 shows a cross-sectional view of the pixel 100. As shown in FIG. 4, the pixel 100 (radiation detector 26) includes a TFT glass substrate 90 and a scintillator 98. As shown in FIG. 4, in the TFT glass substrate 90, a gate wiring 101 (see FIG. 3) and a gate electrode 72 are formed on an insulating substrate 71 made of non-alkali glass or the like. The gate wiring 101 and the gate electrode 72 are connected. The wiring layer in which the gate wiring 101 and the gate electrode 72 are formed (hereinafter also referred to as “first signal wiring layer”) is formed using Al or Cu, or a laminated film mainly composed of Al or Cu. However, it is not limited to these.

  An insulating film 85 is formed on one surface on the first signal wiring layer, and a portion located on the gate electrode 72 functions as a gate insulating film in the TFT switch 74. The insulating film 85 is made of, for example, SiNx, and is formed by, for example, CVD (Chemical Vapor Deposition) film formation.

  A semiconductor active layer 78 is formed in an island shape on the gate electrode 72 on the insulating film 85. The semiconductor active layer 78 is a channel portion of the TFT switch 74 and is made of, for example, an amorphous silicon film.

  On these upper layers, a source electrode 79 and a drain electrode 83 are formed. In the wiring layer in which the source electrode 79 and the drain electrode 83 are formed, a signal wiring 73 is formed together with the source electrode 79 and the drain electrode 83. The source electrode 79 is connected to the signal wiring 73. The wiring layer (hereinafter also referred to as “second signal wiring layer”) in which the source electrode 79, the drain electrode 83, and the signal wiring 73 are formed uses Al or Cu, or a laminated film mainly composed of Al or Cu. Although formed, it is not limited to these. An impurity-added semiconductor layer (not shown) made of impurity-doped amorphous silicon or the like is formed between the source electrode 79 and drain electrode 83 and the semiconductor active layer 78. These constitute a switching TFT switch 74. In the TFT switch 74, the source electrode 79 and the drain electrode 83 are reversed depending on the polarity of charges collected and accumulated by the lower electrode 81 described later.

  A TFT protective film layer 88 is provided to cover the second signal wiring layer and to protect the TFT switch 74 and the signal wiring 73 over almost the entire area (substantially the entire area) where the pixel 100 is provided on the substrate 71. Is formed. The TFT protective film layer 88 is made of, for example, SiNx, and is formed by, for example, CVD film formation.

  On the TFT protective film layer 88, a coating type interlayer insulating film 82 is formed. The interlayer insulating film 82 is a photosensitive organic material having a low dielectric constant (relative dielectric constant εr = 2 to 4) (for example, a positive photosensitive acrylic resin: a base polymer made of a copolymer of methacrylic acid and glycidyl methacrylate). And a material mixed with a naphthoquinonediazide-based positive photosensitive agent).

  In the TFT glass substrate 90 according to the present embodiment, the capacitance between the metals disposed in the upper layer and the lower layer of the interlayer insulating film 82 is kept low by the interlayer insulating film 82. In general, such a material also has a function as a flattening film, and has an effect of flattening a lower step. In the TFT glass substrate 90 according to the present embodiment, a contact hole 87 is formed at a position facing the drain electrode 83 of the interlayer insulating film 82 and the TFT protective film layer 88.

  A lower electrode 81 of the sensor unit 103 is formed on the interlayer insulating film 82 so as to cover the pixel region while filling the contact hole 87, and the lower electrode 81 is connected to the drain electrode 83 of the TFT switch 74. Yes. If the semiconductor layer 91 described later is as thick as about 1 μm, the lower electrode 81 has almost no material limitation if it has conductivity. Therefore, there is no problem if it is formed using a conductive metal such as an Al-based material or ITO (Indium Tin Oxide).

  On the other hand, when the thickness of the semiconductor layer 91 is thin (around 0.2 to 0.5 μm), light is not sufficiently absorbed by the semiconductor layer 91, so that an increase in leakage current due to light irradiation to the TFT switch 74 is prevented. An alloy mainly composed of a light-shielding metal or a laminated film is preferable.

  A semiconductor layer 91 that functions as a photodiode is formed on the lower electrode 81. In this embodiment, a PIN structure photodiode in which an n + layer, an i layer, and a p + layer (n + amorphous silicon, amorphous silicon, and p + amorphous silicon) are stacked is employed as the semiconductor layer 91. The semiconductor layer 91 is formed by sequentially stacking an n + layer 91A, an i layer 91B, and a p + layer 91C from the lower layer. The i layer 91 </ b> B generates charges (a pair of free electrons and free holes) when irradiated with light. The n + layer 91A and the p + layer 91C function as contact layers, and electrically connect the lower electrode 81 and an upper electrode 92 described later and the i layer 91B.

  An upper electrode 92 is individually formed on each semiconductor layer 91. For the upper electrode 92, for example, a material having high light transmittance such as ITO or IZO (Indium Zinc Oxide) is used. In the TFT glass substrate 90 according to the present embodiment, the sensor unit 103 includes the upper electrode 92, the semiconductor layer 91, and the lower electrode 81.

  On the interlayer insulating film 82, the semiconductor layer 91, and the upper electrode 92, a coating type interlayer insulating film 93 is formed so as to have a part of the opening 97 </ b> A corresponding to the upper electrode 92 and cover each semiconductor layer 91. Yes.

  On the interlayer insulating film 93, the common electrode wiring 95 is formed of Al or Cu, or an alloy or laminated film mainly composed of Al or Cu. The common electrode wiring 95 has a contact pad 97 formed in the vicinity of the opening 97 </ b> A and is electrically connected to the upper electrode 92 through the opening 97 </ b> A of the interlayer insulating film 93.

The TFT glass substrate 90 formed in this way is formed with a protective film with an insulating material having a lower light absorption as required, and radiation conversion is performed using an adhesive resin with a lower light absorption on the surface. A scintillator 98 as a layer is attached. Alternatively, the scintillator 98 is formed by vacuum deposition. The scintillator 98 is preferably a scintillator that generates fluorescence having a relatively wide wavelength range so that light in a wavelength range that can be absorbed can be generated. Examples of such a scintillator 98 include CsI: Na, CaWO ₄ , YTaO ₄ : Nb, BaFX: Eu (X is Br or Cl), LaOBr: Tm, and GOS. Specifically, when imaging using X-rays as the radiation X, those containing cesium iodide (CsI) are preferable, and CsI: Tl (thallium is added) having an emission spectrum of 400 nm to 700 nm at the time of X-ray irradiation. It is particularly preferable to use cesium iodide) or CsI: Na. Note that the emission peak wavelength in the visible light region of CsI: Tl is 565 nm. In addition, when using the scintillator containing CsI as the scintillator 98, it is preferable to use what was formed as a strip-shaped columnar crystal structure by the vacuum evaporation method.

  As shown in FIG. 4, the radiation detector 26 is irradiated with radiation X from the side on which the semiconductor layer 91 is formed, and reads a radiation image by a TFT glass substrate 90 provided on the back side of the incident surface of the radiation X. In the case of a so-called back side reading method (PSS (Penetration Side Sampling) method), light is emitted more intensely on the upper surface side of the scintillator 98 provided on the semiconductor layer 91 in the figure. On the other hand, a so-called surface reading method (ISS (Irradiation Side Sampling) method) in which radiation X is irradiated from the TFT glass substrate 90 side and a radiation image is read by the TFT glass substrate 90 provided on the surface side of the radiation X incident surface. In this case, the radiation X transmitted through the TFT glass substrate 90 enters the scintillator 98, and the TFT glass substrate 90 side of the scintillator 98 emits light more strongly. Electric charges are generated in the sensor portion 103 of each pixel 100 provided on the TFT glass substrate 90 by light generated by the scintillator 98. For this reason, since the radiation detector 26 is closer to the light emission position of the scintillator 98 with respect to the TFT glass substrate 90 when the front side reading method is used than when the rear side reading method is used, the resolution of the radiographic image obtained by imaging is reduced. Is expensive.

  The radiation detector 26 is not limited to that shown in FIGS. 3 and 4 and can be variously modified. For example, in the case of the back side scanning method, since there is a low possibility that the radiation X will reach, in place of the above, other imaging elements such as a CMOS (Complementary Metal-Oxide Semiconductor) image sensor having low resistance to the radiation X You may combine with TFT. Further, it may be replaced with a CCD (Charge-Coupled Device) image sensor that transfers charges while shifting them with a shift pulse corresponding to the gate signal of the TFT.

  For example, a flexible substrate may be used. As the flexible substrate, it is preferable to apply a substrate using ultra-thin glass by a recently developed float method as a base material in order to improve the radiation transmittance. As for the ultra-thin glass that can be applied at this time, for example, “Asahi Glass Co., Ltd.,“ Successfully developed the world's thinnest 0.1 mm thick ultra-thin glass by the float method ”, [online], [2011 Aug. 20 search], Internet <URL: http://www.agc.com/news/2011/0516.pdf> ”.

  Next, the radiographic imaging device 14 in the electronic cassette 12 of this embodiment will be described. Hereinafter, as a specific example, a case in which the ISS type radiographic imaging device 14 is used will be described. 5A to 5C are explanatory diagrams for explaining the relationship between the radiation irradiation device 16 and the electronic cassette 12. FIG. 5A shows a state seen from the side, and FIG. 5B shows the radiographic imaging device 14 viewed from the radiation irradiation device 16 side. FIG. 5C shows a state in which the radiographic imaging device 14 has moved (moved) in FIG. 5B. In addition, description of the housing | casing 13 is abbreviate | omitted in FIG. 5A-FIG. 5C.

  As a specific example, the radiographic imaging device 14 of the present exemplary embodiment includes a scan signal control circuit 104 on one side of the radiation detector 26 on the long side of the imaging region, as shown in FIG. 5B. (The scan signal control circuit 104 is not shown in FIG. 5A). As shown in FIG. 5B, a signal detection circuit 105 is provided on one side of the radiation detector 26 that intersects the side where the scan signal control circuit 104 is provided. The signal detection circuit 105 is stacked on the radiation detector 26 as shown in FIG. 5A. When performing imaging, the electronic cassette 12 is arranged so that the side (imaging region) on which the radiation detector 26 of each radiographic imaging device 14 is provided faces the radiation irradiation device 16 (see FIG. 5A). .

  In addition, as a specific example, the radiation image capturing apparatus 14 of the present embodiment has a TFT glass substrate 90 larger than the scintillator 98 as shown in FIG. 5A. More specifically, the area facing the radiation irradiation device 16 is larger in the TFT glass substrate 90 than in the scintillator 98. In the present embodiment, the range (size) of the imaging region is determined according to the area of the scintillator 98 facing the radiation irradiation device 16.

  In the electronic cassette 12 of the present embodiment, due to the following reasons (1) to (3), etc., as shown in FIG. 5A, adjacent to the end (part) of the imaging region of the radiographic imaging device 14 The end of the radiographic image capturing apparatus 14 is arranged so as to overlap. Specifically, the imaging regions are overlapped so as to overlap with the incident direction of the radiation X.

(1) If there is an interval between the imaging regions of each radiographic imaging device 14, a portion that is not imaged may occur in the imaging region of the subject 18. In such a case, a defect occurs in the long radiation image (radiation image of the entire electronic cassette 12) obtained by connecting the radiation images captured by each of the radiation image capturing apparatuses 14 _{1 to} 14 ₃ .

  (2) When mass-producing the radiographic imaging device 14 (radiation detector 26), adjacent radiological detectors 26 are brought into close contact with each other due to manufacturing variations of the radiographic imaging device 14 (radiation detector 26). It becomes difficult to arrange without gaps.

  Furthermore, the radiographic imaging device 14 (radiation detector 26) may expand with temperature. In such a case, there is a concern that the TFT glass substrate 90 may be damaged if the adjacent radiation detectors 26 are in close contact with each other and arranged without a gap.

  (3) Further, when the temperatures of the radiographic imaging devices 14 are different, the expansion rate is different. Therefore, in the electronic cassette 12 of the present embodiment, the radiographic image capturing devices 14 are fixed to the housing 13, while the radiographic image capturing devices 14 are arranged without being fixed. Since they are not fixed to each other, the radiographic imaging device 14 (radiation detector 26) moves (moves, see FIG. 5C).

  Note that the range (size) of the overlapped overlapping imaging region depends on the oblique insertion of the radiation X emitted from the radiation irradiation device 16, the movement (movement, see FIG. 5C) of the radiation imaging device 14, and the like. You just have to decide.

As shown in FIG. 5A, in the radiographic imaging system 10 of the present exemplary embodiment, the position of the radiation irradiation device 16 can be moved in the direction along the longitudinal direction of the electronic cassette 12. Therefore, the position of the radiation irradiation device 16 differs depending on the imaging region of the subject 18 (see FIG. 1) to be imaged, the type of imaging, and the like, and the relative position of the electronic cassette 12 with respect to the long imaging region is displaced. . Therefore, according to the position of the radiation irradiation apparatus 16, in each radiographic imaging device 14, the angle of the incident radiation X differs. Specifically, in FIG. 5A, the overlapping portion of the radiation image capturing apparatus 14 ₁ and the radiographic imaging apparatus 14 _2, the radiation X emitted from the position B is incident so as to be substantially perpendicular to the imaging region, position The radiation X emitted from A is incident (obliquely entered) obliquely to the imaging region. Further, as shown in FIG. 5C, when the radiographic imaging device 14 moves (moves), the imaging region of the overlapping portion changes.

  In consideration of these various cases, the electronic cassette 12 according to the present embodiment determines the range of the imaging region of the overlapping portion with a margin so that the imaging regions do not overlap each other.

In the electronic cassette 12 of the present embodiment, as shown in FIG. 5A, as a specific example, the radiographic imaging devices 14 ₁ and 14 ₃ are on the upper side (on the upper side when viewed from the radiation irradiation device 16 side, on the radiation irradiation device 16). side close), radiographic imaging apparatus 14 ₂ is lower when viewed from below (radiation irradiation device 16 side, an end portion farther) and a so-called terrace-shaped radiation irradiation device 16 is superimposed.

  Note that, if the signal detection circuit 105 is provided between the radiographic imaging devices 14, the signal detection circuit 105 may be reflected in the radiographic image, as in this embodiment. It is preferable to superimpose so that the signal detection circuit 105 is not pinched.

Next, radiographic image capturing by the electronic cassette 12 will be described. In the electronic cassette 12 of the present embodiment, the radiation image is captured by the entire radiation image capturing device 14 by one irradiation (one shot) of the radiation X. FIG. 6 is an explanatory diagram for explaining a radiographic image captured by each radiographic image capturing device 14. 6 (1) shows a radiation image captured by the radiation imaging apparatus 14 _1. 6 (2) shows a radiation image captured by the radiation imaging apparatus 14 _2.

In the radiographic imaging device 14 (14 ₁ , 14 ₃ ) arranged on the upper side, the radiographic image taken is a radiographed using the single radiographic imaging device 14 as shown in FIG. It will be the same as the image.

On the other hand, the radiation image capturing apparatus 14 ₂ disposed on the lower side, as described above, the overlapping portion of the upper of the radiographic image capturing apparatus 14 (14 1, _{14 3),} a step is formed. Due to the step, as shown in FIG. 6 (2), the shadow of the overlapping portion of the upper radiographic imaging device 14 (14 ₁ , 14 ₃ ) is reflected in the captured radiographic image, and the step component Occurs. In the radiation image capturing apparatus 14 ₂ of the present embodiment, since the position of the end portion of the TFT glass substrate 90 and the scintillator 98 of the radiation detector 26 are different, a step component which is due to the step by TFT glass substrate 90, and scintillator 98 Two types of level difference components are generated, which are level difference components due to the level difference caused by Hereinafter, a component corresponding to an image of a region other than two types of step components in a radiographic image is referred to as a normal component.

  In the present embodiment, the step component resulting from the step due to the scintillator 98 is referred to as a scintillation step component, and the step component resulting from the step due to the TFT glass substrate 90 is referred to as a glass step component. Further, when the cinch step component and the glass step component are not distinguished, they are collectively referred to as a step component. Furthermore, an image representing the boundary between the cinch step component and the glass step component is referred to as a cinch step, and an image representing the boundary between the glass step component and the normal component is referred to as a glass step. Further, when the cinch step and the glass step are not distinguished, they are collectively referred to as a step.

Since the shadow of the upper radiographic imaging device 14 (14 ₁ , 14 ₃ ) is reflected, the density of the corresponding region (image) is different between the cinch step component, the glass step component, and the normal component.

FIG. 7 is an explanatory diagram for explaining changes in the positions of the cinch step component and the glass step component. Figure 7 shows an end region including the cinch stepped component and glass stepped component due to the end portion of the radiation image capturing apparatus 14 ₁ in the captured radiographic images by the radiographic imaging apparatus 14 _2. FIG. 7A shows a case where the angles of the radiation X incident on the imaging region are different. If the angle of the radiation X incident on the imaging region is different, the positions of the cinch step component and the glass step component differ depending on the incident angle, and the positions of the cinch step and the glass step are different. As shown in FIG. 7 (1), when the radiation X is irradiated from the position A (see FIG. 5A), the cinch step and the glass step, and when the radiation X is irradiated from the position B (see FIG. 5A). The position is different between the cinch step and the glass step.

  Further, FIG. 7B shows a case where the radiographic image capturing apparatus 14 has moved (moved) as shown in FIG. 5C. When the radiographic imaging device 14 moves (moves), the angle of the cinch step component and the glass step component varies according to the movement (movement), and the cinch step and the glass step are the cinch step and the glass step before the movement. Becomes nonparallel. As shown in FIG. 7 (2), the cinch step and glass step when taken in the state of FIG. 5B (before movement) and the cinch step and glass when taken in the state of FIG. 5C (after movement). The step is non-parallel.

Thus, in the radiographic image taken by the radiographic imaging apparatus 14 ₂ of the present embodiment, in accordance with the position of the radiation irradiating apparatus 16 and the radiographic imaging apparatus 14 of the motion (the incident angle of the radiation) (mobile), The position of the cinch step component and the glass step component changes. That is, the positional deviation of the cinch step component and the glass step component occurs.

In the radiation image captured by the radiation imaging apparatus 14 _2, according to the position of the irradiation apparatus 16 (incident angle of the radiation), the position of the cinch step and the glass step is substantially translated in the longitudinal direction. Further, in the radiographic image taken by the radiographic imaging apparatus 14 _2, the movement of the radiation image capturing apparatus 14 according to the (mobile), the angle of the cinch step and the glass step changes.

  Next, correction of a radiographic image captured by each radiographic image capturing device 14 of the electronic cassette 12 in the radiographic image capturing system 10 of the present embodiment will be described. Various corrections are performed on the radiographic image captured by the radiographic image capturing device 14 by image processing.

  In the radiographic image capturing system 10 according to the present embodiment, the radiographic images captured by the radiographic image capturing devices 14 of the electronic cassette 12 are output from the control unit 106 of each radiographic image capturing device 14 to the console 20. The console 20 functions as a functional unit such as a correction unit that performs image processing including various corrections and correction of the positional deviation of the step component on the radiographic image input from each radiographic imaging device 14. The function as the correction unit is not limited to the control unit 30 of the console 20, and may be included in other functional units of the console 20, or may be included in the electronic cassette 12 or the radiographic imaging device 14. . Further, the functional unit that performs the correction may be varied depending on the type of correction.

  The type of correction performed by the console 20 differs depending on the arrangement (upper side and lower side) of the radiation image capturing apparatus 14.

  In the console 20 of the present embodiment, the correspondence relationship between information such as an ID indicating the radiographic imaging device 14 and the arrangement (upper and lower) is stored in the storage unit 50 in advance. Further, the radiation image input to the console 20 is temporarily stored in the storage unit 50. The radiographic image capturing apparatus 14 outputs an ID indicating its own apparatus to the console 20 in association with the radiographic image. The console 20 can recognize whether the radiographic image is captured by the upper or lower radiographic imaging device 14 by referring to the correspondence relationship stored in the storage unit 50.

  Note that the method for recognizing whether the radiographic imaging device 14 that has captured the radiographic image is arranged on the upper side or the lower side is not limited to the present embodiment. For example, each radiographic imaging device 14 may add information indicating whether the radiography apparatus 14 is the upper side or the lower side to the radiographic image and output the information to the console 20.

When the console 20 of the present embodiment performs correction (step correction, details will be described later) on a radiographic image (hereinafter referred to as a captured image) obtained by imaging the subject 18 with the lower radiographic imaging device 14 (14 ₂ ). Reference is made to the corrected captured image of the upper radiation image capturing apparatus 14 (14 ₁ , 14 ₃ ). Therefore, first, correction is performed on the captured image captured by the upper radiographic image capturing device 14 (14 ₁ , 14 ₃ ).

The correction for the captured image captured by the upper radiation image capturing apparatus 14 (14 ₁ , 14 ₃ ) will be described. FIG. 8 is a flowchart showing an example of the flow of image processing for correcting a captured image captured by the upper radiation image capturing apparatus 14 (14 ₁ , 14 ₃ ). In the console 20 of the present embodiment, three types of corrections, offset correction, gain correction, and defect correction, are performed on the captured image captured by the upper radiation image capturing apparatus 14 (14 ₁ , 14 ₃ ).

In step S <b> 100, the control unit 30 of the console 20 acquires a captured image of the upper radiation image capturing apparatus 14 once stored from the storage unit 50. Specifically, the control unit 30 of the present embodiment acquires a captured image of either of the radiographic image capturing apparatuses 14 ₁ and 14 ₃ . Hereinafter, as a specific example of the captured image captured by the radiation image capturing apparatus 14, a captured image (radiation image) obtained by capturing the subject 18 with the radiation X irradiated from the position B (see FIG. 5A) will be described. To do.

In the next step S <b> 102, the control unit 30 acquires a gain calibration image (detailed later) from the storage unit 50 corresponding to the acquired captured images (radiation image capturing apparatuses 14 ₁ and 14 ₃ ).

  In the next step S104, the control unit 30 performs offset correction of the captured image. The offset correction is to correct a variation in an offset (zero point) taken in a state where the radiation X is not irradiated. The offset component includes a dark current included in each pixel 100 of the radiation detector 26 of the radiographic imaging device 14, an offset of an amplifier of an amplifier circuit built in the signal detection circuit 105, and the like, and changes according to temperature.

  In the next step S106, the control unit 30 ends the process after performing gain correction and defect correction of the captured image.

  Gain correction (gain calibration) is correction of variations in sensitivity of each pixel 100 over the entire imaging region of the radiation detector 26. In the gain correction, based on a radiographic image (hereinafter referred to as a gain calibrated image) captured by irradiating the imaging region with radiation X in a state where there is no shielding object in the imaging region or a reference subject exists. Correct the shot image. The gain component includes the intensity distribution of the radiation X emitted from the radiation irradiating device 16, variations in sensitivity of each pixel 100 of the radiation detector 26, variations in the gain of the amplifier of the amplifier circuit built in the signal detection circuit 105, and the like. is there.

  The console 20 according to the present embodiment acquires a gain calibration image of each radiographic image capturing apparatus 14 that is captured by irradiating the radiation X from the position A (see FIG. 5A) in a state where there is no shielding object in the capturing area. Then, it is stored in advance in the storage unit 50 in association with information such as an ID indicating the radiation image capturing apparatus 14. The control unit 30 performs gain correction of the captured image by correcting variation in sensitivity of each pixel 100 of the radiation detector 26 based on the gain calibration image stored in the storage unit 50.

The gain calibrated image and the captured image have different radiation X irradiation positions. However, in the upper radiation image capturing device 14 (14 ₁ , 14 ₃ ), no step component is generated, so that gain correction is appropriately performed. be able to.

  The defect correction is to correct the pixel value of the pixel 100 in which the defect has occurred. In defect correction, the pixel values of defective pixels are interpolated based on the pixel values of surrounding pixels.

  The captured image subjected to offset correction, gain correction, and defect correction in this way is stored in the storage unit 50.

Next, the control unit 30 of the console 20 corrects the captured image captured by the lower radiographic image capturing device 14 (14 ₂ ).

The correction for the captured image captured by the lower radiation image capturing apparatus 14 (14 ₂ ) will be described. FIG. 9 is a flowchart showing an example of the flow of image processing for correcting a captured image captured by the lower radiographic image capturing device 14 (14 ₂ ).

In the console 20 according to the present embodiment, four types of step correction are added to the captured image captured by the lower radiographic image capturing device 14 (14 ₂ ) in addition to the above-described offset correction, gain correction, and defect correction. Perform the correction.

In the following, to avoid the explanation to become complicated, the case of performing the step correction due to the radiation image capturing apparatus 14 _1. As a specific example, the position (radiation angle) of the radiation irradiation device 16 differs between when the gain calibrated image is captured (position A) and when the captured image is captured (position B), and is shown in FIG. 5C. A case where the radiographic imaging device 14 moves (moves) as described above will be described.

FIG. 10 is a schematic diagram for explaining an example of a flow of image processing for correcting a captured image captured by the lower radiographic image capturing device 14 (14 ₂ ).

  Note that the control unit 30 of the console 20 detects the positions of the cinch step component and the glass step component from the gain calibrated image before performing the image processing shown in FIG. The method for detecting the positions of the cinch step component and the glass step component from the gain calibrated image is not particularly limited.

  As a specific example of detecting the cinch step, the control unit 30 of the present embodiment detects the positions of the cinch step component and the glass step component with respect to the gain calibrated image after performing the process of removing noise. Yes. As a process for removing noise, for example, a main-direction median filter process is performed as a high-frequency removal process. The main direction is a direction intersecting with the sub direction of the electronic cassette 12. Further, the sub-direction is a direction in which the radiation irradiation device 16 moves, and in the present embodiment, is the longitudinal direction of the electronic cassette 12. In addition, for example, a moving average filter process may be applied, or another high frequency removal filter may be applied.

  As a method for detecting the positions of the cinch step component and the glass step component with respect to the gain calibrated image after the processing for removing noise, for example, by detecting a straight line (an image representing a straight line) from the gain calibrated image. The cinch step and the glass step are detected, and the positions of the cinch step component and the glass step component may be detected based on the detected cinch step and glass step. A straight line detection method is not particularly limited, and a general method may be used. For example, a Hough transform (Hough transform) or the like may be used.

In step S200 of the image processing, similarly to step S100 described above, the control unit 30 of the console 20 acquires a captured image of the lower radiation image capturing apparatus 14 that has been temporarily stored from the storage unit 50. Specifically, the control unit 30 of this embodiment obtains the photographed image of the radiographic imaging device 14 _2.

In the next step S202, as in step S102 described above, the control unit 30 acquires a gain calibrated image corresponding to the acquired captured image (radiation image capturing device 14 ₂ ) from the storage unit 50.

  In the console 20 of the present embodiment, offset correction and defect correction are performed before the step position is detected in order to easily detect the step position from the captured image. For this reason, in the next step S204, as in step S104 described above, the control unit 30 performs offset correction of the captured image.

  In the next step S206, gain correction and defect correction of the captured image are performed. In the gain correction in this step, the gain correction of the captured image that has been offset-corrected in step S204 is performed based on the gain calibrated image acquired in step S202 (the gain calibrated image in which nothing has been corrected).

  The method of gain correction and defect correction is not particularly limited. Since the acquired captured image and gain calibrated image include a step component, the QL value (pixel value) of the step component portion is lower than that of the normal component portion. Therefore, it is preferable to perform gain correction and defect correction in consideration of a decrease in the QL value of the step component portion.

  A specific example of gain correction performed by the control unit 30 of the present embodiment will be described, but the method of gain correction is not particularly limited. Since the gain correction corrects variations in sensitivity for each pixel, it is not preferable that the irradiation field is narrowed on the radiation detector 26. Further, it is not desirable that the SID (Source Image Distance) is too short and the radiation X is excessively attenuated due to the influence of the heel effect. Therefore, in the gain correction executed by the control unit 30 of the present embodiment, the pixel value is too large or too small to detect the irradiation field stop or to detect the attenuation of the radiation X due to an excessive heel effect. If it does, it is determined as an error. In the step component portion, the QL value is greatly reduced, and therefore error determination is performed in consideration of this. In the step component portion where the radiographic imaging devices 14 overlap, the pixel value greatly decreases. Therefore, the ratio of the pixel value between the overlapping region and the non-overlapping region is obtained as a set value in advance, and it is determined as an error. By multiplying the upper and lower thresholds by the ratio of the set value, it is possible to determine the abnormality of the pixel value by removing the influence of the radiation absorption of the overlapping region. After determining the abnormality of the pixel value in this manner, the gain correction of the captured image after the offset correction is performed based on the gain calibration image.

  As described above, the position (radiation angle) of the radiation irradiation device 16 at the time of imaging differs between the gain calibrated image and the captured image. Moreover, the radiographic imaging device 14 is moving (moved). Therefore, as described above, the position of the step component generated in the gain calibrated image is different from the position of the step component generated in the captured image. Since the position of the step component differs between the gain calibrated image and the photographed image, when the gain correction is performed, the step component of the gain calibrated image and the step component of the photographed image are generated in the corrected image. . Since the step component of the present embodiment includes a cinch step component and a glass step component, four steps are generated in the image after gain correction (see FIGS. 10 and 7 (2)).

  A specific example of defect correction performed by the control unit 30 according to the present embodiment will be described, but the defect correction method is not particularly limited. In the control unit 30 according to the present embodiment, after the offset correction is performed, the surrounding statistical processing is performed by processing using the median filter in the main direction and the sub direction, the moving average filter, the high frequency filter, and the like. Defect correction is performed by an algorithm for determining a threshold value of the difference between the photographed image and the photographed image before processing. A threshold value is compared for each pixel 100 to determine whether or not the pixel is a defective pixel based on the threshold value. The threshold value is obtained by taking a ratio between the pixel value obtained by applying the median filter and performing the surrounding statistical processing and the pixel value of the normal component, and multiplying the threshold value by the ratio is used as the threshold value of the overlapping portion.

  In the next step S208, the control unit 30 multiplies the captured image by a reciprocal coefficient. In the present embodiment, inverse gain correction is performed as a specific example of the reciprocal coefficient. As described above, there are four steps in the captured image that is to be subjected to inverse gain correction in this step.

  In the control unit 30 of the present embodiment, reverse gain correction is performed based on the gain calibration image for reverse gain correction acquired in advance. Note that the gain calibration image for reverse gain correction is obtained in advance as a gain calibration image obtained by removing noise such as high frequency noise by performing high frequency removal processing. The method for removing noise is not particularly limited. For example, a mask size median filtering process capable of removing point defects and line defects may be applied in the main direction and the sub direction, or moving average filtering process may be applied. Alternatively, other high frequency rejection filters may be applied.

Thereafter, in the control unit 30 according to the present embodiment, as a specific example, a step component (a step component caused by radiation X absorption by the scintillator 98 and a radiation X by the TFT glass substrate 90) is applied to the gain calibrated image from which noise is removed. Cut out the step component due to absorption). Actually, the position of the step component is not accurately known, but because the region where the step component is generated is obtained by design or experiment, by trimming the region including all the obtained regions, Trim the step component. In the Geinkyaribu image shown in FIG. 10 shows a step component caused by the radiation image capturing apparatus 14 _1, in fact, has also caused the stepped component by radiographic imaging apparatus 14 ₃ to Geinkyaribu image . Therefore, the control unit 30 cuts out both step components. That is, the control unit 30 trims the step component from both ends of the gain calibrated image.

  The control unit 30 adjusts the QL value so that the trimmed image between the two step components (corresponding to the normal component) and the two step components are smoothly connected to generate a gain calibration image for inverse gain correction. . The control unit 30 performs reverse gain correction by multiplying the gain-calibrated image for reverse gain correction acquired in advance by the captured image that has been subjected to defect correction in the process of step S206.

  The position of the step component of the gain calibrated image used for the reverse gain correction is different from the captured image, but is the same as that of the gain calibrated image used for the gain correction in step S206. Therefore, by performing inverse gain correction, the step component due to the gain calibrated image is removed, so that the four steps that have occurred in the captured image return to the two steps.

  Further, by performing reverse gain correction, the captured image becomes the same as the image before gain correction with respect to the gain of each pixel 100.

  In the next step S210, the positions of the cinch step component and the glass step component are detected from the captured image obtained in step S208. The detection method of the position of the cinch step component and the glass step component is not particularly limited. As a specific example, the control unit 30 of the present embodiment detects a straight line (an image representing a straight line) from a captured image, thereby detecting a cinch step and a glass step, and based on the detected cinch step and the glass step. The positions of the cinch step component and the glass step component are detected. A straight line detection method is not particularly limited, and a general method may be used. For example, a Hough transform (Hough transform) or the like may be used.

  In addition, when detecting a straight line from a captured image, a process for detecting a straight line may be performed on the entire captured image, but the positions of the cinch step and the glass step are estimated and the region including the estimated position is detected. It is preferable to perform a process of detecting a straight line. For example, a range in which the positions of the cinch step component and the glass step component can be obtained by design or experiment, and it may be estimated that the cinch step and the glass step are within the range. Further, for example, the positional deviation amounts of the cinch step component and the glass step component are obtained by design or experiment, and based on the cinch step and the glass step and the positional deviation amount detected in advance from the gain calibration image. It may be assumed that there are a cinch step and a glass step within the range. Thus, the detection accuracy can be improved by performing the process of detecting a straight line on the region including the estimated position as compared to the case of performing the process of detecting a straight line on the entire captured image.

  In addition, since the difference in the transmittance | permeability of the radiation X is small compared with a cinch level | step difference, the glass level | step difference has a small density | concentration difference between a glass level | step difference component and a normal component. Therefore, the cinch step component (cinch step) may be detected first, and then the position of the glass step component may be detected based on the detected position of the cinch step.

  In the next step S212, the position of the step component of the gain calibrated image is corrected to match the position of the step component of the captured image detected in step S210 by converting the coordinates of the gain calibrated image after defect correction. In this embodiment, the coordinates of the image are the coordinates (position) of the pixel, the y direction is the long direction (sub-direction) in which the radiation irradiation device 16 moves, and the x direction intersects the long direction. Direction (main direction). The coordinate conversion method is not limited, and examples thereof include a method of translating the step component of the gain calibrated image, a method of rotating, a method of deforming the shape of the step component, and the like. As a specific example of the method of deforming the shape of the step component, the step component of the gain calibrated image is transformed into a parallelogram in the sub direction according to the detected angular deviation between the step of the gain calibrated image and the step of the captured image. (See FIG. 10). When the shape is transformed into a parallelogram in this way, it is not necessary to consider the image information of the area protruding from the rectangle when applied to the rectangular gain calibrated image.

In the Geinkyaribu image shown in FIG. 10 shows a step component caused by the radiation image capturing apparatus 14 _1, in fact, it has also caused the stepped component by radiographic imaging device 14 _3. Therefore, the control unit 30 corrects the position of the step component by converting the coordinates of both step components of the gain calibrated image. When the step component is generated only at one end of the captured image, the coordinates of the entire captured image may be converted to correct the position of the step component.

  In order to generate a gain calibration image for gain correction, it is preferable to perform a process in which an image (corresponding to a normal component) between the two step components subjected to coordinate conversion and each step component are smoothly connected.

  In the next step S214, the control unit 30 performs gain correction of the captured image that has been subjected to the reverse gain correction in step S208, based on the gain calibrated image in which the position of the step component has been corrected by the processing in step S212.

  In the gain correction in this step, since the position of the step component of the gain calibrated image is aligned with the position of the step component of the captured image, there are no four steps as in the gain correction performed in step S206. Gain correction can be performed appropriately.

  Furthermore, the console 20 of the present embodiment corrects the step component generated in the captured image (step correction). In the present embodiment, the level difference correction refers to correction for reducing the density difference between the density of the level difference component and the density of the normal component. By performing offset correction, gain correction, and defective pixel correction in advance, the level difference can be corrected appropriately.

  Therefore, in the next step S216, first, the control unit 30 performs the step correction of the glass step component. A specific example of the step correction of the glass step component performed by the control unit 30 of the present embodiment will be described. Since the step is generally not horizontal (y coordinate is constant) but oblique, in the x range where the y coordinate is constant, for example, referring to the technique described in Japanese Patent Application Laid-Open No. 2009-285354, the step Make corrections. Since vertical stripes occur at the x-range boundary where the y-coordinate changes, the corrected image (calculated by smoothing the difference between pixel values of adjacent y-coordinates in the boundary in the main direction) is smoothed in the x-direction, Generation of streaks can be prevented.

  Note that the method of correcting the level difference of the glass level difference component is not limited to a specific example of the present embodiment, as long as the density difference between the density of the glass level difference component and the density of the normal component can be reduced. Good.

  In the next step S218, the control unit 30 performs the step correction of the cinch step component. A specific example of the step correction of the cinch step component performed by the control unit 30 of the present embodiment will be described. The control unit 30 of the present embodiment performs the step correction by dividing the cinch step component into two regions.

On the captured image, the upper radiographic image capturing device 14 (14 ₁ , 14 ₃ ) for the region (overlap region) where the image information is present in the captured image of the upper radiographic image capturing device 14 (14 ₁ , 14 _3). ) Image information. For this reason, in the present embodiment, correction for the captured image of the upper radiographic image capturing device 14 (14 ₁ , 14 ₃ ) is performed first. As the coordinates (address) of the area (overlap area) of the image information to be diverted, a set value or a value obtained by an experiment or the like is obtained in advance, and the storage unit 50 of the console 20, each radiographic image capturing device 14, What is necessary is just to memorize | store in the control part in the electronic cassette 12, a memory | storage part (illustration omitted), etc. FIG.

Further, as shown in FIG. 5A, the upper radiographic imaging device 14 (14 ₁ , 14 ₃ ) and the lower radiographic imaging device 14 (14 ₂ ) have different SIDs. It is preferable to match the magnification of the captured image with the lower captured image. As with the area of the image information to be diverted, the enlargement ratio is obtained in advance by setting values or values obtained by experiments or the like, and in the storage unit 50 of the console 20, in each radiographic imaging device 14, and in the electronic cassette 12. It may be stored in a control unit, a storage unit (not shown), or the like.

  For areas other than the overlap area, the correction amount is calculated so that the overlap area and the cinch step are smoothly connected, and the calculated correction amount is subtracted.

  In this way, when the step correction of the cinch step component generated in the captured image is completed, the control unit 30 ends the main image processing. The captured image after this processing (after level difference correction) is stored in the storage unit 50.

  Note that the portion that is the step component may be an image that is uncomfortable with the normal component portion. For example, the granularity of an image may be different between a portion that is a step component and a normal component portion. Therefore, it is preferable to perform various processes for further improving the image quality on the captured image after the main process.

  The control unit 30 displays the captured image of each radiographic image capturing device 14 corrected in this way on the display unit 34 of the console 20, outputs it to be displayed on an image interpretation device (not shown), or outputs it to the PACS 22. To do. Note that the control unit 30 may connect the captured images (after correction) by the radiation image capturing devices 14 and display or output the images as one radiation image, or may individually display or output the images. .

As described above, the electronic cassette 12 of the present embodiment includes the three radiographic image capturing devices 14 (14 _{1 to} 14 ₃ ). The radiographic imaging devices 14 ₁ and 14 ₃ are arranged in a so-called terrace shape in which the radiographic imaging device 14 ₂ is on the upper side (side closer to the radiation irradiation device 16) and the radiographic imaging device 14 ₂ is on the lower side (side far from the radiation irradiation device 16).

  The control unit 30 of the console 20 acquires a gain calibration image of each radiographic image capturing apparatus 14 captured by the radiation X emitted from the position A in advance and stores it in the storage unit 50. When imaging of the subject 18 is performed, the control unit 30 acquires a captured image from each radiographic image capturing device 14 and temporarily stores it in the storage unit 50.

Based on the gain calibration image stored in the storage unit 50, the control unit 30 performs gain correction of the captured image of the upper radiographic image capturing device 14 (14 ₁ , 14 ₃ ).

On the other hand, the captured image of the lower radiographic image capturing device 14 (14 ₂ ) is caused by a step at the end of the scintillator 98 and the TFT glass substrate 90 of the upper radiographic image capturing device 14 (14 ₁ , 14 ₃ ). Step components (cinch step components and glass step components) are generated. The control unit 30 detects the positions of the cinch step component and the glass step component from the captured image and the gain calibrated image. The control unit 30 corrects the positions of the cinch step component and the glass step component by converting the coordinates of the cinch step component and the glass step component of the gain calibrated image in accordance with the positions of the cinch step component and the glass step component of the photographed image. To do. The control unit 30 performs gain correction of the captured image based on the corrected gain calibration image.

  In the present embodiment, the positions of the cinch step component and the glass step component change in accordance with the position of the radiation irradiation device 16 (radiation incident angle) and the movement (movement) of the radiation image capturing device 14. Depending on the position of the radiation irradiation device 16 (radiation incident angle), the positions of the cinch step and the glass step move substantially in parallel in the longitudinal direction. Further, the angles of the cinch step and the glass step change according to the movement (movement) of the radiographic image capturing device 14. Therefore, the position of the cinch step component and the glass step component may differ between the gain calibrated image and the captured image. When gain correction of a captured image is performed using gain calibrated images having different step component positions, four steps occur in the captured image after gain correction due to the difference in the two step components.

  In contrast, the control unit 30 of the present embodiment corrects the positions of the cinch step component and the glass step component of the gain calibrated image according to the positions of the cinch step component and the glass step component of the captured image. Since the gain of the captured image is corrected based on the corrected gain calibration image, the gain of the captured image can be appropriately corrected. Furthermore, since the step component can be appropriately detected from the captured image, the step correction of the cinch step component and the glass step component can be appropriately performed.

  Therefore, in the radiographic image capturing system 10 (console 20) of the present embodiment, even when the incident direction of radiation changes between the gain calibrated image and the captured image, the step component generated in the captured image is corrected appropriately. Can be done.

  If the position of the cinch step component and the glass step component of the gain calibrated image detected in advance matches the position of the cinch step component and the glass step component of the captured image detected in step S210, the process proceeds to step S212. Processing may be omitted. As described above, when the positions of the cinch step component and the glass step component of the gain calibrated image and the photographed image match, even if the gain correction of the photographed image is performed based on the gain calibrated image, there are four steps as described above. There is nothing. Therefore, it is possible to appropriately correct the gain of the captured image based on the gain calibration image.

  Further, in the present embodiment, since the end of the scintillator 98 and the end of the TFT glass substrate 90 are different from each other, there has been described a case in which a step is generated due to each (two steps are generated). Is determined by the structure of the radiation detector 26 and the like, and is not limited to the present embodiment. It goes without saying that the present invention can be applied regardless of the number of steps.

  Further, the position of the radiation irradiation device 16 (irradiation position of the radiation X) is different depending on whether the correction image is captured or the captured image is captured, not only for the gain calibration image but also for other correction images. It goes without saying that the present invention is applicable to cases.

  In addition, the gain correction in step S206 and the reverse gain correction in step S208 may be omitted, and only defect correction may be performed. Note that by performing steps S206 and S208 as in the present embodiment, the positions of the cinch step component and the glass step component can be detected more appropriately in step S210.

  Further, in the present embodiment, as a method for correcting the positional deviation of the step component, the position of the step component of the gain calibrated image is adjusted to the position of the step component of the photographed image by converting the coordinates of the gain calibrated image. Although it corrects, the correction method is not limited. For example, instead of the gain calibration image, the coordinates of the captured image may be converted. Moreover, you may make it convert the coordinate of both a gain calib image and a picked-up image. When the coordinates of the photographed image are converted, the coordinates may be restored (inversely transformed) after the gain correction of the photographed image.

  Moreover, although this Embodiment demonstrated the case where the electronic cassette 12 was provided with the three radiographic imaging apparatuses 14, the number of the radiographic imaging apparatuses 14 is not specifically limited. Further, the method of overlaying the radiographic image capturing device 14 is not limited to the electronic cassette 12 (see FIG. 5) of the present embodiment.

Further, in the present embodiment has described the case where a plurality of radiographic image capturing apparatus 14 (14 1 _{to 14 3)} are provided in the housing 13 of the one electronic cassette 12 includes a plurality of electronic cassettes The present invention may be applied to a radiographic imaging system. For example, a plurality of electronic cassettes provided with one radiographic imaging device may be arranged adjacent to each other so as to have a long imaging region. A specific configuration example in the case of arranging a plurality of electronic cassettes adjacent to each other is shown in FIGS. 11 and 12 show a case where _three electronic cassettes 62 (62 _{1 to} 62 ₃ ) are arranged adjacent to each other. Moreover, FIG. 11 has shown the case where the electronic cassette 12 is arrange | positioned in the shape of a terrace like the radiographic imaging apparatus 14 of the electronic cassette 12 of this Embodiment. FIG. 12 shows a case where the electronic cassettes 12 are arranged in a staircase pattern.

  In each of the above embodiments, the case where the present invention is applied to the indirect conversion type radiation detector 26 that converts the converted light into electric charges has been described, but the present invention is not limited to this. For example, the present invention may be applied to a direct conversion type radiation detector using a material such as amorphous selenium that directly converts radiation into charges as a photoelectric conversion layer that absorbs radiation and converts it into charges.

  In addition, the configuration, operation, and the like of the radiographic image capturing system 10, the electronic cassette 12, the radiographic image capturing device 14, and the console 20 described in the present embodiment are examples, and the situation is within the scope of the present invention. It goes without saying that it can be changed according to the situation.

  Moreover, in this Embodiment, the radiation of this invention is not specifically limited, X-ray, a gamma ray, etc. can be applied.

10 the radiographic image capturing system 12, 62 the electronic cassette 14, 14 ₁ to 14 ₃ radiographic imaging apparatus 16 radiation irradiation device 18 subject 20 console 26 radiation detector 30 control unit 50 storage unit 90 TFT glass substrate 98 scintillator 100 pixels

Claims (9)

A first radiographic image capturing apparatus having a first imaging region for capturing a radiographic image corresponding to the radiation incident from the radiation irradiation device,
A second imaging region that captures a radiographic image corresponding to the radiation, wherein a part of the second imaging region is superimposed on a part of the first imaging region with respect to an incident direction of the radiation; a second radiographic image capturing device disposed farther from the radiation irradiating device than the first radiographic image capturing apparatus,
The incident direction of the radiation in the part of the first radiographic imaging device that is imaged by the second radiographic imaging device in accordance with the radiation incident on the second radiographic imaging region and overlapped with the first radiographic imaging device A correction image acquisition unit that acquires, as a correction image, a radiation image including a first step component generated due to a step with respect to
A radiographic image of a subject photographed at a timing different from the correction image by the first radiographic image capturing device is acquired as a first captured image, captured by the second radiographic image capturing device at the different timing, and the first radiographic image capturing device. Imaging that acquires a radiographic image of a subject including a second step component generated due to a step with respect to an incident direction of the radiation in the part of the first radiographing region superimposed on the first radiographic imaging device as a second radiographed image. An image acquisition unit;
The first step component is detected from the correction image, the second step component is detected from the second photographed image, and the position of the first step component matches the position of the second step component. As a correction to make a state, a correction unit for correcting a positional deviation between the first step component and the second step component,
A captured image correction unit that performs correction to suppress variation in gain of the second captured image, using the correction image in which the positional deviation is corrected by the correction unit;
A step correction unit that performs correction to reduce the step indicated by the second step component of the second captured image corrected by the captured image correction unit;
Radiographic imaging system equipped with. The correction unit corrects the positional deviation by converting at least one coordinate of the position of the first step component and the position of the second step component;
The radiographic imaging system according to claim 1. The correction unit corrects a positional shift by changing a shape of the first step component of the correction image to match a position of the first step component with a position of the second step component;
The radiographic imaging system according to claim 2. The correction unit detects the first step component and the second step component by detecting an image representing a straight line generated by a step from each of the correction image and the second captured image;
The radiographic imaging system of any one of Claims 1-3. A removal unit that performs high-frequency component removal processing to remove noise from the correction image;
The captured image correction unit corrects the second captured image using the correction image from which noise has been removed by the removing unit.
The radiographic imaging system of any one of Claims 1-4. The step correction unit performs correction to reduce a density difference between the density of the second step component and the density of a component in a region different from the second step component in the second captured image;
The radiographic imaging system of any one of Claims 1-5 . Comprising a first radiographic image capturing apparatus having a first imaging region for capturing a radiographic image corresponding to the radiation incident from the radiation irradiating device, a second imaging area capturing a radiographic image corresponding to the radiation, the first The two radiographing regions are arranged on a side farther from the radiation irradiating device than the first radiographic imaging device in a state where a part of the first radiographing region is overlapped with a part of the first radiographing region with respect to the incident direction of the radiation . An image processing apparatus that performs image processing of a radiographic image captured by a second radiographic image capturing apparatus,
The incident direction of the radiation in the part of the first radiographic imaging device that is imaged by the second radiographic imaging device in accordance with the radiation incident on the second radiographic imaging region and overlapped with the first radiographic imaging device A correction image acquisition unit that acquires, as a correction image, a radiation image including a first step component generated due to a step with respect to
A radiographic image of a subject photographed at a timing different from the correction image by the first radiographic image capturing device is acquired as a first captured image, captured by the second radiographic image capturing device at the different timing, and the first radiographic image capturing device. Imaging that acquires a radiographic image of a subject including a second step component generated due to a step with respect to an incident direction of the radiation in the part of the first radiographing region superimposed on the first radiographic imaging device as a second radiographed image. An image acquisition unit;
The first step component is detected from the correction image, the second step component is detected from the second photographed image, and the position of the first step component matches the position of the second step component. As a correction to make a state, a correction unit for correcting a positional deviation between the first step component and the second step component,
A captured image correction unit that performs correction to suppress variation in gain of the second captured image, using the correction image in which the positional deviation is corrected by the correction unit;
A step correction unit that performs correction to reduce the step indicated by the second step component of the second captured image corrected by the captured image correction unit;
An image processing apparatus. Comprising a first radiographic image capturing apparatus having a first imaging region for capturing a radiographic image corresponding to the radiation incident from the radiation irradiating device, a second imaging area capturing a radiographic image corresponding to the radiation, the first The two radiographing regions are arranged on a side farther from the radiation irradiating device than the first radiographic imaging device in a state where a part of the first radiographing region is overlapped with a part of the first radiographing region with respect to the incident direction of the radiation . a second radiographic image capturing apparatus, a control method of a radiographic image capturing system having a,
The correction image acquisition unit captures an image of the second radiographic image capturing device according to the radiation incident on the second radiographic region, and superimposes the first radiographic image capturing device on the first radiographic image capturing device. Acquiring a radiation image including a first step component generated due to a step with respect to the incident direction of the radiation in the unit as a correction image;
A radiographic image of a subject captured at a timing different from the correction image by the first radiographic imaging device is acquired as a first radiographic image by the radiographic imaging device, and the different timing is acquired by the second radiographic imaging device. A second radiographic image of the subject including a second step component generated due to a step with respect to the incident direction of the radiation in the part of the first radiographic imaging region overlapped with the first radiographic region. Acquiring as a captured image;
The correction unit detects the first step component from the correction image, detects the second step component from the second photographed image, and detects the position of the first step component and the position of the second step component. And correcting the positional deviation between the first step component and the second step component,
And performing by the captured image correcting unit, using the image for correction the positional deviation is corrected by the correction unit, the inhibit correcting variation in gain of the second captured image,
A step of correcting by the step correction unit to reduce a step indicated by the second step component of the second captured image corrected by the captured image correction unit;
A method for controlling a radiographic imaging system comprising: A radiographic imaging system control program for causing a computer to execute each step of the radiographic imaging system control method according to claim 8 .